The following specification describes the nature of the invention and the manner in which it is to be performed

Introduction

This invention relates to layered catalyst carriers that are used in chemical, petrochemical, petroleum refining, hydrocarbon processing and other processing industries and more particularly to layered-catalyst carriers having catalyst support coating(s) provided on particulate cores of spherical or other configuration. This invention provides a process/method for laying thin and uniform catalyst carrier (layers)coatings on inert core supports. This invention also relates to a synergistic mixture of two catalyst carrier materials, the first being a wide pore carrier material and the second being a said carrier material that inter alia synergistically provides better adherability to the mixture. Still further, this invention relates to layered catalysts for dehydrogenation of hydrocarbons and other processes in the industry sectors mentioned hereinabove.

Background of the invention

The three major members of a layered catalyst architecture are: a. the inert core support;

b. the carrier; and

c. the catalyst element.

An inert core support is the basic mechanical support (substrate) whereupon the catalyst architecture is built up, an example whereof are said spheres (spherical elements) referred to hereinabove. Said carrier and catalyst element are laid on said spherical elements.

A carrier is the element of said catalyst architecture that primarily provides the large internal and external surface area for the dispersal of the catalyst element thereupon. Said carrier is installed on a said core support(s) in the form of a coating(s)(layers). One or more said catalyst elements, as required, are either dispersed onto said carrier or impregnated there into.

The catalyst element is the component (member) that provides the catalytic action. It may be any of the metals or compounds that provide catalytic action. Examples of such metals are the group of precious metals (PGMs) which includes platinum(Pt), rhodium(Rh), palladium(Pd) and others.

A layered catalyst carrier(LCC for short) comprises a said inert core support and a said carrier, with the latter laid on the former, as mentioned, in the form of a layer. Where said cores are in the form of spherical elements the carriers are formed into coatings(shells) around the spherical surfaces thereof.

The term 'inert core support is shortened to either 'core' or 'inert support' in the further specification herein below. Within the scope of the invention said cores may be spherical in shape or may be in other forms and shapes, regular or irregular, for example, pellets and tubular structures. They may be prepared by any of the known processes of agglomeration, such as for example, granulation, pelletisation and others. The cores of the invention may also be in the form of extrudates.

Several Refractory Inorganic Oxides(RIOs for short) are used as materials of construction for said cores and are within the scope of the invention including mixtures thereof Cores of metallic construction are also within the scope of the invention. Both hollow and solid spherical cores(spherical elements) are within the scope of the invention.

Examples of RIOs that may be used to form said cores, without limitation to the scope of the invention, are alpha alumina, silica, zirconia, titania, cordierite, indialite and others. These may be used singly or as mixtures. Said cores may be also of non-oxide inorganic materials such as, for example, silicon carbide The preferred materials of construction for the cores of this invention are the RIOs: cordierite and indialite. More preferably, said material of construction is indialite.

The material of construction of said carriers are also RIOs or mixtures thereof and any of them can be adopted as the carrier material within the scope of the invention. Examples of said carrier RIOs, without limitation to the scope of the invention are: the various aluminas including transitional alumina, rare earth oxides, silica, clay minerals, and other metallic and non-metallic oxides. Non-RIO materials such as zeolites are also used. The preferred materials for this invention are discussed herein below.

The RIO material for the formation of said core elements may further comprise one or more suitable additives for control and modification of the physical and chemical properties thereof such as porosity, thermal conductivity, bulk density, impact strength and others. The RIO material for use as the carrier material may further comprise one or more suitable additives that promote catalysis, or are modifiers or structure stabililisers or others.

In some places in this specification, for convenience, the terms outer and inner RIOs are used to refer to the RIO materials of construction adopted for the said carrier and core respectively. The terms first and second aluminas refer to the two aluminas forming the coating material mixture as elaborated further hereinbelow. For the purposes of this specification, the term RIO as used in reference to said cores or said carriers is intended to include all suitable materials, refractory inorganic oxides, non-oxide inorganic materials, metallic, non-metallic oxides and other compounds.

Said catalyst elements may be any of the metallic or non-metallic elements and compounds that possess catalytic activity. Examples are the PGMs. Non precious(base) metals and also some oxides and other compounds that possess the required catalytic properties for the reaction being considered can also be simply and easily installed on the LCCs of the invention. Any said catalyst element(s) may be easily and simply dispersed/impregnated on the layered carriers of the invention by means of known processes in the art.

By installing(dispersing/impregnating) the appropriate catalyst element(s) on the layered catalyst carrier of the invention, a wide range of catalyst assemblies can be obtained that have different applications in chemical, petroleum refining, petrochemicals, hydrocarbon processing, polymers and other industries.

By way of example, such applications are hydrogenation, dehydrogenation, isomerisation, cracking, hydrocracking, oxidation and other operations/processes in these industry sectors. Thus, the LCCs of the invention are easily and simply adapted to produce catalyst assemblies for numerous process applications by simply dispersing/impregnating the appropriate powdered catalytic material thereupon.

Within the scope of the invention, the layered carriers of the invention may be loaded with one or more of the said catalyst elements or otherwise. Further, within the scope of the invention the loading of the catalyst elements on the carriers of the invention may be carried out before the laying of said carriers on the cores or thereafter. Catalyst elements may be installed individually or as mixtures. As mentioned, different processes are known in the art for said dispersal/ impregnation of the catalyst element onto the carrier.

Several other terms such as 'layered catalyst compositions', 'coated substrate', 'coated carriers', 'layered catalysts' are used in the art to refer to said layered catalyst carriers which, are the subject of this invention. Cores are also referred to in the art as substrates and said catalyst elements are referred to alternatively as active elements or just as catalysts. Said carriers are also referred to in some parts herein as support coatings or supports. The said terms may therefore be considered to be synonymous.

The completed catalyst architecture comprising the support and the catalyst element and including said carrier is referred to as the 'catalyst assembly' herein. Said assembly may additionally contain one or more further components that provide secondary and/or complementary catalyst activity such as promoters and modifiers. Such additives, may also be, for functions such as carrier structure stabilisation, oxygen storage and others as mentioned above.

In the further specification herein below, the layered carrier product according to the different aspects of the invention and the process for making the layered carrier product of the invention are described only in the context of cores that are in the form of a plurality of discrete spherical elements such as are widely used in petroleum refining, petrochemical and hydrocarbon sectors. This is in the interests of conciseness and without limitation to the scope of the invention.

It will be observed that the process of the invention is simply and easily adapted to making other types of layered carriers referred to hereinabove, that is, of types other than said particulate spherical entities. Because of that, with reference to terms such as, for example, layers, surfaces, coatings, cores, catalyst elements and others, sometimes the singular may be relevant to the context and sometimes the plural. In some cases, both the singular and plural may be relevant. The interpretation that confers the widest scope to the text may be considered to be applicable and may be adopted.

Various slurry-based processes are used in the art for the application of said carriers on said spherical elements. In these processes, the carrier material in appropriate particle size(s) is slurried in a suitable liquid, which is generally water. The spherical elements are contacted with the slurry and thereafter subjected to a process of calcination that bonds the carrier to the core.

The calcination process is regulated such as to obtain the right degree of porosity and other properties of the carrier layer(coating). Said contacting is by immersion, by spraying, by the incipient wetness method or other methods. Optionally, binders are used during said contacting. The term slurry-based processes as used herein includes processes wherein the carrier material is employed in the form of colloidal solutions (cols), sols and other types of dispersions.

One problem posed in the prior art is that of diffusional limitation (DL). The term refers to the reduced accessibility of some catalyst sites to the reaction molecules because of the high diffusional resistance involved in accessing them. These are mainly the catalyst sites located deeper in the pore interiors. The reactant molecules that access the said interior sites tend to remain in longer contact with the catalyst, which tends to encourage unwanted side reactions and risks deactivation of the catalyst.

DL also arises where there is considerable variation in diffusion resistances across the surfaces of said layers. DL leads to the underutilisation of the catalyst mass and loss of selectivity thereof

The crux of the problem is the variations in the thickness of said carrier layer across the surfaces thereof and the variations in the mean pore diameters and other pore parameters across the carrier surfaces. Diffusion resistance is greater the greater the said thickness and the non-uniformity thereof arises from the said variations in layer thickness and in pore characteristics.

Said underutilisation and loss of selectivity reduces the conversion rate and conversion per pass which translates into increased capital and operational costs.

Said deep interior sites also arise by migration of catalyst elements from sites located closer to the pore mouths into the pore interiors. Depending on the porosity of the core(sphere) material such migration may extend into the core material also. Said migration occurs over time during the life of the catalyst and also leads to said underutilisation.

This invention observes that, in view of the above, it is important that:

i. said layers are thin;

ii. said layers are uniform, that is, the layer thickness is substantially uniform across the layer surfaces;

iii. the pore configurations such as the, shape, surface characteristics and the mean diameters thereof are such that the said diffusion resistance is minimised and that it is substantially uniform across said surfaces; and

iv. the penetration of catalyst element(s) into, and/or the said migration thereof into the core across the layer-core interface during catalyst preparation and operation is minimised.

Ensuring that said layers are thin and uniform can bring down said diffusional resistance and also equalise it to a certain extent across the surfaces. This will bring down said underutilisation but in the absence of harmonisation of the pore configurations some of the gains made in reducing said under-utilisation by thin and uniform layers can be lost. Achieving thin and uniform layers is therefore only a part-solution.

If the pore parameters are not substantially equalised/harmonised over the said surfaces said underutilisation will persist and will defeat the cost and effort involved in producing thin and uniform layers. Providing thin layers(shells) ensures that the catalyst sites are close to the layer surfaces and consequently the diffusion paths are short and the diffusion resistances low.

