Compound extraction agent and method for separating 1-pentene from alkane-alkene mixture of 1-pentene and n-pentane

Abstract

The invention provides a compound extraction agent and a method for separating 1-pentene from an alkene mixture of 1-pentene and n-pentane. The compound extraction agent comprises a ketone substance, a nitrile substance and a pyrrolidone substance, the mass ratio of the ketone substance to the nitrile substance to the pyrrolidone substance is (20-30): (15-20): (50-65), and during separation, the weight ratio of the alkane-olefin mixture to the compound extraction agent is 1: (2-20). Compared with conventional rectification, the method has the advantages that multiple extraction agents are compounded together, 1-pentene and n-pentane can be effectively separated, the purity of the obtained 1-pentene is improved, the process is simple, investment and energy consumption of fixed equipment required for separating 1-pentene can be greatly reduced, and the method has important economic and social benefits. Under the same rectification condition, compared with a rectification process without using the compound extraction agent, the purity of the 1-pentene after using the compound extraction agent is improved to a certain extent.

Description

Technical Field

[0001] The present invention belongs to the technical field of adsorbents, and in particular relates to a composite extractant and a method for separating 1-pentene from an alkene-alkene mixture of 1-pentene and n-pentane. Background Art

[0002] Raffinate C5 is a byproduct of ethylene crackers, primarily composed of C5 hydrocarbons, including isoprene, pentene, and n-pentane. These hydrocarbons are not fully converted to ethylene during the cracking process and are therefore collected and referred to as raffinate C5. Raffinate C5 has a variety of applications, including the production of petroleum resins, pesticide intermediates, and fine chemical raw materials. For example, isoprene can be used to produce C5 petroleum resins, pesticide intermediates, linalool, and flavors and fragrances; pentene can be used for polymer material modification and the synthesis of complex organometallic compounds; and n-pentane can be used as a foaming agent for expanded polystyrene and a solvent for linear low-density polyethylene. Isoprene can generally be separated by DMF extraction, but the remaining components, such as 1-pentene (boiling point 30°C) and n-pentane (boiling point 36°C), have similar boiling points, making effective separation of 1-pentene and n-pentane by distillation difficult while maintaining low costs. For mixtures containing pentene and pentane, the current common treatment method is to fully hydrogenate the product to produce n-pentane and isopentane, such as Chinese patents ZL02145057.9 and ZL02145056.0. However, the above treatment method will result in the inability to better utilize 1-pentene, which has higher application value, and the increase in product added value is seriously restricted. Summary of the Invention

[0003] (1) Technical issues to be resolved

[0004] The present invention provides a composite extractant and method for separating 1-pentene from an alkene mixture of 1-pentene and n-pentane, so as to solve the technical problems of large fixed equipment investment, high energy consumption and difficulty in separation in conventional distillation separation of 1-pentene.

[0005] (2) Technical solution

[0006] In order to solve the above technical problems, the present invention proposes a composite extractant for separating 1-pentene from an alkene mixture of 1-pentene and n-pentane, wherein the composite extractant comprises ketones, nitriles and pyrrolidones.

[0007] Furthermore, the ketone substance is at least one of butanone and pentanone.

[0008] Furthermore, the nitrile substance is at least one of acetonitrile, butyronitrile and capronitrile.

[0009] Furthermore, the pyrrolidone substance is at least one of N-methylpyrrolidone and N-ethylpyrrolidone.

[0010] Furthermore, the mass ratio of ketone substances, nitrile substances and pyrrolidone substances is (20-30):(15-20):(50-65).

[0011] Furthermore, the mass ratio of ketone substances, nitrile substances and pyrrolidone substances is 25:17:58.

[0012] In addition, the present invention also provides a method for separating 1-pentene from an alkene mixture of 1-pentene and n-pentane, which comprises introducing the composite extractant for separating 1-pentene from an alkene mixture of 1-pentene and n-pentane into a distillation tower.

[0013] Furthermore, the weight ratio of the alkane-alkene mixture to the extractant in the distillation tower is 1:(2-20).

[0014] Furthermore, the method specifically comprises the following steps:

[0015] S1. A mixture of 1-pentene and n-pentane is added to the bottom of a distillation column, and a composite extractant is added to the column. The extractant feed temperature is 32°C, the tower top temperature is 30°C, the tower bottom temperature is 45°C, the operating pressure is atmospheric pressure, the reflux ratio is fixed at 1, the n-pentane material is discharged from the top of the column, and the 1-pentene and composite extractant are enriched in the bottom of the column;

[0016] S2. The bottom enriched liquid in step S1 is distilled to separate 1-pentene and the compound extractant. The top temperature is 33°C, the bottom temperature is 70°C, the operating pressure is atmospheric pressure, the reflux ratio is fixed at 1, the 1-pentene product is collected at the top of the tower, and the compound extractant is collected in the bottom of the tower.

[0017] Furthermore, in step S1, the theoretical number of plates of the distillation tower is 60, and the composite extractant is added to the tower from the 5th plate; in step S2, the theoretical number of plates of the distillation tower is 40, and the bottom enriched liquid is added from the 35th plate.

