PREPARATION AND CATALYTIC USE IN SINGLE STEP ALKYLATION+DEHYDROGENATION

CROSS REFERENCE TO RELATED APPLICATIONS

[0001] This application claims the benefit of priority of U.S. Provisional Patent Application

No. 62/673,126 filed May 18, 2018, which is hereby incorporated by reference in its entirety.

FIELD OF INVENTION

[0002] The invention generally relates to the field of zeolites and methods of preparing the same. In particular, the invention relates to core/shell zeolite materials.

BACKGROUND

[0003] Zeolites are a family of crystalline materials used extensively as catalyst compositions in the chemical industry. With an increased focus on process and cost optimization in plant operations, an area of interest for researchers, has been on the development of multifunctional zeolite catalysts, which can catalyze more than one set of chemical reaction in a single reactor. It is expected that, such a catalyst when used in a chemical plant, will enhance the overall process efficiency and reduce operational and capital expenditures.

[0004] Compositions containing zeolite catalysts are known to have certain limitations such as: a) limited selectivity; b) susceptibility to deactivation and reduced stability; and c) having large diffusional length, resulting in reduced rate of reaction. Limited selectivity of a catalyst, is particularly a problem, as the product obtained is contaminated with undesirable byproducts and impurities. Further, catalyst deactivation which reduces the catalyst life span, typically occurs when (i) catalytic active sites are directly exposed to severe reaction conditions during a chemical reaction, or when (ii) catalytic active sites on the zeolite surface are leached/eluted during a reaction.

[0005] Attempts to address some of these limitations have been described in the patent literature WO2017164981A to Soultanidis et al. WO2017164981A describes a core/shell structured zeolite having multifunctional catalytic properties in which, at least a portion of the core is coated with a shell layer, and both the core and the shell layers are catalytically active and capable of catalyzing two sets of reactions. The coating by the shell layer limits the exposure of the catalytic active acidic sites on the core to external reaction conditions. However, as described in the patent, the shell layer is usually not uniform and may in some instance, coat only a part of the core. As a result, the shell may only partially protect or limit the exposure of the core to external reaction conditions. Further, the pore size of the shell as described in WO2017164981A is in the range of 5 to 7 Angstrom. However, in some applications, it may beneficial to reduce the pore size further to improve on the catalytic selectivity without compromising on the catalyst efficiency. In addition, the active acidic sites present in the shell layer may themselves be deactivated, because of direct exposure to external reaction conditions. Accordingly, there remains a need to further improve the overall stability and selectivity of such multi-functional core/shell structured zeolite catalyst systems.

[0006] Other solutions taught in literature suggest the use of an inert shell as a protective coating on an active core to improve on the catalyst selectivity and stability. However, in all such solutions, the number of catalytic active sites per weight of the catalyst is reduced and thereby lowers the overall productive efficiency of the catalyst.

[0007] From the foregoing reasons, there remains a need to develop a zeolite catalyst composition with one or more benefits of (i) having the ability to catalyze more than one set of chemical reaction in a single reactor, (ii) having high catalytic selectivity, (iii) having high stability and reduced susceptibility to deactivation, and (iv) having a structure with reduced diffusional length.

SUMMARY

[0008] The invention relates to a composition comprising a core/shell structured zeolite having a core containing a zeolite with a finite silica (S1O2) to alumina (AI2O3) ratio (SAR) and a shell containing a plurality of hollow zeolite particles having an infinite silica (S1O2) to alumina (AI2O3) ratio. Further, the silica content of the shell is independent of the silica content of the core.

[0009] In some embodiments of the invention, the shell that includes the plurality of hollow zeolite particles further includes an impregnated component selected from metals, metal alloys, metal oxides, and any combination thereof. In some embodiments, the impregnated component can include one or more metal oxides. In some embodiments, the metal is selected from the group consisting of platinum (Pt), palladium (Pd), zinc (Zn), gallium (Ga), nickel (Ni), cobalt (Co), tungsten (W), iron (Fe), and combination thereof. In some embodiments, the shell may further include a silica matrix layer in contact with the plurality of hollow zeolite particles and the core. In some embodiments, the core may include a zeolite having a finite SAR ranging from 7 to 150. In some embodiments, the plurality of hollow zeolite particles can include silicalite-l . In some embodiments, the core may includes *BEA-type zeolite, FAU-type zeolite, MFI-type zeolite, or MWW-type zeolite. In some embodiments, the core includes *BEA-type zeolite. In some embodiments, the shell has a pore size ranging from 4.1 A to 5.0 A. In some embodiments, the shell has a pore size ranging from 5.2 A to 7.5 A. In some embodiments, the shell has a thickness ranging from 125 nm to 170 nm. In some embodiments, the core and the shell each have a surface area ranging from 150 rrr.g ¹ to 500 rrr.g ¹

[0010] In other embodiments of the invention, the invention relates to a method of preparing a composition containing a core/shell structured zeolite, comprising the steps of: a) forming a plurality of hollow zeolite particles; b) forming a zeolite particle having a finite SAR; c) dispersing the zeolite particle having a finite SAR in a material that enhances an interaction between the zeolite particle having a finite SAR and the plurality of hollow zeolite particles, and forming a dispersion of the zeolite particle having a finite SAR; and d) combining the plurality of hollow zeolite particles, with the dispersion of the zeolite particle having a finite SAR and forming the composition comprising the core/shell structured zeolite.

[0011] In some embodiments of the invention, the composition containing the core/shell structured zeolite may be further treated with a gel composition that includes: a) silica; b) a templating agent; and c) water. In some embodiments, the plurality of hollow zeolite particles can be impregnated with one or more metals, metal alloys, metal oxides or any combination thereof. In some embodiments, the material that enhances an interaction between the zeolite particle having a finite SAR and the plurality of hollow zeolite particles, is a cationic polymer, selected from the group consisting polyethyleneimine, polydiallyldimethylammonium chloride, and mixtures thereof.

