DE10055611A1 - Membrane for use in pervaporation or vapor permeation, comprises material-permeable support material and separation-active layer - Google Patents

Abstract

A membrane comprises a material-permeable support material and a separation-active layer. An Independent claim is also included for the production of a membrane comprising synthesizing a separation-active layer in a material-permeable support material. Preferred Features: The pores of the separation-active layer have a pore size of less than 10, preferably less than 7 nm. The material-permeable support material is made from metal, glass, ceramic or a combination of these materials, preferably fabric, fleece, sintered powder or sintered fibers made from metal, glass, ceramic or a combination of these materials. The support material is a material used as a microfiltration, ultrafiltration, nanofiltration or gas separation membrane.

Description

Zeolite membranes, a process for their production and the Use of the zeolite membrane.

A common problem in industrial processes is material separation, in particular the separation of mixtures of liquids or gases. Classical Separation processes such as B. distillation, extraction or adsorption are relatively expensive. Separation processes using membranes are used in particular for gas separation used. Organic membranes are currently frequently used, although these are only limited can be used because their chemical, mechanical and thermal stability is limited.

Ceramic materials that can be used as membranes have recently been developed that have adequate stability in terms of chemical, mechanical or thermal Have 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 manufacturing process can be aluminosilicates or zeolites produce that have a certain pore size. Because zeolites have a defined Have pore size, they are suitable for the separation of compounds or molecules, which is why such compounds are often called molecular sieves. By combination Zeolites with inorganic membranes can be used to produce zeolite membranes Separation of certain gas mixtures are suitable.

There are already numerous attempts to manufacture and use combinations Membranes and zeolites have been described. Such is usually produced Combined membranes by a method in which an inorganic membrane by hydrothermal synthesis in a crystallization solution after heterogeneous nucleation Zeolite layer is crystallized on the membrane.  

For the separation of mixtures of n-butane and isobutane, separation criteria 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. Sci. 144 (1998) 65-76). Giroir-Fendler et al., Stud. Surf achieved similarly good results. Sci. Catal. 111 (1996) 127 and Kusakabe et al. J. Membr. Sci. 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, this membrane achieves separation factors greater than 10,000 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 prevailed because Despite acceptable separation performance, the manufacture of such membranes is time and cost intensive is. This is due in particular to the fact that the number of membrane defects due to synthesis only can be minimized by the fact that the manufacturing process, ie the crystallization is repeated several times. This also leads to an increase in membrane thickness a decrease in flow rates in material separation and thus the use of this Membrane ineffective in separation processes.

In recent times, attempts have been made to place zeolite membranes within a ceramic layer synthesize. Hoffmann et al. at the 12th German Zeolite Conference in 2000 a poster that tested a new process that should work, one To synthesize zeolite membrane in the pores of a porous support. With this procedure a zeolite synthesis solution is infiltrated into the carrier and only then does one take place hydrothermal treatment of the sample. No further information was given about the Manufacturing parameters made. It was also not possible to prove that the membranes thus produced are suitable for the separation of liquids or gases.  

Moueddeb et al. (submitted to J. Membr. Sci.) as well as the PCT application WO 95/29751 the production of a zeolite membrane in the pores of a cylindrical support based on aluminum oxide. The review shows that it is possible to have an almost defect-free one To manufacture zeolite membrane in the pores of a cylindrical support based on aluminum oxide.

The methods described for the production of zeolite membranes have the disadvantage that they lead to zeolite membranes that are mechanically very weak. In addition, the Production of such zeolite membrane is relatively complex and therefore expensive, which is why industrial use of such membranes, e.g. B. for gas separation, has not yet taken place.

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

Surprisingly, it was found that by introducing a crystallization solution into a permeable carrier material and subsequent crystallization of a separating layer in a ceramic membrane can be obtained from the carrier material, which improved Features mechanical and chemical stability than conventional Membranes, the properties of which include the crystallization solution used and thus z. B. depend on the types of zeolite produced.

