Composition for preparing palladium-carbon catalyst and application thereof

Abstract

The invention provides a composition for preparing a palladium-carbon catalyst and application of the composition. The composition comprises a modified carbon material with an oxygen-containing functional group, a covering agent and a palladium precursor aqueous solution, the covering agent comprises a compound with a structure as shown in a formula I and / or a formula II. According to the catalyst disclosed by the invention, the catalytic efficiency of a palladium-carbon catalyst can be remarkably improved, and the residual quantity of 4-CBA can be effectively reduced in a terephthalic acid hydrofining reaction.

Description

Technical Field

[0001] This invention relates to the field of catalyst technology, and more specifically to a composition for preparing palladium-on-carbon catalysts and its applications. Background Technology

[0002] Purified terephthalic acid (PTA) is a major raw material for polyester production, and its demand has been increasing in recent years. Improving PTA product quality and reducing raw material consumption are crucial for industrial production. PTA production mainly employs the air oxidation process with p-xylene. Although the product undergoes separation and purification after the oxidation reaction, a significant amount of impurity 4-CBA remains. To reduce this impurity content, further purification is required by reacting 4-CBA with hydrogen in the presence of a catalyst. Palladium-on-carbon catalyst is currently the most widely used catalyst for the hydrogenation purification of crude terephthalic acid.

[0003] US Patent 6066589A discloses a hydrogenation catalyst in which palladium is supported on activated carbon, wherein less than 50% of the Pd is supported in a surface layer of less than 50 μm on the support surface, and the remaining palladium is located in a surface layer of 50-400 μm. Patent CN104549241A discloses a terephthalic acid hydrogenation refining catalyst, using activated carbon as a support, with a palladium mass percentage of 0.20-1.0%, wherein 70-85% of the palladium is distributed in a surface layer of 0.2-20 μm, no more than 10% of the palladium is distributed in a surface layer of 0-0.20 μm on the support, and the remaining palladium is distributed in an inner layer of 20-180 μm.

[0004] However, existing catalysts suffer from severe palladium loss and low hydrogenation efficiency. Therefore, developing highly efficient catalysts is currently a research hotspot. Summary of the Invention

[0005] The purpose of this invention is to overcome the shortcomings of the prior art and provide a composition for preparing palladium-on-carbon catalysts and its applications.

[0006] In a first aspect, the present invention provides a composition for preparing a palladium-on-carbon catalyst, comprising: a modified carbon material having oxygen-containing functional groups, a covering agent, and an aqueous solution of a palladium precursor; wherein the compound having the structure shown in Formula I and / or Formula II:

[0007]

[0008] Wherein, R1, R2, R3, R4, and R5 are each independently selected from hydrogen, deuterium, halogen, substituted or unsubstituted C1-C10 alkyl, substituted or unsubstituted C1-C10 alkoxy, substituted or unsubstituted C1-C10 heteroalkyl, -NH2, -OH, substituted or unsubstituted amino, acyl, carbonyl, hydroxyl, or ester group having 1-10 carbon atoms; the substituents are selected from deuterium, halogen, C1-C10 straight-chain or branched alkyl, C3-C10 cycloalkyl, C6-C20 aryl, -NH2, C1-C10 alkyl-substituted amino or C3-C20 heteroaryl, and the number of substituents is selected from an integer between 1 and 10;

[0009] n is 1 or 2.

[0010] In some embodiments, the covering agent has at least one of the following physical parameters: (1) a surface tension of 20-60 dyne / cm; for example, 20 dyne / cm, 25 dyne / cm, 30 dyne / cm, 35 dyne / cm, 40 dyne / cm, 45 dyne / cm, 50 dyne / cm, 55 dyne / cm, 60 dyne / cm or any value between them; (2) a polarizability of the covering agent > 7 (10 -24 cm 3 ).

[0011] In some embodiments, the covering agent has at least one of the following physical parameters: (1) surface tension 25-35 dyne / cm; (2) polarizability 9.5-12 (10 -24 cm 3 For example, 9.5 (10) -24 cm 3 ), 9.8 (10 -24 cm 3 ),10.1(10 -24 cm 3 ), 10.4(10 -24 cm 3 ), 10.7 (10 -24 cm 3 ),11(10 -24 cm 3 ), 11.3 (10 -24 cm 3 ), 11.7 (10 -24 cm 3 ), 12(10 -24 cm 3 ) or any value between them.

[0012] In some embodiments, R1, R2, R3, R4, and R5 are each independently selected from hydrogen, deuterium, halogen, substituted or unsubstituted C1-C10 alkyl, -NH2, -OH, substituted or unsubstituted amino groups having 1-10 carbon atoms, and hydroxyl groups; the substituents are selected from deuterium, halogen, C1-C10 straight-chain or branched alkyl, -NH2, or C1-C10 alkyl-substituted amino groups, and the number of substituents is selected from an integer between 1 and 5.

[0013] In some embodiments, R1, R2, R3, R4, and R5 are each independently selected from hydrogen, deuterium, F, Cl, Br, methyl, ethyl, propyl, butyl, or -NH2.

[0014] In some embodiments, R1, R2, R3, R4, and R5 are each independently selected from hydrogen, deuterium, methyl, ethyl, propyl, or butyl.

[0015] In some embodiments, the covering agent includes one or more of γ-methylpyridine, 2-methyltetrahydrofuran, or tetrahydrofuran.

