CN111689846B - Process for producing succinic acid by aqueous phase hydrogenation - Google Patents
Process for producing succinic acid by aqueous phase hydrogenation Download PDFInfo
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- C07C51/00—Preparation of carboxylic acids or their salts, halides or anhydrides
- C07C51/083—Preparation of carboxylic acids or their salts, halides or anhydrides from carboxylic acid anhydrides
- C07C51/087—Preparation of carboxylic acids or their salts, halides or anhydrides from carboxylic acid anhydrides by hydrolysis
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- C—CHEMISTRY; METALLURGY
- C07—ORGANIC CHEMISTRY
- C07C—ACYCLIC OR CARBOCYCLIC COMPOUNDS
- C07C51/00—Preparation of carboxylic acids or their salts, halides or anhydrides
- C07C51/347—Preparation of carboxylic acids or their salts, halides or anhydrides by reactions not involving formation of carboxyl groups
- C07C51/36—Preparation of carboxylic acids or their salts, halides or anhydrides by reactions not involving formation of carboxyl groups by hydrogenation of carbon-to-carbon unsaturated bonds
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- C—CHEMISTRY; METALLURGY
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- C07C—ACYCLIC OR CARBOCYCLIC COMPOUNDS
- C07C51/00—Preparation of carboxylic acids or their salts, halides or anhydrides
- C07C51/42—Separation; Purification; Stabilisation; Use of additives
- C07C51/43—Separation; Purification; Stabilisation; Use of additives by change of the physical state, e.g. crystallisation
Abstract
The invention discloses a novel process for producing succinic acid by aqueous phase hydrogenation, which comprises a stirring kettle, a raw material tank, a raw material and hydrogen premixer, a hydrogenation reactor, a hydrogen distribution pipe, a gas-liquid separation tank, a crystallization tank and the like. The process comprises the steps of uniformly mixing maleic anhydride and water in a stirring kettle according to a certain proportion, feeding the mixture into a raw material tank, conveying the raw material into a pre-mixer through a raw material pump, fully mixing the raw material with hydrogen, feeding the mixed material into a reactor from the upper part of a hydrogenation reactor to be in contact reaction with a catalyst, and feeding the other strand of cold hydrogen into the reactor from 1/3-2/3 to play a role in adjusting the temperature of a catalyst bed layer. 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 solves the technical problems of serious side reaction, poor catalyst stability, reaction system blockage and the like in the prior art by controlling the temperature of each unit, a hydrogen distribution mode, adopting a high-activity high-selectivity catalyst and the like, and the purity of the succinic acid product can meet the requirements of food grade, pharmaceutical grade and polymerization grade.
Description
Technical Field
The invention discloses a novel process for producing succinic acid, and particularly relates to a novel process for producing succinic acid by maleic anhydride aqueous phase hydrogenation.
Technical Field
With the progress of society, the plastic product industry is continuously developed, and more plastic products are widely applied in the aspects of industry, agriculture, medicine, daily necessities and the like. However, since plastics are difficult to degrade, a large amount of plastic waste remains in farmlands, rivers, lakes, pastures, and the like, resulting in "white pollution". Especially, the non-degradable materials are produced and used in large quantities, which not only causes huge waste of resources, but also seriously pollutes and destroys the ecological environment, thus becoming the stumbling stone for sustainable economic development. The non-degradable plastic products are discarded at will, which causes serious harm to the ecological environment. The dioxin which is a substance with the highest toxicity seriously pollutes the air and damages the human health because of harmful gas generated by burning waste plastic products has carcinogenic effect, and can be decomposed at least in 15 months after entering the soil, thereby damaging the growth of plants and crops. The waste plastic products are buried in soil, which affects the absorption of nutrient and moisture by crops and plants, because the non-degradable plastic products take foamed polystyrene, polyethylene or polypropylene as raw materials, the molecular weight reaches over 2 ten thousand, and the natural decay and degradation takes over 200 years.
