DE2910743A1 - PROCESS FOR PRODUCING SYNTHESIS GAS MIXTURES WITH THE AID OF SEMIPERMEABLES HOLLOW FIBER MEMBRANES - Google Patents

Description

DR. BERG DIPL.-ING. STAPF DIPL.-ING. SCHWABE DL DP .. SaNDMAIR.

PATENT LAWYERS

P.O. Box 860245 8G00 Munich 86 2910743

Attorney's file: 29 851

19. M & z Ϊ978

MONSANTO COMPANY ST.LOUIS, MISSOURI / USA

Process for the production of synthesis gas mixtures with the help of semipermeable hollow fiber membranes

C-07-21-1004 GW

«{089) 938272 Telegrams: Bank accounts: Hypo-Bank Munich 4410122850

988273 BERGSTAi ¹ FPATENT Munich (BLZ 70020011) Swift Code: HYPO DE MM

988274 TELEX: Λ «· * ·« / Λ ι.αλ »Bayej Verdnsbank Munich 453100 (bank code 70020270) 983310 0524560 BERcS 0 S 840/0 637 Postscheck Munich 65343-808 (bank code 70010080)

Description

The invention relates to a method for the production of synthesis gas mixtures, in which semipermeable hollow fiber membranes be used; it also concerns methods of regulating such a procedure.

The invention relates to a method for the production of synthesis gas mixtures, which is particularly advantageous for Generation of gas mixtures with precisely regulated composition »intended for specific synthesis reactions are. It also concerns a new, very flexible control procedure for the composition of such synthesis gases.

There have been many methods of concentrating a less concentrated gas in a mixed gas stream proposed, including refrigeration, absorption of certain Gases in solvents, adsorption of certain gases on solid zeolites, and the like. In general it was however, the concentration and / or purification of hydrogen, helium or other relatively light gases. Membrane separation processes have also been used for the separation of relatively pure streams of hydrogen or other light gases described. Such a membrane separation process is used for the production of synthesis gas mixtures, which subsequently should be worked up further, namely in an oxo reaction or other catalyzed Syntb.ese.reak-

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options.

A mixture is often used for such synthesis reactions Gases like hydrogen and carbon monoxide with an entirely different one Composition required than they have the effluent gases that are used in primary reforming processes of Hydrocarbons are formed, i.e. from natural gases which generally also contain impurities that either damage the synthesis catalyst or the effectiveness of the synthesis reaction removed. Nevertheless, the relative proportions of the primary reaction gases, e.g. hydrogen and carbon monoxide, must still be That can be changed to get the most effective response an almost stoichiometric mixture is present.

This can be done in different ways, e.g. by adding pure or highly concentrated gases from a another source, e.g. of highly concentrated carbon monoxide, or by partial removal of one of the gas components »e.g. hydrogen * In a process suggested for this purpose becomes part of the hydrogen content by means of permeation this light gas is removed through a separating membrane the hydrogen content to a desired ratio to that

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or adjust the other components. There were different ones Types of membrane separators have been proposed to effect such hydrogen removal including flat membranes or hollow fiber devices adapted for contact with gas streams became.

In most of these devices, those desired to have contact with the gas streams gave rise to very large active ones Membrane surfaces, the designers, as membranes are very small hollow fibers with small outer and inner diameters to be provided. For example, in US Pat. No. 3,422,008 fibers with diameters from 0 to 50 µm and at most 300 µm preferred. In US-PS 3,339 3 ^ 1 hollow fibers are with Outer diameters between 20 and 250 μm are particularly preferred, It is also noted that a semi-commercial establishment uses 29.2 µm hollow fibers.

Others have also found that hollow fibers with relatively small outer diameters are advantageous in separating devices can be used, as it provides sufficiently large membrane surfaces as well as other advantages, such as resistance against relatively large pressure differences. For example, U.S. Patent 3,228,8-7 mentions hollow fibers should have relatively small outer diameters and that these are advantageously between 10 and 50 μm.

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At the same point it is described that the pressure difference that a hollow fiber can withstand is more direct Relationship is related to the ratio between the wall thickness of the fiber and its inner diameter, and that, since greater Pressure differentials usually result in a larger flow through the fiber wall, very small hollow fibers that can withstand high pressure differences are desirable are. It is concluded from this that the smaller the fiber diameter, the smaller the corresponding one Wall thickness is necessary to withstand a given pressure drop; that further thinner walls of the Oppose less resistance to permeation and thus allow a greater flow rate than is the case with fibers occurs with greater wall thickness.

It has now been found that for an improved axial or radial flow through a bundle of hollow fibers Fibers with slightly larger inside and outside diameters are desirable. In BE-PS 192 024 it is said that hollow fibers with outside diameters of about 150 to 800 μm for most liquid separations, and especially for gas separations to be favoured. At the same point it is stated that the preferred wall thickness of the hollow fibers is between approximately 50 and 300 μΐη is, and that such hollow fibers are preferred made of material with a tensile modulus of at least about 1.5 N / cm. Furthermore, the fact is

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knows that fibers with a low amplitude crimp result in high packing densities, e.g. J ^ 40%, with a more useful Flow is maintained axially and radially to a bundle of such fibers.