[0016] In some embodiments, the covering agent comprises γ-methylpyridine and / or 2-methyltetrahydrofuran.

[0017] In some embodiments, the aqueous palladium precursor is selected from one or more of aqueous chloropalladium acid, aqueous tetraaminopalladium nitrate, or aqueous palladium acetate.

[0018] In some embodiments, the pH of the aqueous palladium precursor solution is 0.1-5, for example 0.1, 1, 2, 3, 4, 5.

[0019] In some embodiments, the pH of the aqueous palladium precursor solution is adjusted using hydrochloric acid and / or nitric acid.

[0020] In some embodiments, the method for preparing the modified carbon material having oxygen-containing functional groups includes: mixing carbon material, polyol and pH adjuster and reacting them.

[0021] In some embodiments, the carbon material is selected from one or more of carbon nanotubes, carbon nanofibers, or activated carbon.

[0022] In some embodiments, the carbon material is carbon nanotubes. The surface of carbon nanotubes is easy to modify and functionalize, and their electron transport properties are beneficial for subsequent catalytic reactions.

[0023] In some embodiments, the aspect ratio of the carbon nanotubes is 125-12500, for example, 150, 550, 1070, 2500, 4200, 6100, 8000, 9500, 10500, 12000 or any value between them.

[0024] In some embodiments, the outer diameter of the carbon nanotubes is 8-80 nm, for example, 10 nm, 20 nm, 30 nm, 40 nm, 50 nm, 60 nm, 70 nm, 80 nm or any value between them.

[0025] In some embodiments, the polyol is selected from one or more of ethylene glycol, propylene glycol, or glycerol.

[0026] In some embodiments, the pH adjuster is urea.

[0027] In some embodiments, the mass ratio of the polyol to the carbon material is 5-20; for example, 5:1, 7:1, 9:1, 11:1, 13:1, 15:1, 17:1, or 19:1. Within this range, abundant functionalized oxygen-containing functional groups can be formed on the surface of the carbon material.

[0028] In some embodiments, the mass ratio of the polyol to the pH adjuster is 200-50, for example, 200:1, 180:1, 160:1, 140:1, 120:1, 100:1, 80:1, or 60:1.

[0029] In some embodiments, the reaction temperature is 100-150°C, for example 100°C, 110°C, 120°C, 130°C, 140°C, or 150°C.

[0030] In some embodiments, the reaction pressure is 0.5-1.5 MPa, for example 0.5 MPa, 0.7 MPa, 0.9 MPa, 1.1 MPa, 1.3 MPa, or 1.5 MPa.

[0031] In some embodiments, the reaction is carried out in a hydrothermal reactor.

[0032] In some embodiments, the reaction time is 1-8 hours, for example 1 hour, 2 hours, 3 hours, 4 hours, 5 hours, 6 hours, 7 hours, or 8 hours.

[0033] In some embodiments, the reaction is carried out in an air atmosphere.

[0034] In a second aspect, the present invention provides a method for preparing a palladium-on-carbon catalyst, wherein the composition described in the first aspect of the present invention is subjected to a reduction treatment to obtain the palladium-on-carbon catalyst.

[0035] In some embodiments, the preparation method includes the following steps:

[0036] (1) A modified carbon material with oxygen-containing functional groups is treated with a first covering agent to obtain material A; (2) Material A is treated with an aqueous solution of palladium precursor to obtain material B; (3) Material B is subjected to reduction treatment; or

[0037] The preparation method includes the following steps: (1) treating a modified carbon material with oxygen-containing functional groups with a first covering agent to obtain material A; (2) treating material A with an aqueous solution of a palladium precursor to obtain material B; (3) treating material B with a second covering agent to obtain material C; (4) reducing material C; the first covering agent and / or the second covering agent include compounds having the structures shown in Formula I and / or Formula II: II;

[0038] Wherein, R1, R2, R3, R4, and R5 are each independently selected from hydrogen, deuterium, halogen, substituted or unsubstituted C1-C10 alkyl, substituted or unsubstituted C1-C10 alkoxy, substituted or unsubstituted C1-C10 heteroalkyl, -NH2, -OH, substituted or unsubstituted amino, acyl, carbonyl, hydroxyl, or ester groups having 1-10 carbon atoms; the substituents are selected from deuterium, halogen, C1-C10 straight-chain or branched alkyl, C3-C10 cycloalkyl, C6-C20 aryl, -NH2, C1-C10 alkyl-substituted amino, or C3-C20 heteroaryl, and the number of substituents is selected from an integer between 1 and 10; n is 1 or 2;

[0039] The second covering agent has at least one of the following physical parameter conditions:

[0040] (1) The surface tension is 20-60 dyne / cm (e.g., 20 dyne / cm, 25 dyne / cm, 30 dyne / cm, 35 dyne / cm, 40 dyne / cm, 45 dyne / cm, 50 dyne / cm, 55 dyne / cm, 60 dyne / cm or any value between them);

[0041] (2) Polarizability > 7 (10 -24 cm 3 ).