[0012] In yet other embodiments of the invention, the invention relates to a method for conducting a single step alkylation and dehydrogenation of an organic substrate. The method includes the step of, contacting the organic substrate with an alkylating agent in presence of the composition containing the core/shell structured zeolite having a core containing a zeolite with a finite silica (S1O2) to alumina (AI2O3) ratio (SAR) and a shell containing a plurality of hollow zeolite particles having an infinite silica (S1O2) to alumina (AI2O3) ratio. Further, the silica content of the shell is independent of the silica content of the core. In some embodiments, the organic substrate is an aromatic compound having C3-C20 carbon atoms. In some embodiments, the alkylating agent is selected from the group consisting of C1-C20 alkyl compounds, C1-C20 alkylene compounds, C1-C20 alkyne compounds, C1-C20 alcohol compounds, C1-C20 alkyl oxides, C1-C20 alkyl halides, and mixtures thereof. [0013] In the context of the present invention, 20 embodiments are described. Embodiment

1 is a composition comprising a core/shell structured zeolite having: (a) a core comprising a zeolite having a finite silica (S1O2) to alumina (AI2O3) ratio (SAR); and (b) a shell comprising a plurality of hollow zeolite particles having an infinite silica (S1O2) to alumina (AI2O3) ratio (SAR), wherein the shell has silica content independent of silica content of the core. Embodiment 2 is the composition of embodiment 1, wherein the shell comprising the plurality of hollow zeolite particles further comprises an impregnated component selected from the group consisting of metals, metal alloys, metal oxides, and any combination thereof. Embodiment 3 is the composition of embodiment 2, wherein the impregnated component comprises one or more metal oxides. Embodiment 4 is the composition of embodiment 3, wherein the metal is selected from the group consisting of platinum (Pt), palladium (Pd), zinc (Zn), gallium (Ga), nickel (Ni), cobalt (Co), tungsten (W), iron (Fe), and combination thereof. Embodiment 5 is the composition of any one of embodiments 1 to 4, wherein the shell further comprises a silica matrix layer in contact with the plurality of hollow zeolite particles and the core. Embodiment 6 is the composition of any one of embodiments 1 to 5, wherein the core comprises a zeolite having a finite SAR ranging from 7 to 150. Embodiment 7 is the composition of any one of embodiments 1 to 6, wherein the plurality of hollow zeolite particles comprises silicalite-l . Embodiment 8 is the composition of any one of embodiments 1 to 7, wherein the core comprises *BEA-type zeolite, FAET-type zeolite, MFI-type zeolite, or MWW- type zeolite. Embodiment 9 is the composition of embodiment 8, wherein the core comprises *BEA-type zeolite. Embodiment 10 is the composition of any one of embodiments 1 to 9, wherein the shell has a pore size ranging from 4.1 A to 5.0 A. Embodiment 11 is the composition of any one of embodiments 1 to 9, wherein the core has a pore size ranging from 5.2 A to 7.5 A. Embodiment 12 is the composition of any one of embodiments 1 to 11, wherein the shell has a thickness ranging from 125 nm to 170 nm. Embodiment 12 is the composition of any one of embodiments 1 to 12, wherein the core and the shell each have a surface area ranging from 150 nrg ¹ to 500 nrg ¹ .

[0014] Embodiment 14 is a method of preparing a composition comprising a core/shell structured zeolite, wherein the method comprises: (a) forming a plurality of hollow zeolite particles; (b) forming a zeolite particle having a finite SAR; (c) dispersing the zeolite particle having a finite SAR in a material that enhances an interaction between the zeolite particle having a finite SAR and the plurality of hollow zeolite particles and forming a dispersion of the zeolite particle having a finite SAR; and (d) combining the plurality of hollow zeolite particles with the dispersion of the zeolite particle having a finite SAR and forming the composition comprising the core/shell structured zeolite. Embodiment 15 is the method of embodiment 14, wherein the method further comprises treating the composition comprising the core/shell structured zeolite with a gel composition comprising: a) silica; b) a templating agent; and c) water. Embodiment 16 is the method of any one of embodiments 14 to 15, wherein the plurality of hollow zeolite particles is impregnated with one or more metals, metal alloys, metal oxides or any combination thereof. Embodiment 17 is the method of any one of embodiments 14 to 16, wherein the material that enhances an interaction between the zeolite particle having a finite SAR and the plurality of hollow zeolite particles, is a cationic polymer selected from the group consisting polyethyleneimine, polydiallyldimethylammonium chloride, and mixtures thereof.

[0015] Embodiment 18 is a method for conducting a single step alkylation and dehydrogenation of an organic substrate, the method comprising contacting the organic substrate with an alkylating agent in presence of any one of the core/shell structured zeolite compositions of embodiments 1 to 13. Embodiment 19 is the method of embodiment 18, wherein the organic substrate is an aromatic compound having C3-C20 carbon atoms. Embodiment 20 is the method of any one of embodiments 18 to 19, wherein the alkylating agent is selected from the group consisting of C1-C20 alkyl compounds, C1-C20 alkylene compounds, C1-C20 alkyne compounds, C1-C20 alcohol compounds, C1-C20 alkyl oxides, Ci- C20 alkyl halides, and mixtures thereof.

[0016] Other objects, features and advantages of the invention will become apparent from the following figures, detailed description, and examples. It should be understood, however, that the figures, detailed description, and examples, while indicating specific embodiments of the invention, are given by way of illustration only and are not meant to be limiting. Additionally, it is contemplated that changes and modifications within the spirit and scope of the invention will become apparent to those skilled in the art from this detailed description. In further embodiments, features from specific embodiments or aspects may be combined with features from other embodiments. For example, features from one embodiment or aspect may be combined with features from any of the other embodiments. In further embodiments, additional features may be added to the specific embodiments described herein. BRIEF DESCRIPTION OF THE DRAWINGS

[0017] For a more complete understanding, reference is now made to the following descriptions taken in conjunction with the accompanying drawings.

[0018] FIG. 1 is a cross sectional representation of a composition containing a core/shell structured zeolite in an embodiment of the invention.

[0019] FIG. 2 is a cross sectional representation of a hollow zeolite particle impregnated with a catalytically active material.

[0020] FIG. 3 is a schematic illustration of a method of preparing a composition containing a core/shell structured zeolite involving a core made of *BEA-type zeolite and a shell made of a metal impregnated hollow zeolite;

[0021] FIG. 4 is a comparison of an X-ray diffraction (XRD) pattern analysis of the composition containing the core/shell structured zeolite prepared under an embodiment of the invention with that of the XRD pattern of a *BEA-type zeolite constituting the core and a Zinc impregnated hollow zeolite particle constituting the shell;

[0022] FIG. 5A is the scanning electron microscope (SEM) image of a *BEA-type zeolite prior to the formation of a composition containing the core/shell structured zeolite;

[0023] FIG. 5B is the SEM image of the composition containing the core-shell structured zeolite - a core having *BEA-type zeolite and a shell having Zinc impregnated hollow zeolite particle (silicalite-l); and

[0024] FIG. 6A is the transmission electron microscope (TEM) image of the composition containing the core/shell structured zeolite with Energy Dispersive X-ray (EDX) analysis.