At present, China is a world-wide major for producing and consuming plastic products, and research, development, production and application of biodegradable plastics have important significance on sustainable development of the plastic industry. "white contamination" is a worldwide problem. At present, countries such as the United states, Japan, Germany and the like are vigorously developing true degradable plastics for protecting environment and soil, and the market prospect of the degradable Plastics (PBS) is wide. PBS can be obtained by polymerizing succinic acid and butanediol, the technology for producing 1, 4-butanediol by the current alkyne-aldehyde method is mature, the product price is lower, the succinic acid is mainly produced by an electrolytic method, the cost is high, and the large-scale application of the PBS is restricted. The catalytic hydrogenation method has the advantages of high conversion rate, high product purity, no obvious side reaction and the like, and is the most promising method for synthesizing the succinic acid. In particular to a liquid phase hydrogenation method using water as a solvent, which is a technology with industrial application potential due to the fact that the solvent is environment-friendly, low in price and easy to obtain.
Patent CN101844976A uses one or more of maleic anhydride aqueous solution, fumaric acid aqueous solution or maleic acid aqueous solution as raw material, uses one or more of Fe, Co, Ni, Pd, Pt, Ru, Rh, Ir as active component, uses one or more of silica, zirconia, activated carbon, titania or silicon carbide as carrier to prepare catalyst, obtains succinic acid aqueous solution through hydrogenation reaction, and obtains succinic acid product after cooling crystallization, filtration and drying. Patent CN 104926643a uses maleic anhydride and/or maleic acid as raw material, and injects hydrogen gas into the solution containing raw material through the pores with average pore diameter of nanometer size to obtain hydrogen-containing solution. The technology adopts an upward flow mode to be sent into a tubular reactor, and the hydrogen-containing solution is contacted with a catalyst with catalytic hydrogenation function filled in the tubular reactor to carry out hydrogenation reaction. Different from a downflow feeding mode adopted by a common fixed bed, the method can obtain higher raw material conversion rate and product selectivity, and can obtain succinic acid with the purity of 99.9 percent. Patent CN106861702A discloses a catalyst for directly synthesizing succinic acid by maleic anhydride aqueous phase hydrogenation, and a preparation method and application thereof, wherein the catalyst takes maleic anhydride aqueous solution as a raw material, the concentration of the raw material is 8-30 wt%, and carbon-coated nickel-copper CuNi/Al is adopted2O3The catalyst utilizes the hydrophobic material property of carbon to prevent the scouring of active components and Al of acidic aqueous solution2O3Corrosion of the carrier. However, these methods do not consider the influence of the by-product generated in the raw material dissolution process on the stability, the influence of the reaction heat effect on the catalyst stability, the effective control technique of the reaction heat, etc., and these patents do not have the number of stable operations for a long timeAccording to the method, no industrial report is found.
In summary, aiming at the technical problems of aqueous phase hydrogenation at present, it is necessary to develop a new technology to solve the restriction of by-products generated in the reaction process and reaction heat on the long-term stable operation of the system, develop a new technology for producing succinic acid with low cost, low energy consumption and simple flow, and have important significance for promoting the development of the plastic industry to green environmental protection.
Disclosure of Invention
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 reactions. 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; malic acid accumulates in the circulating water, causing a decrease in activity and selectivity. Aiming at the defects of the prior art, the invention aims to provide an improved novel process for producing succinic acid by directly hydrogenating a maleic anhydride aqueous phase, and solves the problems.
The invention takes maleic anhydride and hydrogen as raw materials and water as a solvent, and the production process comprises the following parts: the device comprises a stirring kettle, a raw material tank, a raw material and hydrogen premixing unit, a hydrogenation reactor, a hydrogen distribution pipe, a gas-liquid separation tank, a crystallization tank and the like. The specific process steps are as follows:
(1) the raw materials and water are mixed evenly in a stirring kettle according to a certain proportion.
(2) And (2) feeding the aqueous solution obtained in the step (1) into a raw material tank 2.
(3) The raw material in the raw material tank 2 is uniformly mixed with hydrogen gas 9 in the premixer 3.
(4) The mixture obtained in the step (3) enters from the top of the reactor 4.
