MXPA97000131A - Composition containing crystallized zeolite insitu (lai-i - Google Patents

Abstract

The present invention relates to: The applicant has discovered a new composition containing zeolite and a process for preparing the same. The composition is unique in that the zeolite crystals constituting a layer of the composition are packaged in such a way that the composition is essentially continuous without large-scale voids even when the zeolite layer is of the thickness of < 10 micrometers In this manner, the present invention is directed towards a composition comprising a porous substrate and a layer of zeolite crystals wherein the zeolite crystal layer is a polycrystalline layer with at least 99 percent of the zeolite crystals, having at least one point between adjacent crystals that is < _20 angstrom units, and wherein at least 90 percent of the crystals have widths of from about 0.2 to about 100 microns (preferably, from about 2 to about 50 microns), and wherein at least 75 percent of The crystals have a thickness within 20 percent of the average glass thickness. Preferably, the composition has at most one percent by volume of voids in the zeolite layer. The use of the composition is also described

Description

"COMPOSITION CONTAINING ZEOLITE CRYSTALLIZED IN SITU (LAI-ISC) FIELD OF THE INVENTION The present invention relates to a new composition containing zeolite, its preparation and so.

BACKGROUND OF THE INVENTION U.S. Patent Number 5,110,478 describes the direct synthesis of zeolite membranes. The membranes produced in accordance with the teachings of U.S. Patent No. 5,110,478, were discussed in "Synthesis and Characterization of a Zeolite Membrane Puré" by J.G. Tsikoyiannis and W. Haag, Zeolites (Volume 12, pages 126, of 1992). These membranes are self-stable and are not pre-fixed or attached as layers to any supports. In addition, the membranes have a gradient of crystal sizes across the thickness of the membrane. This gradient prevents the growth of a thin membrane with a minimum number of non-selective permeation pathways.

The zeolite membranes have also grown on supports. See, e.g., "High temperature stainless steel supported zeolite (MFI) membranes: Preparation, Module, Construction and Permeation Experiments" by E.R. Geus, H. vanBekkum, J.A. Moulyin, Microporous Materials, Volume 1, page 137, 1993; Dutch Patent Application Number 91011048; European Patent Application Number 91309239.1 and US Patent Number 4,099,692. All of the membranes prepared above have zeolite crystals of non-uniform size and are non-continuous, exhibiting many voids. It is difficult to obtain functional zeolite membranes from alkaline synthesis routes because the heterogeneous crystals in the membrane require a huge thickness of membrane to seal the pits and void structures that decrease the selectivity of the membrane.

BRIEF DESCRIPTION OF THE DRAWINGS Figure 1 is an electron micrograph showing a cross-sectional view of a zeolite layer grown on the inverted face of a porous alpha-alumina substrate.

Figure 2 is an electron micrograph of a top view of a zeolite layer grown on the inverted face of a porous alpha-alumina substrate. Figure 3 is an X-ray diffraction pattern showing the preferred orientation of a composition of the invention. The X axis is 2 teta and the Y axis is the intensity in CPS. Figure 4 is a schematic view of a zeolite layer on a porous substrate. (A) is the porous substrate, (B) the zeolite layer, (C) a plane of exfoliation, (W) the width at a point along a crystal of zeolite and (T) the thickness of a crystal.

COMPENDIUM OF THE INVENTION The applicant has discovered a new composition of matter containing zeolite and a process for preparing the same. The composition is unique in that the zeolite crystals constituting part of the composition are packaged in a manner such that the zeolite forms a layer which is essentially continuous without large-scale voids even though the zeolite layer is of a thickness of < 10 micrometers Therefore, one aspect of the present invention is directed towards the composition of matter comprised of a substrate (which is also referred to herein as a support) and a polycrystalline layer of zeolite crystals wherein at least 99 percent of the zeolite crystals have at least one point between the adjacent zeolite crystals that is more or less 20 angstrom units and wherein at least 90 percent of the zeolite crystals have widths of about 0.2 to about 100 microns and wherein at least 75 percent of the zeolite crystals have a thickness of within 20 percent of the average crystal thickness. Preferably, the zeolite layer will have at most 1 volume percent voids and the zeolite crystal will vary from about 2 to about 50 microns. Another aspect of the present invention is directed to a process for producing the present composition comprising the steps of: (a) contacting a substrate with a zeolite synthesis mixture; (b) hydrothermally treating the substrate and the zeolite synthesis mixture for a period of time and at a temperature sufficient to form a zeolite layer on the substrate, where the particles on the zeolite layer are prevented from settling on the substrate. synthesis of zeolite; (c) removing any unreacted zeolite synthesis mixture. The term "contact" as used herein includes full and partial immersion. The process further comprises calcining the composition of step (c) at a temperature from about 400 ° C to about 600 ° C for at least about 10 minutes when the zeolite synthesis mixture contains an organic template. Compositions produced in this way are, for example, size exclusion separations, such as separation of molecules from the alcohol dye and separation of oligomer from hexane. In addition, the compositions described herein are often referred to as zeolite membranes in the art and can be used as such.

