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CN-122010721-A - Hydrotreatment method of crude terephthalic acid

CN122010721ACN 122010721 ACN122010721 ACN 122010721ACN-122010721-A

Abstract

The present application relates to a process for the hydroprocessing of crude terephthalic acid comprising reacting crude terephthalic acid with hydrogen in the presence of a hydrogenation catalyst, a solvent and a fatty acid selected from one or more of the C1-C6 carboxylic acids. The application solves the problem of serious decarboxylation in the process of producing refined phthalic acid by purifying crude terephthalic acid to a great extent by introducing C1-C6 carboxylic acid in the crude terephthalic acid hydrotreatment. The method provided by the application is used for the purification reaction of crude terephthalic acid, and has the characteristic of low impurity benzoic acid after hydrogenation purification.

Inventors

  • XIAO ZHONGBIN
  • GAO XIAOCHEN
  • HE LIMIN
  • LUO WEI

Assignees

  • 中国石油化工股份有限公司
  • 中石化（上海）石油化工研究院有限公司

Dates

Publication Date
20260512
Application Date
20241111

Claims (10)

  1. 1. A process for the hydroprocessing of crude terephthalic acid comprising reacting crude terephthalic acid with hydrogen in the presence of a hydrogenation catalyst, a solvent, and a fatty acid selected from one or more of C1-C6 carboxylic acids.
  2. 2. The hydrotreating process according to claim 1, characterized in that said fatty acid is selected from one or more of C1-C4 monocarboxylic acids, preferably from one or more of formic acid, acetic acid, n-propionic acid and n-butyric acid.
  3. 3. The hydrotreating process according to claim 1 or 2, wherein the mass ratio of fatty acid to solvent is (0.001-0.05): 1, preferably (0.005-0.02): 1, more preferably (0.009-0.013): 1, and/or The solvent is selected from water.
  4. 4. A hydrotreating process as claimed in any one of claims 1 to 3, in which the temperature of the reaction is 250℃to 300℃and preferably 270℃to 290℃and/or The pressure of the reaction is 5MPaG-10MPaG, preferably 6.5MPaG-8.5MPaG, and/or The reaction time is 10min-150min, preferably 30min-100min.
  5. 5. The hydrotreating process according to claim 4, wherein the partial pressure of hydrogen is 3MPaG to 10MPaG, preferably 4MPaG to 7MPaG.
  6. 6. The hydrotreating process according to any one of claims 1 to 5, in which the ratio of crude terephthalic acid to solvent mass is 1 (3 to 50), preferably 1 (5 to 30).
  7. 7. The hydrotreating process according to any one of claims 1 to 6, wherein the ratio of hydrogenation catalyst to solvent mass is (0.05 to 5): 100, preferably (0.1 to 3): 100.
  8. 8. A hydrotreating process as claimed in any one of claims 1 to 7, in which the mesh number of the hydrogenation catalyst is 3 to 10 mesh, preferably 4 to 8 mesh, and/or The hydrogenation catalyst is selected from palladium-carbon catalysts, and the palladium-carbon catalysts comprise active components of palladium and carrier active carbon.
  9. 9. A hydrotreating process as claimed in claim 8, characterized in that the active component palladium is present in an amount of from 0.2% to 0.6% by mass, preferably from 0.45% to 0.55% by mass, and/or The specific surface area of the activated carbon is 900m 2 /g-1200m 2 /g, the pore volume is 0.45m 3 /g-0.70m 3 /g, and/or The activated carbon is selected from one or more of coal carbon, wood carbon and shell carbon, preferably coconut shell carbon.
  10. 10. The hydrotreating process according to any one of claims 1 to 9, wherein the mass content of p-carboxybenzaldehyde in said crude terephthalic acid is less than or equal to 4000ppmw, and the mass content of p-methylbenzoic acid is less than or equal to 1000ppmw.

