Claims:We Claim:
A method of preparing zeolite intergrowth material comprising steps of:
preparing synthesis gel of at least one zeolite 1,
adding at least one zeolite 2 in the synthesis gel of the at least one zeolite 1,
crystallizing gel obtained in step b) to obtain crystallized material,
separating and optionally drying the crystallized material to obtain the zeolite intergrowth material,
wherein the at least one zeolite 1 and the at least one zeolite 2 are different and have at least one common secondary building unit.
The method as claimed in claim 1, wherein the at least one zeolite 2 is added to the synthesis gel of the at least one zeolite 1 after aging of the synthesis gel for about 1 h to 48 h, preferably about 15 h to 30 h.
The method as claimed in claim 1, wherein the crystallisation is carried out by hydrothermal treatment at a temperature ranging from about 70°C to 100°C for time period ranging from about 2 h to 20 h.
The method as claimed in claim 1, wherein the separating is carried out by technique selected from group comprising centrifugation and filtration, or any combination thereof; and wherein the drying is carried out at temperature ranging from about 70°C to 150°C, for about 2 h to 10 h.
A zeolite intergrowth material comprising two or more zeolites coexisting in a single crystal, wherein the zeolites have at least one common secondary building unit.
The method as claimed in claim 1, wherein the at least one zeolite 1 is at an amount ranging from about 10 w/w% to 95 w/w%; and wherein the at least one zeolite 2 is at an amount ranging from about 5 w/w% to 90 w/w%.
The method as claimed in claim 1 or the zeolite intergrowth material as claimed in claim 5, wherein the zeolite 1 and zeolite 2 of claim 1 or the two or more zeolites of claim 5 are selected from a group comprising faujasite (FAU) framework, Linde Type A (LTA) framework, Mordenite framework (MOR) and MFI framework type zeolite or any combinations thereof
The method as claimed in claim 1 or the zeolite intergrowth material as claimed in claim 5, wherein the zeolite 1 and zeolite 2 of claim 1 or the two or more zeolites of claim 5 are selected from a group comprising zeolite X, zeolite Y, zeolite A, modernite and ZSM-5 or any combination thereof.
The method or the zeolite intergrowth material as claimed in claim 8, wherein the zeolite intergrowth material is a combination of zeolite X and zeolite Y; zeolite X and zeolite A; zeolite Y and zeolite A; zeolite X, zeoliteY, and zeolite A; or modernite and ZSM-5.
Use of the zeolite intergrowth material as claimed in any of the preceding claims for industrial application.
The use as claimed in claim 10, wherein the application is selected from a group comprising catalysis, alkylation, adsorption and separation.
A composition comprising the zeolite intergrowth material of any of the preceding claims optionally along with excipient.
A method of preparing a composition comprising steps of contacting the zeolite intermediate material of any of the preceding claims with excipient and mixing to form a homogeneous mixture.
The method as claimed in claim 13, wherein the method comprises:
forming an extrudable paste of the homogenous mixture,
subjecting the paste to drying and calcining to form extrudate, and
optionally crushing the extrudate.
The composition as claimed in claim 12 or the method as claimed in claim 13, wherein the excipient is selected from a group comprising binder and extruding agent or any combination thereof.
The composition as claimed in claim 12 or the method as claimed in claim 15, wherein the binder is selected from group comprising Attapulgite, Kaolin, Bentonite, alumina and silica or any combinations thereof; and wherein the extruding agent is selected from group comprising carboxy methyl cellulose, starch and polyvinyl alcohol or any combinations thereof.
The method as claimed in claim 14, wherein the drying is at temperature ranging from about 70 to 100°C, the calcining is at temperature ranging from about 500 to 700°C, and wherein the extrudates are crushed and optionally sieved to a size of about 300 to 1000 micron.
The composition as claimed in claim 12 or the method as claimed in claim 13 or claim 14, wherein the composition is ion exchanged with alkali ion or alkaline earth cation or combination thereof and optionally dried at temperature ranging from about 70 to 450°C.
The composition or the method as claimed in claim 18, wherein the alkali ion is potassium, and wherein the alkaline earth cation is barium.
The composition or the method as claimed in claim 18, wherein the ion exchange is carried out with about 50 to 60 % alkali ion exchange and about 40 to 50 % alkaline earth cation exchange.
A method for selective adsorption of a component from a mixture, said method comprising step of contacting the composition as claimed in claim 15 with a mixture comprising the component, for adsorption of the component.
The method as claimed in claim 21, wherein the component is selected from a group comprising p-xylene.

Dated this 5th day of April, 2019

SHIVAKUMAR R.
IN/PA-1301
Of K&S Partners
To: Agent for the Applicant
The Controller of Patents,
The Patent Office, at: Mumbai , Description:TECHNICAL FIELD
The present disclosure relates to the fields of material science and separation science. In particular, the present disclosure relates to zeolite intergrowth materials, compositions, methods of preparation and applications thereof.

BACKGROUND
Zeolites have tremendous scientific and industrial importance due to their unique textural properties and shape selectivity, which is useful in many catalytic and adsorption processes involved in modern chemical and oil-refining industries. Variety of zeolites are being commercially produced and extensively used in many processes. Several efforts are made to develop new zeolites or modification of existing zeolites to tune textural properties to enhance its performance and increase profit. Various molecular modelling studies are carried out to identify required properties of zeolite for particular process. Based on this, combination of zeolites is also being used to get desired properties.
Use of physical mixture of zeolites to get different pore dimensions and to achieve desired properties is known, but synthetic mixture of two or more zeolites are very few. Co-existence of two or more phases of zeolite in highly basic/acidic solution is very difficult.
Further, combination of zeolites for formation of membrane structure or core-shell structure are known in the art. Membrane/core-shell zeolites involve layering/coating respectively for two different zeolites. However, such zeolites are expensive and have limited accessibility to the zeolite in the core.
While prior art provides for few zeolite intergrowth system and their applications, such methods are expensive, time consuming and require additional components such as structure directing agents or templates comprising organic compounds. Thus, there is a need for providing efficient means, methods for producing the same and applications thereof.

SUMMARY OF THE DISCLOSURE
The present disclosure relates to a method of preparing zeolite intergrowth material comprising steps of:
preparing synthesis gel of at least one zeolite 1,
adding at least one zeolite 2 in the synthesis gel of the at least one zeolite 1,
crystallizing gel obtained in step b) to obtain crystallized material,
separating and optionally drying the crystallized material to obtain the zeolite intergrowth material,
wherein the at least one zeolite 1 and the at least one zeolite 2 are different and have at least one common secondary building unit.
The present disclosure also relates to a zeolite intergrowth material comprising two or more zeolites coexisting in a single crystal, wherein the zeolites have at least one common secondary building unit.
The present disclosure further relates to use of the zeolite intergrowth material for industrial application including but not limiting to catalysis, alkylation, adsorption and separation.
Furthermore, the present disclosure relates to a composition comprising the zeolite intergrowth material optionally along with excipient.
The present disclosure also relates to a method of preparing a composition comprising steps of contacting the zeolite intermediate material with excipient and mixing to form a homogeneous mixture.
The present disclosure relates to an absorbent comprising the zeolite intergrowth material.
In an embodiment of the present disclosure, the method of preparing the composition comprises steps of:
contacting the zeolite intermediate material with excipient and mixing to form a homogeneous mixture,
forming an extrudable paste of the homogenous mixture,
subjecting the paste to drying and calcining to form extrudate, optionally crushing the extrudate, to obtain the composition;
optionally subjecting said composition to ion exchange with alkali ion or alkaline earth cation or combination thereof and optionally drying.
In an embodiment, the ion exchange is carried out with about 50 to 60 % alkali ion exchange and about 40 to 50 % alkaline earth cation exchange.
Th present disclosure also relates to a method for selective adsorption of a component from a mixture, said method comprising step of contacting the composition of the present disclosure with a mixture comprising the component, for adsorption of the component.
Th present disclosure also relates to a method for selective adsorption of p-xylene from a mixture, said method comprising step of contacting the composition of the present disclosure with a mixture comprising the component, for adsorption of the p-xylene.