DETAILED DESCRIPTION OF THE INVENTION The applicant has discovered a novel composition comprising a polycrystalline zeolite layer on a support. The support can be porous or non-porous, preferably, porous support will be used. The zeolite layer can be grown on any of the porous supports including, but not limited to, alumina, titania, cordierite, zeolite, mullite, stainless steel, pyrex, silica, silicon carbide, silicon nitride, carbon, graphite. and mixtures thereof. In addition, non-porous supports will include quartz, silicon, glass, borosilicate glass, dense ceramics, ie, clays, metals, polymers, graphite and mixtures thereof. When supports are used porous, the compositions are useful as sensors or cataly Particularly preferably, the support will be a porous ceramic or a porous metal. The growth of the zeolite layer can be carried out by contacting the substrate in a The synthesis mixture of zeolite for a period of time and at a temperature sufficient to effect the , < crystallization. The hydrothermal treatment, for example, can be done in an autoclave under autogenous pressure. The contact of the substrate must be carried out Such that there is no settlement of the crystals formed in the synthesis mixture during treatment in the autoclave to the substrate. The synthesis mixture, therefore, can be managed in a manner to prevent this settling or sedimentation.

In a preferred embodiment, the zeolite layer is grown on a support that is inverted in the zeolite synthesis mixture. The term "inverted" as used herein means that the zeolite layer is grown on the substrate side oriented from 90 degrees to 270 degrees in the synthesis mixture. In the 180 degree orientation, the side of the substrate toward which the zeolite layer is grown is horizontal and oriented downward. This is referred to as inverted. Preferably, the membrane will be grown on one side oriented at 180 degrees. In the inverted orientation, the surface of the substrate to be coated should be at least 5 millimeters, from the bottom and sides of the container containing the synthesis mixture of zeolite, preferably at least 8 millimeters in its lowest point during the preparation process. The Applicant believes that the investment of the substrate prevents the zeolite crystals, which have been nucleated homogeneously in the zeolite synthesis mixture, from being sedimented into the substrate where the zeolite layer is grown. Therefore, the crystals are not incorporated into the growing zeolite layer or alter the growth process. Therefore, at least 99 percent, preferably, at least 99.9 percent of the crystals in the zeolite layer, have at least one point between the adjacent zeolite crystals remaining at < 20 angstrom units. In the present invention, the spacing between adjacent crystals is graded by a zone of the exfoliation plane and the area of the maximum exfoliation plane, absent of voids or defects, will be < 40 angstrom units. In addition, at least 90 percent, and preferably, at least 95 percent of the zeolite crystals in the zeolite layer have widths of about 0.2 to 100 microns, preferably, 2 to about 50 microns. As used herein, the zone of exfoliation plane is the width of the disordered zone between two adjacent ordered crystals. The zeolite crystals in the zeolite layer are intercropped in the membrane so that non-selective permeation pathways through the membrane are blocked by the most limited approach point between the crystals. Non-selective permeation pathways are taken as being permeation pathways that exist at room temperature, which do not pass through the zeolite crystals. This blocking of the non-permeation pathways exists at room temperature after a template that occludes the pore structure is removed from the zeolite crystals. The templates that are used to grow the zeolite are often removed by a calcination step. From transmission electron microscopy (TEM), the narrowest point of approximation between crystals of less than 20 angstrom units after the template is removed, is established of course. The space between the crystals at this point may contain an inorganic oxide material that restricts the non-selective permeation of the molecules through the membrane. The absence of non-selective permeation pathways can be detected by the ability to avoid permeation at room temperature (-20 ° C) of dye molecules through the membrane, after any template is removed from the pore structure. The dye molecules that can be selected to detect non-selective permeation pathways through the membrane, must have minimum dimensions that are larger than the control aperture through the zeolite and the size of the dye molecule must also be less than 20 angstrom units. The non-selective pathways transport the dye molecules that are larger than the pore size of the zeolite. The dye molecules must be carried in a solution produced with a solvent that can be transported through the pore structure of the zeolite and the zeolite layer in case it is not allowed to pick up foreign contaminants (such as water) before try on It is found that the compositions produced in accordance with the present invention block the permeation of the dye molecules at room temperature through the zeolite layer. All selected dye molecules have sizes less than 20 angstrom units. The lack of room temperature permeation of dye molecules with sizes less than -20 angstrom units, demonstrates that non-selective permeation pathways with sizes less than -20 angstrom units are blocked.

'- It should be noted that this test does not have to be carried A molecule with the dye can be removed and any molecular species detectable can be used having a size of less than 20 angstrom units and larger than the pore size of the zeolite. The advantage of using a molecule of the dye is that it can be easily detected by optical means. The habit of MFI zeolite compositions that are grown in accordance with the present invention preferably exhibits a degree of C orientation (within 30 ° of normal to the surface of the substrate in the film layer). zeolite). More especially, the longer edges (thickness) of at least 75 percent of the crystals are within 30 ° of the perpendicular to the plane of the layer, advantageously, at least 90 percent of the crystals staying within that angle.

