A process for the preparation of 1,4-cyclohexanedicarboxylic acid

Abstract

A method for preparing 1,4-cyclohexanedicarboxylic acid, characterized in that terephthalic acid is reacted with hydrogen in the presence of a catalyst, said catalyst being a base earth metal and / or a transition metal and a palladium supported molecular sieve catalyst, said transition metal being selected from at least one of Cu, Zn, Cr, Mn, Fe, Co, Ni. The method improves the conversion rate and the selectivity of the target product, and improves the selectivity of the trans structure.

Description

TECHNICAL FIELD

[0001] The present application relates to a method for preparing 1,4-cyclohexanedicarboxylic acid, and more particularly, to a method for preparing 1,4-cyclohexanedicarboxylic acid by hydrogenating a benzene ring of terephthalic acid. BACKGROUND

[0002] 1,4-cyclohexanedicarboxylic acid (CHDA for short) is an important organic chemical raw material. Due to the symmetrical structure, 1,4-position substituent and alicyclic ring structure and other characteristics of CHDA, it brings many unique properties for high-performance polyester resins for coatings and glass fiber reinforced plastics, and the product is used in automobiles, transportation, industrial maintenance, aerospace, buildings, equipment and instruments, and general metal and gel coat coatings, etc. In addition, CHDA can also be used for synthesizing peptic ulcer drugs.

[0003] Traditionally, CHDA is prepared by first hydrogenating a benzene ring of dimethyl terephthalate (DMT) and then hydrolyzing. For example, CN1042327C discloses a method for hydrogenating DMT to generate the corresponding dimethyl cyclohexanedicarboxylate under low pressure conditions, and the catalyst is a second group VIII metal of palladium and nickel, platinum, ruthenium or a mixture thereof deposited on an alumina carrier, wherein 90% of the palladium is located on the alumina, and the depth from the surface of the alumina is less than 100 microns. CN102746144A discloses a method for preparing CHDA, which comprises mixing dimethyl 1,4-cyclohexanedicarboxylate raw material with sodium hydroxide and water, stirring, heating to 60-110℃, hydrolyzing for 4-12h, cooling the solution after the reaction is completed, then adding hydrochloric acid dropwise for acidolysis, and finally filtering, washing with water, and drying to obtain white powder CHDA.

[0004] In recent years, people have paid attention to the direct hydrogenation of terephthalic acid (PTA) to prepare CHDA.

[0005] US6291706 discloses a 0.1-1% Pd / C catalyst, which catalyzes the hydrogenation of the benzene ring of 5% PTA aqueous solution at a temperature of 195-230°C and a hydrogen pressure of 4.1 to 4.8 MPa, and the conversion rate of PTA is 25.3%-66.5%, and the yield of CHDA is 85.5%-98.4%. US4754064 discloses that 5% Rh / C is used as a catalyst to hydrogenate PTA in a stainless steel batch reactor, and the yield of CHDA is nearly 100%. US5430184 discloses a method for hydrogenating PTA, which uses a mixture of terephthalic acid, alcohol and water as a feedstock, the mass concentration of the terephthalic acid solution is 10%-40%, and 5% Pd / C catalyst is used to react at a temperature of 120-160°C and a hydrogen pressure of 0.19-0.95 MPa for 30-120 min, and the purity of the product CHDA reaches 98%, and the main by-products are 4-methylcyclohexanecarboxylic acid and cyclohexanecarboxylic acid. CN105582926B uses TiO2 or La2O3 as a carrier, and at least two of Pd, Pt and Zn as active components, the loadings of Pd, Pt and Zn are 4-6%, 4-6% and 4-6% respectively, and the catalyst is used to hydrogenate terephthalic acid to prepare 1,4-cyclohexanedicarboxylic acid at a temperature of 160-260°C and a hydrogen pressure of 1-10 MPa, and the selectivity of the product CHDA reaches 98%. CN100482625C uses Al2O3 as a carrier, and loads metal Ru and metal Sn according to 1:(1-5) to prepare a catalyst, which has high activity for directly hydrogenating terephthalic acid to prepare 1,4-cyclohexanedicarboxylic acid. CN102381976B uses Pd, Mg and a tetravalent metal M (M 4+ selected from Ti 4+ , Zr 4+ , Sn 4+ , Mn 4+ , Cr 4+ one or more) to prepare a catalyst, which is used to catalyze the preparation of dimethyl 1,4-cyclohexanedicarboxylate from dimethyl terephthalate at a temperature of 150-300°C and a hydrogen pressure of 3-8 MPa absolute pressure, and the method has the characteristics of less amount of active components and high catalytic activity.

