FI74884B - SAETT ATT SEPARERA GASER ELLER VAETSKOR. - Google Patents

Description

1 74884

Method for separating gases or liquids

The present invention relates to a method for separating gases or liquids from gas or liquid mixtures containing them. The invention is based on the fact that the desired gases or liquids are absorbed into a microporous gel which is an aromatic, crosslinked homopolymer or copolymer, the intrinsic polarity of which has optionally been altered by an aromatic substitution, addition, removal or reduction reaction of the electrophile.

When it is desired to separate predetermined gases or liquids from gas or liquid mixtures containing them, it may often be practical to absorb the desired gas or liquid into an absorbent with which the mixture is contacted and from which the absorbed gas or liquid can be subsequently released.

The present invention relates to a method of carrying out such a method and is characterized by the choice of absorbent. The invention could also be defined as an absorbent intended for the purpose in question.

In the case of purification of gas or liquid mixtures from undesired components, activated carbon is by far the most widely used absorbent. However, activated carbon is relatively difficult to regenerate for reuse and is downright unsuitable for use when monomers need to be separated from the mixture, as monomers usually polymerize spontaneously on carbon and therefore reduce the efficiency of carbon during reuse.

The present invention proposes a completely new type of absorbent for gases and liquids, namely the so-called macro-porous gels.

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By macroporous gel in this context is meant a polymeric material in the form of particles which has a permanent porosity in the dry state, due to which its specific surface area is greater than 50 m / g. The fact that macroporous gels are composed of particulate materials of relatively small particle size is not relevant to their definition, because it is the specific surface area due to porosity and not the outer surface of the particles that gives the macroporous gel its useful specific surface area. It can thus be considered to be more or less independent of the average diameter of the particles.

However, in the following method of preparing macroporous gels, particles having an average diameter of 0.09 to 0.5 mm are obtained without special measures.

The preferred general method for preparing macroporous gels in this context is based on the suspension polymerization of the monomers to be formed into the base polymer of the macroporous gel in the presence of an inert component, which may be, for example, a solvent, a precipitant or an inert polymer. The polymerization is carried out under conditions such that the inert component is finely divided into polymer particles obtained by polymerization. After polymerization, the inert component is removed by evaporation, dissolution, or some other means, leaving the desired holes, i.e., pores, in the resulting polymer particles.

In order for the general method for preparing macroporous gels outlined above to actually work, the polymer forming the macroporous gel must have the correct composition so that the porous structure obtained after removal of the inert component remains unchanged even after the removal of the inert component. This means that only polymers in which the polymer chains form a rigid interconnected network of 11 3 74884 are eligible. For this reason, reticulated aromatic polymers are definitely preferred.

It has now been found that macroporous gels formed from aromatic crosslinked homo- or copolymers are suitable absorption agents for aromatic agents such as styrene, toluene and xylene. Namely, these can be prepared so that their pore size is suitable for these compounds.

Each polymer is more or less polar depending on its own composition. This in turn means that the polymer in question is more or less prone to absorb other molecules, compounds or components.

It has been found that macroporous gels, due to their open structure, are particularly suitable for this purpose, provided, of course, that they are given the appropriate polarity for each purpose.

It has long been known that the polarity of a polymer can be varied by adding polar so-called functional groups. Thus, in theory, it is possible to incorporate functional groups into a macroporous gel to make it more or less suitable for absorbing certain polar molecules, compounds or components.

The general process for the preparation of polymers containing different functional groups starts from the polymerization of monomers containing these functional groups. However, in most cases this method has to work with expensive and difficult-to-polymerize monomers, which, moreover, are difficult to handle.

However, it has been found that macroporous gels formed from crosslinked polymers with aromatic rings can be modified in a purely chemical manner by a surprising number of reactions, thereby adding a surprising number of different functional groups to the aromatic rings. This also means that unwanted groups can be removed. This invention has provided entirely new possibilities for the preparation of macroporous gels of the desired polarity.