A measure of the preferred crystallographic direction of the unit cell and the proportion of the crystals having the longest axis (thickness) perpendicular to the plane of the layer can be obtained by comparing the X-ray diffraction pattern of the layer with that layer. of a randomly oriented zeolite powder. In the case of an MFI type zeolite with predominant C-axis orientation, for example, the longest edge corresponding to the C-axis, the intensity ratio of the maximum 002 to the combined maximum of 200 and 020 is divided between the same ratio for randomly oriented powder; the quotient is called the preferred crystallographic orientation (CPO). Measured in this way, the zeolite layers according to the invention have a CPO of at least one and can have as high a CPO as of 500. The crystals in the zeolite layer vary in thickness from about 2 to about 100 microns, preferably from about 5 to 100 microns, and more preferably from about 30 to about 60 microns, and preferably a maximum of about 30 microns. Even though the crystals can vary in thickness from 2 to 100 micrometers, for any given membrane, 75 percent by volume, preferably 90 percent by volume of the crystals will have glass thicknesses within 20 percent of the glass thickness average. The thickness is defined here as the length of the crystals from the surface of the substrate to the upper edge of the zeolite crystal perpendicular to the substrate. Compositions produced from zeolites other than MFI will also exhibit a degree of customary orientation and / or unitary cell, however, this orientation may not be in the c-direction. For example, orientations A, B and C are possible as well as mixtures thereof. Other orientations are also possible depending on the selected zeolite. The present compositions are virtually free of voids. They preferably exhibit at most about 1 percent volume of voids, preferably less than 0.5 volume percent of voids. The gap as used herein means spaces between the zeolite crystals in the zeolite layer along the exfoliation plane greater than 40 angstrom units. The defects are spaces between adjacent zeolite crystals that extend through the thickness of the zeolite layer. In the present membrane, the total number of defects in the zeolite layer with sizes of > 40 angstrom units is from < 10,000 by 6.45 square centimeters, preferably from < 100 by 6.45 square centimeters. The number of defects having separation between adjacent zeolite crystals greater than about 2,000 angstrom units is < 100 by 6.45 square centimeters, preferably <0.1 by 6.45 square centimeters. Gaps and defects can be detected from cross-sectional images of the zeolite layer produced in the scanning or transmission electron microscope. In the especially preferred case, the zeolite layer will be substantially free of voids and defects. Defects of the type described can be detected in dye permeation experiments. The isolated spots in which the dye penetrates the substrate reveal these defects. Defects can also be determined by examining the cross sections of the zeolite membrane in the scanning electron microscope. The gas permeation can also be used to reveal defects in the membrane. If the permeability of the zeolite layer to nitrogen at room temperature is less than 5 x 10 ~ 6 moles (m2-sec-Pascal) for each micron thickness of the zeolite layer, the membrane can be considered as having a density of defects acceptable. More preferably, the permeability of the zeolite layer to nitrogen at room temperature is less than 5 x 10"^ moles / square meter-sec-Pascal) for each micron thickness of the zeolite layer. present invention are prepared from zeolite synthesis mixtures The zeolite synthesis mixtures are any of the mixtures from which the zeolite crystals are grown and are well known in the art. See, e.g., Handbook of Molecular Sieves, Rosemary Szostak, Van Nostrand Reinhold, NY, 1992 and Zeolite Molecular Sieves, DW Breck, RE Kreiger Publishing Co., Malabar, Florida, 1984, ISBN 0-89874-648-5) For example, for MFI zeolites , the synthesis mixture can be a mixture having a pH of about 8 to about 12 and is easily prepared by those skilled in the art For example, appropriate mixtures include N 2 O, TPABr (tetrapropylammonium bromide), SiO 2 and water. They are made to grow by contacting the support material of the choice in the zeolite synthesis mixture. The synthesis mixture is then heated to a temperature of from about 50 ° C to about 300 ° C, preferably from about 100 ° C to about 250 ° C, and especially preferably at about 180 ° C for a period of about 30 minutes up to approximately 300 hours. Any unwanted growth on the substrate can be easily removed by known techniques. For example, grinding can be used. Undesired growth does not refer to the zeolite layer of the invention, but refers to growth on other surfaces of the substrate. The zeolite layer compositions which can be prepared in accordance with the present invention include silicates, aluminosilicates, aluminophosphates, silicoalumino-phosphates, metalloaluminophosphates, stannosilicates and mixtures thereof. Representative examples of these zeolites are MFI, FAU (including zeolite x, zolite and), zeolite beta; MAZ, LTA, LTL, CHA, AFI, AEL, DEA, AUO, FER, KFI, MOR, MEL, MTW, OFF, TON, AFS, AFY, APC, APD, MTN, MTT, AEL and mixtures thereof, of Preferably the MFI zeolite with a ratio of silicon to alumina greater than 30 will be used including compositions without aluminum. MFI zeolites with Si / Al ratios greater than 30 are referred to herein as silicalite. Some of the aforementioned materials even when they are not true zeolites, are frequently referred to in the literature as such and this term will be used herein to include these materials. The zeolite layer can have either a preferred shape orientation, a preferred crystallographic orientation, or both. The preferred orientations of form or critalográficamente happen due to the control of the relative regimes of nucleation and growth offered by the synthesis