A system and method for separating and recovering catalyst in a process for preparing adiponitrile from butadiene

Abstract

The present application relates to a kind of catalyst separation recovery system and method in butadiene method preparation adiponitrile process, belong to chemical production technical field.The separation recovery system of the present application includes extraction column, solvent recovery first-stage flash tank heater, solvent recovery first-stage flash tank, solvent recovery second-stage flash tank, recovery ligand cooler, raffinate solvent recovery flash tank heater and raffinate solvent recovery flash tank, waste liquid flash tank, waste liquid recovery wiped film evaporator and waste liquid recovery wiped film condenser.Compared with prior art, the present application can realize the effective separation and recovery of poisoned catalyst, catalyst ligand and dinitrile compound in butadiene method synthesis adiponitrile process, significantly improve the economy of process.

Description

Technical Field

[0001] This invention relates to the field of chemical production technology, and in particular to a catalyst separation and recovery system and method in the butadiene-to-adiponitrile process. Background Technology

[0002] Adiponitrile (ADN) is a commercially valuable and widely used intermediate industrially for producing nylon polyamides that can be made into films, fibers, and molded products. Currently, the main synthetic routes for adiponitrile include the butadiene method, the acrylonitrile method, and the adipic acid method. Among these, the butadiene method, which involves the hydrocyanation of 1,3-butadiene (BD) in the presence of various phosphorus-containing transition metal complexes, is the most widely used due to its advantages of low energy consumption and high production capacity.

[0003] For example, CN113444018A discloses a method for producing adiponitrile from 1,3-butadiene and hydrogen cyanide. This process route includes at least the following reactions: primary cyanation of 1,3-butadiene, isomerization of 2-methyl-3-butenonitrile to generate 3PN, and secondary cyanation of 3PN and other pentenonitriles to generate adiponitrile and other dinitrile substances. Many catalytic systems exist in the butadiene-based process for producing adiponitrile, including but not limited to: (1) In the presence of a catalyst, 1,3-butadiene (BD) undergoes a primary cyanidation reaction with hydrogen cyanide (HCN) via hydrocyanation, producing reaction byproducts such as 3-pentenonitrile (3PN), 2-methyl-3-butenonitrile (2M3BN), and methylglutaronitrile (MGN). This process is a primary cyanidation reaction, and the catalyst used in this process is called a primary cyanidation catalyst. The effluent from the primary cyanidation reaction is separated in a specific manner to obtain a 3PN-rich stream, a catalyst-rich stream, and an MGN-rich stream, respectively, allowing for the recycling of the primary cyanidation catalyst.

[0004] (2) To improve the yield of 3PN in the primary cyanidation reaction, 2M3BN can be catalytically isomerized to 3PN in the presence of nickel-based ligands. This process is called isomerization reaction, and the catalyst used in this process is called isomerization catalyst. The reaction effluent is separated by a specific method to obtain a 3PN- and MGN-rich stream and a catalyst-rich stream, and the isomerization catalyst can be recycled.

[0005] (3) In the presence of transition metal complexes containing multiple phosphorus ligands, 3PN and 2M3PN undergo a secondary cyanidation reaction to generate dinitrile compounds such as adiponitrile, methylglutaronitrile (MGN), and ethylbutadionitrile (ESN). This reaction unit is called the secondary cyanidation unit, and the catalyst flowing through this unit is called the secondary cyanidation catalyst.

[0006] Furthermore, dinitrile compounds are more difficult to separate from the catalyst. In high-concentration dinitrile solutions, the thermal stability of the catalyst decreases, and nickel-ligand complexes in the catalyst may undergo thermal degradation, releasing free ligands and uncoordinated nickel. Therefore, the catalyst-rich stream separated from the reaction unit has a complex composition, including deactivated catalyst, ligands produced by catalyst thermal decomposition, and dinitrile compounds, making separation difficult. Since the boiling points of dinitrile compounds are similar to those of the catalyst system, and both have relatively high boiling points, effective separation using conventional atmospheric distillation is difficult.

[0007] Therefore, based on the above-mentioned process reaction route for synthesizing adiponitrile from butadiene, it is urgent to develop a suitable catalyst separation and recovery system and method to achieve the recycling and recovery of catalyst ligands in the catalyst-rich circulating stream and the recovery of the target product adiponitrile, thereby reducing the consumption of catalyst ligand raw materials in the whole process and increasing the yield of the target product adiponitrile. Summary of the Invention

[0008] The purpose of this invention is to provide a catalyst separation and recovery system and method in the butadiene-to-adiponitrile process, so as to achieve effective separation and recovery of poisoned catalyst, catalyst ligands and dinitrile compounds in the butadiene-to-adiponitrile synthesis process, thereby reducing the consumption of catalyst ligand raw materials in the whole process and increasing the yield of the target product adiponitrile.

[0009] The objective of this invention can be achieved through the following technical solutions: The first aspect of this invention provides a separation and recovery system for the catalyst in the butadiene-to-adiponitrile process, the separation and recovery system comprising: An extraction column is used to extract cyclohexane by mixing a catalyst-rich stream containing recovered catalyst, catalyst ligands and dinitrile compounds. The solvent recovery primary flash tank heater is connected to the extract phase outlet at the top of the extraction tower; The solvent recovery primary flash tank is connected to the solvent recovery primary flash tank heater; The secondary flash tank for solvent recovery is connected to the liquid phase outlet at the bottom of the primary flash tank for solvent recovery; The ligand recovery cooler is connected to the liquid phase outlet at the bottom of the solvent recovery secondary flash tank and is used to recover the catalyst ligands obtained after secondary flash evaporation. The raffinate solvent recovery flash tank heater is connected to the raffinate outlet at the bottom of the extraction tower; A flash evaporator for recovering residual solvents is connected to a heater for recovering residual solvents. Waste liquid flash tank, connected to the waste liquid outlet at the bottom of the raffinate solvent recovery flash tank, is used for the preliminary separation of dinitrile compounds and poisoned catalyst; The waste liquid recovery scraped film evaporator is connected to the heavy phase outlet at the bottom of the waste liquid flash tank for further separation of dinitrile compounds and poisoned catalysts; The waste liquid recovery scraped film condenser, connected to the top outlet of the waste liquid recovery scraped film evaporator, is used to cool and recover dinitrile compounds.