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

The present invention also relates to a membrane with at least one separating active layer in a permeable carrier material according to claim 2, which by Introduction of a crystallization solution which is used for the synthesis of the separation-active layer has necessary components, in a carrier material, the in the pores of the Gases present 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 nm.

The membrane according to the invention has the advantage that, depending on the intended use are significantly more durable than the membranes available so far with similar ones Properties like those of the membrane according to the invention.

The membrane according to the invention also has the advantage that, as carrier materials, in which the layer of separation-active crystals is introduced, inexpensive materials can be used.

The membrane of the invention is also characterized by excellent Separation properties. Since the separation-active layer is very thin, the layer according to the invention has Membrane 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 on its Crystal grain boundaries is so dense that no unwanted material passages are possible.

Another advantage of the membrane according to the invention is that the membrane depends on The backing material used is flexible and bendable without the good separating properties get lost. It is also particularly advantageous that the membrane according to the invention the method according to the invention can also be produced very inexpensively in large areas can.  

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 should be limited to these designs.

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

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

In the context of the present invention, a membrane is understood to mean a material which is suitable for separating substances and thus for particles up to a certain size permeable and impermeable to larger particles.

For the purposes of the present invention, the separating layer is understood to mean the layer 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 just barely is permeable.

The permeable carrier material present in the membrane according to the invention can Metal, glass, ceramic or a combination of these materials. Preferably points the permeable carrier material is woven fabric, fleeces, sinter powder or sinter fibers made of metal, Glass, ceramics or a combination of these materials. Likewise, the permeable Carrier material have woven or non-woven fabrics made of carbon fabric. The permeable The carrier material can also be a material which itself acts as a microfiltration membrane,  Ultrafiltration membrane, nanofiltration membrane or gas separation membrane used can be. Such a combination of materials can also be used as the carrier material, at which a micro, nano and / or ultrafiltration membrane as a layer on and / or in one Carrier or applied in and / or on a micro, nano and / or ultrafiltration membrane has been.

The production of such materials or material combinations is, for. B. in the PCT Applications WO 96/00198, WO 99/15262 or WO 99/15272 are described. All these Materials are based on composite materials that are an inorganic or ceramic material applied to and in a porous support. The membrane according to the invention can Both the composite materials described below and the latter as the carrier material have underlying carrier.

The composite materials have at least one openwork and permeable carrier. On at least one side of the carrier and inside the Carrier, the carrier has at least one inorganic component that is essentially at least one compound made of a metal, a semimetal or a mixed metal has at least one element of the 3rd to 7th main group. Under the inside of a carrier are understood in the cavities or pores in a carrier.

The composite materials can be applied by applying a suspension, the at least one Connection of at least one metal, a semi-metal or a mixed metal with at least an element of the 3rd to 7th main group, inorganic component and a sol has, on an openwork and permeable support, and by at least one-time heating, in which the at least one inorganic component Suspension on or in or on and solidified in the carrier can be obtained.

The composite materials can also by vapor deposition, impregnation or Coprecipitation can be obtained.  

The composite materials can be permeable to gases, solids or liquids, especially for particles with a size of less than 10 nm. The spaces in the Composites can include pores, meshes, holes, crystal lattice spaces or Be 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 at least a combination of these materials, exhibit. The carriers, which can have the aforementioned materials, can be made by a chemical, thermal or mechanical treatment method or one Combination of treatment methods have been modified. Preferably, the Composites a carrier that is at least a metal, a natural fiber or a Has plastic which, according to at least one mechanical deformation technique or Treatment method, such as B. drawing, upsetting, milling, rolling, stretching or forging was modified. The composite materials very particularly preferably have at least one Carrier, the at least interwoven, glued, matted or ceramic-bound fibers, or has at least sintered or bonded shaped bodies, balls or particles. In a another preferred embodiment, a perforated carrier can be used. Permeable carriers can also be those that are produced by laser treatment or Ion beam treatment become permeable or have been made.