procedure. Specifically, during the synthesis, the growth regime can be made to dominate the surface nucleation regime of the new crystals or the incorporation of new crystals. The incorporation of new crystals is defined as the fixation towards the surface of the growing zeolite layer of a crystal formed in the synthesis mixture. Since the growth regime can dominate the reinclusion and incorporation, crystals can grow competitively for extended periods of time without significant addition of new crystals in the growing layer. Since the growing layer is composed of individual crystals and the synthesis method seeks to avoid renucleation and incorporation of crystals, the resulting composition may have preferred shape or crystallographic orientation or both. The shape orientation occurs because the crystals grow with preferred regular habits (or morphology) on the surface of the zeolite layer. A regular habit (or morphology) is taken as being a regularly shaped contour of a specific crystallographic grain in the layer. The contours regularly configured are defined as those that can be adjusted or packaged together so that there are no interconnected spaces or gaps between the crystals. The interconnected gaps will form a pore structure. A few examples of regular habits with regular configurations are columnar, cubic, rectangular and prismatic. The configurations or 5 form spherical, irregular and elliptical are not considered as being regular habits. In a preferred shape orientation, the defined layers will have the same regular habit. In a preferred orientation so that the defined layers will have the same regular habit. This can be measure by dissociating or fracturing the substrate where the layer is grown and examining the cross-sectional morphology of the zeolite layer with a scanning electron microscope. By examining the surface of the zeolite layer that has been grown it can be also provide additional information related to the preferred shape orientation in the layer. A layer with '- preferred shape orientation is taken as being one having more than 90 percent of the crystals within a layer inside the zeolite layer that exhibits regular self-similar habits. The self-similar requirement means that the same regular habit is exhibited within a layer that can be attracted to the electron micrograph of the cross-section of the zeolite layer, however, even when the shapes are the same, not all have the same size. Due to the growth mechanism of the zeolite layer, there may be a preferred shape orientation in the bottom (base) of the layer and another preferred orientation of the shape in the attracted layer near the surface. An example of this is an MFI zeolite layer that has a columnar habit at the base of the layer and a rectangular habit on the surface of the layer. Many layers of MFI zeolite that are grown in accordance with the present invention will exhibit only one habit through the thickness of the zeolite layer. Usually, the MFI zeolite layers that are grown in accordance with the present invention exhibit only one habit through the thickness of the zeolite layer. Usually, the MFI zeolite layers with a preferred C-axis orientation exhibit a columnar habit (or morphology) across the entire thickness of the other zeolite layer. Frequently, the layers with preferred shape orientation will have a preferred crystallographic orientation. The substrate in which the zeolite layer is grown may be porous or non-porous. If the substrate is porous, it will be a porous material throughout its thickness. Preferably, an inorganic oxide or stainless steel will be used. The porous substrate, therefore, may be a ceramic, metal, carbide, polymer or mixture thereof. The porous substrate, therefore, may have a uniform pore size therethrough or may be asymmetric, having a larger pore structure through the volume of the substrate, with a smaller pore structure on the surface where the zeolite layer will grow. The pore size of the substrate is regulated by mass transfer considerations. It is preferred that the pore structure and thickness of the substrate are selected in such a way that the mass transfer resistance does not limit the flow of material penetrating through the zeolite membrane during use. The porous substrate, therefore, will exhibit a porosity of about 5 percent to about 70 percent, preferably, about 20 percent to about 50 percent and an average pore size of about 0.004 micrometer to about 100 micrometers, preferably, from about 0.05 micrometer to about 2 microns. It is preferred that the surface of the substrate, porous or non-porous, in which the zeolite layer is grown is smooth. The roughness in the substrate leads to defects in the zeolite layer. The substrate should have an average roughness with an amplitude of less than 10 micrometers with an elongation of the roughness less than 1: 1. It is preferred that the average roughness of the substrate is less than .5 micrometer with a roughness elongation of less than 1: 1. Even when non-porous substrates can be used, porous substrates are preferred. Once the zeolite layer has been grown, the substrate, with the zeolite layer fixed, can preferably be washed with water for a certain time and at a temperature sufficient to remove any amount of the unreacted zeolite synthesis mixture. during the hydrothermal treatment. Thus, the washing can be carried out at a temperature of about 15 ° C to 100 ° C, preferably about 80 ° C to about 100 ° C for at least 10 minutes, preferably at least 6 hours. Excessive washing for longer periods will not affect the ability to separate the compositions. In addition, any of the liquids or solutions capable of removing the excess of the zeolite synthesis mixture can be used. Once it has been washed, if the zeolite synthesis mixture contains an organic template, the composition is calcined at a temperature of about 400 ° C to 600 ° C, for at least one hour, preferably at least about 6 hours. hours. Longer calcination times will not affect the operation of the membrane.