BRIEF DESCRIPTION OF ACCOMPANYING FIGURESf
In order that the disclosure may be readily understood and put into practical effect, reference will now be made to exemplary embodiments as illustrated with reference to the accompanying figures. The figures together with detailed description below, are incorporated in and form part of the specification, and serve to further illustrate the embodiments and explain various principles and advantages, in accordance with the present disclosure where:
Figure 1 depicts XRD pattern of zeolite X-Y intergrowth.
Figure 2 depicts Si NMR of pure zeolite X.
Figure 3 depicts 29Si NMR of pure zeolite Y.
Figure 4 depicts 29Si NMR of physical mixture of zeolite X & Y (1:1).
Figure 5 depicts 29Si NMR of X-Y intergrowth material.
Figure 6 depicts CO2 adsorption isotherm of zeolite X, zeolite Y, physical mixture of zeolites X and Y and zeolite X-Y intergrowth material.
Figure 7 depicts XRD pattern of zeolite A – zeolite Y.
Figure 8 depicts XRD pattern of mordenite-Y.
Figure 9 depicts schematic diagram of experimental set-up for conducting adsorption breakthrough experiment.
Figure 10 depicts adsorption and desorption curves of conventional adsorbent comprising zeolite X and potassium exchange for 4 times and barium exchange for 4 times.
Figure 11 depicts adsorption and desorption curves of adsorbent containing hierarchical zeolite 05:95, potassium exchanged for 4 times and barium exchanged once.
Figure 12 depicts adsorption and desorption curves of adsorbent containing hierarchical zeolite 10:90, potassium exchanged for 4 times and barium exchanged once.
Figure 13 depicts adsorption and desorption curves of adsorbent containing hierarchical zeolite 20:80, potassium exchanged for 4 times and barium exchanged once.

