DESC:FIELD
The present disclosure relates to a silanated metallosilicate catalyst and a process for preparing the same.
DEFINITIONS
As used in the present disclosure, the following words and phrases are generally intended to have the meaning as set forth below, except to the extent that the context in which they are used to indicate otherwise.
The term “metallosilicates” as used herein refers to porous crystalline substances possessing uniform intra-crystalline channels. Metallosilicates are built of SiO4 and MO4 (M=Aluminium, Boron, Gallium, Iron, Chromium etc.). When M represents Aluminium, the metallosilicate is called aluminosilicate or zeolite; similarly, when M represents B, Ga, Fe, Cr, the metallosilicates are called as borosilicate zeolite, gallosilicate zeolite, ferrisilicate zeolite, Chromosilicate zeolite respectively. Aluminosilicate zeolites occur both naturally and in synthetic forms, however many of the synthetic aluminosilicate zeolite are new and do not have any natural counterpart. Further, most of the other metallosilicates are completely synthetic ones. Thus the term ‘Metallosilicate’ covers the aluminosilicate zeolites as well as other metal ion isomorphously substituted zeolite.
The term “isomorphous substitution” as used herein refers to the replacement of a cation in the lattice by another cation with the same charge and approximately the same size. The substitution of trivalent Aluminium in the zeolite framework with group IIIA trivalent elements (e.g. Boron and Gallium) represent isomorphously substituted metallosilicates (or zeolites). Similarly substitution of Aluminium in the framework with other trivalent elements, e.g, first transition series trivalent elements (e.g. Fe, Cr etc.) represents isomorphous substituted zeolites. All this represents member of metallosilicate. There are various zeolite frameworks known, such as Natrolite framework, Analcime framework and the like.
The term “non-framework trivalent Group IIIA elements” as used herein refers to the Group IIIA elements which are located outside the framework, and in non-tetrahedral co-ordination (typically octahedral ones). In the present disclosure, non-frame work Group IIIA elements comprise aluminium, gallium, and boron, atoms located outside the framework. Other trivalent elements include the first transition series elements, viz., iron, and chromium.
The term “silanation” as used herein refers to a process of covering of a metallosilicate catalyst with alkoxysilane molecules and/or silica. (The alkoxysilane molecule is finally converted to silica)
The term “selectivity” as used herein refers to the ratio of the desired product formed to the total product (desired and undesired) formed.
The term “p-isomer selectivity” as used herein refers to the selectivity/content of p-isomer in the mixed isomers.