[0025] FIG. 6B is a magnified TEM image of the composition containing the core/shell structured zeolite and illustrating the interface or the contact point of the shell and the *BEA- type zeolite core.

[0026] FIG. 7 illustrates a chemical reactor arrangement for the preparation of vinyl aromatic compounds such as styrene, using a core/shell structured catalyst of the invention.

DETAILED DESCRIPTION

[0027] The invention, is based, in part on the discovery, that a composition containing a specific core/shell structured zeolite can be used as a catalyst that can exhibit one or more benefits of (i) the ability to catalyze more than one set of chemical reactions in a single reactor, (ii) a high catalytic selectivity, (iii) a high stability and reduced susceptibility to deactivation, or (iv) a structure with reduced diffusional length. Advantageously, the catalyst composition is designed to have unique features that impart useful chemical process behavior, namely a core having a finite silica (S1O2) to alumina (AI2O3) ratio (SAR) and a shell having a plurality of hollow zeolite particles having an infinite silica (S1O2) to alumina (AI2O3) ratio (SAR). These features create a core and a shell, having two different catalytic active sites, thereby enabling the composition containing the core/shell structured zeolite, to catalyze at least two sets of different chemical reactions. Further the pore size of the shell and the core are designed to complement each other in a manner which enhances catalytic selectivity without reducing catalytic efficiency.

[0028] The following includes definitions of various terms and phrases used throughout this specification.

[0029] The terms“about” or“approximately” or“substantially” are defined as being close to as understood by one of ordinary skill in the art. In one non-limiting embodiment the terms are defined to be within 1%, preferably, within 0.1%, more preferably, within 0.01%, and most preferably, within 0.001%.

[0030] The terms“wt.%”,“vol.%”, or“mol.%” refers to a weight, volume, or molar percentage of a component, respectively, based on the total weight, the total volume, or the total moles of material that includes the component. In a non-limiting example, 10 moles of component in 100 moles of the material is 10 mol.% of component.

[0031] The term“substantially” and its variations are defined to include ranges within 10%, within 5%, within 1%, or within 0.5%.

[0032] The terms“inhibiting” or“reducing” or“preventing” or“avoiding” or any variation of these terms, when used in the claims and/or the specification includes any measurable decrease or complete inhibition to achieve a desired result.

[0033] The term“effective,” as that term is used in the specification and/or claims, means adequate to accomplish a desired, expected, or intended result.

[0034] The use of the words“a” or“an” when used in conjunction with the term “comprising,”“including,”“containing,” or“having” in the claims or the specification may mean“one,” but it is also consistent with the meaning of“one or more,”“at least one,” and “one or more than one.” [0035] The words“comprising” (and any form of comprising, such as“comprise” and “comprises”),“having” (and any form of having, such as“have” and“has”),“including” (and any form of including, such as“includes” and“include”) or“containing” (and any form of containing, such as“contains” and“contain”) are inclusive or open-ended and do not exclude additional, unrecited elements or method steps.

[0036] The method of the invention can“comprise,”“consist essentially of,” or“consist of’ particular ingredients, components, compositions, etc., disclosed throughout the specification. With respect to the phrase“consisting essentially of,” in one non-limiting aspect, a basic and novel characteristic of the zeolite catalysts of the present invention can include (i) the ability to catalyze more than one set of chemical reactions in a single reactor, (ii) a high catalytic selectivity, (iii) a high stability and reduced susceptibility to deactivation, and/or (iv) a structure with reduced diffusional length.

[0037] Any numerical range used through this disclosure shall include all values and ranges there between unless specified otherwise. For example, a boiling point range of 50 °C to 100 °C includes all temperatures and ranges between 50 °C and 100 °C including the temperature of 50 °C and 100 °C.

[0038] The term“SAR” means silica (S1O2) to alumina (AI2O3) weight ratio associated with a particular type of zeolite structure.

[0039] In one version of the invention, referring to FIG. 1, the composition containing the core/shell structured zeolite (100) of the invention, comprises a core (101) having a finite silica (S1O2) to alumina (AI2O3) ratio (SAR) and a shell (102) comprising a plurality of hollow zeolite particles (103) having an infinite silica (S1O2) to alumina (AI2O3) ratio (SAR). Further the silica content of the shell (102) is independent of the silica content of the core (101). As used herein, reference to zeolite having an“infinite SAR” or a“SAR of infinity” means a zeolite composition having no alumina or substantially no alumina, wherein substantially no alumina means no alumina or levels of alumina at levels so low that any chemical activity attributable to alumina is negligible.

[0040] In another version of the invention, the core (101) has a particle size defined three dimensionally along the (x,y,z) axis, ranging from (700 nm x 500nm x 500 nm) to (100 nm xlOO nm xlOO nm), alternatively from (500 nm x 300 nm x 300 nm) to (200 nm x 200 nm x 200 nm), alternatively from (400 nm x 200 nm x 200 nm) to (150 nm x 150 nm xl50 nm). The particle size of the core may be measured by using any of the known analytical techniques such as Transmission Electron Microscopy (TEM). The core (101) includes zeolite selected from *BEA-type zeolite, FAET-type zeolite, MFI-type zeolite, or MWW-type zeolite. In one preferred embodiment, the core (101) includes *BEA-type zeolite. In one aspect of the invention, the core (101) is a zeolite having a finite SAR. In another aspect, *BEA-type zeolite when used as the core (101) may be also referred to as parent *BEA. The SAR ranges from 7 to 150, alternatively from 7 to 35, alternatively from 8 to 20, alternatively from 10 to 15. The finite SAR denotes the presence of catalytically active acidic alumina sites in the core (101). The presence of catalytically active acidic sites allows the core to catalyze chemical reactions including alkylation of organic substrates/molecules. In one aspect the core (101) has a pore size ranging from 5.2 A to 7.5 A, alternatively from 5.5 A to 6.5 A, alternatively from 5.8 A to 6 A. In one preferred embodiment, the pore size of the core is 5.9 A. The pore size may be determined using nitrogen (N2) isotherm technique. In some aspects, the pore size of the core (101) is larger than that of the shell (102).