It has been suggested to be built into disconnection devices semipermeable membranes to use to selectively one or more gases from a gas mixture, the at least one additional Contains gas to be separated. The passing (not permeated) The gas mixture is then processed further after the separation process. Put the separator to the river of the gas mixture a substantial resistance, contrary, then Considerable expenditure of energy can be necessary to recycle the gas mixture passing through for further processing to compress to the desired pressure. Pressure drops in a gas mixture caused by the flow resistance of the separator are often considerable when the feed gas mixture is directed to the interiors of the fibers will. For example, Gardner et al. , in "Chemical Engineering Progress", October 1977, 76-78, the Use of a separator containing hollow fiber membranes to remove hydrogen from a hydrogen / carbon monoxide feed stream in an oxo-alcohol synthesis process described. The feed stream with a pressure

2 2

of 2HO N / cm is compressed to a pressure of 420 N / cm, through the interiors of the hollow fibers in the separation

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direction and as a passing stream from the interior of the hollow fibers of the separating device obtained at 230 N / cm. Compression and, in some cases, recompression of the feed gas stream is expensive, which is why the Compressor capital expenditures and operating costs are concerned, and procedures that involve these additional costs can be avoided are clearly desired. In the Gardner example cited above, an essential one arises Pressure drop due to the fact that the feed gas flow into the Separator is fed on the side of the fiber openings; this type of feed is obviously necessary because poor distribution and efficiency losses occur when the feed gas flow to the outside or Shell sides of the hollow fibers would be passed. Feeding the shell side of hollow fiber separators can have other advantages. For example, the outer surfaces of hollow fibers offer a larger surface area for performing the separation than their inner surfaces Hollow fibers can generally withstand higher pressure differentials when the higher pressure is on the outside the fibers act and not on the inside, as in general most fabrics have higher compressive strengths than tensile strengths own.

There have been advantages in using hollow fiber membranes.

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found when these membranes, as described above, have a crimp with a small amplitude and a relatively large outer diameter and wall thicknesses »These advantages are best observed when the feed gas mixture is radial is fed, i.e. the gas mixtures are introduced in the middle section of a hollow fiber bundle and practically flow perpendicular to the arrangement of the hollow fibers; or if the feed gas mixture is introduced predominantly axially, i.e. the Gas mixture is introduced at an outer portion of the fiber bundle, flowing generally in the direction of the fiber arrangement and exits at another section of the fiber bundle. It is often assumed that radial Feed results in better gas separation efficiency, however, the axial feed is often preferred because the Separating device can be constructed more simply than a separating device with radial feed «Since within the bundle no radial feed line has to be accommodated, the Büjidel used for the axial flow can also have a better ratio of available membrane surface area per volume of the separation device * than with a Device for radial feed is the case »

According to the invention it has been found that a process for the preparation of synthesis gas mixtures from feed gas mixtures which have different compositions than those desired for the synthesis process, most advantageously with the help of hollow fiber

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membranes are carried out, which are housed in bundles in separation containers. To generate the desired passing synthesis gas mixture passed an axial flow on the outer or shell side of the hollow fiber. This synthesis gas mixture becomes such on the outside Hollow fiber membranes are peeled off at a point away from the gas entry point, while a permeated Gas flow is derived from the interiors of the hollow fiber membranes. According to the invention it was also found that the most advantageous and flexible regulation of the proportions of the desired gases in the generated gas flows by setting the pressure difference between the the feed gas mixture conducted on the toll side of the fiber membranes and your permaiarten withdrawn from the fiber interior The pressure difference is regulated Often the most beneficial and easiest way to do this is to apply a fixed or constant pressure for the Adjusts the feed gas mixture and the pressure with which the permeated gas stream is withdrawn varies, so as to the entire Pressure difference to vary. According to the invention the composition of the desired gas mixture product passing through determined with an analyzer, and the setting the pressure difference between the gas streams mentioned takes place as a function of changes in the composition of the gas power product passing through.

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For the sake of simplicity, the method according to the invention is used in detail for the production of a Synthesis gas mixture for an oxo-alcohol synthesis described, in which the desired hydrogen: carbon monoxide ratio is about 1: 1. It should be noted, however, that the same process is used for the production of synthesis gas mixtures and for the regulation of gas mixtures also to the production of many and other mixtures of gases besides the two mentioned gases can be used, as well as for other proportions of the gases to one another. The present So invention is not related to the specifically described process for the production of a particular synthesis gas for an oxo-alcohol reaction as shown below is limited.

For the production of an oxo reaction synthesis gas is generally first a source of the main gases required, namely hydrogen and carbon monoxide, which are usually present other gases are mixed in in smaller quantities. Such gas streams can be a by-product of refineries and / or petrochemical processes. Is one of those Source not available, then these gas streams will in general through various catalytic or thermal primary reforming reactions for hydrocarbons, such as Natural gas, naphtha, gas oil or the like. Generated. The proportion of

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various product gases is "varies depending on the kind of the reactant hydrocarbon, the nature of the reforming and the catalyst used is for example natural gas used, and the usual catalysts _s then cleaved are other than hydrogen and carbon monoxide, in general, various other gases such as carbon dioxide, methane ₉ nitrogen and Water present in smaller quantities »Most of these polluting gases are removed from the desired 0xo ~ synthesis gas stream so that the oxo catalyst is not poisoned and the effectiveness of the reaction is not reduced. - "."".."

Bainite competing reactions do not reduce the effectiveness of the oxo reaction process ₉ it is generally thought to be desirable to remove as much as possible of the carbon dioxide that may have been generated in the primary reforming reaction or in the gas mixture from a. other source is available. In general, this carbon dioxide is removed by means of an absorption or washing process, or by means of an adsorption or solids treatment. Any good solvent for carbon dioxide such as water, methanol or monoethanolamine can be used for absorption. In a suitable process, the gas stream is scrubbed with monoethanolamine to remove the carbon dioxide. In another process, the gas stream is subjected to methanol scrubbing * in which case the removed

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Stripped carbon dioxide from the methanol with another gas and thus regenerating the absorbent methanol for reuse. Each of these procedures for Removal of carbon dioxide can be used in the process of the invention if desired, and in general Such a method is used to reduce the carbon dioxide content of a feed gas mixture to below 100 ppm and preferably below 30 ppm carbon dioxide.

Other gaseous impurities in the typical primary reforming product gas streams can, if desired, be removed with any suitable treatment of the gas stream. One suitable method is to use the feed gas stream an adsorption treatment over activated carbon, molecular sieves, zeolites or the like. To be subjected to means Adsorption to remove the other gaseous impurities as well as the methanol that may be from the above Solvent absorption treatments. The adsorbent can then be used as needed regenerated by stripping with a dry stripping gas.

