Composite solvent for separating high-carbon-end olefin and internal olefin and use method of composite solvent

Abstract

The invention discloses a composite solvent for separating high-carbon-end olefin and internal olefin and a use method of the composite solvent. The composite solvent comprises one or more of N, N-dimethylacetamide, N-hydroxymethyl phthalimide and triethanolamine. The composite solvent has the beneficial effects that the composite solvent is wide in raw material application range and suitable for high-carbon olefins including C6-C9 olefins, and the sources include but are not limited to ethylene polymerization, C4 oligomerization or Fischer-Tropsch synthesis processes.

Description

Technical Field

[0001] The invention belongs to the technical field of high carbon olefin isomers, and in particular relates to a composite solvent for separating high carbon terminal olefins and internal olefins and a use method thereof. Background Art

[0002] High-carbon terminal olefins, generally referring to olefin compounds containing six or more carbon atoms, are widely used in the fields of petrochemicals, fine chemicals and materials science. In particular, C6-C9 olefins are used as important raw materials in the production of polymerization, synthetic materials and fine chemicals. For example, C6-C9 olefins can be used to synthesize high-performance plastics, synthetic rubbers and as intermediates for chemical reactions. With the refinement of industrial production, how to efficiently separate and purify terminal olefins has become increasingly important.

[0003] At present, there are still some challenges in the separation of high-carbon olefins, mid-terminal olefins and internal olefins. Although traditional separation methods, such as distillation and adsorption, can achieve certain separation effects, they often have problems such as high energy consumption, complex equipment, and poor selectivity. Especially when processing large-scale raw materials, traditional methods have poor cost-effectiveness and economy.

[0004] The main difficulty in separating high-carbon olefins is that there are many isomers and the boiling point difference is small. By using extractive distillation, the terminal olefins and internal olefins can be separated efficiently by changing the relative volatility between the isomers. The selection of a suitable extractant is the key to ensuring separation efficiency and economy. Therefore, the development of a new composite solvent system and its application method can not only effectively improve the separation efficiency, but also obtain excellent separation effects from different raw material sources.

[0005] At present, the solvents involved in the separation of high-carbon olefins, terminal olefins and internal olefins have problems such as narrow application range, poor versatility, complex process, and difficulty in industrialization. Taking the separation of C8 olefins as an example, CN113149806A and CN109867583A both provide methods for separating 2,4,4-trimethyl-1-pentene, but there are problems such as complex extractants and difficulty in recovery; Patent CN114805005B provides a method for separating 1-octene from Fischer-Tropsch oil-washed naphtha, but there are problems such as low conversion rate and difficulty in industrialization. Patent CN116969809B separates 1-octene from ethylene polymerization products, but there are problems such as complex process and poor versatility. Summary of the invention

[0006] In view of this, the present invention aims to propose a composite solvent for separating high-carbon terminal olefins and internal olefins and a method of use, so as to solve at least one technical problem in the background technology, and aims to solve the problems of low separation efficiency, poor selectivity, high energy consumption, and small application range of the extractant in the prior art.

[0007] To achieve the above object, the technical solution of the present invention is achieved as follows: A composite solvent for separating high-carbon terminal olefins and internal olefins. The composite solvent comprises one or more of N,N-dimethylacetamide, N-hydroxymethylphthalimide and triethanolamine.

[0008] Further, the composite solvent includes N,N-dimethylacetamide, N-hydroxymethylphthalimide and triethanolamine.

[0009] Furthermore, the composite solvent is 45wt%-98wt% of N,N-dimethylacetamide, 1wt%-40wt% of N-hydroxymethylphthalimide, and 1wt%-45wt% of triethanolamine.

[0010] The preparation method of the composite solvent for separating high-carbon terminal olefins and internal olefins comprises the following steps: heating N,N-dimethylacetamide to a specific temperature and keeping the temperature constant, adding N-hydroxymethylphthalimide and triethanolamine in sequence under stirring, and mixing them uniformly to obtain the composite solvent; Preferably, the specific temperature is 25°C-50°C: The method for using the composite solvent prepared by the method for using the composite solvent for separating high-carbon terminal olefins and internal olefins is characterized in that: high-carbon olefins enter the extractive distillation tower at the lower part of the extractive distillation tower, the composite solvent is added from the upper part of the extractive distillation tower, the high-carbon terminal olefins are discharged from the top of the tower, and the composite solvent rich in high-carbon internal olefins enters the middle part of the solvent recovery tower from the bottom of the extractive distillation tower.