[0042] In some embodiments, the second covering agent has at least one of the following physical parameters: (1) surface tension 25-35 dyne / cm; (2) polarizability 9.5-12 (10 -24 cm 3 For example, 9.5 (10) -24 cm 3 ), 9.8 (10 -24 cm 3),10.1(10 -24 cm 3 ), 10.4(10 -24 cm 3 ), 10.7 (10 -24 cm 3 ),11(10 -24 cm 3 ), 11.3 (10 -24 cm 3 ), 11.7 (10 - 24 cm 3 ), 12(10 -24 cm 3 ) or any value between them.

[0043] In some embodiments, the first covering agent has at least one of the following physical parameter conditions:

[0044] (1) The surface tension is 20-60 dyne / cm (e.g., 20 dyne / cm, 25 dyne / cm, 30 dyne / cm, 35 dyne / cm, 40 dyne / cm, 45 dyne / cm, 50 dyne / cm, 55 dyne / cm, 60 dyne / cm or any value between them);

[0045] (2) Polarizability > 7 (10 -24 cm 3 ).

[0046] In some embodiments, the second covering agent has at least one of the following physical parameters: (1) surface tension 25-35 dyne / cm; (2) polarizability 9.5-12 (10 -24 cm 3 For example, 9.5 (10) -24 cm 3 ), 9.8 (10 -24 cm 3 ),10.1(10 -24 cm 3 ), 10.4(10 -24 cm 3 ), 10.7 (10 -24 cm 3 ),11(10 -24 cm 3 ), 11.3 (10 -24 cm 3 ), 11.7 (10 - 24 cm 3 ), 12(10-24 cm 3 ) or any value between them.

[0047] In some embodiments, the reducing agent used in the reduction treatment is one or more of sodium formate solution, formic acid, or hydrazine hydrate.

[0048] In some embodiments, the amount of the reducing agent is 1-10% of the mass of the carrier, for example, 1%, 2%, 3%, 4%, 5%, 6%, 7%, 8%, 9%, or 10%.

[0049] In some embodiments, the reduction treatment temperature is 50-120°C, for example 55°C, 60°C, 65°C, 70°C, 75°C, 80°C, 85°C, 90°C, 95°C, 100°C, 105°C, 110°C, or 115°C.

[0050] In some implementations, the reduction process takes 0.5-3 hours, for example, 1 hour, 1.5 hours, 2 hours, or 2.5 hours.

[0051] In some embodiments, R1, R2, R3, R4, and R5 are each independently selected from hydrogen, deuterium, halogen, substituted or unsubstituted C1-C10 alkyl groups, -NH2, -OH, substituted or unsubstituted amino groups having 1-10 carbon atoms, and hydroxyl groups.

[0052] The substituents are selected from deuterium, halogens, C1-C10 straight-chain or branched alkyl groups, -NH2, and C1-C10 alkyl-substituted amino groups, and the number of substituents is selected from an integer between 1 and 5.

[0053] In some embodiments, R1, R2, R3, R4, and R5 are each independently selected from hydrogen, deuterium, F, Cl, Br, methyl, ethyl, propyl, butyl, or -NH2.

[0054] In some embodiments, R1, R2, R3, R4, and R5 are each independently selected from hydrogen, deuterium, methyl, ethyl, propyl, or butyl.

[0055] In some embodiments, the first covering agent and / or the second covering agent comprises one or more of γ-methylpyridine, 2-methyltetrahydrofuran, or tetrahydrofuran.

[0056] In some embodiments, the first covering agent and / or the second covering agent comprises γ-methylpyridine and / or 2-methyltetrahydrofuran.

[0057] In some implementations, the first covering agent and the second covering agent are the same.

[0058] In a third aspect, the present invention provides the application of a palladium-on-carbon catalyst obtained by the preparation method described in the second aspect in a hydrogenation reaction.

[0059] In a fourth aspect, the present invention provides a method for hydrogenating and purifying terephthalic acid, comprising: using crude terephthalic acid containing 4-CBA and hydrogen as raw materials, and reacting in the presence of a palladium-on-carbon catalyst prepared by the preparation method described in the second aspect of the present invention.

[0060] In some embodiments, the pressure of the hydrogen gas is 0.1-1 MPa; for example, 0.1 MPa, 0.3 MPa, 0.5 MPa, 0.7 MPa, or 0.9 MPa.

[0061] In some embodiments, the reaction temperature is 100-150°C, for example 100°C, 110°C, 120°C, 130°C, 140°C, or 150°C.

[0062] In some embodiments, the reaction time is 20-40 minutes.

[0063] This invention, through the synergistic effect of the first and second covering agents, can significantly improve the dispersibility of the catalyst, thereby improving the catalytic efficiency of the catalyst. In the hydrogenation refining reaction of terephthalic acid, it can effectively reduce the residual amount of 4-CBA. Detailed Implementation

[0064] To make the objectives, technical solutions, and advantages of this invention clearer, the invention will be further described in detail below with reference to embodiments. The specific embodiments described herein are for illustrative purposes only and are not intended to limit the scope of the invention in any way.

[0065] Unless otherwise specified, all reagents used in this invention can be purchased commercially or prepared by the methods described herein. The carbon nanotubes used in the embodiments and comparative examples of this invention were purchased from the Chengdu Institute of Organic Chemistry, Chinese Academy of Sciences, with aspect ratios of 125-12500 and outer diameters of 8-80 nm.