[0006] Although the disclosed terephthalic acid hydrogenation catalyst has good catalytic activity, due to the low solubility of terephthalic acid in water and the stability of the aromatic ring, the reaction temperature and pressure of the catalytic hydrogenation of terephthalic acid are relatively harsh, and the trans-CHDA proportion is less than 50%. SUMMARY

[0007] The present application aims at solving the problems of harsh reaction conditions and low trans-structure selectivity in the preparation of 1,4-cyclohexanedicarboxylic acid by hydrogenation of terephthalic acid in the prior art, and provides a method for hydrogenating terephthalic acid, which has mild hydrogenation conditions and high selectivity of trans-1,4-cyclohexanedicarboxylic acid.

[0008] Therefore, the present application provides a method for preparing 1,4-cyclohexanedicarboxylic acid, characterized in that terephthalic acid is reacted with hydrogen in the presence of a catalyst, and the catalyst is a molecular sieve catalyst loaded with an alkaline earth metal and / or a transition metal and palladium, and the transition metal is at least one selected from Cu, Zn, Cr, Mn, Fe, Co and Ni.

[0009] In the method provided by the present application, the catalyst is a molecular sieve loaded with an alkaline earth metal and / or a transition metal and palladium. The alkaline earth metal is preferably Mg and / or Ba, and the transition metal is at least one selected from Zn, Cu, Mn and Fe. The molecular sieve is selected from one of mordenite, beta zeolite, Y zeolite, MCM-22 zeolite and ZSM-5 zeolite, and the preferred molecular sieve is Y zeolite.

[0010] In the catalyst, the content of the alkaline earth metal is 0.1% to 10%, and preferably 0.5% to 5%, and the content of the transition metal is 0.1% to 10%, and preferably 1% to 5%. The ratio of palladium to the alkaline earth metal and / or the transition metal is 0.2 to 4.

[0011] Preferably, the molecular sieve catalyst loaded with an alkaline earth metal and / or a transition metal and palladium in the present application is obtained by impregnating, drying, calcining and reducing a molecular sieve carrier modified by an alkaline earth metal and / or a transition metal with an impregnation solution containing a palladium precursor. More specifically, the preparation of the molecular sieve catalyst loaded with an alkaline earth metal and / or a transition metal and palladium in the present application comprises the following steps: stirring a molecular sieve and a salt solution of an alkaline earth metal and / or a transition metal at 70 to 95°C for 10 to 24 hours, and then washing, filtering, drying and calcining to obtain a modified molecular sieve; impregnating, drying, calcining and reducing the modified molecular sieve with an impregnation solution containing a palladium precursor.

[0012] Because the precursors of alkaline earth metal and / or transition metal are easy to hydrolyze, the salt solution of the alkaline earth metal and / or transition metal needs to be adjusted to a pH value of 3-5 with an acid. In order to have a higher Pd dispersion and smaller particles, preferably, the impregnation solution containing the palladium precursor is adjusted to a pH value of 9-11 with a base. The acid is one of hydrochloric acid, nitric acid, sulfuric acid and acetic acid, and the base is one of ammonia and ethylenediamine. Preferably, the impregnation is carried out under normal pressure, the impregnation temperature is 25-110°C, and the impregnation time is 1-12 hours. The preparation of the molecular sieve catalyst also includes the steps of vacuumizing the modified molecular sieve before the impregnation and removing water after the impregnation.