In general, feed gas mixtures that have been generated in primary reforming processes have relatively high temperatures and must be ^{cooled to "near ambient temperature, for example about -50 to 50 °} C., preferably about -20 to 20 ^° C.,

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before the impurities are removed from the gas stream as described above. For carrying out the following method steps, including the contact with the Hohlfasertrennmambranen, ambient temperatures are about preferred. Thus, if desired, the treated feed gas stream prior to contact with the separating membranes to about 10 to 50 ⁰ C, preferably 20 is set to 40 ⁰ C. Depending on the source of the mixed gas stream used, these feed gas streams are also under overpressure. When generated in a primary reforming process, the mixed gas product stream is delivered with an excess pressure of 10 to 100 bar, preferably about 20 to 50 bar. If other sources are used for the mixing flow, then it either has a corresponding overpressure or, if desired, can be compressed to the required pressure. Most advantageously, the mixed gas pass stream is brought into contact with the hollow fiber membrane under practically the same overpressure that is desired for the further use of the synthesis gas obtained. It is even better if the mixed gas feed stream is brought into contact with the hollow fibers under a pressure which is 1/3 to 3 bar above the pressure which is desired for the synthesis gas product stream obtained.

The feed gas mixture containing hydrogen and carbon monoxide whether it is the preferred pretreatment for removing carbon dioxide and other contaminants

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Has been subjected to gases or not, with a hollow fiber separation membrane brought into contact, the selectivity for the permeation of hydrogen over the permeation carbon monoxide and in general all other trace gases. There in the feed gas streams generally much higher volume concentrations of hydrogen than of carbon monoxide are present, the Separating membrane do not have a high separation selectivity for hydrogen over carbon monoxide, thus an improved Process for the production of synthesis gas mixtures is made possible. In general, the separation selectivity a membrane described as the ratio of permeability of the fast permeating gas, i.e. hydrogen, to the permeability of the slow permeating gas, i.e. Carbon monoxide, whereby the permeability of the gas through the membrane can be defined as a gas volume at Stan-

Standard temperature and pressure that is passed through the membrane per cm of surface area per second with a partial pressure drop of 1 cm Hg passed through the membrane per unit thickness. This ratio is called the separation factor of a membrane . The separation factor of the membrane for the permeation of Hydrogen versus carbon monoxide is often at least around 10. Certain membranes can have separation factors for hydrogen to carbon monoxide of 80 or more, however, such highly selective membranes only give poor results

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Advantages. In the most common cases, membranes come with a Separation factor for hydrogen versus carbon monoxide of about 10 to 50 appropriate. The higher the permeability of hydrogen through a membrane, the less effective membrane surface area is required so that a certain amount of hydrogen happened through this membrane. Particularly useful membranes have hydrogen permeabilities of min-

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at least about 1x10, preferably at least about 1x10 cm

Hydrogen per cm of membrane surface per second for one

Hg partial pressure drop across the membrane.

The effective merabran surface should be an amount of hydrogen parmaie.'fen that is so great that in the passing Gas flow the desired hydrogen! Carbon monoxide ratio will be produced. Among the factors that determine the Large affect the effective membrane surface area, belong i.a. the permeation rate of hydrogen under the separation conditions, including temperature, absolute pressure, Pressure difference across the membrane and hydrogen partial pressure differences are to be expected across the membrane.

The hydrogen partial pressure difference across the membrane is a driving force for hydrogen permeation and depends not only on the gas pressure but also on the Hydrogen concentration decreases on each side of the membrane. Advantageous pressure differences across the membrane are included

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at least about 3 bar. However, the pressure difference should not be so great that the membrane is unduly stressed i.e. that it breaks or becomes prone to breakage. In many cases, the pressure differences can be over the Membrane must be much larger, e.g. about 5 to 50 bar. Preferably, the effective membrane surface and the Pressure difference so dimensioned that at least about 30%, preferably about 40 to 80% of the hydrogen in the Mixed gas stream permeate the separating membrane.

In the method according to the invention, the separation container contains Membranes in the form of hollow fiber membranes, where a plurality of hollow fiber membranes arranged practically in parallel in bundles. is; the feed gas mixture is with the outer surface (shell side) of the hollow fiber membranes brought into contact and an axial FIuS- along and around the hollow fiber membrane is discontinued. Such a synthesis gas product flowing out or passing through the shell side from the separation container can have a pressure that is less than 1 to 3 bar, even less than 0.1 bar below is the pressure of the feed gas flow fed into the separation vessel. Since the hydrogen concentration on the The feed gas side of the membrane decreases continuously, while the hydrogen enters the interior of the hollow fiber membrane permeates, but in this, on the other hand, the hydrogen concentrations increase, the hydrogen partial pressure difference changes continue through the hollow fiber membrane

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constantly. This allows the flow raster to flow through the hollow fiber membrane can be used to improve the separation of the hydrogen from the feed gas mixtures cause. The method according to the invention can be the same can advantageously be used in a cocurrent or countercurrent process, but a countercurrent system is preferred worked; the feed stream is guided as an axial flow on the shell side, so that the feed gas stream distributed within the bundle and flowing generally in the same direction as the hollow fiber membranes are arranged. By the countercurrent created by having the feed gas flow at the end the hollow fiber membrane separator introduces, on which Au3stro / n is withdrawn from the interior, becomes an increased Hydrogen partial pressure difference across the hollow fiber membranes maintain; this is due to the fact that the concentration of hydrogen inside the fiber increases, as it flows in the direction in which there is a higher concentration of hydrogen in the feed gas mixture.

The separator containing the hollow fiber separation membranes can have any construction suitable for gas separation which an axial flow around the shell side of the hollow fiber membrane is possible. So the separation container can have two ends be constructed so that the feed gas stream is introduced in the central portion of the separation vessel, and the passing

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Gas is withdrawn from both ends, while the permeated gas stream from the interior is either at one or at one removed from both ends of the separation container. Preferably, the separation container has a construction with a End, in which the permeated gas is withdrawn from the interior only at one end, while the gas passing through is drawn off can be removed from either end of the separation container; the feed gas can enter the separation tank at any point between inserted at both ends. In order to obtain the more desirable countercurrent flow, the feed gas is preferably used introduced at the same end of the separation container at which the permeated gas is discharged from the interior space, and the passing gas is withdrawn at the opposite end of the separation container.