[0010] Furthermore, the top outlet of the heater of the solvent recovery primary flash tank is connected to the top condenser of the solvent recovery primary flash tank for recovering cyclohexane separated after primary flash evaporation.

[0011] Furthermore, the top outlet of the solvent recovery secondary flash tank is connected to the top condenser of the solvent recovery secondary flash tank for recovering the residual cyclohexane separated after the secondary flash evaporation.

[0012] Furthermore, the non-condensable gas outlet of the top condenser of the primary flash tank for solvent recovery and the gas phase outlet of the top of the residual solvent recovery flash tank are both connected to the inlet of the top condenser of the secondary flash tank for solvent recovery.

[0013] Furthermore, the outlet of the top condenser of the solvent recovery secondary flash tank is connected to the solvent recovery vacuum system.

[0014] Furthermore, the exhaust gas outlet of the solvent recovery vacuum system is connected to a vacuum exhaust gas condenser for the recovery of cyclohexane.

[0015] Furthermore, the top light phase outlet of the waste liquid flash tank is connected to the waste liquid recovery scraped film condenser for recovering the dinitrile obtained from the initial flash separation.

[0016] Furthermore, the non-condensable gas outlet of the waste liquid recovery scraped film condenser is connected to the scraped film recovery vacuum system.

[0017] A second aspect of this invention provides a method for separating and recovering a catalyst in a butadiene-to-adiponitrile process. This method is based on the aforementioned separation and recovery system and specifically includes the following steps: I. Extraction: A catalyst-rich stream containing recovered catalyst, catalyst ligands, and dinitrile compounds is fed into the extraction column, where solvent extraction is performed using cyclohexane. II. Recovery of ligands and cyclohexane: The upper extract phase after extraction is heated by the heater of the solvent recovery primary flash tank and then fed into the solvent recovery primary flash tank. The cyclohexane extracted in the primary flash is recovered after cooling. The heavy phase after primary flash is fed into the solvent recovery secondary flash tank for stripping and secondary flash. The cyclohexane extracted in the secondary flash is recovered after cooling. The heavy phase from the secondary flash is cooled by the ligand recovery cooler to recover the ligands. III. Recovery of dinitrile compounds: The lower raffinate phase after extraction is fed into the raffinate solvent recovery flash tank heater. After heating, it is sent to the raffinate solvent recovery flash tank. The residual cyclohexane in the raffinate phase is carried out from the top of the tank with the gas phase and recovered after condensation. The waste liquid at the bottom of the raffinate solvent recovery flash tank is sent to the waste liquid flash tank. The light phase at the top of the tank is fed into the waste liquid recovery scraped film condenser to recover dinitrile compounds. The heavy phase at the bottom of the tank flows into the waste liquid recovery scraped film evaporator. The evaporated dinitrile is fed into the waste liquid recovery scraped film condenser to recover dinitrile compounds. The poisoned catalyst waste liquid flows out from the bottom of the waste liquid recovery scraped film evaporator.

[0018] Furthermore, the pressure range at the top of the extraction column is 0~50 kPa.

[0019] Furthermore, the temperature range at the top of the extraction column is 80~85℃.

[0020] Furthermore, the temperature range of the extraction tower kettle is 85~90 ℃.

[0021] Furthermore, the extraction tower is a rotary extraction tower with 40 to 42 rotating discs.

[0022] Furthermore, the feed volume ratio of the recovered catalyst to cyclohexane is 1:(1.5~2).

[0023] Furthermore, the outlet temperature range of the solvent recovery primary flash tank heater is 110~130 ℃.

[0024] Furthermore, the pressure range of the primary flash tank for solvent recovery is 60~65 kPa.

[0025] Furthermore, the internal temperature range of the solvent recovery primary flash tank is 108~128 ℃.

[0026] Furthermore, the pressure range of the secondary flash tank for solvent recovery is 25~35 kPa.

[0027] Furthermore, the stripping gas inside the secondary flash tank for solvent recovery is nitrogen gas at 0.2~0.4 MPa, and the mass ratio of stripping nitrogen gas to feed stream is 1:(5~10).

[0028] Furthermore, the outlet temperature range of the heater for the residual solvent recovery flash tank is 150~160 ℃.

[0029] Furthermore, the pressure range of the flash evaporator for recovering residual solvent is 70~75 kPa.

[0030] Furthermore, the internal temperature range of the flash evaporator for recovering residual solvent is 148~158 ℃.

[0031] Furthermore, the stripping gas inside the flash evaporator for recovering the residual solvent is nitrogen at 0.2~0.4 MPa, and the mass ratio of stripping nitrogen to the feed stream is 1:(5~10).

[0032] Furthermore, the internal pressure of the waste liquid flash tank is in the range of 50~60 kPa.

[0033] Furthermore, the internal temperature range of the waste liquid flash evaporator is 145~155 ℃.

[0034] Furthermore, the pressure range inside the waste liquid recovery scraped film evaporator is 10~20 kPa.

[0035] Furthermore, the temperature range of the waste liquid recovery scraped film evaporator is 180~210 ℃.

