Method for producing poly (butylene succinate) material by using single raw material maleic anhydride

Abstract

The invention discloses a method for producing a poly (butylene succinate) (PBSX) material by using a single raw material maleic anhydride, which comprises the following three steps of: preparing succinic anhydride (SAA) by hydrogenation of maleic anhydride, preparing 1, 4-butanediol (BDO) by hydrogenation of SAA, and preparing PBSX by ring-opening polycondensation of SAA and BDO or by ring-opening polycondensation of SAA and BDO and a third monomer. Wherein the third monomer is selected from at least one of polybasic acid and ester, cyclic anhydride, polyhydric alcohol, cyclic ether, hydroxy acid and ester or lactone. According to the invention, the PBSX is prepared from maleic anhydride through a three-step cascade reaction, so that the link of preparing succinic acid or succinic acid diester in the traditional esterification method or ester exchange method is simplified; the two-step hydrogenation reaction is a high-selectivity process, and used solvents are substances in the system; a small amount of by-products generated in the hydrogenation or polycondensation process can be used as monomers. The method provided by the invention is simple in overall process, low in production cost and good in economic benefit.

Description

Technical Field

[0001] The present invention relates to the technical fields of polyester monomer synthesis and polymer preparation. Specifically, it is a method for producing polybutylene succinate materials using maleic anhydride as a single raw material. Background Art

[0002] With the gradual enhancement of people's awareness of green ecology and environmental protection, people are more pursuing green carbon, low-carbon, and zero-carbon economies as well as the development path of green chemistry, and have higher requirements for the atomic economy of chemical processes, demanding the use of raw material resources with high atomic utilization rates. Therefore, synthesizing monomer raw materials and polymer materials through green and efficient raw material routes has become the research direction of scientific research and industrial production in the fields of fine chemistry and new chemical materials; replacing traditional plastics such as polyolefins PP, PE, PS, PVC, etc. and polyesters PET, polyurethane PU, etc. with biodegradable plastics such as polylactic acid (PLA), polybutylene succinate (PBS), etc. has become an inevitable trend in future social development. In various industries related to national economy and people's livelihood, especially in modern agriculture and daily life, the potential demand for biodegradable plastics is huge. Polybutylene succinate materials (PBSX), as one of the varieties with excellent comprehensive properties among biodegradable plastics, have an increasing demand. Therefore, it is imperative to develop a large-scale continuous production technology for PBSX with sufficient raw material sources and supplies, a green and environmentally friendly synthesis route, a short and efficient process flow, low production costs, and high product quality.

[0003] Traditional PBSX synthesis methods mainly include direct esterification and transesterification. The direct esterification method uses succinic acid and 1,4-butanediol as the main monomer raw materials. With or without the addition of a third monomer such as adipic acid, terephthalic acid, or polyol, PBSX (including PBS, PBSA, PBST, or MPBS, etc.) is obtained through esterification and polycondensation. However, this method has problems such as low esterification reaction rate, incomplete reaction of acidic monomers such as succinic acid, a large amount of by-products such as tetrahydrofuran and / or enol generated by the cycloetherification and / or enolization of alcohol monomers such as 1,4-butanediol, and a large amount of wastewater generated during the esterification-polycondensation reaction, resulting in low raw material utilization rate, high raw material consumption and energy consumption, low product yield, and high wastewater treatment cost, which increases the production cost of PBSX. The transesterification method uses a diester of succinic acid such as dimethyl ester and 1,4-butanediol as the main monomer raw materials, and synthesizes PBSX through transesterification and polycondensation reactions with or without the participation of a third monomer. Since one of the monomer raw materials in the transesterification method is a diester of succinic acid, the diester of succinic acid needs to be synthesized first, and a large amount of small molecules such as methanol are generated during the transesterification process. Compared with the direct esterification method, its synthesis route is longer, the raw material utilization rate is lower, and the raw material consumption, energy consumption, and production cost are higher.

[0004] The recently reported ring-opening polycondensation method, namely the ring-opening polycondensation of succinic anhydride with 1,4-butanediol or / and tetrahydrofuran and a third monomer to synthesize PBSX, such as in invention patents CN114015026B and CN113980252B. Since it does not require the succinic acid monomer of the esterification method or the succinic acid ester monomer of the transesterification method, but uses succinic anhydride prepared by the one-step high-selectivity hydrogenation of maleic anhydride as the monomer, it shortens the monomer preparation process and reduces the monomer manufacturing cost. Moreover, the generation amount of small-molecule substances (water or alcohol) during the polymerization process is at least reduced by half, and the monomer raw material consumption is low. The PBSX product obtained by ring-opening polymerization has a high molecular weight and good thermal and mechanical properties, and the quality is better. Obviously, the method of synthesizing PBSX by the ring-opening polycondensation of succinic anhydride and 1,4-butanediol has been greatly improved in both product performance and production cost compared with the succinic acid esterification polycondensation method and the succinic acid ester transesterification polycondensation method.

[0005] At present, as a biodegradable plastic, the excellent properties of PBSX have been widely recognized. However, due to its production cost and selling price still being much higher than traditional plastics such as PP and PE, there are still obstacles to large-scale promotion and application, and the market acceptance is still low. Reducing the manufacturing cost of PBSX has become a decisive factor for its replacement of traditional plastics and realization of large-scale production and application. Individually improving and optimizing the PBSX polymerization process has limited room for reducing its manufacturing cost, such as the succinic acid esterification method and the succinic acid ester transesterification method for synthesizing PBSX; individually changing the raw material path, such as the succinic anhydride ring-opening method, although it has greatly reduced the manufacturing cost of PBSX, it is still much higher than the manufacturing cost of plastics such as PP. In order to further reduce the comprehensive manufacturing cost of PBSX, it is necessary to reduce the manufacturing cost of monomer raw materials. For this purpose, integrated innovation is required throughout the process from monomer manufacturing to material manufacturing, that is, overall process innovation. Therefore, succinic anhydride and 1,4-butanediol, as two key monomers for synthesizing PBSX by the ring-opening polymerization method, are of great significance for realizing its green, efficient, and low-cost preparation, and for preparing high-quality PBSX cleanly, efficiently, and low-cost by the ring-opening polymerization method, and at the same time integrating the overall process of synthesizing PBSX with maleic anhydride as the starting material to minimize the manufacturing cost of PBSX.

[0006] Regarding the overall process of synthesizing PBSX with maleic anhydride as the raw material, there are the following several combined paths in the prior art:

[0007] 1) A 3-7-step process for synthesizing PBS by the esterification polycondensation of maleic anhydride via succinic acid and 1,4-butanediol:

[0008] D1. Process for synthesizing PBS from maleic anhydride through three steps of two - step hydrogenation and esterification polycondensation: ① One - step aqueous - phase hydrogenation of maleic anhydride to prepare succinic acid (CN111689845B, maleic anhydride conversion rate > 99.6%, succinic acid selectivity > 99.8%); ② One - step aqueous - phase hydrogenation of succinic acid to prepare 1,4 - butanediol (CN109453763A, succinic acid conversion rate > 96%, 1,4 - butanediol selectivity > 90%); ③ Esterification polycondensation of succinic acid and 1,4 - butanediol to synthesize PBS (CN101328261A).

[0009] D2. Process for synthesizing PBS from maleic anhydride through four steps of three - step hydrogenation and esterification polycondensation: ① One - step aqueous - phase hydrogenation of maleic anhydride to prepare succinic acid (CN111689845B); ② Hydrogenation of maleic anhydride to prepare γ - butyrolactone; ③ Further hydrogenation of γ - butyrolactone to prepare 1,4 - butanediol (CN114181038B); ④ Esterification polycondensation of succinic acid and 1,4 - butanediol to synthesize PBS (CN101328261A).

[0010] D3. Process for synthesizing PBS from maleic anhydride through five steps of three - step hydrogenation, hydrolysis and esterification polycondensation: ① Hydrogenation of maleic anhydride to prepare succinic anhydride; ② Hydrolysis of succinic anhydride to prepare succinic acid (CN102311332B); ③ Hydrogenation of maleic anhydride to prepare γ - butyrolactone; ④ Further hydrogenation of γ - butyrolactone to prepare 1,4 - butanediol (CN114181038B); ⑤ Esterification polycondensation of succinic acid and 1,4 - butanediol to synthesize PBS (CN101328261A).

[0011] D4. Process for synthesizing PBS from maleic anhydride through five steps of hydrolysis, three - step hydrogenation and esterification polycondensation: ① Hydrolysis of maleic anhydride to prepare maleic acid; ② Double - bond hydrogenation of maleic acid to prepare succinic acid (CN102417445A); ③ Hydrogenation of maleic anhydride to prepare γ - butyrolactone; ④ Further hydrogenation of γ - butyrolactone to prepare 1,4 - butanediol (CN114181038B); ⑤ Esterification polycondensation of succinic acid and 1,4 - butanediol to synthesize PBS (CN101328261A).

[0012] D5. Process for synthesizing PBS from maleic anhydride through seven steps of hydrolysis, two - step esterification, three - step hydrogenation and esterification polycondensation: ① One - step aqueous - phase hydrogenation of maleic anhydride to prepare succinic acid (CN111689845B); ② - ⑥ Maleic anhydride is successively subjected to mono - esterification to prepare maleic acid mono - ester, double - esterification to prepare maleic acid di - ester, hydrogenation to prepare succinic acid di - ester, and two - step hydrogenation of succinic acid di - ester to prepare 1,4 - butanediol (co - producing γ - butyrolactone and tetrahydrofuran, CN110563933B); ⑦ Esterification polycondensation of succinic acid and 1,4 - butanediol to synthesize PBS (CN101328261A).

[0013] D6. Process for synthesizing PBS from maleic anhydride through seven steps of reaction including two-step esterification, three-step hydrogenation, hydrolysis and esterification polycondensation: ① - ⑤ Maleic anhydride is successively subjected to monoesterification to prepare maleic acid monoester, diesterification to prepare maleic acid diester, hydrogenation to prepare succinic acid diester, and two-step hydrogenation of succinic acid diester to prepare 1,4-butanediol (co-producing a large amount of γ-butyrolactone and tetrahydrofuran, CN110563933B); ⑥ Hydrolysis of succinic acid diester to prepare succinic acid (CN102746138B); ⑦ Esterification polycondensation of succinic acid and 1,4-butanediol to synthesize PBS (CN101328261A).

[0014] 2) 5 - 6-step process for synthesizing PBS from maleic anhydride via transesterification polycondensation of succinic acid ester and 1,4-butanediol:

[0015] D7. Process for synthesizing PBS from maleic anhydride through five steps of reaction including three-step hydrogenation, esterification and transesterification polycondensation (CN112694602B): ① Hydrogenation of maleic anhydride to prepare succinic anhydride, ② Esterification of succinic anhydride with methanol to prepare dimethyl succinate, ③ Hydrogenation of dimethyl succinate to prepare γ-butyrolactone, ④ Hydrogenation of γ-butyrolactone to prepare 1,4-butanediol (co-producing γ-butyrolactone and tetrahydrofuran), ⑤ Transesterification polycondensation of dimethyl succinate and 1,4-butanediol to synthesize PBS.

[0016] D8. Process for synthesizing PBS from maleic anhydride through six steps of reaction including two-step esterification, three-step hydrogenation and transesterification polycondensation (Conser process and CN113512183A): ① Successively subject maleic anhydride to monoesterification to prepare maleic acid monoester, ② Diesterification to prepare maleic acid diester, ③ Double-bond hydrogenation of maleic acid diester to prepare succinic acid diester, ④ - ⑤ Two-step hydrogenation of succinic acid diester to prepare 1,4-butanediol (co-producing γ-butyrolactone and tetrahydrofuran), ⑥ Transesterification polycondensation of succinic acid diester and 1,4-butanediol to synthesize PBS.

[0017] 3) 3-step process for synthesizing PBS from maleic anhydride via ring-opening polycondensation of succinic anhydride and 1,4-butanediol:

[0018] D9. Process for synthesizing PBS from maleic anhydride through three steps of reaction including two-step hydrogenation and ring-opening polycondensation (CN114920913B): ① Hydrogenate the tetrahydrofuran solution of maleic anhydride to generate succinic anhydride and γ-butyrolactone, and separate to obtain the tetrahydrofuran solution of γ-butyrolactone and succinic anhydride; ② Hydrogenate the tetrahydrofuran solution of γ-butyrolactone to obtain the tetrahydrofuran solution of 1,4-butanediol, and separate to obtain 1,4-butanediol and tetrahydrofuran; ③ Polymerize succinic anhydride and 1,4-butanediol to generate PBS.

[0019] It can be seen that among the 9 technical routes for synthesizing PBSX starting from maleic anhydride, except for D1 and D9 which involve 3-step reactions, the rest all have the defect of long process flows (4 - 7 steps); moreover, all 9 routes also have the following disadvantages: the selectivity for preparing monomers is low and the traditional esterification polycondensation or transesterification polycondensation process is adopted, resulting in low raw material utilization rate and high material consumption, energy consumption, and three wastes volume, which increases the manufacturing cost of PBSX.

[0020] In recent years, with the development of the technology for preparing maleic anhydride by the oxidation of n-butane, the production cost of maleic anhydride has been significantly reduced, and the processes for producing succinic anhydride and 1,4-butanediol using maleic anhydride as the raw material have also developed greatly. The catalytic hydrogenation of maleic anhydride to succinic anhydride includes gas-phase method, liquid-phase melting method, and liquid-phase solvent method. Among them, the liquid-phase solvent method for hydrogenation is the mainstream method for large-scale production of succinic anhydride globally due to its relatively mild operating conditions, relatively higher selectivity for succinic anhydride, long catalyst service life, and ease of large-scale production. Currently, the reaction temperature in the liquid-phase solvent hydrogenation method is mostly above 90°C, the space velocity is generally less than 0.1h -1 , the molar ratio of hydrogen to anhydride > 40, the reaction pressure > 3.0 MPa, and the maleic anhydride feed concentration is less than 15%. If the reaction temperature can be reduced, the selectivity for succinic anhydride will be further improved. By reducing the hydrogen-to-anhydride ratio, reaction pressure, and increasing the space velocity and maleic anhydride feed concentration, the energy consumption can be reduced, the space-time yield can be increased, which helps to further reduce the production cost of succinic anhydride and the large-scale production of production equipment.