The term “selectivating agent” as used herein refers to compounds that can be deposited on the surface of a metallosilicate catalyst. In the present disclosure selectivating agent will not enter into the zeolite pore and hence it passivates only the active sites on the external surface of metallosilicate. Thus, the active sites located inside of pore remain intact.
The term “product selectivity” as used herein refers to a process that occurs when some of the products formed within the pores of the catalyst, diffuse out at a much faster rate (due to smaller size), as compared to those which are too bulky to diffuse out of the pores as observed products. The product selectivity either converts the reactants to less bulky molecules.
The term “reactant selectivity” as used herein refers to the process that occurs when some of the molecules in a reactant mixture are too large to diffuse through the catalyst pores, while the smaller ones can easily diffuse through.
The term “restricted transition-state selectivity” or “transition-state selectivity” as used herein refers to the process that occurs when certain reactions are prevented because the corresponding transition state would require more space than available in the cavities or pores of the catalyst. Reactions requiring smaller transition states proceed unhindered.
BACKGROUND
Diethyl benzene has enormous industrial applications. The para-isomer of diethyl benzene is used as a desorbent for separation of para-xylene from the C8 aromatic mixture by adsorptive process and is also used for producing divinyl benzenes.
‘Selectivation’ by ‘silanation’ is a conventionally known method, which can be used for the enhancement of the para-isomer fraction in a mixture of di-substituted aromatics (para-selectivity). The process of ‘selectivation’ by ‘silanation’ comprises contacting the metallosilicates with an organosilicon compound in a solvent, separation/removal of the solvent followed by drying and calcination of the metallosilicates for deposition of silica or polymeric silica layer on the metallosilicates. The organosilicon compound is usually known as selectivating agent.
The process of silanation can be carried out in vapor phase or liquid phase. Liquid phase silanation is also referred to as ex-situ silanation, or ex-situ selectivation. In the ex-situ silanation process, the metallosilicate is treated by impregnating it with the selectivating agent (organosilicon compound), followed by drying in moist air or in humid atmosphere. The treated metallosilicates are then calcined in an oxygen containing atmosphere to remove the organic material therefrom, and the siliceous material is deposited on the metallosilicates.
Metallosilicates have been used as catalysts for hydrocarbon conversion processes in the area of refining and petrochemicals. Further, metallosilicates such as zeolites are known to possess “reactant selectivity”, “product selectivity,” and “transition selectivity”. Though, zeolite catalyst satisfies the need for high selectivity to products of different molecules, its selectivity does not satisfy the expectation in respect of isomers of the same kind of product.
Further, it is also known in the art that the efficiency of silica deposition, in order to enhance the selectivity of the metallosilicates, depends on the nature/type of the molecular structure of the selectivating agent, i.e., the organosilicon compound. The efficiency of silica deposition also depends on the temperature of silanation, the solvents, or the carrier for the organosilicon compound, the method, or procedure adopted for the selectivation.
One of the major causes for low para-isomer selectivity of diethyl benzenes is due to the unexpectedly ineffective silanation of the metallosilicates. The ineffective silanation may occur due to the presence of non-framework octahedral species of Group IIIA elements and/or other isomorphously substituted for group IIIA elements, such as Fe, Cr and the like, present in the parent zeolite.
Therefore, there is felt a need to improve the selectivity and efficiency of metallosilicate catalyst.
OBJECTS
Some of the objects of the present disclosure, which at least one embodiment herein satisfies, are as follows:
It is an object of the present disclosure to ameliorate one or more problems of the prior art or to at least provide a useful alternative.
An object of the present disclosure is to provide a silanated metallosilicate that improves the para-isomer selectivity in dialkyl benzenes.
Another object of the present disclosure is to provide a process for improving the efficiency of silanated metallosilicates.
Other objects and advantages of the present disclosure will be more apparent from the following description, which is not intended to limit the scope of the present disclosure.
SUMMARY
The present disclosure relates to a silanated metallosilicate catalyst which is substantially free of non-framework group IIIA elements or other elements isomorphously substituted for the group IIIA elements. The silanated metallosilicate catalysts of the present disclosure are used for the conversion of hydrocarbon to at least 99 % para-di-substituted aromatic compounds. The non-framework group IIIA element can be at least one selected from octahedral aluminium and octahedral gallium; and the other elements isomorphously substituted for the group IIIA element can be at least one selected from the group consisting of gallium, iron, chromium, and the like.
The present disclosure further relates to a process for preparing the silanated metallosilicate catalyst. The process comprises the step of treating a metallosilicate with an acid solution at a temperature in the range of 20 oC to 100 oC for a time period in the range of 0.5 hour to 10 hours to obtain a treated metallosilicates which is substantially free of non-framework group IIIA elements or other elements isomorphously substituted for the group IIIA elements. The metallosilicates after treatment with the acid undergoes silanation.
In the process of silanation, the metallosilicate catalyst which is substantially free of non-framework group IIIA elements or other elements isomorphously substituted for the group IIIA elements is soaked in a solution of organosilicon compound for a predetermined time period to obtain a mixture. The solution of organosilicon compound is prepared in a fluid media. The fluid media can be removed from the mixture by distillation to obtain a mass followed by heating the mass to a temperature in the range of 70 oC to 150 oC in the presence of moist air or in a humid atmosphere for a time period in the range of 10 hours to 40 hours to obtain a dried mass. The dried mass is calcined at a temperature in the range of 400 oC to 600 oC for a time period in the range of 4 hours to 10 hours to obtain the silanated metallosilicate catalyst. The so obtained silanated metallosilicate catalyst can further undergo multiple silanation at least for 2 times.
DETAILED DESCRIPTION
During the commercial production of metallosilicates such as zeolite, it is possible that, some impurities may remain in the zeolite, specifically, non-framework Group IIIA element or other elements isomorphously substituted for the group IIIA elements. Such impurities are bound to affect the performance of the catalyst in a detrimental manner. The impurity of the Group IIIA elements or other elements isomorphously substituted for Group IIIA elements, which may be present in a particular co-ordination of the element, may be located in the channels of the metallosilicate and/or at the pore entrance, and may cause a diffusional barrier, so that all the active sites of the metallosilicates /zeolite are not accessible. It might also be possible that the impurity is present on the external surface of the zeolite crystallites. These impurities may also hinder the modification procedures, such as impregnation of other elements, e.g., metals or non-metals in pure or in oxide form. Thus, it is necessary to find a way to get rid of such debris /impurities present in and/or on the metallosilicate, and provide a suitable process to avoid such causes leading to decreased performance of catalysts formulated using such materials.