[0011] Further, the top of the extractive distillation tower is cooled by a first cooler, a part of which is discharged as high-carbon terminal olefins, and the other part is returned to the extractive distillation tower; A part of the composite solvent rich in high-carbon internal olefins at the bottom of the extractive distillation tower enters the middle part of the solvent recovery tower, and the other part is heated in the first reboiler and returned to the lower part of the extractive distillation tower.

[0012] Furthermore, the method further comprises extracting high-carbon internal olefins from the top of the solvent recovery tower, and returning the composite solvent from the bottom of the solvent recovery tower to the middle of the extractive distillation tower; The top of the solvent recovery tower is cooled by a second cooler, a part of which is discharged as high-carbon internal olefins, and the other part is returned to the solvent recovery tower; A part of the composite solvent at the bottom of the solvent recovery tower returns to the middle part of the extraction distillation tower, and the other part returns to the lower part of the solvent recovery tower after being heated in the second reboiler.

[0013] Furthermore, the mass ratio of the added composite solvent to the high carbon olefin is (0.5-15):1, preferably, the mass ratio is (1-8):1.

[0014] Furthermore, the top temperature of the extractive distillation tower is 30°C~110°C, the bottom temperature is 90°C~160°C, and the operating pressure is negative pressure operation. Preferably, the operating pressure is -0.04~-0.1MPaG.

[0015] Furthermore, the top temperature of the solvent recovery tower is 30°C to 110°C, the bottom temperature is 90°C to 160°C, and the operating pressure is -0.03 to -0.10 MPaG. Preferably, the operating pressure is -0.05 to -0.09 MPaG.

[0016] Compared with the prior art, the composite solvent for separating high-carbon terminal olefins and internal olefins and the method for using the composite solvent described in the present invention have the following advantages: 1. The addition of compound components further increases the relative volatility of terminal olefins and internal olefins, which can further reduce the solvent-oil ratio in the extraction distillation separation process and reduce the solvent circulation volume.

[0017] 2. This composite solvent has stable chemical properties, is easy to recycle, and is suitable for industrialization.

[0018] 3. This composite solvent raw material has a wide range of applications. Applicable high-carbon olefins include C6-C9 olefins, and their sources include but are not limited to ethylene polymerization, C4 polymerization or Fischer-Tropsch synthesis process. BRIEF DESCRIPTION OF THE DRAWINGS

[0019] The accompanying drawings constituting a part of the present invention are used to provide a further understanding of the present invention. The exemplary embodiments of the present invention and their descriptions are used to explain the present invention and do not constitute an improper limitation of the present invention. In the accompanying drawings: Figure 1 This is a schematic diagram of the method for using the composite solvent described in Example 1 of the present invention.

[0020] Description of reference numerals: 1. Extraction distillation tower; 2. First cooler; 3. First reboiler; 4. Solvent recovery tower; 5. Second cooler; 6. First reboiler. DETAILED DESCRIPTION

[0021] It should be noted that, in the absence of conflict, the embodiments of the present invention and the features in the embodiments may be combined with each other.

[0022] The present invention will be described in detail below with reference to the accompanying drawings and in conjunction with embodiments.

[0023] A composite solvent for separating high-carbon terminal olefins and internal olefins, the composite solvent comprising one or more of N,N-dimethylacetamide, N-hydroxymethylphthalimide, and triethanolamine. The composite solvent comprises N,N-dimethylacetamide, N-hydroxymethylphthalimide, and triethanolamine. The composite solvent is 45wt%-98wt% of N,N-dimethylacetamide, 1wt%-40wt% of N-hydroxymethylphthalimide, and 1wt%-45wt% of triethanolamine.

[0024] The preparation method of the composite solvent for separating high-carbon terminal olefins and internal olefins comprises the following steps: heating N,N-dimethylacetamide to 25°C-50°C and keeping the temperature constant, adding N-hydroxymethylphthalimide and triethanolamine in sequence under stirring, and mixing them evenly to obtain the composite solvent; The method for using the composite solvent prepared by the above-mentioned method for using a composite solvent for separating high-carbon terminal olefins and internal olefins is characterized in that: high-carbon olefins enter the extractive distillation tower 1 at the lower part of the extractive distillation tower 1, the composite solvent is added from the upper part of the extractive distillation tower 1, the high-carbon terminal olefins are discharged from the top of the tower, and the composite solvent rich in high-carbon internal olefins enters the middle part of the solvent recovery tower 4 from the bottom of the extractive distillation tower 1.