[0036] Furthermore, the rotational speed of the waste liquid recovery scraped film evaporator is 40~80 rpm.

[0037] Furthermore, the cyclohexane extracted from the first-stage flash evaporation is fed into the top condenser of the solvent recovery first-stage flash evaporation tank, and the outlet temperature of the top condenser of the solvent recovery first-stage flash evaporation tank is 40~60 ℃.

[0038] Furthermore, the cyclohexane extracted from the secondary flash vapor is fed into the top condenser of the solvent recovery secondary flash tank, and the outlet temperature of the top condenser of the solvent recovery secondary flash tank is 20~30 ℃.

[0039] Furthermore, the condensate output from the top condenser of the solvent recovery secondary flash tank is further input into the solvent recovery vacuum system, and the working fluid of the solvent recovery vacuum system is cyclohexane.

[0040] Furthermore, the vacuum exhaust gas generated by the solvent recovery vacuum system is input into the vacuum exhaust gas condenser, and the outlet temperature of the vacuum exhaust gas condenser is 10~20 ℃.

[0041] Compared with the prior art, the present invention has the following technical advantages: (1) The present invention first uses cyclohexane as an extraction solvent to perform liquid-liquid extraction on a catalyst-rich stream containing deactivated catalyst, catalyst ligand and dinitrile compounds, and then recovers cyclohexane and catalyst ligand in the extraction phase by two-stage flash evaporation; at the same time, dinitrile compounds and poisoned catalyst in the raffinate phase are separated and recovered by two-stage flash evaporation and scraped film evaporation technology, thus successfully realizing the effective separation and recovery of poisoned catalyst, catalyst ligand and dinitrile compounds in the butadiene synthesis of adiponitrile, and significantly improving the economic efficiency of the process.

[0042] (2) This invention is applicable to the recycling and recovery of catalyst ligands in the catalyst-rich circulating stream and the recovery of the target product, dinitrile compounds, in the butadiene-to-adiponitrile synthesis process. By utilizing this catalyst recycling and recovery system, the consumption of ligand raw materials in the entire process unit can be reduced, and the yield of the target product, adiponitrile, can be increased. After testing and verification, the catalyst ligand recovery rate of this invention, which is ultimately separated and recycled back to the production unit, exceeds 95%. The dinitrile recovery rate, separated and recovered to the production unit by the scraped-film evaporation method, is higher than 90%. The recycling of the extraction solvent cyclohexane ensures that the loss rate of cyclohexane in the entire system is no more than 1.5%. Attached Figure Description

[0043] Figure 1 This is a schematic diagram of the separation and recovery system of the present invention.

[0044] Explanation of markings in the diagram: 1-Extraction tower; 2- Solvent recovery primary flash tank heater; 3- Solvent recovery primary flash tank; 4- Secondary flash tank for solvent recovery; 5-Ligand cooler for recovery; 6-Flash tank heater for recovering residual solvent; 7-Flash evaporator for recovering residual solvents; 8- Waste liquid flash tank; 9- Waste liquid recovery scraped film evaporator; 10- Waste liquid recovery scraped film condenser; 11- Solvent recovery primary flash tank top condenser; 12- Solvent recovery secondary flash tank top condenser; 13- Solvent recovery vacuum system; 14-Vacuum exhaust gas condenser; 15-Scrap film recovery vacuum system. Detailed Implementation

[0045] The present invention will now be described in detail with reference to the accompanying drawings and specific embodiments. These embodiments are based on the technical solution of the present invention and provide detailed implementation methods and specific operating procedures. However, the scope of protection of the present invention is not limited to the following embodiments.

[0046] In this invention, it should be noted that the terms "center," "upper," "lower," "left," "right," "vertical," "horizontal," "inner," and "outer," etc., indicating orientation or positional relationships, are based on the orientation or positional relationships shown in the accompanying drawings and are only for the convenience of describing the invention and simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation, or be constructed and operated in a specific orientation, and therefore should not be construed as a limitation of the invention; the terms "first," "second," and "third" are used for descriptive purposes only and should not be construed as indicating or implying relative importance; furthermore, unless otherwise explicitly specified and limited, the terms "installed," "connected," and "linked" should be interpreted broadly, for example, they can be fixed connections, detachable connections, or integral connections; they can be mechanical connections or electrical connections; they can be direct connections or indirect connections through an intermediate medium; they can be internal connections between two elements. Those skilled in the art can understand the specific meaning of the above terms in this invention according to the specific circumstances.

[0047] It should be noted that similar labels and letters in the following figures indicate similar items. Therefore, once an item is defined in one figure, it does not need to be further defined and explained in subsequent figures.

[0048] Unless otherwise specified, the reagents, methods, instruments, and equipment used in this invention are conventional in the art. Unless otherwise specified, the reagents and materials used in the following examples are all commercially available.

[0049] This invention utilizes the hydrocyanation reaction of 1,3-butadiene (BD) in the presence of various phosphorus-containing transition metal complexes to prepare adiponitrile. The specific preparation method is as follows: In the presence of a catalyst, 1,3-butadiene (BD) reacts with hydrogen cyanide (HCN) via hydrocyanation to produce 3-pentenonitrile (3PN) and methylglutaronitrile (MGN) as byproducts. This process is a primary cyanation reaction, and the catalyst used in this process is referred to as the primary cyanation catalyst in this paper. The effluent from the primary cyanation reaction is separated using a specific method to obtain a 3PN-rich stream, a catalyst-rich stream, and an MGN-rich stream, respectively, allowing for the recycling of the primary cyanation catalyst.

[0050] 3-Pentenonitrile (3PN) can be generated through the following reaction: .