It can be advantageous if the carrier fibers are selected from at least one material Carbon, metals, alloys, ceramics, glass, minerals, plastics, amorphous Substances, composites and natural products or fibers from at least one combination these materials, such as B. asbestos, glass fibers, rock wool fibers, carbon fibers, metal wires, Steel wires, polyamide fibers, coconut fibers, coated fibers. Preferably be Carrier used, which have at least woven fibers made of metal or alloys. As Metal fibers can also serve as wires. The very particularly preferably have Composites on a carrier, such as at least a steel or stainless steel mesh z. B. from steel wires, steel fibers, stainless steel wires or stainless steel fibers by weaving manufactured fabric, which preferably has a mesh size of 5 to 500 microns, particularly preferred mesh sizes of 50 to 500 microns and very particularly preferred Mesh sizes of 70 to 120 microns have.  

The carrier of the composite materials can also have at least one expanded metal with a Have pore sizes of 5 to 500 microns. According to the invention, however, the carrier can also at least one granular, sintered metal, a sintered glass or a metal fleece with a Pore size from 0.1 microns to 500 microns, preferably from 3 to 60 microns.

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 one coated with Au, Ag, Pb, Ti, Ni, Cr, Pt, Pd, Rh, Ru and / or Ti Has material.

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, Al 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, Tl, 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. B. 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 themselves. The inorganic component can also be aluminosilicates, aluminum phosphates, zeolites or partially exchanged zeolites, such as, for. B. 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. B. vanadium oxide-silica glass or alumina-silica-methyl-silicon sesquioxide glasses.

At least one inorganic component is preferably present in a grain size fraction a grain size of 1 to 250 nm or with a grain size of 260 to 10000 nm.

It can be advantageous if the composite materials used have at least two Have 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 determined by the grain size of the inorganic component limited to particles of a certain maximum size become.

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

The permeable composite material which can be used according to the invention as a carrier material can an applied layer of compounds from the group of zeolites, the amorphous Mixed metal oxides, the silicalites, aluminosilicates, aluminum phosphates, the partial exchanged zeolites or a mixture of compounds of this group. All a material can particularly preferably be used as the permeable carrier material, which by applying a suspension of zeolite particles in a sol or a Sol containing zeolite particles on a porous support and subsequent solidification is obtained. Such zeolite-containing carrier materials, which also in other ways can be obtained, preferably have the same zeolite compound by the the inventive method is to be synthesized in the carrier material. In this way  a larger release-active surface can be obtained since the release-active layer not only is 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 of less than 500 nm and very particularly preferably less than 10 nm. The average pore size is defined in the sense of the invention as the arithmetic mean of the Mercury porosimetry determined pore size distribution. The maximum pore size is in The meaning of the invention is defined in such a way that the composite material is only for particles of one size which is permeable smaller than the maximum pore size.

The composite material can have at least one catalytically active component. The The catalytically active component can be identical to the inorganic component. this applies especially when the inorganic component is catalytically active on the surface Centers.

The composite material preferably has at least one as a catalytically active component inorganic material, at least one metal or at least one organometallic compound on whose surface there are catalytically active centers. The composite can as a catalytic component, a zeolite, such as. B. ZSM-5, Fe-ZSM-5, silicalite or a Amorphous microporous mixed oxide, such as z. B. in DE 195 45 042 and / or DE 195 06 843 are described, such as. B. 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 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, Tl, Ag, Cu, Li, K, Na, Be, Mg, Ca, Sr, Ba, B, Al and Si exhibit.