The desirability of said thin layers of uniform thickness, better controllability of the said coating process, larger pore dia., and preventing penetration of the carrier material into the core material is mentioned in US 5 935 889 by Murrell LL et al. In US '889, the spherical core elements are fluidised in an air stream and an atomised spray of the carrier material slurry(or sol) is directed on the said core particles(elements). Uniform layers of low thickness are stated to be possible by the procedure disclosed but the degree of uniformity obtainable is not reported. Layer thicknesses as low as 70 micrometres are stated to be possible.

The lowered accessibility of the said interior sites and the consequent wastage of catalyst resources is mentioned by Fisher HC in US 3 145 183. WO 2006/127136 by Rende D et al primarily deals with the problem of insufficient attrition resistance and provides for fibrous reinforcement of the layers. Rende et al, however, report that by using a fluidisation process of layer deposition, layer thicknesses down to 40 microns are possible although the degree of layer thickness uniformity achievable is not disclosed.

While the prior art has posed some of the problems and drawbacks, it has not disclosed any potential or actual solution thereof particularly along the holistic lines as provided by this invention.

This invention, therefore, observes that it is important to tackle both issues simultaneously in a holistic and co-ordinated manner. This is novel. This invention considers that the process for laying down said layers must be so devised that it yields reliably thin and uniform carrier layers and must be coupled with suitable pore engineering steps. The latter must be devised such that said pore parameters are harmonised across said surfaces. Preferably, said pore engineering procedures devised must also take care of the problem of said migration of catalyst sites across the layer-core interface into the said cores. Pore parameter harmonisation herein refers to the process of reducing/minimising the variations in pore parameters across the surfaces of said layers.

Pore engineering in the prior art has comprised treatment (such as calcination) of the carrier material such as to alter the surface area(BET area). Pore engineering in the prior art has not extended to proposing or adoption of wide pore carrier materials.

This invention finds that adoption of wide pore carrier material(s) yields a more harmonised layer and improved catalyst efficiency and performance particularly with regard to selectivity. This is novel and has apparently not been disclosed in the prior art.

While it is known that thermal treatment of the carrier material before or after layer installation can yield wide pore characteristics, prior art has not proceeded to incorporate such treatments. Perhaps this is because of the poor adhesion properties of wide pore materials.

Prior art also appears to be unaware of the said harmonisation, equalisation, diffusion resistance reduction and other advantages that come from the adoption of said wide pore materials.

Wide pore carrier materials have poor adherability(adhesion) to the cores and bring down the adhesion of the carrier mass as a whole. Poor adherability can lead to unravelling of the catalyst layers during operation and loss of catalyst working life.

This invention is apparently the first to be able to overcome this problem by blending the wide pore material with other carrier materials. Thus, the carrier material mixture of the invention comprises at least one carrier material component that, with or without a thermal treatment thereof, primarily imparts said wide pore characteristic to the layer. A second component synergistically provides better adherablility to the mixture as a whole. There are other synergistic advantages that are elaborated further herein.

Functionally, said second component is also a carrier material that can provide support for the catalyst element(s). It may have other functions within the scope of the invention. Also, within the scope of the invention, said mixture may comprise other carrier material components, third, fourth and others that additionally provide carrier(support) function and one or more of the other functions listed herein.

The novel process of the invention for installing said layers is a dry spray process and the novel mixture of the invention comprises a mixture of a carrier material component having a wide pore characteristic and a carrier material component that synergistically interacts with the first(and or with one or more of the others) to correct the low adherability associated with wide pore carrier materials and restores it to workable levels. Said process and mixture are not apparently disclosed in the prior art.

The magnitude of said diffusional resistance(DR) and the said uniformity thereof is of particular relevance in petroleum refining, petrochemical and hydrocarbon processing operations wherein said resistances are high because of the large and long reactant molecules involved. The adverse impact of said non-uniformity can be high in such processes.

It is the principal object of this invention, therefore, to provide a process of making said layered carriers and a catalyst material mixture that tackle the problems outlined hereinabove in a holistic and co-ordinated manner by influencing said layer formation and pore formation such as to achieve to the maximum extent, as many as possible of the said objectives (i) to (iv) stated hereinabove.

A further object of the invention is to devise a said process that offers a high degree of controllability of the layer forming operation so as to achieve highly uniform layers of any thickness. The process of the invention is therefore capable of laying uniform layers of any thickness. The process is particularly suitable for laying highly uniform layers of thicknesses 300 microns(micrometres) and below, a range that is not within the capability of conventional slurry-based processes.

A still further object of the invention is to substantially equalise and harmonise the said pore parameters such that the said diffusional resistances are low and substantially uniform across the said layer surfaces. Other objects of the invention will be evident from the description of the invention and the claims herein.

Said desirable features ensure that said diffusion resistances remain low and are substantially equalised over substantially the whole of said carrier layer surfaces. The other purpose is to ensure that diffusion of the catalyst element and the carrier material across the layer-core boundaries during operation is prevented/minimised.

Attempts have been made in the past to develop said thin layers using the prior art slurry-based processes for carrier deposition on the cores. This invention observes that said slurry-based processes of layer formation are poorly adapted for generating layers that are thin and that are reliably uniform in thickness.

Attempts in pore engineering in the prior art have been confined to calcination procedures that alter the surface area in the pore interiors available for catalyst element deposition. Devising pore engineering steps and calcination procedures such as to obtain said pore parameter equalisation/harmonisation has neither been attempted nor disclosed in the prior art.

This invention is therefore apparently the first to develop a said dry spray process of carrier deposition that provides a high degree of controllability of the coating laying process. The process offers precision in layer formation and reliability as regards the uniformity of thickness across the layer surfaces. It is also apparently the first process that can provide precise layer thicknesses in the range 300 microns and below.

This invention is also apparently the first in achieving said pore parameter equalisation/ harmonisation objective by adoption of novel pore engineering steps such as provision of a novel carrier material mixture that preferably comprises two aluminas each obtained by a different process of formation and a novel heat treatment procedure for the same.

This invention provides a novel dry spray process wherein the carrier material, with or without the catalyst impregnated therein, is deposited by spraying the powdered carrier material on the spherical elements, in a dry condition. In other words, the deposition is by a dry spraying operation utilising a gas as the dispersing medium.

A binder liquid(or binder solution) is applied on the inert cores to promote bonding of the carrier material on the core surfaces. The quantity of binder solution applied is carefully controlled so as to ensure that at no time any free binder liquid is present in the core material. Ensuring absence of free liquid in and around the core material during the dry spraying of the carrier material leads to improved uniformity in layer thickness. Free binder liquid if present tends to disturb the carrier material layer(s) and cause variations in the thicknesses thereof

Application of the binder is preferably by spraying. Preferably, a separate spraying system for the binder solution is provided on the pan coater or other coating equipment that may be used. Preferably, the binder is applied before each spraying of the dry carrier material powder. Simultaneous spraying of the dry carrier material and the binder solution is within the scope of the invention.

Higher level of said layer thickness uniformity is possible through the dry coating process of the invention than possible by the conventional slurry-based coating processes. Reliable layer thicknesses of about 300 microns and below are possible with the process of the invention unlike in the prior art processes. This is novel. The process of the invention offers several other advantages that are elaborated herein below.

This invention further provides a novel carrier material composition that minimises said diffusion resistances and offers said equalisation/harmonisation of the pore configurations and parameters. The invention also offers a process of admixture for making said novel synergistic carrier material mixture (composition).

Said novel carrier material mixture of the invention comprises a mixture of a wide pore carrier material with at least one other component. The provision of said second component synergistically enhances the adhesivity of the mixture and takes care of the adhesion deficit arising from the adoption of said wide pore carrier materials.

The use of the wide pore material results in larger dia. pores, the diffusional resistances whereof are more equalised/harmonised. The use of said mixture is found by this invention to result in more uniformity in pore diameters.

It is observed again that the term 'RIO' is intended to include all materials, whether refractory inorganic oxide or otherwise, that are suitable for the respective application, that is, for the core or for the carrier. Examples of such materials are provided hereinabove.

Thus, the characteristics of the layer formed by such a mixture are: (i) larger dia pores, (ii) a greater degree of equalisation in pore diameters across the layer surface, and (iii) a greater degree of equalisation/harmonisation of the diffusion resistances and other pore parameters..

This combination of properties is not obtainable by adoption of single carrier materials. This invention observes that the mixture offers an unexpected synergy in respect of pore properties. Said synergy is in respect of adherability(adhesiveness) and pore harmonisation. The invention also additionally provides a process for treatment of said mixture that provides a greater degree of pore parameter equalisation/harmonisation. Said additional procedure of the invention may be optionally adopted and applied to the said carrier material mixture of the invention.

The potential applications of the processes and products of the invention are in catalysts for dehydrogenation, isomerisation, hydrogenation, cracking, hydrocracking, oxidation and others.

Brief description of the invention

According to the invention, therefore, there is provided a process for making layered catalyst carrier(s) such as for applications in petroleum refining, petrochemicals and hydrocarbon processing and other sectors, comprising particulate core material having one or more layers(coatings) of catalyst carriers provided on the surfaces thereof, said process comprising the steps of:

(i) providing said particulate core material, and said carrier(s) material in powder form;

(ii) applying a binder material on said particulate core material;

(iii) depositing said carrier powder on said core particle surfaces in one or more operations to obtain one or more deposits of said powder laid thereupon; characterised in said deposition being carried out by dry spraying of said powder onto the base material in one or more operations by means of a gaseous propellant;

(iv) repeating the depositing operation till the generation of the required layer thickness(es) and the required number of said layer(s); and

(v) fixing said deposits and/or layer(s) onto the said base material or surfaces; the said carrier material being deposited comprising catalyst element(s) dispersed/impregnated thereupon or otherwise, and said base material being agitated during the course of said spraying.

