WO2002038259A1

WO2002038259A1 - Zeolite membranes, method for the production thereof and use of zeolite membranes

Info

Publication number: WO2002038259A1
Application number: PCT/EP2001/011756
Authority: WO
Inventors: Gerhard HÖRPEL; Christian Hying; Franz-Felix Kuppinger; Gerhard Tomandl; Jenny Hoffmann
Original assignee: Creavis Gesellschaft Für Technologie Und Innovation Mbh
Priority date: 2000-11-09
Filing date: 2001-10-11
Publication date: 2002-05-16
Also published as: DE10055611A1

Abstract

The invention relates to an inorganic membrane which comprises a layer of crystals displaying molecular screening characteristics and acts as an active separating layer. The invention also relates to a method for the production of such membranes and the use thereof. Membranes are used for various chemical or physical processes e.g. material separation processes. Such membranes are often polymer-based.Said polymers are not particularly resistant to solvents and high temperatures. The aim of the invention is to provide an inorganic membrane. The inventive inorganic membrane consists of inorganic components and is characterized by a high degree of stability with respect to acids and high temperatures. According to the invention, a support material which is permeable with respect to materials is used and a crystal solution which contains the components for synthesis of zeolites is introduced therein. An active separating layer is crystallized in the support material as a result of said crystal solution. The inventive membrane can be used for the separation of materials, especially for separating gases. One advantage of the inventive membrane is that it can be embodied in a flexible form.

Description

Zeolite embrane, process for its production and the use of the zeolite membrane

Zeolite membranes, a process for their production and the use of the zeolite membrane are claimed.

A problem that frequently occurs in industrial processes is the separation of substances, in particular the separation of mixtures of liquids or gases. Classic separation processes, such as Distillation, extraction or adsorption are relatively complex. Separation processes using membranes are used in particular for gas separation. Organic membranes are currently frequently used, although these can only be used to a limited extent because their chemical, mechanical and thermal stability are limited.

More recently, ceramic materials that can be used as membranes have been developed that have sufficient stability with regard to chemical, mechanical or thermal influences. So that these membranes can be used for gas separation, they must have a defined maximum pore size.

Materials with defined maximum pore sizes include zeolites. Depending on the composition and / or production process, aluminosilicates or zeolites can be produced which have a specific pore size. Because zeolites have a defined pore size, they are suitable for separating compounds or molecules, which is why such compounds are often also called molecular sieves. By combining zeolites with inorganic membranes, zeolite membranes can be produced that are suitable for the separation of certain gas mixtures.

Numerous attempts to produce and use combinations of membranes and zeolites have been described. Such combined membranes are usually produced by a process in which a zeolite layer is crystallized onto the membrane on an inorganic membrane by hydrothermal synthesis in a crystallization solution after heterogeneous nucleation. For the separation of mixtures of n-butane and isobutane, separation factors of> 10 at 100 kPa and 200 ° C for silicalite-1 and ZSM-5 membranes are given as the criterion for good membrane quality. A silicalite-1 membrane crystallized onto a planar α-Al ₂ O ₃ support showed a separation factor of 11 (Vroon, Keizer, Burggraaf, Verweij; J. Membr. Sei. 144 (1998) 65-76). Giroir-Fendler et al., Stud. Surf achieved similarly good results. Be. Catal. 111 (1996) 127 and Kusakabe et al. J. Membr. Be. 116 (1996) 39, on tubular α-Al ₂ O ₃ supports.

Such membranes are already being sold commercially to a small extent. Mitsui Engineering & Shipbuilding Co., for example, in European patent application EP 0659469 describes the production of zeolite A membranes by crystallizing zeolites on a porous support, preferably an alumina support. In the pervaporative separation of mixtures of ethanol and water, separation factors greater than 10,000 are achieved with this membrane at 105 ° C at a flow rate of approx. 4 kg / m ² -h-bar.

However, the industrial use of such membranes has not yet established itself, since the manufacture of such membranes is time-consuming and cost-intensive despite acceptable separation performance. This is due in particular to the fact that the number of membrane defects due to synthesis can only be minimized by repeating the manufacturing process, ie the crystallization, several times. This also leads to an increase in the membrane thickness, thus to a decrease in the flow rates in the separation of materials and thus the use of this membrane in separation processes becomes ineffective.

In recent times attempts have been made to synthesize zeolite membranes within a ceramic layer. Hofϊmann et al. at the 12th German Zeolite Conference 2000 on a poster that tested a new process with which it should be possible to synthesize a zeolite membrane in the pores of a porous support. In this method, a zeolite synthesis solution is infiltrated into the carrier and only then is the sample subjected to hydrothermal treatment. No further details were given about the manufacturing parameters. It was also not possible to prove that the membranes produced in this way are suitable for the separation of liquids or gases. Moueddeb et al. (submitted to J. Membr. Sei.), like PCT application WO 95/29751, describe the production of a zeolite membrane in the pores of a cylindrical support based on aluminum oxide. The examination shows that it is possible to produce an almost defect-free zeolite membrane in the pores of a cylindrical carrier based on aluminum oxide.

The methods described for the production of zeolite membranes have the disadvantage that they lead to zeolite membranes which can only be subjected to very low mechanical loads. In addition, the production of such zeolite membranes is relatively complex and therefore expensive, which is why an industrial use of such membranes, e.g. for gas separation, has not yet taken place.

The object of the present invention was therefore to provide a zeolite membrane which is relatively insensitive to mechanical loads and is simple and inexpensive to manufacture, and to provide a process for the production thereof.

Surprisingly, it was found that by introducing a crystallization solution into a permeable carrier material and then crystallizing a separation-active layer in the carrier material, a ceramic membrane can be obtained which has improved properties with regard to mechanical and chemical stability than conventional membranes, the properties of which differ, inter alia, from used crystallization solution and thus eg depend on the type of zeolite produced.