[0051] As used in this paper, BD stands for 1,3-butadiene, HCN for hydrogen cyanide, 3PN for 3-pentenonitrile, 2M3BN for 2-methyl-3-butenonitrile, 2PN for 2-pentenonitrile, and 4PN for 4-pentenonitrile. To improve the yield of 3PN in the primary cyanidation reaction, 2M3BN was catalytically isomerized to 3PN in the presence of a nickel-based ligand. This process is referred to as the isomerization reaction, and the catalyst used in this process is referred to as the isomerization catalyst in this paper. The reaction effluent was separated in a specific manner to obtain a 3PN- and MGN-rich stream and a catalyst-rich stream, allowing for the recycling of the isomerization catalyst.

[0052] In the presence of transition metal complexes containing various phosphorus-containing ligands, 3PN and 2M3PN can generate dinitrile compounds such as adiponitrile (ADN), methylglutaronitrile (MGN), and ethylbutadionitrile (ESN) through a secondary cyanidation reaction, as shown in reaction formulas 3 and 4 below. This reaction unit is referred to as the secondary cyanidation unit, and the catalyst flowing through this unit is referred to as the secondary cyanidation catalyst in this paper.

[0053] .

[0054] Therefore, the integrated process for preparing adiponitrile from 1,3-butadiene and hydrogen cyanide involved in this invention includes: a primary cyanidation reaction of 1,3-butadiene, isomerization of 2-methyl-3-butenonitrile to generate 3PN, and secondary cyanidation of 3PN and other pentenonitriles to generate adiponitrile and other dinitrile compounds. The primary cyanidation catalyst and the isomerization catalyst can be prepared using zero-valent nickel and the same phosphorus-containing ligand, but the secondary cyanidation reaction requires at least one zero-valent nickel catalyst and a Lewis acid co-catalyst to prepare adiponitrile and other dinitrile compounds at an industrially acceptable rate and yield. 3-Pentenonitrile and 2-methyl-3-butenonitrile can be separated from the catalyst through specific operations, and the separated catalyst can be recycled.

[0055] In contrast, dinitrile compounds are more difficult to separate from the catalyst. In high-concentration dinitrile solutions, the thermal stability of the catalyst decreases, and the nickel-ligand complex in the catalyst may undergo thermal degradation, releasing free ligands and uncoordinated nickel. If the Lewis acid co-catalyst is entrained into the primary cyanation reaction zone or the isomerization reaction zone, 2-methyl-3-butenonitrile (2M3BN) will undergo undesirable isomerization under the action of the Lewis acid co-catalyst, generating 2-methyl-2-butenonitrile (2M2BN). Therefore, the recovered ligands in this invention are only recycled to the secondary cyanation catalytic reaction zone.

[0056] Example 1: This embodiment first provides a catalyst separation and recovery system in the butadiene-to-adiponitrile process. The separation and recovery system includes an extraction tower 1, a primary flash tank heater for solvent recovery 2, a primary flash tank for solvent recovery 3, a secondary flash tank for solvent recovery 4, a ligand cooler 5, a flash tank heater for raffinate phase solvent recovery 6 and a flash tank for raffinate phase solvent recovery 7, a waste liquid flash tank 8, a waste liquid scraped film evaporator 9, and a waste liquid scraped film condenser 10.

[0057] The solvent recovery primary flash tank heater 2, solvent recovery primary flash tank 3, solvent recovery secondary flash tank 4, and ligand recovery cooler 5 constitute the ligand and cyclohexane recovery route. The raffinate phase solvent recovery flash tank heater 6, raffinate phase solvent recovery flash tank 7, waste liquid flash tank 8, waste liquid recovery scraped film evaporator 9, and waste liquid recovery scraped film condenser 10 constitute the dinitrile recovery route.

[0058] In this embodiment, extraction tower 1 is used to mix a catalyst-rich stream containing recovered catalysts (including primary cyanation catalysts, isomerization catalysts, and secondary cyanation catalysts), ligands, and dinitrile compounds (including adiponitrile and its isomers) with the extractant cyclohexane for extraction. The ligands to be recovered enter the cyclohexane extraction phase and are fed into the subsequent cyclohexane recovery route, while the residual dinitrile compounds in the raffinate waste liquid are fed into the subsequent dinitrile recovery route.

[0059] Since the catalyst solution requiring regeneration consists of undeactivated catalyst, poisoned catalyst, catalyst ligands, adiponitrile, methylglutaronitrile, 3-pentenonitrile, and a small amount of other impurities, the purpose of liquid-liquid extraction in this embodiment is to separate the poisoned catalyst, which is insoluble in the solvent, from the catalyst solution. The catalyst solution requiring regeneration (i.e., the heavy phase) is fed into the upper feed inlet of extraction column 1, while cyclohexane (i.e., the light phase) is fed into the lower feed inlet of extraction column 1. The undeactivated catalyst and most of the ligands dissolve in cyclohexane and enter the extraction phase, flowing out from the top of the column; the poisoned catalyst, etc., are insoluble in cyclohexane and enter the raffinate phase, flowing out from the bottom of the column.

[0060] In this embodiment, the solvent recovery primary flash tank heater 2 is connected to the extract phase outlet at the top of the extraction tower 1 to receive and heat the extract phase containing cyclohexane. The solvent recovery primary flash tank 3 is connected to the solvent recovery primary flash tank heater 2 for primary flash evaporation of the extract phase. The solvent recovery secondary flash tank 4 is connected to the liquid phase outlet at the bottom of the solvent recovery primary flash tank 3 for secondary flash evaporation of the heavy phase after primary flash evaporation. The ligand recovery cooler 5 is connected to the liquid phase outlet at the bottom of the solvent recovery secondary flash tank 4 for recovering the catalyst ligands obtained after secondary flash evaporation. The cyclohexane obtained after primary and secondary flash evaporation can be recycled after cooling.