The compositions are useful for separation processes, whereby the feedstock derived from petroleum, natural gas, hydrocarbons or air, comprising at least two molecular species is contacted with the composition of the invention and, at least , a molecular species of the feedstock is separated from the feedstock, by means of the composition and wherein the materials of the hydrocarbon feed are coal, bitumen and kerogen-derived feedstocks. Specifically, the following table shows some possible feedstocks derived from petroleum, natural gas, air or hydrocarbons and the molecular species separated from them, by using the present compositions. The table is not intended to be limiting.

MOLECULAR SPECIES MATERIAL SEPARATE FOOD Mixed xylenes (ortho, para, meta) and ethylbenzene Paraxylene Mixture of hydrogen, H2S and ammonia Hydrogen Mixture of normal substances and isobutanes Normal butane Mixture of normal substances and isobutenes Normal butene Kerosene containing normal paraffins of normal nas from Cg to C ^ g C9 to Cis Nitrogen and oxygen mixture Nitrogen (or oxygen) Mixture of hydrogen and methane Hydrogen Mixture of hydrogen, ethane and ethylene Hydrogen and / or ethylene Coke naphtha containing olefins and normal paraffins Olefins and paraffins from C5 to C ^ or normal from C5 to C ^ g Mixtures of methane and ethane containing argon, helium, neon or nitrogen Helium, neon and / or argon Products catalytic reformers of intermediate reactor containing hydrogen and / or gases Hydrogen and / or light light gases (C ^ - C7) Fluid catalytic thermal fractionation products containing H2 and / or gases Hydrogen and / or light light gases Naphtha containing paraffins Normal normal paraffins from C5 to C ^ Q C5 a Cio Light coke diesel containing olefins and paraffins Normal olefins and paraffins from Cg to C ^ g from Cg to C ^ g Mixture of normal substances and isopentanes Normal Pentane Mixture of normal substances and isopentenes Normal Pentene Mixture of ammonia, hydrogen and nitrogen Hydrogen and nitrogen Mixture of A10 aromatics (10 v.eg, paradiethylbenzene carbon atoms) (PDEB) Butenes mixed n-butenes Sulfur and / or nitrogen compounds H2S and / or NH3 Mixtures containing benzene (toluene) Benzene H2, propane, propylene Hydrogen, and / or propylene Applicants believe that molecular dysfunction is responsible for the above-mentioned separations. In addition, the compositions can be used to effect a chemical reaction to yield at least one reaction product by contacting the feedstocks as described above or below with the compositions having a catalyst incorporated within them. the zeolite layer, or support or placing the catalyst in close proximity near the composition to form a module. A module would react the feed material just prior to its entry into the composition or just after it leaves the composition. In this way, at least one reaction product or reagent can be separated of the feeding materials. The catalysts that are selected for specific process fluids are well •. ' known to those skilled in the art and can be easily incorporated into the present compositions or formed into modules with the compositions by a person skilled in the art. The following table represents some of the possible feed materials / processes in addition to those previously mentioned that can be reacted and some possible products that can be rendered. Picture is not intended to be limiting.

FOOD PRODUCT MATERIAL / RENDED PROCESS Mixed xylenes (for, ortho, paraxylene and / or meta) and ethylbenzene ethylbenzene Dehydrogenation of ethane in ethylene Hydrogen and / or ethylene Dehydrogenation of ethylbenzene in styrene Hydrogen Dehydrogenation of butanes in butenes (iso and normal) Hydrogen Dehydrogenation of propane in propylene Hydrogen and / or propylene Dehydrogenation of normal paraffin from CIO to C18 in olefins Hydrogen Decomposition of Hydrogen Sulfide Hydrogen Hydrogen dehydrogenation, light reformation / aromatization hydrocarbons (C ^ a C7) Dehydrogenation / aromatization of light petroleum gas Hydrogen Butenes mixed n-butenes The supported zeolite layer of the invention can be extended in these separations without the problem of damage by contact with the materials to be separated. In addition, many of these separations are carried out at elevated temperatures, as high as 500 ° C, and it is an advantage of the supported layer of the present invention that it can be used at these elevated temperatures. Additional separations that can be carried out using the composition according to the invention include, for example, separation of normal alkanes from co-boiling hydrocarbons, for example, normal alkanes of iso-alkanes such as mixtures of 4 carbon atoms. to 6 carbon atoms and n-alkanes of 10 carbon atoms to 16 carbon atoms of kerosene; separation of aromatic compounds from one another, especially the separation of aromatic isomers of 8 carbon atoms from one another, more specifically, para-xylene from a mixture of xylenes and optionally ethylbenzene and the separation of aromatics from different carbon numbers , for example, mixtures of benzene, toluene and aromatics of 8 carbon atoms mixed; the separation of aromatic compounds from aliphatic compounds, especially aromatic molecules with carbon atoms of 10 carbon atoms (naphtha scale); separation of olefinic compounds from saturated compounds, especially light alkenes from alkane / alkene mixtures, more especially ethane ethane and propane propene; removing hydrogen from hydrogen-containing streams, especially from light refinery and petrochemical gas streams and more particularly from 2-carbon and lighter components; and alcohols of aqueous streams; alcohols of other hydrocarbons, particularly alkenes and alkanes which may be present in mixtures formed during the manufacture of alcohols and the separation of heteroatomic compounds from hydrocarbons, such as alcohols and sulfur-containing materials, such as H2S and mercaptans. The present invention therefore also provides a process for the separation of a fluid mixture comprising contacting the mixture with a face of a layer according to the invention under conditions such that at least one component of the mixture has a different constant state permeability through the layer from that of another component and recovering one component or mixture of the components from the other surface of the layer.