[0021] The catalytic hydrogenation of maleic anhydride to prepare 1,4-butanediol includes two routes: esterification hydrogenation or direct hydrogenation. In the direct hydrogenation method, maleic anhydride first undergoes the first-step catalytic hydrogenation to generate tetrahydrofuran and γ-butyrolactone, and then γ-butyrolactone undergoes the second-step catalytic hydrogenation to generate 1,4-butanediol. It can be seen that the direct hydrogenation method of maleic anhydride is a co-production process for 1,4-butanediol, tetrahydrofuran, and γ-butyrolactone. Although the process flow is short, the product selectivity for 1,4-butanediol is low, the separation energy consumption is large, and the production cost is high. In the maleic anhydride esterification hydrogenation method, first, maleic anhydride reacts with a monohydric alcohol (usually methanol or ethanol) to form maleic acid diester, and then through multiple steps of catalytic hydrogenation, 1,4-butanediol is obtained, and a large amount of γ-butyrolactone and tetrahydrofuran are co-produced. Obviously, the product selectivity for 1,4-butanediol in the maleic anhydride esterification hydrogenation method is also not high, and the process route is long, requiring a lot of equipment, large investment, difficult control, and high production cost. Therefore, it is necessary to improve the technology for the hydrogenation of maleic anhydride to 1,4-butanediol, and there is still a huge room for improvement.

[0022] In order to further reduce the manufacturing cost of PBSX, technical personnel attempted to synthesize two key monomers of PBSX, succinic anhydride and 1,4-butanediol, through the co-production of maleic anhydride hydrogenation and ring-opening polycondensation. The new patent CN217248853U discloses a co-production system of succinic anhydride, γ-butyrolactone, 1,4-butanediol and tetrahydrofuran. Its primary hydrogenation reaction unit is used for the hydrogenation of maleic anhydride by the solvent method to prepare succinic anhydride, the crystallization unit is used for separating crude succinic anhydride and the solvent, the secondary hydrogenation reaction unit is used for the further hydrogenation of succinic anhydride to generate a mixed crude product of 1,4-butanediol, γ-butyrolactone and tetrahydrofuran, and the refining unit is used for the separation of the crude product. The second-step hydrogenation in this patent has low selectivity, co-produces 1,4-butanediol, γ-butyrolactone and tetrahydrofuran, has a long separation process, high energy consumption and a complex system. The invention patent CN114181038B proposes a method for directly hydrogenating maleic anhydride to produce 1,4-butanediol and co-producing succinic anhydride. 1,4-butanediol is obtained by two-step hydrogenation of maleic anhydride as the raw material; in the first-step maleic anhydride hydrogenation reactor, maleic anhydride is hydrogenated under the action of a catalyst to generate γ-butyrolactone, succinic anhydride, tetrahydrofuran and water, and at the same time a small amount of succinic anhydride is hydrolyzed to form succinic acid; then the reaction product enters the separation system, tetrahydrofuran, water and a small amount of n-butanol are separated out, succinic acid is dehydrated to form succinic anhydride, and then γ-butyrolactone and succinic anhydride products are separated; after heating, γ-butyrolactone enters the reactor for hydrogenation to generate 1,4-butanediol, and at the same time a small amount of tetrahydrofuran, n-butanol and acetal are generated, and the 1,4-butanediol product is obtained through subsequent separation. It can be seen that although this process can obtain succinic anhydride and 1,4-butanediol through two-step hydrogenation of maleic anhydride and γ-butyrolactone, there are many by-products and the separation process is complex. In particular, the co-produced succinic acid will corrode the equipment, resulting in increased investment and production costs. In fact, the so-called co-production process essentially still has poor catalyst selectivity and cannot reach the level of only generating a single product or highly selectively generating a certain product.

[0023] Patents CN112694602B and CN110563933B propose a method for producing PBS using maleic anhydride as a raw material. The method involves hydrogenating maleic anhydride to prepare succinic anhydride, and then esterifying succinic anhydride with a lower aliphatic monohydric alcohol to prepare diethyl succinate, or esterifying maleic anhydride with a lower aliphatic monohydric alcohol to prepare diethyl maleate, followed by hydrogenation to prepare diethyl succinate. Then, diethyl succinate and 1,4-butanediol are synthesized into PBS through transesterification polycondensation. However, none of these patents solve the problem of the source of 1,4-butanediol, and still need to first synthesize diethyl succinate and then carry out transesterification polycondensation, resulting in a long process flow and having the disadvantages of the aforementioned method for preparing PBS by transesterification polycondensation. CN106366297B discloses a preparation method for the overall industrial chain of polybutylene succinate. The overall reaction route is to rectify n-butane from a C4 fraction, produce liquid-phase maleic anhydride from n-butane, produce succinic anhydride using liquid-phase maleic anhydride as a raw material, carry out ring-opening esterification of succinic anhydride, 1,4-butanediol and a catalyst in a nitrogen atmosphere, and then carry out a polycondensation reaction under vacuum conditions to obtain the target product polybutylene succinate. Although this patent proposes the preparation of succinic anhydride by hydrogenating maleic anhydride from butane and the ring-opening polymerization of succinic anhydride to prepare PBS, it still does not solve the problem of the source of another key monomer, 1,4-butanediol, required for preparing PBS.

[0024] CN114920913B provides a method for catalytic conversion of maleic anhydride to prepare PBS. Maleic anhydride is dissolved in tetrahydrofuran to prepare a maleic anhydride solution, and then hydrogenated to generate succinic anhydride and γ-butyrolactone. The tetrahydrofuran solution of γ-butyrolactone and succinic anhydride are separated; the tetrahydrofuran solution of γ-butyrolactone is further hydrogenated to obtain a tetrahydrofuran solution of 1,4-butanediol, and 1,4-butanediol and tetrahydrofuran are separated; succinic anhydride and 1,4-butanediol are subjected to a polymerization reaction to generate the product PBS. However, in the first step of hydrogenation in this patent, a 6.6wt% Ni-2.3wt% Co-2.5wt% Nd2O5-1.2wt% CeO2 / 89.7wt% ZrO2 supported multi-component catalyst and a high-temperature and high-pressure (140-200°C, 3.0-5.0 MPa) reaction process for co-production of succinic anhydride and γ-butyrolactone are used, and the selectivity of the target product succinic anhydride is very low (less than 50%); in the second step of hydrogenation reaction, higher temperature and pressure (160-240°C, 4.0-7.0 MPa) are used. Since tetrahydrofuran is used as a solvent and the material balance is not provided, it is impossible to judge whether by-products are generated during the reaction. At the same time, since the hydrogenation catalyst is not given, it cannot be specifically implemented; in the third step of polymerization reaction, the mass ratio of the monomers succinic anhydride and 1,4-butanediol is 1:0.94-1.03 (converted to a molar ratio of 1:1.04-1.14), and the total mass yield of PBS in Examples 1-5 is 94.7-98.0%, which is impossible (when succinic anhydride and butanediol are polycondensed to synthesize PBS, in addition to obtaining the polyester, water and tetrahydrofuran are also generated, and the limit theoretical mass yield of PBS is only 90.5%), and the polymerization catalyst and polymerization process are not given, and it also lacks operability. Summary of the Invention

[0025] In view of the above-mentioned defects of the prior art, the present invention proposes a method for producing polybutylene succinate materials with a single raw material maleic anhydride. It uses maleic anhydride as the only starting raw material, and synthesizes two key monomers through two-step tandem highly selective hydrogenation reactions of hydrogenating maleic anhydride to prepare succinic anhydride and hydrogenating succinic anhydride to prepare 1,4-butanediol. Then, succinic anhydride and 1,4-butanediol are subjected to ring-opening polycondensation to synthesize PBS-based polyesters. Through three steps of reaction, an innovative process route and a continuous preparation method for high-quality PBSX can be obtained. It provides an overall process route and production method for green, efficient, and low-cost preparation of high-quality polybutylene succinate biodegradable materials PBSX.

[0026] The object of the present invention is achieved by the following technical solutions:

[0027] A method for producing polybutylene succinate materials with a single raw material maleic anhydride, comprising the following steps:

[0028] S1. Selective hydrogenation of maleic anhydride to prepare succinic anhydride;

[0029] S2. Part of the succinic anhydride obtained in step S1 is selectively hydrogenated to prepare 1,4-butanediol;

[0030] S3. The remaining succinic anhydride obtained in step S1, the 1,4-butanediol obtained in step S2, with or without the addition of a third monomer, are mixed and then subjected to ring-opening polycondensation to synthesize polybutylene succinate;

[0031] Among them, the catalyst used in the hydrogenation reaction in step S1 is a supported metal palladium catalyst, and the process conditions of the hydrogenation reaction are: temperature 40 - 90 °C, pressure 0.2 - 2.0 MPa, feed weight hourly space velocity is 0.1 - 2.0 h -1 , and the molar ratio of hydrogen to anhydride is 1 - 30; the catalyst used in the hydrogenation reaction in step S2 is a copper-based catalyst, and the process conditions of the hydrogenation reaction are: temperature 240 - 340 °C, pressure 2.0 - 10.0 MPa, feed weight hourly space velocity 0.1 - 5.0 h -1 and the molar ratio of hydrogen to anhydride is 20 - 200; the mass ratio of the succinic anhydride obtained in step S1 used for preparing 1,4-butanediol in step S2 and the succinic anhydride used for synthesizing polybutylene succinate in step S3 is (0.8 - 2.5):1; the third monomer is selected from at least one of polyacids and esters, cyclic anhydrides, polyols, cyclic ethers, hydroxy acids and esters, or lactones.

[0032] In the hydrogenation reaction of step S1, the molar ratio of hydrogen to anhydride is the molar ratio of hydrogen and maleic anhydride as the hydrogenation reaction raw material; in the hydrogenation reaction of step S2, the molar ratio of hydrogen to anhydride is the molar ratio of hydrogen and succinic anhydride as the hydrogenation reaction raw material.

[0033] The present invention is further configured such that in step S1, the selective hydrogenation of maleic anhydride as a raw material to prepare succinic anhydride includes the following steps:

[0034] S11. Dissolve maleic anhydride in a solvent to prepare a maleic anhydride solution as the feed, preheat it and then send it into a hydrogenation reactor for hydrogenation reaction;

[0035] S12. Carry out gas-liquid separation on the reaction product of the hydrogenation reaction, recycle the separated gaseous hydrogen to the hydrogenation reactor, and send the liquid-phase material into a separation and purification system to obtain high-purity succinic anhydride.

[0036] The present invention is further configured such that in step S11, the hydrogenation reactor uses a gas-liquid-solid slurry bed or a fixed-bed reactor, preferably a fixed-bed reactor, and more preferably a trickle fixed-bed reactor;

[0037] The catalyst in the hydrogenation reaction is selected from Pd / γ-Al2O3 or Pd-D / γ-Al2O3 catalysts, where D = Ni or / and Cu; more preferably Pd / γ-Al2O3 or Pd-Ni / γ-Al2O3 catalysts;

[0038] The present invention is further configured such that the loading amount of Pd in the Pd / γ-Al2O3 catalyst is 0.1 to 1.0 wt%; the loading amount of Pd in the Pd-Ni / γ-Al2O3 catalyst is 0.1 to 1.0 wt%, and the loading amount of Ni is 2 to 10 wt%.

[0039] The solvent of the maleic anhydride solution is γ-butyrolactone, and the mass concentration of maleic anhydride in the feed is 15 to 50%, preferably 18 to 40%, more preferably 20 to 30%;

[0040] The process conditions for the hydrogenation reaction are: temperature 45 to 80 °C, pressure 0.3 to 1.5 MPa, weight hourly space velocity of the feed 0.2 to 1.5 h -1 、hydrogen-to-anhydride molar ratio 2 to 20; preferably temperature 50 to 70 °C, pressure 0.5 to 1.0 MPa, weight hourly space velocity of the feed 0.4 to 1.0 h -1 、hydrogen-to-anhydride molar ratio 5 to 15.

[0041] The present invention is further configured such that in step S11, both the maleic anhydride solution and hydrogen are preheated to the reaction temperature and then fed into the hydrogenation reactor.

[0042] The present invention is further configured such that in step S12, the liquid-phase material is fed into the separation and purification system, and through light component removal, γ-butyrolactone removal, and maleic anhydride purification in sequence, high-purity maleic anhydride is obtained; all the separated γ-butyrolactone is recycled as the solvent for formulating the maleic anhydride solution in the feed, or part of it is recycled as the solvent, and the remaining part is used as the third monomer for synthesizing polybutylene succinate.

[0043] The present invention is further configured such that in step S2, the hydrogenation of maleic anhydride to prepare 1,4-butanediol includes the following steps:

[0044] S21. Dissolve maleic anhydride in tetrahydrofuran to prepare a maleic anhydride solution as the feed. After the maleic anhydride solution is pressurized, preheated, and vaporized, it is mixed with hydrogen and fed into a hydrogenation reactor for hydrogenation reaction;

[0045] S22. Perform gas-liquid separation on the reaction product after the hydrogenation reaction. The separated gaseous hydrogen is pressurized and preheated and then returned to the hydrogenation reactor for continued use. The liquid-phase material is fed into the separation and purification system, and through tetrahydrofuran removal, dehydration, and 1,4-butanediol purification in sequence, high-purity 1,4-butanediol is obtained; all the tetrahydrofuran is recycled as the solvent for formulating the maleic anhydride solution in the feed, or part of it is recycled as the solvent, and the remaining part is used as the third monomer for synthesizing polybutylene succinate.

[0046] The present invention is further configured such that in step S21, the hydrogenation reactor uses a gas-solid fixed-bed reactor, preferably an isothermal fixed-bed or adiabatic fixed-bed reactor, more preferably a tube-type isothermal fixed-bed or inter-stage heat-removing adiabatic fixed-bed reactor;

[0047] The copper-based catalyst is selected from CuZnZrE or CuZnAlG / SiO2 catalysts, where E and G are alkaline earth metal or rare earth metal elements, and the copper-based catalyst is preferably a CuZnZrLa or CuZnAlCe / SiO2 catalyst;

[0048] The solvent of the succinic anhydride solution is tetrahydrofuran, and the mass concentration of the fed succinic anhydride is 10-40%, preferably 15-35%, more preferably 20-30%;

[0049] The process conditions for the hydrogenation reaction are: temperature 250-320 °C, pressure 3.5-8.5 MPa, and the weight hourly space velocity of the feed is 0.25-2.0 h -1 and the molar ratio of hydrogen to anhydride is 30-150; preferably, the temperature is 260-300 °C, the pressure is 5.0-7.5 MPa, and the weight hourly space velocity of the feed is 0.5-1.0 h -1 and the molar ratio of hydrogen to anhydride is 50-100.