DETAILED DESCRIPTION
As used herein, the terms ‘method’ and ‘process’ are used interchangeably.
As used herein, the terms ‘zeolite intergrowth material’, ‘hierarchical zeolites’ and ‘hierarchical zeolite materials’ of the present invention are used interchangeably in reference to zeolites comprising two or more types of pores or frameworks in one crystal. The hierarchical zeolites comprise two or more zeolites coexisting in a single crystal, wherein the zeolites have at least one common secondary building unit. The said hierarchical zeolites are porous, exhibit molecular sieving ability, fast mass transport and possess secondary porosity at meso- and macroscale.
As used herein, the term ‘common building unit’ refers to common/same ‘primary building block’ and/or ‘secondary building block’ between two or more zeolites.
As used herein, the terms ‘primary building block(s)’, ‘primary building unit(s)’ and ‘PBU’ are used interchangeably. The primary building units (PBU) of zeolites are tetrahedra of silicon and aluminum i.e. [SiO4]4- and/or [AlO4]5-.
As used herein, the terms ‘secondary building block(s)’, ‘secondary building unit(s)’ and ‘SBU’ are used interchangeably. Secondary building units (SBU) are polyhedras that are assembled from PBUs in different forms such as cubes, hexagonal prisms, octahedra, and truncated octahedra. The silicon and aluminum atoms, located at the corners of the polyhedra, are joined by a shared oxygen. The final zeolite structure consists of assemblages of the secondary units in a regular three-dimensional crystalline framework.
As used herein the terms “primary zeolite” and “zeolite 1” are used interchangeably in reference to the zeolite(s) to which the seed zeolite is added for the synthesis of the zeolite intergrowth material.
As used herein the terms “zeolite seed” and “zeolite 2” are used interchangeably in reference to the zeolite(s) employed in the synthesis of the zeolite intergrowth material to accelerate the rate of crystallization. The zeolite seed employed during synthesis has common secondary building unit with the zeolite 1 of the synthesis mixture, to provide ready availability of nuclei of same zeolite and enables faster growth of desired framework post crystallization.
In an embodiment, addition of seed of same zeolite in synthesis gel is known to enhance the rate of crystallization in the art. However, the present disclosure provides for addition of seed of a zeolite (zeolite 2) in gel of different zeolite (zeolite 1) for intergrowth of zeolite 1 and 2. This step is carefully optimized for coexistence of different zeolites in a single crystal.
The present disclosure relates to zeolite intergrowth materials, method of preparing and applications thereof.
The present disclosure relates to a method of preparing zeolite intergrowth material comprising steps of:
preparing synthesis gel of at least one zeolite 1,
adding at least one zeolite 2 in the synthesis gel of the at least one zeolite 1,
crystallizing gel obtained in step b) to obtain crystallized material,
separating and optionally drying the crystallized material to obtain the zeolite intergrowth material,
wherein the at least one zeolite 1 and the at least one zeolite 2 are different and have at least one common building unit. The said common building unit is at least one secondary building unit.
In embodiments of the present disclosure, the at least one zeolite 1 is at an amount ranging from about 10 w/w% to about 95 w/w%.
In embodiments of the present disclosure, the at least one zeolite 2 is at an amount ranging from about 5 w/w% to about 90 w/w%.
In embodiments of the present disclosure, the at least one zeolite 2 is added to the synthesis gel of the at least one zeolite 1 after aging of the synthesis gel for about 1 h to 48 h, preferably about 15 h to 30 h.
In embodiments of the present disclosure, the crystallisation is carried out by hydrothermal treatment at a temperature ranging from about 70°C to 100°C for time period ranging from about 2 h to 20 h.
In embodiments of the present disclosure, the separating in the method of preparing zeolite intergrowth material is carried out by technique selected from group comprising centrifugation and filtration, or any combination thereof.
In embodiments of the present disclosure, the drying in the method of preparing zeolite intergrowth material is carried out at temperature ranging from about 70°C to about 150°C, for about 2 h to about 10 h.
In embodiments of the present disclosure, the zeolite 1 and zeolite 2 are selected from a group comprising faujasite (FAU) framework, Linde Type A (LTA) framework, Mordenite framework (MOR) and MFI framework type zeolite or any combinations thereof.
In embodiments of the present disclosure, the zeolite 1 and zeolite 2 are selected from a group comprising zeolite X, zeolite Y, zeolite A, modernite and ZSM-5 or any combination thereof.
In exemplary embodiments of the present disclosure, the zeolite intergrowth material is a combination of zeolite X and zeoliteY; zeolite X and zeolite A; zeolite Y and zeolite A; zeolite X, zeoliteY, and zeolite A; or modernite and ZSM-5.
The present disclosure also relates to a zeolite intergrowth material obtained by the method of preparing zeolite intergrowth material as per the present disclosure.
The present disclosure also relates to a zeolite intergrowth material comprising two or more zeolites coexisting in a single crystal, wherein the zeolites have at least one common secondary building unit.
In an embodiment of the present disclosure, the two or more zeolites in the zeolite intergrowth material are selected from a group comprising faujasite (FAU) framework, Linde Type A (LTA) framework, Mordenite framework (MOR) and MFI framework type zeolite or any combinations thereof.
In an embodiment of the present disclosure, the two or more zeolites in the zeolite intergrowth material are selected from a group comprising zeolite X, zeolite Y, zeolite A, modernite and ZSM-5 or any combination thereof.
In an embodiment of the present disclosure, the zeolite intergrowth material is a combination of zeolite X and zeoliteY; zeolite X and zeolite A; zeolite Y and zeolite A; zeolite X, zeoliteY, and zeolite A; or modernite and ZSM-5.
The present disclosure also relates to the use/application of the zeolite intergrowth material of the present disclosure such as but not limiting to its use in industrial application.
In embodiments of the present disclosure, the zeolite intergrowth material of the present disclosure has application in catalysis, alkylation, adsorption and/or separation, etc.
The present disclosure also relates to a composition comprising the zeolite intergrowth material of the present disclosure optionally along with excipient.
In an embodiment of the present disclosure, the excipient in the composition is selected from a group comprising binder and extruding agent or any combination thereof.
In an embodiment of the present disclosure, the binder is selected from group comprising Attapulgite, Kaolin, Bentonite, alumina and silica.
In an embodiment of the present disclosure, the extruding agent is selected from group comprising carboxy methyl cellulose, starch and polyvinyl alcohol.
In an embodiment of the present disclosure, the composition is ion exchanged with alkali ion or alkaline earth cation or combination thereof. In an embodiment of the present disclosure, the alkali ion is potassium, and wherein the alkaline earth cation is barium.
The present disclosure also relates to a method of preparing a composition comprising steps of contacting the zeolite intermediate material of the present disclosure with excipient and mixing to form a homogeneous mixture.
In an embodiment of the present disclosure, the aforedescribed method of the present disclosure further comprises acts of:
forming an extrudable paste of the homogenous mixture,
subjecting the paste to extrusion followed by drying and calcination to form extrudate, and
optionally crushing the extrudates to get desired size of particle (about 300- 1000 micron).
In embodiments of the present disclosure, the excipient is selected from a group comprising binder and extruding agent or any combination thereof.
In embodiments of the present disclosure, the binder is selected from group comprising Attapulgite, Kaolin, Bentonite, alumina and silica or any combinations thereof.
In embodiments of the present disclosure, the extruding agent is selected from group comprising carboxy methyl cellulose, starch and polyvinyl alcohol or any combinations thereof.
In embodiments of the present disclosure, the drying in the method of the present disclosure is at temperature ranging from about 70 to 100°C, the calcining is at temperature ranging from about 500 – 700°C, and wherein the extrudates are crushed and optionally sieved to a size of about 300 - 1000 micron.
In an embodiment, the method of the present disclosure the composition is subjected to ion exchange with alkali ion or alkaline earth cation or combination thereof and optionally dried at temperature ranging from about 70 to about 450°C.
In an embodiment of the present disclosure, the alkali ion is potassium and/or the alkaline earth cation is barium.
In another embodiment of the present disclosure, the ion exchange is carried out with about 50 to 60 % alkali ion exchange and about 40 to 50 % alkaline earth cation exchange.
The present disclosure also relates to a method for selective adsorption of a component such as but not limiting to -xylene, C3 and CO2 etc from a mixture, said method comprising step of contacting the composition of the present disclosure with a mixture comprising the component, for adsorption of the component.
The present disclosure relates to method of preparing hierarchical zeolite materials comprising synthetic mixture of two or more zeolites.
In all embodiments of the present disclosure, the two or more zeolites involved in intergrowth material have at least one common SBU.
In embodiments of the present disclosure, the structural requirement to get the zeolite intergrowth material is that the two or more zeolites involved in intergrowth material should have at least one common SBU. Synthesis with two or more zeolite with common SBU results in dissolution or disappearance of one phase of zeolite and results in presence of only dominant phase of zeolite as product.
In embodiments of the present disclosure, the present disclosure provides for synthesis/ preparation of intergrowth material using one/more zeolite as a seed on which one/more zeolite is allowed to grow. Thus, in the preparation of zeolite intergrowth material of two or more zeolites, one zeolite is added as a seed (zeolite 2) on which other zeolite(s) (zeolite 1) will be grown. Selection of zeolites is such that at least one common secondary building block from zeolite framework should be present. Due to presence of common building block of framework, seeded material does not get completely dissolved in alkaline gel of the other zeolite(s). On the other hand, seeded material does not interfere in the growth of other zeolite and favours its growth because of ready availability of SBU required for complete crystallization. In an embodiment, depending on the application, zeolites can be chosen to get desired properties.
In an embodiment, the present disclosure provides for zeolite intergrowth of various combinations based on their common building blocks of the framework. This approach enables to tune the textural properties of zeolites to get better performance of zeolite-based catalyst in different reactions. This is also beneficial for selecting adsorbent with different pore dimensions depending on requirement of suitable separation process. In an embodiment, development of such hierarchical materials will be advantageous for various applications such as industrial and chemical reactions including but not limiting to para xylene separation, CO2 capture, C3 separation, zeolite-based alkylation reactions, etc.
In an embodiment, the method of preparing hierarchical zeolite material comprises selection of zeolites with at least one common SBU among them and adding one zeolite as a seed on which other zeolite will be grown. Selection of zeolites will be such that at least one common secondary building block from zeolite framework should be present. Presence of common SBU favors intergrowth or coexistence of two or more zeolites within one crystal. This approach enables to tune the textural properties of the material for better performance in different applications such as an adsorbent, catalyst, etc.
In an embodiment, the method of preparing hierarchical zeolite material comprises selection of zeolites with at least one common SBU among them and adding one zeolite as a seed on which other zeolite will be grown, followed by hydrothermal treatment/crystallisation. Here, one zeolite grows on a seeded zeolite(s) and forms a crystal with hierarchical structural properties.
In an embodiment, the method of preparing hierarchical zeolite material comprises adding one or more zeolites as seed/seeds in the synthesis gel comprising other zeolite(s) prior to crystallisation.
In an exemplary embodiment, zeolite X is added as seed in the synthesis gel of zeolite Y prior to crystallization by techniques such as hydrothermal treatment. Hence, zeolite Y is grown on seeds of zeolite X and forming a crystal with hierarchical structural properties. The zeolite intergrowth of zeolite X and zeolite Y is highly efficient for selective adsorption of p-xylene from its isomers.
In an embodiment, the method of preparing zeolite intergrowth material comprising steps of:
preparing synthesis gel of at least one zeolite 1,
adding at least one zeolite 2 in the synthesis gel of the at least one zeolite 1,
crystallizing gel obtained in step b) to obtain crystallized material,
separating and optionally drying the crystallized material to obtain the zeolite intergrowth material,
wherein the at least one zeolite 1 and the at least one zeolite 2 are different and have at least one common secondary building unit.
In an embodiment, the method of preparing zeolite intermediate material comprises:
preparing a typical zeolite 1 synthesis gel in accordance to standard recipes provided by the International zeolite association (IZA),
adding zeolite 2 seeds to the zeolite 1 synthesis gel preferably after aging of the synthesis gel for about 1 h to 48 h, more preferably after 15 to 30 h, most preferably after completion of desired aging time of 24 h;
crystallizing the resultant gel at about 70°C to 100°C, more preferably at about 90°C till complete crystallization of the material;
filtering and optionally drying the crystals of the zeolite intermediate material obtained;
optionally characterising the crystals by different techniques such as but not limited to XRD, Solid state NMR, CO2 adsorption.
In embodiments of the present disclosure, preparation of synthesis gel of zeolite 1 is carried out as per the protocol set forth by the International Zeolite Association (IZA).
In an embodiment of the present disclosure, preparation of synthesis gel of zeolite 1 wherein the zeolite 1 is selected from a group comprising zeolite X, zeolite Y, zeolite A, modernite or zeolite ZSM-5, is carried out as per the protocol set forth by the International Zeolite Association (IZA).
In an embodiment, the source material for the preparation of synthesis gel of zeolite X as zeolite 1 comprises distilled water, sodium hydroxide (99+% NaOH), alumina trihydrate (Merck, 65% Al2O3)c, and sodium silicate solution (27.35% SiO2, 8.30% Na2O, 1.37 g/mL).
In an embodiment, the source material for the preparation of synthesis gel of zeolite X as zeolite 1 comprises deionized water, sodium aluminate solid (Strem Chemicalb 1.27 Na/Al, 6.1% H2O), sodium hydroxide pellets (J. T.Baker, 99% NaOH), and sodium silicate solution (PQ Corp, N Brand, 28.7 wt% SiO2, 8.9 wt% Na2O)c.
In an embodiment, the source material for the preparation of synthesis gel of zeolite X as zeolite 1 comprises deionized water, sodium hydroxide (Fisher Scientific, 99+% NaOH), sodium aluminate (Fisher Scientific, NaO2: Al2O3: 3 H2O)b and sodium metasilicate (Fisher Scientific, Na2SiO3: 5 H2O).
In embodiments of the present disclosure, the term ‘aging’ in zeolite synthesis is related to aging period before the hydrothermal crystallization. This aging is usually performed at room temperature. It can help to orient the crystallisation toward the desired structure (favor the growth of the desired phase over an undesired one), decrease the crystallisation time or favor the formation of smaller particles (favor nucleation over growth).
In embodiments of the present disclosure, the crystallisation is carried out by hydrothermal treatment. In another embodiment of the present disclosure, the crystallisation is carried out at a temperature ranging from about 70°C to 100°C preferably at about 90°C for time period ranging from about 2 h to 20 h preferably for about 4 h.
In embodiments of the present disclosure, the drying is carried out at temperature ranging from about 70°C to about 150°C, preferably about 90°C, for about 2 h to about 10 h, preferably 4 h.
In embodiments of the present disclosure, the addition of seed zeolite(s)/zeolite 2 is at an amount ranging from 5 w/w% to 90 w/w%, and the other zeolite (zeolite 1) is at an amount ranging from 10 w/w% to 95 w/w%, with respect to the total amount of zeolite, to get various compositions of intergrowth materials.
In an exemplary embodiment, the structure of the novel zeolite intergrowth materials prepared as per the present disclosure is analysed by techniques such as but not limiting to XRD and solid state NMR.
All combinations of zeolites with common SBU can be synthesized in accordance to the method of the present disclosure, to obtain zeolite intergrowth material which shows intergrowth and/or coexistence of both the zeolites in the same crystal.
Co-existence of two or more phases of zeolite during hydrothermal synthesis of zeolite in highly basic/acidic solution is very difficult. However, the present disclosure provides for hierarchical or intergrowth zeolites comprising two or more zeolites in same zeolite crystal.
The present disclosure also provides for zeolite intergrowth material which contains two or more zeolites in which their individual properties are present in a single crystal. Different acid sites, pore dimensions and pore volumes of each zeolite can be present in the single crystal of the hierarchical intergrowth material. This enables to tune the properties of the material as per catalyst or adsorbent requirement for suitable applications.
In an embodiment, the approach of selecting zeolites having at least one common secondary building block of framework is suitable for hierarchical material for zeolite based catalytic and separation processes.