(5) The material entering the reactor is fully contacted and reacted with the catalyst in the reactor.
(6) The material from the reactor 4 enters a gas-liquid separation tank 5 for gas-liquid separation, and a liquid product is obtained at the bottom and enters a crystallization tank 10. And cooling the materials to a certain temperature in the crystallization tank 10, crystallizing the succinic acid to obtain a product, and circulating the residual liquid back to the stirring kettle 1 for recycling.
(7) Unreacted hydrogen 6 is circulated by a circulating hydrogen compressor and mixed with new hydrogen 7 and then is divided into 8 and 9 by a hydrogen distribution pipe in proportion, the hydrogen 9 enters the premixer 3, and the hydrogen 8 enters the reactor from a certain height of the reactor.
Wherein the weight ratio of the maleic anhydride to the water in the step (1) is 2: 1-18 ℃, and controlling the temperature of the stirring kettle at 50-120 ℃. Maleic anhydride and water can generate hydrolysis reaction to release a large amount of heat, maleic acid can generate isomerization reaction under certain conditions to generate fumaric acid and malic acid, and the fumaric acid has low solubility in water and is easy to cause pipeline blockage; malic acid can be enriched in the aqueous phase, which affects catalyst stability and product purity. Therefore, the invention avoids the generation of fumaric acid and malic acid by controlling the adding amount of water and taking heat transfer measures.
And (3) controlling the temperature of the raw material tank in the step (2) to be 30-100 ℃.
And (3) the volume ratio of the hydrogen to the water solution is 100-1000. The hydrogen has low solubility in water, and the hydrogen-liquid hydrogen pre-mixing device is used for pre-mixing the hydrogen-liquid hydrogen, so that the gas-liquid two-phase mass transfer is enhanced, and the hydrogenation reaction is favorably carried out.
And (5) the hydrogenation reactor is a fixed bed reactor. The inlet temperature of the reactor is 30-100 ℃, the outlet temperature of the reactor is 50-200 ℃, the reaction pressure is 0.5-5.0 MPa, and the mass space velocity is 0.1-10 h-1The volume ratio of hydrogen to oil is 50-1000. The used catalyst is active carbon, alpha alumina, silicon oxide or silicon carbide and other acid-resistant carriers loaded with Ru, Rh, Pd, Pt, Au, Ag and other metals, and the mass percentage of the active components is 0.1-10%. The hydrogenation catalyst has the following technical characteristics: the catalyst consists of an active component and an acid-resistant in-vivo component; 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 (6) controlling the temperature of the separation tank to be 50-150 ℃. The temperature of the crystallization tank is controlled to be-10-30 ℃.
The volume ratio of the hydrogen 8 to the hydrogen 9 in the step (7) is 1: 1-10. The hydrogen 8 enters the reactor from the 1/3-2/3 positions, so that concentrated heat release is avoided, the temperature of a catalyst bed is controlled by heat exchange of cold hydrogen materials, and temperature runaway is avoided. Experiments show that the opening position of the hydrogen distribution pipe 8 on the reactor is 1/3-2/3 of the height of the reactor, which is more beneficial to the hydrogenation reaction.
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 process for producing the succinic acid by the aqueous-phase hydrogenation of the maleic anhydride, 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 by matching with the high-efficiency hydrogenation catalyst, and can meet the requirements of food grade, medical grade and polymerization grade on the purity of the succinic acid product. The invention adopts the fixed 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 graph of the catalyst stability experiment for example 2 and comparative example 2, in which the maleic anhydride conversion is for example 2; o is succinic acid selectivity of example 2; the tangle-solidup is the maleic anhydride conversion rate of the comparative example 2; 2 succinic acid selectivity in media
FIG. 2 is a process flow diagram showing 1. a stirred tank; 2. a raw material tank; 3. a premixer; 4. a hydrogenation reactor; 5. a gas-liquid separator; 6. recycling hydrogen; 7. (ii) fresh hydrogen; 8. a hydrogen distribution pipe; 9. a hydrogen distribution pipe; 10. crystallization tank
Detailed Description
The invention is further illustrated, but not limited, by the following examples.