[0050] The present invention is further configured such that the CuZnZrLa catalyst used for the hydrogenation reaction in step S2 is Cu a Zn b Zr c La d , where a = 43-48, b = 23-28, c = 23-28, d = 2-7; or,

[0051] The CuZnAlCe / SiO2 catalyst used for the hydrogenation reaction is xCu a Zn b Al c Ce d / ySiO2 catalyst, where x / (x + y) = 70-80%, a = 45-55, b = 23-28, c = 23-28, d = 8-12.

[0052] The present invention is further configured such that in step S22, the liquid phase material after gas-liquid separation first enters a THF removal tower, and the THF separated from the top of the tower is recycled as the reaction solvent, or part of it is recycled as the reaction solvent, and the remaining part is used as the third monomer for synthesizing polybutylene succinate; the BDO material drawn from the bottom of the tower is further refined to obtain high-purity BDO, and a small amount of unreacted SAA is recycled as the reaction raw material.

[0053] The present invention is further configured such that the mass ratio of the succinic anhydride obtained in step S1 for use in step S2 to prepare BDO and for use in step S3 to synthesize polybutylene succinate is (1.0 - 2.2):1; for example, 1.0:1, 1.1:1, 1.2:1, 1.3:1, 1.4:1, 1.5:1, 1.6:1, 1.7:1, 1.8:1, 1.9:1, 2.0:1, 2.1:1 or 2.2:1.

[0054] The present invention is further configured such that in step S3, the process of ring-opening polycondensation to synthesize polybutylene succinate includes the following steps:

[0055] S31. Prepare a slurry by proportioning the succinic anhydride obtained in step S1, 1,4-butanediol obtained in step S2, with or without a third monomer, and an esterification catalyst, and feed it into an esterification reactor for pressure ring-opening esterification reaction;

[0056] S32. The esterification reaction product is depressurized to remove small molecules, a polymerization catalyst is added, and then it is fed into a prepolymerization reactor for negative pressure prepolycondensation reaction;

[0057] S33. The prepolymer product is further fed into a final polymerization reactor for vacuum final polycondensation reaction to obtain a polybutylene succinate polyester, and then the polybutylene succinate polyester pellet product is obtained by underwater cooling and pelletizing.

[0058] The present invention is further configured such that in step S31, the molar ratio of the raw material monomers is succinic anhydride:1,4-butanediol:third monomer = 1.00:(0.50 - 3.75):(0 - 2.00).

[0059] The present invention is further configured such that in step S31, when no third monomer is added, the molar ratio of the raw material monomers is succinic anhydride:1,4-butanediol = 1.0:(1.10 - 1.35);

[0060] When a third monomer is added and the third monomer is selected from polybasic acids or polybasic acid esters or cyclic anhydrides of polybasic acids, the molar ratio of the raw material monomers is succinic anhydride:1,4-butanediol:third monomer = 1.00:(1.15 - 2.50):(0.05 - 1.00);

[0061] When a third monomer is added and the third monomer is selected from polyhydric alcohols or cyclic ethers of polyhydric alcohols or hydroxy acids or hydroxy acid esters or lactones, the molar ratio of the raw material monomers is succinic anhydride:1,4-butanediol:third monomer = 1.00:(0.75 - 1.25):(0.05 - 0.55).

[0062] The present invention is further configured such that in step S31, a vertical reactor is used for the ring-opening esterification reaction, the ring-opening esterification catalyst is trifluoromethanesulfonic acid, and the dosage of the ring-opening esterification catalyst is 0.01 to 1.00% of the mass of succinic anhydride, preferably 0.05 to 0.50%;

[0063] The conditions for the ring-opening esterification reaction are a temperature of 150 to 200 °C, a pressure of 0.10 to 0.50 MPa, and a residence time of the material of 40 to 150 min, preferably a temperature of 160 to 180 °C, a pressure of 0.15 to 0.25 MPa, and a residence time of the material of 60 to 120 min.

[0064] The present invention is further configured such that in step S32, a vertical reactor is used for the pre-polycondensation reaction, the polymerization catalyst is tetrabutyl titanate, and the dosage is 0.01 to 0.50% of the mass of succinic anhydride, preferably 0.05 to 0.10%; the conditions for the pre-polycondensation reaction are a temperature of 180 to 240 °C, a pressure of 5 to 90 kPa, and a residence time of the material of 20 to 60 min, preferably a temperature of 200 to 220 °C, a pressure of 10 to 50 kPa, and a residence time of the material of 30 to 45 min.

[0065] The present invention is further configured such that in step S33, a horizontal reactor is used for the final polycondensation reaction, and the conditions for the final polycondensation reaction are a temperature of 200 to 260 °C, a pressure of 10 to 200 Pa, and a residence time of the material of 60 to 150 min, preferably a temperature of 220 to 240 °C, a pressure of 50 to 90 Pa, and a residence time of the material of 90 to 120 min.

[0066] The present invention is further configured such that the third monomer is at least one of polybasic acids and esters, cyclic anhydrides, polyols, cyclic ethers, hydroxy acids and esters, or lactones; wherein,

[0067] The polybasic acid is selected from C4-C 22 aliphatic polybasic acids, C8-C 16 aromatic polybasic acids, or C6-C 10 heterocyclic polybasic acids, preferably 1,4-butanedioic acid, 1,5-pentanedioic acid, 1,6-hexanedioic acid, 1,10-decanedioic acid, 1,4-cyclohexanedicarboxylic acid, terephthalic acid, isophthalic acid, 1,4-naphthalenedicarboxylic acid, 2,6-naphthalenedicarboxylic acid, or 2,5-furandicarboxylic acid;

[0068] The polybasic acid ester is selected from C4-C 22 monoesters or diesters of aliphatic polybasic acids, C8-C 16 monoesters or diesters of aromatic polybasic acids, or C6-C 10Heterocyclic polybasic acid monoester or diester, preferably dimethyl esters of 1,4 - butanedioic acid, 1,5 - pentanedioic acid, 1,6 - hexanedioic acid, 1,10 - decanedioic acid, 1,4 - cyclohexanedicarboxylic acid, terephthalic acid, isophthalic acid, 1,4 - naphthalenedicarboxylic acid or 2,5 - furandicarboxylic acid;

[0069] The cyclic anhydrides of the polybasic acids are selected from glutaric anhydride, adipic anhydride, phthalic anhydride, trimellitic anhydride or pyromellitic dianhydride, preferably glutaric anhydride or adipic anhydride;

[0070] The polyhydric alcohols are selected from C2 - C 22 aliphatic polyhydric alcohols, C8 - C 16 aromatic polyhydric alcohols or C6 - C 10 heterocyclic polyhydric alcohols, preferably ethylene glycol, 1,3 - propanediol, 1,5 - pentanediol, 1,6 - hexanediol, 1,10 - decanediol, 2 - methyl - 1,3 - propanediol, neopentyl glycol, trimethylolethane, trimethylolpropane, pentaerythritol, xylitol, sorbitol, 1,4 - cyclohexanediol, 1,4 - cyclohexanedimethanol, terephthalyl alcohol or 2,5 - furandimethanol;

[0071] The cyclic ethers of the polyhydric alcohols are selected from C2 - C5 aliphatic cyclic ethers, preferably ethylene oxide, propylene oxide, epichlorohydrin, propylene chlorohydrin, tetrahydrofuran, tetrahydrofurfuryl alcohol or tetrahydropyran;

[0072] The hydroxy acids or esters are selected from C2 - C 10 hydroxy fatty acids or esters, preferably glycolic acid, 2 - hydroxypropionic acid, 3 - hydroxypropionic acid, 3 - hydroxybutyric acid, 4 - hydroxybutyric acid, 5 - hydroxypentanoic acid, 6 - hydroxyhexanoic acid or their methyl esters;

[0073] The lactones are selected from β - propiolactone, γ - butyrolactone, γ - valerolactone, δ - valerolactone or ε - caprolactone, preferably γ - butyrolactone, δ - valerolactone or ε - caprolactone.

[0074] Compared with the prior art, the present invention has the following beneficial effects:

[0075] (1) The present invention uses maleic anhydride as the only starting material, and through a highly selective two - step tandem hydrogenation reaction, the two main monomers succinic anhydride and 1,4 - butanediol required for synthesizing PBSX are obtained; while in the traditional route, maleic anhydride is mostly used as the raw material to prepare succinic acid or dimethyl succinate, and 1,4 - butanediol is derived from the Reppe process (condensation and hydrogenation of acetylene and formaldehyde). Therefore, to obtain the two main monomers for synthesizing PBSX by the esterification method or the transesterification method, at least three organic raw materials, namely maleic anhydride, acetylene and formaldehyde, are required.

[0076] (2) The process route and flow of the present invention are short. Starting from maleic anhydride, PBSX can be obtained through only 3 tandem steps (hydrogenation of maleic anhydride to succinic anhydride, hydrogenation of succinic anhydride to 1,4-butanediol, and ring-opening polymerization of succinic anhydride with 1,4-butanediol or with 1,4-butanediol and a third monomer). However, in the prior art, since it is necessary to prepare succinic acid or succinic acid diester and 1,4-butanediol monomers, starting from maleic anhydride to prepare monomers and then polycondensing to synthesize PBS requires 3 - 7 reaction steps, with a long process flow or many co-products / by-products, a low overall yield and high energy consumption.

[0077] (3) The hydrogenation of maleic anhydride to succinic anhydride and the hydrogenation of succinic anhydride to 1,4-butanediol in the present invention are both highly selective processes for exclusive production. The separation of the monomer succinic anhydride and 1,4-butanediol is simple, with low investment, material consumption and energy consumption, and low production cost. In the prior art, due to different raw material routes and poor catalyst selectivity, a co-production process is basically adopted, such as the co-production of succinic anhydride and γ-butyrolactone and / or tetrahydrofuran by the hydrogenation of maleic anhydride, and the co-production of tetrahydrofuran and 1,4-butanediol by the hydrogenation of γ-butyrolactone, resulting in complex monomer separation, high investment, high raw material consumption and energy consumption, increased production cost, and problems with sales outlets due to mismatched co-product markets.

[0078] (4) In the overall process of the present invention, a small amount of γ-butyrolactone and tetrahydrofuran generated during the hydrogenation process and the tetrahydrofuran generated during the polymerization process can all be used as the third monomer for ring-opening copolymerization to synthesize PBSX. In addition, the solvents (γ-butyrolactone and tetrahydrofuran) used in the two-step hydrogenation reaction are all substances within the system. A small amount of by-products during the hydrogenation process can supplement the solvent loss, and there is no need to introduce new substances from outside the system, thereby simplifying the process, saving costs and reducing the cost.

[0079] In summary, in the overall process of synthesizing PBSX from maleic anhydride through two-step hydrogenation and polycondensation, a small amount of by-products γ-butyrolactone and tetrahydrofuran, whether used as the third monomer for modifying polycondensation to synthesize PBSX or as a supplementary solvent for hydrogenation reaction, can achieve a full-process closed loop, thereby realizing clean production, significantly reducing production costs, and improving the economic benefits and market competitiveness of PBSX. BRIEF DESCRIPTION OF THE DRAWINGS

[0080] Figure 1 It is a schematic material flow diagram for synthesizing the monomers succinic anhydride, 1,4-butanediol and polyester PBSX through three-step reactions starting from maleic anhydride.

[0081] Figure 2 It is a schematic flow diagram for producing SAA with MA as the raw material in step S1.

[0082] Figure 3 It is a schematic flow diagram for producing BDO with SAA as the raw material in step S2. DETAILED DESCRIPTION OF THE INVENTION

[0083] To further understand the present invention, the preferred embodiments of the present invention will be described below in conjunction with the embodiments. Obviously, the described embodiments are only a part of the embodiments of the present invention, rather than all of them. All other embodiments obtained by those of ordinary skill in the art based on the embodiments of the present invention without creative efforts belong to the scope of protection of the present invention.

[0084] Symbol description: MA is maleic anhydride, SAA is succinic anhydride, BDO is 1,4-butanediol, GBL is γ-butyrolactone, THF is tetrahydrofuran, PDO is 1,3-propanediol, TMP is trimethylolpropane, GA is glycolic acid, GAA is glutaric anhydride, SA is 1,10-sebacic acid, KCB is 1,4-naphthalenedicarboxylic acid, DMT is dimethyl terephthalate; TfOH and TBT are trifluoromethanesulfonic acid and tetrabutyl titanate respectively, and the dosage is based on the weight of SAA.

[0085] Calculation description:

[0086] 1) Calculation formulas for the conversion rate, selectivity and yield of the maleic anhydride hydrogenation reaction

[0087]

[0088] 2) Calculation formulas for the conversion rate, selectivity and yield of the succinic anhydride hydrogenation reaction

[0089]

[0090] 3) Calculation formula for the yield of the polycondensation reaction (based on the total weight of the charged monomers)

[0091]

[0092] 4) Calculation formulas for the yields of the whole-process polyester and by-products (based on the weight of the fed maleic anhydride)

[0093]

[0094]

[0095] 5) Calculation formulas for the yields of the whole-process polyester and wastewater (based on the total amount of the input organic raw materials)

[0096]

[0097] As Figures 1 to 3 shown, the process for synthesizing the monomer succinic anhydride (SAA) and 1,4-butanediol (BDO) and polyester PBSX provided by the present invention starting from maleic anhydride (MA) through three-step reactions is as follows:

[0098] Maleic anhydride is mixed with the solvent γ-butyrolactone (GBL) to prepare a GBL solution of maleic anhydride. After selective hydrogenation, a GBL solution of succinic anhydride is obtained, and then SAA and GBL are separated.

[0099] GBL is divided into two streams: one stream is recycled as the solvent for preparing the MA solution; the other stream is used as the third monomer for the co-polycondensation synthesis of modified PBS, and is co-polycondensed with SAA and BDO to synthesize GBL-modified poly(butylene succinate) (GPBS). The mixture of residual BDO and by-produced tetrahydrofuran (THF) and water is sent to the BDO+THF separation system.