According to a second aspect of the invention, there is provided a layered catalyst carrier(s) such as for applications in petroleum refining, petrochemicals and hydrocarbon processing and other sectors, made by the process of the invention disclosed hereinabove as the first aspect of the invention.

According to a third aspect of the invention, there is provided a carrier material for application as catalyst-carrier layers(coatings) on the surfaces of inert core supports of layered catalyst carriers such as for applications in petroleum refining, petrochemicals and hydrocarbon processing and other sectors, comprising a mixture of at least a first, and a second carrier material component, said first component being a wide pore carrier material and the said second carrier material, being either peptisable or being in a col or sol form, or a mixture thereof

According to a fourth aspect of the invention, there is provided a layered catalyst carrier(s) such as for applications in petroleum refining, petrochemicals and hydrocarbon processing and other sectors, comprising particulate core material having one or more layers(coatings) of catalyst carriers provided on the surfaces thereof, wherein the carrier material of at least one layer thereof comprises a mixture of first and second carrier material components, as disclosed hereinabove as the third aspect of the invention.

According to a fifth aspect of the invention, there is provided a layered catalyst carrier(s) such as for applications in petroleum refining, petrochemicals and hydrocarbon processing and other sectors, comprising particulate core material having one or more layers(coatings) of catalyst carriers provided on the surfaces thereof, at least one said layer thereof having a thickness not exceeding 300 microns.

Detailed description of the invention.

Some details of the products and process of the invention and the scope of the invention are disclosed and defined in the other sections hereinabove. Said disclosures may be considered adopted in this section also. The remarks given herein on the features and scope of the inventions are in respect of all the aspects thereof unless otherwise required by the context.

In the process and products according to the first and other aspects of the invention disclosed hereinabove, the said particulate core material may be any RIO or other material. Said material may be oxide, non-oxide, metallic or non-metallic or others.

Examples of some suitable core materials have been given hereinabove. Preferably, the core material is either cordierite or indialite and more preferably the latter.
In the embodiments/examples described in detail hereinbelow the inert core material is indialite. The invention can be easily and simply adapted for use with other core materials including, and particularly cordierite.

Said core particles may be spherical or of any other shape. Said shapes may be regular or irregular and may be hollow or otherwise. Within the scope of the invention, they may be fabricated by any known process including by any of the known agglomeration processes such as for example, granulation, pelletisation and others.

Said particulate core material may also be an extrudate having any of the many possible cross-sections. Said core material may also be any mixture of the abovementioned variants within the scope of the invention. Said core particle surfaces may be plain or of any other configuration within the scope of the invention. Shapes such as those used in absorption tower packings are also within the scope of the invention.

Preferably the said core particles are spherical in shape and possess generally plain surfaces.

Preferably said core particles are small in diameter(or effective diameter) not exceeding about 5 mm. As their surface areas are correspondingly small, it helps in minimising said catalyst site migration into the core material. Accordingly, the core spheres in the embodiments described hereinbelow are small. The said core spherical elements are calcined at a temperature of about 500 C to about 1400 C before taking up dry spraying of the carrier material thereupon.

This invention observes that indialite is particularly adapted for small core diameters as low as 5 mm and below and for installing thin layers of 300 microns and below thereupon. Indialite is a high temperature form of cordierite and has a different structure as established by x-ray crystollagraphic analysis. It has greater thermal stability in contrast to cordierite. The distortion index of indialite is also lower than that of cordierite.

As would be noted from the experimental measurements given hereinbelow, the LCC of the invention incorporating indialite cores has excellent IB, abrasion resistance, CBD, CS and other properties. Said properties are controllable by varying the component ratio in the carrier material mixture of the invention.
Said carrier material may also be any material: a RIO or a non-RIO. It may be any of the oxides of the rare earth metals, alkali earth metals, transition metals or metals of the lanthanide series, or any mixture thereof within the scope of the invention.

Said carrier material may further comprise admixed therein one or more compounds with functional properties such as stabilisation of the carrier structure, catalysis promotion/modification, oxygen storage and others within the scope of the invention.

Said carrier material for the formation of said layers may be with or without catalyst element(s) dispersed/impregnated thereupon. Carrier material containing the catalyst element(s) is referred to herein as loaded carrier material or loaded carrier for short. Said loading may comprise one catalyst element or a plurality thereof.

Thus, a said layer of the layered catalyst carrier of the invention may comprise one catalyst element or more. The layered catalyst carrier may comprise a plurality of said layers and the said different layers thereof may be loaded with different catalyst elements(or mixtures thereof) within the scope of the invention.

The said carrier material mixture of the invention is a mixture of at least two carrier material components. In the broadest aspect of this novel feature of the invention, said first component can be any wide pore carrier material. The said wide pore characteristic may be inherent in said first component material or may be developed by suitable heat treatment thereof. In some cases, the wide pore characteristic may be partly of an inherent nature and partly developed by the treatment procedure adopted.

The range of carrier materials has been discussed hereinabove. Any of these carrier materials that have the said wide-pore property or that can be heat treated to acquire the wide-pore characteristic can be adopted as the first component of the carrier material mixture of the invention.

Within the scope of the invention, the material of said first component may be any carrier material, the only requirement being that they are in the wide-pore form or are convertible to the wide-pore form by the heat treatment procedure described herein.

Typical carrier materials that possess, or that can be modified by thermal treatment to achieve said wide-pore characteristic are the various aluminas, the rare earth oxides and others. These materials are simply and easily converted into the wide-pore form by the said heat treatment procedure. Said first component is preferably one of the aluminas, or ceria or zirconia. More preferably the material of construction of said first component is an alumina obtained by a process of precipitation from a suitable solution thereof. Still more preferably the first component is either precipitated delta or theta alumina, or mixtures thereof

Within the scope of the invention, the second component of the carrier material mixture can be any of the carrier materials enumerated hereinabove that are peptisable. Preferably said second component is also an alumina but derived by the alkoxide route. More preferably, said second component alumina is either delta alumina or theta alumina or a mixture thereof.

Said second component can thus be any peptisable carrier material in the broadest aspect of the invention. It can alternatively be a col or sol of any one of the several suitable RIOs or other material that are listed hereinabove.

In the preferred embodiment, said delta or theta alumina or a mixture thereof for the said first component is derived by precipitation from a suitable solution thereof by physical or chemical means and the second obtained through the alkoxide route. Use of mixtures of said carrier materials for the said first and second components is within the scope of the invention. Said carrier material mixture of the invention may comprise additionally third, fourth and higher order components within the scope of the invention.

Alternatively, the said second component may be a col/sol of said aluminas or of mixtures thereof or of ceria, zirconia, silica or other metal oxides within the scope of the invention. Mixtures of the abovecited materials are within the scope of the invention.

The alumina obtained by the precipitation route is referred to fiarther herein as Compound A and the other alumina derived through the alkoxide route as Compound B. Compounds A and B have been adopted in the examples described herein below.

Preferably, the mixture of compounds A and B is subjected to a novel calcination procedure developed of the invention before spraying onto the core by means of the said dry process. Adoption of said novel procedure increases the degree of said harmonisation. The novel process of calcination and treatment of said mixture when applied prior to taking up said dry spraying yields better pore characteristics.

All compositions of the said two alumina components, (Compounds A and B) in the carrier material mixture of the invention are within the scope of the invention. Preferably, the ratio of the two said alumina components(Compound A to Compound B) is upto about 10:1 by wt. The more preferred value of the said ratio of compound A to compound B is from about 2:1 by wt. to about 2.5:1 by wt.

The alumina carrier material may be modified by the addition of stabilisers, promoters, and others as required by the specific process intended to be catalysed, within the scope of the invention. The aluminas may be any of the following: gamma, delta, theta and eta or transitional alumina.

The novel observation made by this invention based on experimental investigation is that if the said carrier material comprises a mixture of said two aluminas derived by the routes and process steps disclosed, the said pore parameters are substantially harmonised/equalised over the surfaces of the layers. This results in considerably greater and more uniform utilisation of the catalyst sites across the said surfaces in operation.

This invention has discovered through experimental work the surprising synergy exhibited by a mixture of a wide pore carrier material and a peptisable carrier material. Similar synergy is also observed in a mixture of the former with a carrier material in a col/sol form. At different compositions of the said mixture different mean pore diameters of the formed layers are found.

Accordingly, indicators of catalyst performance change with the composition of the carrier material mixture and exhibit a maximum corresponding to a maximum in said synergy.

Another synergy observed is that the drawback of poor adhesion associated with a said wide pore carrier material and the proclivity towards narrower pores of the said second carrier material both get advantageously modified in the mixture to yield layers, that comprise reliably wide pores throughout and further have good adhesion characteristics. The catalytic performance thereof is better than that of the individual carrier materials when used alone.

A general mechanism has been suggested herein of how the advantageous features and performance of the LCC of the invention arise. This is without commitment. It may be noted that said advantageous features, performance and synergy are established by the tests and experiments carried out by the invention and are not dependent on the correctness or otherwise of the suggested mechanism.

Additionally, if thin and uniform carrier layers are provided as by the process of the invention further benefit in the form of lowered diffusion resistance and further equalisation thereof is realised. Forming said layers by the novel dry spraying process of the invention further helps to reduce the said layer-core interface migration of catalyst element(s). The optional adoption of the novel treatment procedure of the invention for said carrier materials enhances said harmonisation and lowers diffusion resistances

Said dry spraying may be carried out by any conventional method within the scope of the invention including by fluidisation procedures. Preferably, the process of spraying is by means of one or more suitable spray guns. The propellant may be any gas but is preferably air. The relative movement during said dry spraying passes may be provided by movement imparted to said spray gun(s) or to the platform holding the core particulate material to be sprayed or both.