The composition and physical and chemical properties of the catalyst used in the process of the present invention are shown in table 1.
Example 1:
example 1 a Pd/C catalyst was used, the composition and properties of which are shown in table 1. Maleic anhydride and water are mixed according to the mass ratio of 2:3Mixing evenly, reacting maleic anhydride with water in a stirring kettle to generate maleic acid and release a large amount of heat, and introducing cooling water into a stirring kettle jacket to control the temperature of the stirring kettle to 100 ℃. The raw materials after being uniformly mixed are pumped into a raw material tank 2, and the temperature of the raw materials is 80 ℃. The raw materials and hydrogen 9 are uniformly mixed in the pre-mixer 3 by a pump, and the obtained mixture enters from the top of the reactor 4 to fully contact and react with the catalyst in the reactor. Another stream of hydrogen 8 was fed at reactor height 1/3, with a 1:1 volume ratio of hydrogen 8 to hydrogen 9. The outlet temperature of the reactor is 100 ℃, the reaction pressure is 1.0MPa, and the mass space velocity is 1.5h-1The volume ratio of hydrogen to aqueous maleic acid was 200. And (3) allowing the material discharged from the reactor to enter a separation tank for gas-liquid separation, wherein the temperature of the separation tank is 100 ℃, discharging unreacted hydrogen from the top of the separation tank, and recycling the unreacted hydrogen by a recycle hydrogen compressor. And (3) obtaining a liquid product at the bottom, feeding the liquid product into a crystallization tank, cooling the material in the crystallization tank to-8 ℃, crystallizing the succinic acid to obtain a product, and recycling the residual liquid into the stirring kettle for reuse, wherein the content of organic matters in the circulating water is 0.08%. The results are shown in Table 2, where the conversion of maleic acid was 100% and the selectivity of succinic acid was 99.95%.
Comparative example 1
Comparative example 1 the same catalyst was used as in example 1, and the composition and properties of the catalyst are shown in table 1. The difference of the process is that the stirring kettle does not adopt heat transfer measures, so the temperature of the solution in the stirring kettle is raised to 200 ℃, side reactions are caused by violent heat release, and the contents of fumaric acid and malic acid in a raw material tank are respectively 1.5 percent and 1.1 percent. The reactor does not adopt a sectional feeding mode, the inlet temperature of the reactor is 150 ℃, the outlet temperature of the reactor reaches 240 ℃, the temperature of the gas-liquid separation tank is 200 ℃, the temperature of the crystallization tank is 30 ℃, and the content of the organic acid in the circulating water is 10.0 percent. The conversion rate of maleic acid is 100%, the selectivity of succinic acid is 80.89%, by-products are increased due to severe fluctuation of temperature, and the selectivity of succinic acid is reduced.
Example 2
The composition and properties of the catalyst of example 2 are shown in table 1. Maleic anhydride and water are uniformly mixed according to the mass ratio of 2:8, and the maleic anhydride and the water are subjected to chemical reaction in a stirring kettle to generate maleic anhydrideThe acid releases a large amount of heat, and cooling water is introduced into the jacket of the stirring kettle to control the temperature of the stirring kettle to 80 ℃. The raw materials after being uniformly mixed are pumped into a raw material tank 2, and the temperature of the raw materials is 50 ℃. The raw materials and hydrogen 9 are uniformly mixed in the pre-mixer 3 by a pump, and the obtained mixture enters from the top of the reactor 4 to fully contact and react with the catalyst in the reactor. Another stream of hydrogen 8 was fed at reactor height 2/3, with a 1:10 volume ratio of hydrogen 8 to hydrogen 9. The outlet temperature of the reactor is 65 ℃, the reaction pressure is 0.5MPa, and the mass space velocity is 0.2h-1The volume ratio of hydrogen to aqueous maleic acid was 1000. And (3) allowing the material discharged from the reactor to enter a separation tank for gas-liquid separation, wherein the temperature of the separation tank is 60 ℃, discharging unreacted hydrogen from the top of the separation tank, and recycling the unreacted hydrogen by a recycle hydrogen compressor. And (3) obtaining a liquid product at the bottom, feeding the liquid product into a crystallization tank, cooling the material to 0 ℃ in the crystallization tank, crystallizing the succinic acid to obtain a product, and recycling the residual liquid into the stirring kettle for reuse, wherein the content of organic matters in the circulating water is 0.32%. The results obtained are shown in table 2, with a maleic acid conversion of 99.99% and a succinic acid selectivity of 99.99%.