Description

Hydrotreatment method of crude terephthalic acid Technical Field The application relates to a hydrotreating method of crude terephthalic acid. Background Refined terephthalic acid is one of the basic raw materials for synthesizing polyethylene terephthalate (PET), commonly called PTA, the demand continues to increase, and in 2024, the global PTA demand is expected to reach 9000 ten thousand tons. The current PTA production technology is mainly a two-step process of oxidizing and hydrofining Paraxylene (PX) developed by Mid-Centry (Amoco-BP acquisition). In the production process, acetic acid is used as a solvent and a Co-Mn-Br catalyst system is adopted in the oxidation step, p-aldehyde benzoic acid (4-CBA) is added into p-methylbenzoic acid (p-TA) mainly through hydrogenation under a palladium-carbon catalyst at high temperature and high pressure, and then the p-methylbenzoic acid (p-TA) is removed through centrifugation and water elution. The PTA quality is affected by a plurality of indexes, the content of 4-CBA is required to be less than 25ppmw for the PTA of the polyester grade, and the content of p-methylbenzoic acid (p-TA) is required to be less than 150ppmw. The hydrogenation processes differ mainly in the oxidation reaction temperature (from 160 ℃ to 225 ℃) and the corresponding process conditions, reactor form and flow design. ICI and Amoco react at the highest temperatures, the triple well-Amoco temperature is centered, and Eastman is the lowest, respectively known as the high temperature oxidation, medium temperature oxidation, and low temperature oxidation processes. But the process variation in the hydrogenation process is not great, the temperature is 250-290 ℃, and the pressure is 6.5-9.0 MPa. Due to the severe hydrogenation conditions, the decarboxylation of the carboxyl groups on the benzene rings to Benzoic Acid (BA) is unavoidable, which leads to the loss of Terephthalic Acid (TA) as a product, and the hydrogenation of 4-CBA to p-hydroxymethylbenzoic acid (HMBA) and p-TA can be returned to the oxidation system by centrifugal separation. In order to reduce the decarboxylation reaction in the hydrogenation process, the reaction temperature and the reaction pressure are reduced as much as possible or the partial pressure of hydrogen is reduced, but the colored impurities of the 4-CBA are improved, and the quality of the PTA product is reduced. U.S. patent No. 4626598 (Purification of TEREPHTHALIC ACID) discloses a method for increasing the hydrogen partial pressure in the hydrogenation process or increasing the hydrogenation reaction temperature to reduce the PTA b value, which increases the energy and material consumption of the reaction, but also increases the decarboxylation side reaction of terephthalic acid. Disclosure of Invention The application aims to solve the technical problem of serious decarboxylation in the process of producing refined phthalic acid by purifying crude terephthalic acid, and provides a novel method for hydrotreating crude terephthalic acid, which is used for purifying crude terephthalic acid and has the characteristic of low impurity benzoic acid after hydrogenation purification. Specifically, the method for hydrotreating crude terephthalic acid provided by the application comprises the step of reacting crude terephthalic acid with hydrogen in the presence of a hydrogenation catalyst, a solvent and fatty acid, wherein the fatty acid is selected from one or more of C1-C6 carboxylic acids. According to the application, the C1-C6 carboxylic acid is introduced in the hydrotreatment of the crude terephthalic acid, so that on one hand, the decarboxylation of the terephthalic acid can be reduced by taking the C1-C6 carboxylic acid and the solvent as mixed solvents, and on the other hand, the content of 4-CBA impurity in the hydrogenated product can be effectively reduced by adding the C1-C6 carboxylic acid. In some embodiments, the fatty acid is selected from one or more of C1-C4 monocarboxylic acids. In some embodiments, the fatty acid is selected from one or more of formic acid, acetic acid, n-propionic acid, and n-butyric acid. In some embodiments, the mass ratio of fatty acid to solvent is (0.001-0.05): 1, e.g., 0.003:1、0.005:1、0.007:1、0.009:1、0.01:1、0.011:1、0.013:1、0.015:1、0.017:1、0.019:1、0.02:1、0.021:1、0.023:1、0.025:1、0.027:1、0.029:1、0.03:1、0.031:1、0.033:1、0.035:1、0.037:1、0.039:1、0.04:1、0.041:1、0.043:1、0.045:1、0.047:1、0.049:1 or any value therebetween. The too high mass ratio of fatty acid to solvent, i.e. when the fatty acid content is too high, can inhibit the hydrogenation reaction, and the too low mass ratio of fatty acid to solvent, i.e. when the fatty acid content is too low, the reduction effect on the impurity 4-CBA is not obvious. In some embodiments, the mass ratio of fatty acid to solvent is (0.005-0.02): 1. In some embodiments, the mass ratio of fatty acid to solvent is (0.009-0.013): 1. In some embodiments, the solvent is selected from water. In so