It can also be advantageous if the composite material used as the carrier material as a catalytically active component, 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 carried out without destroying the composite, bendable or flexible. 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 having. It can also be advantageous if the permeable carrier material is a has inhomogeneous porosity. The permeable carrier material particularly preferably has Areas with larger and areas with smaller porosity. Is very particularly preferred the carrier material in layers from areas with larger and areas with smaller Porosity built up. The porosity decreases during the transition from one layer to the next layer preferably up or down, so that a porosity gradient is present in the carrier material. Under a substance that has a homogeneous porosity in the sense of the present invention understood a substance which, at the places where it has pores, pores of the same or has almost the same size. A carrier material according to the invention, which consists of a Wire mesh with applied ceramic is then used as a carrier material with a more homogeneous Porosity understood when the ceramic has pores with a substantially same pore size having. A carrier material according to the invention, which consists of a wire mesh with a applied ceramics, one ceramic on the other side with another ceramic Composition has been applied, has an inhomogeneous porosity in the sense of present invention if the two ceramics have different pore sizes exhibit.

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 the corresponds to the maximum thickness of the carrier. The separating layer particularly preferably has The direction of transmission has a thickness that is 1/10 to 1 / 100,000, very particularly preferably 1/100 to  1 / 10,000 corresponds to the thickness of the carrier. Usual layer thicknesses for the release-active layer are in the range of 1 to 10 µm. However, it is also possible to use thinner or thicker separating agents Produce layers, the layer thickness being determined by the thickness of the layer of the carrier, in which the separation-active layer is to be synthesized can be specified.

It can be advantageous if the separation-active layer is crystalline. Preferably, the separating active layer at least one compound that has molecular sieve properties. The separation-active layer particularly preferably has at least one crystalline compound a natural or synthetic zeolite, an aluminosilicate, an aluminophosphate and / or a metal aluminophosphate. Most preferably, the membrane according to the invention has a separating layer which comprises at least one compound 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, Silikalit-1, the aluminosilicates, the aluminophosphates, the Metallalumophosphaten, the Metallalumino-phosphosilikaten or mixtures of these Connections includes.

The person skilled in the art can see that by replacing part of the aluminum but also the Silicon from the aforementioned compounds by other elements further separation-active Compounds can be obtained which have other separation properties. This Compounds often have the same structure as the original disconnect-active ones Compounds, however, have different lattice constants and therefore different pore sizes. For Silicon and / or aluminum can also contain the elements Be, Co, Cu, Fe, Zn, B, Cr, Ga, Ge, Sn, Ti, V, Zr, P and / or V may be present.

In a membrane according to the invention, the separation-active layer is preferably in the outermost layer arranged in the interior of the carrier material. The is particularly preferred separating layer in the outermost layers of all sides of a carrier material inside arranged. Are nano-, micro- or ultrafiltration membranes, the separating layer is located  preferably in the layer establishing the nano, micro or ultrafiltration capacity of these membranes, which is usually 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 have no loss of separation properties be bendable to a minimum radius of 5 cm.

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 in a permeable material Carrier material is a separating active layer is synthesized. As a carrier material, the Carrier materials, composites described above or usually as ceramic membranes used materials are used. Preferably be flexible permeable materials used as carrier materials. Most notably backing materials which are flexible down to a minimum radius of 2 cm are preferred used. The permeable carrier material also preferably has a medium one Pore size of less than 2000 nm, preferably less than 500 nm and very particularly preferred less than 100 nm.

According to the invention, a separation-active layer of crystals is formed in the carrier material at least one 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, Offretit, X, Y, NaX, NaY, CaY, REY, US-Y, Mordenite, ZK-5, ZK-4, Silikalit-1, den Aluminosilicates, the aluminophosphates, the metal aluminophosphates, the Metal aluminophosphosilicate or mixtures of these compounds synthesized. It can not only the connections mentioned but also connections created by exchange in particular of 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 separating layer be synthesized in the carrier material. These connections often have the same structure  like the original active disconnects, but have different lattice constants and therefore other pore sizes.

