阅读说明：本技术 一种液相两段加氢生产丁二酸的方法 (Method for producing succinic acid by liquid-phase two-stage hydrogenation ) 是由 唐明兴 宋晓玲 李学宽 周军 李国栋 司江坤 夏伦超 周立公 于 2020-03-18 设计创作，主要内容包括：本发明公开了一种液相两段加氢生产丁二酸的新方法,为有效避免飞温和副反应,加氢部分分两段进行,其具体步骤为：原料与氢气在预混合器中进行充分混合；混合物料从第一催化床层上部进入和催化剂接触进行预加氢反应；从第一反应床层出来物料从顶部进入第二反应床层,向下流经催化剂进行主加氢反应；反应后物料进入气液分离器分离得到未反应氢气和产物,氢气经循环氢压缩机循环再利用,加氢产物进入结晶槽将丁二酸和溶剂进行分离,溶剂水重复利用。本发明采用两段加氢工艺,通过控制反应温度、接触时间、母液浓度、催化剂和级配工艺等关键技术解决现有技术存在的副反应严重、催化剂稳定性差及反应系统堵塞等技术难题,丁二酸产品纯度可满足食品级、医药级和聚合级的需求。(The invention discloses a novel method for producing succinic acid by liquid-phase two-stage hydrogenation, which is characterized in that in order to effectively avoid runaway temperature and side reaction, the hydrogenation part is carried out in two stages, and the method comprises the following specific steps: fully mixing the raw materials with hydrogen in a premixer; the mixed material enters from the upper part of the first catalytic bed layer and contacts with a catalyst to carry out a pre-hydrogenation reaction; the material from the first reaction bed layer enters a second reaction bed layer from the top, and flows downwards through a catalyst to carry out a main hydrogenation reaction; and the reacted material enters a gas-liquid separator for separation to obtain unreacted hydrogen and a product, the hydrogen is recycled by a recycle hydrogen compressor, the hydrogenated product enters a crystallization tank for separation of succinic acid and the solvent, and the solvent water is recycled. The invention adopts two-stage hydrogenation process, solves the technical problems of serious side reaction, poor catalyst stability, reaction system blockage and the like in the prior art by controlling key technologies such as reaction temperature, contact time, mother liquor concentration, catalyst, grading process and the like, and the purity of the succinic acid product can meet the requirements of food grade, pharmaceutical grade and polymerization grade.)

1. A method for producing succinic acid by liquid phase hydrogenation is characterized in that a hydrogenation part is carried out in two sections, and the method comprises the following specific steps:

(1) uniformly mixing the raw materials and hydrogen in a premixer;

(2) the obtained uniformly mixed material enters a first section reaction bed layer from the top, and flows downwards through a catalyst to carry out a pre-hydrogenation reaction;

(3) the material from the first reaction bed layer enters a second reaction bed layer from the top, and flows downwards through a catalyst to carry out a main hydrogenation reaction;

(4) the material from the second reaction bed layer enters a gas-liquid separator for gas-liquid separation, a liquid product is obtained at the lower part, and unreacted hydrogen is recycled from the upper part through a recycle hydrogen compressor;

(5) and (4) cooling and crystallizing the liquid product obtained in the step (4) in a crystallization tank to obtain a solid product, and recycling the residual mother liquor.

2. The method according to claim 1, wherein the raw material in the step (1) is an aqueous solution containing 5-60% by weight of maleic acid, and the temperature of the raw material is controlled to be 30-100 ℃.

3. The method of any one of claims 1 to 2, wherein the first-stage reaction temperature in the step (2) is 30 to 150 ℃, the reaction pressure is 0.5 to 10.0MPa, and the mass space velocity is 0.2 to 20h^-1The volume ratio of the hydrogen raw material is 100-2000.

4. The method as claimed in any one of claims 1 to 3, wherein the second stage reaction temperature in step (3) is 50 to 250 ℃, the reaction pressure is 0.5 to 10.0MPa, and the mass space velocity is 0.2 to 20h^-1The volume ratio of the hydrogen raw material is 100-2000.

