JPS61204140A - Separation of hydrocarbon and water content-free separating membrane - Google Patents

Abstract

(57) [Summary] This bulletin contains application data before electronic filing, so abstract data is not recorded.

Description

BACKGROUND OF THE INVENTION The present invention relates to a water-free separation membrane for separating unsaturated hydrocarbons from saturated hydrocarbons. The present invention also utilizes a water-free membrane constructed from a separation barrier material having metal ions dissolved in a polyhydric alcohol in the pores or on the surface of a porous support to transport hydrocarbons in fluid form. It also relates to a method for separating aliphatic unsaturated hydrocarbons from a mixture. The present invention can be particularly advantageously used to separate ethylene from gaseous mixtures containing ethylene, other hydrocarbons (eg, ethane, methane), and hydrogen in the absence of water.

The separation of various aliphatic unsaturated hydrocarbons from mixtures of hydrocarbons is an operation of considerable industrial interest. Aliphatic unsaturated hydrocarbons are reactive substances used for various purposes in the chemical and hydrocarbon industries, and are generally used as intermediates in chemical synthesis.

A number of unsaturated hydrocarbons are used as monomers in the manufacture of polymers, and olefins such as ethylene, propylene, butadiene and isoprene are well known in the art. Aliphatic unsaturated hydrocarbons are most often commercially available in the form of mixtures with other chemicals. Such unsaturated hydrocarbon-containing mixture fluids are generally by-products of chemical synthesis or separation operations. If such a hydrocarbon stream is normally liquid or readily liquefiable, its separation into its individual hydrocarbon components requires that the boiling points of these components differ considerably from each other. can be economically separated into its components using conventional distillation techniques. However, when the hydrocarbon mixture contains components with boiling points close to each other, distillation is not an attractive separation method. Mixtures of hydrocarbons having the same number of carbon atoms or differing by only one are defined as the above-mentioned hydrocarbon mixtures (i.e., hydrocarbon mixtures containing multiple components with boiling points close to each other). This is often the case. In such cases, alternative separation methods must be used, which are often expensive and involve operations such as solvent extraction, extractive distillation, and freeze-coagulation. .

Desired constituents from the mixture of aliphatic unsaturated hydrocarbons or mixtures of said hydrocarbons and other hydrocarbons (having similar boiling points) when the mixture is substantially gaseous under normal atmospheric pressure. Separation of is generally quite cumbersome. Freezing methods can be used in this case, but are often not commercially viable due to high costs. To circumvent this difficulty, methods have been developed to separate unsaturated hydrocarbons from mixtures of saturated and unsaturated hydrocarbons using semipermeable membranes.

A separation method that uses a membrane is called the "P-desorption method," and it is a good separation method.In the desorption method, one substance in the raw material mixture is passed through the membrane, and for this purpose, the A membrane is used that contains a component that has properties that interact specifically and reversibly with the component.

The best-studied method for separating aliphatic unsaturated hydrocarbons to date is the separation of ethylene from a mixture of ethylene and saturated hydrocarbons. It is already known that unsaturated hydrocarbons have the property of interacting with silver ions. Knowledge of the kinetics and equilibrium of this reaction indicates that research results in this area can be used to improve the process. The use of metal ions, such as silver ions, has been proposed as a convenient method for the separation of unsaturated hydrocarbons.

However, all conventional methods require the membrane to be impregnated with moisture to prevent it from drying out, and the raw material gas must also be saturated with moisture, that is, the use of water is an essential requirement. . Thus, in order to carry out the aforementioned separation processes, such as the separation of ethylene from ethane, it was considered essential to saturate the system with water. It has been postulated that the presence of water is necessary because water acts as a solvent for the silver ions and/or water forms the necessary electronic environment for the silver ions. Since water is highly volatile, the requirement to use water has been a major hindrance to the usefulness of the separation method.

When the membrane dries out due to some accident, it loses its separation properties (separation ability) and this change is irreversible, so the membrane can no longer be used.

A method has been developed for separating aliphatic unsaturated hydrocarbons from mixtures of them and other hydrocarbons by combining metal complexation techniques with membrane permeation techniques using liquid barriers. In this method, a liquid barrier is placed adjacent to a film-like semipermeable membrane that allows each component in a raw mixture of hydrocarbons to pass therethrough in a relatively non-selective manner. It uses a device that exists as a liquid phase. Additionally, aliphatic unsaturated hydrocarbons can be separated from other hydrocarbons using a technique that combines metal complex formation techniques that are selective for aliphatic unsaturated hydrocarbons with liquid barrier permeation techniques. Methods for separating each component from a mixture of are known.

