1. The compound solvent for separating olefin/alkane is characterized by consisting of a low-transition-temperature mixture and an organic solvent or a metal salt.

2. The low transition temperature mixture of claim 1, consisting of a built solvent, consisting of a hydrogen bond acceptor and a hydrogen bond donor as follows: ethanolamine and sulfolane in a molar ratio of 1: 1-1: 5, tetrabutylammonium halide (tetrabutylammonium bromide, tetrabutylammonium chloride and tetrabutylammonium iodide) and sulfolane in a molar ratio of 1: 4-1: 8, or trimethylamine hydrochloride and ethylene glycol in a molar ratio of 1: 4-1: 8.

3. The organic solvent constituting the built solvent according to claim 1 mainly comprises: n-methylpyrrolidone, dimethylsulfoxide.

4. The metal salt constituting the built solvent according to claim 1 mainly comprises: silver acetate, silver nitrate, silver tetrafluoroborate, copper nitrate and copper acetate.

5. The preparation method of the compound solvent for separating alkene/alkane according to claim 1, which comprises the following steps: and mixing the hydrogen bond donor and the hydrogen bond acceptor according to a certain molar ratio, heating to 80-120 ℃, stirring, stopping heating and stirring until the solution is clear and transparent, and naturally cooling the solution to room temperature to obtain the low-transition-temperature mixture.

Keeping the temperature of the low-transition-temperature mixture at 60-80 ℃, adding a certain mass of organic solvent or metal salt into the mixture, stirring until the compound solvent is uniformly mixed, and naturally cooling to room temperature to obtain the compound solvent for separating alkene/alkane.

6. The compound solvent for separating alkene/alkane according to claim 1, wherein the mass ratio of the low-transition-temperature mixture to the organic solvent is 1: 5-5: 1.

7. The built solvent for separating alkene/alkane according to claim 1, wherein the mass ratio of the low-transition-temperature mixture to the metal salt is 4: 1-20: 1.

8. The compound solvent for separating alkene/alkane according to claim 1, wherein the mass ratio of the compound solvent to raw materials is 1: 1-15: 1.

9. The method for separating olefin and alkane by using the compound solvent as claimed in claim 1, wherein the separation of olefin/alkane and the recycling of the compound solvent are realized by using an extraction separation process combining an extraction tower and a reduced pressure distillation tower, wherein the operating temperature of the extraction tower is 20-60 ℃, the temperature of the reduced pressure distillation tower is 20-100 ℃, and the pressure is 0.05-0.1 MPa.

Background

Unsaturated hydrocarbon (C5-C8) is used as an important organic petrochemical raw material and can be used for producing detergents, plasticizer alcohol, oil additives, polymers, synthetic rubber and the like. The current processes for producing olefins mainly focus on petroleum cracking, low carbon olefin oligomerization, alkane dehydrogenation and the Ficher-Tropsh route, and the products are often olefin/alkane mixtures regardless of the production method. Since the molecular structure and properties of olefin and straight-chain alkane with the same carbon number are very similar, the separation of olefin/alkane is always a technical difficulty in petrochemical industry.

The typical process for olefin/alkane separation is to use high boiling polar compounds as solvent and separate them by extractive distillation, which requires huge energy and capital investment. In addition, separation methods such as adsorption separation and membrane separation have been proposed.

The patent CN103007885B discloses an adsorbent for olefin/alkane separation and a preparation method and application thereof, the adsorbent is prepared by taking porous carbon with high specific surface area and ordered pore channels as an adsorbent carrier and cuprous chloride as an active component, and has the advantages of simple preparation, good adsorption effect and capability of maintaining good adsorption effect after adsorption and regeneration. However, the adsorption method has the problems of poor selectivity, low yield and the like, and metal ions are easy to generate irreversible reaction with carbon oxides and sulfur oxides, so that desorption and recovery of the adsorbent are influenced.