Thus, it has been found that functional portions such as NO 2, SO 2, H, Cl, Br, J, acyl, alkyl and CH 2 Cl can be introduced into the porous gels formed from crosslinked aromatic homo- or copolymers by conventional electrophilic aromatic substitution.

Among the compounds suitable for absorption into the aromatic macroporous gel modified as described above, mention may be made of acetone, methyl ethyl ketone, vinyl chloride, isobutanol and the like.

It has also been found that other functional groups, such as an amino or nitrile group, can be introduced into the aromatic rings in the macroporous gel in a second step, by means of a conventional substitution or addition reaction. Thanks to the present invention, it is also possible to combine the above reactions. Thus, it is entirely possible to introduce both a nitro and a nitrile group into the aromatic rings of a crosslinked aromatic macroporous gel. In this case, first the functional group Br and then the NO 2 group are introduced into the aromatic rings by aromatic substitution of the electrophile, after which Br is substituted by a nitrile group.

If, on the other hand, an amino group is desired, the nitro group is first introduced by aromatic substitution of the electrophile, after which it is reduced.

The amino acid is introduced into the gel in a similar manner so that the introduced bromine or nitro group is replaced by the desired group, i.e. 74884 5 which contains the amino acid.

Modification of crosslinked macroporous gels in the form of particles has proven to be simpler to perform if the particles are almost equal in size. In this case, an equal reaction time and an equal reaction result are obtained. A completely uniform particle size is called a monodispersion. However, the possibilities for producing a fully monodispersed material are only theoretical. Therefore, a material consisting in the relevant particle size range of 0.09 to 0.5 mm of at least 80% of particles deviating from the mean by no more than 0.2 mm is referred to as a "near monodispersion". Such a nearly monodispersed macroporous gel can be prepared, albeit with some labor.

The most complete monodispersion possible is not only advantageous in the case of the modification of a macroporous gel, but is also of great importance when it is desired to utilize coarse-grained gels for the absorption of some gases or liquids from the mixtures containing them.

The infinitely large surface area of the macroporous gel thus makes it a very suitable absorbent. While easy methods have been found to change the polarity of crosslinked aromatic macroporous gels, it has become possible to prepare absorbents that can be used to separate a wide variety of gases and liquids. A further advantage of the method according to the invention is that the crosslinked aromatic macroporous gels are so easy to regenerate. It is usually sufficient to blow warm air of about 120 degrees per gel. It is preferred that the absorbent be heated by a gaseous medium such as air, an inert gas or water vapor, as the same medium is used to introduce heat and drive away the absorbed component when the absorption forces release their grip.

6 74884

The invention can thus be briefly defined as a method by which gases or liquids can be separated from gas or liquid mixtures by absorption into a macroporous gel which is a crosslinked aromatic polymer, the polarity of which may have been changed in order to increase the absorption tendency of the gas or liquid. Thus, the polarity is altered in the desired amount by an aromatic substitution, addition, removal or reduction reaction of the electrophile.

The macroporous gel used is prepared primarily by suspension polymerization in the presence of an inert component, which may be a solvent, precipitant, or polymer, which is removed when the polymerization is complete by either dissolution, evaporation, or other means. Suitable monomers have been found to be divinylbenzene and ethylstyrene in proportions of 50-70 to 50-30% by weight. Thus, the process of the invention and its associated absorbents can be advantageously used, for example: to separate a gas from a mixture of air "liquids" "" water "solvents" "" air "" "" "water" aromatic "" " "water" aliphatic "" "water compounds" monomers "" "air" aliphatic "" "air compounds" polar "" "water compounds" "" "" air

The invention is therefore very useful for the purification of gases or liquids or for the separation of certain gases or liquids.

II

7 74884 of mixtures containing them together with one or more other components.

One field of application of the present invention is the absorption of styrene from air, for which no satisfactory solution has previously been found. It is a problem that is currently topical in much of the plastics industry.