The liquid barriers used in these known methods are aqueous solutions containing dissolved metal ions that can form complexes with the components to be separated. The selectivity and separation power of devices using these metal ion-containing aqueous barriers can decrease due to loss of water from the barrier-membrane system over extended use of the device. Like this,
Since the selectivity and separation ability of this metal ion-containing aqueous solution-membrane system decreases with drying, it is generally
It is necessary to add water throughout.

SUMMARY OF THE INVENTION It is an object of the present invention to provide a method for separating aliphatically unsaturated hydrocarbons from a hydrocarbon mixture and a water-free membrane for this separation.

Another object of the present invention is to provide a permeable membrane that is not moisture dependent, has fewer failures, and is easy to operate.

To achieve this objective, in the present invention, metal ions are dissolved in polyhydric alcohol at a high concentration, and this solution is introduced into the pores of a porous support. The resulting separation membrane is suitable for the selective permeation of unsaturated hydrocarbons such as ethylene;
It passes through a membrane made of a barrier material made by dissolving metal ions in polyhydric alcohol. The term "polyhydric alcohol" used to describe the present invention means a compound having two or more hydroxyl groups, and thus includes both monomeric and polymeric compounds. do.

The barrier material may constitute a membrane on the porous support, or it may constitute a membrane effective in the pores of the porous support1, thus forming a porous support. The polymer or other material used is a substantially neutral material that does not affect the selectivity or permeability of the aliphatic unsaturated hydrocarbon permeate.

The present invention provides a convenient means for separating aliphatic unsaturated hydrocarbons from saturated hydrocarbons without the need for adding water to the separation membrane or feed stream. A barrier material for separation operations is created by dissolving metal ions in a polyhydric alcohol or in a polymer plasticized by the polyhydric alcohol, and this is applied to the pores of the porous support. Whether contained within or on the surface of the support, the barrier material may constitute a liquid or substantially solid barrier membrane. If the porous support is hydrophobic so that the barrier material cannot penetrate into its pores, a barrier film can be formed on the surface of the porous support by surface tension phenomena.

When a hydrophilic substance is present in the structure of the porous support, the hydrophilic barrier material can penetrate into the pores of the porous support described in F, thereby allowing metal ions and polyhydric alcohols to A barrier membrane consisting of a polyurethane material can be formed in the pores of the porous support.

The novel features considered characteristic of the invention are set forth in the claims. However, the objects, structure, and effects of the present invention, as well as the method of carrying out the same, will be better understood from the following description of some specific examples of the present invention.

Description of Preferred Embodiments Both liquid and solid metal ion-containing membranes can be used in a water-free state. That is, it may be in the form of a solution containing metal ions in a polyhydric alcohol, or it may contain metal ions in a polymer-polyhydric alcohol mixture. This membrane is present in the pores or on the surface of the porous support. This metal ion-containing polyhydric alcohol membrane can be used as a means for separating said unsaturated hydrocarbons from a mixture of aliphatic unsaturated hydrocarbons and saturated hydrocarbons, i.e. this metal ion-containing barrier membrane It exhibits chemical selectivity for saturated hydrocarbons and has the property of selectively permeating them.

Metal salts, such as silver nitrate or silver trifluoromethanesulfonate, can be dissolved in high concentrations in polyhydric alcohols such as glycerol. This solution can be present in the pores or on the surface of the porous support as a thin film or as a pore barrier III. If the porous support is hydrophobic, the polyhydric alcohol-metal ion barrier material cannot penetrate into the pores due to surface tension phenomena. When the polyhydric alcohol is a polymer, a thin barrier film can generally be formed on the surface of the hydrophobic porous support. Because of this surface tension relationship, the barrier membrane or film covering the support is sufficiently thin to have a sufficiently high permeation rate and desired selectivity.