5. The process according to any one of claims 1 to 4, wherein the first reaction bed and the second reaction bed in step (2) and step (3) are in two reactors or in the upper and lower parts of the same reactor, respectively, and the reactors are trickle bed reactors.

6. The method according to any one of claims 1 to 5, wherein the catalyst loading ratio of the first reaction bed to the second reaction bed in the steps (2) and (3) is 1: 0.1 to 10.

7. The method according to any one of claims 1 to 6, wherein the catalyst used in the first reaction bed and the second reaction bed can be the same catalyst or different catalysts; different catalysts are preferred.

8. The process according to any one of claims 1 to 7, characterized in that the catalyst has the following technical characteristics: the used catalyst is an acid-resistant carrier loaded with metals such as Ni, Pt, Pd, Ir, Ru, Rh and the like; the catalyst has hydrophilicity, and the contact angle of the catalyst with water is less than 60 degrees; the acid content of the catalyst is 0.01-2.0 mmol NH₃(ii)/g; the ratio of the pore volume of the catalyst with a pore diameter of less than 1nm to the total pore volume is less than 50%.

9. The method according to any one of claims 1 to 8, wherein the temperature of the separator in the step (4) is controlled to 50 to 150 ℃.

10. The method as claimed in any one of claims 1 to 9, wherein the temperature of the crystallization tank in the step (5) is controlled to be-10 to 30 ℃.

Technical Field

The invention discloses a novel method for producing succinic acid, and particularly relates to a novel method for producing succinic acid by liquid-phase hydrogenation of maleic acid aqueous solution.

Technical Field

Succinic acid is an important organic chemical raw material and intermediate, is widely applied to the environmental protection industry, the food industry, the chemical industry, the pharmaceutical industry and the like, and has good application prospect. The industrial technology comprises an electrolytic reduction method, a biological fermentation method and a catalytic hydrogenation method, wherein the biological fermentation method is mainly used abroad, the electrolytic reduction method is mainly used domestically, but the catalytic hydrogenation method has a better development prospect. The existing catalytic hydrogenation process takes maleic anhydride as a raw material, has harsh reaction conditions and high requirements on catalysts and equipment. Therefore, a green synthesis process of succinic acid needs to be developed as soon as possible.

In recent years, with the problem of environmental pollution caused by plastic wastes, the development of degradable bioplastics has become a hot point of research, and among them, polybutylene succinate (PBS) is considered as one of the best comprehensive properties among many biodegradable plastics, and is polymerized from succinic acid and 1, 4-butanediol by a direct esterification method, an ester exchange method, a chain extension method, and the like. At present, the production capacity of PBS and copolymers thereof in China is about 10 ten thousand tons/year, and the demand of PBS in China is estimated to reach 300 ten thousand tons/year as far as 2020, and meanwhile, the demand of succinic acid for producing PBS also reaches more than 180 ten thousand tons/year. The succinic acid production capacity restricts the development of the PBS industry, and the exploration of a high-efficiency and environment-friendly succinic acid preparation method is still the key research point in the next years.

Chinese patent CN103570650B discloses a process for continuously producing succinic anhydride and succinic acid by catalytic hydrogenation of maleic anhydride, which uses one or more mixed organic solvents to dissolve maleic anhydride, uses supported Ni/Cu as a catalyst, and adopts a two-stage hydrogenation reactor to carry out reaction, wherein the first-stage hydrogenation reactor is a fixed bed reactor in which hydrogen and reaction liquid enter and exit from below, and the second-stage hydrogenation reactor is a trickle bed reactor in which hydrogen and reaction liquid both enter and exit from below. The method has the problems of loss of catalyst components, high production cost and environmental pollution, and the reaction is difficult to effectively transfer heat for high-concentration raw materials.