Comparative example 2
Comparative example 2 the same catalyst was used as in example 2, and the composition and properties of the catalyst are shown in table 1. The difference of the process is that the stirring kettle does not adopt heat transfer measures, so the temperature of the solution in the stirring kettle is raised to 120 ℃, side reactions are caused by violent heat release, and the contents of fumaric acid and malic acid in a raw material tank are respectively 0.08 percent and 0.02 percent. The reactor does not adopt a sectional feeding mode, the inlet temperature of the reactor is 90 ℃, the outlet temperature of the reactor reaches 150 ℃, the temperature of the gas-liquid separation tank is 140 ℃, the temperature of the crystallization tank is 30 ℃, and the content of the organic acid in the circulating water is 10.0 percent. The conversion rate of maleic acid is 99.93%, the selectivity of succinic acid is 92.27%, the by-products are increased due to temperature rise, and the selectivity of succinic acid is reduced.
Example 3
The composition and properties of the catalyst of example 3 are shown in table 1. Maleic anhydride and water are uniformly mixed according to the mass ratio of 2:15, the maleic anhydride and the water are subjected to chemical reaction in a stirring kettle to generate maleic acid, a large amount of heat is released, cooling water is introduced into a stirring kettle jacket to control the temperature of the stirring kettleTo 60 ℃. The raw materials after being uniformly mixed are pumped into a raw material tank 2, and the temperature of the raw materials is 55 ℃. The raw materials and hydrogen 9 are uniformly mixed in the pre-mixer 3 by a pump, and the obtained mixture enters from the top of the reactor 4 to fully contact and react with the catalyst in the reactor. Another stream of hydrogen 8 was fed at reactor height 1/2, with a 1:3 volume ratio of hydrogen 8 to hydrogen 9. The outlet temperature of the reactor is 70 ℃, the reaction pressure is 1.5MPa, and the mass space velocity is 5.0h-1The volume ratio of hydrogen to aqueous maleic acid was 1000. And (3) allowing the material discharged from the reactor to enter a separation tank for gas-liquid separation, wherein the temperature of the separation tank is 70 ℃, discharging unreacted hydrogen from the top of the separation tank, and recycling the unreacted hydrogen by a recycle hydrogen compressor. And (3) obtaining a liquid product at the bottom, feeding the liquid product into a crystallization tank, cooling the material to 10 ℃ in the crystallization tank, crystallizing the succinic acid to obtain a product, and recycling the residual liquid into the stirring kettle for reuse, wherein the content of organic matters in the circulating water is 1.81%. The results obtained are shown in table 2, with a maleic acid conversion of 99.98% and a succinic acid selectivity of 99.99%.
Comparative example 3
Comparative example 3 the same catalyst was used as in example 3, and the composition and properties of the catalyst are shown in table 1. The difference of the process is that the stirring kettle does not adopt heat transfer measures, so that the temperature of the solution in the stirring kettle is raised to 70 ℃, and fumaric acid and malic acid are not detected in the raw material tank. The reactor does not adopt a sectional feeding mode, the inlet temperature of the reactor is 65 ℃, the outlet temperature of the reactor reaches 110 ℃, the temperature of the gas-liquid separation tank is 100 ℃, the temperature of the crystallization tank is 30 ℃, and the content of the organic acid in the circulating water is 10.1 percent. The conversion rate of maleic acid is 99.98%, the selectivity of succinic acid is 98.65%, by-products are increased due to reaction temperature rise, and the selectivity of succinic acid is reduced.