The present invention therefore relates to a membrane which has a permeable carrier material and a release-active layer according to claim 1, which is characterized in that the membrane has at least one release-active layer in the permeable carrier material.

The present invention also relates to a membrane with at least one release-active layer in a permeable carrier material according to claim 2, which by introducing a crystallization solution, which has the components necessary for the synthesis of the release-active layer, into a carrier material, the ones present in the pores of the carrier material Gases from the crystallization solution from the carrier material are displaced, and subsequent crystallization of the separation-active layer in the carrier material is available.

The present invention also relates to a method for producing a membrane according to at least one of claims 1 to 21, which is characterized in that a release-active layer is synthesized in a permeable carrier material.

The present invention also relates to the use of a membrane according to at least one of claims 1 to 21 for the separation of compounds or molecules which have an average size of less than 10 μm.

The membrane according to the invention has the advantage that, depending on the intended use, it is significantly more durable than the membrane available to date with properties similar to those of the membrane according to the invention.

The membrane according to the invention also has the advantage that inexpensive materials can be used as carrier materials into which the layer of separating crystals is introduced.

The membranes according to the invention are additionally distinguished by excellent separation properties. Since the separation-active layer is very thin, the membrane according to the invention has a large permeate flow despite the high selectivity of the separation. The good separation behavior is also achieved in that the separation-active crystal layer is so dense at its crystal grain boundaries that no unwanted material passages are possible.

A further advantage of the membrane according to the invention is that the membrane is flexible and bendable, depending on the carrier material used, without the good separation properties being lost. It is also particularly advantageous that the membrane according to the invention can be produced very inexpensively even in large areas by the method according to the invention.

The manufacturing process for the membrane according to the invention is simple and economical since it does not require any special technical effort.

The membrane according to the invention is described below by way of example, without the membrane being restricted to these embodiments.

The membrane according to the invention, which has a permeable carrier material and at least one separating layer, is characterized in that the membrane has at least one separating layer in the permeable carrier material.

Membranes according to the invention with at least one separation-active layer in a permeable carrier material are introduced into a carrier material by introducing a crystallization solution which has the components necessary for the synthesis of the separation-active layer, the gases present in the pores of the carrier material being displaced from the carrier material by the crystallization solution. and subsequent crystallization of the separation-active layer in the carrier material.

For the purposes of the present invention, a membrane is understood to be a material which is suitable for separating substances and is therefore permeable to particles up to a certain size and impermeable to larger particles.

For the purposes of the present invention, the separating layer is understood to be the layer on which the actual material separation takes place. The maximum pore size of the separation-active layer therefore determines the size of the particles for which the membrane is just permeable. The permeable carrier material present in the membrane according to the invention can comprise metal, glass, ceramic or a combination of these materials. The permeable carrier material preferably has woven fabrics, nonwovens, sintered powder or sintered fibers made of metal, glass, ceramic or a combination of these materials. Likewise, the permeable carrier material can have woven or non-woven fabrics made of carbon woven fabric. The permeable carrier material can also be a material which itself uses as a microfiltration membrane, ultrafiltration membrane, nanofiltration membrane or gas separation membrane can be. It is also possible to use material combinations in which a micro, nano and / or ultrafiltration membrane has been applied as a layer on and / or in a support or in and / or on a micro, nano and / or ultrafiltration membrane.

The production of such materials or material combinations is e.g. described in PCT applications WO 96/00198, WO 99/15262 or WO 99/15272. All of these materials are based on composite materials that have an inorganic or ceramic material applied to and in a porous carrier. The membrane according to the invention can have both the composite materials described below and the supports on which they are based as the carrier material.

The composite materials have at least one perforated and permeable support as the basis. On at least one side of the carrier and in the interior of the carrier, the carrier has at least one inorganic component which essentially has at least one compound composed of a metal, a semimetal or a mixed metal with at least one element from the 3rd to 7th main group. The interior of a carrier is understood to be the cavities or pores in a carrier.

The composite materials can, by applying a suspension which has at least one inorganic component and a sol comprising at least one, a compound of at least one metal, a semi-metal or a mixed metal with at least one element of the 3rd to 7th main group, on a perforated and permeable carrier, and by at least one heating, in which the suspension having at least one inorganic component is solidified on or in or on and in the carrier.

However, the composite materials can also be obtained by vapor deposition, impregnation or coprecipitation.

The composite materials can be permeable to gases, solids or liquids, in particular to particles with a size of less than 10 nm. The spaces in the Composite materials can be pores, meshes, holes, crystal lattice interstices or cavities. The carrier can have at least one material selected from carbon, metals, alloys, glass, ceramics, minerals, plastics, amorphous substances, natural products, composite materials or from at least a combination of these materials. The carriers, which may have the aforementioned materials, may have been modified by a chemical, thermal or mechanical treatment method or a combination of the treatment methods. The composite materials preferably have a carrier which has at least one metal, a natural fiber or a plastic which has been modified by at least one mechanical deformation technique or treatment method, such as, for example, drawing, upsetting, milling, rolling, stretching or forging. The composite materials very particularly preferably have at least one carrier which has at least woven, bonded, matted or ceramic-bonded fibers, or at least sintered or bonded shaped bodies, balls or particles. In a further preferred embodiment, a perforated carrier can be used. Permeable supports can also be those which become permeable or have been made by laser treatment or ion beam treatment.