Any suitable material that is selectively permeable to hydrogen over carbon monoxide and other heavier gases can be used for the hollow fiber separation membranes. Typical membrane materials include organic ones Polymers or organic polymers with inorganic substances such as fillers and reinforcing agents and the like. are mixed. Metallic and metal-containing membranes can also be used. Suitable for the separating membranes Polymers can be substituted or unsubstituted Be polymers and be selected from: polysulfones; Polystyrenes, including styrene-containing polymers such as

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Acrylonitrile-styral copolymers, styrene-butadiene copolymers and styrene vinylbenzyl halide copolymers; Polycarbonates; Cellulose-based polymers such as cellulose acetate, cellulose acetate butyrate, Cellulose propionate, ethyl cellulose, Methy! Cellulose, nitrocellulose, etc., polyamides and polyimides, including ary! polyamides and ary! polyimides; Polyethers; Polyarylene oxides such as polyphenylene oxide and Polyxylylene oxide; Polyester amide diisocyanate; Polyurethanes; Polyesters including polyacrylates such as polyethylene terephthalate, Polyalkyl methacrylates, polyalkyl acrylates, polyphenylene terephthalate, etc .; Polysulfides; Polymers from monomers with ct-olefinic unsaturation except the mentioned above, such as polyethylene, polypropylene, polybutene-1, Poly-4-methylpentene-1, polyvinylene, e.g. polyvinyl chloride, Polyvinyl fluoride, polyvinylidene chloride, polyvinylidene fluoride, polyvinyl alcohol, polyvinyl esters such as polyvinyl acetate and polyvinyl propionate, polyvinyl pyridines, polyvinyl pyrrolidones, Polyvinyl ethers, polyvinyl ketones, polyvinyl aldehydes xiie polyvinyl formal and polyvinyl butyral, Polyvinylamides, polyviny! Amines, polyviny! Urethanes, Polyvinyl ureas, polyvinyl phosphates and polyvinyl sulfates; Polyallylene; Polytriazoles; Polybenzobenzimidazoles; Polycarbodiimides; Polyphosphazines; etc., and copolymers including Blockmisehpolyn-iren, the repetitive Contain units of the above substances, such as »B, Terpolymers from acrylonitrile vinyl bromide sodium salt des

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p-sulfophanyl methallyl ethers; also graft polymers and mixtures containing the above-mentioned substances. Typical substituents for substituted polymers are e.g. Halogens such as fluorine, chlorine and bromine, hydroxyl groups, lower alkyl groups, Lower alkoxy groups, monocyclic aryl, lower acyl groups and the like.

The material of the hollow fiber membrane is preferably as thin as possible in order to reduce the rate of permeation through the To improve the membrane, but so thick that the hollow fiber membrane is stable enough to withstand the separation conditions, including to withstand the pressure and partial pressure differences used. Hollow fiber membranes can be isotropic i.e. they can have the same density throughout; however, they can also be anisotropic, i.e. they can have at least one zone with a greater density than at least have a different zone of the fiber membrane. The hollow fiber membrane can be chemically homogeneous, i.e. constructed from one material, but it can also be a composite Be membrane. Suitable composite membranes can consist of a thin layer which causes the separation consist of a porous support that the hollow fiber membrane gives the necessary strength to withstand the separation conditions. Other suitable composite hollow fiber membranes are the multicomponent hollow fiber membranes described in BE-PS 860 811. These membranes are made of

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a porous separation membrane, which essentially causes the separation, and a sealing material Bes that with
the porous separating membrane has occlusion contact. These
Multicomponent diaphragms are particularly useful for gas separations, including the separation of hydrogen from carbon monoxide and other heavier gases, as one can use
they can achieve good separation selectivity and strong flux through the membrane.

The substances for the coating of these multicomponent membranes can be natural or synthetic substances; they are often polymers which advantageously have the properties desired for occlusive contact with the porous separating merabran. Synthetic substances include both addition and condensation polymers. Typical substances which can be used for the coating are polymers, which can be substituted or unsubstituted, and which are liquid or solid under the conditions for the gas separation. These include: synthetic rubbers, natural rubbers, liquids with high molecular weight and / or high boiling point, organic prepolymers, polysiloxanes, silicone polymers,
Polysilazanes, polyurethanes, polyepichlorohydrin, polyamines, polyimines, polyamides including polylactams, acrylonitrile-containing copolymers such as poly ~ {α-chloroacrylonitrile) copolymers, polyesters including polyacrylates, for example polyalkyl acrylates and polyalkyl methacrylates, in which the alkyl groups

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Have 1 to about 8 carbon atoms; Polysebacate, Polysuccinates and alkyd resins, terpinoid resins, linseed oil, Cellulose-based polymers, polysulfones, especially "polysulfones" containing aliphatics, polyalkylene glycols, such as Polyethylene glycol, polypropylene glycol, etc .; Polyalkylene polysulphates, Polypyrrolidone, polymers of monomers with α-olefinic unsaturation such as polyolefins, e.g. Polyethylene, polypropylene, polybutadiene, poly- (2,3-dichlorobutadiene), Polyisoprene, polychloroprene, polystyrene including Polystyrene copolymers, e.g. styrene-butadiene copolymers, polyvinyls such as polyvinyl alcohols, polyvinyl aldehydes, e.g. polyvinyl formal and polyvinyl butyral, polyvinyl ketones, e.g. polymethyl vinyl ketone, polyvinyl esters, e.g. polyvinyl likewiseate, polyvinyl halides, see B. Polyvinyl bromide, Polyvinylidene halides, polyvinylidene carbonate, Poly- (N-vinylmaleimide), etc., poly-CljS-cyclooctadiene), Poly- (methylisopropeny! Ketone), fluorinated ethylene copolymers, Polyarylene oxides, e.g. polyxylylene oxide, polycarbonates, Polyphosphates, e.g. polyethylene methyl phosphate, and the like, as well as all copolymers, including block copolymers, containing the above-mentioned repeating units, and graft polymers and mixtures, the above-mentioned Contain substances. Once applied to the porous separation membrane, the polymers may or may not be polymerized.