[0100] SAA is divided into five streams: the first stream is used as a monomer for the co-polycondensation synthesis of GPBS; the second stream is used as a monomer for the polycondensation synthesis of PBS, and is polycondensed with BDO to synthesize PBS. The mixture of residual BDO and by-produced THF and water is sent to the BDO+THF separation system; the third stream is used as a monomer for the co-polycondensation synthesis of PBS, and is co-polycondensed with BDO and THF to synthesize PBS. The mixture of residual BDO and by-produced THF and water is sent to the BDO+THF separation system; the fourth stream is used as a monomer for the co-polycondensation synthesis of PBSX, and is co-polycondensed with BDO and an additional third monomer to synthesize PBSX. The mixture of residual BDO and by-produced THF and water is sent to the BDO+THF separation system; the fifth stream is mixed with the solvent THF to prepare a THF solution of SAA. After hydrogenation, a mixture of BDO, THF, and water is obtained, which is sent to the BDO+THF separation system together with the mixture of residual BDO and by-produced THF and water from each polymerization unit. After separation, BDO and THF are obtained.

[0101] BDO is divided into four streams: the first stream is used as a monomer for the co-polycondensation synthesis of GPBS; the second stream is used as a monomer for the polycondensation synthesis of PBS; the third stream is used as a monomer for the co-polycondensation synthesis of PBS; the fourth stream is used as a monomer for the co-polycondensation synthesis of PBSX.

[0102] THF is divided into two streams: one stream is recycled as the solvent for preparing the SAA solution; the other stream is used as the third monomer for the co-polycondensation synthesis of PBS.

[0103] THF has six sources: one is the recycled solvent for SAA hydrogenation, the second is a small amount of by-product from SAA hydrogenation; the third is a by-product from the co-polycondensation synthesis of GPBS; the fourth is a by-product from the polycondensation synthesis of PBS; the fifth is the residue and by-product from the co-polycondensation synthesis of PBS; the sixth is a by-product from the co-polycondensation synthesis of PBSX.

[0104] GBL has two sources: one is the recycled solvent for MA hydrogenation, the second is a small amount of by-product from MA hydrogenation.

[0105] Examples 1-8: Preparation of SAA by hydrogenation of maleic anhydride (special production process for the preparation of SAA by hydrogenation of maleic anhydride)

[0106] Maleic anhydride is dissolved in the solvent γ-butyrolactone (GBL) to prepare a solution with a concentration of 15-50 wt%. The maleic anhydride solution is pressurized and preheated to 40-90 °C, and then fed into a trickle-bed hydrogenation reactor filled with 0.5 wt% Pd / γ-Al2O3 or 0.3 wt% Pd-5.0 wt% Ni / γ-Al2O3 catalyst. (The catalyst is pre-reduced at 180 °C, a hydrogen space velocity of 100 h -1 , a hydrogen pressure of 1.0 MPa for 10 h); after fresh hydrogen is mixed with recycled hydrogen, it is preheated to the same temperature as the maleic anhydride solution and then enters the reactor; the gas and liquid flow downward in parallel for the hydrogenation reaction, the reaction pressure is 0.2-2.0 MPa, the feed weight space velocity is 0.2-2.0 h -1 , and the molar ratio of hydrogen to anhydride is 2-30. After the reaction product of the hydrogenation reaction enters the gas-liquid separator for separation, the gaseous hydrogen is pressurized and returned to the hydrogenation reactor for continued use in the hydrogenation reaction. The liquid-phase material enters the light-component removal tower, and a small amount of light components such as water generated by the reaction and GBL are distilled out from the top of the tower, and succinic anhydride (SAA) and trace heavy components are discharged from the bottom of the tower. The overhead product of the light-component removal tower is condensed and then fed into the GBL removal tower, and the light components are taken out from the top of the tower and sent to the waste water collection tank; GBL with a purity greater than 99.50% is obtained at the bottom of the tower and recycled as the hydrogenation solvent. The bottom product of the light-component removal tower enters the SAA purification tower, a small amount of heavy components are discharged from the bottom of the tower, and polymer-grade SAA with a purity of 99.95% is obtained at the top of the tower.

[0107] The specific operating conditions and reaction results of Examples 1-8 are shown in Table 1. It can be seen from Table 1 that using the supported palladium catalyst, within the investigated process conditions, it has excellent catalytic performance for the hydrogenation of maleic anhydride to prepare succinic anhydride, with a maleic anhydride conversion rate of 99.6-99.9 mol%, an SAA selectivity of 99.4-99.8 mol%, and a GBL selectivity of <0.6 mol%.

[0108] Coproduction process of preparing succinic anhydride and γ-butyrolactone by hydrogenation of maleic anhydride in Comparative Example 1

[0109] According to the method of Patent CN 114181038 B, maleic anhydride is mixed with GBL to prepare a 10 wt% maleic anhydride solution, which is preheated, vaporized and then heated to 220 °C and fed into the maleic anhydride hydrogenation reactor. In the maleic anhydride hydrogenation reactor filled with Cu-Ni-Al2O3 / SiO2 catalyst, at a reaction temperature of 240 °C, a pressure of 0.4 MPa, a hydrogen-to-anhydride ratio of 100, and a maleic anhydride weight hourly space velocity of 0.5 h -1 Under these conditions, maleic anhydride reacts with hydrogen to form GBL, SAA, and by-products such as THF, succinic acid, and n-butanol. After gas chromatography analysis and calculation based on the fed maleic anhydride as the reference, the maleic anhydride conversion rate is 99.9 mol%, the SAA selectivity is 41.0 mol%, the GBL selectivity is 47.0 mol%, the by-product THF selectivity is 9.04 mol%, and the total selectivity of by-products succinic acid and n-butanol is 2.90 mol%.

[0110] Table 1 Operating conditions and reaction results for the preparation of succinic anhydride (SAA) by hydrogenation of maleic anhydride (MA) in Examples 1 - 8

[0111]

[0112] Comparing Examples 1 - 8 and Comparative Example 1, it can be seen that by using the catalyst and hydrogenation reaction process of the present invention, high - activity (≥99.6 mol%) and high - selectivity (≥99.4 mol%) conversion of the raw material maleic anhydride into the target product succinic anhydride can be achieved under high raw material concentration (15 - 50 wt%), low reaction temperature (45 - 80 °C), high space velocity (0.2 - 2.0 h -1 -1), low hydrogen - to - anhydride ratio (2 - 30) and appropriate reaction pressure (0.2 - 2.0 MPa), realizing the exclusive production of succinic anhydride from maleic anhydride hydrogenation. However, for the catalyst and hydrogenation reaction process used in Comparative Example 1, the hydrogenation conversion of maleic anhydride can only be achieved under relatively harsh conditions (raw material concentration 10 wt%, reaction temperature 240 °C, space velocity 0.5 h -1 -1, hydrogen - to - anhydride ratio 100 and pressure 0.4 MPa), and the selectivity of the target product succinic anhydride is very low (only 41.06 mol%).

[0113] Examples 9 - 16 Preparation of BDO by hydrogenation of succinic anhydride (Exclusive process for preparing BDO by hydrogenation of SAA)

[0114] Dissolve succinic anhydride (SAA) in the solvent tetrahydrofuran (THF) to prepare a 10 - 40 wt% SAA solution. After the SAA solution is pressurized, pre - heated, and vaporized, it is mixed with hydrogen. The mixed material is heated to the reaction temperature of 240 - 340 °C and enters a fixed - bed hydrogenation reactor filled with a copper - based catalyst Cu 45 Zn 25 Zr 25 La5 or 75 wt% (Cu 50 Zn 20 Al 20 Ce 10 ) / 25 wt% SiO2 (the catalyst is pre - reduced at 350 °C, hydrogen space velocity 200 h -1 -1, hydrogen pressure 2.0 MPa for 24 h), and under a reaction pressure of 3.5 - 8.5 MPa and a feed space velocity of 0.2 - 5.0 h -1, The reaction of hydrogenating succinic anhydride (SAA) to 1,4 - butanediol (BDO) is carried out at a molar ratio of hydrogen to anhydride of 20 - 200. After the hydrogenation product is condensed and cooled, it enters a gas - liquid separator. After separation, the gaseous hydrogen is pressurized and returned to the reactor for continued use in the hydrogenation reaction; the liquid - phase material enters the THF removal column (extractive distillation column, with BDO as the extractant). THF with a purity greater than 99.50% is obtained at the top of the column and recycled as the reaction solvent. The bottom material of the THF column is sent to the dehydration column. Waste water containing trace amounts of n - butanol is taken out from the top of the column; BDO and SAA are taken out from the bottom and sent to the BDO refining column. Polymer - grade BDO with a purity of 99.92% is taken out from the top of the BDO refining column, and a small amount of unreacted SAA is taken out from the bottom and returned to the raw material preparation tank.

[0115] The specific operating conditions and reaction results of Examples 9 - 16 are shown in Table 2. As can be seen from Table 2, using a copper - based catalyst, within the investigated process conditions, it has good catalytic performance for the hydrogenation of SAA to prepare BDO. The conversion rate of SAA is 85.2 - 99.6 mol%, and the selectivity of BDO is 93.5 - 98.6 mol%. Under the optimized process conditions (SAA mass concentration of 20 - 30%, temperature of 260 - 300 °C, pressure of 5.0 - 7.5 MPa, liquid hourly space velocity of the feed of 0.5 - 1.0 h -1 and molar ratio of hydrogen to anhydride of 50 - 100), the catalyst has better performance, with the conversion rate of SAA > 95.6 mol%, the selectivity of BDO > 96.8%, and the selectivity of THF < 3.2%.

[0116] Table 2 Operating conditions and reaction results for the hydrogenation of succinic anhydride (SAA) to 1,4 - butanediol (BDO) in Examples 9 - 16

[0117]

[0118] Examples 17 - 26, Open - ring polycondensation test of SAA and BDO to synthesize PBSX

[0119] SAA is mixed with BDO or with BDO and a comonomer, and trifluoromethanesulfonic acid, an esterification catalyst, is added. After stirring evenly and pre - heating to 80 °C, it is sent to an open - ring esterification reactor for open - ring esterification reaction under set temperature and pressure. Then, tetrabutyl titanate, a polymerization catalyst, is added to the esterification product. After stirring evenly, it is continuously sent to a prepolymerization reactor for prepolymerization reaction under set temperature and negative pressure. Finally, the prepolymerization product is continuously sent to a final polymerization reactor for final polymerization reaction under set temperature and vacuum to obtain PBSX products. During the reaction process, since BDO dehydrates to form THF, after separation and purification, it is returned to the open - ring esterification process as a comonomer for use.

[0120] Examples 17 to 26 The specific operating conditions, yields and properties of PBSX are shown in Table 3. According to Table 3, under the process operating conditions shown in Table 3, the synthesized PBSX all have good yields and properties: the weight yield of PBSX is 76.18 - 83.07%, the melt index is 20.3 - 28.5 g / 10 min, the acid value is 9.6 - 28.6 mol / t, the weight-average molecular weight is 13.3×10 4 ~25.6×10 4 , the melting point is 91 - 115 °C, and the tensile strength is 29 - 48 MPa.

[0121] Table 3 Operating conditions for the synthesis of PBSX by ring-opening polycondensation of succinic anhydride (SAA) in Examples 17 - 26 and properties of PBSX

[0122]

[0123]

[0124] Example 27 Production of SAA and BDO by two-step hydrogenation of maleic anhydride and ring-opening polycondensation to produce PBS

[0125] According to Figures 1 to 3 the shown material flow, PBS is produced through three reaction steps.

[0126] Step 1: High-selectivity hydrogenation of maleic anhydride to produce SAA. Dissolve maleic anhydride in the γ-butyrolactone solvent to prepare a 25 wt% maleic anhydride solution. The total feed rate of the maleic anhydride solution is 5000 kg / h (where the feed rate of maleic anhydride is 1250 kg / h). Pressurize and preheat it to 60 °C, and send it into a trickle-bed hydrogenation reactor filled with 0.5 wt% Pd / γ-Al2O3 catalyst. After mixing fresh hydrogen and recycle hydrogen, preheat it to the same temperature as the maleic anhydride solution and enter the reactor. The gas and liquid flow downward in parallel for the hydrogenation reaction. The reaction pressure is 1.0 MPa, and the feed space velocity is 1.2 h -1, the molar ratio of hydrogen to anhydride is 20. After the reaction products enter the gas-liquid separator for separation, the hydrogen content in the gas phase is greater than 99%, and after being compressed by the recycle hydrogen compressor, it is returned to the hydrogenation reactor and continues to be used for the hydrogenation reaction. The liquid-phase material enters the light component removal tower, and a small amount of light components such as water and GBL generated by the reaction are distilled from the top of the tower and sent to the GBL removal tower after condensation; SAA and trace heavy components are discharged from the bottom of the tower and sent to the SAA rectification tower. The overhead product (2.5 kg / h) of the GBL removal tower is sent to the wastewater treatment system after cooling and condensation, and GBL with a purity of 99.95% (3754.2 kg / h) is obtained at the bottom of the tower. Among them, 3750.0 kg / h is recycled as a hydrogenation solvent, and the remaining 4.2 kg / h is used as a by-product. A small amount of heavy components (2.8 kg / h) are discharged from the bottom of the SAA rectification tower, and polymer-grade SAA with a purity of 99.95% is obtained at the top of the tower, with a production rate of 1266.6 kg / h. Among them, 686.6 kg / h is used for the hydrogenation of SAA to produce BDO, and 580.0 kg / h is used for ring-opening polymerization to produce PBS.

[0127] Step 2: Highly selective hydrogenation of SAA to produce BDO. The SAA produced in Step 1 is dissolved in THF to prepare a 20 wt% SAA solution. The total feed rate of the SAA solution is 3433.0 kg / h (where the feed rate of SAA is 686.6 kg / h). After being pressurized, preheated, and vaporized, it is mixed with hydrogen, and the mixed material is heated to the reaction temperature of 280 °C and enters a fixed-bed hydrogenation reactor filled with a 75 wt% (Cu 50 Zn 20 Al 20 Ce 10 ) / 25 wt% SiO2 catalyst. The reaction of hydrogenating SAA to produce BDO is carried out under a reaction pressure of 6.5 MPa, a feed space velocity of 1.5 h -1 , and a molar ratio of hydrogen to anhydride of 100. After the hydrogenation product is condensed and cooled, it enters the gas-liquid separator for separation. After separation, the hydrogen content in the gas phase is greater than 99%, and after being compressed by the recycle hydrogen compressor, it is returned to the reactor and continues to be used for the hydrogenation reaction; the liquid-phase material enters the THF removal tower (an extractive distillation tower with BDO as the extractant), and THF with a purity of 99.55% (2758.6 kg / h) is obtained at the top of the tower. Among them, 2746.4 kg / h is recycled as a reaction solvent, and the remaining 12.0 kg / h is used as a by-product or as the third monomer for subsequent polyester synthesis. The bottom material of the THF removal tower is sent to the dehydration tower, and wastewater containing trace amounts of n-butanol (127.8 kg / h) is taken from the top of the tower and sent to the wastewater treatment system; BDO and SAA are taken from the bottom of the tower and sent to the BDO tower for refining. Polymer-grade BDO with a purity of 99.92% (591.0 kg / h) is taken from the top of the BDO tower and used for ring-opening polymerization with SAA to produce PBS; a small amount of unreacted SAA (10.3 kg / h) is taken from the bottom of the tower and returned to the raw material preparation tank.