According to the invention, the membrane is produced by the separation-active layer or a precursor of the separation-active layer by supplying (infiltrating) one Crystallization solution which has the components for the synthesis of the separation-active layer, is produced in the carrier material and subsequent crystallization. Most notably the separation-active layer or a precursor of the separation-active layer is preferred by Feeding (infiltrating) a crystallization solution which contains the components for the synthesis of the has separation-active layer, in the outer layer of the carrier material and subsequent Crystallization produced. The crystallization solution is preferably fed in such a way that the crystallization solution, the gas present in the pores of the carrier material, usually Air, replaced when penetrating. This measure ensures that in one layer of Support material after the crystallization all the pores are filled by the separation-active layer. The Membranes usually produced without this measure often have air pockets during the manufacturing process of the release-active layer, which in the later Use of the membrane imperfections, i.e. pores with too large a diameter, represent, so that the selectivity of such membrane is deteriorated. With these procedures the gas present in the pores does not have sufficient opportunity to emerge from the pores.

The crystallization solution is preferably supplied by spraying or Drip the crystallization solution onto the support material. It does that the entire surface of the carrier material is simultaneously wetted with the crystallization solution is and thus the gas present in the pores can escape. The intrusion of the Crystallization solution in the carrier material is preferably carried out by simple capillary forces, which suck the solution into the pores. It can be advantageous if on the opposite side of the A negative pressure is generated so that the crystallization solution accelerates in the carrier material is sucked.

In the method according to the invention, it can be advantageous to determine the depth of penetration Control crystallization solution in the carrier material. So z. B. by adjusting the  Viscosity of the crystallization solution the penetration depth of the crystallization solution into the Carrier material can be influenced.

However, the penetration depth of the crystallization solution can also be influenced in particular that a particularly suitable carrier material is used. So it can be beneficial be if the carrier material has a layer, e.g. B. an ultrafiltration layer, which is not permeable to all components present in the crystallization solution. On this Ultrafiltration layer, the carrier material has a further layer as the outermost layer, which is permeable to all components of the crystallization solution, such as. Legs Microfiltration layer. When using such a carrier material, the Crystallization solution with all components only penetrate into the outer layer. By subsequent z. B. hydrothermal treatment with or without subsequent calcination receive a membrane that the separating layer only in the outer layer of the Has carrier material.

It is also possible through the use of carrier materials with layers different chemical properties, such as B. hydrophilized or hydrophobized Have layers to use. The manufacture of substrates, which Have hydrophobized layers, z. B. described in WO 99/62624. Such layers can e.g. B. by adding organosilicon compounds, such as. B. silanes, for sol be made during the manufacture of the layer.

By using such layers, depending on the properties of the crystallization solution, the penetration depth of the crystallization solution can be controlled. Is it z. B. a aqueous crystallization solution, e.g. B. a carrier material can be used, which a has outer layer which has hydrophilic properties and a layer below this outer layer, which has hydrophobic properties. When feeding the aqueous Crystallization solution will mostly only fill the pores of the hydrophilic layer. In the subsequent crystallization and calcination, the separation-active layer is only in the outermost layer arise. By specifying the thickness of the hydrophilic layer, the Set the maximum thickness of the active layer.  

Corresponding membranes can be constructed in a corresponding manner Pages have a certain permeability or separation property.

The carrier material pretreated in this way with the crystallization solution present therein becomes Crystallization is preferably placed in an autoclave in which the carrier material further crystallization solution is brought into contact. Preferably only the side of the Carrier material brought into contact with the crystallization solution, which previously by Spraying or dripping crystallization solution was supplied. Is a carrier material Crystallization solution has been supplied from all sides, so it can be advantageous that Immerse the carrier material in the crystallization solution. Usually as Crystallization solution used the same, which the support material already by spraying or dripping was applied. But it can also be advantageous to use one of the supplied Crystallization solution to use different crystallization solution in the autoclave. By the use of a crystallization solution with a lower concentration than that of the The crystallization solution used can be supplied or sprayed on in an autoclave lower tendency to crystallize can be achieved on the carrier surface. Another advantage a cost reduction is obtained by using the diluted crystallization solution. The use of pure water is not advantageous because the synthesis of the separation active Layer in the carrier material when using pure water in the autoclave is not so Completely in the pores of the carrier material that a flawless separation-active layer succeeds is obtained.