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In the method according to the invention, the desired product synthesis gas that is withdrawn from the separation container and thus from the outer surface of the hollow fiber membranes has a reduced hydrogen content compared to the feed gas mixture introduced into the separation container. It is also drawn off at a pressure that is only very slightly lower, mostly only 0.1 to 0.3 bar, than the pressure at which the feed gas mixture was introduced into the separation vessel. This is due to the very low pressure drop is created by the axial flow of the gas stream through the separation vessel and around the outer surfaces of the hollow fiber membranes present therein. By using the process according to the invention, a very different composition of the synthesis gas product passing through can be achieved; this depends on the composition of the feed gas mixture, the flow rate of the feed gas mixture and the pressure difference maintained between the feed gas mixture and the interior spaces of the hollow fiber membrane and thus the pressure difference between the outside and inside of the hollow fiber membranes; Hydrogen partial pressure difference .ab

Any feed gas composition whose hydrogen content is in the Relation to the other gaseous constituents flows away geri: is to be, can with the method according to the invention be treated. In the special case where a syn-

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thesegas is desired for an oxo synthesis reaction, a feed gas composition in which the stoichiometric ratio of the molar volumes of hydrogen: carbon monoxide is too large can be used as the feed gas. Generally such feed gases have hydrogen: carbon monoxide ratios from about 1.3: 1 up to H or 5: 1. In the process according to the invention, any desired flow rate can be maintained in the separating containers used by varying the size and number of the containers used. It is evident that increasing the flow rates within a single vessel reduces the possibility of permeation for the hydrogen portion of the feed gas mixture.

The pressure difference that exists between the feed gas stream and the permeated flow inside the hollow fiber membranes will hold, is the main variable in the inventive Process and represents the most advantageous control element for the composition of the synthesis gas product passing through represents. So it was found that the pressure difference can be only 5 bar to even 70 bar and more, depending on the Strength and resistance to breakage of the hollow fiber membranes used. The pressure of the feed gas mixture - i.e. the The gas fed into the separating vessel on the shell side can be between about 5 and 70 bar, preferably

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however between about 8 and 50 bar, preferably between and 30 bar. On the other hand, the pressure of the permeated gas flow in the interior of the hollow fiber membranes can be about 1 to 50 bar, preferably 1 to 20 bar, and more preferably 1 to 10 bar. So the pressure difference becomes preferably between about M- to 30 bar and even better held between about 10 and 20 bar.

By appropriately setting the pressure difference, in the method according to the invention, a passing sy nth es gasstrom be regulated with great flexibility so that a composition is created in which the ratio Hydrogen: carbon monoxide between 0.8 and 3.1 or more can be varied, depending on the composition of the spa gas flow. For most synthesis gas mixtures, intended for use in an oxo reaction process are, and depending on other gas mixtures that can be mixed therewith, the composition can be adjusted to a hydrogen: carbon monoxide ratio of about 0.9 to 2.1. Should no other gas streams are mixed, the composition of the passing synthesis gas stream is preferably adjusted to a ratio Hydrogen: carbon monoxide adjusted from about 1.0 to 1.2.

Such passing synthesis gas streams were found to be very suitable and beneficial for direct use

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in a synthesis reaction for oxo alcohols, in which a Cobalt Oxo Catalyst is used. Are auxiliary gas flows available, which is mixed with the passing synthesis gas stream to form the final synthesis gas for oxocatalysis then are the streams with greater possibilities for variation in the hydrogen: carbon monoxide ratio as described above, very suitable and useful.

At the same time, a permeated gas flow is generated from the inner spaces of the hollow fiber membrane, which is relatively higher hydrogen content than that in the separation tank has fed feed gas mixture. In general, this hydrogen-rich permeated stream contains at least one 80% by volume hydrogen. More often, and depending on the relative permeability of the particular hollow fiber membrane used for hydrogen versus carbon monoxide, such a permeated gas stream contains over 90% by volume of hydrogen. most often about 92 to 96 volume percent hydrogen. The hydrogen rich permeated gas stream is suitable for any desired application in a specific device. So can e.g. these dry hydrogen gas streams for regeneration used by molecular sieve adsorption units by purging the polluting gases previously adsorbed thereon. Likewise with these Hydrogen streams the carbon dioxide solvents such as

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ethanol or monoethanolamine are regenerated from which the absorbed carbon dioxide is stripped out »These permeated Gas streams are suitable for all other applications for which a hydrogen stream of relatively high purity is needed.

As already mentioned, the regulation of the pressure differences between the feed gas mixture and the permeated gas flow in the interiors of the hollow fiber membranes with each appropriate procedures may be performed including adjusting the compression applied to the feed gas stream odar, more simply, by setting the sustained Use the control valves to press in the hurried streams. As the simplest method of regulation this pressure difference often turns out to be the setting of a stabilized pressure for the feed gas mixture and then changing the pressure maintained in the interiors of the hollow fiber membranes Setting of suitable valves in the line with the permeated gas immediately downstream of the separation vessel. Such a regulation of the pressure of the permeated gas flow and thus the pressure difference across the entire separation tank occurs in response to changes in the composition of the passing synthesis gas stream that one on the shell side of the separating device .. So once there is a desired composition, i.e. a specific one Hydrogen: carbon monoxide ratio has been established »

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then any deviation from this desired ratio leads to adapt the pressure exerted on the permeated gas flow in the interior. A desired Composition can e.g. * the highest possible carbon monoxide content provide in the passing synthesis gas stream, whereupon the pressure on the permeated gas stream is then adjusted to the lowest value for the subsequent desired processing of this permeated gas stream is required.