[0025] The top of the extractive distillation tower 1 is cooled by the first cooler 2, a part of which discharges high-carbon terminal olefins, and the other part returns to the extractive distillation tower 1; a part of the composite solvent rich in high-carbon internal olefins at the bottom of the extractive distillation tower 1 enters the middle part of the solvent recovery tower 4, and the other part is heated by the first reboiler 3 and returned to the lower part of the extractive distillation tower 1. It also includes the extraction of high-carbon internal olefins from the top of the solvent recovery tower 4, and the composite solvent is returned to the middle part of the extractive distillation tower 1 from the bottom of the solvent recovery tower 4; the top of the solvent recovery tower 4 is cooled by the second cooler 5, a part of which discharges high-carbon internal olefins, and the other part returns to the solvent recovery tower 4; a part of the composite solvent at the bottom of the solvent recovery tower 4 returns to the middle part of the extractive distillation tower 1, and the other part is heated by the second reboiler and returned to the lower part of the solvent recovery tower 4.

[0026] The mass ratio of the added composite solvent to the high carbon olefin is (0.5-8):1, preferably, the mass ratio is (1-5):1. The top temperature of the extractive distillation tower 1 is 30°C~110°C, the bottom temperature is 90°C~160°C, and the operating pressure is negative pressure operation, preferably, the operating pressure is -0.04~-0.1MPaG, the top temperature of the solvent recovery tower 4 is 30°C~110°C, the bottom temperature is 90°C-160°C, and the operating pressure is -0.03~-0.10MPaG, preferably, the operating pressure is -0.05~-0.09MPaG.

[0027] Example 1 Diisobutylene was separated by extractive distillation. The raw material diisobutylene consisted of 79.8% 2,4,4-trimethyl-1-pentene and 20.2% 2,4,4-trimethyl-2-pentene. The compound solvent is a mixture of 75% N,N-dimethylacetamide and 25% N-hydroxymethylphthalimide.

[0028] N,N-dimethylacetamide is heated to 25° C. and the temperature is kept constant. N-hydroxymethylphthalimide is added under stirring and mixed evenly to obtain the composite solvent.

[0029] Diisobutylene was added to extractive distillation tower 1 from the lower part of extractive distillation tower 1, and the composite solvent was added from the upper part of extractive distillation tower 1. 2,4,4-trimethyl-1-pentene was discharged from the top of the tower, and the composite solvent rich in 2,4,4-trimethyl-2-pentene was discharged from the bottom of the tower and entered the solvent recovery tower 4. The operating conditions of extractive distillation tower 1 were: agent-oil ratio 3:1, tower top temperature 50°C, tower bottom temperature 103°C, and pressure -0.05MPa. The top temperature of solvent recovery tower 4 was 55°C, the bottom temperature was 55°C, and the pressure was -0.07MPaG. At this time, the purity of 2,4,4-trimethyl-1-pentene was 95.3%.

[0030] Example 2 Diisobutylene was separated by extractive distillation. The raw material diisobutylene consisted of 79.8% 2,4,4-trimethyl-1-pentene and 20.2% 2,4,4-trimethyl-2-pentene. The compound solvent is a mixture of 75wt% N,N-dimethylacetamide, 13wt% N-hydroxymethylphthalimide and 12wt% triethanolamine; N,N-dimethylacetamide is heated to ...°C and the temperature is kept constant, N-hydroxymethylphthalimide and triethanolamine are added in sequence under stirring, and the composite solvent is obtained after mixing evenly; Extraction distillation tower 1 separates 2,4,4-trimethyl-1-pentene from the crude diisobutylene component. Diisobutylene is added to extraction distillation tower 1 from the lower part of extraction distillation tower 1, 2,4,4-trimethyl-1-pentene is discharged from the top of the tower, and the composite solvent rich in 2,4,4-trimethyl-2-pentene is discharged from the bottom of the tower into solvent recovery tower 4. The operating conditions of extraction distillation tower 1 are: agent-oil ratio 1:1, tower top temperature 57°C, tower bottom temperature 110°C, and pressure -0.07MPa. Solvent recovery tower 4 has a tower top temperature of 65°C, a tower bottom temperature of 120°C, and a pressure of -0.08MPaG. At this time, the purity of 2,4,4-trimethyl-1-pentene is 98.5%.