[0013] The method provided by the present application preferably uses water as the solvent. The concentration of terephthalic acid is 1-30 wt%, preferably 2-15 wt%. The mass ratio of terephthalic acid to catalyst is (15-5):1, preferably (10-5):1. The reaction of terephthalic acid with hydrogen in the presence of the catalyst is carried out at a reaction temperature of 80-200°C and a hydrogen pressure of 1-8 MPa, preferably at a reaction temperature of 100-150°C and a hydrogen pressure of 2-5 MPa.

[0014] The method for preparing 1,4-cyclohexane dicarboxylic acid provided by the present application can be carried out in various reaction devices, such as a fixed bed, a slurry bed, a high-pressure reaction kettle and the like. In the present specification, a high-pressure reaction kettle is used to evaluate the effect of the method for preparing 1,4-cyclohexane dicarboxylic acid, but the reaction device of the present application is not limited thereto.

[0015] The method for preparing 1,4-cyclohexane dicarboxylic acid provided by the present application has the following advantages: (1) the catalyst used is modified by ion exchange with alkaline earth metal and / or transition metal to enhance the L acidity of the catalyst, and then loaded with noble metal Pd to promote the dispersion of Pd and improve the activity of the catalyst; (2) in the hydrogenation of terephthalic acid, the two oxygen atoms on the para-carboxyl group are adsorbed by the L acidic sites on the carrier, and then the benzene ring of terephthalic acid is hydrogenated by the active metal atoms to generate the target product 1,4-cyclohexane dicarboxylic acid; (3) the harsh conditions of the hydrogenation of terephthalic acid are relieved, the conversion rate is greatly improved, and the selectivity of the target product and the selectivity of the trans structure are improved. For example, the conversion rate of terephthalic acid is increased by 7.3-16.9%, and the content of trans 1,4-cyclohexane dicarboxylic acid is increased from about 70% to 85%-98.4%. DETAILED DESCRIPTION

[0016] The present application is described in detail below by way of examples. It should be understood that the examples described herein are only used to illustrate and explain the present application, and are not used to limit the present application.

[0017] The present application evaluates the reaction of terephthalic acid hydrogenation to prepare 1,4-cyclohexane dicarboxylic acid using terephthalic acid conversion, 1,4-cyclohexane dicarboxylic acid yield and selectivity of trans-1,4-cyclohexane dicarboxylic acid as indexes. The reaction product is analyzed on a gas chromatograph.

[0018] Terephthalic acid (PTA) conversion is calculated by the following formula:

[0019]

[0020] 1,4-cyclohexane dicarboxylic acid (CHDA) yield is calculated by the following formula:

[0021]

[0022] Wherein:

[0023] m CHDA : mass of CHDA in product (g);

[0024] m1: mass of product (g);

[0025] m2: sample amount (g);

[0026] m: mass of raw material (g);

[0027] M PTA : molar mass of PTA (g / mol);

[0028] M CHDA : molar mass of CHDA (g / mol);

[0029] Selectivity of trans-1,4-cyclohexane dicarboxylic acid (Trans-CHDA) is calculated by the following formula:

[0030] Trans-CHDA selectivity = δ trans-CHDA x 100%, δ trans-CHDA is the ratio of integral area of Trans-CHDA component to integral area of product.

[0031] Example 1

[0032] (1) Modified molecular sieve carrier: configure an aqueous solution of magnesium nitrate, adjust the pH to 5 with nitric acid. The molecular sieve is completely immersed in the magnesium nitrate solution at a mass ratio of 1:6, wherein the mass fraction of Mg is 0.5%, stirred at 70°C for 24h, then filtered, washed, at 120°C for 12h, and finally calcined at 500°C for 3h.