In an exemplary embodiment, the zeolites are selected from zeolite structural group comprising but not limiting to Faujasite framework (FAU), Linde Type A framework (LTA), ZSM-FIve (MFI) framework and Mordenite framework (MOR) or any combination thereof.
In an exemplary embodiment, the FAU framework zeolites comprise zeolite X and zeolite Y, the LTA framework zeolite comprises zeolite A, the MFI framework zeolite comprises ZSM and the MOR framework zeolite comprises modernite.
In an exemplary embodiment, the present disclosure provides for zeolite intergrowth material such as but not limiting to Zeolite X-Zeolite Y, Zeolite Y-Zeolite A, Zeolite X-Zeolite A, Zeolite X- Zeolite Y-Zeolite A, modernite-ZSM-5 etc.
In embodiments of the present disclosure, the zeolite intergrowth material is Zeolite X-Zeolite Y.
In embodiments of the present disclosure, the zeolite intergrowth material is Zeolite Y-Zeolite A.
In embodiments of the present disclosure, the zeolite intergrowth material is Zeolite X-Zeolite A.
In embodiments of the present disclosure, the zeolite intergrowth material is Zeolite X- Zeolite Y-Zeolite A.
In embodiments of the present disclosure, the zeolite intergrowth material is modernite-ZSM-5. ZSM-5 belongs to framework MFI, however it has MOR as one of the SBU.
Zeolite intergrowth material or co-existence of zeolites are not seen in absence of common secondary building blocks of frameworks. For instance, co-existence of both zeolite phases is not observed when ZSM-5/zeolite-Y and Zeolite-Y/Mordenite are employed, since they do not have any common SBU to allow formation of zeolite intergrowth material.
The present disclosure also provides for a methodology to tune the textural properties of zeolite by using appropriate ratio of zeolites. In embodiments of the present disclosure, the ratio of seed zeolite(s)/zeolite 2 with that of zeolite 1 is ranging from 5:95 to about 90:10, preferably about 5:40, and more preferably about 10:20.
The present disclosure also relates to the method of using the zeolite intergrowth material for various industrial and chemical applications. In an exemplary embodiment, the zeolite intergrowth material is used in selective adsorption of p-xylene.
In an embodiment, the present disclosure provides for method of synthesizing hierarchical zeolite materials to achieve desired textural properties for different applications. Synthesis of hierarchical zeolites with different acid sites and pore dimension has potential to replace existing zeolites and increase the profit margin. Synthesis of zeolite intergrowth material as per the present disclosure is an approach to obtain new hierarchical materials for suitable application.
In an embodiment, the zeolite intergrowth materials of the present disclosure have higher adsorption capacity and selectivity.
The present disclosure also relates to a composition comprising the zeolite intergrowth material optionally along with excipient.
In embodiments of the present disclosure, the excipient in the composition of the present disclosure is selected from group comprising but not limiting to binder, extruding agent, and/or any industrially acceptable excipient(s). In an embodiment, the binder is present at an amount ranging from about 5 – 30 wt%. In another embodiment, the extruding agent is present at an amount ranging from about 0 – 4 wt%.
In an exemplary embodiment, the binder in the composition of the present disclosure is selected from group comprising Attapulgite, Kaolin, Bentonite, alumina and silica or any combination thereof; and the extruding agent is selected from group comprising carboxy methyl cellulose, starch and polyvinyl alcohol or any combination thereof.
In an embodiment, the composition of the present invention is an adsorbent or a catalyst.
In an embodiment, the composition is ion exchanged with alkali ion or alkaline earth cation or combination thereof. In an embodiment, the alkali ion is potassium, and the alkaline earth cation is barium.
In an embodiment, the zeolite intergrowth material or the composition comprising the same have enhanced adsorption, selectivity and capacity for separation of industrially important chemicals.
The present disclosure also relates to the use of the zeolite intergrowth material or the composition comprising the zeolite intergrowth material of the present disclosure for application in industrial and/or chemical reactions. In an exemplary embodiment, the reaction is selected from a group comprising catalysis, alkylation, adsorption and separation.
The present disclosure also relates to an adsorbent comprising the zeolite intermediate material of the present invention, and a method of preparation thereof.
In an embodiment, the adsorbent of the present disclosure has enhanced adsorption, selectivity and capacity for separation of industrially important chemicals.
In an embodiment, the present disclosure relates to a method of preparing an adsorbent composition comprising steps of:
contacting zeolite intermediate material of the present invention with excipients such as but not limiting to binder and extruding agent or a combination thereof, and optionally mixing to form a homogeneous mixture,
adding water to the mixture to form a paste,
subjecting the paste to extrusion followed by drying and calcination,
optionally crushing the extrudate,
conducting ion exchange on extrudate, and
drying the extrudate thus obtained to obtain the adsorbent.
Adsorbents must have a high physical strength. In embodiments of the present disclosure, the adsorbent comprises binder, extruding agent and/or any industrially acceptable excipient(s). In an embodiment, the binder in the adsorbent must maintain a high macro-porosity, which does not increase the diffusion resistance. In an embodiment, extruding agent is needed to form extrudable dough. This agent will burn off during calcination of adsorbent. However, after burning it leaves behind macro pores in adsorbent, that further helps in reducing diffusional resistance during application. In embodiments of the present disclosure, the binder is selected from group comprising Attapulgite, Kaolin, Bentonite, alumina and silica or any combination thereof; and the extruding agent is selected from group comprising carboxy methyl cellulose, Starch and polyvinyl alcohol or any combination thereof. In an exemplary and non-limiting embodiment, the binder used in the preparing the adsorbent is attapulgite and the extruding agent is carboxy methyl cellulose. In an embodiment, the binder is present at an amount ranging from about 5–30 wt% in adsorbent. In another embodiment, the extruding agent is present at an amount ranging from about 0 – 4 wt%.
In an exemplary and non-limiting embodiment for preparing the adsorbent, the extrudates are dried prior to calcination at temperature ranging from about 70-100°C.
In an exemplary and non-limiting embodiment for preparing the adsorbent, the extrudates are calcined at temperature ranging from about 500°C to about 700°C, preferably about 600°C for about 5 h to about 7 h, preferably about 6 h.
In an exemplary and non-limiting embodiment for preparing the adsorbent, the extrudates are crushed and sieved to a size of about 300 - 1000 micron.
In an exemplary embodiment for preparation of the composition or adsorbent, the ion exchange is conducted using alkali ion such as but not limiting to potassium, or alkaline earth cation such as but not limiting to barium, or combinations thereof. In an embodiment, the potassium exchange is done by contacting the composition or the adsorbent with potassium chloride solution and refluxing; the liquid to solid ratio was maintained to be about 3:1 to 20:1. In another embodiment, the barium exchange is done by contacting the composition or the adsorbent with barium chloride solution and refluxing; the liquid to solid ratio was maintained to be about 3:1 to about 20:1. In an embodiment, the adsorbent is dried post ion exchange at temperature ranging from about 70°C to about 100°C, preferably 90°C for 1 to about 8 h, and optionally further dried at temperature ranging from about 200 to about 450°C, preferably about 350-400°C for about 4 - 6 h.
In an exemplary embodiment of the present disclosure, the intergrowth material was exchanged 4 times with potassium ion and 1 time with barium ion.
In an exemplary embodiment of the present disclosure, the intergrowth material was exchanged with about 50-60 % potassium and 50-40% barium ions. The % mentioned is with respect to the total number of extra-framework cations present in the adsorbent/intergrowth material.
The present disclosure relates to a method for preparation of adsorbent comprising zeolite intergrowth material comprising steps such as mixing, kneading, extrusion, calcination, cation exchange.
In an embodiment, the method for preparation of adsorbent comprises using zeolite XY intergrowth material using optimum amount of alkali and/or alkaline earth ion exchange.
In an embodiment, the method of preparation of the adsorbent of the present invention comprises steps of:
mixing zeolite intermediate material, binder and extruding agent to form a homogeneous mixture,
extrudable paste of this homogenous mixture was made by adding an appropriate amount of distilled water,
the extrudates are dried at ambient temperature for 2 h and subsequently at 70°C overnight, and thereafter calcined at temperature 500 – 700°C preferably 600°C for 6 h,
the extrudates are further crushed and sieved to size of about 300 - 1000 micron,
potassium exchange is done by contacting adsorbent and KCl solution (10% w/w of solution) by refluxing at 90°C for 8 h. Liquid to Solid ratio was maintained to be 3:1-20:1,
barium exchange is done by contacting adsorbent and barium chloride solution (10% w/w of solution) by refluxing at 90°C for 8 h. Liquid to solid ratio was maintained to be 3:1-20:1, and
drying the adsorbent at 70-90°C overnight in oven and then at 350-400°C for 4 - 6 h.
In an embodiment, the adsorbent is prepared using zeolite intermediate material prepared using 5 w/w%-90 w/w% seeding of zeolite.
In an exemplary embodiment, the extrudates are made by hand extruder.
In an exemplary embodiment, the method of preparing the adsorbent comprises mixing the intergrowth faujasite zeolite, inorganic binder and extruding agent; followed by extrusion, calcination at temperature ranging from about 500 - 700°C, and exchange of extra framework cations with potassium and barium. In an embodiment, the inorganic binder used for forming adsorbent is selected from a group comprising attapulgite, Kaolin, Bentonite, alumina and silica or any combination thereof. In an embodiment, the extruding agent is selected from group comprising carboxy methyl cellulose, starch and polyvinyl alcohol or any combination thereof.
In an embodiment, the adsorbent comprises the zeolite intergrowth material such as but not limiting to hierarchical faujasite zeolite, as primary adsorbing material. In an exemplary embodiment, the hierarchical faujasite zeolite contains zeolite Y and zeolite X in the same zeolite crystal.
In an embodiment, the adsorbent of the present disclosure comprises the afore-described zeolite intergrowth material, binder such as inorganic binder and extruding agent.
In an exemplary embodiment, the adsorbents are evaluated with respect to adsorption capacity and/or selectivity by techniques such as adsorption equilibrium experiment and adsorption breakthrough test.
In an exemplary embodiment, the adsorbents are evaluated with respect to adsorption capacity and selectivity of p-xylene over other C8-aromatic isomers by techniques such as 1) adsorption equilibrium experiment at 20°C, and 2) adsorption breakthrough test in a fixed bed at plant operating conditions 180°C and 9 kg/cm2G.
In embodiments of the present disclosure, the composition/adsorbent of the present disclosure is subjected to ion exchange with about 50 to 60 % potassium exchange and about 40 to 50 % barium exchange for selective adsorption of p-xylene.
The composition/adsorbent of the present disclosure is commercially cost effective, has longer life and higher catalytic activity, adsorption selectivity and capacity. In an exemplary embodiment, the composition/adsorbent of the present disclosure has higher p-xylene adsorption selectivity and capacity.
The present disclosure also relates to a method for selective adsorption of a component from a mixture, said method comprising step of contacting the composition/adsorbent comprising the zeolite intergrowth material of the present disclosure with a mixture comprising the component, and separating / isolating the component from the composition/adsorbent. In an embodiment, the component is selected from a group comprising p-xylene, C3 and CO2.
The present disclosure also relates to method of using an adsorbent comprising the zeolite intergrowth material such as but not limiting to hierarchical faujasite zeolite, for separating p-xylene from C8 aromatic isomers/stream.
The present disclosure also relates to a method for selective adsorption of p-xylene from its isomers, said method comprises step of contacting the adsorbent of the present disclosure with a mixture comprising p-xylene.
In an embodiment, the method for isolating p-xylene from its isomers comprises step of contacting the adsorbent of the present disclosure with a solution comprising p-xylene (PX) (optionally along with m-xylene (MX), o-xylene (OX), ethylbenzene (EB) etc. or combinations thereof) in non-adsorbing solvent(s) for about 6 to about 30 h, preferably about 24 h at temperature ranging from about 10 to about 30°C, preferably about 20°C, and separating p-xylene from the adsorbent to obtain the separated p-xylene.
In a preferred embodiment, the adsorbent comprises hierarchical zeolite structure with enhanced adsorption selectivity and capacity for separation of p-xylene from mixture of C8 aromatic isomers.
p-xylene (PX) is widely used in the production of purified terephthalic acid (PTA), which is an important chemical in the production of polyethylene terephthalate (PET). The separation of C8 aromatic isomers to recover p-xylene of high level purity (>99.5 wt%) is of great commercial importance in the petrochemicals industries as p-xylene is used as raw material for the production of polyethylene terephthalate (PET) used for polyester fibers, molded plastics, films and blown beverage bottles. C8 isomers such as xylene mixtures, ethyl benzene (EB) etc. are very difficult to separate using the conventional method of distillation because they have close boiling points (136-142°C), and have similar physicochemical properties.
p-xylene is industrially separated from mixture of C8 aromatic isomers (p-xylene, m-xylene, o-xylene and ethylbenzene) by crystallization or selective adsorption technique. Fractional crystallization based processes exploits the large freezing point difference between p-xylene and the remaining components in the mixture. PX has higher freezing point (13°C) than that of other isomers (OX -25°C, MX -48°C, and EB -95°C), which make it easy to separate by cooling down to a certain temperature is reached, just above the eutectic point where is still possible to separate PX without precipitation of the other isomers. In fractional crystallization, PX is separated as solid and other isomers remain in filtrate. At all temperatures above the eutectic point, PX is still soluble in the remaining C8 aromatics. This fact limits the efficiency of crystallization processes to a PX recovery of 60-65% for feed streams with about 20 wt % of p-xylene. This limitation is one of the main drawbacks of crystallization when processing feeds with a low concentration of p-xylene.
In selective adsorption technique, feed mixture is contacted with adsorbent in fixed bed/ simulated moving bed (SMB) to adsorb p-xylene, which is subsequently desorbed with appropriate desorbent. Conventional adsorbent has at least 90% of the exchangeable cationic sites of the zeolite occupied with barium ions. However, the adsorbent comprising hierarchical zeolite of the present disclosure provides for enhanced p-xylene selectivity and adsorption capacity from mixture of C8 aromatic isomers, with less Ba exchange.
In an embodiment, the adsorbent comprising hierarchical zeolite has better p-xylene selectivity and adsorption capacity than counterparts of conventional adsorbent comprising zeolite X. Higher PX selectivity and adsorption capacity of the adsorbent of the present disclosure compared to conventional adsorbent, leads to better recovery of p-xylene from C8 aromatic stream, less use of decreased amount of desorbent, requirement of smaller quantity of adsorbent or increased throughput.
In an exemplary embodiment, the adsorbent comprises hierarchical faujasite zeolite structure with enhanced adsorption selectivity and capacity for separation of p-xylene from mixture of C8 aromatic isomers. In a non-limiting embodiment, the hierarchical faujasite zeolite structure is zeolite X-zeolite Y.
In an exemplary embodiment of the present disclsoure, the desorbent is p-diethylbenzene (PDEB), toluene or any other suitable desorbent known to a person skilled in the art.
In an embodiment, the Zeolite of the present disclosure selectively allows entery of PX into the micropores and hence, selectively adsorbs it. Zeolite in Na-form has low selectivity of PX; therefore, selectivity of PX is typically increased by ion-exchange with alkaline earth exchange cations such as Barium. Adsorbent typically has at least 90% of the exchangeable cationic sites of the zeolite occupied with barium ions along and rest with other cations like Na, K etc. However, the hierarchical faujisite zeolites of the present invention have better selectivity with intergrowth material at less than 90% barium exchange, and preferably about 40-50% lesser barium exchange.
In an embodiment, the zeolite intergrowth material zeolite X-zeolite Y has at least 10 – 20% higher total C8 aromatics adsorbed, and at least 40-50% higher selectivity of p-xylene over m-xylene.
In a preferred embodiment, the composition or adsorbent comprising the zeolite X-zeolite Y intergrowth material is subjected to about 50 to 60 % potassium exchange and 40 to 50 % barium exchange for selective adsorption of p-xylene.
In embodiments of the present disclosure, ambient temperature ranges from about 20°C to about 40°C.
Additional embodiments and features of the present disclosure will be apparent to one of ordinary skill in art based upon the description provided. The embodiments provide various features and advantageous details thereof in the description. Descriptions of well-known/conventional methods and techniques are omitted so as to not unnecessarily obscure the embodiments. The examples provided herein are intended merely to facilitate an understanding of ways in which the embodiments provided may be practiced and to further enable those of skill in the art to practice the embodiments provided. Accordingly, the following examples should not be construed as limiting the scope of the embodiments.