The water-free separation barrier material in solution can be placed in a porous support, thereby forming a separation barrier consisting of the barrier material remaining in the support as a liquid or semi-solid or solid. , when fed with a dry ethylene-ethane mixture, a selectivity of about 50-300 and about ethylene can be separated. Since this polyhydric alcohol has low volatility, it does not escape from the membrane, and the operability is generally stable even during long-term operation.

When a hydrophobic porous support is selected and used as the porous support for barrier a consisting of metal ions and hydrophilic alcohol, the barrier formed to cover this support is hydrophilic, It can therefore be formed on or adjacent to the porous surface of said hydrophobic support, ie a hydrophilic surface can be formed in contact with the hydrophobic support. A barrier membrane in the form of a hydrophilic coating can be formed on the surface of a hydrophobic porous support, for example by coating the surface with a hydrophilic barrier film. The separation of unsaturated hydrocarbons from a gaseous feedstock hydrocarbon stream containing a mixture of aliphatic unsaturated hydrocarbons and saturated hydrocarbons is accomplished primarily by using a polyhydric alcohol-based barrier membrane containing the complexing metal ions. This can be achieved through action.

The hydrophobic support for the membrane used according to the invention is a substantially solid and water-insoluble semipermeable support.
It is made of easy material. This support does not have good selectivity, so it does not serve as a pathway for aliphatic unsaturated hydrocarbons, nor is it permeable to said unsaturated hydrocarbons, in other words: It does not have the effect of separating the components in the raw material mixture as desired. However, by contacting this support with a sufficient amount of liquid or solid barrier material to create a thin film separation membrane, the amount of gas passing through the barrier by physical mechanisms is reduced or Therefore, each component in the raw material stream passes through the polyhydric alcohol-metal ion complex barrier membrane through the separation zone of this barrier membrane, mainly as a part of the components of the eardrum, and is immediately separated from the eardrum. Otherwise, it cannot penetrate the eardrum.

Preferably, the polyhydric alcohol used to make the thin film is a polymer. For example, in the absence of complexing metal ions in the polyhydric alcohol medium, no or little separation of hydrocarbons by a hydrophobic porous support can take place. However, according to the present invention, the presence of complex-forming metal ions in the polyhydric alcohol barrier membrane provides very good selectivity to aliphatic unsaturated hydrocarbons.

In operation of the present invention, the polyhydric alcohol-metal ion barrier membrane described above is useful for feedstocks in the form of liquids or mixed fluids. The polymeric polyhydric alcohol thin membrane described above may contain other polymers that can increase the membrane strength without interfering with the separation function of the membrane.

Since this barrier membrane is fairly thin, unsaturated hydrocarbons permeate through this membrane at a fairly high permeation rate. This permeation rate will vary depending on the thickness of the membrane. On the other hand, selectivity can be partially controlled by metal ion concentration.

The barrier membrane contains sufficient alcohol-soluble metal ions to form suitable complexes with at least one aliphatic unsaturated hydrocarbon component in the feed fluid. The metal ions readily form complexes when contacted with the feed fluid, and the complexes dissociate again into metal ions and aliphatic unsaturated hydrocarbon components under the conditions present on the discharge side of the barrier membrane. The aliphatic unsaturated hydrocarbons thus released exit the discharge side of the barrier membrane and flow freely through the porous support. The aliphatic unsaturated hydrocarbons can be removed from the vicinity of the uncoated surface of the porous support by a sweeping fluid or by using vacuum and/or other means. Thus, the unsaturated hydrocarbons form metal complexes during flow through the metal ion-containing polyhydric alcohol-based barrier membrane, and the complexes decompose, resulting in at least one of the substances passing through the barrier membrane. The concentration of one aliphatic unsaturated hydrocarbon will be higher than the concentration of the unsaturated hydrocarbon in the feed stream.

The aliphatic unsaturated hydrocarbons to be selectively separated react to a sufficient extent with the metal complexing ions, while at least one component in the feed stream does not react or only reacts to a very small extent with the complexing metal ions. It is necessary to use a feed stream containing m aliphatic unsaturated hydrocarbons sufficient to meet the requirements of compatibility. This amount may be small, ie feed streams containing small amounts of said unsaturated hydrocarbons can be used, as long as the above conditions are met.