[0031] Example 3 The C8 olefins in the Fischer-Tropsch synthetic oil were separated by extractive distillation. The specific composition of the C8 olefins was: 97.6% 1-octene, 1.5% 2-octene, and 0.9% C8 alkane. The compound solvent was a mixture of 55wt% N,N-dimethylacetamide, 33% N-hydroxymethylphthalimide, and 12wt% triethanolamine. N,N-dimethylacetamide is heated to 35° C. and the temperature is kept constant, and N-hydroxymethylphthalimide and triethanolamine are added in sequence under stirring, and the mixture is mixed uniformly to obtain the composite solvent; Extraction distillation tower 1 separates crude Fischer-Tropsch C8 olefins. Crude Fischer-Tropsch C8 olefins are added to extraction distillation tower 1 from the lower part of extraction distillation tower 1, 1-octene is discharged from the top of the tower, and the composite solvent rich in internal olefins is discharged from the bottom of the tower into solvent recovery tower 4. The operating conditions of extraction distillation tower 1 are: agent-oil ratio 2.5:1, tower top temperature 77°C, tower bottom temperature 130°C, and pressure -0.08MPa. Solvent recovery tower 4 has a tower top temperature of 78°C, a tower bottom temperature of 130°C, and a pressure of -0.08MPaG. At this time, the purity of 1-octene is 99.3%.

[0032] Example 4 The difference from Example 2 is: The composite solvent is: the composite solvent is a mixture of 75wt% N,N-dimethylacetamide and 25% triethanolamine triethanolamine; At this time, the purity of 2,4,4-trimethyl-1-pentene was 96.1%.

[0033] Example 5 The C6 olefins in the Fischer-Tropsch synthetic oil were separated by extractive distillation. The specific composition of the C6 olefins was: 98.0% 1-hexene, 1.2% 2-hexene, and 0.8% C6 alkane. The compound solvent was a mixture of 80wt% N,N-dimethylacetamide, 13% N-hydroxymethylphthalimide, and 7wt% triethanolamine. N,N-dimethylacetamide is heated to 45° C. and the temperature is kept constant, and N-hydroxymethylphthalimide and triethanolamine are added in sequence under stirring, and the mixture is mixed evenly to obtain the composite solvent; Extraction distillation tower 1 separates crude Fischer-Tropsch C6 olefins. Crude Fischer-Tropsch C6 olefins are added to extraction distillation tower 1 from the lower part of extraction distillation tower 1, 1-hexene is discharged from the top of the tower, and the composite solvent rich in internal olefins is discharged from the bottom of the tower into solvent recovery tower 4. The operating conditions of extraction distillation tower 1 are: agent-oil ratio 4.0:1, tower top temperature 55°C, tower bottom temperature 110°C, and pressure -0.05MPa. Solvent recovery tower 4 has a tower top temperature of 58°C, a tower bottom temperature of 110°C, and a pressure of -0.05MPaG. At this time, the purity of 1-hexene is 99.1%.

[0034] Example 6 The C7 olefins in the Fischer-Tropsch synthetic oil were separated by extractive distillation. The specific composition of the C7 olefins was: 97.8% 1-heptene, 1.6% 2-heptene, and 0.6% C7 alkane. The compound solvent was a mixture of 70wt% N,N-dimethylacetamide, 13% N-hydroxymethylphthalimide, and 17wt% triethanolamine. N,N-dimethylacetamide is heated to 38° C. and the temperature is kept constant, and N-hydroxymethylphthalimide and triethanolamine are added in sequence under stirring, and the mixture is mixed evenly to obtain the composite solvent; Extraction distillation tower 1 separates crude Fischer-Tropsch C6 olefins. Crude Fischer-Tropsch C7 olefins are added to extraction distillation tower 1 from the lower part of extraction distillation tower 1, 1-heptene is discharged from the top of the tower, and the composite solvent rich in internal olefins is discharged from the bottom of the tower into solvent recovery tower 4. The operating conditions of extraction distillation tower 1 are: agent-oil ratio 3.0:1, tower top temperature 68°C, tower bottom temperature 120°C, and pressure -0.07MPa. Solvent recovery tower 4 has a tower top temperature of 73°C, a tower bottom temperature of 120°C, and a pressure of -0.07MPaG. At this time, the purity of 1-hexene is 98.6%.