The process for improving the efficiency of the metallosilicate also affords a way to recover and convert an off-spec metallosilicate batch (usually rejected for low performance), to an on-spec material, thus saving, time, energy, raw materials as well as the operating cost to produce the material. It is also observed that failure occurs during the processing steps of para-isomer selectivity through silanation steps of the conventional multiple silanation procedure. Even with repeated silanation, the para-disubstituted isomer selectivity does not reach to specified level of > 97%.
The present disclosure provides a metallosilicates catalyst that overcomes the drawbacks of the unacceptably low selectivity for para- disubstituted isomer after the silanation treatment, and thus provides an economical and easy process for improving the efficiency of para-isomer selectivity.
The present disclosure relates to a silanated metallosilicate catalyst used for selective conversion of hydrocarbon to para-disubstituted isomers, through removal of non-framework Group IIIA elements or other elements isomorphously substituted for the Group IIIA elements, present in the metallosilicate and on the metallosilicate. The present disclosure further relates to a process for preparing the silanated metallosilicates for selectivation of metallosilicate through deposition of silica, resulting in significant improvement in selectivity for para-disubstituted isomer in the process of disproportion (Trans alkylation) of mono-alkyl aromatics or alkylation of mono-alkyl aromatics to di-alkyl aromatics using alkene or alkanol as alkylating agents.
The major cause for low improvement in para-isomer selectivity is identified to be related to the ineffective silanation of the metallosilicate composite extrudates, which is attributed to the presence of non-framework Group IIIA elements such as octahedral aluminium species or other elements which are isomorphously substituted for Group IIIA elements such as gallium, iron and chromium and the like present in the parent metallosilicates or metallosilicate composite extrudates.
The present disclosure provides a simple process for the removal of such octahedral species of non-framework Group IIIA elements or any other octahedral species coming from other elements isomorphously substituted for Group IIIA elements. In an embodiment, the non-framework species from the metallosilicates are removed, thereby improving the efficiency towards silanation to obtain high para- isomer selectivity in reactions concerning alkylation of mono-alkyl aromatics to para-di-alkyl aromatics.
Typically, silanation procedure is adopted in case of metallosilicates, to deposit a thin layer of silica on the surface of metallosilicates to increase diffusivity difference among para and other (ortho and meta) isomers, and thus enhance the para-isomer product selectivity in alkylation and the disproportionation reaction of mono-alkyl aromatics.
The process of the present disclosure comprises a pretreatment process of the impure metallosilicates, thus improving the catalytic performance in terms of enhanced efficacy of silanation, thereby providing a smooth and hassle-free operation leading to the production of metallosilicates that meet all the desired performance criteria.
In one aspect, the present disclosure provides a silanated metallosilicate catalyst, which is substantially free of non-framework group IIIA elements or other elements isomorphously substituted for the group IIIA elements. The silanated metallosilicates of the present disclosure can be used for conversion of hydrocarbon to at least 99 % para-di-substituted aromatic compound. The non-framework group IIIA elements can be at least one selected from the group consisting of octahedral aluminium (Al) and octahedral gallium (Ga) or other elements isomorphously substituted for group IIIA elements can be at least one selected from the group consisting of octahedral iron (Fe), octahedral chromium (Cr), and the like.
The para-di-substituted aromatics can be at least one selected from the group consisting of para-diethyl benzene, para-xylene, para-ethyl toluene, para-cymene, and para-di-isopropyl benzene.
It is surprisingly found that once these kinds of non-framework group IIIA elements or other elements isomorphously substituted for group IIIA elements, are removed, the selectivity for para-isomer through a silanation procedure (selectivation process), is enhanced significantly.

In another aspect, the present disclosure provides a process for preparing the silanated metallosilicates having improved efficiency. The process comprises treatment of metallosilicates with an acid at a temperature in the range of 20 oC to 100 oC for a time period in the range of 0.5 hour to 20 hours to obtain treated metallosilicates.

The ratio (w/w) of the metallosilicate to the acid solution can be in the range of 1:1 to 1:20. In an embodiment, the ratio of the metallosilicate to the acid solution is 1:5 wt/wt (1 part metallosilicate and 5 part of acid solution).