Within the scope of the invention, said relative movement may be reciprocating, oscillatory, vibratory, rotatory or others. Preferably, said platform is a pan coater; the said motion is rotatory and the pan inclined at an angle. Examples of other equipment that can be utilised to carry out the dry spray process of the invention are fluid bed dryers, tablet and capsule coaters and others. All such equipment are within the scope of the invention.

The alumina materials for the said first and second components are separately subjected to pore-modification by calcination procedures. The temperature for said calcination ranges from about 400 C to about 1000 C. The preferred temperature slot is about 500C to 900 C. The calcination period may extend from about 1 to about 10 h and is preferably in the range of about 2 to 6 hours.

The carrier material for dry spraying is preferably ground and milled down to about 5 to about 80 microns, more preferably to about 5 to 20 microns. For milling, dry milling, jet milling, ball/jar milling (wet or dry) or any of the other known processes may be employed. Preferably the jar milling option is adopted.

If ball milling is adopted the preferred ratio of the alumina components and ball media is about 1:0.15 to 1:5 and more preferably about 1:1 to 1:3. The ball milling media may be any of the known ones but are preferably stainless steel, zirconia, or ceramic and more preferably ceramic. The carrier material to be dry sprayed is charged into a pan-coater which is run preferably at about 40 to about 100 rpm and more preferably between about 40 to 60 rpm. Preferably the angle of inclination of the pan coater is maintained at about 30 degrees to 45 degrees.

The carrier material may be wetted before the commencement of the first said spray operation. Said spraying operations are also referred to herein as passes. The wetting may be carried out using any liquid. Preferably, the wetting liquid is distilled water.

The wetting process encourages bonding between the carrier layer and the core surfaces. The non-wetting alternative offers other advantages.

The said preliminary wetting operation may be carried out on the cores before they are charged into the pan coater or after such charging. Preferably, said wetting may be continued for a duration of time such that a pre-determined amount of water is absorbed by the particulate core mass. The range of targeted weight increase during this process is preferably from about 15% by wt to about 45% by wt. and more preferably from about 10% by wt to about 40% by wt.

The duration of said wetting is from about 3 to about 24 h, preferably from about 12 h to 15 h. At the end of the period the spherical elements are dried by a process of contact drying wherein absorbent paper or other material is employed to remove water on the surface.

In another embodiment of the invention, the said wetting of the core material is not carried out. The layered carrier obtained by such a process was found to have better attrition resistance than the product obtained by adopting said wetting, all other parameters being the same.

After the wetting operation, the core spherical elements are subjected to contact drying to remove substantially all free water clinging to the surfaces thereof This may be done by using absorbent paper or other means. The spherical elements mass is now ready for the dry spraying operation. Other methods of removing said surface water are within the scope of the invention.

A said layer may be formed in a single said dry spraying operation or by a plurality thereof each such operation laying a thin deposit of the carrier material on the core surfaces.

Within the scope of the invention, binding and/or bonding agents may be employed during said spraying and layer building operation, or otherwise. Adoption of said binders is preferable. Preferably, a binder composition comprising three individual binder components is employed. The desired characteristics of the three said binder components are elaborated herein below.

Thus, the known binder materials fall into three classes and each of the three binder components going into the mixture of the invention can be any member of the respective class within the scope of the invention. Within the scope of the invention any of the known binder materials may be employed.

As mentioned, the preferred binder of the invention is a composition. Said composition comprises first, second and third components, each of which is an individual binder material. Said first component comprises a colloidal solution of alumina or other metal oxide material. Said second component is one that imparts or enhances the acid resistance of the LCC. The preferred material for the second component is aluminium nitrate. Said third component is an organic binder that enhances the viscosity of the composition. The preferred organic binder of the invention is HPMC(hydroxypropyl methyl cellulose).

Within the scope of the invention the application of the binder may also be carried out simultaneously with the spraying. All arrangements, simultaneous, sequential or hybrids of the two are within the scope of the invention.

Both said first and second classes of binder compounds are generally inorganic compounds. An inorganic binder will fall into one of the said two classes but some inorganic binders may belong to both, the properties of these binder compounds being such that they provide binding action as also impart acid resistance to the LCC as a whole.

With reference to said classes, an individual member of a class may be adopted or a mixture of the said members of the class, within the scope of the invention.

Thus, the binder solution(composition) can also be looked upon as a mixture of one or more inorganic binder compounds and an organic binder compound. The binder compound is dispersed or dissolved in a suitable solvent which may be water or a mixture of water and a lower alcohol(s). The spraying of the binder solution is carried out by means of spray nozzles installed over the said pan coater.

The binder composition of the invention is preferably applied on the base material, said base material being either uncoated spherical core elements or partially coated spherical core elements that are in different stages of the coating process. Said application by spraying may be before each dry spraying operation or simultaneously therewith.

Said fixing operation is preferably by calcination of the deposited layer. Within the scope of the invention, said fixing by calcination may be carried out at the completion of a layer or during the formation of the layer. In case of the latter, said fixing by calcination may preferably be done after each said spraying operation, that is, upon laying of each deposit of the carrier material.

The calcination process binds the carrier material to the core surface or to a previously laid layer or deposit. Said process also develops the said pores in the deposited layer.
The inorganic binder compounds preferred are, but not limited to, alumina, silica, aluminium nitrate, aluminium phosphate and colloidal alumina sol. The selection of organic binder compounds suitable is from, but is not limited to, HPMC(hydroxypropyl methyl cellulose), starch and other polymers, PVA(polyvinyl alcohol), and PEG(polyethylene glycol) having considerable amount of cross-linking.

The proportion of the binder compound(s) in the binder solution depends on the carrier material loading in the layer. Preferably, the ratio of the binder compound(s) to the solvent is from about 10% by wt. to about 25% by wt. More, preferably said ratio is about 20% by wt.

The preferred range for inorganic binders with respect to the amount of carrier material is about 1% by wt to about 10% by wt and preferably from 1% to 6% by wt.

The corresponding figure for organic binder(s) is upto about 3% by wt. and preferably upto about 0.5% by wt.

The inorganic and organic binder components cited above are precursors that undergo decomposition on heating. The preferred temperature range for said heating operation is from about 100 C to about 400 C and more preferably from about 100 C to 270 C.

The solvent for the binder solution is preferably either water or a water/lower alcohol mixture. If the latter is used the preferred ratio of water to alcohol is from about 0 to about 10 v/v, more preferably about 0 to 5 v/v.

The loading of the carrier material, with or without the catalyst thereof, on said spherical support may be from about 10% to 80% by wt of the support(core material/base material). Preferably, the loading is about 20% to 40% by wt.

After the coating operation, the 'green' spherical carriers are subjected to a process of calcination at temperatures from about 100 C to 900 C, preferably in the temperature range from about 100 C to 500 C.

Any active catalyst metal(and/or compound) may be deposited on said carriers before said dry spraying and layer formation and/or on the carriers after they have been deposited in the form of coatings on said spherical supports. Commonly said active catalyst metals are from Group III to XII of the periodic table (1UPAC). Widely used active metals are Pt, Pd, Rh, Re, Ru, Os, Sn and Ir.

Preferred promoter / modifying /dispersing agents are elements/oxides of boron, barium, Li, Ca, Ba, Zn, Si, Sm, Ce and other alkali and alkaline earth metals. Any combination of these elements/oxides may be installed on the said carrier layer(s) of the invention. The factors affecting the choice of said elements are the reaction to be catalysed, the degree of catalysis desired and others.

The slurry-based layering processes of prior art are complex and cumbersome. In contrast, the dry spray layering process of the invention is simple and for thin layers, if required, the operation can be reduced to a single spraying step.

In one embodiment of the invention, the carrier material is dry sprayed on said spherical elements. After every carrier material spraying pass a binder solution is sprayed. The operation is carried out in a pan coater whose rpm is set at about 40 to 100 rpm. Preferably, the rotation is kept at about 40 to 60 rpm. Agitation(pan rotation) may be continued from about 0.5 h to about 3 hours. Preferably, the agitation is continued for about 1 to 2 h per batch. The pan angle is set at about 5 deg. to 70 degrees, preferably it is kept at about 30 deg to 45 deg.

Wetting of the core material prior to coating is adopted. Wetting is carried out by immersion in distilled water. The wetting period is preferably from about 3 h to about 24 h, preferably from about 12 h to 15 hours. The wetted spherical elements are pat dried. The weight increase of the core material is targeted at from about 5% to 25% by wt. More preferably the spherical elements where the weight increase is in the range of about 10% to 20% by wt is taken up for dry spraying of the carrier material. Most preferably said range is 15% to 20% by wt.

The "green" layered carriers are then calcined at temperatures ranging from about 100 C to about 900 C, preferably in the range of about 100 C to 500 C for a period of time from about 1 h to about 7 h, preferably from about 2 h to about 5 hours.

In another embodiment, said wetting step is not included, all other steps being as in the abovementioned embodiment.

This invention has practically carried out both the abovementioned embodiment procedures and has found that the layered carrier product obtained by the embodiment wherein the wetting step is excluded has better attrition resistance than that obtained by the embodiment wherein wetting is provided. This aspect is further discussed herein below and the experimental data presented in Table IV further herein.

The novel features of this invention are easily and simply adapted to any said catalyst assembly and are particularly relevant for catalyst situations where diffusion limitation subsists.