[0035] Example 7 The carbon nine olefins in the Fischer-Tropsch synthetic oil were separated by extractive distillation. The specific composition of the carbon nine olefins was: 95.0% 1-nonene, 2.2% 2-nonene, and 2.8% C9 alkanes. The compound solvent was a mixture of 50wt% N,N-dimethylacetamide, 33% N-hydroxymethylphthalimide, and 17wt% triethanolamine. N,N-dimethylacetamide is heated to 25° C. and the temperature is kept constant, and N-hydroxymethylphthalimide and triethanolamine are added in sequence under stirring, and the mixture is mixed evenly to obtain the composite solvent; Extraction distillation tower 1 separates crude Fischer-Tropsch carbon nine olefins. Crude Fischer-Tropsch carbon nine olefins are added to extraction distillation tower 1 from the lower part of extraction distillation tower 1, 1-nonene is discharged from the top of the tower, and the composite solvent rich in internal olefins is discharged from the bottom of the tower into the solvent recovery tower 4. The operating conditions of extraction distillation tower 1 are: agent-oil ratio 5.0:1, tower top temperature 83°C, tower bottom temperature 135°C, and pressure -0.09MPa. Solvent recovery tower 4 has a tower top temperature of 87°C, a tower bottom temperature of 135°C, and a pressure of -0.09MPaG. At this time, the purity of 1-hexene is 97.8% yield.

[0036] The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions, improvements, etc. made within the spirit and principle of the present invention should be included in the protection scope of the present invention.

Claims

1. A composite solvent for separating high-carbon terminal olefins and internal olefins, characterized in that: The composite solvent includes one or more of N,N-dimethylacetamide, N-hydroxymethylphthalimide and triethanolamine.

2. The composite solvent for separating high-carbon terminal olefins and internal olefins according to claim 1, characterized in that: The composite solvent includes N,N-dimethylacetamide, N-hydroxymethylphthalimide and triethanolamine.

3. The composite solvent for separating high-carbon terminal olefins and internal olefins according to claim 1, characterized in that: The composite solvent comprises 45wt%-98wt% of N,N-dimethylacetamide, 1wt%-40wt% of N-hydroxymethylphthalimide and 1wt%-45wt% of triethanolamine.

4. A method for preparing a composite solvent for separating high-carbon terminal olefins and internal olefins according to any one of claims 1 to 3, characterized in that: The method comprises the following steps: heating N,N-dimethylacetamide to a specific temperature and then keeping the temperature constant, adding N-hydroxymethylphthalimide and triethanolamine in sequence under stirring, and mixing them evenly to obtain the composite solvent; Preferably, the specific temperature is 25°C-50°C.

5. The method for using the composite solvent for separating high-carbon terminal olefins and internal olefins according to claim 4 is characterized in that: The high carbon olefins enter the extractive distillation tower at the lower part, the composite solvent is added from the upper part of the extractive distillation tower, the high carbon terminal olefins are discharged from the top of the tower, and the composite solvent rich in high carbon internal olefins enters the middle part of the solvent recovery tower from the bottom of the extractive distillation tower.

6. The method for using the composite solvent according to claim 5, characterized in that: The top of the extractive distillation tower is cooled by a first cooler, a part of which is discharged as high-carbon terminal olefins, and the other part is returned to the extractive distillation tower; A part of the composite solvent rich in high-carbon internal olefins at the bottom of the extractive distillation tower enters the middle part of the solvent recovery tower, and the other part is heated in the first reboiler and returned to the lower part of the extractive distillation tower.

7. The method for using the composite solvent according to claim 5, characterized in that: The high-carbon internal olefin is extracted from the top of the solvent recovery tower, and the composite solvent is returned from the bottom of the solvent recovery tower to the middle of the extractive distillation tower; The top of the solvent recovery tower is cooled by a second cooler, a part of which is discharged as high-carbon internal olefins, and the other part is returned to the solvent recovery tower; A part of the composite solvent at the bottom of the solvent recovery tower returns to the middle part of the extractive distillation tower, and the other part returns to the lower part of the solvent recovery tower after being heated in the second reboiler.

8. The method for using the composite solvent according to claim 5, characterized in that: The mass ratio of the added composite solvent to the high carbon olefin is (0.5-15):1, preferably, the mass ratio is (1-8):

1.

9. The method for using the composite solvent according to claim 5, characterized in that: The top temperature of the extractive distillation tower is 30°C~110°C, the bottom temperature is 90°C~160°C, and the operating pressure is negative pressure operation. Preferably, the operating pressure is -0.04~-0.1MPaG.

10. The method for using the composite solvent according to claim 5, characterized in that: The top temperature of the solvent recovery tower is 30°C to 110°C, the bottom temperature is 90°C to 160°C, and the operating pressure is -0.03 to -0.10 MPaG. Preferably, the operating pressure is -0.05 to -0.09 MPaG.

Images