For the analysis of the passing synthesis gas stream can any suitable method can be used. Manual analysis with liquid reactants is generally too slow to influence the setting of the required pressures. However, there are various analytical methods with which rapid changes in carbon monoxide and / or Hydrogen content of the passing synthesis gas stream determined can be. A writing gas chromatograph is most suitable. In the preferred embodiment of the process according to the invention is such a gas chromatograph connected to a signal transmitter. This signal is used to control the setting of the valves that control the Check the pressure of the perfused gas flow from the interior. Such a signal from a process control analyzer such as a gas chromatograph can be can also be routed to a process computer, which

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on the other hand, a signal for the regulation of the valve system generated the line for the permeated gas stream from the separation container. Such control circuits for the Process control with the aid of gas chromatograph analyzers are known and will not be discussed in detail here.

The method according to the invention was used here on a method for producing a synthesis gas mixture described; however, it is clearly evident that the aspect of process control by adjusting the pressure difference between the feed gas mixture and the perms.ia? tan gas flow to regulate the composition of a pausing gas mixture to many different gsmischa of feed and product gases can be applied. So is for every gas separation system where there is a passing gas mixture for further processing or treatment after the permeation of a lighter, more selective permaabien Gasas from the original feed gas mixture is desired, such a method for controlling Gases particularly advantageous. Such passing gas mixtures can consist of any other group of gases., which are less selectively permeable than a lighter gas, whose concentration in the passing gas flow is to be reduced · The same control system for gases can can also be applied to systems with the same advantage

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for which the permeated gas is the main flow, which is for the further implementation or treatment is desired. In such a case, too, the regulation depends on the analysis values of the gas flow passing through in relation to the proportion of the desired Gas or one of the other main gases present in the gas stream passing through, and the regulation takes place likewise with the aid of the pressure of the permeated gas stream.

Whenever, for example, excess hydrogen from different Refining or petrochemical processes such as hydrocarbon hydrogenation are to be obtained, then Such a method can be used to regulate the gas flows from gas separation processes with hollow fiber membranes will. The possible uses of the inventive Methods for regulating mixed gas flows are diverse and the benefits are apparent from a number of industrial processes.

The following examples are intended to explain the invention in greater detail. Unless otherwise stated, all data relate to about shares and percentages on the volume.

Example 1

A binary mixture of 75 mol% hydrogen and 2 5 mol% Carbon monoxide was treated in a separation container, the

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anisotropic celijilose acetate hollow fiber membranes with a Inside diameter of 100 μm, an outside diameter of 300 µm and a wall thickness of 100 µm, of which less than 10 μm made up the dense, anisotropic coating. The hollow fiber membranes had an effective upper

2
area of about 9600 cm. The separation vessel was immersed in a bath at a constant temperature of 23 ⁰ G. The pressure of the feed gas on the outer surface of the hollow fiber merribran was varied by a pressure regulator, and the pressure on the inner space was kept at a fixed value. There have been two gas streams (of passing and 'permeated) given below Züsammensetzurxgsn erzeuji ^4, 2r_it specified dan Druckünterschieden-.zwischen-. The jacket and inner space of the membranes, and the feed gas mixture at ESSO speeds of 18.5 to 19.2 1 / mih. The separation factor determined from the specified flow and the calculated permeabilities of each gas component is listed in Table I below *

Happening al) CO Table I ■ Separating factor 45.8 Pressure lower (Mant 26 _: Perraeiert H "/ CO 40.8 parted cash nol% 31, (Inner space) ζ. 86.5 38. raol%. 73.9 , 0 H _n CO 3.3 68.0 , 0 94.5 5.5 6.7 60.9 »9 95.9 4.1 10.0 97.6 2.4

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71 , 5 25th , 6 2 ,8th O ,1

~ ** Γ 2310743

Example 2

One obtained from a primary reforming process of natural gas Feed gas washed out with methanol and passed through a bed of zeolite, and the following Composition was treated to partially remove its hydrogen content.

Components mol%

Hydrogen carbon monoxide methane

nitrogen

The separation container contained poly (siloxane) coated anisotropic polysulfone hollow fiber mera, which were made essentially as in Example Gh of the above-mentioned Belgian patent. They had an inner diameter of 250 _ym} μπι an outer diameter of 500 and a wall thickness of 125 pm. The hollow fiber membranes had an effective surface area of about 5500 cm. The hollow fiber membranes had a calculated separation factor for hydrogen versus carbon monoxide by HS, H. The separation container contained about 1200 individual fiber membranes.

The separation unit was operated in the axial Sieichstrom, the gas flow passing through from the shell side of the membrane was withdrawn at the same end of the separation container,

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such as the permeated gas flow from the interior of the * membranes, while the feed to the shell side took place at the opposite end of the container. The separation unit was operated in all runs at a Ursgebungstemperatur of about 25 ⁰ C. The pressure of the feed gas mixture of the above composition and the passing and permeated gas streams were continuously controlled. The composition of the passing and the blocked gas stream was also continuously determined using gas chromatographs. All data were monitored with an IBM Model 1800 process computer and flow rates, pressures, and composition of passing and permeated gas were checked every 3 minutes during a run. The tanning unit was operated continuously for a period in excess of 1200 hours.

The pressure difference between the jacket outlet pressure, which was kept constant at around 19.3 bar, and the inner chamber outlet pressure was changed in steps of about 1 bar from about 10.3 to 6.41 bar to switch between the jacket inlet and interior vent pressure differences from 9.0 to To generate 12.9 bar. The flow rates of the gas having the above composition became within one Range from approximately HOOO to 9000 standard square meters / min the listed pressure differences varies. It was

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found that the pressure drop between jacket inlet and jacket outlet (passing gas) of the separation vessel varied only minimally within the tested pressure differences and flow rates; he was in the mean at about 0.07 to 0.09 bar, within a range of 0.06 to 0.12 bar.

Table II shows the results of 2 8 runs, which have been carried out for long enough to practically operate under equilibrium conditions to create. The feed gas flow rate, pressure differences, H ^ / CO ratios are listed passing gas, hydrogen content of the permeated gas,% hydrogen, dis in the permeated gas. were directed and% carbon monoxide recovered in the passing gas stream.