Chinese patent CN101844976B discloses a method for preparing succinic acid by catalytic hydrogenation, which uses one or more of maleic anhydride aqueous solution, fumaric acid aqueous solution or maleic acid aqueous solution as raw material, one or more of load type VIII group metals Fe, Co, Ni, Pd, Pt, Ru, Rh and Ir as catalyst, and adopts fixed bed hydrogenation process, the conversion rate of raw material and the selectivity of succinic acid reach more than 99%, and the purity of product reaches more than 99.5%. Although the method takes water as a solvent, the process flow is simple, the energy consumption is low, and the catalyst component is easy to lose because the reaction system is acidic, so that the production cost is increased.

Chinese patent CN102417445B discloses a method for synthesizing succinic acid from maleic acid, which uses aqueous solution of maleic acid or maleate as raw material, uses supported palladium, platinum, ruthenium or nickel as active component, uses acidic resin, activated carbon and silicon dioxide as carrier, and adopts fixed bed hydrogenation process.

Chinese patent CN104926643B discloses a method for producing succinic acid, which adopts a tubular reactor, hydrogen is injected into a solution containing raw materials through a hole with the average pore diameter of nanometer size before reaction, firstly, a hydrogen-containing solution is obtained, then the solution is in contact reaction with a catalyst in the tubular reactor, the conversion rate of the raw materials and the selectivity of the succinic acid are both improved, and the purity of the product reaches 99.9 percent. Although the method improves the hydrogenation reaction efficiency, improves the effective treatment capacity of the catalyst and reduces the volume of the reactor, the method does not consider that the nano-sized micropores can be blocked by impurities in the raw materials, and the cleaning work after the blockage of the micropores is more complicated.

Chinese patent CN101735182B discloses a process for continuously producing succinic anhydride by maleic anhydride hydrogenation, which adopts a trickle bed reactor, after the maleic anhydride solution is hydrogenated, the maleic anhydride solution is shunted by a shunting ratio of 1/5-1/2, a part of reaction liquid is subjected to a rectification stage, the solvent is recycled, and other reaction liquid is mixed with the raw material, and the mixture is returned to the reactor after heat exchange by a heat exchanger. Although the method solves the problem of strong heat release in the preparation of succinic anhydride by maleic anhydride hydrogenation and the solvent is recycled, the method adopts partial reaction liquid to be mixed with the raw material, so that the problem of reducing the reaction heat is actually solved only by reducing the concentration of the raw material, and the problem is not solved fundamentally.

In summary, the prior art has disadvantages such as high catalyst cost, harsh reaction conditions, loss of catalyst components, high product price, severe pollution in the production process, and special requirements for the design and material of the reactor, which seriously hinders the large-scale synthesis and application of downstream PBS. Therefore, the development of a succinic acid production technology with low cost, low energy consumption, low pollution and simple flow has important significance for promoting the development of the plastic industry to green environmental protection.

Disclosure of Invention

The hydrogenation of maleic anhydride belongs to a strong exothermic reaction, and the temperature of a gas phase hydrogenation reaction is not well controlled, so that temperature runaway or a large amount of byproducts are easily caused. The production cost of the dissolving process using the organic solvent is high, and the organic solvent has great harm to operators and the environment. Water has obvious advantages as a green environment-friendly solvent, but the reaction temperature rise is still very large, which can cause the rapid inactivation of the catalyst or serious side reaction; the succinic acid and the fumaric acid in the product have low solubility in water, so that equipment or pipelines are easily blocked, and the safety production is influenced; byproducts in the circulating mother liquor can accumulate and affect the long-term running stability of the catalyst. Aiming at the defects of the prior art, the invention aims to provide an improved novel method for producing succinic acid by directly hydrogenating a maleic acid liquid phase.