[0066] The testing method of this invention is as follows:

[0067] The Pd content was determined by inductively coupled plasma atomic emission spectrometry (ICP-AES) using an Agilent 725-ES ICP-AES instrument. The catalyst described in this invention was dissolved in aqua regia and hydrofluoric acid. After evaporating the acid solution and diluting it, multiple measurements were performed, and the average value was taken to obtain the average Pd content (mass percentage).

[0068] Example 1

[0069] (a) Weigh 50g of carbon nanotubes and mix them with 500g of ethylene glycol. Stir and sonicate to form an ink-like mixture. Then add 4.5g of urea, purge with air to maintain a pressure of 1.2MPa, and react at 120℃ for 6h. Filter, wash with ethanol 5 times, collect the solid, and dry the solid in an oven at 100℃ for 6h. Record this solid as A.

[0070] (b) Prepare an aqueous solution of chloropalladium acid with a Pd mass concentration of 0.002 g / mL and adjust the pH to 1 with hydrochloric acid; add 5 g of 2-methyltetrahydrofuran dropwise to A and stir continuously for 10 min, then add 1.5 mL of chloropalladium acid dropwise to A and stir for 30 min; finally add 4.5 g of 2-methyltetrahydrofuran and continue stirring for 1 h to form a sludge-like substance. Dry the sludge in an oven at 120 °C for 6 h and record this as B.

[0071] (c) The dried solid was placed in 500 mL of sodium formate solution (5 wt.%) and heated to 80 °C for 1.5 h to reduce it.

[0072] The preparation conditions are listed in Table 1.

[0073] Example 2

[0074] (a) Weigh 50g of carbon nanotubes and mix them with 500g of ethylene glycol. Stir and sonicate to form an ink-like mixture. Then add 4.5g of urea, purge with air to maintain a pressure of 1.2MPa, and react at 120℃ for 6h. Filter, wash with ethanol 5 times, collect the solid, and dry the solid in an oven at 100℃ for 6h. Record this solid as A.

[0075] (b) Prepare an aqueous solution of chloropalladium acid with a Pd mass concentration of 0.002 g / mL and adjust the pH to 1 with hydrochloric acid; add 5 g of cyclohexanone dropwise into A and stir continuously for 10 min, then add 1.5 mL of chloropalladium acid dropwise into A and stir for 30 min; finally add 4.5 g of cyclohexanone and continue stirring for 1 h to form a sludge-like substance. Dry the sludge in an oven at 120 °C for 6 h and record this as B.

[0076] (c) The dried solid was placed in 500 mL of sodium formate solution (5 wt.%) and heated to 80 °C for 1.5 h to reduce it.

[0077] The preparation conditions are listed in Table 1.

[0078] Example 3

[0079] (a) Weigh 50g of carbon nanotubes and mix them with 500g of ethylene glycol. Stir and sonicate to form an ink-like mixture. Then add 4.5g of urea, purge with air to maintain a pressure of 1.2MPa, and react at 120℃ for 6h. Filter, wash with ethanol 5 times, collect the solid, and dry the solid in an oven at 100℃ for 6h. Record this solid as A.

[0080] (b) Prepare an aqueous solution of chloropalladium acid with a Pd mass concentration of 0.002 g / mL and adjust the pH to 1 with hydrochloric acid; add 5 g of tetrahydrofuran dropwise to A and stir continuously for 10 min, then add 1.5 mL of chloropalladium acid dropwise to A and stir for 30 min; finally add 4.5 g of tetrahydrofuran and continue stirring for 1 h to form a sludge-like substance. Dry the sludge in an oven at 120 °C for 6 h and record it as B.

[0081] (c) The dried solid was placed in 500 mL of sodium formate solution (5 wt.%) and heated to 80 °C for 1.5 h to reduce it.

[0082] The preparation conditions are listed in Table 1.

[0083] Example 4

[0084] (a) Weigh 50g of carbon nanotubes and mix them with 500g of ethylene glycol. Stir and sonicate to form an ink-like mixture. Then add 4.5g of urea, purge with air to maintain a pressure of 1.2MPa, and react at 120℃ for 6h. Filter, wash with ethanol 5 times, collect the solid, and dry the solid in an oven at 100℃ for 6h. Record this solid as A.

[0085] (b) Prepare an aqueous solution of chloropalladium acid with a Pd mass concentration of 0.002 g / mL and adjust the pH to 1 with hydrochloric acid; add 5 g of 2-methyltetrahydrofuran dropwise to A and stir continuously for 10 min, then add 1.5 mL of chloropalladium acid dropwise to A and stir for 30 min; finally add 4.5 g of cyclohexanone and continue stirring for 1 h to form a sludge-like substance. Dry the sludge in an oven at 120 °C for 6 h and record this as B.

[0086] (c) The dried solid was placed in 500 mL of sodium formate solution (5 wt.%) and heated to 80 °C for 1.5 h to reduce it.

[0087] The preparation conditions are listed in Table 1.

[0088] Example 5

[0089] (a) Weigh 50g of carbon nanotubes and mix them with 500g of ethylene glycol. Stir and sonicate to form an ink-like mixture. Then add 4.5g of urea, purge with air to maintain a pressure of 1.2MPa, and react at 120℃ for 6h. Filter, wash with ethanol 5 times, collect the solid, and dry the solid in an oven at 100℃ for 6h. Record this solid as A.