EXAMPLES:
Example 1(a): Synthesis of hierarchical zeolite comprising Zeolite X – Zeolite Y
Zeolite X and zeolite Y belong to fuajasite (FAU) type zeolite and have common PBU and SBU. For synthesis of intergrowth material of zeolite X and zeolite Y, zeolite Y synthesis gel was prepared in accordance to the standard recipe as per International zeolite association (IZA). Zeolite X seeds are added in the zeolite Y synthesis gel, after completion of aging time of 24 h. Resultant gel was subjected to crystallization by hydrothermal treatment at 90oC till complete crystallization of the material. This was followed by filtration at room temperature by centrifugation at 8000 rpm for 10 min followed by decanting supernatant. The filtered and dried material was characterized by different techniques. Composition of zeolite X-Y intergrowth material was varied by changing amount of seeded material (zeolite X) from 5% to 90% w/w (table 1).

Table 1:
Intermediate Zeolite X-Y (ratio w/w%) Amount of
Zeolite X
(g) Amount of
Zeolite Y
(g)
XY (5:95) 5 95
XY (10:90) 10 90
XY (20:80) 20 80
XY (30:70) 30 70
XY (40:60) 40 60
XY (50:50) 50 50
XY (60:40) 60 40
XY (70:30) 70 30
XY (80:20) 80 20
XY (90:10) 90 10