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Table II

Feed pressure sub- ratio H content% H ₂ in the% C0 in the speed differed! HL / CO in the permeated passing

Through- standard bar passing gas gas gas

run cm / m in gas

1 4055

2 4050

3 3998

4th 3922 "

5 4067

«0 6 5000

O 7 5000

* ° 8 5010 xi, w -, -

■ * ■ 9 4962 12.14 0.81, 89.4 80.2 Vb, b £ o

£ 10 4998 "*" ■ «·" »■ osR 84.6 72.2 **.

«% 1.1 6037

O 12 6033

«. 13 6004

^ω 14 6003

"^. 15 '6027

16 69 7 2

17 7000

18 7069 19, 6973 20 .8058

: 21 8044

^ 22 8017.

ö 23 ^: 7862

O 24 8023, 19.98 0.76 si, υ »« ■, «. -, -.

2 25 9000 " ^Λ - ^{ηΛ Λ} ^ ⁰

Q , 26 9091

Hr- _ < 27 9147

2-8 8926

8th, 99 10, 0 11 0 12, 14th 12, 98 8th, 99 10, , 0 11 , 0 12, , 14 12th , 98 .8th. , 99 10. , 0 ■ ii. "O 12th , 14 12th , 98 8th , 99 10 , 0 11 , 0 12th , 98 8th , 99 10 , 0 .. 11 , 0. 12th , 14 12th , 98 8th , 99 11 , 0 12th 12th .98,

■ ι, 07 O, 98 O, 88 O ₅ 72 O, 67 1, 15th 1, 04 O, , 98 O, .81, O, , 72 1. , 31 : ■■■■ 1. , 14 " 1, , 09 . 0, , 86 ■ .. 0 , 73 1 , 37 1 , 31 ' 1 , 01 0 , 81 ■ '■' .1 , 40 , ^! ι , 36 ■ ■ 'ι , 19 :. ; ■. ■ ■ ο , 9S 0 , 76 '■■■ .i , 46 1 , 31 0 , 99 0 , 79 ■

88.0 65.0 79.4 87.1 73.9 73.3 87.7 76.9 72.6 86.0 83.9 68.1 87.0 86.7 66.9 89, 1 63.1 82.3 89.5 68.3 80.8 89, 3 74.5 76.6 89.4 80.2 75.8 88.8 84.6 72.2 90.0 59, 8 83.7 90.8 65.8 84.0 ** 7
90.6 72.0 80.2 91.4 , 76.0 82.5 7, ■
90.2 83.0 80.1 ■ ^w 7 -
91.2 56.8 86.4 91.7 62.2 85.7 91.9 69.9 85.4 7,
91.3 80.6 80.1 92.1 52.9 89.2 92.2 60.6 86, 8 '92.7 ,., 65.7 86.6 92.9 ■ 70.1 84.3 ^v * -, 7 ■
91.0 70.0 86.0 '9 3.1 50.5 91.0 93.7 S2.3 88.9 93.5 70.2. 88.2 Y 7
93.5 76.2 86.4

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Example 2B .

A series of 4 runs was made with the one described above Separation unit carried out. It was operated in both cocurrent and countercurrent systems. The flow rates were between 5000 and 9000 Standard cm / min and the pressure differences varied between 8.96 and 12.07 bar. The runs in these comparisons obtained results for% hydrogen that was diverted into the permeated gas and for% CO that was in the passing gas are collected in Table III. It can be seen that when operated in a countercurrent system the proportion of hydrogen diverted into the permeated gas is consistently higher, and that in the gas passing through it The amount of CG gained is generally somewhat improved.

Table III '

Feed- direct current G egans.tr pm Schwindig- pressure- ^ H ^ in the% C0 in% Kid ·% C0 idness under- pefmeiert the pass- psrneier- passie-through-standard different gassing te gas rende

run cm / mm 9 bar 64 , 0. gas "O 73 , 6 gas 8th A. 5000 9 , 14 58 , 3 81 ,1 68 »9 84, 4th B. 7000 , 11 85 88

Example 3

A plant for synthesis gas production from 15 separation tanks was provided. These contained anisotropic Multicomponent hollow fiber membranes made of polysulfone with a

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Molecular weight over 10,000 coated with poly (siloxane). This had to be before networking a silicone rubber having a molecular weight of over 1000. The membranes were produced as described in Example 2. The hollow fiber membranes had an inner diameter of about 265 to 295 μm, an outer diameter of about 535 to 575 pm, wall thicknesses of about 125 to 150 μm, and each Bundle had an effective surface area of about 93 m *

The plant was operated for 3 months; during this time relatively stable conditions were maintained with the help of an automatic control system. The plant had a branch that conducted feed gas to three head pieces, each of which supplied an assembly consisting of 5 separators, which were operated in axial countercurrent. The gas passing through was collected with three headers and a branch, which, after mixing with other gas streams, was used as synthesis gas for an oxo-alcohol synthesis process. The permeated gas was collected from the interior of the hollow fiber membranes with the help of three headers and a branch and passed on for further processing. The dry feed gas line to each separator and each head piece for permeated gas were provided with devices for taking samples, which transmitted signals to an automatic analyzer.

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continuously recorded information on composition and pressure. Also the branch that is made by the three headers for passing gas was supplied, was equipped with a device for sampling, the signals to a gave separate, automatically and continuously working analyzer; this was for the procedural regulation with coupled to a process computer. The process computer gave a signal to a pressure control valve in the manifold for permeated gas in response to any deviation from the fixed carbon monoxide content in the gas stream passing through, detected by the separate automatic analyzer. The regulation of the wtirda procedure in Dependence on the composition of the passing gas · ^ Current by varying the pressure difference that passes through the pressure of the permeated gas was adjusted.