The treated metallosilicates are washed with water followed by heating/drying to obtain the metallosilicates that are substantially free of non-framework group IIIA elements or other elements isomorphously substituted for the Group IIIA elements. The treated metallosilicates (prior to silanation) enhance the efficiency towards selectivation, and thus provide an easy process to obtain highly selective metallosilicates, useful for para-isomer selective reactions.
The metallosilicate can be at least one selected from the group of pentasil and mordenite family. Typically, the pentasil family of the metallosilicate is at least one selected from the group consisting of Ga-ZSM-5, Fe-ZSM-5, B-ZSM-5, Al-ZSM-5, Ga-Al-ZSM-5, Fe-Al-ZSM-5, and B-Al-ZSM-5. Typically, the metallosilicate is selected from Al-ZSM-5 or Ga-Al-ZSM-5 or a mixture thereof.
The silica to alumina weight ratio in the metallosilicate can be in the range of 20 to 600. In an embodiment, the silica to alumina weight ratio is 185.
The metallosilicate contains non-frame work Group IIIA elements or other elements isomorphously substituted for the Group IIIA element, which are located in non-conformational manner or in non-framework manner. The content of the non-conformational elements in the metallosilicate can be in the range from 0.1 to 20 wt % as measured from the peak area in the Magic Angle Spinning Nuclear Magnetic Resonance (MAS-NMR) spectra of the metallosilicate. In an embodiment, the non-conformational elements /octahedral species content in the metallosilicate are 1.6 wt%.
In accordance with the present disclosure, the acid can be at least one selected from the group consisting of mono-basic or poly-basic inorganic or organic acids. Typically, the acid is at least one selected from the group consisting of nitric acid, nitrous acid, hydrochloric acid, sulphuric acid, sulphurous acid, persulphuric acid, phosphoric acid, carbonic acid, formic acid, acetic acid, propionic acid, oxalic acid, tartaric acid, and benzoic acid. In one embodiment, the acid is nitric acid.
The concentration of the acid used in the process can be in the range of 0.1 to 20 % w/v. In one embodiment, the concentration of acid used in the process is 2 % w/v (i.e., 2 part of pure acid by wt., was diluted to 100 ml with water).
The ratio of liquid to solid in terms of volume to weight can be in the range of 50:1 to 1:1. The liquid refers to the aqueous solution of the selected acid in water as described hereinbefore (0.1 to 20% w/v). The solid refers to the metallosilicate containing the debris i.e. untreated metallosilicates or metallosilicate having impurities as described hereinbefore or the composite extrudes of the metallosilicate.
The metallosilicate is treated with the acid solution at a temperature in the range of 20 oC to 100 °C for a time period in the range of 0.5 hour to 20 hours. In one embodiment, the metallosilicate is treated 2%w/v nitric acid solution at 90 °C for 3 hours to obtain treated metallosilicate.
The so obtained treated metallosilicate is washed with water and dried at a temperature in the range of 100 oC to 150 oC for a time period in the range of 8 hours to 15 hours to obtain a metallosilicate, which is substantially free of non-framework Group IIIA elements or other elements isomorphously substituted for the Group IIIA elements. In one embodiment, the so obtained treated metallosilicate is washed with 500 ml water and dried at 120 oC for 12 hours to obtain a metallosilicate catalyst, which is substantially free of non-framework Group IIIA elements or other elements isomorphously substituted for the Group IIIA elements. Typically, the treated metallosilicate is washed with water once. Since the acid concentration used in the process of the present disclosure is low, washing with water once, is sufficient to remove the adhered acid on the metallosilicate composite.
In accordance with the present disclosure, the metallosilicate can be in powder form or composite form during the acid treatment. The composite form of metallosilicate can be with a binder. The binder used in the present disclosure can be selected from alumina, silica, clay and any mixture thereof. The amount of the binder can be in the range of 10 to 90 wt. % with respect to the total composite. In one embodiment, the metallosilicate composite has a zeolite to silica (binder) ratio of 65:35.
The acid treated metallosilicates, substantially free of non-framework Group IIIA elements or other elements isomorphously substituted for the Group IIIA elements, are further repeatedly selectivated by multiple silanation treatments with a solution of an organosilicon compound. In one embodiment, the selectivation treatment with the organosilicon compound can be carried out by soaking the acid treated metallosilicate in the organosilicon compound solution for a predetermined time to obtain a mixture. The solution of the organosilicon compound can be prepared by mixing organosilicon compound in a mixture of fluid media. The fluid medium can be selected from the group consisting of aromatic hydrocarbons such as benzene, toluene, and xylenes and paraffinic hydrocarbons having carbon number C4 – C8 and alcohols having carbon number C1 - C6 or any combinations thereof. In one embodiment, the fluid media is a mixture of toluene and methanol.
The organosilicon compound can be at least one selected from water soluble organo-silicon compound and hydrocarbon soluble organosilicon compound. Typically, the water soluble organosilicon compound is aminoalkyltrialkoxy silane, preferably 3-aminopropyl triethoxysilane. The hydrocarbon soluble organosilicon compound can be tetra-alkoxysilane, preferably tetra-ethoxysilane (tetra-ethoxysilicate-TEOS).
From the so obtained mixture, the fluid medium can be removed to obtain a mass. The mass can be dried by heating the mass to a temperature in the range of 70 oC to 150 oC in the presence of a moist atmosphere or in a humid atmosphere for a time period in the range of 10 hours to 40 hours to obtain a dried mass. In the process of the present disclosure, during drying of the mass, the presence of humid atmosphere (or moist air) is needed to hydrolyze the organosilicon compound deposited on metallosilicate in the previous step. Desired percentage of moisture to carry out the process is the air saturated with moisture at that operating temperature. (Higher the moisture available better is the efficiency of the step). However, typically drying of the mass is carried out at about 90-95% relative humidity, i.e., 90-95% moisture content with respect to that required for saturation at that temperature.
The dried mass can be calcined at a temperature in the range of 400 oC to 600 oC in the presence of air for a time period in the range of 4 hours to 10 hours to obtain a silanation compound I. The silanation compound I is selectivated for 2-10 times, preferably 2-8 times by a procedure similar to that described hereinabove.
The acid-treated and repeatedly selectivated metallosilicates exhibits superior selectivity for para-isomer in alkylation or disproportionation reactions of mono-alkyl aromatics, under conditions sufficient to effect the conversions.
The mono-alkyl aromatics can be selected from mono-aromatic compound containing substituents having carbon number in the range of 1 to 4, e.g. toluene, ethyl benzene, propyl benzene, isopropyl benzene, butyl benzene and its isomers, or any commercial hydrocarbon stream rich in mono-alkyl aromatics. Typically, the mono-alkyl aromatic is a hydrocarbon stream containing 50 to 90% ethyl benzene. In one embodiment, the mono-alkyl aromatic is monoalkyl benzene.
The mono-alkyl aromatics, and an alkene or alkanol or alkylating agent, is contacted with the acid-treated and repeatedly selectivated metallosilicate, at a temperature in the range of 100 °C to 500 °C at a pressure in the range of 0.1 to 100 bar, and weight hourly space velocity in the range of 0.1 to 50 h-1 to produce di-alkyl aromatics with more than 99.5% selectivity for the para-isomer among the di-alkyl ortho and meta isomers. The mole ratio of mono-alkyl aromatics to alkene or alkanol as the alkylating agent can be in the range of 0.2 to 50 and the mole ratio of hydrogen to hydrocarbon can be in the range of 0.5 to 25. The mole ratio of hydrogen to hydrocarbon is calculated by the formula: (moles of H2)/ (total moles of hydrocarbons in feed). In the present disclosure, the hydrogen can be from carrier gas; and hydrocarbon can be from mixed xylene solvent stream and ethanol. In one embodiment, the alkene is ethylene, alkanol is ethanol, and the di-alkyl aromatic is para-diethyl benzene.
The process described in the present disclosure has many advantages over known processes, such as comparatively high yield, mild operating conditions, easy to control conditions, and environment friendly.
The present disclosure is further described in light of the following experiments which are set forth for illustration purpose only and not to be construed for limiting the scope of the disclosure. These laboratory scale experiments can be scaled up to industrial/commercial scale and the results obtained can be extrapolated to industrial/commercial scale.