[0128] Step 3: Ring-opening polycondensation of SAA and BDO to synthesize PBS. 580.0 kg / h of SAA obtained in Step 1, 591.0 kg / h of BDO obtained in Step 2, and 55.0 kg / h of recycled BDO (the molar ratio of SAA to BDO in the feed is 1.00:1.13, and the recycle molar ratio is 1.00:1.24) are fed into a batching tank, 1.5 kg / h of trifluoromethanesulfonic acid catalyst is added, stirred evenly and preheated to 80 °C, and then fed into a ring-opening esterification reactor. The ring-opening esterification reaction is carried out under the conditions of a temperature of 170 °C, a pressure of 0.2 MPa, and a residence time of 60 min. After the esterification product is depressurized to remove small molecules at 15 kPa, 0.55 kg / h of tetrabutyl titanate polymerization catalyst is added to the esterification product, stirred evenly and continuously fed into a prepolymerization reactor. The prepolymerization reaction is carried out under the conditions of a temperature of 205 °C, a pressure of 15 kPa, and a residence time of 50 min. Finally, the prepolymer product is continuously fed into a final polymerization reactor, and the final polymerization reaction is carried out at a temperature of 240 °C, a pressure of 75 Pa, and a residence time of 120 min. The final polymerization product is granulated underwater to obtain PBS pellet products with a yield of 998.8 kg / h. A total of 227.2 kg / h of condensed gas-phase effluents are collected, and after separation and purification, 55.0 kg / h of BDO with a purity greater than 99.9%, 54.0 kg / h of by-product THF with a purity greater than 99.5%, and 118.2 kg / h of wastewater are obtained. The recycled BDO is fed into the batching tank for recycling.

[0129] Final results: In Step 1, the maleic anhydride conversion rate is 99.80 mol%, the SAA yield is 99.30 mol%, and the by-product GBL yield is 0.38 mol%; in Step 2, the SAA conversion rate is 98.50 mol%, the BDO yield is 95.64 mol%, and the by-product THF yield is 2.43 mol%; in Step 3, the PBS weight yield based on the monomer feed amount is 85.29 wt%, and the by-product THF weight yield is 4.61 wt%; the weight yield of the whole process of producing PBS starting from maleic anhydride (based on maleic anhydride): the total PBS yield is 79.90 wt%, the by-product GBL yield is 0.34 wt%, and the total THF yield is 5.28 wt%, and the by-product wastewater yield is 19.88 wt%. After testing, the performance indicators of the produced PBS are good: the melt index is 27.2 g / 10 min, the acid value is 20.5 mol / t, the weight-average molecular weight is 16.2×10 4 , the melting point is 113 °C, and the tensile strength is 45 MPa.

[0130] Example 28 Production of SAA, BDO, and THF as the third monomer by two-step hydrogenation of maleic anhydride and ring-opening copolymerization to synthesize PBS

[0131] According to Figures 1 to 3 the shown material flow, PBS is produced through three reaction steps.

[0132] Step 1: High-selectivity hydrogenation of maleic anhydride to produce SAA. The process is the same as step 1 of Example 27, except that: among the 1266.6 kg / h of SAA obtained by refining, the amount used for subsequent hydrogenation to produce BDO is 634.6 kg / h, and the amount used for ring-opening polymerization to produce PBS is 632.0 kg / h.

[0133] Step 2: High-selectivity hydrogenation of SAA to produce BDO. The SAA produced in step 1 is dissolved in THF to prepare a 40 wt% SAA solution. The total feed rate of the SAA solution is 1586.5 kg / h (where the feed rate of SAA is 634.6 kg / h). After pressurization, preheating, and gasification, it is mixed with hydrogen. The mixed material is heated to the reaction temperature of 320 °C and enters a fixed-bed hydrogenation reactor filled with 75 wt% (Cu 50 Zn 20 Al 20 Ce 10 ) / 25 wt% SiO2 catalyst. The reaction of hydrogenating SAA to produce BDO is carried out at a reaction pressure of 8.0 MPa, a feed space velocity of 0.5 h -1 , and a hydrogen-to-anhydride molar ratio of 50. The hydrogenation product is condensed and cooled and then enters a gas-liquid separator for separation. After separation, the hydrogen content in the gas phase is greater than 99%. After being compressed by circulation, it is returned to the reactor and continues to be used for the hydrogenation reaction; the liquid-phase material enters a THF removal column (an extractive distillation column with BDO as the extractant). THF with a purity greater than 99.55% and a flow rate of 1065.6 kg / h is obtained at the top of the column. Among them, 951.9 kg / h is recycled as the reaction solvent, and the remaining part of 113.7 kg / h is used as a comonomer for PBS. The bottom material of the THF removal column is sent to a dehydration column. Wastewater containing a small amount of n-butanol (143.2 kg / h) is taken out from the top of the column and sent to the wastewater treatment system; BDO and SAA are taken out from the bottom of the column and sent to the BDO column for refining. Polymer-grade BDO with a purity of 99.92% and a flow rate of 427.0 kg / h is taken out from the top of the BDO column and used for ring-opening polymerization with SAA to produce PBS; a small amount of heavy components (1.2 kg / h) is taken out from the bottom of the column and sent to the solid waste treatment system.

[0134] Step 3: Ring-opening polycondensation of SAA with BDO and THF to synthesize PBS. 632 kg / h of SAA produced in Step 1, 427.0 kg / h of BDO produced in Step 2, 113.7 kg / h of THF, and 111.5 kg / h of recycled THF (the feed molar ratio of SAA:BDO:THF is 1.00:0.75:0.25, and the recycle molar ratio is 1.00:0.75:0.49) are fed into a batching tank, 2.0 kg / h of trifluoromethanesulfonic acid catalyst and 0.1 kg / h of hydrochloric acid (20 wt%) are added, stirred evenly and preheated to 85 °C, then fed into a ring-opening esterification reactor, and ring-opening esterification reaction is carried out under the conditions of a temperature of 180 °C, a pressure of 0.5 MPa, and a residence time of 75 min. After the esterification product is depressurized to remove small molecules at 25 kPa, 0.58 kg / h of tetrabutyl titanate polymerization catalyst is added to the esterification product, stirred evenly and continuously fed into a prepolymerization reactor, and prepolymerization reaction is carried out under the conditions of a temperature of 210 °C, a pressure of 25 kPa, and a residence time of 50 min. Finally, the prepolymer product is continuously fed into a final polymerization reactor, and final polymerization reaction is carried out at a temperature of 245 °C, a pressure of 50 Pa, and a residence time of 150 min. The final polymerization product is granulated underwater to obtain PBS pellet products with a yield of 1089.0 kg / h. A total of 199.5 kg / h of condensed gas-phase off-gas is collected, and THF with a purity greater than 99.5% of 111.5 kg / h and wastewater of 88.0 kg / h (containing about 1.5 kg / h of BDO) are obtained after separation and purification. The recycled THF is fed into the batching tank of the polymerization unit for recycling.

[0135] Final results: In Step 1, the maleic anhydride conversion rate is 99.80 mol%, the SAA yield is 99.30 mol%, and the by-product GBL yield is 0.38 mol%; in Step 2, the SAA conversion rate is 100 mol%, the BDO yield is 74.77 mol%, and the THF yield is 24.88 mol%; in Step 3, the PBS weight yield based on the monomer feed amount is 92.86 wt%. The weight yield of the whole process of producing PBS starting from maleic anhydride (based on maleic anhydride): the total PBS yield is 87.12 wt%, the by-product GBL yield is 0.34 wt%, and the by-product wastewater yield is 18.70 wt%. After testing, the various performance indicators of the produced PBS are good: the melt index is 21.5 g / 10 min, the acid value is 25.5 mol / t, the weight-average molecular weight is 14.2×10 4 , the melting point is 112 °C, and the tensile strength is 43 MPa.

[0136] Example 29 Production of SAA, BDO, and THF as the third monomer by two-step hydrogenation of maleic anhydride and ring-opening copolymerization thereof to synthesize modified PBS (GPBS)

[0137] According to Figures 1 to 3 the shown material flow, γ-butyrolactone modified PBS is produced through three reaction steps.

[0138] Step 1: High-selectivity hydrogenation of maleic anhydride to produce SAA. Dissolve maleic anhydride in GBL solvent to prepare a 40 wt% solution. The total feed rate of the maleic anhydride solution is 3125 kg / h (where the feed rate of maleic anhydride is 1250 kg / h). Pressurize and preheat it to 80 °C, and then send it into a trickle-bed hydrogenation reactor filled with 0.5 wt% Pd / γ-Al2O3 catalyst. After fresh hydrogen and recycle hydrogen are mixed, preheat them to the same temperature as the maleic anhydride solution and then enter the reactor. The gas and liquid flow downward in parallel for the hydrogenation reaction. The reaction pressure is 1.5 MPa, the feed space velocity is 0.75 h -1 , and the hydrogen-to-anhydride molar ratio is 30. After the reaction product enters the gas-liquid separator for separation, the gas-phase hydrogen content is greater than 99%. After being compressed by the recycle hydrogen compressor, it returns to the reactor and continues to be used for the hydrogenation reaction. The liquid-phase material enters the light-component removal tower. A small amount of light components such as water generated by the reaction and GBL are distilled from the top of the tower, condensed, and then sent to the GBL removal tower; SAA and trace heavy components are discharged from the bottom of the tower and sent to the SAA rectification tower. The overhead product (9.6 kg / h) of the GBL removal tower is sent to the wastewater treatment system after condensation and cooling; 99.95% pure GBL (1921.0 kg / h) is obtained at the bottom of the tower, of which 1875.0 kg / h is recycled as the hydrogenation solvent, and the remaining 46.0 kg / h is used as the comonomer of PBS. A small amount of heavy components (0.8 kg / h) are discharged from the bottom of the SAA rectification tower, and 99.95% pure polymer-grade SAA is obtained at the top of the tower, with a production rate of 1222.0 kg / h, of which 662.0 kg / h is used for subsequent hydrogenation of SAA to produce BDO, and 560.0 kg / h is used for ring-opening polymerization to produce PBS.

[0139] Step 2: High-selectivity hydrogenation of SAA to produce BDO. Dissolve the SAA produced in Step 1 in THF to prepare a 20 wt% SAA solution. The total feed rate of the SAA solution is 3310.0 kg / h (where the feed rate of SAA is 662.0 kg / h). After being pressurized, preheated, and vaporized, it is mixed with hydrogen. The mixed material is heated to the reaction temperature of 280 °C and then enters a fixed-bed hydrogenation reactor filled with 75 wt% (Cu 50 Zn 20 Al 20 Ce 10 ) / 25 wt% SiO2 catalyst. At a reaction pressure of 6.5 MPa and a feed space velocity of 1.5 h -1At a molar ratio of hydrogen anhydride of 100, the reaction of hydrogenating SAA to produce BDO is carried out. After the hydrogenation product is condensed and cooled, it enters a gas-liquid separator for separation. After separation, the hydrogen content in the gas phase is greater than 99%. After being compressed by a recycle hydrogen compressor, it returns to the reactor and continues to be used for the hydrogenation reaction. The liquid-phase material enters a THF removal column (an extractive distillation column with BDO as the extractant). THF with a purity of 99.55% and a flow rate of 2659.7 kg / h is obtained at the top of the column. Among them, 2648.0 kg / h is recycled as the reaction solvent, and the remaining 11.7 kg / h is used as a by-product. The bottom material of the THF removal column is sent to a dehydration column. Wastewater containing a trace amount of n-butanol (122.9 kg / h) is taken out from the top of the column and sent to the wastewater treatment system. BDO and SAA are taken out from the bottom of the column and sent to the BDO column for purification. Polymer-grade BDO with a purity of 99.92% and a flow rate of 570.0 kg / h is taken out from the top of the BDO column and is used for ring-opening polymerization with SAA to produce PBS. A small amount of unreacted SAA (10.2 kg / h) is taken out from the bottom of the column and returned to the raw material preparation tank.

[0140] Step 3: Ring-opening polycondensation of SAA with BDO and GBL to synthesize modified PBS. 560.0 kg / h of SAA produced in Step 1, 46.0 kg / h of GBL, 570.0 kg / h of BDO produced in Step 2, and 52 kg / h of recycled BDO (the molar ratio of SAA:BDO:GBL feed is 1.00:1.13:0.10, and the recycle molar ratio is 1.00:1.23:0.10) are sent to a batching tank, 1.5 kg / h of trifluoromethanesulfonic acid catalyst is added, stirred evenly and preheated to 90 °C, and then sent to a ring-opening esterification reactor. The ring-opening esterification reaction is carried out under the conditions of a temperature of 160 °C, a pressure of 0.3 MPa, and a residence time of 90 min. After the esterification product is depressurized to remove small molecules at 25 kPa, 0.60 kg / h of tetrabutyl titanate, a polymerization catalyst, is added to the esterification product. After stirring evenly, it is continuously sent to a prepolymerization reactor. The prepolymerization reaction is carried out under the conditions of a temperature of 190 °C, a pressure of 25 kPa, and a residence time of 60 min. Finally, the prepolymerization product is continuously sent to a final polymerization reactor. The final polymerization reaction is carried out under the conditions of a temperature of 230 °C, a pressure of 50 Pa, and a residence time of 150 min. The final polymerization product is granulated underwater to obtain GPBS pellet products with a yield of 1010.0 kg / h. A total of 218.0 kg / h of condensed gas-phase off-gas is collected. After separation and purification, 52.0 kg / h of BDO with a purity greater than 99.9%, 52.0 kg / h of by-product THF with a purity greater than 99.5%, and 114.0 kg / h of wastewater are obtained. The recovered BDO is sent to the batching tank of the polymerization unit for recycling.