Example 4
The composition and properties of the catalyst of example 4 are shown in table 1. Maleic anhydride and water are uniformly mixed according to the mass ratio of 2:1, the maleic anhydride and the water are subjected to chemical reaction in a stirring kettle to generate maleic acid, a large amount of heat is released, and cooling water is introduced into a stirring kettle jacket to control the temperature of the stirring kettle to 120 ℃. The raw materials are pumped into a raw material tank 2 after being uniformly mixed, and the temperature of the raw materials is 100 ℃. The raw material is mixed with hydrogen 9 in a pre-mixer 3 by a pumpThe mixture is uniform, and the mixture enters from the top of the reactor 4 to be fully contacted and reacted with the catalyst in the reactor. Another stream of hydrogen 8 was fed at reactor height 1/2, with a 1:5 volume ratio of hydrogen 8 to hydrogen 9. The inlet temperature of the reactor is 100 ℃, the outlet temperature of the reactor is 110 ℃, the reaction pressure is 4.5MPa, and the mass space velocity is 8.0h-1The volume ratio of hydrogen to aqueous maleic acid was 600. And (3) allowing the material discharged from the reactor to enter a separation tank for gas-liquid separation, wherein the temperature of the separation tank is 80 ℃, discharging unreacted hydrogen from the top of the separation tank, and recycling the unreacted hydrogen by a recycle hydrogen compressor. And (3) obtaining a liquid product at the bottom, feeding the liquid product into a crystallization tank, cooling the material to 20 ℃ in the crystallization tank, crystallizing the succinic acid to obtain a product, and recycling the residual liquid into the stirring kettle for reuse, wherein the content of organic matters in the circulating water is 5.1%. The results obtained are shown in table 2, with a maleic acid conversion of 99.89% and a succinic acid selectivity of 99.99%.
Comparative example 4
Comparative example 4 the same catalyst was used as in example 4, and the composition and properties of the catalyst are shown in table 1. The difference of the process is that the stirring kettle does not adopt heat transfer measures, so the temperature of the solution in the stirring kettle is raised to 210 ℃, the severe heat release causes side reaction in the hydrolysis process, and the contents of fumaric acid and malic acid in the raw material tank are respectively 2.0 percent and 1.3 percent. The reactor does not adopt a sectional feeding mode, the inlet temperature of the reactor is 200 ℃, the outlet temperature of the reactor reaches 250 ℃, the temperature of the gas-liquid separation tank is 220 ℃, the temperature of the crystallization tank is 30 ℃, and the content of the organic acid in the circulating water is 10.0 percent. The conversion rate of maleic acid is 99.95%, the selectivity of succinic acid is 90.24%, the by-products are increased due to the reaction temperature rise, and the selectivity of succinic acid is reduced.
Example 5
The composition and properties of the catalyst of example 5 are shown in table 1. Maleic anhydride and water are uniformly mixed according to the mass ratio of 2:10, the maleic anhydride and the water are subjected to chemical reaction in a stirring kettle to generate maleic acid, a large amount of heat is released, and cooling water is introduced into a stirring kettle jacket to control the temperature of the stirring kettle to 30 ℃. The raw materials after being uniformly mixed are pumped into a raw material tank 2, and the temperature of the raw materials is 30 ℃. The raw materials are uniformly mixed with hydrogen 9 in a pre-mixer 3 by a pump, and the mixture is reactedThe top of the reactor 4 enters into full contact reaction with the catalyst in the reactor. Another stream of hydrogen 8 was fed at reactor height 1/2, with a 1:8 volume ratio of hydrogen 8 to hydrogen 9. The inlet temperature of the reactor is 30 ℃, the outlet temperature of the reactor is 50 ℃, the reaction pressure is 5.0MPa, and the mass space velocity is 10.0h-1The volume ratio of hydrogen to aqueous maleic acid was 800. And (3) allowing the material discharged from the reactor to enter a separation tank for gas-liquid separation, wherein the temperature of the separation tank is 50 ℃, discharging unreacted hydrogen from the top of the separation tank, and recycling the unreacted hydrogen by a recycle hydrogen compressor. And (3) obtaining a liquid product at the bottom, feeding the liquid product into a crystallization tank, cooling the material to 30 ℃ in the crystallization tank, crystallizing the succinic acid to obtain a product, and recycling the residual liquid into the stirring kettle for reuse, wherein the content of organic matters in the circulating water is 10.0%. The results obtained are shown in table 2, with a maleic acid conversion of 99.95% and a succinic acid selectivity of 99.99%.