[0090] (b) Prepare an aqueous solution of chloropalladium acid with a Pd mass concentration of 0.002 g / mL and adjust the pH to 1 with hydrochloric acid; add 5 g of cyclohexanone dropwise to A and stir continuously for 10 min, then add 1.5 mL of chloropalladium acid dropwise to A and stir for 30 min; finally add 4.5 g of 2-methyltetrahydrofuran and continue stirring for 1 h to form a sludge-like substance. Dry the sludge in an oven at 120 °C for 6 h and record it as B.

[0091] (c) The dried solid was placed in 500 mL of sodium formate solution (5 wt.%) and heated to 80 °C for 1.5 h to reduce it.

[0092] The preparation conditions are listed in Table 1.

[0093] Example 6

[0094] (a) Weigh 50g of carbon nanotubes and mix them with 500g of ethylene glycol. Stir and sonicate to form an ink-like mixture. Then add 4.5g of urea, purge with air to maintain a pressure of 1.2MPa, and react at 120℃ for 6h. Filter, wash with ethanol 5 times, collect the solid, and dry the solid in an oven at 100℃ for 6h. Record this solid as A.

[0095] (b) Prepare an aqueous solution of chloropalladium acid with a Pd mass concentration of 0.002 g / mL and adjust the pH to 1 with hydrochloric acid; add 5 g of 2-methyltetrahydrofuran dropwise to A and stir continuously for 10 min, then add 1.5 mL of chloropalladium acid dropwise to A and stir for 30 min; finally add 4.5 g of tetrahydrofuran and continue stirring for 1 h to form a sludge-like substance. Dry the sludge in an oven at 120 °C for 6 h and record this as B.

[0096] (c) The dried solid was placed in 500 mL of sodium formate solution (5 wt.%) and heated to 80 °C for 1.5 h to reduce it.

[0097] The preparation conditions are listed in Table 1.

[0098] Example 7

[0099] (a) Weigh 50g of carbon nanotubes and mix them with 500g of ethylene glycol. Stir and sonicate to form an ink-like mixture. Then add 4.5g of urea, purge with air to maintain a pressure of 1.2MPa, and react at 120℃ for 6h. Filter, wash with ethanol 5 times, collect the solid, and dry the solid in an oven at 100℃ for 6h. Record this solid as A.

[0100] (b) Prepare an aqueous solution of chloropalladium acid with a Pd mass concentration of 0.002 g / mL and adjust the pH to 1 with hydrochloric acid; add 5 g of 2-methyltetrahydrofuran dropwise to A and stir continuously for 10 min, then add 1.5 mL of chloropalladium acid dropwise to A and stir for 30 min; finally add 4.5 g of N-methylpyrrolidone and continue stirring for 1 h to form a sludge-like substance. Dry the sludge in an oven at 120 °C for 6 h and record this as B.

[0101] (c) The dried solid was placed in 500 mL of sodium formate solution (5 wt.%) and heated to 80 °C for 1.5 h to reduce it.

[0102] The preparation conditions are listed in Table 1.

[0103] Example 8

[0104] (a) Weigh 50g of carbon nanotubes and mix them with 500g of ethylene glycol. Stir and sonicate to form an ink-like mixture. Then add 4.5g of urea, purge with air to maintain a pressure of 1.2MPa, and react at 120℃ for 6h. Filter, wash with ethanol 5 times, collect the solid, and dry the solid in an oven at 100℃ for 6h. Record this solid as A.

[0105] (b) Prepare an aqueous solution of chloropalladium acid with a Pd mass concentration of 0.002 g / mL and adjust the pH to 1 with hydrochloric acid; add 5 g of 2-methyltetrahydrofuran dropwise to A and stir continuously for 10 min, then add 1.5 mL of chloropalladium acid dropwise to A and stir for 30 min; finally add 4.5 g of γ-methylpyridine and continue stirring for 1 h to form a sludge-like substance. Dry the sludge in an oven at 120 °C for 6 h and record this as B.

[0106] (c) The dried solid was placed in 500 mL of sodium formate solution (5 wt.%) and heated to 80 °C for 1.5 h to reduce it.

[0107] The preparation conditions are listed in Table 1.

[0108] Example 9

[0109] (a) Weigh 50g of carbon nanotubes and mix them with 500g of ethylene glycol. Stir and sonicate to form an ink-like mixture. Then add 4.5g of urea, purge with air to maintain a pressure of 1.2MPa, and react at 120℃ for 6h. Filter, wash with ethanol 5 times, collect the solid, and dry the solid in an oven at 100℃ for 6h. Record this solid as A.

[0110] (b) Prepare an aqueous solution of chloropalladium acid with a Pd mass concentration of 0.002 g / mL and adjust the pH to 1 with hydrochloric acid; add 5 g of γ-methylpyridine dropwise to A and stir continuously for 10 min, then add 1.5 mL of chloropalladium acid dropwise to A and stir for 30 min; finally add 4.5 g of γ-methylpyridine and continue stirring for 1 h to form a sludge-like substance. Dry the sludge in an oven at 120 °C for 6 h and record this as B.

[0111] (c) The dried solid was placed in 500 mL of sodium formate solution (5 wt.%) and heated to 80 °C for 1.5 h to reduce it.

[0112] The preparation conditions are listed in Table 1.

[0113] Example 10

[0114] (a) Weigh 50g of carbon nanotubes and mix them with 500g of ethylene glycol. Stir and sonicate to form an ink-like mixture. Then add 4.5g of urea, purge with air to maintain a pressure of 1.2MPa, and react at 120℃ for 6h. Filter, wash with ethanol 5 times, collect the solid, and dry the solid in an oven at 100℃ for 6h. Record this solid as A.