The invention further provides a process for catalyzing a chemical reaction comprising contacting a feed material with a layer according to the invention which is a catalytically active form under conditions of catalytic conversion and recovering a composition comprising, at least , a conversion product, advantageously at a concentration that differs from its equilibrium concentration - - in the reaction mixture. For example, a mixture rich in P-xylene from the reactor or a reactor product in a xylene isomerization process; the aromatic and aliphatic hydrogen compounds in a reforming reactor, the removal of hydrogen from refinery and chemical processes, such as dehydrogenation of alkane in the formation of alkenes, dehydrocyclization of alkane / alkene in the formation of aromatic compounds (e.g., Cyclar), dehydrogenation of ethylbenzene in styrene. The invention further provides a process for catalyzing a chemical reaction comprising putting in Contact a reagent of a bimolecular reaction with a face of a layer according to the invention, that is, in the form of a membrane and in an active catalytic form, under conditions of catalytic conversion and controlling the addition of a second reagent by diffusion from the opposite face of the layer, in order to more precisely control the reaction conditions. Examples include controlling the addition of ethylene, propylene or hydrogen to benzene in the formation of ethylenebenzene, eumeno or cyclohexane, respectively. The invention further proposes the separation of a feedstock, as described herein, wherein the separated species reacts as it leaves the composition as it passes through the composition and thus forms another product. It is believed that this increases the driving force for diffusion through the zeolite layer. The catalytic functions can be incorporated into the present compositions. When a catalytic function is incorporated into the composition, it can be used as an active element in a reactor. The different reactor architectures can be constructed depending on the location of the catalytic site in the composition. In one case, the catalytic function can be placed within the zeolite layer, while in another case, the catalytic function can be placed within the support, and in another case, the catalytic function can be distributed through the support and the zeolite layer . In addition, the catalytic function can be incorporated into a reactor by placing conventional catalyst particles near one or more of the surfaces of the composition in such a way that the specific products or reagents are continuously and selectively removed or added to the reaction zone through the catalyst. of the reactor. Impregnation with catalytically active metals, such as the noble metals of Group VIII, e.g., Pt, can impart the catalytic function to the composition. The catalytically active metals can be incorporated by techniques known in the art, such as incipient moisture. The amount of Group VIII noble metal to be incorporated will vary from about 0.01 percent to about 10 percent by weight. Some specific reaction systems where these compositions would be advantageous for selective separation, either in the reactor or in a reactor effluent include: the selective removal of the para-xylene-rich mixture from the reactor, the reactor product, the reactor feed or other sites in a xylene isomerization process; the selective separation of aromatic fractions or molecule-rich currents of the aromatic compound specific to catalytic reforming or other processes for the generation of aromatic compounds, such as dehydrocyclization processes of alkane and alkene (e.g., C3 to C7 paraffins to compounds aromatics from processes, such as Cyclar), thermo-fractionation processes of methanol to gasoline and catalytic; selective separation of benzene-rich fractions from refinery and chemical plant streams and processes; selective separation of olefins or specific olefin fractions from refinery and chemical processing units including thermal catalytic thermofraction, olefin isomerization processes, methanol to olefin processes, naphtha to olefin conversion processes, alkane dehydrogenation processes, such as dehydrogenation of propane in propylene, selective removal of hydrogen from refinery and chemical streams and processes, such as catalytic reforming, dehydrogenation of alkane, catalytic thermofraction, thermal thermocracking and dehydrocyclization of light alkane / alkene, dehydrogenation of ethylbenzene, paraffin dehydrogenation , selective separation of molecular isomers in processes such as butane isomerization, paraffin isomerization, olefin isomerization, selective separation of alcohols from aqueous streams and / or other hydrocarbons. The following examples are for illustration and are not intended to be limiting.

Examples 1. Materials The hydrothermal experiments were carried out using mixtures of the following reagents: NaOH (Baker), Al (N? 3) 3, 9H2? (Baker), Ludox AS-40 (Dupont), tetrapropylammonium bromide (98 percent Aldrich) and distilled water. They were used for the support of the zeolite layers, porous alumina substrates and stainless steel.

The average pore size and porosity of the alumina substrate was approximately 800 angstrom units and 32 percent, respectively. Porous sintered stainless steel substrates of Mott (0.25 micrometer) and Pall (M020, 2 microns) were then obtained. All substrates were cleaned with acetone in an ultrasonic bath, dried at 120 ° C and then cooled to room temperature before use. 2. Hydrothermal Reaction MFI membranes were prepared from two different batch mixtures, one containing only silica to produce MFI of high silica content and the other with alumina added to produce ZSM-5, having the general formulation x M2?: 10 SÍO2: z Al2? 3. * pTPABr: and H2O; M can be NA, K, Rb, and Cs, x is varied from 0.1 to 0.15 and p is varied from 0.2 to 1. All the results shown in the following section have the composition of 0.22 Na2?: 10 SÍO2: 0A1203-.280 H2?: 0.5 TPABr (tetrapropylammonium bromide), with the exception of the ZSM-5 sample, which contained 0.05 of AI2O3, 1.74 grams or TPABr and 0.45 gram of NaOH (50 weight percent) were dissolved in 52 milliliters of distilled water with agitation. To this solution was added with stirring 18.8 grams of Ludox AS-40 for at least 15 minutes, until a uniform solution formed. The substrates were placed inverted (180 degree orientation) in a Teflon-lined reaction vessel supported on a stainless steel wire frame. The distance between the substrate and the bottom of the reactor was at least 5 millimeters. The synthesis solution was then emptied into the reactor to cover the entire substrate. The autoclave was sealed and placed in an oven and preheated to the desired temperature. The reaction pumps were removed from the furnace after the reaction and cooled to room temperature. The coated substrates were washed with hot water for at least 6 hours and then calcined at a temperature of 500 ° C for 6 hours in air, the heating rate was controlled at 10 ° C per hour. 3. Analysis The resulting membranes were characterized by X-ray diffraction, electron microscopy and permeability measurements.