EXPERIMENTAL DETAILS:
Performance test:
The performance of the zeolite extrudates in terms of di-ethylbenzene (DEB) yield and para-diethylbenzene selectivity was evaluated in an all glass integrated down-flow atmospheric pressure reactor by a known method as disclosed in the US patent No.7, 709,692 which is incorporated herein by reference.
Ethyl benzene rich mixed xylene solvent (MXS) stream and ethanol were used as feed. The composition of MXS was 0.94% toluene, 73.78% ethylbenzene, 24.32% total xylenes, 0.37% cumene, and 0.59% higher aromatics. Hydrogen gas was employed as carrier gas. The performance test reactions were carried out at a temperature of 330 °C, whsv of 3 h-1 having MXS to ethanol mole ratio of 8 and hydrogen to hydrocarbon mole ratio of 2. Products of the reaction were analyzed by gas-chromatography following standard analytical method referred as UOP 744 method. UOP 744 method is used for determining the individual C6 aromatics through C10 aromatics in petroleum distillates or aromatic concentrates by gas chromatography technique. The yield of diethyl benzene (DEB yield) and the para-isomer selectivity among the diethyl benzene isomers (PDEB isomer selectivity), were defined as performance criteria.
EXAMPLE I- Comparative example-
Experiment 1
A ZSM-5 zeolite having silica to alumina ratio of 185, and 1.6 % of the total aluminium present as octahedral aluminium (as measured from the peak area in the analysis of state of aluminium by 27Al MAS-NMR spectroscopy), was composited and shaped in the form of 1.5 mm cylindrical extrudates with a zeolite to silica (binder) ratio of 65:35. The final extrudates contained proton form of the zeolite.