It can be advantageous if the carrier fibers from at least one material selected from carbon, metals, alloys, ceramics, glass, minerals, plastics, amorphous substances, composites and natural products or fibers from at least a combination of these materials, such as asbestos, glass fibers , Rock wool fibers, carbon fibers, metal wires, steel wires, polyamide fibers, coconut fibers, coated fibers. Carriers are preferably used which have at least woven fibers made of metal or alloys. Wires can also serve as fibers made of metal. The composite materials very particularly preferably have a carrier which has at least one fabric made of steel or stainless steel, such as fabric made from steel wires, steel fibers, stainless steel wires or stainless steel fibers by weaving, which preferably has a mesh size of 5 to 500 μm, particularly preferably mesh sizes of 50 to 500 μm and very particularly preferably have mesh sizes of 70 to 120 μm. The carrier of the composite materials can also have at least one expanded metal with a pore size of 5 to 500 μm. According to the invention, however, the carrier can also have at least one granular, sintered metal, a sintered glass or a metal fleece with a pore size of 0.1 μm to 500 μm, preferably 3 to 60 μm.

The composite materials preferably have a carrier which contains at least aluminum, silicon, cobalt, manganese, zinc, vanadium, molybdenum, indium, lead, bismuth, silver, gold, nickel, copper, iron, titanium, platinum, stainless steel, steel, brass, an alloy of these materials or a material coated with Au, Ag, Pb, Ti, Ni, Cr, Pt, Pd, Rh, Ru and / or Ti.

The inorganic component present in the composite materials can have at least one compound of at least one metal, semimetal or mixed metal with at least one element from the 3rd to 7th main group of the periodic table or at least a mixture of these compounds. The compounds of the metals, semimetals or mixed metals can have at least elements of the subgroup elements and the 3rd to 5th main group or at least elements of the subgroup elements or the 3rd to 5th main group, these compounds having a grain size of 0.001 to 25 μm. The inorganic component preferably has at least one compound of an element of the 3rd to 8th subgroup or at least one element of the 3rd to 5th main group with at least one of the elements Te, Se, S, O, Sb, As, P, N, Ge , Si, C, Ga, AI or B or at least one connection of an element of the 3rd to 8th subgroup and at least one element of the 3rd to 5th main group with at least one of the elements Te, Se, S, O, Sb, As , P, N, Ge, Si, C, Ga, Al or B or a mixture of these compounds. The inorganic component particularly preferably has at least one compound of at least one of the elements Sc, Y, Ti, Zr, V, Nb, Cr, Mo, W, Mn, Fe, Co, B, Al, Ga, In, TI, Si, Ge , Sn, Pb, Sb or Bi with at least one of the elements Te, Se, S, O, Sb, As, P, N, C, Si, Ge or Ga, such as TiO ₂ , Al ₂ O ₃ , SiO ₂ , ZrO ₂ , Y ₂ O ₃ , BC, SiC, Fe ₃ O ₄ , SiN, SiP, nitrides, sulfates, phosphites, silicides, spinels or yttrium aluminum garnet, or one of these elements itself. The inorganic component can also be aluminosilicates, aluminum phosphates, zeolites or partially exchanged zeolites such as ZSM-5, Na-ZSM-5 or Fe-ZSM-5 or amorphous microporous mixed oxides, which can contain up to 20% non-hydrolyzable organic compounds, such as e.g. vanadium oxide-silicon oxide glass or aluminum oxide-silicon oxide-methyl silicon sesquioxide- Glasses.

At least one inorganic component is preferably present in a grain size fraction with a grain size of 1 to 250 nm or with a grain size of 260 to 10,000 μm.

It can be advantageous if the composite materials used have at least two grain size fractions of at least one inorganic component. The grain size ratio of the grain size fractions in the composite material is from 1: 1 to 1: 10000, preferably from 1: 1 to 1: 100. The quantitative ratio of the grain size fractions in the composite material can preferably be from 0.01 to 1 to 1 to 0.01.

The permeability of the composite materials can be limited by the grain size of the inorganic component used to particles with a certain maximum size.

The suspension having at least one inorganic component, with which the composite materials can be obtained, can have at least one liquid selected from water, alcohol and acid or a combination of these liquids.

The permeable composite material which can be used according to the invention as the carrier material can have an applied layer of compounds from the group of the zeolites, the amorphous mixed metal oxides, the silicalites, aluminum silicates, aluminum phosphates, the partially exchanged zeolites or a mixture of compounds from this group. A material which is obtained by applying a suspension of zeolite particles in a sol or a sol comprising zeolite particles to a porous support and then solidifying can very particularly preferably be used as the permeable support material. Such zeolite-containing carrier materials, which can also be obtained in another way, preferably have the same zeolite compound that is to be synthesized in the carrier material by the process according to the invention. In this way, a larger release-active surface can be obtained, since the release-active layer is not only present between the pores of the support material but also the support material itself is partially active.

The composite material has an average pore size of less than 2000 nm, preferably less than 500 nm and very particularly preferably less than 10 nm. The mean pore size is defined in the sense of the invention as the arithmetic mean of the pore size distribution determined by mercury porosimetry. The maximum pore size is defined in the sense of the invention in such a way that the composite material is permeable only for particles of a size that is smaller than the maximum pore size.

The composite material can have at least one catalytically active component. The catalytically active component can be identical to the inorganic component. This applies in particular if the inorganic component has catalytically active centers on the surface.

As a catalytically active component, the composite material preferably has at least one inorganic material, at least one metal or at least one organometallic compound, on the surface of which there are catalytically active centers. The composite material can also be a zeolite, e.g. ZSM-5, Fe-ZSM-5, silicalite or an amorphous microporous mixed oxide, e.g. be described in DE 195 45 042 and / or DE 195 06 843, e.g. Vanadium oxide-silicon oxide glass or aluminum oxide-silicon oxide-methyl silicon sesquioxide glasses.

As a catalytically active component, however, the composite material can also have at least one oxide of at least one of the elements Mo, Sn, Zn, V, Mn, Fe, Co, Ni, As, Sb, Pb, Bi, Ru, Re, Cr, W, Nb, Ti, Zr, Hf, La, Ce, Gd, Ga, In, TI, Ag, Cu, Li, K, Na, Be, Mg, Ca, Sr, Ba, B, AI and Si.