[0041] In one version of the invention, the shell (102) is in direct contact with the core (101) and covers substantially all of the surface area of the core (101). In a preferred embodiment, the shell (102) covers the entire surface area of the core (101) which is also evidenced by the non-limiting SEM and TEM images of FIG. 5B and FIG. 6A respectively. Preferably, the shell (102) covers at least 99%, alternatively at least 99.5%, or alternatively at least 100% of the surface area of the core (101). In another aspect, the core and the shell each have a surface area in the range of 150 nrg ¹ to 500 nrg ¹ , alternatively in the range of 190 nrig ¹ to 400 m ² g ^_1 , or alternatively in the range of 250 m ² g ^_1 to 350 nrig ¹ , or any range or value there between. The surface area may be determined by using any of the known techniques used for such measurement such as N2 isotherm technique.

[0042] In one version of the invention, the shell (102) can include a plurality of hollow zeolite particles (103). The plurality of hollow zeolite particles (103) are in direct contact with each other or are separated from each other by a silica matrix layer (104). In one embodiment, the plurality of hollow zeolite particles (103) is dispersed in the silica matrix layer (104). In yet another embodiment the shell further comprises a silica matrix layer (104), which is in contact with the core (101) and the plurality of hollow zeolite particles (103). The silica matrix layer (104) has a SAR of infinity and preferably has an MFI structure. In one preferred aspect the silica matrix layer (104) is pure silica, preferably silicalite-l . In another preferred embodiment, the silica content of the shell (102) is constituted from the plurality of hollow zeolite particles (103) and from the silica matrix layer (104). The silica content of the shell (102) is independent or is substantially independent from the silica content of the core (101). In one embodiment of the invention, the zeolite structure constituting the shell (102) has a different crystalline structure from the zeolite structure constituting the core (101). The term“independent” as used herein means that the zeolite structure of the shell (102) is not derived from the zeolite structure of the core (101) thereby ensuring that the core (101) and shell (102) each have distinct crystalline structure, pore size and distinct catalytic selectivity. In some literature references, the shell (102) is formed from the crystallization growth on the surface of the core (101). In one aspect of the invention, the independent silica content of the shell and the core is achieved by the method of synthesis employed as described in a non-limiting manner in the Examples to prepare the composition containing the core/shell structured zeolite. However, it may be appreciated by a person skilled in the art, that the independent silica content may also be achieved by any other suitable method for the synthesis of a composition containing such a core/shell structured zeolite.

[0043] In one embodiment of the invention, the shell (102) has a thickness ranging from 125 nm to 170 nm, alternatively from 135 nm to 165 nm, or alternatively from 145 nm to 155 nm, or any range or value there between. In one embodiment, the shell has a thickness of about 150 nm. In one aspect of the invention, the thickness of the shell (102) constituting the core/shell structured zeolite is substantially uniform with a variation of thickness less than 60 nm, alternatively less than 50 nm, alternatively less than 45 nm, alternatively less than 25 nm or any range or value there between. The shell has a minimum thickness of 0.01 nm. The shell (102) has a porous zeolite structure, which is particularly useful in limiting the access of reactants and reagents to the acidic active site of the core (101) and thereby increases the selectivity of only specific molecules to diffuse through the shell. The pore size of the shell (102) ranges from 4.1 A to 5.0 A, alternatively 4.3 A to 4.9 A, and alternatively 4.4 A to 4.8 A or any value or range there between..

[0044] In one embodiment of the invention, the plurality of hollow zeolite particle (103) comprises individual hollow zeolite particles. Referring to FIG. 2, the individual hollow zeolite particle (115) can include an inner cavity (106), enclosed by a thin zeolite shell (105) where catalytic active materials (107), can be impregnated, thereby serving as a nano/micro reactor for conducting chemical reactions. As reported in literature by Prates et al. (“Hollow Beta Zeolite Single Crystals for the Design of Selective Catalysts”, Cryst. Growth Des. 2018, 18, 592-59) and by Pagis et al. (“Hollow Zeolite Structures: An Overview of Synthesis Methods” Chem. Mater. 2016, 28, 5205-5223), hollow zeolites are particularly advantageous over other ordinary zeolites as: (i) the shell thickness of hollow zeolites are uniform and can generally be adjusted by controlling the synthesis parameters, (ii) hollow zeolites have relatively small dilfusional path length and high selectivity for reactant molecules, and (iii) hollow zeolites have high hydrothermal stability. Therefore, without wishing to be bound by theory, it is expected that the incorporation of hollow zeolite particles for forming the shell of the core/ shell structured zeolite, will help in imparting one or more of its characteristic benefits to the composition containing the core/ shell structured zeolite.

[0045] In some embodiments of the invention, the individual hollow zeolite particle (115) can include a pure silica based zeolite. Non-limiting examples of pure silica based zeolite include silicalite-l, ZSM-5 and TS-l . In preferred embodiments, the individual hollow zeolite particle (115) is silicalite-l . In another embodiment, the plurality of hollow zeolite particles includes silicalite-l . In another preferred embodiment, the silicalite-l has an MFI structure. In one aspect of the invention, the individual hollow zeolite particle, has a silica to alumina ratio (SAR) of infinite with no alumina content or Lewis acid catalytic sites being present. This is particularly advantageous, as the lack of acidic sites renders the zeolite inert or substantially inert to specific reactants and reagents during a chemical reaction and can help in improving the selectivity of the catalyst. The individual hollow zeolite particle (115) can have a particle size defined three dimensionally along the (x,y,z) axis, ranging from (150 nm x 150 nm x 150 nm) to (100 nm x 100 nm x 100 nm), alternatively from (120 nm x 120 nm x 120 nm) to (110 nm x 110 nm x 110 nm) or any value or range there between. The thin zeolite shell (105) is uniform or substantially uniform having a thickness ranging from 20 nm to 100 nm, alternatively from 30 nm to 80 nm, alternatively from 50 nm to 70 nm. In another embodiment, the individual hollow zeolite particles (115) has a spherical shape. Without wishing to be bound by any theory, the uniformity and spherical shape of the thin zeolite shell (105) is due to the use of a templating agent or a structure directing agent used for the synthesis of the individual hollow zeolite particle (115).