Within the scope of the invention, a said layer may be laid in a single pass(operation) of said dry spray or multiple passes may be employed to build up a layer. The layered catalyst carriers and the processes of the invention are easily and simply adapted for continuous processing. Such continuous processes and products thereof are within the scope of the invention.

The adoption of a mixture of wide pore alumina derived by a process of precipitation and an alumina derived chemically through the alkoxide route in the LCC of the invention was found to offer benefits also as regards other properties of the LCC such as the IB( Impact Breakage) and crushing strength(CS). IB( Impact Breakage) of the LCC formed from mixtures of compound A and B were found to be higher than the LCCs obtained by adopting either compounds A or B alone. This is indicated by the experimental results presented in Table I. As will be observed, there is a synergy benefit.

The variation of the IB values with the composition of the carrier material is also shown in Table I. The 2.33:1 mixture(of A:B) appears to show better physico-chemical properties with respect to IB in addition to the parameter of catalyst efficiency.

Values given in Table I are for layers comprising compound A alone, compound B alone and mixtures of A and B. Two different mixtures have been studied. The table demonstrates the synergy arising from the use of a mixture of compounds A and B.

A very high level of control over the properties of the final catalyst assembly is offered by the carrier material mixture and the dry spray procedure of the invention. It permits engineering of the layers to realise specific parametric values. This is unlike as in prior art methods. The parameters that can be effectively controlled are the layer thickness and its uniformity, reduction of diffusion resistances, harmonisation of the said resistances, catalyst efficiency and selectivity, CS, IB, CBD and others.

The degree of loading of the carrier material on the cores as well as the ratio of the compound A to compound B was found to influence the IB, CS and other properties including performance. is, the optimum value of 2.33:1 by wt. Material A and B are mixtures of theta and delta alumina in all the examples. The same binder(HPMC) has been used in all the three samples.

Within the range investigated increased said loading results in increased layer thickness. The layer thickness was established by means of SEM images.


Table IV displays the parameter values for two experiments carried out to ascertain the effect of wetting of the core particles before being subjected to the dry spraying of the carrier material thereupon. In the 'wet' experiment the spherical cores were wetted with water prior to the dry spray operation for layer deposition. In the 'dry' experiment said pre-wetting operation was not resorted to. In these two experiments, identical amounts of water were used with the binder.

The same carrier material mixture having the A: B ratio of 2.33:1 by wt was used in the study. The same binder and carrier material loading have been adopted in the two experiments. As mentioned hereinabove, the adoption of dry procedure wherein the core particles are not pre-wetted prior to the dry spraying yields a LCC having improved crushing strength (CS). The effects on the other parameters are small.

The higher level of uniformity in carrier layer thickness that can be achieved over the prior art by the dry spray process of the invention is confirmed by SEM(Scanning Electron Microscope) images. SEM image of a carrier layer deposited by the dry spray process of the invention was compared with the SEM image of a carrier layer obtained by following one of the prior art slurry-based procedures.. Said cores in both experiments are spherical and of approximately equivalent diameters.

The layer thickness observed in the image of the layer according to the invention is about 235 to 291 microns, that is, a spread of about + 28 units about the mean. The layer thickness in the image of the prior art process based layer is from about 53 to 205 microns. The variation in this case is about + 76 units about the mean.

As mentioned hereinabove, this invention provides for lower diffusion resistance and the said harmonisation thereof by adoption of thin and uniform layers and a wide pore carrier material which is used in the form of a mixture with a said second carrier material component. The efficacy of the LCC of the invention should therefore be evident from variations in catalyst performance such as product selectivity and stability.

Catalytic trials using the LCC of the invention were conducted in confidence jointly with an actual user organisation that carries out laying of catalyst elements on layered catalyst carriers. This was done at their research laboratory where a rig was set up to verify the increased efficacy of a catalyst assembly using the LCC of the invention.
Suitable catalyst elements for catalysing a hydrocarbon dehydrogenation reaction were dispersed on the LCC of the invention and the catalyst assembly formed. The catalyst assembly spherical particles were slurried in the hydrocarbon to be dehydrogenated. The progress of the reaction was observed by taking BN(Bromine Number) measurements at successive time points. Layered catalyst carriers of two different specifications were used in the investigation. One of the LCC sample used had a wider mean pore dia. than the other. The mean pore dia. data of the two samples are presented in Table V below. The catalyst mounted on the wide-pore LCC of the invention exhibited higher selectivity, stability and durability than the catalyst mounted on the LCC with smaller pore dia.


The expectation of this invention, that the larger pore dia sample would exhibit better performance as well as lower deactivation was confirmed by the experimental results.

The loading of the LCC was the same in both the trials.

The higher activity and stability shown of the larger pore diameter sample is attributable to reduced formation of by-products such as aromatics, which are known precursors of coke formation on the catalyst, which can cause rapid deactivation thereof.

This invention observes that increased diffusion resistances such as found in thick layers tend to increase said DL problems. The interior sites become difficult to access.
It also causes increases in residence times. This increases the scope for said side reactions which brings down the efficiency, selectivity and stability of the catalyst.

This scenario can be expected to occur even where the thickness of the thick layers employed is quite uniform.

Four catalyst assemblies Nos. 1,2,3 and 4 were prepared with different carrier material loading of 20%, 25%, 33% and 40% by wt. respectively. The carrier material used was a mixture of compounds A and B in accordance with the invention.

The loading % is: Wt. of the carrier material mixture x 100 wt of the cores

The A:B ratio was the same for the four said assemblies. Increased loading results in increased layer thickness. The four samples thus comprised increasingly thick layers going from sample 1 to sample 4.

It was found that the catalysts performance passes through a maximum at about 33% by wt. loading. The maximum represents the optimum layer thickness. Beyond the maximum the diffusion resistance as also the variation in diffusion resistances across the layer surfaces increases bringing down the catalysts performance.

In order to provide a clearer understanding of the invention and without limitation to the scope of the invention, a few embodiments thereof are described in detail herein below.

In the embodiments/examples given herein below and in the said catalytic dehydrogenation studies/experiments, the carrier material mixture comprised a theta and delta alumina mixture obtained by a precipitation route(compound A) with a theta alumina-delta alumina mixture derived by the alkoxide route(compound B). The carrier material mixture was subjected to calcination and other treatment according to the procedure of the invention.

In each of the examples described herein below, a batch of about 100 gm. of the calcined layered catalyst carrier product was accurately weighed and charged into the attrition apparatus which comprised a hollow drum fitted with a baffle. The drum was rotated at about 60 rpm for about 30 min. The fines were collected, weighed and the Impact Breakage (IB) percent values were calculated using the expression:
IB= [(Weight of fines in gm)/(Total weight of the layered catalyst carrier material)] x 100

The evaluated physical properties of the layered catalyst carriers obtained in the examples given hereinbelow are presented in Tables I to V hereinabove. The tables present the following parameters:

CBD = Compact Bulk Density in gm/cc
CS = Crushing Strength in kg.
BET = Brunauer, Emmet & Teller Surface Area in m2/g
IB = Impact breakage in %
Layer thickness in microns, pore diameter in deg. Angstrom and others.

Example 1

Indialite spheres (1.8mm, 1000g) were taken in a polypropylene beaker of capacity 5000 mL. To this was added distilled water (1500g) under stirring to ensure that the indialite is completely submerged. The mixture was allowed to stand for 12h. After the stipulated time, the wet indialite was spread on an adsorbent paper-lined tray. Adequate precaution to ensure that clumping did not occur was taken. Further the indialite spheres were gradually patted to semi-dryness with paper towels. An increase in weight of indialite by 15% was observed.

The indialite was transferred to the pan coater fitted with a baffle. The pan of the pan coater was then set into motion and an rpm of 60 was maintained. The angle of the pan coater was maintained at 45° throughout the layering process.

The outer refractory oxide (400g) comprised a single alumina component [Component B] calcined to 900°C followed by jar-milling to desired PS(particle size) of 20 microns. The binder solution comprised colloidal alumina sol (20 wt% solution; 4%; 16g), Al (NO3)3 9H2O (5%; 20g) and hydroxypropyl methyl cellulose (0.2%, 0.8g) dispersed in 250g of distilled water.

The process of layering of indialite cores by outer refractory oxide (carrier material mixture-in this case component B) was as follows. Initially a small amount of outer refractory oxide (6g) was sprayed through a dosing element on the wet indialite in the rotating pan. It was allowed to mix thoroughly. Next, binder solution (4.2g) was sprayed through another dosing element on the indialite. Care was taken to see that the alumina did not stick to the wall surface of the pan. Post-binder spraying, another batch of outer refractory oxide (6g) was again sprayed. The process was continued till all the outer refractory oxide and binder solution were exhausted simultaneously.

The resulting 'green' coated spheres were unloaded from the pan coater into ceramic trays. A single layer of'green' coated indialite spheres taken in a ceramic tray was subjected to calcination at 550°C for 3h

Accurately, weighed calcined, layered supports (l00 gms) were taken in the attrition apparatus, a hollow drum fitted with a baffle and rotated at 60 rpm for 30 minutes.

The fines were collected, weighed and the impact breakage (IB) was determined as the weight percent fines generated versus the total weight of the spheres.

The IB for this sample was found to be 1.7%.

The outer refractory oxide loading percent of this sample was found to be 40%.

Example 2

Indialite spheres (1.8mm, 1000g) were taken in a polypropylene beaker of capacity 5000 mL. To this was added distilled water (1500g) under stirring to ensure that the indialite is completely submerged. The mixture was allowed to stand for 12h. After the stipulated time, the wet indialite was spread on an adsorbent paper-lined tray. Adequate precaution to ensure that clumping did not occur was taken. Further the indialite spheres were gradually patted to semi-dryness with paper towels. An increase in weight of indialite by 15% was observed.