[0115] (b) Prepare an aqueous solution of chloropalladium acid with a Pd mass concentration of 0.002 g / mL and adjust the pH to 1 with hydrochloric acid; add 5 g of γ-methylpyridine dropwise to A and stir continuously for 10 min, then add 1.5 mL of chloropalladium acid dropwise to A and stir for 30 min; finally add 4.5 g of cyclohexanone and continue stirring for 1 h to form a sludge-like substance. Dry the sludge in an oven at 120 °C for 6 h and record it as B.

[0116] (c) The dried solid was placed in 500 mL of sodium formate solution (5 wt.%) and heated to 80 °C for 1.5 h to reduce it.

[0117] The preparation conditions are listed in Table 1.

[0118] Example 11

[0119] (a) Weigh 50g of carbon nanotubes and mix them with 500g of ethylene glycol. Stir and sonicate to form an ink-like mixture. Then add 4.5g of urea, purge with air to maintain a pressure of 1.2MPa, and react at 120℃ for 6h. Filter, wash with ethanol 5 times, collect the solid, and dry the solid in an oven at 100℃ for 6h. Record this solid as A.

[0120] (b) Prepare an aqueous solution of chloropalladium acid with a Pd mass concentration of 0.002 g / mL and adjust the pH to 1 with hydrochloric acid; add 5 g of cyclohexanone dropwise into A and stir continuously for 10 min, then add 1.5 mL of chloropalladium acid dropwise into A and stir for 30 min; finally add 4.5 g of γ-methylpyridine and continue stirring for 1 h to form a sludge-like substance. Dry the sludge in an oven at 120 °C for 6 h and record it as B.

[0121] (c) The dried solid was placed in 500 mL of sodium formate solution (5 wt.%) and heated to 80 °C for 1.5 h to reduce it.

[0122] The preparation conditions are listed in Table 1.

[0123] Example 12

[0124] (a) Weigh 50g of carbon nanotubes and mix them with 500g of ethylene glycol. Stir and sonicate to form an ink-like mixture. Then add 4.5g of urea, purge with air to maintain a pressure of 1.2MPa, and react at 120℃ for 6h. Filter, wash with ethanol 5 times, collect the solid, and dry the solid in an oven at 100℃ for 6h. Record this solid as A.

[0125] (b) Prepare an aqueous solution of chloropalladium acid with a Pd mass concentration of 0.002 g / mL and adjust the pH to 1 with hydrochloric acid; add 5 g of γ-methylpyridine dropwise to A and stir continuously for 10 min, then add 1.5 mL of chloropalladium acid dropwise to A and stir for 30 min; finally add 4.5 g of N-methylpyrrolidone and continue stirring for 1 h to form a sludge-like substance. Dry the sludge in an oven at 120 °C for 6 h and record it as B.

[0126] (c) The dried solid was placed in 500 mL of sodium formate solution (5 wt.%) and heated to 80 °C for 1.5 h to reduce it.

[0127] The preparation conditions are listed in Table 1.

[0128] Example 13

[0129] (a) Weigh 50g of carbon nanotubes and mix them with 500g of ethylene glycol. Stir and sonicate to form an ink-like mixture. Then add 4.5g of urea, purge with air to maintain a pressure of 1.2MPa, and react at 120℃ for 6h. Filter, wash with ethanol 5 times, collect the solid, and dry the solid in an oven at 100℃ for 6h. Record this solid as A.

[0130] (b) Prepare an aqueous solution of chloropalladium acid with a Pd mass concentration of 0.002 g / mL and adjust the pH to 1 with hydrochloric acid; add 5 g of γ-methylpyridine dropwise to A and stir continuously for 10 min, then add 1.5 mL of chloropalladium acid dropwise to A and stir for 30 min; finally add 4.5 g of 2-methyltetrahydrofuran and continue stirring for 1 h to form a sludge-like substance. Dry the sludge in an oven at 120 °C for 6 h and record this as B.

[0131] (c) The dried solid was placed in 500 mL of sodium formate solution (5 wt.%) and heated to 80 °C for 1.5 h to reduce it.

[0132] The preparation conditions are listed in Table 1.

[0133] Example 14

[0134] (a) Weigh 50g of carbon nanotubes and mix them with 500g of ethylene glycol. Stir and sonicate to form an ink-like mixture. Then add 4.5g of urea, purge with air to maintain a pressure of 1.2MPa, and react at 120℃ for 6h. Filter, wash with ethanol 5 times, collect the solid, and dry the solid in an oven at 100℃ for 6h. Record this solid as A.

[0135] (b) Prepare an aqueous solution of chloropalladium acid with a Pd mass concentration of 0.002 g / mL and adjust the pH to 1 with hydrochloric acid; add 5 g of γ-methylpyridine dropwise to A and stir continuously for 10 min, then add 1.5 mL of chloropalladium acid dropwise to A and stir for 30 min; finally add 4.5 g of tetrahydrofuran and continue stirring for 1 h to form a sludge-like substance. Dry the sludge in an oven at 120 °C for 6 h and record it as B.

[0136] (c) The dried solid was placed in 500 mL of sodium formate solution (5 wt.%) and heated to 80 °C for 1.5 h to reduce it.