[0046] In some embodiments, the shell that includes the plurality of hollow zeolite particles can further include an impregnated component selected from the group consisting of metals, metal alloys, metal oxides and any combination thereof. Referring to FIG. 2, in embodiments of the invention, the hollow zeolite particle (115) is impregnated by an impregnated component that includes one or more metal, metal alloys, metal oxides or combinations thereof. In a preferred embodiment the impregnated component can include one or more metal oxides. The term“impregnated component” as used herein means that all or substantially all of the component is located within the inner cavity (106) of the hollow zeolite particle (115). Referring back to FIG. 1, in one preferred aspect, the plurality of hollow zeolite particles (103) is impregnated with an impregnated component comprising one or more metals, metal alloys, metal oxides or combinations thereof. While in the preferred embodiment, the impregnated component can be one or more metals, metal alloys, metal oxides or combinations thereof, it should be understood that other impregnated components comprising non-metal based materials are possible to be used in the invention.

[0047] Non-limiting examples of metal include, platinum (Pt), palladium (Pd), zinc (Zn), gallium (Ga), nickel (Ni), cobalt (Co), tungsten (W), iron (Fe) or any combination thereof. Without being bound by any specific theory, as reported by Pagis et al. (“Hollow Zeolite Structures: An Overview of Synthesis Methods” Chem. Mater. 2016, 28, 5205-5223), hollow zeolites are particularly adapted for the impregnation by catalytically active materials, because of their size adjustable cavities, as well as for their uniform micro-porosity. Referring to FIG. 2, in one aspect of the invention, all of the metals, or metal oxides or metal alloys (metal based particles) are completely impregnated within the thin shell zeolite shell (105). The impregnation of metal based particles prevents sintering under harsh catalytic conditions and also improves catalytic selectivity. As the size of the metal based particles can be controlled, hollow zeolite particles become particularly useful in controlling the leaching and dispersion of the metal based particles and thereby help improving catalyst stability. In particular, the shell (105) acts as a molecular sieve and protects the metal particles from external poisoning and leaching. In some embodiments, the hollow zeolite particles (115) functions as a micro/nano reactor with the impregnated metal based particles functioning as a catalyst and the shell (105) being substantially inert to any chemical reaction. The total amount of metals or metal alloys or metal oxides (metal based particles) present in the hollow zeolite particle (115) ranges from 10 wt% to 0.5 wt%, alternatively from 8 wt% to 2 wt%, alternatively from 6 wt% to 3 wt% or any range or value there between of the hollow zeolite particle.

[0048] In one embodiment of the invention, methods of preparing a composition that includes the core/shell structured zeolite are described. A method can include the steps of: (i) forming a plurality of hollow zeolite particles; (ii) forming a zeolite having a finite S AR; (iii) dispersing the zeolite having a finite SAR in a material that enhances an interaction between the zeolite having a finite SAR and the plurality of hollow zeolite particles, and forming a dispersion of the zeolite having a finite SAR; and (iv) combining the plurality of hollow zeolite particles with the dispersion of the zeolite having a finite SAR and forming the composition comprising the core/shell structured zeolite. In a preferred embodiment, the zeolite with the finite SAR forms the core of the core/shell structured zeolite and the plurality of hollow zeolite particles forms the shell. In another aspect of the invention, the core/shell structured zeolite prepared from the aforesaid method, can be treated with a gel composition that includes: a) silica; b) a templating agent; and c) water. The treatment by the gel composition results in the formation of a silica matrix layer which is in contact with the plurality of hollow zeolite particles and the core.

[0049] In another embodiment of the invention, the plurality of hollow zeolite particles is impregnated with one or more metals, metal alloys, metal oxides or any combination thereof. In a preferred embodiment, the metal can be selected from Pt, Pd, Zn, Ga, Ni, Co, W, Fe, an oxide thereof, an alloy thereof, or any combination thereof.

[0050] In one embodiment, the material used for enhancing the interaction between the zeolite particle having a finite SAR and the plurality of hollow zeolite particles is a cationic polymer. The cationic polymer that may be used in the invention include polyethyleneimine, polydiallyldimethylammonium chloride (PDDA) and mixtures thereof. The cationic polymer may be in the form of an aqueous solution and helps enhancing the interaction between the zeolite having finite SAR and the plurality of hollow zeolite particles. Non-limiting examples of the interaction between the zeolite having finite SAR and the plurality of hollow zeolite particles is that of an electrostatic interaction.

[0051] A schematic representation of a method to obtain a composition containing a core/shell structured zeolite for an embodiment of the invention is shown under FIG. 3. Referring to FIG. 3, a pure silica material such as silicalite-l based zeolite is subjected to recrystallization and dissolution to form a hollow zeolite particle (H-Sl). The process for forming the hollow zeolite particle (H-Sl) involves treating the pure silica material with the corresponding templating agent in the hydroxide form such as tetrapropylammonium hydroxide TPA(OH), and forming a hollow zeolite precursor mixture. The precursor mixture is subsequently transferred to an autoclave and thermally treated at a temperature in the range of 150 °C to 200 °C, alternatively in the range of 160 °C to 190 °C, alternatively in the range of 160 °C to 185 °C or any range or value there between. The thermal treatment is conducted for at least 50 hours, alternatively for at least 60 hours, alternatively for at least 70 hours, or any range or value there between. The material so obtained is washed and subsequently calcined for at least 4 hours, alternatively for at least 5 hours, at a calcination temperature in the range of 500 °C to 600 °C to obtain the hollow zeolite particle (H-Sl). Using a similar process for a number of pure silica zeolite particles, the plurality of hollow zeolite particles may be formed.

[0052] In one embodiment of the invention, the hollow zeolite particle (H-Sl) is impregnated with one or more metals, metal alloys, metal oxides or any combinations thereof. The impregnation process includes a wet impregnation technique, to form a metal impregnated hollow zeolite particle (M-HS1). The wet impregnation method includes the steps of contacting a metal precursor compound dissolved in solvents such as methanol, with the hollow zeolite particle (H-Sl) followed by washing, drying and calcining to obtain the metal impregnated hollow zeolite (M-HS1). In a preferred embodiment, the metal precursor used is zinc nitrate salt. The washing is done in a manner to ensure all of the metal or the metal alloys or metal oxides (metal based particles) are removed from the surface of the hollow zeolite particle but not from the inner cavity of the hollow zeolite thereby ensuring that all of the metal, or the metal allow or the metal oxides are contained only within the hollow zeolite particle. This feature is particularly important to ensure stability of the composition containing the core/shell structured zeolite when used as a catalyst. The calcination is conducted at a temperature in the range of 500 °C to 600 °C, alternatively at a temperature 520 °C to 580 °C for at least 4 hours, alternatively for at least 6 hours. The process can be repeated to form a plurality of metal impregnated hollow zeolite.