The separation unit was operated at ambient temperature of 30 to tj-0 ⁰ C in the axial reverse flow under realtiv stable conditions. The nature of the regulation of the process is represented by two sets of data recorded at an interval of 20 days with continuous operation. The recorded conditions and data are summarized in Table IV; the control of the carbon monoxide content in the gas stream passing through was at a fixed level

Value of 36.0 mol% set,

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Table IV

Day 1 - separation factor H ₂ / CO a 23.5

Flow rate feed gas composition mol%
pressure ΔΡ Feed Passing Permexertes kg / h par bar gas gas gas

1402 22.21 14.47 H ₂ 73.9 59.5 94.0

36.0 5.1

14th , 47 H ₂ 73.9 CO 23.0 ' ^C \ 2.9 ^N 2 0.3

_φ CH ₁₊ 2.9 4.2 0.5

0.2 0.5

^ Day 20 - separation factor H ₂ ZCO = 23.5

1385 22.08 14.4, H ₂ 72.7 59.8 94.1

"**" CO 24.0 36.0 5.4

CH ₁₊ 3.2 '4.1 0.4

■ '.', ■ ■ '■■'''. :, '■''. .N ₉ /. 0,1, ■ '; ■, 0.2 ■■, ■. '■ ^; 0.1.

During another period, the same procedure was followed so as to reduce the feed gas velocity greatly could be mastered. In this case, the fixed control value was set to a lower value, to adapt it to the new situation. It was about 4.5 hours needed to achieve a lower operating equilibrium. The data recorded at 30 minute intervals during this period are summarized in Table V; she refer to Spexsegasfl5.e.ßgesehätze, pressure des permeated stream and C0 content of the passing stream. The first number in front of 3 3 mol% represents the initial control value while 29 mol% CO means the final control value for the process layout under equilibrium conditions.

Feed gas
flowing
windy
speed
Wh Table V Passing gas
eo content
mol% Time
min 1610 Permeated gas
pressure
bar 33 0 1134 6.74 24 30th 1140-1220 6.74 28 60 1140-122Q 6.74 27 90 1140-1220 6.74 27 120-210 1140-1220 6.74 27 240 1180 6.00 29 270 1180 6.00 29 300 6.08

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Claims (1)

Claims 1. Process for the production of a synthesis gas mixture, characterized in that a feed gas mixture is present which contains at least hydrogen and contains carbon monoxide, this feed gas mixture is kept under excess pressure, this feed gas mixture with the outer surfaces of a large number of semipermeable carbon fiber membranes, which are used for Hydrogen are selectively permeable at overpressure, in Contact is made, a portion of the hydrogen present in the feed gas mixture selectively through and into the hollow fiber membranes Interiors permeated, after contact with said outer surfaces, a passing synthesis gas stream is withdrawn, the hydrogen content of which Is reduced and which is at least suitable as part of a synthesis gas mixture, a permeated stream with a relatively high hydrogen content and a lower hydrogen content from the interior of the hollow fiber membranes Pressure is withdrawn, and the composition of the synthesis gas stream passing through by adjusting the pressure difference between the -Il »(089) 938272 Telegrams: Bankconisn: Hypo-Bank Munich 4410122850 938273 BERGSTAPFPATENT Munich (BLZ 7CO20011) S-νΙΛ ("ode: HYPO DE MM 938274 TELEX: "Bayer. V; r» insbank Munich 453! OO (bank code 7ÜU2027O) 933310 0524560 BERC ^ _{Λ QQ} . _ / Λ Λ · »·> Postsehecs Munich 63343-SCS (bank code 700ICOSO) ςτ Q U IJ / Π fj -J? ι BATH ORIGINAL - *? - 2810743 The feed gas mixture flowing around the outer surfaces and the permeated Electricity is regulated. 2. The method according to claim 1, characterized that the composition of the passing synthesis gas stream by adjusting the pressure of the permeated stream is regulated. 3. The method according to claim 2, characterized in that the pressure of the permeated stream is adjusted by valve systems in response to a signal from a gas composition analyzer Device is generated. H. Method for regulating gas compositions, characterized in that a feed gas mixture is present which contains at least two gases under overpressure, this feed gas mixture into a separator and into Contact with the outer surface of a variety of semi-permeable Hollow fiber membranes is brought, wherein the separation container has at least one inlet opening, through which a gas mixture can be selectively passed onto the outside of the hollow fiber membranes, furthermore at least an exit opening through which the gas mixture is drawn off from the outside of the hollow fiber membranes - / 3 909840/083? BATH ORIGINAL, den can, and an opening through which selectively a permeated Gas from the interior of the hollow fiber membranes can be deducted » an axial flow is created along the outer surfaces, wherein the plurality of hollow fiber membranes consist of a bundle semipermeable hollow fibers consists of at least for one of the gases versus at least one other the gases are selectively permeable, a portion of at least one gas of the feed gas mixture permeates selectively through the hollow fiber membranes and into their interior spaces, a gas mixture passing through is withdrawn from the outside of the hollow fiber membrane at a significant excess pressure, its content of at least one of the gases is reduced is, . at a lower pressure from the interior of the. Hollow fiber membranes, a permeated gas stream is drawn off, and the composition of the gas mixture passing through Adjustment of the pressure difference between the feed gas mixture and the permeated gas flow is regulated. 5. The method according to claim 4, since you r c h characterized in that the composition of the passing Gas flow is regulated by adjusting the pressure of the permeated gas flow. 909840/063? BATH ORIGINAL 6. The method according to claim 1, characterized that the feed gas mixture with the outer surface of a plurality of semi-permeable hollow fiber membranes is brought into contact, which are selectively permeable to hydrogen at overpressure and have a diameter from about 150 to 800 ym and a wall thickness of about 50 to 300 μια have. 7. The method according to claim 6, characterized in that the semipermeable hollow fiber membranes of a porous hollow fiber separation membrane and a Coating exist on their outer surface. 8. The method according to claim 7 »characterized that the porous separation membrane contains polysulfone. 9. The method according to claim 7, characterized that the coating contains poly (siloxane). 0Ü984O / OB1? BATH ORIGINAL