The aliphatically unsaturated hydrocarbons of most interest from the separation characteristics of the process of the invention and the properties of the membranes of the invention are those having about 2-9, preferably about 2-4, carbon atoms per molecule. Of particular interest is the separation of ethylene or propylene from mixtures thereof with one or more normally gaseous substances such as ethane, methane, propane, hydrogen, etc. Feedstock mixtures of this type often contain about 1-50% by weight ethylene, about 0-50% by weight M% ethane, and about 0-50% by weight methane.

As used herein, the term "metal ionpa" refers to a metal that can form metal ions in water-free polyhydric alcohol solutions and reversibly form complexes with aliphatic unsaturated hydrocarbons. Metals can be used that are capable of forming metal complexes with the desired properties in the form of metal ions and that have the property of separating aliphatic unsaturated hydrocarbons from the feed mixture through complex formation.

Examples of such metals include transition metals having a base number greater than 20 in the Elements Table of Elements.

Main examples of this metal include chromium, copper (especially cuprous ions)
, metals belonging to the first transition metal group with atomic numbers 21-29, such as iron group metals (eg nickel and iron). Another useful complex-forming metal is atomic number 39-
47, and 57-79 metals of the second and third transition metal groups, and mercury (particularly the mercurous ion). For example, noble metals such as gold and silver and platinum group metals such as platinum, baladyllum, rhodium, ruthenium, osnium are suitable. Examples of useful base metals belonging to the second iB and third transition metal groups include molybdenum, tungsten, rhenium, and the like.

Various combinations of these complexing metals can also be used in accordance with the present invention in the presence or absence of non-metal cations and non-complexing metals.

Permeable membranes often exhibit a saturation phenomenon, that is, their selectivity deteriorates rapidly with increasing pressure. However, solid barrier membranes made as composites using porous supports according to the present invention can be operated under pressure differentials of 689 Pa or more and are a good choice for aliphatic unsaturated hydrocarbons. Show your gender.

Various membranes in the form of separation barrier membranes are prepared according to the present invention using various silver ions in combination with polyhydric alcohols or polyhydric alcohol mixtures and are used in separation operations of ethylene from ethane. I did it. These membranes are
It existed on the surface of porous polypropylene or in the pores of porous nylon sheet. 7 according to the present invention
The membranes described above were used in the separation of ethylene from ethane and the permeability and resolution were measured, details of which are described in Examples 1-6 below.

The unit of transmittance is cm (S T P ) / ctr
r 2 (membrane)/min/1.333 Pa (thickness 1 c
pressure difference across the membrane of tn), so this is “c
m3Xcm (S T P )/ctn -seC-
caHg''. Unless otherwise specified, all permeability values are measured at normal pressure (ie, at a temperature of about 24° C. and a pressure of 1 atmosphere).

Another convenient value for expressing the gas permeability of a membrane is the separation factor.

The separation coefficient when a pair of gases "a" and "b" are separated by a membrane is determined by the desorption degree (Pa) of gas "aIT" in the gas mixture and the desorption degree (Pa) of gas "b" in the gas mixture. (Pb).

Example 1 A 1M solution was made by placing silver nitrate in glycerol and gently heating with stirring. A 0.1 μm nylon steel material was impregnated into the resulting transparent solution. After 48 hours of equilibration, the filter media was removed, excess solution wiped from its surface, and the test was conducted. That is, dry ethylene/ethane (abundance ratio 1:1) raw material is
The separation properties of the membrane (the above-mentioned filter medium) were measured under a pressure of 33.3 Pa. The characteristic values after 24 hours of use were as follows.

α(CH/C21-16)-50,2 P(C2)-14)=3.6xlO Example 2 A liquid film was prepared according to the method of Example 1, except that silver trifluoromethanesulfonate was used instead of silver nitrate. manufactured and tested.

α(C2H4/C2H6)-22,3 P (C2H4)=2.8x10 Example 3 The procedure of Example 1 was followed, except that the solution of AgNO3 in glycerol was a 3M solution. The measured values of separation characteristics were as follows.

α[CH/C2H6] = 69 P (C2H4') = 11, 5x 10 When this membrane material (also called membrane cell) was heated to 65°C, the permeability increased substantially and Selectivity was maintained at a good value.

α[C2□H4/C2H6] = 24 P (C2H4) = 46xl 0 Example 4 The procedure of Example 1, except that a solution of AgNO3 in 1,4-butanediol at a 1M concentration was used. repeated. The separation characteristics were as follows.