[0033] (2) Preparation of catalyst: according to the Pd content of 1% in the catalyst, the corresponding mass of tetraammine palladium nitrate was weighed, and then dissolved in 25 g of aqueous solution, and the pH value was adjusted to 11 by adding ammonia water to form a metal impregnation solution. The impregnation solution was added dropwise to the modified molecular sieve, and impregnated at 60°C for 6h, and then the excess water was removed by rotary evaporation. The obtained catalyst precursor was dried at 110°C for 12h, calcined at 500°C for 3h, and then reduced in a hydrogen atmosphere at 150°C for 3h to obtain catalyst A1. The composition of catalyst A1 is shown in Table 1.

[0034] (3) Preparation of 1,4-cyclohexane dicarboxylic acid: 0.5g of catalyst A1 obtained in step (2) and 5g of terephthalic acid were added to an autoclave, and 250g of water was added. The autoclave was replaced with nitrogen and hydrogen for 3 times respectively, and then hydrogen was introduced until the pressure reached 5MPa. The reaction temperature was maintained at 100°C, and the product was analyzed after 6h of reaction. The results are shown in Table 1.

[0035] Example 2 and Example 3

[0036] The same method as in Example 1 was used to prepare the catalyst, except that:

[0037] In step (1), the mass fraction of Mg was changed to 2.5%, 5% respectively. The stirring temperature and time were changed to 80°C, 15h, 90°C, 10h respectively, and the calcination temperature was changed to 550°C, 600°C respectively.

[0038] In step (2), the mass fraction of Pd was changed to 1.5%, 2% respectively. Catalyst A2 and catalyst A3 were obtained respectively. The results are shown in Table 1.

[0039] Example 4

[0040] (1) Modification of molecular sieve carrier. A barium nitrate solution was prepared, and the pH was adjusted to 5 with nitric acid. The molecular sieve was completely immersed in the barium nitrate solution with a mass ratio of 1:6, and the mass fraction of Ba was 0.5%. The mixture was stirred at 70°C for 24h, then filtered, washed, dried at 120°C for 12h, and finally calcined at 500°C for 3h.

[0041] (2) Preparation of catalyst: according to the Pd content of 1% in the catalyst, the corresponding mass of tetraammine palladium nitrate was weighed, and then dissolved in 25 g of aqueous solution, and the pH value was adjusted to 11 by adding ammonia water to form a metal impregnation solution. The impregnation solution was added dropwise to the modified molecular sieve, and impregnated at 60°C for 6h, and then the excess water was removed by rotary evaporation. The obtained catalyst precursor was dried at 110°C for 12h, calcined at 500°C for 3h, and then reduced in a hydrogen atmosphere at 150°C for 3h to obtain catalyst A1. The composition of catalyst A1 is shown in Table 1.

[0042] (3) Preparation of 1,4-cyclohexane dicarboxylic acid: 1 g of catalyst A4 obtained in step (2) and 5 g of terephthalic acid were added to an autoclave, and 34 g of water was added. The autoclave was replaced with nitrogen and hydrogen for 3 times, respectively, and then hydrogen was introduced until the pressure reached 2 MPa. The reaction temperature was maintained at 150 °C, and after 4 h of reaction, the product was analyzed. The results are shown in Table 1.

[0043] Example 5 and Example 6

[0044] The same method as in Example 4 was used to prepare the catalyst, except that:

[0045] In step (1), the mass fraction of Ba was changed to 2.5%, 5%, respectively. The stirring temperature and time were changed to 80 °C, 15 h, 95 °C, 10 h, respectively. The calcination temperature was changed to 550 °C, 600 °C, respectively.

[0046] In step (2), the mass fraction of Pd was changed to 1.5%, 2%. Catalyst A5 and catalyst A6 were obtained, respectively. The results are shown in Table 1.