The invention takes maleic anhydride/maleic acid and hydrogen as raw materials, water as a solvent, and the hydrogenation part is carried out in two sections, and the specific steps are as follows:

(1) uniformly mixing the raw materials and hydrogen in a premixer;

(2) the obtained uniformly mixed material enters a first section reaction bed layer from the top, and flows downwards through a catalyst to carry out a pre-hydrogenation reaction;

(3) the material from the first reaction bed layer enters a second reaction bed layer from the top, and flows downwards through a catalyst to carry out a main hydrogenation reaction;

(4) the material from the second reaction bed layer enters a gas-liquid separator for gas-liquid separation, a liquid product is obtained at the lower part, and unreacted hydrogen is recycled from the upper part through a recycle hydrogen compressor;

(5) and (4) cooling and crystallizing the liquid product obtained in the step (4) in a crystallization tank to obtain a solid product, and recycling the residual mother liquor.

Wherein the raw material in the step (1) is an aqueous solution containing 5-60% by mass of maleic acid, and the temperature of the raw material is controlled to be 30-100 ℃.

The first stage reaction temperature in the step (2) is 30-150 ℃, the reaction pressure is 0.5-10.0 MPa, and the mass space velocity is 0.2-20 h^-1The volume ratio of the hydrogen raw material is 100-2000.

The second-stage reaction temperature in the step (3) is 50-250 ℃, the reaction pressure is 0.5-10.0 MPa, and the mass space velocity is 0.2-20 h^-1The volume ratio of the hydrogen raw material is 100-2000.

And (3) the first reaction bed layer and the second reaction bed layer are respectively arranged in two reactors or in the upper part and the lower part of the same reactor. The reaction temperature can be controlled by adopting the modes of heat exchange, cold charge introduction and the like between the first reaction bed layer and the second reaction bed layer, so that the occurrence of runaway temperature and side reaction is avoided. The reactor is a trickle bed reactor. The ratio of the catalyst loading of the first reaction bed layer to the second reaction bed layer is 1: 0.1 to 10. First reaction bed and second reactionThe catalyst used in the bed layer can be the same catalyst or different catalysts; different catalysts are preferred. The used catalyst is an acid-resistant carrier loaded with metals such as Ni, Pt, Pd, Ir, Ru, Rh and the like; the catalyst has hydrophilicity, and the contact angle of the catalyst with water is less than 60 degrees; the acid content of the catalyst is 0.01-2.0 mmol NH₃(ii)/g; the ratio of the pore volume of the catalyst with a pore diameter of less than 1nm to the total pore volume is less than 50%.

And (4) controlling the temperature of the separator in the step (4) to be 50-150 ℃.

And (5) controlling the temperature of the crystallization tank to be-10-30 ℃.

The raw material of the invention can be maleic anhydride, maleic acid, fumaric acid and the mixture thereof.

The process can be used for obtaining food-grade, medical-grade and polymer-grade succinic acid products, and can flexibly change production tasks according to market demands.

THE ADVANTAGES OF THE PRESENT INVENTION

The novel method for producing the succinic acid by liquid-phase hydrogenation of the maleic acid, which is provided by the invention, takes water as a solvent, and is green and environment-friendly in process. The invention can effectively control the temperature and concentration of each unit, solves the technical problems of serious side reaction, reaction system blockage and the like in the prior art, and ensures that the purity of the succinic acid product can meet the requirements of food grade, pharmaceutical grade and polymer grade. The invention adopts the trickle bed reactor, has mild reaction conditions and simple operation, is suitable for continuous mass industrial production and reduces the operation cost.

Drawings

FIG. 1 is a stability experiment, wherein it is the maleic acid conversion of example 4; x is the succinic acid selectivity of example 4; comparative example 4 maleic acid conversion; tangle-solidup is the succinic acid selectivity of comparative example 4.

Detailed Description

The invention is further illustrated, but not limited, by the following examples. The raw material used in the present invention is maleic acid, maleic anhydride, fumaric acid or a mixture thereof may be used, and maleic acid is used as the raw material in the examples.

The temperature and concentration of each unit of the invention need to be strictly controlled, and the occurrence of side reaction and the blockage of a reaction system are avoided.

The catalyst used in the process of the invention has the models of A, B, C, D and E, and the composition and properties of the catalyst are shown in Table 1.

The invention is further illustrated and described below with reference to examples.