The crystallization can, for. B. hydrothermally at a Temperature of 70 to 400 ° C and a pressure of 0.3 to 200 bar can be carried out. 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 may be advantageous to use the crystallization to support a temperature program. The heating is preferably carried out on the Treatment temperature with a heating rate of 1 to 100 K / h, preferably from 5 to 25 K / h. For the crystallization, the carrier material to which the crystallization solution is fed was, for 12 to 72 hours, most preferably 18 to 36 hours at Leave treatment temperature of preferably 170 to 250 ° C. But they are all too  other methods for crystallizing the above as a separation-active layer connections possible.

It can be advantageous, after the treatment of the carrier material with the Crystallization solution to calcine the membrane obtained. The calcination takes place preferably in the presence of oxygen, e.g. B. 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. This is particularly preferably done Calcine at a temperature range of 340 to 450 ° C for a time of 60 to 120 Hours. To avoid thermal stresses when calcining, it can also be advantageous to heat the membrane to be calcined at a heating rate of 0.1 to 1 K / min, preferably bring from 0.2 to 0.5 K / min to the calcination temperature. As well It can be advantageous to cool the calcined membrane at a cooling rate of 0.1 to 1 K / min. preferably from 0.2 to 0.5 K / min from the calcination temperature to room temperature cool. The calcination may result in the crystallization solutions and thus in the Carrier material existing organic compounds such. B. crystallization aids such as Tetrapropylammoniumverbindungen (TPA compounds) such as. B. TPAOH or TPABr, implemented or burned and expelled from the membrane. Furthermore, it will Crystal structure in the separating layer stabilized by the calcination.

However, it must be noted that when using carrier materials, the Have carbon or natural fibers, these also from the calcination All or part of the carrier material can be removed by combustion or decomposition. Should these fibers are retained in the carrier material, it is advantageous if Crystallization solutions are used in which the membrane is not calcined is necessary because z. B. have no crystallization aids.

The crystallization solution preferably has at least one silicon compound, one Aluminum compound or a phosphorus compound or a mixture of one or more of these connections. The crystallization solution particularly preferably has at least one Silicate, an aluminate or phosphate or a mixture of one or more of these  Connections. The crystallization solution preferably has a silicon to aluminum Ratio from 1 to infinity.

The crystallization solutions can have one or more crystallization aids. As such crystallization aids are, for. B. Tetraallkylammonium compounds such. B. tetrapropylammonium hydroxide or bromide (TPAOH or TPABr), (Me ₄ N) ₂ O, Et ₄ NOH, (Pr ₄ N) ₂ O, or crown ether (18-crown-6, 15-crown-5), tetraethyl orthosilicate or Cetyltrimethylammonium compounds such as (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 The molar proportion of water can be varied when preparing the crystallization solutions, care must be taken to ensure that the crystallization solution remains liquid, i.e. one thing Gel formation should be avoided and that a minimum concentration in the Crystallization solution is not fallen below, otherwise no crystallization take place would. In certain cases it may be necessary or advantageous to use the water against others Exchange connections. So the synthesis of silica sodalite instead of in water in the In the presence of ethylene glycol.

The following table shows typical compositions of Crystallization solutions and the type or structure of the separation-active compound which this crystallization solution can be synthesized. At the specified Compositions are only an exemplary selection, because despite Deviation from the specified compositions receive the compounds mentioned can be. Depending on the type of zeolite desired, the composition of the Crystallization solution to be more or less variable. So the zeolite of the type ZSM-5 can also be obtained if there are deviations in the composition of the Crystallization solution on a component, in particular on silicon dioxide of 100% or more available. The zeolite type NaA, on the other hand, is only obtained if the Deviations from the ideal composition of the crystallization solution are small. For the  Zeolite-A and the ZSM-5 types are each two different possible compositions specified.