Experiment 2
50 g of the ZSM-5 extrudates from experiment 1 were soaked in a solution of 16.3 g of tetraethyl orthosilicate (TEOS), for 6 h. The solution of 16.3 g of tetraethyl orthosilicate (TEOS) was prepared in a mixture of 50 ml toluene and 30 ml methanol. Thereafter, the solvent mixture was slowly distilled out and the extrudates were treated in an air oven at 120 °C in 95% relative humidity for 24 hours. The so obtained dried extrudates were calcined at 540 oC for 6 h. After calcination the compound was labeled as Silanation compound I.
The silanation compound I was tested for performance as described in the performance test. Results are included in table 1.
Experiment 3
40 g of Silanation compound I obtained in Experiment 2 was treated for second selectivation step in the same manner as explained in Experiment 2 using 40 ml toluene, 24 ml methanol, and 13 g of TEOS. Thereafter, the solvent mixture was slowly distilled out and the extrudates were treated in an air oven at 120 °C in 95% relative humidity for 24 hours. The so obtained dried extrudates were calcined at 540 oC for 6 h. After calcination the compound was labeled as a Silanation compound II.
The silanation compound II was tested for performance as described in the performance test. Results are included in table 1.
Experiment 4
30 g of Silanation compound II obtained in Experiment 3 was treated for third selectivation step in the same manner as explained in Experiment 2 using 30 ml toluene, 18 ml methanol, and 6.7 g of TEOS. Thereafter, the solvent mixture was slowly distilled out and the extrudates were treated in an air oven at 120 °C in 95% relative humidity for 24 hours. The so obtained dried extrudates were calcined at 540 oC for 6 h. After calcination the compound was labeled as a silanation compound III.
The silanation compound III was tested for performance as described in the performance test. Results are included in table 1.
Experiment 5
20 g of Silanation compound III obtained in Experiment 4 was treated for fourth selectivation step in the same manner as explained in Experiment 2 using 20 ml toluene, 12 ml methanol, and 1.9 g of TEOS. Thereafter, the solvent mixture was slowly distilled out and the extrudates were treated in an air oven at 120 °C in 95% relative humidity for 24 hours. The so obtained dried extrudates were calcined at 540 oC for 6 h. After calcination, the compound was labeled as Silanation compound IV. The so obtained Silanation compound IV was tested for performance as described. Results are included in table 1.
Table 1: Performance of fresh and selectivated ZSM-5 extrudates
Experiments
Samples
Performance Criteria
DEB Yield PDEB Isomer Selectivity
Experiment 1 Metallosilicate (ZSM-5) without acid treatment and without silanation 11.2 wt% 47.8 %
Experiment 2 Silanation compound I 8.7 wt% 63.6 %
Experiment 3 Silanation compound II 7.4 wt% 74.8 %
Experiment 4 Silanation compound III 6.3 wt% 84.6 %
Experiment 5 Silanation compound IV 4.5 wt% 96.3 %