Patent CN106431813B discloses a method for separating olefin/alkane mixture by using an immobilized Ag [ Tf2N ] transfer membrane, which details the preparation of the immobilized Ag [ Tf2N ] transfer membrane and its flow and method for separating olefin/alkane mixture. However, the preparation method of the membrane is complex and high in cost, and the application of the membrane in olefin/alkane separation is limited.

Compared with the separation of olefin/alkane by an adsorption method and a membrane separation method, the extraction method has simple operation equipment and operation method, can be completed at normal temperature, can save cost and is easy for large-scale production. Research on the use of extraction methods for olefin/alkane separation dates back to the sixties of the last century and researchers have attempted to mix different solvents to improve the extraction capacity of the solvents in order to improve the selectivity of solvent separation.

In the research of separating olefin/alkane by an extraction method, a common organic solvent is easy to volatilize, secondary pollution is easy to cause, the difficulty of recycling the solvent is increased, the separation selectivity is low, and the dosage of the organic solvent is increased; the low-transition temperature mixture is widely applied in the separation process due to the advantages of easily available raw materials, simple preparation, no toxicity, good biodegradability and the like, and in addition, the low-transition temperature mixture has structural designability, can improve the separation selectivity of olefin/alkane through molecular design, but has high viscosity compared with an organic solvent. Therefore, the alkene/alkane is separated by the compound solvent consisting of the organic solvent and the mixture with the low transition temperature, so that the separation selectivity can be improved, the use amount of the organic solvent is reduced, the pollution is reduced, the viscosity of the mixture with the low transition temperature is reduced, and the mass transfer efficiency is improved.

In addition, the complexation theory is applied to the separation process of the olefin/alkane to improve the separation selectivity of the olefin/alkane. The metal salt can form a complex with olefin, thereby improving the separation selectivity. Based on the advantages of easy acquisition of raw materials of the low-transition-temperature mixture, simple preparation, no toxicity, good biodegradability, difficult volatilization and the like, the compound solvent formed by the low-transition-temperature mixture and the metal salt is used for separating the olefin/alkane.

Disclosure of Invention

In view of the above, the invention aims to provide a compound solvent for separating olefin/alkane, and a preparation method and application thereof.

The compound solvent composed of the low-transition-temperature mixture and the organic solvent can be designed to overcome the problems of secondary pollution, low separation selectivity and the like caused by the traditional organic solvent by using the extremely low volatility and function of the low-transition-temperature mixture, and simultaneously solves the problems of high viscosity and influence on mass transfer efficiency of the low-transition-temperature mixture.

The compound solvent composed of the low-transition-temperature mixture and the metal salt overcomes the problem that the traditional organic solvent pollutes olefin by the advantage that the low-transition-temperature mixture is not easy to volatilize, improves the selectivity of the olefin by combining the complexation of the metal salt and the olefin, and greatly improves the separation performance of the solvent by the compound solvent composed of the low-transition-temperature mixture and the metal salt.

The technical scheme of the invention is as follows: a compound solvent for extracting and separating olefin/alkane is characterized in that: the compound solvent for separating alkene/alkane consists of a low-transition-temperature mixture and an organic solvent or a metal salt.

The low transition temperature mixture is composed of a hydrogen bond donor and a hydrogen bond acceptor, and is liquid at normal temperature and normal pressure. The low transition temperature mixture has the advantages of higher thermal stability, difficult volatility and no toxicity, and is a green solvent.

The invention aims to provide a solvent for separating alkene/alkane by an extraction method, a compound solvent obtained by compounding a low-transition-temperature mixture and an organic solvent or a metal salt has high separation selectivity, and the separation selectivity of alkene/alkane can be flexibly adjusted by adjusting the compounding ratio of the low-transition-temperature mixture and the organic solvent or the metal salt.