The skilled person can see that by replacing part of the elements used, in particular the replacement of aluminum but also 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 ones Compounds, however, have different lattice constants and therefore different pore sizes. moreover can by replacing the aluminum or silicon with other elements such. B. Transition metal elements catalytic properties are generated. A detailed one Treatise on zeolites, their synthesis and their modification can be found e.g. B. in J. Weitkamp and L. Puppe, "catalysis and zeolites: fundamentals 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. So z. B. also a composition of 2 parts of SiO ₂ to 2 parts of Na ₂ O to one part of Al ₂ O ₃ and 120 parts of water to an A-type zeolite and a composition of 10 parts of SiO ₂ to 14 parts of Na ₂ O. one part of Al ₂ O ₃ to 840 parts of water to form an X-type zeolite. In order to achieve the desired pore size, there are of course many types of zeolites, e.g. B. of the ZSM-5 type, A type, X type, Y type, etc., suitable. 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, be from 0.26 nm × 0.57 nm (mordenite) to 0.53 nm × 0.56 nm (ZSM-5) and 0, 76 nm × 0.64 nm (zeolite beta) up to 1.6 nm to 10.0 nm (mesoporous aluminosilicates).

By varying the composition, especially the silicon to aluminum The ratio of pore size and properties of the compounds can also be compared influence. A high Si / Al ratio, often referred to as a module, often leads to that the zeolite has hydrophobic properties.

The selection of the most suitable type of zeolite or the most suitable disconnectively active connection, such as. B. microporous silicate, microporous phosphate or microporous amorphous or crystalline mixed metal oxide, depends on the desired Pore size and after the separation problem itself.

The membrane according to the invention can be used in processes for separating mixtures Compounds or molecules can be used as a separation membrane. In particular, the membrane according to the invention in processes for separating mixtures of compounds or Molecules with the same molecular weight and different structure, such as. B. in Process for the separation of n-butane and isobutane can be used as the separation membrane. The membrane can also be used as a separation membrane in processes for separating particles, Particles, compounds or molecules are used that are of 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 the separation of mixtures from Molelkülen or compounds are the same Molecular weight but different adsorption behavior on zeolite pore walls. at This process is the different adsorption behavior of those to be separated Compounds or molecules in the release-active layer, which in this case are preferred has at least one zeolitic connection, used for separation.

The membranes according to the invention are very particularly suitable for use as Separation membrane when performing pervaporation or vapor permeation processes. These methods are e.g. B. in the separation of alcohol-water mixtures, in particular of ethanol-water mixtures. Pervaporation is a liquid mixture fed to the membrane and the permeate leaves the membrane on the other side as  Vapor phase. With vapor permeation, the mixture to be separated becomes the membrane supplied in vapor form. The separation of ethanol-water mixtures using pervaporation is usually carried out at a temperature of 70 to 90 ° C during the separation is carried out by means of vapor permeation at a temperature of more than 100 ° C. For this method is a membrane according to the invention particularly suitable as a separation membrane, because it has a higher temperature resistance than membranes based on organic Polymers.

The inventive method for producing the membrane according to the invention and the membrane of the invention will be described with reference to FIGS. 1 to Fig. 5 in greater detail, without the invention being restricted to the embodiments.

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

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

Fig. 3 shows a scanning electron micrograph of the fracture surfaces of the untreated support 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.

Fig. 5 shows an X-ray diffraction pattern of the Al ₂ O ₃ support (a) of Al ₂ O ₃ / MFI membrane of 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 Production 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, washed with distilled water 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 from 540 ° C to 250 ° C 0.2 Kmin ^-1 , from 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 Production 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. Subsequently So much crystallization solution was filled in the autoclave 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 with distilled water washed and dried at 120 ° C for 2 hours. A membrane was obtained, which as separating active layer has a layer of the compound zeolite A.