Example 1(b): X-ray powder diffraction (XRD) technique
Intermediate Zeolite XY obtained by employing 20% seed of zeolite X and 80% zeolite Y was analysed using XRD technique using standard method. Since both zeolite X and zeolite Y has FAU framework, their XRD patterns are similar. However small difference was observed in their 2 Theta values. Their peak position i.e. the 2 Theta value is a function of Si/Al ratio of zeolite. Si/Al ratio of zeolite X is 1.2 and that of zeolite Y is 2.5. Higher 2 Theta values observed with increasing Si/Al ratio. XRD pattern of as prepared material (Figure 1) showed doublets of every peak indicating presence of both zeolite X and Y in the material.

Example 1(c): Solid state Nuclear Magnetic Resonance spectroscopy (NMR)
Solid state 29Si NMR as per standard method was also used to study X-Y intergrowth material. In this, solid state NMR of pure zeolite X and zeolite Y were taken followed by physical mixture of zeolite X and zeolite Y (1:1) ratio. 5 peaks were observed in the NMR spectrum of zeolite X (Figure 2) based on number of Al atoms in the vicinity of Si atom. Most intense peak is of Si(4Al) followed by decrease in intensity with the function of reduction in number of Al atoms. NMR spectrum of zeolite Y (Figure 3) was found to be different in the intensity pattern compared to zeolite X. Peaks of Si(2Al) and Si(1Al) are comparatively more intense than other peak. These spectra show significant difference in terms of zeolite X and Y which will be helpful to study intergrowth of zeolite X-Y.
It is important to check pattern of NMR spectrum of physical mixture of zeolite X and Y with similar composition as intergrowth material prior to analysing that of X-Y intergrowth material. Figure 4 shows NMR spectrum of physical mixture of zeolite X and Y (1:1). In this spectrum peaks of Si(4Al) and Si(2Al) are most intense. NMR spectrum of zeolite X-Y intergrowth (20% zeolite X and 80% zeolite Y) showed completely different pattern in terms of intensity of peaks compared to their physical mixture. Intensity of peak implies density of corresponding Si atoms. Different pattern of intensity of peaks of zeolite X-Y intergrowth than physical mixture, pure X and pure Y shows structural difference in X-Y intergrowth material. This is very strongly evidenced formation of X-Y intergrowth.