It can also be advantageous if the composite material used as the carrier material as the catalytically active component has at least one metal compound selected from the compounds of the metals Bi, Pt, Rh, Ru, Ir, Au, Ag, Ti, Zr, Hf, V, Nb, Cr, Mo, W, Os, Re,

Cu, Fe, Ni, Pd and Co, or at least one metal selected from the metals Pt, Rh, Ru, Ir, Au, Ag, Os, Re, Fe, Cu, Ni, Pd and Co.

The composite material used as the carrier material in the membrane according to the invention is preferably designed to be bendable or flexible without destroying the composite material. The composite material can preferably be bent to a minimum radius of up to 2 cm.

It can be advantageous if the permeable carrier material has a homogeneous porosity. It can also be advantageous if the permeable carrier material has an inhomogeneous porosity. The permeable carrier material particularly preferably has regions with larger and regions with smaller porosity. The carrier material is very particularly preferably built up in layers from regions with larger and regions with smaller porosity. The porosity in the transition from one layer to the next layer preferably increases or decreases, so that a porosity gradient is present in the carrier material. A substance which has a homogeneous porosity in the sense of the present invention is understood to mean a substance which has pores of the same or almost the same size at the locations where it has pores. A carrier material according to the invention, which consists of a wire mesh with applied ceramic, is understood to be a carrier material with homogeneous porosity if the ceramic has pores with an essentially the same pore size. A carrier material according to the invention, which consists of a wire mesh with an applied ceramic, another ceramic with a different composition being applied to the ceramic on one side, has an inhomogeneous porosity in the sense of the present invention if the two ceramics have different pore sizes.

The pores of the separation-active layer in the membrane according to the invention preferably have a maximum pore size of less than 10 nm, particularly preferably less than 1 nm. The separating-active layer preferably has a thickness in the forward direction that corresponds to the maximum thickness of the carrier. The separating-active layer particularly preferably has a thickness in the forward direction which corresponds to 1/10 to 1 / 100,000, very particularly preferably 1/100 to 1 / 10,000, of the thickness of the carrier. Usual layer thicknesses for the release-active layer are in the range from 1 to 10 μm. However, it is also possible to use thinner or thicker separating agents Produce layers, wherein the layer thickness can be predetermined by the thickness of the layer of the support in which the separation-active layer is to be synthesized.

It can be advantageous if the separation-active layer is crystalline. The separation-active layer preferably has at least one compound which has molecular sieving properties. The separating-active layer particularly preferably has at least one crystalline compound composed of a natural or synthetic zeolite, an aluminosilicate, an aluminophosphate and / or a metal aluminophosphate. The membrane according to the invention very particularly preferably has a separation-active layer which contains at least one compound from the zeolites NaA, CaA, erionite, ZSM-5, ZSM-11, ZSM-20, ZSM-22, ZSM-23, ZSM-35, ZSM -38, ZSM-48, ZSM-12, Beta, L, ZSM-4, Omega, Offretit, X, Y, NaX, NaY, CaY, REY, US-Y, Mordenite, ZK-5, ZK-4, silicalite -1, the aluminosilicates, the aluminophosphates, the metal aluminophosphates, the metal aluminophosphosilicates or mixtures of these compounds.

It is apparent to the person skilled in the art that by replacing part of the aluminum but also the silicon from the abovementioned compounds with other elements, it is possible to obtain further active compounds which have different separation properties. These compounds often have the same structure as the original separation-active compounds, but have different lattice constants and therefore different pore sizes. For silicon and / or aluminum, the elements Be, Co, Cu, Fe, Zn, B, Cr, Ga, Ge, Sn, Ti, V, Zr, P and / or V can also be present in the compounds mentioned.

In a membrane according to the invention, the separation-active layer is preferably arranged in the outermost layer in the interior of the carrier material. The separation-active layer is particularly preferably arranged in the outermost layers of all sides of a carrier material in the interior. If nano-, micro- or ultrafiltration membranes are used as carrier material for the membranes according to the invention, the separation-active layer is preferably in the layer of these membranes which is the basis for the nano-, micro- or ultrafiltration capacity and which usually represents the outermost layer of a membrane.

The membrane according to the invention can be flexible depending on the carrier material used. In particular, the membrane according to the invention can be bendable to a smallest radius of 5 cm without loss of the separation properties.

The production of a membrane according to the invention is described below by way of example, without the method according to the invention being restricted to this embodiment.

The method according to the invention is characterized in that a release-active layer is synthesized in a permeable carrier material. The carrier materials described above, composite materials or materials usually used as ceramic membranes can be used as carrier material. Flexible permeable materials are preferably used as carrier materials. Support materials which can be bent to a minimum radius of 2 cm are very particularly preferably used. The permeable carrier material also preferably has an average pore size of less than 2000 nm, preferably less than 500 nm and very particularly preferably less than 100 nm.

According to the invention, a separation-active layer of crystals of at least one compound is selected from the zeolites NaA, CaA, erionite, ZSM-5, ZSM-11, ZSM-20, ZSM-22, ZSM-23, ZSM-35, ZSM- in the carrier material. 38, ZSM-48, ZSM-12, Beta, L, ZSM-4, Omega, Offretit, X, Y, NaX, NaY, CaY, REY, US-Y, Mordenite, ZK-5, ZK-4, Silikalit- 1, the aluminosilicates, the aluminophosphates, the metal aluminophosphates, the metal aluminophosphosilicates or mixtures of these compounds. Not only the compounds mentioned, but also compounds which are replaced by the exchange of, in particular, Al and / or Si in these compounds by the elements Be, Co, Cu, Fe, Zn, B, Cr, Ga, Ge, Sn, Ti, V , Zr, P and / or V can be obtained as a separation-active layer in the carrier material. These compounds often have the same structure as the original separation-active compounds, but have different lattice constants and therefore different pore sizes.