The indialite was transferred to the pan coater fitted with a baffle. The pan of the pan coater was then set into motion and an rpm of 60 was maintained. The angle of the pan coater was maintained at 45° throughout the layering process.

The outer refractory oxide (400g) comprised mixed [Component A : Component B = 1:] alumina components calcined as a mixture to 900°C followed by jar-milling to desired PS of 5 microns (Component A) and 20 microns (Component B). The binder solution comprised colloidal alumina sol (20 wt% solution; 4%; 16g), Al (NO3)3 9H2O (5%; 20g) and hydroxypropyl methyl cellulose (0.2%, 0.8g) dispersed in 250g of distilled water.

The process of layering of the indialite cores by the outer refractory oxide(carrier material mixture) was as disclosed under Example 1 hereinabove.

The resulting 'green' coated spheres were unloaded from the pan coater into ceramic trays. A single layer of'green' coated indialite spheres taken in a ceramic tray was subjected to calcination at 550°C for 3h

Accurately, weighed, calcined, layered supports (lOOgms) were taken in the attrition apparatus, a hollow drum fitted with a baffle and rotated at 60 rpm for 30 minutes.

The fines were collected, weighed and the impact breakage (IB) was determined as the weight percent fines generated versus the total weight of the spheres.
The IB for this sample was found to be 1.8%.

The outer relractory oxide loading percent of this sample was found to be 40%.

Example 3

Indialite spheres (1.8mm, 1000g) were taken in a polypropylene beaker of capacity 5000 mL. To this was added distilled water (1500g) under stirring to ensure that the indialite is completely submerged. The mixture was allowed to stand for 12h. After the stipulated time, the wet indialite was spread on an adsorbent paper-lined tray. Adequate precautions to ensure that clumping did not occur were taken. Further the indialite spheres were gradually patted to semi-dryness with paper towels. An increase in weight of indialite by 15% was observed.

The indialite was transferred to the pan coater fitted with a baffle. The pan of the pan coater was then set into motion and an rpm of 60 was maintained. The angle of the pan coater was maintained at 45° throughout the layering process.

The outer refractory oxide (200g) comprised mixed [Component A : Component B = 2.33:1] alumina components calcined as a mixture to 900°C followed by jar-milling to desired PS of 5 microns (Component A) and 20 microns (Component B). The binder solution comprised colloidal alumina sol (20 wt% solution; 4%; 8g), Al (NO3)3 9H2O (5%; 10g) and hydroxypropyl methyl cellulose (0.2%, 0.4 g) dispersed in 50g of distilled water.

The process of layering of the indialite cores by the outer refractory oxide(carrier material mixture) was as disclosed under Example 1 hereinabove.

The resulting 'green' coated spheres were unloaded from the pan coater into ceramic trays. A single layer of'green' coated indialite spheres taken in a ceramic tray was subjected to calcination at 550°C for 3h

Accurately, weighed calcined, layered supports (lOOgms) were taken in the attrition apparatus, a hollow drum fitted with a baffle and rotated at 60 rpm for 30 minutes.

The fines were collected, weighed and the impact breakage (IB) was determined as the weight percent fines generated versus the total weight of the spheres.
The IB for this sample was found to be <1.0%.

The outer refractory oxide loading percent of this sample was found to be 20%.

Example 4

Indialite spheres (1.8mm, 1000g) were taken in a polypropylene beaker of capacity 5000 mL. To this was added distilled water (1500g) under stirring to ensure that the indialite is completely submerged. The mixture was allowed to stand for 12h. After the stipulated time, the wet indialite was spread on an adsorbent paper-lined tray. Adequate precaution to ensure that clumping did not occur was taken. Further the indialite spheres were gradually patted to semi-dryness with paper towels. An increase in weight of indialite by 15% was observed.

The indialite was transferred to the pan coater fitted with a baffle. The pan of the pan coater was then set into motion and an rpm of 60 was maintained. The angle of the pan coater was maintained at 45° throughout the layering process.

The outer refractory oxide (400g) comprised mixed [Component A : Component B = 2.33:1] alumina components calcined as a mixture to 900°C followed by jar-milling to desired PS of 5 microns (Component A) and 20 microns (Component B). The binder solution comprised colloidal alumina sol (20 wt% solution; 4%; 16g), Al (NO3)3 9H2O (5%; 20g) and hydroxypropyl methyl cellulose (0.2%, 0.8g) dispersed in 250g of distilled water.

The process of layering of the indialite cores by the outer refractory oxide(carrier material mixture) was as disclosed under Example 1 hereinabove.

The resulting 'green' coated spheres were unloaded from the pan coater into ceramic trays. A single layer of 'green' coated indialite spheres taken in a ceramic tray was subjected to calcination at 550°C for 3h

Accurately weighed, calcined, layered supports (100gms) were taken in the attrition apparatus, a hollow drum fitted with a baffle and rotated at 60 rpm for 30 minutes.

The fines were collected, weighed and the impact breakage (IB) was determined as the weight percent fines generated versus the total weight of the spheres.

The IB for this sample was found to be < 1.0 %.

The outer refractory oxide loading percent of this sample was found to be 40%.

Example 5

Dry indialite spheres (1.8mm, 1000g) were transferred to the pan coater fitted with a baffle. The pan of the pan coater was then set into motion and an rpm of 60 was maintained. The angle of the pan coater was maintained at 45° throughout the layering process.

The outer refractory oxide (300g) comprised mixed [Component A : Component B = 2.33:1] alumina components calcined as a mixture to 900°C followed by jar-milling to desired PS of 5 microns (Component A) and 20 microns (Component B). The binder solution comprised colloidal alumina sol (20 wt% solution; 4%; 12g), Al (NO3)3 9H2O (5%; 15g) and hydroxypropyl methyl cellulose (0.2%, 0.6g) dispersed in 300g of distilled water.

The process of layering of the indialite cores by the outer refractory oxide(carrier material mixture) was as disclosed under Example 1 hereinabove.

The resulting 'green' coated spheres were unloaded from the pan coater into ceramic trays. A single layer of 'green' coated indialite spheres taken in a ceramic tray was subjected to calcination at 550°C for 3h.

Accurately, weighed calcined, layered supports (100gms) were taken in the attrition apparatus, a hollow drum fitted with a baffle and rotated at 60 rpm for 30 minutes.

The fines were collected, weighed and the impact breakage (IB) was determined as the weight percent fines generated versus the total weight of the spheres.

The IB for this sample was found to be 1.2%.

The outer refractory oxide loading percent of this sample was found to be 30%.

Example 6

Dry indialite spheres (1.8mm, 1000g) were transferred to the pan coater fitted with a baffle. The pan of the pan coater was then set into motion and an rpm of 60 was maintained. The angle of the pan coater was maintained at 45° throughout the layering process.

The outer refractory oxide (250g) comprised mixed [Component A : Component B = 2.33:1] alumina components calcined as a mixture to 900°C followed by jar-milling to desired PS of 5 microns (Component A) and 20 microns (Component B). The binder solution comprised colloidal alumina sol (20 wt% solution; 4%; 10g), Al (NO3)3 9H2O (5%; 12.5g) and hydroxypropyl methyl cellulose (0.2%, 0.5g) dispersed in 250g of distilled water.

The process of layering of the indialite cores by the outer refractory oxide(carrier material mixture) was as disclosed under Example 1 hereinabove.

The resulting 'green' coated spheres were unloaded from the pan coater into ceramic trays. A single layer of'green' coated indialite spheres taken in a ceramic tray was subjected to calcination at 550°C for 3h

Accurately weighed, calcined, layered supports (100gms) were taken in the attrition apparatus, a hollow drum fitted with a baffle and rotated at 60 rpm for 30 minutes.

The fines were collected, weighed and the impact breakage (IB) was determined as the weight percent fines generated versus the total weight of the spheres.

The IB for this sample was found to be <1%.

The outer refractory oxide loading percent of this sample was found to be 25%.

Example 7

Dry indialite spheres (1.8mm, 1000g) were transferred to the pan coater fitted with a baffle. The pan of the pan coater was then set into motion and an rpm of 60 was maintained. The angle of the pan coater was maintained at 45° throughout the layering process.

The outer refractory oxide (200g) comprised mixed [Component A : Component B = 2.33:1] alumina components calcined as a mixture to 900°C followed by jar-milling to desired PS of 5 microns (Component A) and 20 microns (Component B). The binder solution comprised colloidal alumina sol (20 wt% solution; 4%; 8g), Al (NO3)3 9H2O (5%; 10g) and hydroxypropyl methyl cellulose (0.2%, 0.4g) dispersed in 200g of distilled water.

The process of layering of the indialite cores by the outer refractory oxide(carrier material mixture) was as disclosed under Example 1 hereinabove.

The resulting 'green' coated spheres were unloaded from the pan coater into ceramic trays. A single layer of green' coated indialite spheres taken in a ceramic tray was subjected to calcination at 550°C for 3h.

Accurately weighed, calcined, layered supports (100gms) were taken in the attrition apparatus, a hollow drum fitted with a baffle and rotated at 60 rpm for 30 minutes.

The fines were collected, weighed and the impact breakage (IB) was determined as the weight percent fines generated versus the total weight of the spheres.

The IB value of the product was found to be < 1.

The outer refractory oxide loading percent of this sample was found to be 20%.

Example 8

Dry indialite spheres (1.8mm, 1000g) were transferred to the pan coater fitted with a baffle. The pan of the pan coater was then set into motion and an rpm of 60 was maintained. The angle of the pan coater was maintained at 45° throughout the layering process.