[0018] (3) Beneficial effects

[0019] The present invention proposes a compound extractant and method for separating 1-pentene from an alkene mixture of 1-pentene and n-pentane. The compound extractant includes ketones, nitriles and pyrrolidones, and the mass ratio of ketones, nitriles and pyrrolidones is (20-30):(15-20):(50-65). When separating, the weight ratio of the alkene mixture to the compound extractant is 1:(2-20). Compared with conventional distillation, the present invention compounds multiple extractants together, which can effectively separate 1-pentene from n-pentane and improve the purity of the obtained 1-pentene. The process is simple and can significantly reduce the investment in fixed equipment and energy consumption required for separating 1-pentene, which has important economic and social benefits. Under the same distillation conditions, compared with the distillation process without using the compound extractant, the purity of 1-pentene is improved to a certain extent after using the compound extractant. DETAILED DESCRIPTION

[0020] In order to make the purpose, content and advantages of the present invention more clear, the specific implementation methods of the present invention are further described in detail below with reference to the embodiments.

[0021] The effects of compound extractants composed of different extractants on the purification of 1-pentene are shown in Table 1.

[0022] Table 1 Effect of compound extractants composed of different extractants on the purification of 1-pentene

[0023]

[0024]

[0025] The effects of compound extractants composed of the same extractant in different compounding ratios on the purification of 1-pentene are shown in Table 2.

[0026] Table 2 Effects of compound extractants with different compound ratios on the purification of 1-pentene

[0027]

[0028] The effects of different weight ratios of alkane-ene mixture and compound extractant on the purification of 1-pentene are shown in Table 3.

[0029] Table 3 Effect of different weight ratios on 1-pentene refining

[0030]

[0031] Comparative Example

[0032] The alkane-alkene mixture was subjected to 1-pentene distillation separation according to the distillation tower and distillation conditions used in the above test, but without using the composite extractant, and the 1-pentene purity was 60.3%.

[0033] The above test results show that by compounding a variety of different types of extractants in a certain proportion and under a certain material weight ratio, efficient separation of 1-pentene can be achieved.

[0034] The above is only a preferred embodiment of the present invention. It should be pointed out that for ordinary technicians in this technical field, several improvements and modifications can be made without departing from the technical principles of the present invention. These improvements and modifications should also be regarded as the scope of protection of the present invention.

Claims

1. A composite extractant for separating 1-pentene from an alkene mixture of 1-pentene and n-pentane, characterized in that: The composite extractant comprises ketone substances, nitrile substances and pyrrolidone substances.

2. The composite extractant for separating 1-pentene from an alkene mixture of 1-pentene and n-pentane according to claim 1, wherein: The ketone substance is at least one of butanone and pentanone.

3. The composite extractant for separating 1-pentene from an alkene mixture of 1-pentene and n-pentane according to claim 1, wherein: The nitrile substance is at least one of acetonitrile, butyronitrile and hexanenitrile.

4. The composite extractant for separating 1-pentene from an alkene mixture of 1-pentene and n-pentane according to claim 1, wherein: The pyrrolidone substance is at least one of N-methylpyrrolidone and N-ethylpyrrolidone.

5. The composite extractant for separating 1-pentene from an alkene mixture of 1-pentene and n-pentane according to claim 1, wherein The mass ratio of the ketone substance, the nitrile substance and the pyrrolidone substance is (20-30):(15-20):(50-65).

6. The composite extractant for separating 1-pentene from an alkene mixture of 1-pentene and n-pentane according to claim 5, characterized in that The mass ratio of the ketone substance, the nitrile substance and the pyrrolidone substance is 25:17:

58.

7. A method for separating 1-pentene from an alkene mixture of 1-pentene and n-pentane, characterized in that: The method comprises introducing the composite extractant for separating 1-pentene from an alkene-alkene mixture of 1-pentene and n-pentane according to any one of claims 1 to 6 into a distillation tower.

8. The method for separating 1-pentene from an alkene mixture of 1-pentene and n-pentane according to claim 7, wherein: The weight ratio of the alkane-alkene mixture to the extractant in the distillation tower is 1:(2-20).

9. The method for separating 1-pentene from an alkene mixture of 1-pentene and n-pentane according to claim 8, wherein: The method specifically comprises the following steps: S1. A mixture of 1-pentene and n-pentane is added to the bottom of a distillation column, and a composite extractant is added to the column. The extractant feed temperature is 32°C, the tower top temperature is 30°C, the tower bottom temperature is 45°C, the operating pressure is atmospheric pressure, the reflux ratio is fixed at 1, the n-pentane material is discharged from the top of the column, and the 1-pentene and composite extractant are enriched in the bottom of the column; S2. The bottom enriched liquid in step S1 is distilled to separate 1-pentene and the compound extractant. The top temperature is 33°C, the bottom temperature is 70°C, the operating pressure is atmospheric pressure, the reflux ratio is fixed at 1, the 1-pentene product is collected at the top of the tower, and the compound extractant is collected in the bottom of the tower.

10. The method for separating 1-pentene from an alkene mixture of 1-pentene and n-pentane according to claim 9, wherein: In step S1, the distillation tower has 60 theoretical plates, and the composite extractant is added to the tower from the 5th plate; in step S2, the distillation tower has 40 theoretical plates, and the bottom enriched liquid is added from the 35th plate.

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