According to the invention, the membrane is produced by the separation-active layer or a precursor of the separation-active layer by feeding (infiltrating) one Crystallization solution, which has the components for the synthesis of the separation-active layer, is prepared in the carrier material and subsequent crystallization. The separating-active layer or a precursor of the separating-active layer is very particularly preferably produced by feeding (infiltrating) a crystallization solution, which has the components for the synthesis of the separating-active layer, into the outer layer of the carrier material and subsequent crystallization. The crystallization solution is preferably fed in such a way that the crystallization solution replaces the gas, usually air, present in the pores of the carrier material when it penetrates. This measure ensures that all the pores in a layer of the carrier material are filled by the separation-active layer after crystallization. The membranes usually produced without this measure often have air pockets during the manufacturing process of the separation-active layer, which during the subsequent use of the membrane represent imperfections, that is, pores with too large a diameter, so that the selectivity of such membranes is impaired. With these processes, the gas present in the pores does not have sufficient opportunity to emerge from the pores.

The crystallization solution is preferably fed in by spraying or dropping the crystallization solution onto the support material. The result of this is that the entire surface of the carrier material is not simultaneously wetted with the crystallization solution and the gas present in the pores can thus escape. The penetration of the crystallization solution into the carrier material is preferably carried out by simple capillary forces, which suck the solution into the pores. It can be advantageous if a negative pressure is generated on the opposite side of the carrier material, so that the crystallization solution is sucked into the carrier material at an accelerated rate.

In the method according to the invention, it can be advantageous to control the depth of penetration of the crystallization solution into the carrier material. For example, the penetration depth of the crystallization solution into the carrier material can be influenced by adjusting the viscosity of the crystallization solution.

The penetration depth of the crystallization solution can, however, also be influenced in particular by using a particularly suitable carrier material. So it can be beneficial be, if the carrier material has a layer, for example an ultrafiltration layer, which is not permeable to all components present in the crystallization solution. On this ultrafiltration layer, the carrier material has, as the outermost layer, a further layer which is permeable to all components of the crystallization solution, such as a microfiltration layer. When using such a carrier material, the crystallization solution with all components will only penetrate into the outer layer. Subsequent, for example, hydrothermal treatment with or without subsequent calcination, a membrane is obtained which has the separation-active layer only in the outer layer of the carrier material.

It is also possible to use layers with different chemical properties, e.g. have hydrophilized or hydrophobized layers. The production of carrier materials which have hydrophobized layers is e.g. described in WO 99/62624. Such layers can e.g. by adding organosilicon compounds, e.g. Silanes, to be made to sol during the manufacture of the layer.

Depending on the properties of the crystallization solution, the depth of penetration of the crystallization solution can be controlled by using such layers. Is it e.g. an aqueous crystallization solution, e.g. a carrier material can be used which has an outer layer which has hydrophilic properties and a layer under this outer layer which has hydrophobic properties. When the aqueous crystallization solution is supplied, it will predominantly only fill the pores of the hydrophilic layer. In the subsequent crystallization and calcination, the separation-active layer will only arise in the outermost layer. The maximum thickness of the separation-active layer can be set by specifying the thickness of the hydrophilic layer.

Correspondingly, membranes can be constructed that have a certain permeability or separation property on certain sides.

The carrier material pretreated in this way, with the crystallization solution present therein, is preferably added to an autoclave for crystallization, in which the carrier material coexists further crystallization solution is brought into contact. Preferably, only the side of the support material is brought into contact with the crystallization solution, which was previously supplied with the crystallization solution by spraying or dropping. If crystallization solution has been supplied to a support material from all sides, it may be advantageous to immerse the support material in the crystallization solution. Usually the same crystallization solution is used, which has already been added to the carrier material by spraying or dropping. However, it can also be advantageous to use a crystallization solution different from the supplied crystallization solution in the autoclave. By using a crystallization solution with a lower concentration than that of the crystallization solution used in the supply or spraying, a lower tendency to crystallize on the support surface can be achieved in the autoclave. Another advantage is a cost reduction through the use of the diluted crystallization solution. The use of pure water is not advantageous since the synthesis of the release-active layer in the support material does not succeed so completely in the pores of the support material when using pure water in the autoclave that an error-free release-active layer is obtained.

Crystallization can be carried out in a manner known to those skilled in the art, e.g. hydrothermally at a temperature of 70 to 400 ° C and a pressure of 0.3 to 200 bar. The crystallization is particularly preferably carried out hydrothermally at a temperature of 100 to 250 ° C. and a pressure of 0.5 to 40 bar. It can be advantageous to support the crystallization by means of a temperature program. The heating to the treatment temperature is preferably carried out at a heating rate of 1 to 100 IC / h, preferably 5 to 25 K / h. For the crystallization, the carrier material to which the crystallization solution was fed is left for 12 to 72 hours, very particularly preferably 18 to 36 hours, at the treatment temperature of preferably 170 to 250 ° C. However, all other methods for crystallizing the above-mentioned compounds to be used as a separation-active layer are also possible.

It may be advantageous to calcine the membrane obtained after treating the support material with the crystallization solution. The calcination takes place preferably in the presence of oxygen, for example atmospheric oxygen at a temperature of greater than 300 ° C., preferably greater than 500 ° C., for a period of 12 to 120 hours, preferably for a period of 24 to 36 hours. The calcining is particularly preferably carried out at a temperature range of 340 to 450 ° C. for a time of 60 to 120 hours. In order to avoid thermal stresses during calcining, it may also be advantageous to bring the membrane to be calcined to the calcining temperature at a heating rate of 0.1 to 1 K / min, preferably 0.2 to 0.5 K / min. It may also be advantageous to cool the calcined membrane from the calcining temperature to room temperature at a cooling rate of 0.1 to 1 K / min, preferably from 0.2 to 0.5 K / min. By calcining, any organic compounds present in the crystallization solutions and thus in the support material, such as crystallization aids such as tetrapropylammonium compounds (TPA compounds) such as TPAOH or TPABr, are reacted or burned and expelled from the membrane. Furthermore, the crystal structure in the separation-active layer is stabilized by the calcining.