[0061] In this embodiment, the raffinate solvent recovery flash evaporator heater 6 is connected to the raffinate outlet at the bottom of the extraction tower 1 for heating the raffinate phase. The raffinate solvent recovery flash evaporator 7 is connected to the raffinate solvent recovery flash evaporator heater 6 for flash separation of the heated raffinate phase. The waste liquid flash evaporator 8 is connected to the waste liquid outlet at the bottom of the raffinate solvent recovery flash evaporator 7 for secondary flash evaporation to initially separate dinitrile compounds. The waste liquid recovery scraped film evaporator 9 is connected to the heavy phase outlet at the bottom of the waste liquid flash evaporator 8 for further separation of dinitrile compounds and poisoned catalyst. The waste liquid recovery scraped film condenser 10 is connected to the top outlet of the waste liquid recovery scraped film evaporator 9 for cooling and recovering the dinitrile compounds obtained by scraped film evaporation.

[0062] Based on the above separation and recovery system, this embodiment also provides a method for separating and recovering the catalyst in the butadiene-to-adiponitrile process, which specifically includes the following steps: I. Extraction: A catalyst-rich stream containing recovered catalysts (including primary cyanation catalysts, isomerization catalysts, and secondary cyanation catalysts), ligands, and dinitrile compounds is fed into extraction column 1, and solvent extraction is performed using cyclohexane as the extractant.

[0063] II. Recovery of ligands and cyclohexane via two-stage flash evaporation separation: The upper extract phase after extraction is heated by heater 2 in the solvent recovery primary flash tank and then fed into solvent recovery primary flash tank 3. The cyclohexane extracted in the primary flash is recovered after cooling. The heavy phase after primary flash is fed into solvent recovery secondary flash tank 4 for stripping and secondary flash. The cyclohexane extracted in the secondary flash is recovered after cooling, and the heavy phase from the secondary flash is cooled by ligand recovery cooler 5 for ligand recovery.

[0064] III. Recovery of dinitrile compounds: The lower raffinate phase after extraction is fed into the raffinate solvent recovery flash tank heater 6, and after heating, it is sent to the raffinate solvent recovery flash tank 7. The residual cyclohexane in the raffinate phase is carried out from the top of the tank with the gas phase and recovered after condensation. The waste liquid at the bottom of the raffinate solvent recovery flash tank 7 is sent to the waste liquid flash tank 8. The light phase at the top of the tank is fed into the waste liquid recovery scraped film condenser 10 to recover dinitrile compounds. The heavy phase at the bottom of the tank flows into the waste liquid recovery scraped film evaporator 9. The evaporated dinitrile is fed into the waste liquid recovery scraped film condenser 10 to recover dinitrile compounds. The poisoned catalyst waste liquid flows out from the bottom of the waste liquid recovery scraped film evaporator 9.

[0065] Example 2: This embodiment provides a catalyst separation and recovery system and method for the butadiene-to-adiponitrile synthesis process, suitable for the recycling and recovery of catalyst ligands and the target product adiponitrile in the catalyst-rich circulating stream of the butadiene-to-adiponitrile synthesis process. The application of this catalyst separation and recovery system can reduce the consumption of ligand raw materials in the entire process unit and improve the yield of the target product adiponitrile.

[0066] Specifically, the separation and recovery system of this embodiment includes an extraction tower 1, a primary flash tank heater for solvent recovery 2, a primary flash tank for solvent recovery 3, a secondary flash tank for solvent recovery 4, a ligand cooler 5, a flash tank heater for raffinate phase solvent recovery 6 and a flash tank for raffinate phase solvent recovery 7, a waste liquid flash tank 8, a waste liquid recovery scraped film evaporator 9, a waste liquid recovery scraped film condenser 10, a top condenser of the primary flash tank for solvent recovery 11, a top condenser of the secondary flash tank for solvent recovery 12, a solvent recovery vacuum system 13, a vacuum exhaust gas condenser 14, and a scraped film recovery vacuum system 15.

[0067] In this embodiment, the solvent recovery primary flash tank heater 2 is connected to the extraction phase outlet at the top of the extraction tower 1. The solvent recovery primary flash tank 3 is connected to the solvent recovery primary flash tank heater 2. The solvent recovery secondary flash tank 4 is connected to the liquid phase outlet at the bottom of the solvent recovery primary flash tank 3. The ligand recovery cooler 5 is connected to the liquid phase outlet at the bottom of the solvent recovery secondary flash tank 4 and is used to recover the catalyst ligands obtained after secondary flash evaporation. The top outlet of the solvent recovery primary flash tank heater 2 is connected to the top condenser 11 of the solvent recovery primary flash tank and is used to recover the cyclohexane separated after primary flash evaporation. The top outlet of the solvent recovery secondary flash tank 4 is connected to the top condenser 12 of the solvent recovery secondary flash tank and is used to recover the residual cyclohexane separated after secondary flash evaporation. The non-condensable gas outlet of the top condenser 11 of the solvent recovery primary flash tank and the gas phase outlet at the top of the raffinate solvent recovery flash tank 7 are both connected to the inlet of the top condenser 12 of the solvent recovery secondary flash tank. The outlet of the top condenser 12 of the solvent recovery secondary flash tank is connected to the solvent recovery vacuum system 13, and the exhaust gas outlet of the solvent recovery vacuum system 13 is connected to the vacuum exhaust gas condenser 14 for the recovery of cyclohexane.