Comparative example 5
Comparative example 5 the same catalyst was used as in example 5, and the composition and properties of the catalyst are shown in table 1. The difference of the process is that the stirring kettle does not adopt heat transfer measures, so the temperature of the solution in the stirring kettle is raised to 100 ℃, and fumaric acid and malic acid are not detected in the raw material tank. The reactor does not adopt a sectional feeding mode, the inlet temperature of the reactor is 90 ℃, the outlet temperature of the reactor reaches 130 ℃, the temperature of the gas-liquid separation tank is 130 ℃, the temperature of the crystallization tank is 30 ℃, and the content of the organic acid in the circulating water is 10.0 percent. The conversion rate of maleic acid is 99.98%, the selectivity of succinic acid is 98.35%, the by-products are increased due to the reaction temperature rise, and the selectivity of succinic acid is reduced.
Stability test
2016h stability test was performed under the conditions of example 2 and comparative example 2, and the results are shown in FIG. 1. As can be seen from the figure, the long-term stable operation of the catalyst can be achieved under the conditions of the present invention while the comparative example 2 does not consider the heat effects of the raw material dissolution process and the reaction process, and does not control the temperatures of the gas-liquid separator and the crystallization tank, so that byproducts are generated during the reaction process and accumulated for a long time to affect the catalyst stability.
TABLE 1 catalyst composition, physico-chemical Properties
| Examples | Catalyst composition | Contact Angle/° | Acid amount/mmol NH3/g | Pore volume proportion/% of less than 1nm |
| Example 1 | 0.2％Pd/C | 20 | 0.02 | 10 |
| Example 2 | 1.5％Rh-1.2％Ag/α-Al2O3 | 40 | 0.5 | 22 |
| Example 3 | 2.3％Ru-6.8％Au/SiC | 25 | 1.1 | 29 |
| Example 4 | 0.5％Pt-0.5％Pd/ |
5 | 1.6 | 36 |
| Example 5 | 0.6％Rh-0.5％Au-0.3％Ru/SiC | 60 | 2.0 | 49 |
TABLE 2 reaction Process conditions and evaluation results
| Process conditions and evaluation results | Example 1 | Comparative example 1 | Example 2 | Comparative example 2 | Example 3 | Comparative example 3 | Example 4 | Comparative example 4 | Example 5 | Comparative example 5 |
| Maleic anhydride/water (quality) | 2：3 | 2：3 | 2:8 | 2:8 | 2:15 | 2:15 | 2:1 | 2:1 | 2:10 | 2:10 |
| Stirred tank temperature/. degree.C | 100 | 200 | 80 | 120 | 60 | 70 | 120 | 210 | 30 | 100 |
| Amount of fumaric acid/% in raw material tank | - | 1.5 | - | 0.08 | - | - | - | 2.0 | - | - |
| Malic acid/% in the stock tank | - | 1.1 | - | 0.02 | - | - | - | 1.3 | - | - |
| Volume ratio of hydrogen gas to hydrogen gas of 8 to 9 | 1：1 | - | 1：10 | - | 1：3 | - | 1：5 | - | 1：8 | - |
| Hydrogen 8 entry location | 1/3 position | - | 2/3 position | - | 1/2 position | - | 1/2 position | - | 1/2 position | - |
| Reactor inlet temperature/. degree.C | 80 | 150 | 50 | 90 | 55 | 65 | 100 | 200 | 30 | 90 |
| Reactor outlet temperature/. degree.C | 100 | 240 | 65 | 150 | 70 | 110 | 110 | 250 | 50 | 130 |
| Reaction pressure/MPa | 1.0 | 1.0 | 0.5 | 0.5 | 1.5 | 1.5 | 4.5 | 4.5 | 5.0 | 5.0 |
| Mass space velocity/h-1 | 1.5 | 1.5 | 0.2 | 0.2 | 5.0 | 5.0 | 8.0 | 8.0 | 10.0 | 10.0 |
| Hydrogen/maleic acid aqueous solution volume ratio | 200 | 200 | 1000 | 1000 | 1000 | 1000 | 600 | 600 | 800 | 800 |
| Temperature/. degree.C.of gas-liquid separation tank | 100 | 200 | 60 | 140 | 70 | 90 | 80 | 220 | 50 | 130 |