[0137] The preparation conditions are listed in Table 1.

[0138] Comparative Example 1

[0139] (a) Weigh out 50g of carbon nanotubes and record it as A;

[0140] (b) Prepare an aqueous solution of chloropalladium acid with a Pd mass concentration of 0.002 g / mL and adjust the pH to 1 with hydrochloric acid; add 11 mL of chloropalladium acid dropwise to A and stir for 1.7 h to form a sludge-like substance, and dry it in an oven at 120 °C for 6 h, which is recorded as B.

[0141] (c) The dried solid was placed in 500 mL of sodium formate solution (5 wt.%) and heated to 80 °C for 1.5 h to reduce it.

[0142] The preparation conditions are listed in Table 1.

[0143] Comparative Example 2

[0144] (a) Weigh 50 g of carbon nanotubes and mix them with 500 g of ethylene glycol. Stir and sonicate to form an ink-like mixture. Then add 4.5 g of urea, purge with air to maintain a pressure of 1.2 MPa, and react at 120 °C for 6 h. Dry in an oven at 100 °C for 6 h. Record this as A.

[0145] (b) Prepare an aqueous solution of chloropalladium acid with a Pd mass concentration of 0.002 g / mL and adjust the pH to 1 with hydrochloric acid; add 11 mL of chloropalladium acid dropwise to A and stir for 1.7 h to form a sludge-like substance, and dry it in an oven at 120 °C for 6 h, which is recorded as B.

[0146] (c) The dried solid was placed in 500 mL of sodium formate solution (5 wt.%) and heated to 80 °C for 1.5 h to reduce it.

[0147] The preparation conditions are listed in Table 1.

[0148] In the above examples and comparative examples, Pd accounts for 0.5% of the total mass of the catalyst.

[0149] Catalyst evaluation:

[0150] The catalysts of the above embodiments and comparative examples were evaluated using a batch stirred tank reactor under the following conditions:

[0151] Catalyst loading weight: 50 mg;

[0152] Composition of reaction raw materials: 200mg 4-CBA;

[0153] Reaction pressure: 1.2 MPa;

[0154] Reaction temperature: 120℃;

[0155] Reaction time: 30 min;

[0156] Catalyst evaluation methods:

[0157] The activity evaluation of the catalysts in the above embodiments and comparative examples was carried out in a 100 mL batch reactor. The reactants were added to the reactor, and the catalyst was loaded into a rotating frame inside the reactor. The reaction conditions were as described above, with a hydrogen partial pressure of 0.5 MPa. After the reaction, samples were taken to determine the 4-CBA content. The 4-CBA content was determined using an HP1100 HPLC instrument according to GB / T30921.1 standard. The experimental results are listed in Table 1.

[0158] Table 1

[0159]

[0160]

[0161]

[0162] As shown in Table 1, the palladium-on-carbon catalyst prepared by this invention can improve the catalytic activity of the catalyst, thereby significantly reducing the residual amount of 4-CBA in the process of hydrorefining terephthalic acid.

[0163] The preferred embodiments of the present invention have been described in detail above; however, the present invention is not limited thereto. Within the scope of the inventive concept, various simple modifications can be made to the technical solutions of the present invention, including combinations of various technical features in any other suitable manner. These simple modifications and combinations should also be considered as the content disclosed in the present invention and are all within the protection scope of the present invention.

Claims

1. A composition for preparing a palladium-on-carbon catalyst, comprising: Modified carbon materials with oxygen-containing functional groups, covering agents, and aqueous solutions of palladium precursors; The covering agent comprises compounds having the structures shown in Formula I and / or Formula II: R1, R2, R3, R4, and R5 are each independently selected from hydrogen, deuterium, halogen, substituted or unsubstituted C1-C10 alkyl, substituted or unsubstituted C1-C10 alkoxy, substituted or unsubstituted C1-C10 heteroalkyl, -NH2, -OH, substituted or unsubstituted amino, acyl, carbonyl, hydroxyl, or ester groups having 1-10 carbon atoms; The substituents are selected from deuterium, halogens, C1-C10 straight-chain or branched alkyl groups, C3-C10 cycloalkyl groups, C6-C20 aryl groups, -NH2, C1-C10 alkyl-substituted amino groups, or C3-C20 heteroaryl groups, and the number of substituents is selected from an integer between 1 and 10. n is 1 or 2; Preferably, the covering agent has at least one of the following physical parameter conditions: (1) Surface tension is 20-60 dyne / cm; (2) Polarizability > 7 (10 -24 cm 3 ).

2. The composition according to claim 1, characterized in that, R1, R2, R3, R4, and R5 are each independently selected from hydrogen, deuterium, halogen, substituted or unsubstituted C1-C10 alkyl groups, -NH2, -OH, substituted or unsubstituted amino groups having 1-10 carbon atoms, and hydroxyl groups. The substituents are selected from deuterium, halogens, C1-C10 straight-chain or branched alkyl groups, -NH2, and C1-C10 alkyl-substituted amino groups, and the number of substituents is selected from an integer between 1 and 5. Preferably, R1, R2, R3, R4, and R5 are each independently selected from hydrogen, deuterium, F, Cl, Br, methyl, ethyl, propyl, butyl, or -NH2; Preferably, R1, R2, R3, R4, and R5 are each independently selected from hydrogen, deuterium, methyl, ethyl, propyl, or butyl; Preferably, the covering agent comprises one or more of γ-methylpyridine, 2-methyltetrahydrofuran, or tetrahydrofuran; More preferably, the covering agent comprises γ-methylpyridine and / or 2-methyltetrahydrofuran.