[0053] Referring to FIG. 3 further, the zeolite having a finite SAR is formed using a *BEA- type zeolite. The *BEA-type zeolite is treated with a cationic polymer for reversing the surface charge on the *BEA-type zeolite. In one aspect, the cationic polymer is polyethyleneimine. The resultant *BEA-type zeolite post the treatment, has a net cationic charge and a dispersion containing the *BEA-type zeolite is subsequently formed. The dispersion containing the *BEA-type zeolite is combined with the plurality of metal impregnated hollow zeolite particle (M-HS1) resulting in the adsorption of the metal impregnated hollow zeolite particle (M-HS1) on the surface of the *BEA-type zeolite surface to form the core/shell structured zeolite with the core including the *BEA-type zeolite and the shell including the plurality of metal impregnated hollow zeolite particles (M-HS1). The composition containing the core/shell structured zeolite is further dried at a temperature in the range of 75 °C to 90 °C, alternatively in the range of 78 °C to 85 °C for at least 3 hours and thereafter calcined at a temperature in the range of 500 °C to 600 °C, alternatively at a temperature in the range of 520 °C to 580 °C for at least 4 hours, alternatively for at least 6 hours. [0054] The composition containing the core/shell structured zeolite is treated with a gel composition for secondary growth of zeolite crystals using a gel composition that includes a) silica, b) a templating agent, and c) water, to obtain a desired thickness of the shell and also to ensure that the shell covers the entire surface area of the core. The secondary growth achieved through the use of the gel results in the formation of a silica matrix layer which is in contact with the metal impregnated hollow zeolite particles (M-HS1) and the *BEA-type zeolite core. In embodiments of the invention, the templating agent used is one of tetrapropylammonium hydroxide, tetraethylammonium hydroxide, tetramethylammonium hydroxide and mixtures thereof. In one preferred aspect, the templating agent is tetrapropylammonium hydroxide and is used for forming the MFI-type zeolite structure for the hollow zeolite particle. The templating agent provides the structure for the hollow zeolite, although other means to achieve this are possible, including basic treatment of a non-hollow zeolite precursor.

[0055] In another aspect of the invention, methods for conducting a single step alkylation and dehydrogenation of an organic substrate are described. A method can include the step of contacting the organic substrate with an alkylating agent in the presence of the composition containing the core/shell structured zeolite of the invention under conditions suitable to alkylate and dehydrogenate the organic substrate. In an embodiment of the invention, the organic substrate includes one or more aromatic compounds having C3 to C20 carbon atoms. Non limiting examples of such aromatic compounds can include benzene, naphthalene, phenanthrene, anthracene and derivatives thereof, any combination thereof. In one embodiment, the aromatic compound is benzene. In an embodiment of the invention, the alkylating agent can include Ci to C20 alkyl compounds, Ci to C20 alkylene compounds, C1-C20 alkyne compounds, Ci to C20 alcohol compounds, Ci to C20 alkoxides, Ci to C20 alkyl halides, and any combinations thereof. Non-limiting examples of alkylating agent are ethylene, propylene, butylene, methanol, ethanol or any combination thereof. In one preferred embodiment, the alkylating agent is ethylene.

[0056] In one particular aspect of the invention, a method for producing vinyl aromatic hydrocarbons such as styrene, alpha-methyl styrene is provided. The method can include reacting an alkylating agent ( e.g ., ethylene or propylene) with an organic substrate such as an aromatic compound (e.g., benzene) in the presence of the composition containing the core/shell structured zeolite of the invention, under conditions sufficient to produce the vinyl aromatic hydrocarbon. Referring to FIG. 7, a schematic representation of the system (108) for the production of vinyl aromatic hydrocarbon such as styrene is depicted. System (108) can include a continuous flow reactor (112) and a reaction zone (111) that includes a core/shell structured zeolite (110) of the kind depicted in FIG. 1. A reactant stream that includes an alkylating agent such as ethylene, propylene, butylene, and an aromatic hydrocarbon such as benzene can enter the continuous flow reactor (112) via the feed inlet (109). The molar ratio of the aromatic compound to alkylating agent can be in the range of 1 : 1 to 6: 1, alternatively in the range of 2: 1 to 4: 1 or any value or range there between. In one embodiment, the ratio of aromatic compound to alkylating agent is 3 : 1. In some instances, the catalytic material can be layered or in beds in the continuous flow reactor (112). The continuous flow reactor can be a fixed bed reactor or fluidized circulating reactor ( e.g ., an ebullating bed reactor). In some embodiments, any one of the feeds may include a gaseous diluent. The gaseous diluent may be, for example, nitrogen, helium, argon, carbon dioxide, or water, or any combination thereof.

[0057] Reaction zone (111) and the reactant feed(s) can be heated to a temperature suitable for an aromatic alkylation reaction followed by in situ dehydrogenation using known heating sources (e.g., heaters, heat exchangers, steam, oil, high temperature circulating fluid, or combinations thereof). The temperature condition can be maintained at a range of 300 °C to 650 °C, alternatively at a range of 320 °C to 580 °C, or alternatively at a range of 350 °C to 500 °C, or any range or value there between. The pressure can be maintained at range of 0.7 atmosphere to 1.1 atmosphere, alternatively at a range of 0.8 atmosphere to 1 atmosphere, or any range or value there between. Contact of the alkylating agent and the aromatic hydrocarbon with the composition containing the core/shell structured zeolite catalyst (110) of the invention under these conditions can produce a product stream that includes the vinyl aromatic hydrocarbon (e.g, styrene).

[0058] The product stream can exit continuous flow reactor (112) via product outlet (113), and be transported to a collection zone. In the collection zone, the vinyl aromatic hydrocarbon can be separated from the reactant feed stream using known separation techniques, for example, distillation, absorption, membrane technology, etc., to produce a vinyl aromatic hydrocarbon. The method can further include isolating and/or storing the produced vinyl aromatic hydrocarbon or the separated products.