Results and Discussion 1. Products The following table shows some of the typical examples synthesized under different experimental conditions, such as the reaction time and the substrate. TABLE 1 PORO TEMPERATURE SIZE SAMPLE @SUBSTRATO MICROMETER REACTION (° C) 1 alumina 0.08 180 2 alumina 0.08 180 3 alumina 0.08 180 4 SS 0.25 180 5 SS 0.25 180 6 SS 0.25 180 7 alumina 0.08 158 8 alumina 1.0 158 9 SS 0.25 158 10 SS 2.0 158 TABLE 1 (CONTINUED) CAPA THICKNESS TIME REACTION, OF ZEOLITE AXIS C SAMPLE HOURS (MICROMETERS) RESULT 1 4 4 CPO MFI 2 8 12 CPO MFI 3 18 30 CPO MFI 4 4 4 CPO MFI 8 11 CPO MFI 6 20 30 CPO MFI 7 64 45 CPO MFI 8 64 45-50 CPO MFI 9 64 50 CPO MFI 64 50 CPO MFI @ alumina: pore size of 0.08 micrometer and 1 micrometer; SS = stainless steel, Pall Corporation, PMM Quality M020 (2 micrometers) and Mott Corp (0.25). CPO - Preferred Crystallographic Orientation

Claims (29)

R E I V I N D I C A C I O N E S;

1. A composition comprising a substrate and a polycrystalline layer of zeolite crystals wherein, At least, 99 percent of the zeolite crystals have at least one point between adjacent crystals that is < 20 angstrom units, and wherein at least 90 percent of the crystals have widths of approximately .2 to approximately 100 microns, and in 10 where at least, 75 percent of the crystals have a thickness within 20 percent of the average glass thickness.

2. A composition according to claim 1, wherein the substrate is a substrate 15 porous which is selected from the group consisting of stainless steel, alumina, courdierite, mullite, titania, pyrex, '-. silica, silicon nitride, silicon carbide, zeolite, carbon, graphite and mixtures thereof.

3. A composition according to claim 1, wherein the zeolite crystals are from about 2 to about 100 microns thick.

4. A composition according to claim 3, wherein the thickness of the zeolite crystal varies from about 5 to about 100 microns.

A composition according to claim 1, wherein the substrate is a non-porous substrate selected from the group consisting of quartz, glass, borosilicate glass, clay, metal, silicon, polymer, graphite, dense ceramic and mixtures thereof.

6. A composition according to claim 1, wherein the zeolite crystals exhibit a preferred cryographic orientation.

7. A composition according to claim 6, wherein when the zeolite crystals are MFI crystals, the zeolite crystals have a C orientation within 30 ° of normal orientation to the surface of the substrate.

A composition according to claim 2, wherein the substrate has a porosity of about 5 percent to about 70 percent and a pore size distribution of about 0.004 to 100 micrometers.

9. A composition according to claim 1, wherein the substrate has an average roughness with an amplitude of less than 10 microns with a roughness elongation of less than 1: 1.

10. A composition according to claim 1, wherein the crystals have widths of about 2 to about 50 microns.

11. A composition according to claim 1, wherein the zeolite crystal layer is selected from the group consisting of silicates, aluminosilicates, aluminophosphates, siliconalumino-phosphates, metalloaluminophosphates, stannosilicates, MFI, FAU, zeolite and, zeolite X, MAX, LTA, CHA, AFI, AEL, BEA, EUO, FER, KFI, MOR, MEL, MTW, OFF, TON, AFS, AFY, APC, APD, MTN, MTT, AEL and mixtures thereof.

12. A composition according to claim 11, wherein the zeolite crystal layer is a layer of MFI zeolite crystals.

13. A composition according to claim 1, wherein the zeolite layer has less than 1 volume percent voids.

14. A composition according to claim 13, wherein the zeolite layer has less than 0.5 volume percent voids.

15. A composition according to claim 1, wherein the zeolite layer has less than 10,000 defects of a size greater than 40 angstrom units per 6.45 square centimeters.