From the results of Table 1, it is evident that PDEB isomer selectivity is increased after multiple silanation. However, the improvement in selectivity for Silanation compounds I, II, III, and IV are comparatively low, since the selectivity has not reached the targeted value of >97% while DEB yield dropped to < 5 wt%.
EXAMPLE II- Improved efficiency of the Metallosilicate in accordance with the present disclosure:
Experiment 6: 100 g of the zeolite extrudates were prepared as described in experiment 1 and added to 1000 ml of 2% w/v of nitric acid solution. The mixture was treated at 90 °C for three hours. After 3 hours, the nitric acid solution was decanted and the acid treated extrudates were then washed with 500 ml of water, and dried overnight at 120 °C. Dried extrudates were calcined at 540 °C for 6 h.
Performance results of these acid treated extrudates were checked and are tabulated in table 2.
Experiments 7-10:
Multiple selectivated silanation of the acid treated extrudates were carried out in a manner similar to the experiments as given in Experiments 2-5 with the same quantities of extrudates, TEOS, toluene, and methanol as described in Experiments 2-5. Selectivations were carried out to prepare samples of Silanation compound V, Silanation compound VI, Silanation compound VII, and Silanation compound VIII.
The performance of the samples was checked in the same manner as described above. The results are shown in Table 2.
Table 2: Performances of the acid treated and selectivated ZSM-5 extrudates
Experiments Samples
Performance Criteria
DEB Yield PDEB Isomer
Selectivity
Experiment 6 Acid treated metallosilicate (ZSM-5) without silanation 11.7 wt% 45.5 %
Experiment 7 Silanation compound V 10.8 wt% 79.1 %
Experiment 8 Silanation compound VI 8.1 wt% 94.7 %
Experiment 9 Silanation compound VII 7.8 wt% 99.1 %
Experiment 10 Silanation compound VIII 7.5 wt% 99.7 %

From Table 1 and Table 2, it is evident that PDEB (para-diethyl benzene) isomer selectivity is increased, when the zeolite is pretreated with an acid solution followed by multiple silanation as compared to when the zeolite is only subjected to the multiple silanation and no pretreatment with acid. It is noted that increment in the para-isomer selectivity in each of the multiple silanation steps, with the treated metallosilicate is more than that in case of untreated metallosilicate. It is also observed that because of improved efficiency of silanation in case of the treated metallosilicate composite, the total amount of TEOS needed per gram to achieve >99.5% para-isomer selectivity, is much less as compared to untreated metallosilicate.
Experiment 11
Performance test for Silanation compound VIII
15 g of catalyst sample, Silanation compound VIII (as described hereinbefore), was tested for performance under continuous operation mode. The test conditions were: temperature 335 oC, pressure 4 Kg.cm-1, whsv 4 h-1, H2/hydrocarbons mole ratio 2, MXS/ethylene mole ratio 8. The DEB yield and PDEB selectivity were 8.15 wt% and 99.75 %, respectively at 50th hour-on-stream. This run was continued upto 120 hrs. The DEB yield and PDEB selectivity remained almost same (8.1 wt% and 99.75%) after 120th hour-on-stream. The catalyst deactivation was not observed up to 120 hour-on-stream.

TECHNICAL ADVANCEMENTS
The present disclosure described herein above has several technical advantages including, but not limited to, the realization of,
• improved silanated metallosilicates;
• improved silanated metallosilicates that enhances the selectivity of para-disubstituted aromatics from hydrocarbons;
• a process that selectively improves the efficiency of silanation;
• a process that is simple and easy; and
• a process that facilitates removal of impurities from the metallosilicates.
Throughout this specification the word “comprise”, or variations such as “comprises” or “comprising”, will be understood to imply the inclusion of a stated element, integer or step, or group of elements, integers or steps, but not the exclusion of any other element, integer or step, or group of elements, integers or steps.
The use of the expression “at least” or “at least one” suggests the use of one or more elements or ingredients or quantities, as the use may be in the embodiment of the invention to achieve one or more of the desired objects or results. While certain embodiments of the inventions have been described, these embodiments have been presented by way of example only, and are not intended to limit the scope of the inventions. Variations or modifications to the formulation of this invention, within the scope of the invention, may occur to those skilled in the art upon reviewing the disclosure herein. Such variations or modifications are well within the spirit of this invention.
The numerical values given for various physical parameters, dimensions, and quantities are only approximate values and it is envisaged that the values higher than the numerical value assigned to the physical parameters, dimensions and quantities fall within the scope of the invention unless there is a statement in the specification to the contrary.
While considerable emphasis has been placed herein on the specific features of the preferred embodiment, it will be appreciated that many additional features can be added and that many changes can be made in the preferred embodiment without departing from the principles of the disclosure. These and other changes in the preferred embodiment of the disclosure will be apparent to those skilled in the art from the disclosure herein, whereby it is to be distinctly understood that the foregoing descriptive matter is to be interpreted merely as illustrative of the disclosure and not as a limitation. ,CLAIMS:1. A silanated metallosilicate catalyst which is substantially free of non-framework group IIIA elements or other elements isomorphously substituted for group IIIA elements.