In order to achieve the purpose, the technical scheme of the invention is realized as follows:

the method for separating olefin/alkane by using the compound solvent obtained by the mixture with low transition temperature and the organic solvent or the metal salt comprises the following steps:

(1) mixing ethanolamine and sulfolane in a molar ratio of 1: 1-1: 5, or tetrabutylammonium halide (tetrabutylammonium bromide, tetrabutylammonium chloride and tetrabutylammonium iodide) and sulfolane in a molar ratio of 1: 4-1: 8, or trimethylamine hydrochloride and ethylene glycol in a molar ratio of 1: 4-1: 8, heating to 80-120 ℃, stirring until the solution is clear and transparent, stopping heating and stirring, and naturally cooling the solution to room temperature to obtain the low-transition-temperature mixture.

(2) And (2) heating the low-transition-temperature mixture prepared in the step (1) to keep the temperature at 60-80 ℃, adding a certain mass of organic solvent into the low-transition-temperature mixture according to the mass ratio of the low-transition-temperature mixture to the organic solvent of 1: 5-5: 1, stirring until the compound solvent is uniformly mixed, and naturally cooling to room temperature to obtain the compound solvent for separating alkene/alkane.

(3) And (2) heating the low-transition-temperature mixture prepared in the step (1) to keep the temperature at 60-80 ℃, adding a certain mass of metal salt into the low-transition-temperature mixture according to the mass ratio of the low-transition-temperature mixture to the metal salt of 4: 1-20: 1, stirring until the compound solvent is uniformly mixed, and naturally cooling to room temperature to obtain the compound solvent for separating alkene/alkane.

(4) And (4) taking the compound solvent prepared in the steps (3) and (4) as an extracting agent for olefin/alkane separation. The method is characterized in that an extraction separation process combining an extraction tower and a reduced pressure distillation tower is adopted to realize the separation of olefin/alkane and the recycling of a compound solvent, the operating temperature of the extraction tower is 20-60 ℃, the temperature of the reduced pressure distillation tower is 20-100 ℃, and the pressure is 0.05-0.1 MPa.

Further, the low transition temperature mixture in the step (1) has a melting point or a glass transition temperature of 25 ℃ or less

Further, in the step (2), the organic solvent is any one of N-methylpyrrolidone and dimethyl sulfoxide.

Further, in the step (3), the metal salt is any one of silver acetate, silver nitrate, silver tetrafluoroborate, copper nitrate and copper acetate.

Further, the olefins/alkanes in the step (4) are C5-C8 olefins and C5-C8 alkanes, including but not limited to 1-pentene/n-pentane, 1-hexene/n-hexane, 1-heptene/n-heptane, 1-octene/n-octane.

Compared with the prior art, the invention has the following advantages:

(1) the low-transition-temperature mixture has the advantages of cheap and easily-obtained raw materials, simple preparation process, easy large-scale production and the like.

(2) The low transition temperature mixture has high thermal stability and difficult volatility, and is beneficial to environmental protection.

(3) The addition of the organic solvent can reduce the viscosity of the mixture with low transition temperature, is beneficial to the mass transfer process and improves the separation performance.

(4) The compound solvent formed by the low-transition-temperature mixture and the metal salt can improve the stability of the traditional metal salt solution and solve the problem that the traditional metal salt solution is easy to reduce.

Drawings

FIG. 1 is a flow chart of the application process of the built solvent of the invention.

Wherein, the reference numbers:

1 extraction column

2 reduced pressure distillation column

3 Mixer

S1 alkene/alkane mixture

S2 heavy phase

S3 light phase

S4 higher purity olefin

S5 recovered compound solvent

S6 fresh compound solvent

S7 compound solvent

Detailed Description

The following described embodiments are exemplary and are intended to be illustrative of the invention and are not to be construed as limiting the invention.