3. The composition according to claim 1 or 2, characterized in that, The palladium precursor aqueous solution is selected from one or more of chloropalladic acid aqueous solution, tetraaminopalladium nitrate aqueous solution, or palladium acetate aqueous solution; Preferably, the pH of the aqueous solution of the palladium precursor is 0.1-5; Preferably, the pH of the palladium precursor aqueous solution is adjusted using hydrochloric acid and / or nitric acid.

4. The composition according to any one of claims 1-3, characterized in that, The method for preparing the modified carbon material with oxygen-containing functional groups includes: mixing carbon material, polyol and pH adjuster and reacting them; Preferably, the carbon material is selected from one or more of carbon nanotubes, carbon nanofibers, or activated carbon; preferably, it is carbon nanotubes; preferably, the aspect ratio of the carbon nanotubes is 125-12500, and / or, the outer diameter of the carbon nanotubes is 8-80 nm; and / or The polyol is selected from one or more of ethylene glycol, propylene glycol, or glycerol; and / or The pH adjuster is urea; and / or The mass ratio of the polyol to the carbon material is 5-20; and / or The mass ratio of the polyol to the pH adjuster is 200-50; The reaction temperature is 100-150℃, and / or The reaction pressure is 0.5-1.5 MPa, and / or The reaction time is 1-8 hours; and / or The reaction was carried out in an air atmosphere.

5. A method for preparing a palladium-on-carbon catalyst, comprising: The composition according to any one of claims 1-4 is subjected to reduction treatment to obtain the palladium-on-carbon catalyst.

6. The preparation method according to claim 5, characterized in that, The preparation method includes the following steps: (1) The modified carbon material with oxygen-containing functional groups is treated with a first covering agent to obtain material A; (2) The material A was treated with an aqueous solution of palladium precursor to obtain material B; (3) Reduce material B; or Material B is treated with a second covering agent to obtain material C; Material C is subjected to reduction treatment. The first covering agent and / or the second covering agent comprises: compounds having the structures shown in Formula I and / or Formula II: R1, R2, R3, R4, and R5 are each independently selected from hydrogen, deuterium, halogen, substituted or unsubstituted C1-C10 alkyl, substituted or unsubstituted C1-C10 alkoxy, substituted or unsubstituted C1-C10 heteroalkyl, -NH2, -OH, substituted or unsubstituted amino, acyl, carbonyl, hydroxyl, or ester groups having 1-10 carbon atoms; The substituents are selected from deuterium, halogens, C1-C10 straight-chain or branched alkyl groups, C3-C10 cycloalkyl groups, C6-C20 aryl groups, -NH2, C1-C10 alkyl-substituted amino groups, or C3-C20 heteroaryl groups, and the number of substituents is selected from an integer between 1 and 10. n is 1 or 2; The second covering agent has at least one of the following physical parameter conditions: (1) Surface tension is 20-60 dyne / cm; (2) Polarizability > 7 (10 -24 cm 3 ); Preferably, the first covering agent has at least one of the following physical parameter conditions: (1) Surface tension is 20-60 dyne / cm; (2) Polarizability > 7 (10 -24 cm 3 ); Preferably, the reducing agent used in the reduction treatment is one or more of sodium formate solution, formic acid, or hydrazine hydrate.

7. The preparation method according to claim 5 or 6, characterized in that, R1, R2, R3, R4, and R5 are each independently selected from hydrogen, deuterium, halogen, substituted or unsubstituted C1-C10 alkyl groups, -NH2, -OH, substituted or unsubstituted amino groups having 1-10 carbon atoms, and hydroxyl groups. The substituents are selected from deuterium, halogens, C1-C10 straight-chain or branched alkyl groups, -NH2, and C1-C10 alkyl-substituted amino groups, and the number of substituents is selected from an integer between 1 and 5.

8. The preparation method according to claim 6, characterized in that, R1, R2, R3, R4, and R5 are each independently selected from hydrogen, deuterium, F, Cl, Br, methyl, ethyl, propyl, butyl, or -NH2; R1, R2, R3, R4, and R5 are each independently selected from hydrogen, deuterium, methyl, ethyl, propyl, or butyl. Preferably, the first covering agent and / or the second covering agent comprises one or more of γ-methylpyridine, 2-methyltetrahydrofuran, or tetrahydrofuran; Preferably, the first covering agent and / or the second covering agent comprises γ-methylpyridine and / or 2-methyltetrahydrofuran; Preferably, the first covering agent and the second covering agent are the same.

9. The application of a palladium-on-carbon catalyst obtained by any one of claims 5-8 in a hydrogenation reaction.

10. A method for hydrogenating and purifying terephthalic acid, comprising: The reaction is carried out using crude terephthalic acid containing 4-CBA and hydrogen as raw materials in the presence of the palladium-on-carbon catalyst prepared by the preparation method according to any one of claims 5-8; Preferably, the pressure of the hydrogen gas is 0.1-1 MPa; and / or The reaction temperature is 100-150℃; and / or The reaction time is 20-40 minutes.

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