[0059] Accordingly, the invention includes embodiments that include zeolite compositions that (i) have the ability to catalyze more than one set of chemical reaction in a single reactor, (ii) have high catalytic selectivity, (iii) have high stability and reduced susceptibility to deactivation, and/or (iv) have a structure with reduced diffusional length. The invention also includes methods of making and using such compositions. Advantageously, the invention now provides previously unavailable uses and benefits. Advantageously, the invention now enables artisans the ability to design a catalyst having unique features that impart useful chemical process behavior, namely a core having a finite silica (S1O2) to alumina (AI2O3) ratio (SAR) and a shell having a plurality of hollow zeolite particles having an infinite silica (S1O2) to alumina (AI2O3) ratio (SAR). These features create a core and a shell, having two different catalytic active sites, thereby enable the composition containing the core/shell structured zeolite of the invention, to catalyze at least two different chemical reactions. Further the pore size of the shell and the core complement each other in a manner that enhances catalytic selectivity without reducing catalytic efficiency.

[0060] Specific examples demonstrating some of the embodiments of the invention are included below. The examples are for illustrative purposes only and are not intended to limit the invention. Those of ordinary skill in the art will readily recognize parameters that can be changed or modified to yield essentially the same results.

EXAMPLE

Example 1

(Synthesis and characterization of a composition containing a core/shell structured zeolite prepared in accordance with an embodiment of the invention)

[0061] Purpose: Example 1 demonstrates the synthesis and material characterization results of a composition containing a core/shell structured zeolite prepared in accordance with an embodiment of the invention.

[0062] Materials: The following materials were procured and used for the synthesis of the composition containing the core/shell structured zeolite as well as for the synthesis of the core and the shell individually. Table lists the materials, description and supplier.

Table 1

[0063] Process/Procedure: The following method for synthesizing a composition containing a core/shell structured zeolite was practiced for the purpose of this Example. The method included the steps of a) forming a plurality of hollow zeolite particles; b) forming a zeolite particle having a finite SAR; c) dispersing the zeolite particle having a finite SAR in a material that enhanced the interaction between the zeolite particle having a finite SAR and the plurality of hollow zeolite particles, and forming a dispersion of the zeolite having a finite SAR; and d) combining the plurality of hollow zeolite particles with the dispersion of the zeolite particle having a finite SAR and forming the composition containing the core/shell structured zeolite. The method further included the step of treating the core/shell structured zeolite with a gel composition comprising a) silica; b) a templating agent; and c) water. In accordance with the present embodiment of the invention, the plurality of hollow zeolite particle was first impregnated with one or more metals, metal alloys, metal oxides or combinations thereof, prior to forming the core/shell structured zeolite.

[0064] More particularly, referring to FIG. 3 the method of preparing the core/shell zeolite structure involved forming a core from a zeolite particle having finite SAR such as a *BEA- type zeolite and forming a shell from a plurality of metal-impregnated hollow zeolite particles comprising silicalite-l . The core was surface treated with a cationic polymer and a dispersion containing the treated core was subsequently combined with the plurality of metal-impregnated hollow zeolite particles.

[0065] Forming the plurality of metal impregnated hollow zeolite particles (Zn Hollow S- 1). Synthesis of hollow zeolite particles (H-Sl). The method involved using zeolite of the type silicalite-l having a SAR value of infinity. The silicalite-l zeolite was treated with the corresponding template in the hydroxide form, tetrapropylammonium hydroxide (TPA(OH), for obtaining the MFI zeolite structure and post the treatment, the mixture so obtained was transferred to a Teflon-lined autoclave and was heated at 180 °C for about 72 hour to obtain the hollow silicalite zeolite (HS-l). Subsequently, the hollow zeolite (HS-l) so obtained, was recovered by centrifugation (15 min. @ 10000 imp) and was washed several times with water to ensure the removal of excess of template. After drying the material at 100 °C under air for about 10 hours, the hollow zeolite was calcined 6 h at 540 °C (1 °C/min) under air in order to clean the zeolite pores. The hollow zeolite (HS-l) so obtained was further treated using a wet impregnation technique to form the metal impregnated hollow zeolite (M-HS1).

[0066] Synthesis of Metal-impregnated Hollow zeolite (M-HS1) particularly Zn Hollow S- 1. For the synthesis, zinc nitrate (0.637 g) was dissolved in methanol (2 mL) and subsequently mixed with HS-l (1.34 g) to form a mixture having hollow zeolite and zinc nitrate. A special washing procedure was used to ensure the removal of metals from the surface of the hollow zeolite surface and not from inside the cavity. The washing was carried out by adding water (8-12 mL) to the mixture, shaking @ 100 rpm, and subsequently removing any solvent or washing agent. The product so obtained, was dried at 80 °C for 4 hours then calcined at 550 °C (1 °C /min) for 6 hours under air to obtain the metal impregnated hollow zeolite (M-HS1) and particularly Zn Hollow S-l .

[0067] Forming the zeolite particle having finite SAR (core) or parent *BEA. The core used for the purpose of this example was a commercially available zeolite, procured from Zeolyst, having a finite SAR for which a *BEA-type zeolite (also referred to as parent *BEA) was used.

[0068] Preparing the core/ shell structured zeolite. The *BEA-type zeolite was combined with a plurality of metal impregnated hollow zeolite (M-HSl)/Zn Hollow S-l, using the process as described herein below. The *BEA-type zeolite was dispersed in a solution containing an aqueous solution of polyethylenimine cationic polymer in which, *BEA-type zeolite particle (about 0.5 grams) was dispersed in an aqueous solution of 0.6% polyethylenimine (20 mL) and stirred for 1.5 hours to form a dispersion having the treated *BEA-type zeolite. The treated *BEA-type zeolite, was subsequently washed with distilled water and recovered by centrifugation at a speed of 6,000 rpm. The treated *BEA-type zeolite was subsequently dispersed in distilled water (20 mL) and ometal-impregnated hollow zeolite particle (M-HS1, 0.3 grams) made of silicalite-l and the resultant mixture was stirred vigorously for an hour. The mixture was then washed with water and centrifuged to recover the product. The product was then dried at 80 °C for 3 hours and calcined at 500 °C for 6 hours. The product so obtained was then transferred to an autoclave and was further treated with a gel solution comprising TPAOH/SiCh/HiO having molar ratios of 1.5/25/1500. The product so obtained was further thermally treated at 200 °C for 10 minutes in an autoclave. The product was recovered by washing and centrifugation and subsequently dried at 90 °C for 6 hours and calcined at 500 °C for 6 hours to obtain the core/shell structured zeolite as contemplated under the present embodiment.