Example one

A compound solvent for separating olefin/alkane by extraction method is a mixture with low transformation temperature, N-methyl pyrrolidone (5: 1). The preparation method comprises the following steps: weighing corresponding mass of hydrogen bond donor sulfolane and hydrogen bond acceptor ethanolamine according to the molar ratio of the hydrogen bond donor to the hydrogen bond acceptor being 1:1, heating the container at the heating temperature of 80 ℃, starting a stirring device while heating, stirring the liquid mixture, stopping heating and stirring after clear transparent liquid is formed in the container, and naturally cooling the liquid mixture to the room temperature to obtain the low-transition-temperature mixture. Keeping the temperature of the mixture with the low transition temperature constant at 60 ℃, adding 0.2 times of N-methyl pyrrolidone by mass into the mixture, stirring until the compound solvent is uniformly mixed, and naturally cooling to room temperature to obtain the compound solvent for separating alkene/alkane.

FIG. 1 is a process flow diagram of the compound solvent extraction separation of olefin/alkane, the mass ratio of the compound solvent to the olefin/alkane mixture is 1:1, an olefin/alkane mixture material flow S1 enters an extraction tower from the bottom of the tower, a compound solvent S7 enters from the top of the tower, the compound solvent S7 entering from the top of the tower exchanges substances with the olefin/alkane mixture S1 in the extraction tower, the extraction temperature is 20 ℃, a light phase S3 is discharged from the top of the extraction tower, a heavy phase S2 is discharged from the bottom of the extraction tower, solvent recovery is carried out in a reduced pressure distillation tower 2, the recovered compound solvent S5 flows out from the bottom of the reduced pressure distillation tower 2 and is mixed with a fresh compound solvent S6 to obtain a material flow S7 which enters the extraction tower 1 together, and the top of the reduced pressure distillation tower obtains a high-purity olefin material flow S4. The main parameters are shown in the following table:

example two

A compound solvent for separating olefin/alkane by extraction method is a mixture with low transformation temperature and dimethyl sulfoxide (1: 1). The preparation method comprises the following steps: weighing hydrogen bond acceptor tetrabutylammonium bromide and hydrogen bond donor sulfolane in a container according to the molar ratio of the hydrogen bond acceptor to the hydrogen bond donor of 1:4, heating the container at 100 ℃, starting a stirring device while heating, stirring the liquid mixture, stopping heating and stirring after a clear transparent liquid is formed in the container, and naturally cooling to room temperature to obtain the low-transition-temperature mixture. Keeping the temperature of the mixture with the low transition temperature constant at 70 ℃, adding dimethyl sulfoxide with the same mass into the mixture, stirring the mixture until the compound solvent is uniformly mixed, and naturally cooling the mixture to room temperature to obtain the compound solvent for separating the olefin/alkane.

The mass ratio of the compound solvent to the olefin/alkane mixture is 3:1, an olefin/alkane mixture material flow S1 enters an extraction tower from the bottom of the tower, the compound solvent S7 enters from the top of the tower, the compound solvent S7 entering from the top of the tower exchanges substances with the olefin/alkane mixture S1 in the extraction tower, the extraction temperature is 40 ℃, a light phase S3 is discharged from the top of the extraction tower, a heavy phase S2 is discharged from the bottom of the extraction tower and subjected to solvent recovery through a reduced pressure distillation tower 2, the recovered compound solvent S5 flows out from the bottom of the reduced pressure distillation tower 2 and is mixed with a fresh compound solvent S6 to obtain a material flow S7 which enters the extraction tower 1 together, and the top of the reduced pressure distillation tower obtains a high-purity olefin material flow S4. The main parameters are shown in the following table:

EXAMPLE III

A compound solvent for separating olefin/alkane by extraction method is a mixture with low transformation temperature and dimethyl sulfoxide (1: 5). The preparation method comprises the following steps: weighing hydrogen bond acceptor trimethylamine hydrochloride and hydrogen bond donor ethylene glycol in corresponding mass according to the molar ratio of the hydrogen bond acceptor to the hydrogen bond donor being 1:4, heating the container at the heating temperature of 120 ℃, starting a stirring device while heating, stirring the liquid mixture, stopping heating and stirring after clear transparent liquid is formed in the container, and naturally cooling the liquid mixture to the room temperature to obtain the low-transition-temperature mixture. Keeping the temperature of the mixture with the low transition temperature constant at 80 ℃, adding dimethyl sulfoxide with the mass being 5 times that of the mixture, stirring until the compound solvent is uniformly mixed, and then naturally cooling to room temperature to obtain the compound solvent for separating alkene/alkane.

The mass ratio of the compound solvent to the olefin/alkane mixture is 5:1, an olefin/alkane mixture material flow S1 enters an extraction tower from the bottom of the tower, the compound solvent S7 enters from the top of the tower, the compound solvent S7 entering from the top of the tower exchanges substances with the olefin/alkane mixture S1 in the extraction tower, the extraction temperature is 60 ℃, a light phase S3 is discharged from the top of the extraction tower, a heavy phase S2 is discharged from the bottom of the extraction tower and subjected to solvent recovery through a reduced pressure distillation tower 2, the recovered compound solvent S5 flows out from the bottom of the reduced pressure distillation tower 2 and is mixed with a fresh compound solvent S6 to obtain a material flow S7 which enters the extraction tower 1 together, and the top of the reduced pressure distillation tower obtains a high-purity olefin material flow S4. The main parameters are shown in the following table:

example four

A compound solvent for separating olefin/alkane by extraction method features that the ratio of said solvent is low-temp mixture (silver tetrafluoroborate-20: 1). The preparation method comprises the following steps: weighing corresponding mass of hydrogen bond donor sulfolane and hydrogen bond acceptor ethanolamine according to the molar ratio of the hydrogen bond donor to the hydrogen bond acceptor being 1:5, heating the container at the heating temperature of 80 ℃, starting a stirring device while heating, stirring the liquid mixture, stopping heating and stirring after clear transparent liquid is formed in the container, and naturally cooling the liquid mixture to the room temperature to obtain the low-transition-temperature mixture. Keeping the temperature of the mixture with the low transition temperature constant at 80 ℃, adding 0.05 times of silver tetrafluoroborate by mass into the mixture, stirring until the compound solvent is uniformly mixed, and naturally cooling to room temperature to obtain the compound solvent for separating alkene/alkane.

The mass ratio of the compound solvent to the olefin/alkane mixture is 8:1, an olefin/alkane mixture material flow S1 enters an extraction tower from the bottom of the tower, the compound solvent S7 enters from the top of the tower, the compound solvent S7 entering from the top of the tower exchanges substances with the olefin/alkane mixture S1 in the extraction tower, the extraction temperature is 20 ℃, a light phase S3 is discharged from the top of the extraction tower, a heavy phase S2 is discharged from the bottom of the extraction tower and subjected to solvent recovery through a reduced pressure distillation tower 2, the recovered compound solvent S5 flows out from the bottom of the reduced pressure distillation tower 2 and is mixed with a fresh compound solvent S6 to obtain a material flow S7 which enters the extraction tower 1 together, and the top of the reduced pressure distillation tower obtains a high-purity olefin material flow S4. The main parameters are shown in the following table:

EXAMPLE five

A compound solvent for separating olefin/alkane by extraction method features that the ratio of said solvent is low-temp mixture (silver acetate: 10: 1). The preparation method comprises the following steps: weighing corresponding mass of hydrogen bond donor sulfolane and hydrogen bond acceptor tetrabutylammonium chloride according to the molar ratio of the hydrogen bond donor to the hydrogen bond acceptor being 1:8, heating the container at the heating temperature of 100 ℃, starting a stirring device while heating, stirring the liquid mixture, stopping heating and stirring after clear transparent liquid is formed in the container, and naturally cooling the liquid mixture to the room temperature to obtain the low-transition-temperature mixture. And keeping the temperature of the mixture with the low transition temperature constant at 80 ℃, adding 0.1 time of copper nitrate by mass into the mixture, stirring until the compound solvent is uniformly mixed, and naturally cooling to room temperature to obtain the compound solvent for separating alkene/alkane.