2. The silanated metallosilicate catalyst as claimed in claim 1, wherein said non-framework group IIIA element is octahedral aluminium or said other elements isomorphously substituted for the group IIIA element is at least one selected from the group consisting of gallium, iron, and chromium.

3. The silanated metallosilicate catalyst as claimed in claim 1 or claim 2 are used for conversion of hydrocarbon to at least 99 % para-di-substituted aromatic compounds.
4. A process for preparing the silanated metallosilicate catalyst as claimed in claim 1, wherein said process comprises the following steps:
a. treating at least one metallosilicate with an acid solution at a temperature in the range of 20 oC to 100 oC to obtain a treated metallosilicate;
b. washing said treated metallosilicate with water, followed by heating to obtain a treated metallosilicate which is substantially free of non-framework group IIIA elements or other elements isomorphously substituted for the group IIIA elements;
c. soaking said treated metallosilicate substantially free of said non-framework group IIIA elements or said other elements isomorphously substituted for the group IIIA elements obtained in step (b) in a solution of organosilicon compound to obtain a mixture, wherein the solution of organosilicon compound is prepared in a fluid media;
d. removing said fluid media from said mixture to obtain a mass and heating said mass to a temperature in the range of 100 oC to 150 oC in the presence of moist air for a time period in the range of 10 hours to 40 hours to obtain a dried mass;
e. calcining said dried mass at a temperature in the range of 400 oC to 600 oC for a time period in the range of 4 hours to 8 hours to obtain a silanation compound I; and
f. iterating the steps c) to e) at least 2 times for multiple silanation to obtain the silanated metallosilicate catalyst, which is substantially free of said non-framework group IIIA elements or said other elements isomorphously substituted for the group IIIA elements.

5. The process as claimed in claim 4, wherein said metallosilicate is at least one selected from pentasil family and mordenite family.

6. The process as claimed in claim 4 or claim 5, wherein said metallosilicate is at least one selected from the group consisting of Ga-ZSM-5, Fe-ZSM-5, B-ZSM-5, Al-ZSM-5, Ga-Al-ZSM-5, Fe-Al-ZSM-5, B-Al-ZSM-5, Cr-ZSM-5 and Cr-Al-ZSM-5.

7. The process as claimed in claim 4 to claim 6, wherein said metallosilicate is at least one of Al-ZSM-5, and Ga-Al-ZSM-5.
8. The process as claimed in claim 4, wherein said acid is at least one selected from the group consisting of nitric acid, nitrous acid, hydrochloric acid, sulphuric acid, sulphurous acid, persulphuric acid, phosphoric acid, carbonic acid, formic acid, acetic acid, propionic acid, oxalic acid, tartaric acid, and benzoic acid.
9. The process as claimed in claim 4 or claim 8, wherein the concentration of said acid is in the range of 0.1 to 20% w/v.
10. The process as claimed in claim 4, wherein the ratio of said metallosilicate to said acid solution is in the range of 1:1 to 1:20.
11. The process as claimed in claim 4, wherein said fluid media is a mixture of methanol and toluene.

12. The process as claimed in claim 4, wherein said organosilicon compound is at least one of tetra-alkoxy silane and functionalized alkoxy silane.

13. The process as claimed in claim 12, wherein said organosilicon compound is tetraethoxy silane.

14. A process for improving the selectivity of di-substituted aromatics, said process comprising contacting said silanated metallosilicate as claimed in claim 1 with at least one alkyl aromatic compound and at least one alkylating agent selected from the group consisting of alkene and alkanol, at a temperature in the range of 100 oC to 500 oC at a pressure in the range of 0.1 bar to 100 bar and weight hourly space velocity in the range of 0.1 to 50 h-1 to obtain disubstituted alkyl aromatic compound having para-isomer selectivity of at least 99%.

15. The process as claimed in claim 14, wherein said alkyl aromatic compound is a monoaromatic compound containing a substituent having carbon number in the range of 1 to 4.

16. The process as claimed in claim 14 or claim 15, wherein said alkyl aromatic is at least one selected from the group consisting of toluene, ethyl benzene, propyl benzene, isopropyl benzene, and butyl benzene.

17. The process as claimed in claim 14, wherein said alkene is selected from the group consisting of ethylene, propylene, and butylene; and said alkanol is selected from the group consisting of ethanol, n-propanol, iso-propanol and butanol.

18. The process as claimed in claim 14, wherein the mole ratio of said alkyl aromatics to said alkylating agent is in the range of 0.2 to 50.