However, it must be noted that when using carrier materials that have carbon or natural fibers, they are also completely or partially removed from the carrier material by burning or decomposing by calcining. If these fibers are to be retained in the carrier material, it is advantageous to use crystallization solutions in which calcination of the membrane is not necessary because, e.g. have no crystallization aids.

The crystallization solution preferably has at least one silicon compound, an aluminum compound or a phosphorus compound or a mixture of one or more of these compounds. The crystallization solution particularly preferably has at least one silicate, an aluminate or phosphate or a mixture of one or more of these compounds. The crystallization solution preferably has a silicon to aluminum ratio of 1 to infinity.

The crystallization solutions can have one or more crystallization aids. Suitable crystallization aids are, for example, tetraalkylammonium compounds, such as Tetrapropylammonium hydroxide or bromide (TPAOH or TPABr), (Me ₄ N) ₂ O, Et ₄ NOH, (Pr N) ₂ O, or crown ether (18-crown-6, 15-crown-5), tetraethylorthosilicate or cetyltrimethylammonium compounds like (CTMA) ₂ O. These products can be used as crystallization aids, but are usually removed after the synthesis by burning in air at 500-600 ° C.

The crystallization solution according to the invention usually has water. In the preparation of the crystallization solutions, the molar proportion of water can be varied, taking care that the crystallization solution remains liquid, i.e. that gel formation should be avoided and that a minimum concentration in the crystallization solution is not fallen below, since otherwise no crystallization takes place would. In certain cases it may be necessary or advantageous to exchange the water for other compounds. The synthesis of silica sodalite is carried out in the presence of ethylene glycol instead of in water.

The following table shows typical compositions of crystallization solutions and the type or structure of the active separation compound which can be synthesized from this crystallization solution. The compositions given are only an exemplary selection, since the compounds mentioned can also be obtained despite a deviation from the compositions specified. Depending on the type of zeolite desired, the composition of the crystallization solution can be more or less variable. Thus, the zeolite of the ZSM-5 type can also be obtained if there are deviations in the composition of the crystallization solution of a component, in particular of silicon dioxide, of 100% or more. In contrast, the NaA zeolite type is only obtained if the deviations from the ideal composition of the crystallization solution are small. Two different possible compositions are given for the Zeolite-A and the ZSM-5 types.

It is apparent to the person skilled in the art that by replacing part of the elements used, in particular the replacement of the aluminum but also the silicon by other elements separation-active compounds can be obtained which have other separation properties. These compounds often have the same structure as the original separation-active compounds, but have different lattice constants and therefore different pore sizes. In addition, the replacement of aluminum or silicon with other elements, such as transition metal elements, can produce catalytic properties. A detailed treatise on zeolites, their synthesis and their modification can be found, for example, in J. Weitkamp and L. Puppe, "catalysis and zeolites: fundamentale and applications", Springer-Verlag, Berlin, 1999. This treatise also includes other possible compositions for crystallization solutions , as well as synthesis parameters, tailored to certain compositions.

Table 1 Crystallization compositions

Basically, all relevant known compositions used for the production of zeolites are suitable. For example, a composition of 2 parts of SiO ₂ leads to 2 parts of Na ₂ O to one part of Al ₂ O ₃ and to 120 parts of water leads to an A-type zeolite and a composition of 10 parts of SiO ₂ to 14 parts of Na ₂ O. to one part Al ₂ O ₃ to 840 parts water to a zeolite of the X type. Of course, many types of zeolites, for example of the ZSM-5 type, A type, X type, Y type, etc., are suitable for achieving the desired pore size. The pore sizes of the separating layer which can be achieved according to the invention can, depending on the compound selected for the separating layer, from 0.26 nm x 0.57 nm (mordenite) to 0.53 nm x 0.56 nm (ZSM-5) and 0, 76 nm x 0.64 nm (zeolite beta) up to 1.6 nm to 10.0 nm (mesoporous aluminosilicates).

The pore size and properties of the compounds can also be influenced by varying the composition, in particular the silicon to aluminum ratio. A high Si / Al ratio, often also referred to as a modulus, often leads to the zeolite having hydrophobic properties.

The selection of the most suitable type of zeolite or the most suitable separating compound, e.g. Microporous silicate, microporous phosphate or microporous amorphous or crystalline mixed metal oxide depends on the desired pore size and the separation problem itself.

The membrane according to the invention can be used as a separation membrane in processes for separating mixtures of compounds or molecules. In particular, the membrane according to the invention can be used as a separation membrane in processes for separating mixtures of compounds or molecules with the same molecular weight and different structure, such as, for example, in processes for separating n-butane and isobutane. The membrane can also be used as a separating membrane in processes for separating particles, particles, compounds or molecules which have an average size of less than 10 nm. The membrane according to the invention is also suitable for use as a separation membrane in processes for separating mixtures of molecules or compounds of the same molecular weight but different adsorption behavior on zeolite pore walls. at In this method, the different adsorption behavior of the compounds or molecules to be separated in the separation-active layer, which in this case preferably has at least one zeolitic compound, is used for the separation.

The membranes according to the invention are very particularly suitable for use as a separation membrane when carrying out pervaporation or vapor permeation processes. These methods are e.g. used in the separation of alcohol-water mixtures, in particular ethanol-water mixtures. During pervaporation, a liquid mixture is fed to the membrane and the permeate leaves the membrane on the other side as a vapor phase. In the case of vapor permeation, the mixture to be separated is already supplied to the membrane in vapor form. The separation of ethanol-water mixtures by means of pervaporation is usually carried out at a temperature of 70 to 90 ° C., while the separation is carried out by means of vapor permeation at a temperature of more than 100 ° C. A membrane according to the invention is particularly suitable as a separating membrane for these processes, since it has a higher temperature resistance than membranes based on organic polymers.