Claims (38)

1. membrane, which has a permeable carrier material and a separating layer, characterized in that the membrane has at least one separating layer in the permeable carrier material. 2. Membrane with at least one separation-active layer in a permeable material Support material by introducing a crystallization solution, which is used for synthesis the separation-active layer has necessary components, in a carrier material, wherein the gases present in the pores of the carrier material from the crystallization solution be displaced from the carrier material, and subsequent crystallization of the separation-active Layer in the carrier material is available. 3. Membrane according to claim 1 or 2, characterized, that the pores of the separating layer have a maximum pore size of less than 10 nm exhibit. 4. Membrane according to claim 3, characterized, 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, that the permeable substrate metal, glass, ceramic or a combination of these materials. 6. membrane according to at least one of claims 1 to 5, characterized,  that the permeable carrier material is woven, non-woven, 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, 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, that the permeable carrier material has a homogeneous porosity. 9. membrane according to at least one of claims 1 to 7, characterized, that the permeable carrier material has an inhomogeneous porosity. 10. membrane according to claim 9, characterized, that the permeable carrier material areas with larger and areas with smaller Porosity. 11. Membrane according to claim 10, characterized, that the areas with larger and areas with smaller porosity build up in layers are. 12. Membrane according to claim 11, characterized, 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, that the separating layer in the forward direction has a thickness less than or equal to the thickness of the carrier material. 14. Membrane according to claim 13, characterized, that the release-active layer has a thickness of 1/10 to 1 / 100,000 of the Has thickness of the carrier material. 15. Membrane according to at least one of claims 1 to 14, characterized, that the release-active layer has at least one compound that Has molecular sieve properties. 16. Membrane according to at least one of claims 1 to 15, characterized, that the separation-active layer has at least one compound made from a natural and / or synthetic zeolite, an aluminosilicate, an aluminophosphate and / or one Has metal aluminophosphate. 17. Membrane according to claim 16, characterized, 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, that the release-active layer in the outermost layer inside the carrier material is arranged. 19. Membrane according to at least one of claims 1 to 17, characterized, that the release-active layer in the outermost layer of all sides of a carrier material in the Inside is arranged. 20. Membrane according to at least one of claims 1 to 19, characterized, that the membrane is flexible. 21. Membrane according to at least one of claims 1 to 20, characterized, that the membrane to a minimum radius of 5 cm without loss of separation properties is bendable. 22. A method for producing a membrane according to at least one of claims 1 to 21, characterized, that a release-active layer is synthesized in a permeable carrier material. 23. The method according to claim 22, characterized, 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, that the release active layer or a precursor of the release active layer by feeding a crystallization solution, which contains the components for the synthesis of the separation-active Has layer in the carrier material and subsequent crystallization is produced. 25. The method according to claim 24, characterized, that the release active layer or a precursor of the release active layer by feeding a crystallization solution, which contains the components for the synthesis of the separation-active Has layer in 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, that the crystallization hydrothermally at a temperature of 70 to 400 ° C and a Pressure from 0.3 to 200 bar is carried out. 27. The method according to claim 26, characterized, 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, that the permeable carrier material is flexible. 29. The method according to claim 28, characterized, that the permeable carrier material can be bent to a minimum radius of 2 cm.   30. The method according to at least one of claims 22 to 29, characterized, that the permeable carrier material has an average pore size of less than 2000 nm having. 31. The method according to at least one of claims 24 to 30, characterized, that the crystallization solution has at least one silicate. 32. The method according to at least one of claims 24 to 30, characterized, that the crystallization solution has at least one aluminate. 33. The method according to at least one of claims 24 to 30, characterized, 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 that have an average size of have 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 that are the same Molecular weight a different adsorption behavior on zeolite pore walls exhibit. 37. Use of a membrane according to at least one of claims 1 to 21 for the Separation of mixtures of compounds or molecules that are the same  Molecular weight have a different geometry or structure. 38. Use of a membrane according to at least one of claims 1 to 21 as a membrane in pervaporation or vapor permeation.