α[02H4/C2H6]=5.7 P (C2H4)-46,8xl O A coating liquid was prepared according to the manufacturing method of Nyu-Shinji. 6% triglycerol in a 3% (W/V) aqueous solution of polyvinyl alcohol,
hydrogen peroxide (the amount necessary to make a 1.5% solution was used), and 6) silver monate (the amount necessary to make a 4M solution in non-volatile components (PVA and triglycerol)). ] was added.

The resulting solution was filtered and coated onto a porous polypropylene sheet (trade name "Celgard-2402") to form a thin layer. After drying in vacuum at room temperature,
Tests were conducted using a dry ethylene/ethane mixture (1:1 mixture). The measured selectivity for ethylene in the ethylene/ethane mixture was 182. The ethylene permeability was 3.1×10. This exam is 4
The experiment was carried out for 8 hours, during which time no change in separation properties occurred.

Example 6 Example 5 was carried out, except that 1.6% glycerol was used instead of triglycerol and a 5% aqueous solution of PVA was used. The following results were obtained.

In all of Examples 1-6 above, the membrane was moisture-free and the ethylene/ethane feedstock was also moisture-free.

Example 7 below specifically illustrates the need to omit the presence of a polyhydric alcohol in the water-free membrane for hydrocarbon separation of the present invention.

Example 7 A composite type membrane was prepared from a 10% aqueous solution of polyvinyl alcohol containing 10 moles of silver nitrate (based on the weight of the polymer) as follows: this solution was coated on the surface of polypropylene to form a thin layer. A membrane was prepared.

Tests were conducted using a dry ethylene/ethane feed but no selectivity values were obtained. The membrane was observed to crack when removed from the test cell (foam). Only when glycerol or triglycerol is added to this polyvinyl alcohol barrier material,
It was confirmed that the separation characteristics were good as described in the above-mentioned Examples.

Procedural amendment (own ship) March 6, 1986 Dear Commissioner of the Patent Office, rare.

1. Indication of the case 1985 Patent Application No. 299691 2° Invention (D name: Method for separating carbon-hydrogen and water-free separation membrane 3. Person making amendments Relationship with the case Patent applicant 4, Agent 5.Date of amendment order Showa year month day

Claims (12)

[Claims] (1) A separation barrier material consisting of a metal ion dissolved in a polyhydric alcohol or a polyhydric alcohol mixture is present on the surface of a porous support or in the pores of the porous support. A water-free membrane suitable for the separation of aliphatic unsaturated hydrocarbons from saturated hydrocarbons. (2) The water-free membrane according to claim 1, wherein the metal ions are selected from noble metals in the Periodic Table of the Elements. (3) The water-free membrane according to claim 1, wherein the metal ions are silver ions. (4) Aliphatic unsaturated hydrocarbon and saturated hydrocarbon are 1
A water-free membrane according to claim 1, having about 1-9 carbon atoms per molecule. (5) Aliphatic unsaturated hydrocarbon and saturated hydrocarbon are 1
5. A water-free membrane according to claim 4, having about 1-4 carbon atoms per molecule. (6) A water-free membrane according to claim 1, suitable for separating ethylene from ethane. (7) The porous support is hydrophobic, and the separation barrier material constitutes a membrane on the surface of the porous support, as set forth in claim 1. water-free membrane. (8) Claim 1, wherein the porous support is hydrophilic, the separation barrier material is a liquid, and a membrane is formed in the pores of the porous support. Moisture-free membranes as described in Section. (9) In order to separate aliphatic unsaturated hydrocarbons from saturated hydrocarbons, these hydrocarbons are brought into contact with a moisture-free membrane containing a separation barrier material, and this barrier material is
A metal ion dissolved in a polyhydric alcohol or a mixture of polyhydric alcohols is present on the surface of a porous support or in the pores of the porous support, and is used to remove the aliphatic unsaturation. A separation method characterized in that hydrocarbons are selectively permeated through the water-free membrane. (10) The method according to claim 9, wherein the aliphatic unsaturated hydrocarbon and the saturated hydrocarbon do not contain water. (11) Aliphatic unsaturated hydrocarbon and saturated hydrocarbon are 1
11. A method according to claim 10, characterized in that it has about 1-9 carbon atoms per molecule. (12) The method according to claim 9, characterized in that ethylene is separated from ethane.