The outer refractory oxide (250g) comprised mixed [Component A : Component B = 2.33:1] alumina components calcined as a mixture to 900°C followed by jar-milling to desired PS of 5 microns (Component A) and 20 microns (Component B). The binder solution comprised colloidal alumina sol (20 wt% solution; 4%; 10g ), Al (NO3)3 9H20 (5%; 12.5g) and polyethylene glycol (0.2%, 0.5g) dispersed in 250g of distilled water.

The process of layering of the indialite cores by the outer refractory oxide(carrier material mixture) was as disclosed under Example 1 hereinabove.

The resulting 'green' coated spheres were unloaded from the pan coater into ceramic trays. A single layer of' green' coated indialite spheres taken in a ceramic tray was subjected to calcination at 550°C for 3h.

Accurately weighed, calcined, layered supports (100gms) were taken in the attrition apparatus, a hollow drum fitted with a baffle and rotated at 60 rpm for 30 minutes.

The fines were collected, weighed and the impact breakage (IB) was determined as the weight percent fines generated versus the total weight of the spheres.

The IB value of the product was found to be 1.5.

The outer refractory oxide loading percent of this sample was found to be 25%.

Example 9

Dry indialite spheres (1.8mm, 1000g) were transferred to the pan coater fitted with a baffle. The pan of the pan coater was then set into motion and an rpm of 60 was

maintained. The angle of the pan coater was maintained at 45° throughout the layering process.
The outer refractory oxide (250g) comprised mixed [Component A : Component B = 2.33:1] alumina components calcined as a mixture to 900°C followed by jar-milling to desired PS of 5 microns (Component A) and 20 microns (Component B). The binder solution comprised colloidal alumina sol (20 wt% solution; 4%; 10g), Al (NO3)3 9H2O (5%; 12.5g) and polyvinyl alcohol (0.2%, 0.5g) dispersed in 250g of distilled water

The process of layering of the indialite cores by the outer refractory oxide(carrier material mixture) was as disclosed under Example 1 hereinabove.

The resulting 'green' coated spheres were unloaded from the pan coater into ceramic trays. A single layer of'green' coated indialite spheres taken in a ceramic tray was subjected to calcination at 550°C for 3h.

Accurately weighed, calcined, layered supports (100gms) were taken in the attrition apparatus, a hollow drum fitted with a baffle and rotated at 60 rpm for 30 minutes.

The fines were collected, weighed and the impact breakage (IB) was determined as the weight percent fines generated versus the total weight of the spheres.

The IB value of the product was found to be 1.8.

The outer refractory oxide loading percent of this sample was found to be 25%.

Example 10

Dry indialite spheres (1.8mm, 1000g) were transferred to the pan coater fitted with a baffle. The pan of the pan coater was then set into motion and an rpm of 60 was maintained. The angle of the pan coater was maintained at 45° throughout the layering process.

The outer refractory oxide (250g) comprised mixed [Component A : Component B = 2.33:1] alumina components calcined as a mixture to 900°C followed by jar-milling to desired PS of 5 microns (Component A) and 20 microns (Component B). The binder solution comprised colloidal alumina sol (20 wt% solution; 4%; l0 g), Al (NO3)3 9H2O (5%; 12.5g) and starch (0.2%, 0.5g) dispersed in 250g of distilled water.

The process of layering of the indialite cores by the outer refractory oxide(carrier material mixture) was as disclosed under Example 1 hereinabove.

The resulting 'green' coated spheres were unloaded from the pan coater into ceramic trays. A single layer of'green' coated indialite spheres taken in a ceramic tray was subjected to calcination at 550°C for 3h.

Accurately weighed, calcined, layered supports (100gms) were taken in the attrition apparatus, a hollow drum fitted with a baffle and rotated at 60 rpm for 30 minutes.

The fines were collected, weighed and the impact breakage (IB) was determined as the weight percent fines generated versus the total weight of the spheres.

The IB value of the product was found to be 1.2.

The outer refractory oxide loading percent of this sample was found to be 25%.

Example 11

Dry indialite spheres (1.8mm, 1000g) were transferred to the pan coater fitted with a baffle. The pan of the pan coater was then set into motion and an rpm of 60 was maintained. The angle of the pan coater was maintained at 45° throughout the layering process.

The outer refractory oxide (250g) comprised mixed [Component A : Component B = 2.33:1] alumina components calcined as a mixture to 900°C followed by jar-milling to desired PS of 5 microns (Component A) and 20 microns (Component B). The binder solution comprised colloidal alumina sol (20 wt% solution; 4%; 10g), Al (NO3)3 9H2O (5%; 12.5g) and methyl cellulose (0.2%, 0.5g) dispersed in 250g of distilled water.

The process of layering of the indialite cores by the outer refractory oxide(carrier material mixture) was as disclosed under Example 1 hereinabove.

The resulting 'green' coated spheres were unloaded from the pan coater into ceramic trays. A single layer of 'green' coated indialite spheres taken in a ceramic tray was subjected to calcination at 550°C for 3h.

Accurately weighed, calcined, layered supports (100gms) were taken in the attrition apparatus, a hollow drum fitted with a baffle and rotated at 60 rpm for 30 minutes.

The fines were collected, weighed and the impact breakage (IB) was determined as the weight percent fines generated versus the total weight of the spheres.

The IB value of the product was found to be <1.

The outer refractory oxide loading percent of this sample was found to be 25%.

The IB values in the examples as a whole were found be below about 5% by wt and in many cases below about 1% by wt. The average was about 1 to 2% by wt.

Example 12

Indialite spheres (1.8mm, 1000g) were taken in a polypropylene beaker of capacity 5000 mL. To this was added distilled water (1500g) under stirring to ensure that the indialite is completely submerged. The mixture was allowed to stand for 12h. After the stipulated time, the wet indialite was spread on an adsorbent paper-lined tray.

Adequate precaution to ensure that clumping did not occur was taken. Further the indialite spheres were gradually patted to semi-dryness with paper towels. An increase in weight of indialite by 15% was observed.

The indialite was transferred to the pan coater fitted with a baffle. The pan of the pan coater was then set into motion and an rpm of 60 was maintained. The angle of the pan coater was maintained at 45° throughout the layering process.

The outer refractory oxide (400g) comprised a single [Component A] alumina component calcined to 900°C followed by jar-milling to desired PS(particle size) of 5 microns. The binder solution comprised colloidal alumina sol (20 wt% solution; 4%; 16g), Al (NO3)3 9H2O (5%; 20g) and hydroxypropyl methyl cellulose (0.2%, 0.8g) dispersed in250g of distilled water.

The process of layering of the indialite cores by the outer refractory oxide(carrier material mixture) was as disclosed under Example 1 hereinabove.

The resulting 'green' coated spheres were unloaded from the pan coater into ceramic trays. A single layer of 'green' coated indialite spheres taken in a ceramic tray was subjected to calcination at 550°C for 3h Accurately weighed calcined, layered supports (100gms) were taken in the attrition apparatus, a hollow drum fitted with a baffle and rotated at 60 rpm for 30 minutes. The fines were collected, weighed and the impact breakage (IB) was determined as the weight percent fines generated versus the total weight of the spheres.

The IB for this sample was found to be 21%.

The outer refractory oxide loading percent of this sample was found to be 40%.

In the process claims herein below, the terms 'particulate core material' or 'core material' is employed to refer not only to the material at the start of the process but also to the material during the process, that is material-in-process at various stages of the process. Said material-in-process is also referred to as base material herein. No ambiguity arises from this as the meaning is apparent from the context. The meaning appropriate to the context may be adopted.

Embodiments and variations other than described hereinabove are feasible by persons skilled in the art and the same are within the scope and spirit of this invention.

We claim:

1. A process for making layered catalyst carrier(s) such as for applications in petroleum refining, petrochemicals and hydrocarbon processing and other sectors, comprising particulate core material having one or more layers(coatings) of catalyst carriers provided on the surfaces thereof, said process comprising the steps of:

(i) providing said particulate core material, and said carrier(s) material in powder form;

(ii) applying a binder material on said particulate core material;

(iii) depositing said carrier powder on said core particle surfaces in one or more operations to obtain one or more deposits of said powder laid thereupon; characterised in said deposition being carried out by dry spraying of said powder onto the base material in one or more operations by means of a gaseous propellant;

(iv) repeating the depositing operation till the generation of the required layer
thickness(es) and the required number of said layer(s); and

(v) fixing said deposits and/or layer(s) onto the said base material or surfaces; the said carrier material being deposited comprising catalyst element(s) dispersed/impregnated thereupon or otherwise, and said base material being agitated during the course of said spraying.

2. The process as claimed in the preceding claim 1 wherein each said spraying operation is followed by a said fixing operation.

3. The process as claimed in the preceding claim 2 wherein said fixing operation comprises calcination of the said deposit(s).

4. The process as claimed in any of the preceding claims 1 to 3 wherein said propellant gas is air.

5. The process as claimed in any of the preceding claims 1 to 4 wherein said binder material is applied upon the said base material before each said spraying operation.

6. The process as claimed in any of the preceding claims 1 to 5 wherein said binder material is a composition comprising a first, second and third binder material components, said first comprising a colloidal solution(col) of a metal oxide, or a mixture thereof, said second being a material that imparts acid resistance to the said layer(s), or a mixture thereof, and the said third comprising an organic binder material that enhances the viscosity of the said composition, said first, second and third components being preferably an alumina col, aluminium nitrate and HPMC(hydroxypropyl methyl cellulose) respectively.

7. The process as claimed in any of the preceding claims 1 to 6 wherein the said base material is wetted before said dry spraying of the powdered carrier material, the wetting material being preferably water.

8. The process as claimed in the preceding claim 7 wherein said wetting operation is carried out for a duration of time such as to yield water absorption from about 15% by wt. to about 45% by wt., preferably from about 10% by wt. to about 40% by wt.