[0068] In this embodiment, the raffinate phase solvent recovery flash evaporator heater 6 is connected to the raffinate phase outlet at the bottom of the extraction tower 1, and the raffinate phase solvent recovery flash evaporator 7 is connected to the raffinate phase solvent recovery flash evaporator heater 6, used for flash separation of the heated raffinate phase. The waste liquid flash evaporator 8 is connected to the waste liquid outlet at the bottom of the raffinate phase solvent recovery flash evaporator 7, used for secondary flash evaporation to initially separate dinitrile compounds. The waste liquid recovery scraped-film evaporator 9 is connected to the heavy phase outlet at the bottom of the waste liquid flash evaporator 8, used for separating dinitrile compounds and catalyst waste liquid. The waste liquid recovery scraped-film condenser 10 is connected to the top outlet of the waste liquid recovery scraped-film evaporator 9, used for cooling and recovering the dinitrile obtained from the scraped-film evaporation. Furthermore, the top light phase outlet of the waste liquid flash evaporator 8 is connected to the waste liquid recovery scraped-film condenser 10, used for recovering the dinitrile obtained from the initial flash separation. The non-condensable gas outlet of the waste liquid recovery scraped-film condenser 10 is connected to the scraped-film recovery vacuum system 15.

[0069] Based on the above separation and recovery system, this embodiment provides a method for separating and recovering the catalyst in the butadiene-to-adiponitrile process, which specifically includes the following steps: I. Extraction: A catalyst-rich stream containing recovered catalysts (including primary cyanation catalysts, isomerization catalysts, and secondary cyanation catalysts), ligands, and dinitrile compounds is fed into extraction column 1, and solvent extraction is performed using cyclohexane as the extractant.

[0070] Since dinitrile compounds have similar boiling points to the catalyst system, and both have relatively high boiling points, they are difficult to separate using atmospheric distillation. Therefore, this embodiment uses cyclohexane for liquid-liquid extraction of the catalyst-rich stream. Furthermore, since the catalyst solution requiring regeneration consists of undeactivated catalyst, poisoned catalyst, catalyst ligands, adiponitrile, methylglutaronitrile, 3-pentenonitrile, and small amounts of other impurities, the purpose of liquid-liquid extraction in this embodiment is to separate the poisoned catalyst, which is insoluble in the solvent. The catalyst solution requiring regeneration (i.e., the heavy phase) is fed into the upper feed inlet of extraction column 1, while cyclohexane (i.e., the light phase) is fed into the lower feed inlet of extraction column 1. The undeactivated catalyst and most of the ligands dissolve in cyclohexane and enter the extraction phase, flowing out from the top of the column; the poisoned catalyst, etc., being insoluble in cyclohexane, enter the raffinate phase and flow out from the bottom of the column.

[0071] In this embodiment, the pressure range at the top of extraction column 1 is 0~50 kPa, the temperature range at the top of extraction column 1 is 80~85℃, and the temperature range at the bottom of extraction column 1 is 85~90℃. The feed volume ratio of the recovered catalyst to cyclohexane is 1:(1.5~2).

[0072] In this embodiment, a rotary disc extraction tower with 40-42 disc layers is selected as the extraction equipment. The rotation of the discs breaks the dispersed phase into fine droplets, increasing the contact area between the two phases. Simultaneously, fixed baffles suppress axial backmixing, prolonging the contact time between the two phases and improving mass transfer efficiency. The tower is divided into upper and lower sections. The upper section uses a large-diameter, short-path design to prevent flooding, while the lower section uses a small-diameter, long-path design to avoid droplet aggregation.

[0073] II. Recovery of ligands and cyclohexane via two-stage flash evaporation separation: The upper extract phase after extraction is heated by heater 2 in the solvent recovery primary flash tank and then fed into solvent recovery primary flash tank 3. The cyclohexane extracted in the primary flash is cooled by condenser 11 at the top of the solvent recovery primary flash tank and then recovered. The heavy phase after primary flash is further fed into solvent recovery secondary flash tank 4 for stripping secondary flash. The cyclohexane extracted in the secondary flash is cooled by condenser 12 at the top of the solvent recovery secondary flash tank and then recovered. The heavy phase from the secondary flash is cooled by ligand recovery cooler 5 and then the ligands are recovered.

[0074] In this embodiment, the outlet temperature of the solvent recovery primary flash tank heater 2 is controlled at 110~130 ℃.

[0075] In this embodiment, the pressure of the primary flash tank 3 for solvent recovery is controlled at 60~65 kPa, and the temperature inside the tank is controlled at 108~128 ℃.

[0076] In this embodiment, the pressure of the secondary flash tank 4 for solvent recovery is controlled at 25~35 kPa, the stripping gas in the tank is nitrogen at 0.2~0.4 MPa, and the mass ratio of stripping nitrogen to feed stream is 1: (5~10).

[0077] III. Recovery of dinitrile compounds: The lower raffinate phase after extraction is fed into the raffinate solvent recovery flash tank heater 6, and after heating, it is sent to the raffinate solvent recovery flash tank 7. Residual cyclohexane in the raffinate phase is carried out from the top of the tank with the gas phase and fed into the top condenser 12 of the solvent recovery secondary flash tank for condensation and recovery. The waste liquid at the bottom of the raffinate solvent recovery flash tank 7 is sent to the waste liquid flash tank 8. The light phase at the top of the tank is a dinitrile-rich stream, which is fed into the waste liquid recovery scraped film condenser 10 for the recovery of dinitrile compounds. The heavy phase at the bottom of the tank flows into the waste liquid recovery scraped film evaporator 9, and the evaporated dinitrile is fed into the waste liquid recovery scraped film condenser 10 for the recovery of dinitrile compounds. The catalyst waste liquid flows out from the bottom of the waste liquid recovery scraped film evaporator 9.