Example 1(d): CO2 adsorption
Zeolite X-Y intergrowth material was also tested for CO2 adsorption as per standard method and compared with that of zeolite X and zeolite Y. Figure 6(a) shows CO2 adsorption isotherm of zeolite X, zeolite Y, physical mixture of zeolites X and Y and zeolite XY intergrowth material (20% zeolite X and 80% zeolite Y). It was seen that adsorption capacity of X-Y intergrowth material is significantly improved than that of pure zeolite X and pure zeolite Y. This also indicated the structural difference in X-Y intergrowth material which enhances sorption capacity of the material.

Example 2: Zeolite A – Zeolite Y
Intergrowth of zeolite A and zeolite Y was also prepared using similar method as example 1(a). Here, zeolite A was used as a seed in the synthesis gel of zeolite Y followed by hydrothermal treatment for crystallization. Obtained material was characterized by XRD (as per the protocol of example 1(b). The XRD pattern is illustrated in figure 7, which clearly shows existence of both zeolite A and zeolite Y in the intergrowth material.

Example 3: Mordenite – Zeolite Y
Mordenite zeolite has building unit mor, however the building unit in zeolite Y is d6r and sod. An attempt was made to synthesise intergrowth material of mordenite and zeolite Y in which mordenite was added as a seed in the synthesis gel of zeolite Y. The experimental conditions employed were same as Example 1(a). Resultant material was characterized by XRD, as per the protocol of Example 1(b). It has observed from the XRD pattern (Figure 8), that only mordenite phase was seen, however no evidence of zeolite Y was found. Since there is no common PBU/SBU between mordenite and zeolite Y, coexistence of both phases are not seen.
Above examples support the approach of preparing zeolite intergrowth material. Example 1(a) shows zeolite intergrowth of zeolite X-Y. In this system both zeolite X and zeolite Y have all common building blocks (d6r, sod). In Example 2, d6r is a common building block between zeolite A and zeolite Y, which favours the formation of zeolite A-Y intergrowth material. On the contrary, mordenite and zeolite Y do not have any common building block and hence no evidence of coexistence of both the phases in the resultant material.

Example 4: Zeolites X and Y – Zeolite A
Intergrowth of zeolites X, Y and A is also prepared using similar method as example 1(a). Here, zeolite X as well as zeolite Y is used as a seed in the synthesis gel of zeolite A followed by hydrothermal treatment for crystallization. Obtained material was characterized by XRD, as per the protocol of example 1(b).

Example 5: Preparation of adsorbent
75 g of hierarchical faujasite zeolite obtained from Example 1(a), 25 g of attapulgite as binder, 3 g carboxy methyl cellulose (CMC) as extruding agent were mixed together to form a homogeneous mixture. Extrudable paste of this homogenous mixture was made by adding an appropriate amount of distilled water. Extrudates were made by hand extruder with 1 mm diameter aperture, which were then dried in an oven at ambient temperature for 2 h and subsequently at 70°C overnight. Extrudates were calcined in a furnace at temperature of 600°C for 6 h. Extrudates were further crushed and sieved to size of about 300 - 1000 micron. Potassium exchange was done by contacting adsorbent and KCl solution (10% w/w of solution) by refluxing at 90°C for 8 h. Liquid to solid ratio was maintained to be -5:1. Barium exchange was done by contacting adsorbent and barium chloride solution (10% w/w of solution) by refluxing at 90°C for 8 h. Liquid to solid ratio was maintained to be 5:1. Adsorbent was dried at 70°C overnight in oven and then at 400°C for about 4 - 6 h. Adsorbents were prepared using hierarchical faujasite zeolite prepared using 5 w/w%, 10 w/w% and 20 w/w% seeding of zeolite X.

Example 6:
Example 6(a): Adsorption equilibrium experiments
Adsorbent (0.5 - 0.6 g) prepared in accordance to Example 5 was contacted with a solution (1.5 – 1.6 g) of p-xylene (PX), m-xylene (MX), o-xylene (OX) and ethylbenzene (EB) (about 10 wt% each) in non-adsorbing solvent n-nonane for 24 h at 20°C in water bath. Initial and final concentrations of p-xylene (PX), m-xylene (MX), o-xylene (OX) and ethylbenzene (EB) were measured by gas chromatography. Amount of p-xylene (PX), m-xylene (MX), o-xylene (OX) and ethylbenzene (EB) adsorbed on adsorbent were calculated by solving following linear equations:
M_f C_(pX,f)+ q_(pX,f) M_ads= M_i C_(pX,i)
M_f C_(mX,f)+ q_(mX,f) M_ads= M_i C_(mX,i)
M_f C_(oX,f)+ q_(oX,f) M_ads= M_i C_(oX,i)
M_f C_(EB,f)+ q_(EB,f) M_ads= M_i C_(EB,i)
(1/M_ads ) M_f+ q_(pX,f)+q_(mX,f) + q_(oX,f)+q_(EB,f) =M_i/M_ads
where, Mi and Mf are initial (before adsorption) and final (after adsorption) mass of solution, respectively. CpX,i, and CmX,i, CoX,i, and CEB,i are initial (before adsorption) concentration (mass fraction) of PX, MX, OX and EB in the solution, respectively. CpX,f, CmX,f, CoX,f and CEB,f are final (after adsorption) concentration (mass fraction) of PX, MX, OX and EB in the solution, respectively. Mads is mass of adsorbent. qpX,f, qmX,f, qoX,f and qEB,f are adsorbed phase concentrations of PX, MX, OX and EB, respectively at adsorption equilibrium.
Total C8 aromatics adsorption capacity of the adsorbent and adsorption selectivity of p-xylene are calculated by following equations,
q_total=q_(pX,f)+q_(mX,f)+q_(oX,f)+q_(EB,f)
a_(pX/mX)=(q_(pX,f)/C_(pX,f) )/(q_(mX,f)/C_(mX,f) )

Example 5(b): Evaluation of adsorbents by Adsorption equilibrium experiments at 20°C
Adsorbent based intergrowth zeolite materials were evaluated by adsorption equilibrium experiment at 20°C. Results of evaluation by adsorption equilibrium experiments at 20°C are summarized in table 2. Adsorbent was prepared using hierarchical material 10: 90 (10% seeding of zeolite X). Adsorbent was exchanged with different levels of potassium and barium and further evaluated by adsorption equilibrium experiments. Adsorbent comprising zeolite X alone (Adsorbent X), Adsorbent comprising zeolite Y alone (Adsorbent Y) and Adsorbent comprising physical mixtures (PM) of zeolitesX and Y (Adsorbent PM-XY) at 10:90 wt% were used as control. The results are tabulated in Table 2 below. The zeolite intergrowth of zeolite X and zeolite Y is highly efficient for selective adsorption of p-xylene from its isomers.