Styrene is a relatively non-polar compound that has been shown to have a molecular size that readily adheres to the pores of aromatic macroporous gels. Activated carbon binds somewhat more styrene, but then the already mentioned disadvantage that styrene polymerizes in carbon becomes apparent, which makes it very difficult to regenerate. This disadvantage does not occur with aromatic macroporous gels.

The invention is defined in the following claims and will now be further illustrated by some examples.

Experiments These experiments compare the absorption and desabsorption capacity (regeneration) of differently modified macroporous gels with different substances. Some comparisons have also been made with activated carbon. In order to illustrate as clearly as possible the importance of polarity for the potency of a macroporous gel and to avoid the examples becoming too broad, the examples are limited to a macroporous gel composed of a single base polymer modified by the introduction of various functional groups.

A. Preparation of the base polymer 48 g of divinylbenzene (DVB), 32 g of ethyl vinylbenzene, 1 g of AIBN (reactant) and 180 ml of toluene are mixed together in flask No. 1.

Mix 540 ml of water and 11 g of polyvinylpyrrolidone in flask No 2.

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The contents of flasks 1 and 2 are combined and heated to 70 ° C and the reaction is allowed to proceed with stirring for 6 h.

Yield: About 95% of the monomer mixture is converted to polymer (detected by weighing).

Macro-porous gels prepared as described above with a particle size in the range of 0.09 to 0.5 mm and having a particle size obtained by screening to meet the requirements of the specification and being nearly monodispersed were used in various experiments.

B Sulfonation of a macroporous gel

A large excess of concentrated sulfuric acid was poured into the flask. Then, 40 g of a macroporous gel prepared by the method described above of 60% by weight of divinylbenzene and 40% by weight of ethyl vinylbenzene were slowly added under cooling. The reaction was allowed to proceed for a couple of hours at room temperature.

The polymer was purified by dissolving, first with water, then with methylene chloride.

Yield: About 95% of the total number of dinaromatic rings were imported in this way with a sulfonyl group (elemental analysis).

C. Acylation of a Macroporous Gel 60 g of aluminum chloride, 400 ml of methylene chloride and 48 g of a macroporous gel prepared according to the method described above from 60% by weight of DVB and 40% by weight of ethyl vinylbenzene were mixed in a flask. 29 g of acetyl chloride were then added under cooling. The reaction mixture was heated to 50 ° C and allowed to proceed for a few hours. The material was purified by dissolving first in water and then in methylene chloride.

Yield: About 65% of the total number of aromatic rings 11,74884 were introduced in this way with an acyl group (elemental analysis).

D Alkylation of a macroporous gel

Alkylation occurs in the same manner as acylation, but R-Cl was used instead of R-COCl.

E Nitration of a macroporous gel

A large excess of nitric acid (HNO 2 + 1 ^ SO 2) was poured into the flask. 40 g of a macroporous gel prepared from 60% by weight of DVB and 40% by weight of ethyl vinylbenzene were then added slowly with cooling. The reaction occurs in the blink of an eye.

The polymer was purified by dissolving, first with water, then with methylene chloride.

Yield: Approximately 96% of the total number of aromatic rings were imported in this way with a nitro group (elemental analysis).

F Bromination of a macroporous gel 40 g of a macroporous gel prepared from 60% by weight of DVB and 40% by weight of ethyl vinylbenzene, 300 ml of methylene chloride and catalytic amounts of pyridine were mixed in a flask. Then 20 ml of bromine were added under cooling. After all the bromine had been added, the mixture was warmed to about 30 ° C and the reaction was allowed to proceed for 3 hours. The polymer was filtered and dissolved first with water and then with methylene chloride.

Yield: About 70% of the total amount of aromatic rings was imported in this way (bromine analysis).

G Introduction of amino acid function (macroporous gel) 20 g of brominated macroporous gel from point F were suspended in 100 ml of dimethylformamide together with 15 g of potassium carbonate. 10 g of L-cysteine methyl ether were added and the whole mixture was stirred at 30 ° C for 20 h. The polymer was then filtered off and dissolved in water and then 74884 10 methylene chloride. The reaction had released bromine ions, corresponding to a 60% yield.