[0047] Example 7

[0048] (1) Modification of the molecular sieve carrier. A zinc chloride solution was prepared, and the pH was adjusted to 4 with hydrochloric acid. The molecular sieve was completely immersed in the zinc chloride solution with a mass ratio of 1:6, where the mass fraction of Zn was 1%, and stirred at 70 °C for 24 h, then filtered, washed, and calcined at 120 °C for 12 h, and finally calcined at 500 °C for 3 h.

[0049] (2) Preparation of the catalyst. According to the Pd content of 1% in the catalyst, the corresponding mass of palladium tetraammine nitrate was weighed, and then dissolved in 60 g of water solution. The pH value was adjusted to 11 by adding ammonia water to form a metal impregnation solution. The impregnation solution was added dropwise to the modified molecular sieve, and impregnated at 90 °C for 3 h, and then the excess water was removed by rotary evaporation. The obtained catalyst precursor was dried at 110 °C for 12 h, and then the dried catalyst precursor was reduced at 150 °C in a hydrogen atmosphere for 3 h to obtain the final catalyst A7.

[0050] (3) Preparation of 1,4-cyclohexane dicarboxylic acid. 0.5 g of catalyst A7 obtained in step (2) and 5 g of terephthalic acid were added to an autoclave, and 100 g of water was added. The autoclave was replaced with nitrogen and hydrogen for 3 times, respectively, and then hydrogen was introduced until the pressure reached 3 MPa. The reaction temperature was maintained at 120 °C, and after 5 h of reaction, the product was analyzed. The results are shown in Table 1.

[0051] Example 8 and Example 9

[0052] The same method as in Example 7 was used to prepare the catalyst, except that:

[0053] In step (1), the mass fraction of Zn was changed to 2.5%, 5% respectively. The stirring temperature and time were changed to 80°C, 15h; 95°C, 10h respectively. The calcination temperature was changed to 550°C, 600°C respectively.

[0054] In step (2), the mass fraction of Pd was changed to 1.5%, 2% respectively. Catalyst A8 and catalyst A9 were obtained respectively. The results are shown in Table 1.

[0055] Example 10

[0056] (1) Modification of molecular sieve carrier. A copper sulfate solution was prepared, and the pH was adjusted to 3 with hydrochloric acid. The molecular sieve was completely immersed in the copper sulfate solution with a mass ratio of 1:6, wherein the mass fraction of Cu was 1%, and the stirring was carried out at 70°C for 24h, followed by filtration, washing, drying at 120°C for 12h, and finally calcination at 500°C for 3h.

[0057] (2) Preparation of catalyst. According to the Pd content of 1% in the catalyst, the corresponding mass of tetraammine palladium nitrate was weighed, and then dissolved in 45g of aqueous solution. The pH value was adjusted to 11 by adding ammonia water to form a metal impregnation solution. The impregnation solution was added dropwise to the modified molecular sieve, and impregnated at 80°C for 4.5h, and then the excess water was removed by rotary evaporation. The obtained catalyst precursor was dried at 110°C for 12h, and then the dried catalyst precursor was reduced at 150°C in a hydrogen atmosphere for 3h to obtain the final catalyst A10.

[0058] (3) Preparation of 1,4-cyclohexane dicarboxylic acid. 0.5g of catalyst A10 obtained in step (2) and 5g of terephthalic acid were added to an autoclave with 100g of water. The autoclave was replaced with nitrogen and hydrogen for 3 times respectively, and then hydrogen was introduced until the pressure reached 3MPa. The reaction temperature was maintained at 120°C, and the reaction was carried out for 5h. The product was analyzed, and the results are shown in Table 1.

[0059] Example 11 and Example 12

[0060] The same method as in Example 10 was used to prepare the catalyst, except that:

[0061] In step (1), the mass fraction of Cu was changed to 2.5%, 5% respectively. The stirring temperature and time were changed to 80°C, 15h; 95°C, 10h respectively. The calcination temperature was changed to 550°C, 600°C respectively.