[0069] Results: The composition containing the core/shell structured zeolite was analyzed and characterized using various material analysis techniques as described:

[0070] XRD Analysis. XRD patterns were collected with Empyrean X-ray diffractometer from PANalytical (the Netherlands) using a nickel-filtered CuKa X-ray source, a convergence mirror, and a PIXcelld detector. The scanning rate was 0.01 degrees over the range between 5 degrees and 80 degrees at 2 theta (Q). The XRD patterns obtained for the core/shell structured zeolite was compared with the XRD pattern obtained for the parent *BEA zeolite and the metal impregnated hollow zeolite particles (Zn Hollow S-l) as shown under FIG. 4.

[0071] SEM Analysis: SEM analysis was performed using a Titan G2 80-300 kV transmission electron microscopy (FEI™, ETSA) operating at 300 kV equipped with a 4 k x 4 k CCD camera, a GIF Tridiem (Gatan, Inc.) and an energy-dispersive X-ray spectroscopy (EDS) detector (ED AX, ETSA). Field-emission SEM pictures were obtained with a FEI Quanta 600 FEG. FIG. 5 shows the SEM image of the core/shell structured zeolite. Particularly, FIG. 5A shows the SEM and EDX analysis of the parent *BEA. FIG. 5B illustrates the SEM image and EDX analysis of the parent *BEA core, after the adsorption of the metal impregnated hollow zeolite particles or (Zn Hollow S-l) on the surface of the parent *BEA.

[0072] TEM Analysis. FIG. 6A and FIG. 6B depict the TEM/EDX analysis of the composition containing the core/shell structured zeolite. FIG. 6B specifically shows a magnified image of the interface between the Zinc Hollow S-l particle and the parent *BEA. The EDX analysis of the core and the shell depict the constituting elements of the core and the shell.

[0073] Isothermal Analysis. Nitrogen adsorption/desorption isotherms of the BEA-MFI zeolite of the invention was collected at 77 K using a Micromeritics® ASAP 2010 instrument (Micromeritics®, ETSA). Before the measurement, approximately 100 mg of sample was degassed under vacuum (10 ⁶ bar) at 350 °C for 10 hours. The pore size of the core was determined to be approximately 5.95 A while the pore size of the shell was determined to be approximately 4.6 A.

[0074] Discussion: Analyzing the results from the XRD, SEM, TEM, N2 Isothermal and EDX characterization, it was concluded that the zeolite composition synthesized using the method described under Example 1, contained a unique core/shell structure that was formed by a core that included the parent *BEA zeolite particle having a finite SAR, and a shell comprising metal impregnated hollow zeolites particles (Zinc Hollow S-l) having an infinite SAR. The composition containing the core/shell structure synthesized using the method of Example 1, had a combined property and characteristics of two distinct zeolite systems in a single zeolite framework. This unique structural arrangement was particularly suitable for using the composition containing the core/shell structured zeolite as a catalyst with enhanced selectivity, stability and having the ability to catalyze more than one chemical reaction in a single reactor system. [0075] From the XRD pattern analysis as shown in FIG. 4, it was concluded that the composition containing the core/shell structured zeolite had a combination of properties and characteristics of the individual zeolite systems which formed the core/shell structured zeolite. This was evidenced from the comparison of the signature patterns of the core/shell structured zeolite with that of the parent *BEA particle and the metal-impregnated hollow zeolite particles (Zinc Hollow S-l), where the core/shell structured zeolite exhibited similar characteristic peaks to that of *BEA and Zinc Hollow S-l . For example, the shoulder of the XRD pattern of the core/shell structured zeolite at 6 as well as the peak at 22.5 on the 20 axes, are characteristic of the parent *BEA structure and the Zn Hollow S-l . Thus the core/shell structure zeolite retained the character of each of the constituent zeolite systems which can be used effectively as a dual/multi-functional catalyst by leveraging the properties of the two different zeolite systems.

[0076] The conclusion drawn from the XRD pattern analysis was also supported by the SEM/EDX analysis. FIG. 5A shows the presence of the constituent elements of the parent *BEA without the presence of Zinc (Zn) while FIG. 5B shows the presence of Zinc after the adsorption of the metal impregnated hollow zeolite particles on the surface of the parent *BEA particle. The SEM/EDX analysis further showed that the core that included the parent *BEA structure had a finite Silica/ Alumina ratio (SAR) which increased from 5.59 to 9.22 after the adsorption of the metal impregnated hollow zeolite particles (Zn Hollow S-l) on the core surface. From FIG. 6A and FIG. 6B which showed the TEM/EDX analysis, it was evident that the core had alumina or aluminum“Al” signature pattern while the shell exhibited no alumina or Al signature pattern. Thus, it was concluded that the core that included the parent *BEA particle had a finite SAR on account of having alumina content while the shell had an infinite SAR on account of the absence of alumina in the shell. The differential value of SAR imparted the dual functional catalytic property of the core/shell structured zeolite, where the alumina containing core can catalyze reactions such as alkylation of an organic substrate while the metal impregnated hollow zeolite shell having infinite SAR can remain inert to alkylation and catalyze dehydrogenation of an alkylated organic substrate using the Zn based catalyst. The SEM and the TEM images further establisheed the core/shell structured zeolite with the parent *BEA core surface being completely covered by the shell. From the Isothermal N2 analysis it was determined that the pore size of the shell is smaller than that of the core, which ensures enhanced selectivity of the type of reactants and molecules which can diffuse through the pores of the zeolite catalyst. [0077] Although embodiments of the present application and their advantages have been described in detail, it should be understood that various changes, substitutions and alterations can be made herein without departing from the spirit and scope of the embodiments as defined by the appended claims. Moreover, the scope of the present application is not intended to be limited to the particular embodiments of the process, machine, manufacture, composition of matter, means, methods and steps described in the specification. As one of ordinary skill in the art will readily appreciate from the above disclosure, processes, machines, manufacture, compositions of matter, means, methods, or steps, presently existing or later to be developed that perform substantially the same function or achieve substantially the same result as the corresponding embodiments described herein can be utilized. Accordingly, the appended claims are intended to include within their scope such processes, machines, manufacture, compositions of matter, means, methods, or steps.