16. A method for preparing a composition comprising the steps of: (a) contacting a substrate with a zeolite synthesis mixture; (b) hydrothermally treating the substrate and the zeolite synthesis mixture for a period of time and at a temperature sufficient to form a zeolite layer in the substrate, in which the sedimentation of the particles produced from the mixture is avoided. synthesis of zeolite during the treatment to the zeolite layer; 15 (c) removing any unreacted zeolite synthesis mixture. '

17. A method according to claim 16, wherein the composition is calcined at a temperature of 400 ° C to 600 ° C for at least 30 minutes. 20 minutes when the zeolite synthesis mixture contains an organic template.

18. A method according to claim 16, wherein the substrate is oriented in such a way that the zeolite layer is grown on the side 25 of the substrate oriented from 90 ° to 270 ° in the synthesis mixture, and in the 180 ° orientation, the zeolite layer is grown on the horizontal downward facing side.

19. A composition according to claim 1, wherein the composition is incorporated therein, from about 0.1 percent to about 10 percent of a noble metal.

20. A separation process comprising contacting a feedstock derived from petroleum, natural gas, air or hydrocarbons comprising at least two molecular species with a composition comprising a substrate and a layer of polycrystalline zeolite crystals, in wherein at least 99 percent of the zeolite crystals have at least one point between the adjacent crystals that is at a distance of < 20 angstrom units and wherein at least 90 percent of the crystals have widths of about 0.2 to about 100 microns and wherein at least 75 percent of the crystals have a thickness within 20 percent of the thickness of the crystals. average crystal, wherein at least one molecular species of the feedstock is separated from the feedstock by the composition, and wherein the feedstock of hiderocarbide are selected from the group consisting of coal, bitumen, kerogen and mixtures of the same.

21. A process according to claim 20, wherein the molecular species is separated through molecular diffusion.

22. A process according to claim 20, wherein the feedstock is selected from the group consisting of mixed xylenes and ethylbenzene; hydrogen, H2S and ammonia; mixtures of normal substances and isobutanes; mixtures of normal substances and isobutenes; normal paraffins containing kerosene; mixtures of nitrogen and oxygen; mixtures of hydrogen and methane; mixtures of hydrogen, ethane and ethylene; mixtures of hydrogen, propane and propylene; Coke naphtha containing mixtures of 5 carbon atoms to 10 carbon atoms containing argon, helium, neon or nitrogen; products of the catalytic reformer of the intermediate reactor; fluid catalytic thermocracking products; light coke gas oil; mixtures of normal materials and isopentanes; mixtures of normal materials and isopentenes; mixtures of ammonia, hydrogen and nitrogen; mixtures of aromatic compounds of 10 carbon atoms, "mixtures of butenes", mixtures of sulfur and nitrogen compounds; mixtures of sulfur compounds; mixtures of nitrogen compounds; and mixtures thereof.

23. A process for catalyzing a chemical reaction comprising contacting a reaction stream with a composition consisting of a substrate and a polycrystalline layer of zeolite crystals, wherein at least 99 percent of the zeolite crystals have at least minus one point between the adjacent crystals that is < 20 angstrom units and wherein at least 90 percent of the crystals have widths of about 0.2 to about 100 microns and wherein at least 75 percent of the crystals have a thickness within 20 percent of the average thickness of the crystals. crystal .

24. A process according to claim 23, wherein a catalyst forms a module with the composition or is contained within the composition.

25. A process according to claim 24, wherein the feedstock comprises mixed xylenes and ethylbenzene; ethane; ethylbenzene; butans; propane; normal paraffins of 10 carbon atoms to 18 carbon atoms; H2S; catalytic reforming currents; light petroleum gases (LPG); sulfur and hydrogen compounds; nitrogen compounds; mixed butenes and mixtures thereof.

26. A process according to claim 25, wherein when the feed material is reacted with the composition, a reactant or a reaction product is obtained.

27. A composition obtainable by the method of claim 16.

28. A process for catalyzing a chemical reaction comprising contacting a reagent of a bimolecular reaction mixture with a face of a composition comprising a substrate and a polycrystalline layer of zeolite crystals, wherein at least 99 percent of the zeolite crystals have at least one point between adjacent crystals that is < 20 angstrom units, and wherein at least 90 percent of the crystals have widths of about .2 to about 100 microns, and wherein at least 75 percent of the crystals have a thickness within 20 percent of the average glass thickness that is in catalytic form, under catalytic conversion conditions, and control the addition of a second reagent by diffusion from the opposite face of the structure.

29. A process according to claim 20, wherein the composition absorbs at least one molecular species of the feedstock. SUMMARY OF THE INVENTION The applicant has discovered a new composition containing zeolite and a process for preparing the same. The composition is unique in that the zeolite crystals constituting a layer of the composition are packaged in such a way that the composition is essentially continuous without large-scale voids even when the zeolite layer is of the thickness of < 10 micrometers In this way, the present invention is directed towards a composition comprising a porous substrate and a zeolite crystal layer wherein the zeolite crystal layer is a polycrystalline layer with at least 99 percent of the zeolite crystals, having at least one point between adjacent crystals that is < 20 angstrom units, and wherein at least 90 percent of the crystals have widths of about 0.2 to about 100 microns (preferably, about 2 to about 50 microns), and wherein at least 75 percent of The crystals have a thickness within 20 percent of the average glass thickness. Preferably, the composition has at most one percent by volume of voids in the zeolite layer. The use of the composition is also described.