Table 2: Results of evaluation by adsorption equilibrium experiments at 20°C
Adsorbent qtotal, wt% ?PX/MX ?PX/OX ?PX/EB
Adsorbent X, Before ion exchange 17 1.05 0.66 1
Adsorbent Y, Before ion exchange 19.3 0.36 0.96 2.0
Adsorbent PM-XY (10:90), Before ion exchange 19 0.47 0.9 1.8
Adsorbent XY (10:90) Before Ion Exchange 19.0 0.55 0.76 1.54
Adsorbent PM-XY (10:90), After ion exchange 4K-1Ba 16.5 2.1 2.2 2.1
Adsorbent XY (10:90), 4K 17.1 3.63 2.88 1.14
Adsorbent XY (10:90), 2K and 1 Ba 17.8 3.2 3.1 2.3
Adsorbent XY (10:90), 3K and 1 Ba 17.9 4.2 3.5 1.3
Adsorbent XY (10:90), 4K and 1 Ba 16.1 4.5 4.7 2.5
Adsorbent using zeolite Y, 4K and 1 Ba 17.1 2.0 2.1 2.0
Adsorbent using zeolite X, 4K and 1 Ba 14 2.6 2.6 2.1

Example 6: Adsorption breakthrough experiment
Schematic diagram of experimental set up for performing adsorption breakthrough experiment is shown in figure 9. Valves V1 and V2 are three way valves, and V3 is a needle valve. All valves are of 1/8” size. Valve V1 is provided to choose fluid amongst desorbent and feed solution for pumping through adsorbent bed. Valve V2 can be used to flush or priming pumping line (HPLC pump). All solutions at inlet are maintained under inert (N2) atmosphere. Packed bed has inside diameter of 1 cm and bed height of 50 cm. Bed volume from particle support plate to top of the packed bed was 40 mL. Packed bed, preheater and connecting lines were insulated to minimize heat loss to surroundings.
Fresh adsorbent was heated at 350°C for 3 h and charged in adsorber. It was activated under Nitrogen atmosphere at 1 kg/cm2G pressure and 250°C (heating rate 10°C/min) for 1 hr. After cooling adsorbent to 30°C, flow of desorbent was started. Desorbent was p-diethylbenzene (PDEB). Once liquid reached at the outlet, temperature of preheater and packed bed were set to 180°C and heating started. Pressure at back pressure regulator (BPR) was maintained at 9 kg/cm2G. Adsorbent bed was saturated with desorbent at 1.5 mL/min. Feed solution was containing 5 wt% n-octane (tracer) and 95 wt% synthetic C8 aromatics mixture (4.2 wt% EB, 24.4 wt% PX, 53.1 wt% MX, 18.3 wt% OX). Feed solution (step change) was passed through packed bed at 1.5 mL/min, temperature 180°C and pressure 12 kg/cm2, till concentration of adsorbates in the solution at outlet is same as that in the feed solution or adsorbent is saturated. Then, flow of desorbent was resumed through packed bed to desorb adsorbed compounds at 1.5 mL/min, temperature of 180°C and pressure of 12 kg/cm2, till complete desorption of adsorbed C8 aromatics took place. Samples were collected in vials at a time interval of 1 min at the outlet using fraction collector. All samples were analyzed using GC to determine the concentration of each component at the bed outlet with respect to time. Data of variation of concentration at outlet (Co) w.r.t. time (i.e. breakthrough curve) was used to calculate mean residence time (MRT), adsorbed phase concentration (q) for all adsorbates and tracer. Selectivity of p-xylene over other adsorbates m-xylene, o-xylene and ethylbenzene was also calculated. Equations are given below:
Mean residence time (MRT), µ_o=?_0^8¦?(1-C_o/C_F ?)dt
Selectivity of ‘i’ over ‘j’, a_(i/j)=(q_i/C_i)/(q_j/C_j )=(?MRT?_i-?MRT?_tr)/(?MRT?_j-?MRT?_tr )
Quantity of ‘i’ adsorbed per g of adsorbent, q_i=(?MRT?_i-?MRT?_tr )MFR C_(F,i)/M_ads
Total C8 aromatics adsorbed per g of adsorbent, q_total=?_(i=1)^n¦q_i
where, MRTtr is MRT of tracer, CF,i is concentration of ‘i’ in feed, MFR is mass flow rate of feed during breakthrough experiment in g/min, CO is concentration at outlet.

Adsorption & Desorption breakthrough experiments were performed with four adsorbents viz. 1. Conventional adsorbent comprised of zeolite X and potassium exchange for 4 times and barium exchange for 4 times, 2. Adsorbent containing hierarchical zeolite 05:95, potassium exchanged for 4 times and barium exchanged for once, 3. Adsorbent containing hierarchical zeolite 10:90, potassium exchanged for 4 times and barium exchanged for once, 4. Adsorbent containing hierarchical zeolite 20:80, potassium exchanged for 4 times and barium exchanged for once. Respective adsorption and desorption curves are given in Figures 10-13. Results of these adsorption breakthrough experiments are summarized in Table 3. Table 3 clearly shows that adsorbents claimed in said invention has 10 – 20% higher total C8 aromatics (pX, mX, oX, EB) adsorbed, and around 40-50% higher selectivity of p-xylene over m-xylene. Further the concentration of EB in the feed was around 4 wt%. Even at such low concentration of EB, the selectivity of PX/EB was found to be more than 1.5 (and good to separate PX from EB).

Table 3: Results of adsorbent evaluation by adsorption breakthrough experiments at 180°C and 9 kg/cm2G.
Conventional adsorbent Adsorbent 05:95, 4K-1Ba Adsorbent 10:90, 4K-1Ba Adsorbent 20:80, 4K-1Ba
Total C8 aromatics (pX, mX, oX, EB) adsorbed per g of adsorbent, qtotal, g/100 g adsorbent 14 16.3 15.5 17
apX/mX 1.8 2.7 2.6 2.6
apX/oX 1.7 2.8 2.8 2.7
apX/EB 2.4 1.9 2.0 2.0

Additional embodiments and features of the present disclosure will be apparent to one of ordinary skill in art based on the description provided herein. The embodiments herein provide various features and advantageous details thereof in the description. Descriptions of well-known/conventional methods and techniques are omitted so as to not unnecessarily obscure the embodiments herein.
The foregoing description of the specific embodiments will so fully reveal the general nature of the embodiments herein that others can, by applying current knowledge, readily modify and/or adapt for various applications such specific embodiments without departing from the generic concept, and, therefore, such adaptations and modifications should and are intended to be comprehended within the meaning and range of equivalents of the disclosed embodiments. It is to be understood that the phraseology or terminology employed herein is for the purpose of description and not of limitation. Therefore, while the embodiments in this disclosure have been described in terms of preferred embodiments, those skilled in the art will recognize that the embodiments herein can be practiced with modification within the spirit and scope of the embodiments as described herein.
With respect to the use of substantially any plural and/or singular terms herein, those having skill in the art can translate from the plural to the singular and/or from the singular to the plural as is appropriate to the context and/or application. The various singular/plural permutations may be expressly set forth herein for sake of clarity.
Throughout this specification, the word “comprise”, or variations such as “comprises” or “comprising” wherever used, 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 disclosure to achieve one or more of the desired objects or results.
Any discussion of documents, acts, materials, devices, articles and the like that has been included in this specification is solely for the purpose of providing a context for the disclosure. It is not to be taken as an admission that any or all of these matters form a part of the prior art base or were common general knowledge in the field relevant to the disclosure as it existed anywhere before the priority date of this application.
While considerable emphasis has been placed herein on the particular features of this disclosure, it will be appreciated that various modifications can be made, and that many changes can be made in the preferred embodiments without departing from the principles of the disclosure. These and other modifications in the nature of the disclosure or the preferred embodiments 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.