[0141] Final results: In Step 1, the conversion rate of maleic anhydride is 99.94 mol%, the yield of SAA is 95.80 mol%, and the yield of GBL is 4.19 mol%; in Step 2, the conversion rate of SAA is 98.46 mol%, the yield of BDO is 95.67 mol%, and the yield of by-product THF is 2.45 mol%; in Step 3, the weight yield of GPBS based on the monomer feed amount is 85.88 wt%, and the weight yield of by-product THF is 4.42 wt%. The weight yield of the whole process of producing GPBS starting from maleic anhydride (based on maleic anhydride): the total yield of GPBS is 80.80 wt%, the total yield of by-product THF is 5.10 wt%, and the yield of by-product wastewater is 19.72 wt%. After testing, the performance indicators of the produced GPBS are good: melt index 24.8 g / 10 min, acid value 15.6 mol / t, weight average molecular weight 17.2×10 4 , melting point 96 °C, tensile strength 34 MPa.

[0142] Example 30 Production of SAA and BDO by two-step hydrogenation of maleic anhydride and ring-opening copolymerization of it with by-products GBL and THF as the third monomer to produce modified PBS (GPBS)

[0143] The production process, catalyst and operating conditions are the same as in Example 28, except that: in Step 3, 4.2 kg / h of GBL by-produced in Step 1 is also used as a modified copolymerization monomer for synthesizing PBS, and the output of GPBS is 1093.0 kg / h; in Step 3, the weight yield of GPBS based on the monomer feed amount is 92.87 wt%; the total weight yield of the whole process of producing GPBS starting from maleic anhydride (based on maleic anhydride) is 87.44 wt%, and the performance indicators of the produced GPBS are: melt index 25.8 g / 10 min, acid value 18.5 mol / t, weight average molecular weight 16.8×10 4 , melting point 103 °C, tensile strength 38 MPa. Obviously, all by-products GBL and THF generated by the two-step hydrogenation and polycondensation reaction of maleic anhydride are effectively utilized, improving the polyester yield and reducing the production cost, and the performance indicators of the produced GPBS are excellent.

[0144] Comparative Example 2 Production of SAA and BDO by two-step hydrogenation of maleic anhydride

[0145] According to the method of Patent CN 114181038 B. 5 kg / h of maleic anhydride is mixed with 45 kg / h of GBL to prepare a 10 wt% maleic anhydride solution, which is preheated, vaporized and then heated to 220 °C and fed into the maleic anhydride hydrogenation reactor. In the maleic anhydride hydrogenation reactor filled with Cu-Ni-Al2O3 / SiO2 catalyst, at a reaction temperature of 240 °C, a pressure of 0.4 MPa, a hydrogen-to-anhydride ratio of 100 and a maleic anhydride weight hourly space velocity of 0.5 h -1Under such conditions, maleic anhydride reacts with hydrogen to produce GBL, SAA, and by-products such as THF, succinic acid, and n-butanol. After the reaction products are cooled, condensed, and subjected to gas-liquid separation, the gas phase is recycled as recycled hydrogen, and the liquid phase enters the stabilizer column. Water, n-butanol, THF, etc. are separated at the top of the stabilizer column and enter the dehydration column. Process wastewater containing a small amount of n-butanol and THF is separated at the top of the dehydration column and sent out of the boundary for treatment. GBL and a small amount of SAA at the bottom of the dehydration column are returned to the stabilizer column, and succinic acid produced as a by-product in the dehydration column is dehydrated to form SAA. The crude SAA separated at the bottom of the stabilizer column is sent to the light component removal column. The light components separated from the crude SAA are at the top and returned to the dehydration column; the bottom stream is divided into three parts: one part is recycled to the maleic anhydride hydrogenation unit as a solvent, one part is sent to the GBL hydrogenation unit, and the remaining part is sent to the heavy component removal column. The refined SAA product of 2.1 kg / h is obtained at the top of the heavy component removal column. 0.31 kg / h of THF by-produced during the maleic anhydride hydrogenation process is discharged out of the system with the wastewater.

[0146] GBL from the SAA product refining unit is sent to a GBL hydrogenation reactor filled with a Cu-Ni-Al2O3 / SiO2 catalyst, where it reacts with the fresh hydrogen supplemented from outside the boundary and the recycled hydrogen from the GBL hydrogenation reaction to produce BDO, and at the same time, a small amount of by-products such as THF, n-butanol, and acetal are generated. The GBL hydrogenation reaction temperature is 150 °C, the pressure is 6.5 MPa, and the hydrogen-ester ratio is 50. After the reaction products are cooled, condensed, and subjected to gas-liquid separation, the gas phase is recycled as recycled hydrogen, and the liquid-phase product enters the GBL recovery column. GBL is recovered at the top of the column and recycled. The bottom stream is transported to the BDO product column, and 2.2 kg / h of the BDO product is recovered at the top of the BDO product column. The bottom of the column contains heavy components such as acetal.

[0147] Final result: Based on the fed maleic anhydride, the maleic anhydride conversion rate is 99.85 mol%, the SAA yield is 41.40 mol%, the BDO yield is 47.22 mol%, and the by-product THF yield is 10.02 mol%; the total yield of the two products, SAA and BDO, is 88.62 mol%.

[0148] Obviously, although this process can produce SAA and BDO through two-step reactions by co-producing SAA and GBL through maleic anhydride hydrogenation and co-producing BDO and THF through GBL hydrogenation, the yields of the main products are both lower than 50%. There are many co-products (GBL and THF) and by-products (succinic acid, n-butanol, acetal, and water) in the two-step hydrogenation reactions, resulting in high raw material consumption; the temperature and hydrogen-maleic anhydride ratio in the first-step hydrogenation process are high, increasing energy consumption, the separation process is complex, and the by-produced succinic acid will also cause corrosion to the equipment, leading to increased investment.

[0149] From the results of Examples 27 to 30 (see Table 4), it can be seen that using the by-products THF or / and GBL generated from the hydrogenation reaction as the third monomer for PBS synthesis can improve the effective utilization rate of the starting material maleic anhydride and the yield of the polyester product PBS. Moreover, under the condition of condensing and recycling THF in the gas phase of the polymerization reaction and recycling it, the consumption balance between THF by-products from hydrogenation and ring-opening polycondensation in the overall process can be achieved, enabling all by-products to be utilized without external discharge, and at the same time producing polyester PBS or modified PBS with excellent properties. In addition, by comparing Example 27 and Comparative Example 2, it can be seen that using the existing maleic anhydride hydrogenation co-production process, the total yield of SAA + BDO is only 88.62 mol%, which is much lower than the SAA yield of 99.30 mol% and the BDO yield of 95.64 mol% of the special production process of the present invention.

[0150] Example 31: Production of SAA and BDO by two-step hydrogenation of maleic anhydride and ring-opening co-polycondensation with an externally added third monomer TMP to synthesize modified PBS (TPBS)

[0151] According to Figures 1 to 3 the shown material flow, trimethylolpropane-modified PBS is produced through three reaction steps.

[0152] Step 1: High-selectivity hydrogenation of maleic anhydride to produce SAA. Maleic anhydride is dissolved in GBL solvent to prepare a 30 wt% solution. The total feed rate of the maleic anhydride solution is 4166.6 kg / h (where the feed rate of maleic anhydride is 1250 kg / h), pressurized and preheated to 70 °C, and fed into a trickle-bed hydrogenation reactor filled with 0.3 wt% Pd - 5.0 wt% Ni / γ-Al2O3 catalyst. After fresh hydrogen and recycled hydrogen are mixed, they are preheated to the same temperature as the maleic anhydride solution and enter the reactor. The gas and liquid flow downward in parallel for the hydrogenation reaction, with a reaction pressure of 1.2 MPa, a feed space velocity of 1.0 h -1 ⁻¹, and a hydrogen-to-anhydride molar ratio of 25. After the reaction product enters the gas-liquid separator for separation, the gas-phase hydrogen content is greater than 99%. After being compressed by the recycle hydrogen compressor, it returns to the reactor and continues to be used for the hydrogenation reaction. The liquid-phase material enters the light component removal tower, and a small amount of light components such as water and GBL generated by the reaction are distilled from the top of the tower. After condensation, they are sent to the GBL removal tower; SAA and trace heavy components are discharged from the bottom of the tower and sent to the SAA distillation tower. The overhead product (1.8 kg / h) of the GBL removal tower is sent to the wastewater treatment system after condensation and cooling; GBL with a purity of 99.95% (2925.3 kg / h) is obtained at the bottom of the tower, of which 2916.6 kg / h is recycled as the hydrogenation solvent, and the remaining 8.7 kg / h is used as a by-product. A small amount of heavy components (1.5 kg / h) are discharged from the bottom of the SAA distillation tower, and polymer-grade SAA with a purity of 99.95% is obtained at the top of the tower, with a production rate of 1264.0 kg / h, of which 662.0 kg / h is used for subsequent hydrogenation of SAA to produce BDO, and 602.0 kg / h is used for ring-opening polymerization to produce PBS.

[0153] Step 2: Highly selective hydrogenation of SAA to produce BDO. The SAA produced in Step 1 is dissolved in THF to prepare a 30 wt% SAA solution. The total feed rate of the SAA solution is 2206.6 kg / h (where the feed rate of SAA is 662.0 kg / h). After pressurization, preheating, and gasification, it is mixed with hydrogen, and the mixed material is heated to the reaction temperature of 290 °C and enters a fixed-bed hydrogenation reactor filled with Cu 45 Zn 25 Zr 25 Ca5 catalyst. The reaction of hydrogenating SAA to BDO is carried out at a reaction pressure of 8.0 MPa, a feed space velocity of 1.0 h -1 ⁻¹, and a hydrogen-to-anhydride molar ratio of 150. After the hydrogenation product is condensed and cooled, it enters a gas-liquid separator for separation. After separation, the hydrogen content in the gas phase is greater than 99%. After being compressed by a recycle hydrogen compressor, it is returned to the reactor and continues to be used for the hydrogenation reaction; the liquid-phase material enters a THF removal column (which is an extractive distillation column with BDO as the extractant). At the top of the column, 1556.1 kg / h of THF with a purity of 99.55% is obtained, of which 1544.6 kg / h is recycled as the reaction solvent, and the remaining 11.5 kg / h is used as a by-product. The bottom material of the THF removal column is sent to a dehydration column. Wastewater containing a small amount of n-butanol (123.0 kg / h) is taken out from the top of the column and sent to the wastewater treatment system; BDO and SAA are taken out from the bottom of the column and sent to the BDO column for refining. At the top of the BDO column, 567.5 kg / h of polymer-grade BDO with a purity of 99.92% is obtained, which is used for ring-opening polymerization with SAA to produce TPBS; a small amount of unreacted succinic anhydride (12.0 kg / h) is taken out from the bottom of the column and returned to the raw material preparation tank.

[0154] Step 3: Ring-opening polycondensation of SAA with BDO and TMP to synthesize modified PBS. Feed 602.0 kg / h of SAA produced in Step 1, 567.5 kg / h of BDO produced in Step 2, 55.0 kg / h of recycled BDO, and 40.3 kg / h of externally added third monomer modifier TMP (the molar ratio of SAA:BDO:TMP feed is 1.00:1.05:0.05, and the recycling molar ratio is 1.00:1.15:0.05) into the batching tank, add 1.5 kg / h of trifluoromethanesulfonic acid catalyst, stir evenly and preheat to 80 °C, then feed it into the ring-opening esterification reactor. Carry out the ring-opening esterification reaction under the conditions of a temperature of 160 °C, a pressure of 0.25 MPa, and a residence time of 45 min. After the esterification product is depressurized to remove small molecules at 30 kPa, add 0.75 kg / h of polymerization catalyst tetrabutyl titanate to the esterification product, stir evenly and continuously feed it into the prepolymerization reactor. Carry out the prepolymerization reaction under the conditions of a temperature of 200 °C, a pressure of 30 kPa, and a residence time of 50 min. Finally, continuously feed the prepolymer product into the final polymerization reactor, carry out the final polymerization reaction at a temperature of 240 °C, a pressure of 50 Pa, and a residence time of 135 min. The final polymerization product is underwater pelletized to obtain TPBS pellet products with a yield of 1036.0 kg / h. A total of 228.6 kg / h of condensed gas-phase effluents are collected, and after separation and purification, 55.0 kg / h of BDO with a purity greater than 99.9%, 52.0 kg / h of by-product THF with a purity greater than 99.5%, and 121.6 kg / h of wastewater are obtained. The recycled BDO is sent to the batching tank of the polymerization unit for recycling.

[0155] Final results: In Step 1, the maleic anhydride conversion rate is 99.88 mol%, the SAA yield is 99.10 mol%, and the by-product GBL yield is 0.81 mol%; in Step 2, the SAA conversion rate is 98.19 mol%, the BDO yield is 95.25 mol%, and the by-product THF yield is 2.41 mol%; in Step 3, the weight yield of TPBS based on the monomer feed amount is 85.63 wt%, and the weight yield of by-product THF is 4.30 wt%. The overall weight yield (based on maleic anhydride) from maleic anhydride: the total yield of TPBS is 82.88 wt%, the total yield of by-product THF is 5.08 wt%, and the by-product GBL yield is 0.70 wt%; based on the total amount of organic raw materials input, the total yield of TPBS is 80.29 wt%, and the total yield of by-product wastewater is 19.10 wt%. After testing, the performance indicators of the produced TPBS are good: melt index 22.6 g / 10 min, acid value 13.6 mol / t, weight average molecular weight 25.2×10 4 , melting point 103 °C, tensile strength 34 MPa.

[0156] Example 32 Production of SAA and BDO by two-step hydrogenation of maleic anhydride and their ring-opening copolymerization with externally added third monomer adipic acid to synthesize PBSA

[0157] According to Figures 1 to 3 the material flow shown, PBSA copolymerized with the external monomer adipic acid is produced through three reaction steps.

[0158] Step 1: High-selectivity hydrogenation of maleic anhydride to produce SAA. The process and operating conditions are the same as those in Step 1 of Example 31, except that: among the 1264.0 kg / h of SAA obtained by refining, the amount used for subsequent hydrogenation to produce BDO is 778.0 kg / h, and the amount used for ring-opening polymerization to produce PBSA is 486.0 kg / h.