The method according to the invention for producing the membrane according to the invention and the membrane according to the invention are described in more detail with reference to FIGS. 1 to 5, without the invention being restricted to the embodiments.

1 shows a scanning electron micrograph of the carrier material treated in Example 1. Zeolite crystals can be seen on the surface of the carrier material, but the separation-active layer is located in the pores.

2 shows a scanning electron micrograph of the carrier material used in the untreated state.

3 shows a scanning electron micrograph of the fracture surfaces of the untreated carrier material. It can be clearly seen that pores are present in the carrier material. FIG. 4 shows a scanning electron micrograph of a fracture surface of the carrier material treated in example 1. The pores which can be seen in FIG. 3 cannot be seen on this photograph, since the pores are filled with zeolite crystals.

5 shows an X-ray diffraction diagram of the Al ₂ O ₃ support (a), the Al ₂ O ₃ / MFI membrane from Example 1 (b) and the reference data for MFI (c). A comparison of the diffraction patterns shown in diagrams b and c confirms that the membrane according to Example 1 has zeolites of the MFI type.

Example 1: Preparation of an MFI-type zeolite membrane

A crystallization solution for the synthesis of an MFI-type zeolite was prepared. For this purpose, 3.2 g of NaOH biscuits and 64 g of tetrapropylammonium bromide (TPABr) were dissolved in 172 g of distilled water. This solution was mixed with 320 g of colloidal silica sol (Carl Roth GmbH Co, Karlsruhe) and homogenized by stirring. The crystallization solution thus obtained had the molar composition SiO ₂ 100: 15 (TPA) ₂ O: 5 Na ₂ O: 1420 H ₂ O. This crystallization solution was slowly added dropwise to a serving as the support material flexible ceramic membrane. A composite material produced according to WO 99/15262 was obtained as a flexible, ceramic membrane, which was obtained by a sol consisting of 120 g titanium triisopropylate, 60 g water, 100 g hydrochloric acid (25%) and 280 g aluminum oxide (SC530SG, Fa. Alcoa, Germany) was applied to a support made of a square mesh fabric made of stainless steel (Paul GmbH, Germany) with a mesh size of 150 μm and solidified at 350 ° C. for 10 minutes. This planar, flexible, symmetrical α-Al ₂ O ₃ membrane with a diameter of 60 mm was infiltrated by dripping the crystallization solution onto it.

The infiltrated carrier material was fixed in the autoclave with a holder. Sufficient crystallization solution was then filled into the autoclave so that the carrier material was completely covered by the crystallization solution. The hydrothermal zeolite synthesis took place at a temperature of 175 ° C over a period of 17 hours. Following the synthesis, the membrane was removed from the autoclave with distilled water washed and dried at 120 ° C for 24 hours. The dried membrane was then calcined at a temperature of 540 ° C for 16 hours. The heating rate was 1 Kmin ¹ from room temperature to 250 ° C., 0.2 Kmin ^"1 from 250 ° C to 540 ° C. The cooling rate was 0.2 Kmin ^{" 1} , from 250 ° C to 540 ° C to 250 ° C to room temperature 1 Kmin ^"1 .

The membrane was examined by scanning electron microscopy. The surface was partly covered with zeolite crystals that were closely intergrown with one another (FIG. 2). The view of the fracture surfaces showed the complete crystallization of the separation-active layer made of zeolite within the pore structure of the carrier material (FIG. 4). Using X-ray diffractometry, it was demonstrated that the crystallization product was exclusively the zeolite of the MFI structure (FIG. 5).

Example 2: Preparation of an A-type zeolite membrane

A 22% sodium aluminate solution in water is mixed with a 34% solution of sodium silicate in water in a 1: 1 ratio to a crystallization solution. This crystallization solution was slowly dripped onto a flexible ceramic membrane serving as a carrier material. A composite material produced according to WO 99/15262 was obtained as a flexible, ceramic membrane, which was obtained by a sol consisting of 120 g titanium triisopropylate, 60 g water, 100 g hydrochloric acid (25%) and 280 g aluminum oxide (SC530SG, Fa. Alcoa, Germany) was applied to a support made of a square mesh fabric made of stainless steel (Paul GmbH, Germany) with a mesh size of 150 μm and solidified at 350 ° C. for 10 minutes. This planar, flexible, symmetrical α-Al ₂ O ₃ membrane with a diameter of 60 mm was infiltrated by dripping the crystallization solution onto it.

The infiltrated carrier material was fixed in the autoclave with a holder. Sufficient crystallization solution was then filled into the autoclave so that the carrier material was completely covered by the crystallization solution. The hydrothermal zeolite synthesis took place at a temperature of 170 ° C over a period of 17 hours. Following the Synthesis, the membrane was removed from the autoclave, washed with distilled water and dried at 120 ° C for 2 hours. A membrane was obtained which has a layer of the compound zeolite A as the separation-active layer.

Claims

claims:

1. membrane, which has a permeable carrier material and a separating layer, characterized in that the membrane at least one separating layer in the permeable

Has carrier material.

2. Membrane with at least one separation-active layer in a material-permeable carrier material which, by introducing a crystallization solution which has the components necessary for the synthesis of the separation-active layer, into a carrier material, the gases present in the pores of the carrier material being displaced by the crystallization solution from the carrier material be, and subsequent crystallization of the separation-active layer in the carrier material is available.

3. Membrane according to claim 1 or 2, characterized in that the pores of the separation-active layer have a maximum pore size of less than 10 nm.