The mass ratio of the compound solvent to the olefin/alkane mixture is 10:1, an olefin/alkane mixture material flow S1 enters an extraction tower from the bottom of the tower, the compound solvent S7 enters from the top of the tower, the compound solvent S7 entering from the top of the tower exchanges substances with the olefin/alkane mixture S1 in the extraction tower, the extraction temperature is 40 ℃, a light phase S3 is discharged from the top of the extraction tower, a heavy phase S2 is discharged from the bottom of the extraction tower and subjected to solvent recovery through a reduced pressure distillation tower 2, the recovered compound solvent S5 flows out from the bottom of the reduced pressure distillation tower 2 and is mixed with a fresh compound solvent S6 to obtain a material flow S7 which enters the extraction tower 1 together, and the top of the reduced pressure distillation tower obtains a high-purity olefin material flow S4. The main parameters are shown in the following table:

EXAMPLE six

A compound solvent for separating olefin/alkane by extraction method is a mixture with low transformation temperature, copper nitrate is 4: 1. The preparation method comprises the following steps: weighing hydrogen bond acceptor trimethylamine hydrochloride and hydrogen bond donor ethylene glycol in corresponding mass according to the molar ratio of the hydrogen bond acceptor to the hydrogen bond donor of 1:8 in a container, heating the container at the heating temperature of 120 ℃, starting a stirring device while heating, stirring the liquid mixture, stopping heating and stirring after clear transparent liquid is formed in the container, and naturally cooling the liquid mixture to the room temperature to obtain the low-transition-temperature mixture. And keeping the temperature of the mixture with the low transition temperature constant at 80 ℃, adding 0.25 mass time of copper nitrate into the mixture, stirring until the compound solvent is uniformly mixed, and naturally cooling to room temperature to obtain the compound solvent for separating alkene/alkane.

The mass ratio of the compound solvent to the olefin/alkane mixture is 15:1, an olefin/alkane mixture material flow S1 enters an extraction tower from the bottom of the tower, the compound solvent S7 enters from the top of the tower, the compound solvent S7 entering from the top of the tower exchanges substances with the olefin/alkane mixture S1 in the extraction tower, the extraction temperature is 60 ℃, a light phase S3 is discharged from the top of the extraction tower, a heavy phase S2 is discharged from the bottom of the extraction tower and subjected to solvent recovery through a reduced pressure distillation tower 2, the recovered compound solvent S5 flows out from the bottom of the reduced pressure distillation tower 2 and is mixed with a fresh compound solvent S6 to obtain a material flow S7 which enters the extraction tower 1 together, and the top of the reduced pressure distillation tower obtains a high-purity olefin material flow S4. The main parameters are shown in the following table:

in conclusion, the compound solvent for extracting and separating olefin/alkane has higher separation selectivity and solubility, and overcomes the defects of low separation selectivity, poor biodegradability, potential toxicity and the like of the existing solvent for separating olefin/alkane, which is easy to volatilize and causes secondary pollution. The compound solvent for separating alkene/alkane by the extraction method is obtained by compounding the low-transition-temperature mixture and the organic solvent or the metal salt, has the advantage of high separation selectivity, and can flexibly adjust the separation selectivity of the alkene/alkane by adjusting the compounding ratio of the low-transition-temperature mixture and the organic solvent or the metal salt.

Although embodiments of the present invention have been shown and described, it should be understood that the above embodiments are illustrative and not restrictive, and that any modifications, equivalents, improvements, etc. made within the spirit and principles of the invention are intended to be included within the scope of the invention.