[0159] Step 2: High-selectivity hydrogenation of SAA to produce BDO. The process and operating conditions are the same as those in Step 2 of Example 31, except that: the feed rate of SAA is different. The total feed rate of the SAA solution is 2596.6 kg / h, among which the feed rate of SAA is 778.0 kg / h; 1832.1 kg / h of THF is obtained at the top of the THF stripper, among which 1818.6 kg / h is recycled as the reaction solvent, and the remaining 13.5 kg / h is used as a by-product; 144.5 kg / h of wastewater containing trace amounts of n-butanol is taken out at the top of the dehydration tower; 666.9 kg / h of BDO is taken out at the top of the BDO tower, and 14.1 kg / h of unreacted SAA is taken out at the bottom of the tower.

[0160] Step 3: Ring-opening polycondensation of SAA with BDO and adipic acid to synthesize PBSA. Feed 486.0 kg / h of SAA produced in Step 1, 666.9 kg / h of BDO produced in Step 2, 55.0 kg / h of recycled BDO, and 283.8 kg / h of externally added comonomer adipic acid (the feeding molar ratio of SAA:BDO:adipic acid is 1.00:1.52:0.40, and the recycling molar ratio is 1.00:1.65:0.40) into the batching tank, add 1.5 kg / h of trifluoromethanesulfonic acid catalyst, stir evenly and preheat to 80 °C, then feed it into the ring-opening esterification reactor, and carry out the ring-opening esterification reaction at a temperature of 170 °C, a pressure of 0.25 MPa, and a residence time of 60 min. After the esterification product is depressurized to remove small molecules at 50 kPa, add 0.65 kg / h of polymerization catalyst tetrabutyl titanate to the esterification product, stir evenly and continuously feed it into the prepolymerization reactor, and carry out the prepolymerization reaction at a temperature of 210 °C, a pressure of 50 kPa, and a residence time of 45 min. Finally, continuously feed the prepolymerization product into the final polymerization reactor, and carry out the final polymerization reaction at a temperature of 240 °C, a pressure of 50 Pa, and a residence time of 120 min. The final polymerization product is pelletized underwater to obtain PBSA pellet products with a yield of 1224.5 kg / h. A total of 267.0 kg / h of the condensed gas-phase effluent is collected, and after separation and purification, 55.0 kg / h of BDO with a purity greater than 99.9%, 43.5 kg / h of by-product THF with a purity greater than 99.5%, and 168.5 kg / h of wastewater are obtained. The recovered BDO is sent to the batching tank of the polymerization unit for recycling.

[0161] Final results: In Step 1, the maleic anhydride conversion rate is 99.88 mol%, the SAA yield is 99.10 mol%, and the by-product GBL yield is 0.81 mol%; in Step 2, the SAA conversion rate is 98.19 mol%, the BDO yield is 95.25 mol%, and the by-product THF yield is 2.41 mol%; in Step 3, the weight yield of PBSA based on the monomer feed amount is 85.23 wt%, and the weight yield of by-product THF is 3.03 wt%; the weight yield of the whole process of producing PBSA starting from maleic anhydride (based on maleic anhydride): the total yield of PBSA is 97.96 wt%, the total yield of by-product THF is 4.56 wt%, and the by-product GBL yield is 0.70 wt%; based on the total amount of organic raw materials input, the total yield of PBS is 79.83 wt%, and the by-product wastewater yield is 20.52 wt%. After testing, the performance indicators of the produced PBSA are good: the melt index is 26.6 g / 10 min, the acid value is 19.5 mol / t, and the weight-average molecular weight is 18.5×10 4 , the melting point is 95 °C, and the tensile strength is 36 MPa.

[0162] Example 33: Two-step hydrogenation of maleic anhydride to produce SAA and BDO and their ring-opening copolymerization with externally added third monomer DMT to synthesize PBST

[0163] According to Figures 1 to 3 the process flow shown, PBST copolymerized with external monomer DMT is produced through three reaction steps.

[0164] Step 1: Maleic anhydride is highly selectively hydrogenated to produce SAA. The process and operating conditions are the same as those in Step 1 of Example 31, except that: among the 1264.0 kg / h of SAA obtained by refining, the amount used for subsequent hydrogenation to produce BDO is 864.0 kg / h, and the amount used for ring-opening polymerization to produce PBS is 400.0 kg / h.

[0165] Step 2: SAA is highly selectively hydrogenated to produce BDO. The SAA produced in Step 1 is dissolved in THF to prepare a 40 wt% SAA solution. The total feed rate of the SAA solution is 2160.0 kg / h (where the SAA feed rate is 864.0 kg / h). After being pressurized, preheated, and vaporized, it is mixed with hydrogen. The mixed material is heated to the reaction temperature of 310 °C and enters a fixed-bed hydrogenation reactor filled with Cu 45 Zn 25 Zr 25 Ca5 catalyst. The reaction of SAA hydrogenation to produce BDO is carried out at a reaction pressure of 6.0 MPa, a feed space velocity of 1.0 h -1 ⁻¹, and a hydrogen-to-anhydride molar ratio of 200. After the hydrogenation product is condensed and cooled, it enters a gas-liquid separator for separation. After separation, the gas-phase hydrogen content is greater than 99%. After being compressed by a recycle hydrogen compressor, it returns to the reactor and continues to be used for the hydrogenation reaction; the liquid-phase material enters a THF removal tower (an extractive distillation tower, and the extractant is BDO). 1310.8 kg / h of THF with a purity of 99.55% is obtained at the top of the tower. Among them, 1296.0 kg / h is recycled as the reaction solvent, and the remaining 14.8 kg / h is used as a by-product. The bottom material of the THF removal tower is sent to a dehydration tower. Waste water containing a small amount of n-butanol (155.2 kg / h) is taken out from the top of the tower and sent to the waste water treatment system; BDO and SAA are taken out from the bottom of the tower and sent to the BDO tower for refining. 748.0 kg / h of polymerization-grade BDO with a purity of 99.92% is taken out from the top of the BDO tower and used for ring-opening polymerization with SAA to produce PBST; a small amount of unreacted succinic anhydride (14.0 kg / h) is taken out from the bottom of the tower and returned to the raw material preparation tank.

[0166] Step 3: SAA undergoes ring-opening polycondensation with BDO and DMT to synthesize PBST. 400.0 kg / h of SAA produced in Step 1, 748.0 kg / h of BDO produced in Step 2, 30.0 kg / h of recycled BDO, and 776.0 kg / h of externally added comonomer DMT (the molar ratio of SAA:BDO:DMT feed is 1.00:2.08:1.00, and the recycling molar ratio is 1.00:2.16:1.00) are fed into the batching tank. 3.5 kg / h of trifluoromethanesulfonic acid catalyst is added, stirred evenly, and preheated to 80°C, then fed into the ring-opening esterification reactor. The ring-opening esterification reaction is carried out under the conditions of a temperature of 150°C, a pressure of 0.15 MPa, and a residence time of 75 min. After the esterification product is depressurized to remove small molecules at 20 kPa, 1.5 kg / h of tetrabutyl titanate polymerization catalyst is added to the esterification product, stirred evenly, and continuously fed into the prepolymerization reactor. The prepolymerization reaction is carried out under the conditions of a temperature of 180°C, a pressure of 50 kPa, and a residence time of 60 min. Finally, the prepolymer product is continuously fed into the final polymerization reactor, and the final polymerization reaction is carried out at a temperature of 220°C, a pressure of 30 Pa, and a residence time of 150 min. The final polymerization product is underwater pelletized to obtain PBS pellet products with a production rate of 1568.0 kg / h. A total of 386.0 kg / h of condensed gas-phase effluents are collected, and after separation and purification, 30.0 kg / h of BDO with a purity greater than 99.9%, 22.0 kg / h of by-product THF with a purity greater than 99.5%, and 79.0 kg / h of wastewater are obtained. The recovered BDO is sent to the polymerization unit batching tank for recycling; DMT generates methanol through transesterification polycondensation, and after separation and purification, 255.0 kg / h of by-product methanol with a purity of 99.95% is obtained.

[0167] Final results: In Step 1, the maleic anhydride conversion rate is 99.88 mol%, the SAA yield is 99.10 mol%, and the by-product GBL yield is 0.81 mol%; in Step 2, the SAA conversion rate is 98.38 mol%, the BDO yield is 96.19 mol%, and the by-product THF yield is 2.38 mol%; in Step 3, based on the monomer feed amount, the PBST weight yield is 81.50 wt%, the by-product THF weight yield is 1.14 wt%, and the by-product methanol weight yield is 13.25 wt%; the weight yield of the whole process of producing PBST starting from maleic anhydride (based on maleic anhydride): the total PBST yield is 125.44 wt%, the total by-product THF yield is 2.94 wt%, and the by-product GBL yield is 0.70 wt%; based on the total amount of organic raw materials input, the total PBST yield is 77.39 wt%, and the by-product wastewater yield is 11.65 wt%. After testing, the various performance indicators of the produced PBST are good: the melt index is 25.6 g / 10 min, the acid value is 10.2 mol / t, the weight-average molecular weight is 16.8×10 4 , the melting point is 106°C, and the tensile strength is 41 MPa.

[0168] Comparative Example 3

[0169] The gaseous phase materials for the polycondensation of SAA and BDO to form PBS are not recycled

[0170] The production process, catalyst, and operating conditions are the same as those in Example 27, except that: in step 3, the gaseous phase materials in the polycondensation reaction are not recycled; the obtained PBS production rate is 988.2 kg / h, and a total of 184.8 kg / h of the condensed gaseous phase effluent is collected, which contains BDO (10.5 kg / g), THF (59.3 kg / h), water (106.3 kg / h), and small amounts of succinic acid (6.8 kg / h), n-butanol (0.5 kg / h), and trifluoromethanesulfonic acid (1.5 kg / h).

[0171] Final result: The weight yield of PBS based on the monomer feed amount in step 3 is 84.39 wt%; the weight yield of the whole process of producing PBS starting from maleic anhydride (based on maleic anhydride) is 79.06 wt%; the performance indexes of the produced PBS are: melt index 29.2 g / 10 min, acid value 35.0 mol / t, weight average molecular weight 13.2×10 4 , melting point 98 °C, tensile strength 38 MPa.

[0172] Comparative Example 4

[0173] The gaseous phase materials for the polycondensation of SAA, BDO, and adipic acid to form PBSA are not recycled

[0174] The production process, catalyst, and operating conditions are the same as those in Example 32, except that: in step 3, the gaseous phase materials in the polycondensation reaction are not recycled; the obtained PBSA production rate is 1216.0 kg / h, and a total of 222.9 kg / h of the condensed gaseous phase effluent is collected, which contains BDO (6.5 kg / g), THF (41.6 kg / h), water (167.5 kg / h), and small amounts of succinic acid (5.2 kg / h), n-butanol (0.6 kg / h), and trifluoromethanesulfonic acid (1.5 kg / h).

[0175] Final result: The weight yield of PBS based on the monomer feed amount in step 3 is 84.64 wt%; the weight yield of the whole process of producing PBS starting from maleic anhydride (based on the total amount of organic raw materials input) is the weight yield of PBSA 79.28 wt%; the performance indexes of the produced PBSA are: melt index 28.3 g / 10 min, acid value 31.6 mol / t, weight average molecular weight 16.2×10 4 , melting point 93 °C, tensile strength 35 MPa.

[0176] The maleic anhydride conversion rates, molar yields of monomers SAA and BDO, polyester weight yield based on the total amount of organic raw materials input, and polyester performance indicators of the above Examples 27 to 33 and Comparative Examples 2 to 4 are summarized in Table 4. The actual acid-alcohol monomer ratio described in Table 4 refers to the molar ratio of the acid monomer to the alcohol monomer actually participating in the polymerization reaction, and the relative amount of the acid monomer refers to the percentage based on the absolute feed amount of the acid monomer in Example 27.

[0177] Table 4 Maleic anhydride conversion rates, molar yields of monomers SAA and BDO, polyester weight yield based on the total amount of organic raw materials input, and polyester performance indicators of Examples 27 to 33 and Comparative Examples 2 to 4

[0178]

[0179] Comparing Examples 27 and 28 with Comparative Example 3, it was found that the same starting material maleic anhydride, the same dosage, the same catalyst, and the same operation process were used. The differences were as follows: The operations in Steps 1 to 3 of Example 27 were exactly the same as those of Comparative Example 3. Only in the polycondensation process of Step 3, Example 27 adopted the BDO material recycling process, while the BDO material in Comparative Example 3 was not recycled. That is, although the feed amounts of SAA and BDO monomers were the same, the molar ratios of the monomers actually participating in the polymerization reaction were different. For Example 27, SAA:BDO = 1.00:1.24, while for Comparative Example 3, SAA:BDO = 1.00:1.13. As a result, the excess of BDO in Example 27 was more than that in Comparative Example 3, and the feed amount and the amount actually participating in the polymerization reaction of the SAA monomer were the same. Therefore, their yields were comparable (79.90% and 79.06% respectively), but there were significant differences in the performance of the polyester product PBS. The melt index of Comparative Example 3 was 8.0 g / 10 min (37.7%) higher than that of Example 27, the acid value was 14.5 mol / t (70.7%) higher, and the weight-average molecular weight Mw was 3×10 4(18.5%), the melting point is 15 °C lower (13.3%), and the tensile strength is 7.0 MPa lower (15.6%). The difference between Example 28 and Example 27 and Comparative Example 3 is that the ratio of SAA used as an acid monomer to that used for hydrogenation to produce BDO is adjusted. In the recycled material for the polycondensation reaction, in addition to BDO, the THF generated throughout the process is also recycled. The amount of SAA used for the polycondensation reaction is 1.09 times that of Example 27 and Comparative Example 3. At the same time, the ratio of the alcohol monomer to the acid monomer participating in the actual reaction is kept the same as that of Example 27. As a result, the yield of the polyester product PBS is increased to 87.12% (9.0% higher than Example 27 and 10.2% higher than Comparative Example 3). The performance indexes are between those of Example 27 and Comparative Example 3, but closer to Example 27. The melt index of Comparative Example 3 is 7.7 g / 10 min (35.8%) higher than that of Example 28, the acid value is 9.5 mol / t (37.2%) higher, and the weight-average molecular weight Mw is 2×10 4 (13.2%), the melting point is 14 °C lower (12.5%), and the tensile strength is 5.0 MPa lower (11.6%).

[0180] In addition, in the case of adding a third monomer, compared with Example 32 with recycled material, Comparative Example 4 without recycled material is basically similar to Comparative Example 3 and Example 27. The polyester yields are close (79.83% and 79.28% respectively), but the polyester quality deteriorates, especially the acid values differ significantly, with the acid value being 12.1 mol / t (62.1%) higher.