4. Membrane according to claim 3, characterized in that the pores have a maximum pore size of less than 7 nm.

5. Membrane according to at least one of claims 1 to 4, characterized in that the permeable carrier material comprises metal, glass, ceramic or a combination of these materials.

6. Membrane according to at least one of claims 1 to 5, characterized in that the permeable carrier material is fabric, nonwovens, sintered powder or sintered fibers made of metal, glass, ceramic or a combination of these materials.

7. Membrane according to at least one of claims 1 to 6, characterized in that the permeable carrier material is a material which as

Microfiltration membrane, ultrafiltration membrane, nanofiltration membrane or gas separation membrane can be used.

8. Membrane according to at least one of claims 1 to 7, characterized in that the permeable carrier material has a homogeneous porosity.

9. Membrane according to at least one of claims 1 to 7, characterized in that the permeable carrier material has an inhomogeneous porosity.

10. Membrane according to claim 9, characterized in that the permeable carrier material has areas with larger and areas with smaller porosity.

11. Membrane according to claim 10, characterized in that the areas with larger and areas with smaller porosity are constructed in layers.

12. Membrane according to claim 11, characterized in that the porosity increases or decreases during the transition from one layer to the next.

13. Membrane according to at least one of claims 1 to 12, characterized in that the separation-active layer has a thickness in the forward direction, less than or equal to the thickness of the carrier material.

14. Membrane according to claim 13, characterized in that the separating layer in the forward direction has a thickness of 1/10 to 1 / 100,000 of the thickness of the carrier material.

15. Membrane according to at least one of claims 1 to 14, characterized in that the separation-active layer has at least one compound which has molecular sieve properties.

16. Membrane according to at least one of claims 1 to 15, characterized in that the separation-active layer at least one compound of a natural and / or synthetic zeolite, an aluminosilicate, an aluminophosphate and / or one

Has metal aluminophosphate.

17. Membrane according to claim 16, characterized in that the separation-active layer is selected from at least one crystalline compound

Zeolites NaA, CaA, erionite, ZSM-5, ZSM-11, ZSM-20, ZSM-22, ZSM-23, ZSM-35, ZSM-38, ZSM-48, ZSM-12, Beta, L, ZSM-4 , Omega, X, Y, NaX, NaY, CaY, REY, US

Y, mordenite, ZK-5, ZK-4, the aluminosilicates, the aluminophosphates, the

Metal aluminophosphates, the metal aluminophosphosilicates or mixtures thereof

Connections.

18. Membrane according to at least one of claims 1 to 17, characterized in that the release-active layer is arranged in the outermost layer in the interior of the carrier material.

19. Membrane according to at least one of claims 1 to 17, characterized in that the separating layer is arranged in the outermost layer of all sides of a carrier material inside.

20. Membrane according to at least one of claims 1 to 19, characterized in that the membrane is flexible.

21. Membrane according to at least one of claims 1 to 20, characterized in that the membrane can be bent to a minimum radius of 5 cm without loss of the separating properties.

22. A method for producing a membrane according to at least one of claims 1 to 21, characterized in that a release-active layer is synthesized in a permeable carrier material.

23. The method according to claim 22, characterized in that in the carrier material a separation-active layer of at least one crystalline compound selected from the zeolites NaA, CaA, erionite, ZSM-5, ZSM-11, ZSM-20,

ZSM-22, ZSM-23, ZSM-35, ZSM-38, ZSM-48, ZSM-12, Beta, L, ZSM-4, Omega, X, Y, NaX, NaY, CaY, REY, US-Y, Mordenite, ZK-5, ZK-4, the aluminosilicates, the aluminophosphates, the metal aluminophosphates, the metal aluminophosphosilicates or mixtures of these compounds is synthesized.

24. The method according to any one of claims 22 or 23, characterized in that the separation-active layer or a precursor of the separation-active layer is produced by feeding a crystallization solution, which has the components for the synthesis of the separation-active layer, into the carrier material and subsequent crystallization.

25. The method according to claim 24, characterized in that the release-active layer or a precursor of the release-active layer by supplying a crystallization solution, which has the components for the synthesis of the release-active layer, into the outer layer of the carrier material and subsequent

Crystallization is made.

26. The method according to any one of claims 24 or 25, characterized in that the crystallization hydrothermally at a temperature of 70 to 400 ° C and one

Pressure from 0.3 to 200 bar is carried out.

27. The method according to claim 26, characterized in that the crystallization hydrothermally at a temperature of 100 to 250 ° C and a

Pressure of 0.5 to 40 bar is carried out.

28. The method according to at least one of claims 22 to 27, characterized in that the permeable carrier material is flexible.

29. The method according to claim 28, characterized in that the permeable carrier material is bendable to a minimum radius of 2 cm.

30. The method according to at least one of claims 22 to 29, characterized in that the permeable carrier material has an average pore size of Ideine 2000 nm.

31. The method according to at least one of claims 24 to 30, characterized in that the crystallization solution has at least one silicate.

32. The method according to at least one of claims 24 to 30, characterized in that the crystallization solution has at least one aluminate.

33. The method according to at least one of claims 24 to 30, characterized in that the crystallization solution has at least one silicate and at least one aluminate.

34. Use of a membrane according to at least one of claims 1 to 21 for the separation of compounds or molecules from mixtures of substances.

35. Use of a membrane according to at least one of claims 1 to 21 for the separation of compounds or molecules, which have an average size of less than 10 nm, from mixtures of substances.

36. Use of a membrane according to at least one of claims 1 to 21 for the separation of mixtures of compounds or molecules, the same

Molecular weight have a different adsorption behavior on zeolite pore walls.

37. Use of a membrane according to at least one of claims 1 to 21 for the separation of mixtures of compounds or molecules, the same

Molecular weight have a different geometry or structure.

8. Use of a membrane according to at least one of claims 1 to 21 as a membrane in pervaporation or vapor permeation.