9. The process as claimed in any of the preceding claims 1 to 8 wherein said core material comprises indialite.

10. The process as claimed in any of the preceding claims 1 to 9 wherein and said powdered carrier material comprises a mixture of a first carrier material component and a second carrier material component, said first being a wide pore carrier material and the said second being one that is either a peptisable carrier material or a col or sol thereof, or a mixture thereof.

11. The process as claimed in the preceding claim 10 wherein both said first and second carrier materials are aluminas, the first being derived by precipitation from a solution thereof and the second being derived by the alkoxide route.

12 The process as claimed in the preceding claim 11 wherein said first and second carrier material aluminas are either delta-alumina or theta alumina or mixtures thereof.

13. The process as claimed in the preceding claim 12 wherein the ratio of said first and second aluminas is upto about 10:1 by wt, preferably from about 2:1 to about 2.5:1 by wt.

14. The process as claimed in any of the preceding claims 1 to 13 wherein the said powdered carrier material is of a size from about 5 to about 90 microns and preferably from about 5 to about 20 microns.

15. The process as claimed in any of the preceding claims 1 to 14 wherein the said particulate core material comprises spherical particles.

16. The process as claimed in any of the preceding claims 1 to 15 wherein the said dry spraying operation, including the spraying of binders, if any, is carried out in a pan coater.

17. The process as claimed in the preceding claim 16 wherein the said agitation is provided by rotation of the coater pan, the rotation speed thereof being from about 40 rpm to about 100 rpm, preferably about 40 rpm to about 60 rpm and the pan inclination is from about 30 degrees to about 45 degrees.

18. A process for making layered catalyst carrier(s) such as for applications in petroleum refining, petrochemicals and hydrocarbon processing and other sectors, comprising particulate core material having one or more layers(coatings) of catalyst carriers provided on the surfaces thereof, substantially as herein described.

19 A layered catalyst carrier(s) such as for applications in petroleum refining, petrochemicals and hydrocarbon processing and other sectors, made by the process of the invention as claimed in any of the preceding claims 1 to 18.

20. The layered catalyst carrier(s) as claimed in the preceding claim 19, wherein the thickness of at least one said layer thereof is about 300 micrometers or below.

21. A carrier material for application as catalyst-carrier layers(coatings) on the surfaces of inert core supports of layered catalyst carriers such as for applications in petroleum refining, petrochemicals and hydrocarbon processing and other sectors, comprising a mixture of at least a first, and a second carrier material component, said first component being a wide pore carrier material and the said second carrier material, being either peptisable or being in a col or sol form, or a mixture thereof.

22. The carrier material as claimed in the preceding claim 21 wherein said first carrier material is a wide pore alumina and the said second a peptisable alumina.

23. The carrier material as claimed in the preceding claim 22 wherein said first carrier material is derived by a precipitation route and the said second by the alkoxide route.

24. The carrier material as claimed in the preceding claim 23 wherein the said first and/or second carrier materials are either delta alumina or theta alumina or a mixture thereof.

25. The carrier material as claimed in the preceding claim 24 wherein the ratio of said first and second aluminas is upto about 10:1 by wt, and is preferably about 2:1 to 2.5:1 by wt.

26. A carrier material for application as catalyst-carrier layers(coatings) on the surfaces of inert core supports of layered catalyst carriers such as for applications in petroleum refining, petrochemicals and hydrocarbon processing and other sectors, substantially as herein described.

27. A layered catalyst carrier(s) such as for applications in petroleum refining, petrochemicals and hydrocarbon processing and other sectors, comprising particulate core material having one or more layers(coatings) of catalyst carriers provided on the surfaces thereof, wherein the carrier material of at least one layer thereof comprises a said mixture of first and second carrier material components, as claimed in any of the preceding claims 21 to 26.

28. The layered catalyst carrier(s) as claimed in the preceding claim 27 wherein at least one said carrier layer thereof is a dry sprayed layer made by the process as claimed in any of the preceding claims 1 to 18.

29. The layered catalyst carrier(s) as claimed in any of the preceding claims 27 and 28 and comprising a single said catalyst carrier layer.

30. The layered catalyst carrier(s) as claimed in the preceding claim 29 wherein the carrier layer thickness is not exceeding about 300 micrometers.

31. The layered catalyst carrier(s) as claimed in any of the preceding claims 27 to 30 wherein the said particulate core material is indialite.

32. The layered catalyst carrier(s) as claimed in the preceding claim 31 wherein the said indialite particulate core material comprises substantially spherical particles.

33. A layered catalyst carrier(s) such as for applications in petroleum refining, petrochemicals and hydrocarbon processing and other sectors, comprising particulate core material having one or more layers(coatings) of catalyst carriers provided on the surfaces thereof, at least one said carrier layer thereof having a thickness not exceeding 300 microns.

34. The layered catalyst carrier(s) as claimed in the preceding claim 33 wherein at least one of the said one or more layers thereof are formed by the dry spray layer-making process as claimed in any of the preceding claims 1 to 18.

35. The layered catalyst carrier(s) as claimed in any of the preceding claims 33 and 34 wherein the carrier material of at least one said layer thereof comprises a mixture of first and second carrier material components, as claimed in any of the preceding claims 21 to 26.

36. The layered catalyst carrier(s) as claimed in the preceding claim 35 wherein said first component comprises a wide pore carrier material and the said second being either peptisable or being in a col or sol form, or a mixture thereof

37. The layered catalyst carrier(s) as claimed in the preceding claim 36 wherein said first component comprises a wide pore alumina derived by precipitation from a solution thereof and the said second is an alumina derived by the alkoxide route. .

38. The layered catalyst carrier(s) as claimed in the preceding claim 37 wherein said first and second alumina components are either delta-alumina or theta-alumina, or any mixture of the two.

39. The layered catalyst carrier(s) as claimed in the preceding claim 38 wherein the ratio of said first and second aluminas is upto about 10:1 by wt., and is preferably from about 2:1 to about 2.5:1 by wt.

40. The layered catalyst carrier(s) as claimed in any of the preceding claims 33 to 39 wherein said particulate core material is indialite.

41. The layered catalyst carrier(s) as claimed in the preceding claim 40 wherein said particulate core material comprises substantially spherical particles.

42. The layered catalyst carrier(s) as claimed in any of the preceding claims 33 to 41 and comprising a single said layer.

43. The layered catalyst carrier(s) as claimed in the preceding claim 42 wherein one or more catalyst elements for hydrocarbon dehydrogenation, optionally together with auxiliary materials if any such as promoters and modifiers are dispersed/impregnated on/into said layer.

44. A layered catalyst carrier(s) such as for applications in petroleum refining, petrochemicals and hydrocarbon processing and other sectors, comprising particulate core material having one or more layers(coatings) of catalyst carriers provided on the surfaces thereof, substantially as herein described.

45. A catalyst assembly as herein defined comprising one or more catalyst carrier layers wherein at least one said layer thereof is made by the dry spray process of layer formation as claimed in any of the preceding claims 1 to 18.

46. A catalyst assembly as herein defined comprising a layered catalyst carrier(s) as claimed in any of the preceding claims 19, 20 and 27 to 44.

47. A catalyst assembly as herein defined comprising a layered catalyst carrier(s) wherein the catalyst carrier material in at least one of the one or more catalyst carrier layers thereof is as claimed in any of the preceding claims 21 to 26.

48. A catalyst assembly as herein defined comprising a layered catalyst carrier(s) as claimed in any of the preceding claims 19, 20 and 27 to 44, wherein at least one of the one or more catalyst carrier layers thereof is formed by the dry spray process of layer formation as claimed in any of the preceding claims 1 to 18 and comprises carrier material as claimed in any of the preceding claims 21 to 26.

49. A catalyst assembly as herein defined as claimed in the preceding claim 48 and comprising a single said layer.

50. A catalyst assembly as herein defined as claimed in the preceding claim 49 wherein said layer is of thickness not exceeding about 300 microns.

51. The catalyst assembly as herein defined as claimed in any of the preceding claims 45 to 50, being a dehydrogenation catalyst wherein one or more catalyst elements for hydrocarbon dehydrogenation together with auxiliary materials if any such as promoters and modifiers are dispersed/impregnated on/into the said layer.

52. A catalyst assembly as herein defined comprising a layered catalyst carrier(s) comprising one or more catalyst carrier layers substantially as herein described.

53. A process of admixture for making a synergistic catalyst carrier material mixture comprising at least a first said carrier material and at least a second said carrier material, the former being of the wide pore type and the latter being of the peptisable type or being in the col or sol form or a mixture thereof, comprising the steps of providing the said first and second materials and optionally other said carrier materials followed by admixing of the said first, second and the said other materials.

54. The process of admixture for making a synergistic catalyst carrier material mixture as claimed in the preceding claim 53 wherein the said first and second materials are wide pore alumina and peptisable alumina respectively.

55. The process of admixture for making a synergistic catalyst carrier material mixture as claimed in the preceding claim 54 wherein said wide pore alumina is derived by precipitation from a solution thereof and the said peptisable alumina is derived by the alkoxide route.

56. The process of admixture for making a synergistic catalyst carrier material mixture as claimed in the preceding claim 55 wherein both said first and second aluminas are either theta alumina or delta alumina or a mixture thereof

57. The process of admixture for making a synergistic catalyst carrier material mixture as claimed in the preceding claim 56 wherein the ratio of said first alumina to said second alumina is upto about 10:1 by wt. and is preferably from about 2:1 to about 2.5:1 by wt.

58. A process of admixture for making a synergistic catalyst carrier material mixture substantially as herein described.