| Crystallization tank temperature/. degree.C | -8 | 30 | 0 | 30 | 10 | 30 | 20 | 30 | 30 | 30 |
| Content of organic matter in the circulating water/%) | 0.08 | 10.0 | 0.32 | 10.0 | 1.81 | 10.1 | 5.1 | 10.0 | 10.0 | 10.0 |
| Conversion of maleic acid/%) | 100 | 100 | 99.99 | 99.93 | 99.98 | 99.98 | 99.89 | 99.95 | 99.95 | 99.98 |
| Succinic acid selectivity/%) | 99.95 | 80.89 | 99.99 | 92.27 | 99.99 | 98.65 | 99.99 | 90.24 | 99.99 | 98.35 |
Claims (6)
1. A process for preparing succinic acid by maleic anhydride aqueous phase hydrogenation comprises a stirring kettle, a raw material tank, a raw material and hydrogen premixer, a hydrogenation reactor, a hydrogen distribution pipe, a gas-liquid separation tank and a crystallization tank unit, and comprises the following specific process steps:
1) uniformly mixing the raw materials and water in a stirring kettle (1) according to a certain proportion, and controlling the temperature of the stirring kettle at 50-120 ℃;
2) the water solution obtained in the step 1) enters a raw material tank (2), and the temperature of the raw material tank is controlled to be 30-100 ℃;
3) the raw material in the raw material tank (2) and the first hydrogen (9) are uniformly mixed in the premixer (3);
4) the mixture obtained in the step 3) enters from the top of the reactor (4);
5) the material entering the reactor (4) is fully contacted and reacted with the catalyst in the reactor (4);
6) the material from the reactor (4) enters a gas-liquid separation tank (5) for gas-liquid separation, a liquid product is obtained at the bottom and enters a crystallization tank (10), the material is cooled to-10-30 ℃ in the crystallization tank (10), succinic acid is crystallized to obtain a product, and the residual liquid is recycled to the stirring kettle (1) for reuse;
7) unreacted hydrogen (6) is circulated by a circulating hydrogen compressor and mixed with new hydrogen (7) and then is divided into two parts by a hydrogen distribution pipe in proportion, first hydrogen (9) enters a premixer (3), and second hydrogen (8) enters the reactor from the positions 1/3-2/3;
wherein, the catalyst in the step 5) has the following technical characteristics: the catalyst consists of an active component and an acid-resistant in-vivo carrier, wherein the active component consists of at least one of Ru, Rh, Pd, Pt, Au and Ag, the mass percentage of the active component is 0.1-10%, and the acid-resistant carrier is one of active carbon, alpha alumina, silicon oxide or silicon carbide; 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%.
2. The process of claim 1, wherein the weight ratio of the feedstock to water in step 1) is 2:1 to 18.
3. The process of claim 1, wherein the volume ratio of the hydrogen gas and the raw material in the step 3) is 100-1000.
4. The process of claim 1, wherein the hydrogenation reactor in the step 5) is a fixed bed reactor, the inlet temperature of the reactor is 30-100 ℃, the outlet temperature of the reactor is 50-200 ℃, the reaction pressure is 0.5-5.0 MPa, and the mass space velocity is 0.1-10 h-1The volume ratio of hydrogen to oil is 110-2000.
5. The process according to claim 1, wherein the temperature of the separation tank in the step 6) is controlled to be 50-150 ℃.
6. The process according to claim 1, wherein the volume ratio of the second hydrogen (8) to the first hydrogen (9) in the step 7) is 1: 1-10.
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