[0181] Therefore, not recycling the gas-phase material of the polycondensation reaction will affect the yield and product quality of the polyester (PBS or PBSX): the melt index and acid value increase significantly, and the weight-average molecular weight, melting point, and tensile strength also decrease. This is because without recycled material, the molar ratio of the alcohol and acid monomers actually participating in the polycondensation reaction is relatively low. Due to the chemical equilibrium in the esterification reaction, the esterification reaction is incomplete under normal pressure or slightly positive pressure. At the same time, the polycondensation and final polymerization reactions are carried out under negative pressure, which will cause some monomers and oligomers, especially alcohol monomers, to be pulled out of the reaction system by vacuum, resulting in the actual alcohol-acid molar ratio being lower than the feed ratio. The ultimate result is a decrease in the degree of polymerization, an increase in the proportion of oligomers, and an increase in the proportion of terminal carboxyl groups, which in turn leads to an increase in the melt index and acid value, a decrease in the molecular weight, and a deterioration in the thermal and mechanical properties.

[0182] In summary, as can be seen from the results of the examples and comparative examples in Tables 1 to 4, by using maleic anhydride, a cheap and readily available single basic organic raw material, and adopting a special production process with GBL and THF as solvents for the two-step hydrogenation reaction respectively, two key monomers SAA and BDO for polyester synthesis can be efficiently produced. Furthermore, by adopting an efficient polymerization process (pressure esterification, negative pressure prepolymerization, vacuum final polymerization and gas-phase material circulation), and using the by-products GBL and THF as comonomers or adding a third monomer externally, PBS-based polyester products with excellent properties can be synthesized. In addition, by selecting GBL and THF, which are the same substances as the small amount of by-products generated in the hydrogenation reaction, as solvents for the hydrogenation reaction, it is possible to avoid introducing new impurities and separation and circulation energy consumption to the system by selecting an externally added solvent. At the same time, a small amount of by-products (the total yield of GBL + THF does not exceed 5% under optimized conditions in the two-step hydrogenation reaction) can also supplement the losses in the solvent circulation process, achieve internal balance in the system and improve the raw material utilization rate. It is very necessary to collect the gas-phase materials in the cyclic condensation reaction, which can increase the actual alcohol / acid (anhydride) ratio in the polymerization reaction process, improve both the polyester yield and the quality of the polyester product.

[0183] The above are only the preferred embodiments of the present invention and are not intended to limit the present invention. Any modifications, equivalent replacements, improvements, etc. made within the spirit and principles of the present invention shall be included in the protection scope of the present invention.

Claims

1. A method for producing polybutylene succinate materials using maleic anhydride as a single raw material, characterized in that, It includes the following steps: S1. Selective hydrogenation of maleic anhydride to prepare succinic anhydride; S2. Selective hydrogenation of a part of the succinic anhydride obtained in step S1 to prepare 1,4-butanediol; S3. The remaining succinic anhydride obtained in step S1, 1,4-butanediol obtained in step S2, with or without the addition of a third monomer, are mixed and then subjected to ring-opening polycondensation to synthesize poly(butylene succinate); Among them, the catalyst used in the hydrogenation reaction in step S1 is a metal palladium supported catalyst, and the process conditions for the hydrogenation reaction are: temperature 40-90 °C, pressure 0.2-2.0 MPa, weight hourly space velocity of the feed is 0.1-2.0 h -1 , and the molar ratio of hydrogen to anhydride is 1-30; the catalyst used in the hydrogenation reaction in step S2 is a copper-based catalyst, and the process conditions for the hydrogenation reaction are: temperature 240-340 °C, pressure 2.0-10.0 MPa, weight hourly space velocity of the feed 0.1-5.0 h -1 and the molar ratio of hydrogen to anhydride is 20-200; the mass ratio of the succinic anhydride prepared in step S1 used for preparing 1,4-butanediol in step S2 and the succinic anhydride used for synthesizing polybutylene succinate in step S3 is (0.8-2.5):1; the third monomer is selected from at least one of polybasic acids and esters, cyclic anhydrides, polyhydric alcohols, cyclic ethers, hydroxy acids and esters, or lactones.

2. The method according to claim 1, wherein In the above step S1, the process for the selective hydrogenation of maleic anhydride to prepare succinic anhydride includes the following steps: S11. Dissolve maleic anhydride in the solvent γ-butyrolactone to prepare a maleic anhydride solution as the feed, and after pressurization and preheating, feed it into a hydrogenation reactor for hydrogenation reaction; S12. Carry out gas-liquid separation on the reaction product after the hydrogenation reaction, recycle the separated gaseous hydrogen to the hydrogenation reactor, and send the liquid-phase material to a separation and purification system, and sequentially carry out light-component removal, γ-butyrolactone removal and succinic anhydride purification to obtain high-purity succinic anhydride; all the separated γ-butyrolactone is recycled as the solvent for preparing the feed maleic anhydride solution, or part of it is recycled as the solvent, and the remaining part is used as the third monomer for synthesizing poly(butylene succinate).

3. The method according to claim 1, characterized in that, In the above step S1, the hydrogenation reactor used for the hydrogenation reaction adopts a gas-liquid-solid slurry bed or a fixed-bed reactor, preferably a fixed-bed reactor, and more preferably a trickle fixed-bed reactor; The catalyst used for the hydrogenation reaction is selected from Pd / γ-Al2O3 or Pd-D / γ-Al2O3 catalysts, where D = Ni or / and Cu; The solvent used for the maleic anhydride solution is γ-butyrolactone, and the mass concentration of maleic anhydride in the feed is 15-50%, preferably 18-40%, and more preferably 20-30%; The process conditions for the hydrogenation reaction are as follows: temperature 45 - 80 °C, pressure 0.3 - 1.5 MPa, weight hourly space velocity of the feed 0.2 - 1.5 h -1 , molar ratio of hydrogen to anhydride 2 - 20; preferably, temperature 50 - 70 °C, pressure 0.5 - 1.0 MPa, weight hourly space velocity of the feed 0.4 - 1.0 h -1 , molar ratio of hydrogen to anhydride 5 - 15.

4. The method according to claim 1, wherein In the above step S2, the process for the hydrogenation of succinic anhydride to prepare 1,4-butanediol includes the following steps: S21. Dissolve succinic anhydride in tetrahydrofuran to prepare a succinic anhydride solution as the feed, and after pressurization, preheating and gasification, mix it with hydrogen and feed it into a hydrogenation reactor for hydrogenation reaction; S22. Carry out gas-liquid separation on the reaction product after the hydrogenation reaction, return the separated gaseous hydrogen to the hydrogenation reactor for continued use after pressurization and preheating, and send the liquid-phase material to a separation and purification system, and sequentially carry out tetrahydrofuran removal, dehydration and 1,4-butanediol purification to obtain high-purity 1,4-butanediol; all the tetrahydrofuran is recycled as the solvent for preparing the feed succinic anhydride solution, or part of it is recycled as the solvent, and the remaining part is used as the third monomer for synthesizing poly(butylene succinate).

5. The method according to claim 1, wherein In the above step S2, the hydrogenation reactor used for the hydrogenation reaction adopts a gas-solid fixed-bed reactor, preferably an isothermal fixed-bed or an adiabatic fixed-bed reactor, and more preferably a tubular isothermal fixed-bed or an inter-stage heat-removing adiabatic fixed-bed reactor; The copper-based catalyst is selected from CuZnZrE or CuZnAlG / SiO2 catalysts, where E and G are alkaline earth metal or rare earth metal elements; preferably CuZnZrLa or CuZnAlCe / SiO2 catalysts; The mass concentration of succinic anhydride in the feed succinic anhydride solution is 10-40%, preferably 15-35%, and more preferably 20-30%; The hydrogenation reaction process conditions are as follows: temperature 250 - 320 °C, pressure 3.5 - 8.5 MPa, weight hourly space velocity of the feed 0.25 - 2.0 h -1 and molar ratio of hydrogen to anhydride 30 - 150; preferably temperature 260 - 300 °C, pressure 5.0 - 7.5 MPa, weight hourly space velocity of the feed 0.5 - 1.0 h -1 and molar ratio of hydrogen to anhydride 50 - 100.

6. The method according to claim 5, characterized in that In the step S2, the catalyst for the hydrogenation reaction is Cu a Zn b Zr c La d , where a = 43 - 48, b = 23 - 28, c = 23 - 28, d = 2 - 7; or, The catalyst for the hydrogenation reaction is xCu a Zn b Al c Ce d / ySiO2 catalyst, where x / (x + y) = 70 - 80%, a = 45 - 55, b = 23 - 28, c = 23 - 28, d = 8 - 12.

7. The method according to claim 1, wherein In the step S3, the technological process of synthesizing poly(butylene succinate) by ring-opening polycondensation includes the following steps: preparing a slurry by mixing succinic anhydride obtained in step S1, 1,4-butanediol obtained in step S2, with or without a third monomer, and an esterification catalyst in proportion, and feeding the slurry into an esterification reactor for pressure ring-opening esterification reaction; removing small molecules from the esterification reaction product under reduced pressure, adding a polymerization catalyst, and then feeding it into a prepolymerization reactor for negative pressure prepolymerization reaction; feeding the prepolymer into a final polymerization reactor for vacuum final polycondensation reaction to obtain a poly(butylene succinate) polyester, and then obtaining poly(butylene succinate) polyester pellet products through underwater cooling and pelletizing.

8. The method according to claim 7, wherein In the step S3, the molar ratio of raw material monomers is succinic anhydride:1,4-butanediol:third monomer = 1.00:(0.50 - 3.75):(0 - 2.00); For the ring-opening esterification reaction: a vertical reactor is used, the ring-opening esterification catalyst is trifluoromethanesulfonic acid, and the dosage of the ring-opening esterification catalyst is 0.01 - 1.00% of the mass of succinic anhydride, preferably 0.05 - 0.50%; the ring-opening esterification reaction conditions are a temperature of 150 - 200 °C, a pressure of 0.10 - 0.50 MPa, and a residence time of the material of 40 - 150 min, preferably a temperature of 160 - 180 °C, a pressure of 0.15 - 0.25 MPa, and a residence time of the material of 60 - 120 min; For the prepolymerization reaction: a vertical reactor is used, the polymerization catalyst is tetrabutyl titanate, and the dosage is 0.01 - 0.50% of the mass of succinic anhydride, preferably 0.05 - 0.10%; the prepolymerization reaction conditions are a temperature of 180 - 240 °C, a pressure of 5 - 90 kPa, and a residence time of the material of 20 - 60 min, preferably a temperature of 200 - 220 °C, a pressure of 10 - 50 kPa, and a residence time of the material of 30 - 45 min; For the final polycondensation reaction: a horizontal reactor is used, and the final polycondensation reaction conditions are a temperature of 200 - 260 °C, a pressure of 10 - 200 Pa, and a residence time of the material of 60 - 150 min, preferably a temperature of 220 - 240 °C, a pressure of 50 - 90 Pa, and a residence time of the material of 90 - 120 min.

9. The method according to claim 1, wherein In the step S3, when no third monomer is added, the molar ratio of raw material monomers is succinic anhydride:1,4-butanediol = 1.0:(1.10 - 1.35); When a third monomer is added and the third monomer is selected from polyacids or polyacid esters or cyclic anhydrides of polyacids, the molar ratio of raw material monomers is succinic anhydride:1,4-butanediol:third monomer = 1.00:(1.15 - 2.50):(0.05 - 1.00); When a third monomer is added and the third monomer is selected from polyols or cyclic ethers of polyols or hydroxy acids or hydroxy acid esters or lactones, the molar ratio of raw material monomers is succinic anhydride:1,4-butanediol:third monomer = 1.00:(0.75 - 1.25):(0.05 - 0.55).

10. The method according to claim 1, characterized in that, The third monomer is at least one of polyacids and esters, cyclic anhydrides, polyols, cyclic ethers, hydroxy acids and esters, or lactones; among them, The polybasic acid is selected from C4-C 22 aliphatic polybasic acids, C8-C 16 aromatic polybasic acids or C6-C 10 heterocyclic polybasic acids, preferably 1,4-butanedioic acid, 1,5-pentanedioic acid, 1,6-hexanedioic acid, 1,10-decanedioic acid, 1,4-cyclohexanedicarboxylic acid, terephthalic acid, isophthalic acid, 1,4-naphthalenedicarboxylic acid, 2,6-naphthalenedicarboxylic acid or 2,5-furandicarboxylic acid; The polybasic acid ester is selected from C4-C 22 monoesters or diesters of aliphatic polybasic acids, C8-C 16 monoesters of aromatic polybasic acids, or diesters or C6-C 10 monoesters or diesters of heterocyclic polybasic acids, preferably dimethyl esters of 1,4-succinic acid, 1,5-glutaric acid, 1,6-adipic acid, 1,10-sebacic acid, 1,4-cyclohexanedicarboxylic acid, terephthalic acid, isophthalic acid, 1,4-naphthalenedicarboxylic acid or 2,5-furandicarboxylic acid; The cyclic anhydride of the polybasic acid is selected from glutaric anhydride, adipic anhydride, phthalic anhydride, trimellitic anhydride or pyromellitic dianhydride; The polyol is selected from C2-C 22 aliphatic polyols, C8-C 16 aromatic polyols or C6-C 10 heterocyclic polyols, preferably ethylene glycol, 1,3-propanediol, 1,5-pentanediol, 1,6-hexanediol, 1,10-decanediol, 2-methyl-1,3-propanediol, neopentyl glycol, trimethylolethane, trimethylolpropane, pentaerythritol, xylitol, sorbitol, 1,4-cyclohexanediol, 1,4-cyclohexanedimethanol, terephthalyl alcohol or 2,5-furandimethanol; The cyclic ether of the polyhydric alcohol is selected from C2-C5 aliphatic cyclic ethers, preferably ethylene oxide, propylene oxide, epichlorohydrin, propylene glycol, tetrahydrofuran, tetrahydrofurfuryl alcohol or tetrahydropyran; The hydroxy acid or ester is selected from C2-C 10 hydroxy fatty acid or ester, preferably glycolic acid, 2-hydroxypropionic acid, 3-hydroxypropionic acid, 3-hydroxybutyric acid, 4-hydroxybutyric acid, 5-hydroxypentanoic acid, 6-hydroxyhexanoic acid or their methyl esters; The lactone is selected from β-propiolactone, γ-butyrolactone, γ-valerolactone, δ-valerolactone or ε-caprolactone.

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