H Reduction of the nitro group to the amine in a macroporous gel

First, a macroporous gel prepared from 60 wt% DVB and 40 wt% ethyl vinylbenzene was nitrated as previously described.

45 g of granulated tin were mixed with 100 ml of hydrochloric acid in a flask. 44 g of the macroporous gel described above was slowly added. The mixture was then heated to 100 ° C for a couple of hours.

The material was purified by first dissolving in dilute hydrochloric acid, then with methylene chloride.

Throughput; Approximately 90% of the total number of aromatic rings were introduced in this way with an amino group (elemental analysis and weighing).

I. Introduction of Nitro and Bromine Groups into a Macroporous Gel First, a macroporous gel prepared from 60% by weight of DVB and 40% by weight of ethyl vinylbenzene was brominated as described above.

40 g of the above brominated product were then nitrated in a large excess of nitric acid (HNO 2 + H 2 SO 4).

The polymer was purified by dissolving first in water and then in methylene chloride.

Yield: In the first stage, about 70% of the total number of aromatic rings was introduced into the bromine group. In the subsequent nitration, a nitro group was introduced into about 95% of the total amount of aromatic rings.

J Introduction of nitro and nitrile groups into macroporous gels li 11 748 84

First, a nitro, bromine polymer was prepared as described above. 20 g of this polymer, 15 g of CuCN and 100 ml of dimethylformamide were then mixed in a flask. The reaction is allowed to proceed for 5 h at 80 ° C.

Yield: About 60% of the total amount of aromatic rings is introduced in this way with a nitrile group (elemental analysis).

Tables I and II show the measured values obtained in comparative experiments in which different test gases were absorbed in both activated carbon and an unmodified and modified macroporous gel prepared from divinylbenzene and ethyl vinylbenzene (60:40). Table II shows the results for several successive absorption-desab sorption cycles.

12 74884

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Claims (9)

14 74 8 84 A process for separating gaseous or liquid components from a gas or liquid mixture, characterized in that the gaseous or liquid component to be separated is absorbed into a particulate macroporous gel formed of a crosslinked aromatic homo- or copolymer capable of selectively absorbing the component in question. the gas or liquid mixture is brought into contact, and from which the gas or liquid can later be released while the gel is regenerated. Process according to Claim 1, characterized in that the intrinsic polarity of the macroporous gel is modified by introducing one or more functional groups through the aromatic substitution of the electrophile before it is brought into contact with the gas or liquid mixture in question. Process according to Claim 1 or 2, characterized in that a macroporous gel is prepared which is prepared in the presence of an inert component such as a solvent, a dopant or a polymer. Process according to one of Claims 1 to 3, characterized in that a macroporous gel prepared from divinylbenzene and ethylvinylbenzene in a weight ratio of 60:40 is used. Process according to Claim 2 or 3, characterized in that the polarity obtained by the macroporous gel after introduction of functional groups in the electrophilic aromatic substitution is further modified by means of a conventional substitution, addition or removal reaction. Il 1S 74884 Method according to one of Claims 1 to 5, characterized in that the component absorbed in the macroporous gel, after the contact between the macroporous gel and the gas or liquid mixture has been terminated, is released from the macroporous gel by heating and removed with an inert carrier which is passed through a macroporous gel, which also regenerates the gel. A method according to claim 6, characterized in that the heating of the macroporous gel and the removal of the previously absorbed component thus released take place with the aid of the same medium. Process according to one of Claims 1 to 7, characterized in that a macroporous gel consisting of a crosslinked aromatic homopolymer or copolymer having a particle size in the range from 0.09 to 0.5 mm and which is essentially monodispersed is used as the absorbent, as defined herein. means that the polymer consists of at least 80% by weight of particles which do not deviate from the mean by more than 0.2 mm. Absorbent for use in a method according to any one of claims 1 to 8, characterized in that it is a macroporous gel consisting of a crosslinked homo- or copolymer.