[0078] In this embodiment, the outlet temperature of the flash evaporator heater 6 for recovering residual solvent is controlled at 150~160 ℃.

[0079] In this embodiment, the pressure of the flash evaporator 7 for recovering residual solvent is controlled at 70~75 kPa, and the temperature inside the evaporator is controlled at 148~158 ℃. The stripping gas inside the flash evaporator 7 is nitrogen gas at 0.2~0.4 MPa, and the mass ratio of stripping nitrogen gas to feed stream is 1:(5~10).

[0080] In this embodiment, the pressure inside the waste liquid flash evaporator 8 is controlled at 50~60 kPa, and the temperature inside the tank is controlled at 145~155℃.

[0081] In this embodiment, the pressure inside the waste liquid recovery scraped film evaporator 9 is controlled at 10~20 kPa, and the temperature is controlled at 180~210 ℃. The rotation speed of the waste liquid recovery scraped film evaporator 9 is controlled at 40~80 rpm. Considering the high viscosity characteristics of the waste liquid system and the heat sensitivity of adiponitrile, this embodiment uses scraped film evaporation technology to separate the waste liquid. The characteristic is that a uniform liquid film is formed on the heated wall by a rotating scraper, and gentle evaporation is achieved by combining high vacuum and low residence time.

[0082] In this embodiment, the cyclohexane extracted from the first-stage flash evaporation is fed into the top condenser 11 of the solvent recovery first-stage flash evaporation tank, and the outlet temperature of the top condenser 11 of the solvent recovery first-stage flash evaporation tank is controlled at 40~60 ℃.

[0083] In this embodiment, the cyclohexane extracted from the secondary flash vapor is fed into the top condenser 12 of the solvent recovery secondary flash tank, and the outlet temperature of the top condenser 12 is controlled at 20~30 ℃. To further improve the cyclohexane recovery rate and reduce solvent consumption in the liquid-liquid extraction method, the condensate output from the top condenser 12 of the solvent recovery secondary flash tank is further fed into the solvent recovery vacuum system 13, and the working fluid of the solvent recovery vacuum system 13 is cyclohexane.

[0084] In this embodiment, the vacuum exhaust gas generated by the solvent recovery vacuum system 13 is input into the vacuum exhaust gas condenser 14, and the outlet temperature of the vacuum exhaust gas condenser 14 is controlled at 10~20 ℃.

[0085] Based on the separation and recovery system and method of this embodiment, the catalyst ligand recovery rate of the recovered catalyst stream, which is ultimately separated and recycled to the production unit by liquid-liquid extraction, exceeds 95%; the dionitrile recovery rate of the dionitrile separated and recycled to the production unit by scraped film evaporation is higher than 90%. In this invention, the extraction solvent cyclohexane is recycled, and the loss rate of cyclohexane in the entire system is no more than 1.5%.

[0086] The above description of the embodiments is provided to enable those skilled in the art to understand and use the invention. It will be apparent to those skilled in the art that various modifications can be made to these embodiments, and the general principles described herein can be applied to other embodiments without inventive effort. Therefore, the present invention is not limited to the above embodiments, and any improvements and modifications made by those skilled in the art based on the disclosure of the present invention without departing from the scope of the invention should be within the protection scope of the present invention.

Claims

1. A catalyst separation and recovery system in the butadiene-to-adiponitrile process, characterized in that, The separation and recovery system is used to achieve the effective separation and recovery of poisoned catalysts, catalyst ligands and dinitrile compounds in the butadiene-to-adiponitrile synthesis process. The separation and recovery system includes: An extraction tower (1) is used to extract cyclohexane by mixing a catalyst-rich stream containing recovered catalyst, catalyst ligand and dinitrile compound with cyclohexane; the recovered catalyst includes a primary cyanidation catalyst, an isomerization catalyst and a secondary cyanidation catalyst. The solvent recovery first-stage flash tank heater (2) is connected to the extraction phase outlet at the top of the extraction tower (1); the top outlet of the solvent recovery first-stage flash tank heater (2) is connected to the top condenser (11) of the solvent recovery first-stage flash tank for recovering cyclohexane separated after the first-stage flash evaporation. The solvent recovery primary flash tank (3) is connected to the solvent recovery primary flash tank heater (2); The solvent recovery secondary flash tank (4) is connected to the liquid phase outlet at the bottom of the solvent recovery primary flash tank (3); the top outlet of the solvent recovery secondary flash tank (4) is connected to the top condenser (12) of the solvent recovery secondary flash tank, which is used to recover the residual cyclohexane separated after secondary flash evaporation; The ligand recovery cooler (5) is connected to the liquid phase outlet at the bottom of the solvent recovery secondary flash tank (4) and is used to recover the catalyst ligands obtained after secondary flash evaporation. The raffinate solvent recovery flash tank heater (6) is connected to the raffinate outlet at the bottom of the extraction tower (1); The flash evaporator (7) for recovering residual solvent is connected to the heater (6) for recovering residual solvent. Waste liquid flash tank (8) is connected to the waste liquid outlet at the bottom of the raffinate solvent recovery flash tank (7) for the preliminary separation of dinitrile compounds and poisoned catalyst; The waste liquid recovery scraped film evaporator (9) is connected to the heavy phase outlet at the bottom of the waste liquid flash tank (8) for further separation of dinitrile compounds and poisoned catalyst; Waste liquid recovery scraped film condenser (10), connected to the top outlet of waste liquid recovery scraped film evaporator (9), is used to cool and recover dinitrile compounds.

2. The catalyst separation and recovery system in the butadiene-to-adiponitrile process according to claim 1, characterized in that, The non-condensable gas material outlet of the top condenser (11) of the solvent recovery primary flash tank and the gas phase outlet of the top of the solvent recovery flash tank (7) are both connected to the inlet of the top condenser (12) of the solvent recovery secondary flash tank. The outlet of the top condenser (12) of the solvent recovery secondary flash tank is connected to the solvent recovery vacuum system (13); The exhaust gas outlet of the solvent recovery vacuum system (13) is connected to the vacuum exhaust gas condenser (14) for the recovery of cyclohexane.

3. The catalyst separation and recovery system in the butadiene-to-adiponitrile process according to claim 1, characterized in that, The top light phase outlet of the waste liquid flash evaporator (8) is connected to the waste liquid recovery scraped film condenser (10) for recovering the dinitrile obtained from the initial flash separation; The non-condensable gas outlet of the waste liquid recovery scraped film condenser (10) is connected to the scraped film recovery vacuum system (15).

4. A method for separating and recovering catalysts in a butadiene-to-adiponitrile process, characterized in that, Based on the separation and recovery system according to any one of claims 1-3, the specific steps include: I. Extraction: A catalyst-rich stream containing recovered catalyst, catalyst ligand and dinitrile compound is fed into the extraction column (1) for solvent extraction using cyclohexane; II. Recovery of ligands and cyclohexane: The upper extract phase after extraction is heated by the solvent recovery primary flash tank heater (2) and then fed into the solvent recovery primary flash tank (3). The cyclohexane extracted by the primary flash is recovered after cooling. The heavy phase after the primary flash is fed into the solvent recovery secondary flash tank (4) for stripping and secondary flash. The cyclohexane extracted by the secondary flash is recovered after cooling. The heavy phase from the secondary flash is cooled by the ligand recovery cooler (5) and the ligands are recovered. III. Recovery of dinitrile compounds: The lower raffinate phase after extraction is fed into the raffinate phase solvent recovery flash tank heater (6), and after heating, it is sent into the raffinate phase solvent recovery flash tank (7). The residual cyclohexane in the raffinate phase is carried out from the top of the tank with the gas phase and recovered after condensation. The waste liquid at the bottom of the raffinate phase solvent recovery flash tank (7) is sent into the waste liquid flash tank (8). The light phase at the top of the tank is fed into the waste liquid recovery scraped film condenser (10) to recover dinitrile compounds. The heavy phase at the bottom of the tank flows into the waste liquid recovery scraped film evaporator (9). The evaporated dinitrile is fed into the waste liquid recovery scraped film condenser (10) to recover dinitrile compounds. The poisoned catalyst waste liquid flows out from the bottom of the waste liquid recovery scraped film evaporator (9).

5. The method for separating and recovering the catalyst in the butadiene-to-adiponitrile process according to claim 4, characterized in that, The pressure range at the top of the extraction tower (1) is 0~50 kPa, the temperature range at the top is 80~85℃, and the temperature range at the bottom is 85~90℃. The extraction tower (1) is a rotary extraction tower with 40 to 42 rotary layers; The feed volume ratio of the recovered catalyst to cyclohexane is 1:(1.5~2).

6. The method for separating and recovering the catalyst in the butadiene-to-adiponitrile process according to claim 4, characterized in that, The outlet temperature range of the solvent recovery primary flash tank heater (2) is 110~130 ℃; The pressure range of the solvent recovery primary flash tank (3) is 60~65 kPa, and the temperature range inside the tank is 108~128 ℃; The pressure range of the secondary flash tank (4) for solvent recovery is 25~35 kPa, the stripping gas in the tank is nitrogen gas at 0.2~0.4 MPa, and the mass ratio of stripping nitrogen gas to feed stream is 1: (5~10).

7. The method for separating and recovering the catalyst in the butadiene-to-adiponitrile process according to claim 4, characterized in that, The outlet temperature range of the flash tank heater (6) for recovering residual solvent is 150~160 ℃; The pressure range of the flash evaporator (7) for recovering residual solvent is 70~75 kPa, the temperature range inside the tank is 148~158℃, the stripping gas inside the tank is nitrogen gas at 0.2~0.4 MPa, and the mass ratio of stripping nitrogen gas to feed stream is 1: (5~10). The internal pressure range of the waste liquid flash tank (8) is 50~60 kPa, and the internal temperature range is 145~155 ℃.

8. The method for separating and recovering the catalyst in the butadiene-to-adiponitrile process according to claim 4, characterized in that, The pressure range of the waste liquid recovery scraped film evaporator (9) is 10~20 kPa, the temperature range is 180~210℃, and the rotation speed is 40~80 rpm.

9. The method for separating and recovering the catalyst in the butadiene-to-adiponitrile process according to claim 4, characterized in that, The cyclohexane extracted from the first-stage flash evaporation is fed into the top condenser (11) of the solvent recovery first-stage flash evaporation tank, and the outlet temperature of the top condenser (11) of the solvent recovery first-stage flash evaporation tank is 40~60 ℃; The cyclohexane extracted from the secondary flash vapor is fed into the top condenser (12) of the solvent recovery secondary flash tank, and the outlet temperature of the top condenser (12) of the solvent recovery secondary flash tank is 20~30 ℃; The condensate output from the top condenser (12) of the solvent recovery secondary flash tank is further fed into the solvent recovery vacuum system (13), and the working fluid of the solvent recovery vacuum system (13) is cyclohexane; The vacuum exhaust gas generated by the solvent recovery vacuum system (13) is input into the vacuum exhaust gas condenser (14), and the outlet temperature of the vacuum exhaust gas condenser (14) is 10~20 ℃.

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