[0062] In step (2), the mass fraction of Pd was changed to 1.5%, 2% respectively. Catalyst A11 and catalyst A12 were obtained respectively. The results are shown in Table 1.

[0063] Example 13

[0064] (1) Modification of the molecular sieve carrier. A manganese acetate aqueous solution was prepared, and the pH was adjusted to 5 with acetic acid. The molecular sieve was completely immersed in a copper sulfate solution with a mass ratio of 1:6, wherein the mass fraction of Mn was 1%, and stirred at 70°C for 24 h, then filtered, washed, at 120°C for 12 h, and finally calcined at 500°C for 3 h.

[0065] (2) Preparation of the catalyst. The catalyst was prepared according to the method of Example 10, and a metal solution was first prepared, impregnated, dried, calcined, and reduced to obtain catalyst A13

[0066] (3) Preparation of 1,4-cyclohexane dicarboxylic acid. The method of Example 10 was used, and the results are shown in Table 1.

[0067] Example 14 and Example 15

[0068] The catalyst was prepared according to the same method as in Example 13, except that:

[0069] In step (1), the mass fraction of Cu was changed to 2.5% and 5%, respectively. The stirring temperature and time were changed to 80°C for 15 h and 95°C for 10 h, respectively. The calcination temperature was changed to 550°C and 600°C, respectively.

[0070] In step (2), the mass fraction of Pd was changed to 1.5% and 2%, respectively. Catalyst A14 and catalyst A15 were obtained, respectively. The results are shown in Table 1.

[0071] Example 16

[0072] (1) Modification of the molecular sieve carrier. A ferrous chloride aqueous solution was prepared, and the pH was adjusted to 3 with hydrochloric acid. The molecular sieve was completely immersed in a copper sulfate solution with a mass ratio of 1:6, wherein the mass fraction of Fe was 1%, and stirred at 70°C for 24 h, then filtered, washed, at 120°C for 12 h, and finally calcined at 500°C for 3 h.

[0073] (2) Preparation of the catalyst. The catalyst was prepared according to the method of Example 10, and a metal solution was first prepared, impregnated, dried, calcined, and reduced to obtain catalyst A16

[0074] (3) Preparation of 1,4-cyclohexane dicarboxylic acid. The method of Example 10 was used, and the results are shown in Table 1.

[0075] Example 17 and Example 18

[0076] The catalyst was prepared according to the same method as in Example 16, except that:

[0077] In step (1), the mass fraction of Cu was changed to 2.5% and 5%, respectively. The stirring temperature and time were changed to 80°C for 15 h and 95°C for 10 h, respectively. The calcination temperature was changed to 550°C and 600°C, respectively.

[0078] In step (2), the mass fraction of Pd was changed to 1.5% and 2%, respectively, to obtain catalysts A17 and A18, respectively. The results are shown in Table 1.

[0079] Example 19

[0080] (1) Modification of the molecular sieve carrier. Magnesium nitrate and zinc nitrate were weighed and dissolved in water to form an aqueous solution, and nitric acid was added to adjust the pH to prevent hydrolysis. The mass fractions of Mg and Zn were 1.5% and 1%, respectively. The solution was stirred at 80°C for 12h, then filtered and washed. The solution was then dried at 120°C for 12h, and finally calcined at 550°C for 3h.

[0081] (2) Preparation of the catalyst. According to the Pd content of 1% in the catalyst, the corresponding mass of tetraammine palladium nitrate was weighed and then dissolved in 45g of water solution. Ammonia water was added to adjust the pH value to 11 to form a metal impregnation solution. The impregnation solution was added dropwise to the modified molecular sieve, and the mixture was impregnated at 80°C for 4.5h. Excess water was removed by rotary evaporation. The obtained catalyst precursor was dried at 110°C for 12h, and then reduced at 150°C under hydrogen atmosphere for 3h to obtain catalyst A19.

[0082] (3) Preparation of 1,4-cyclohexane dicarboxylic acid. 0.5g of catalyst A19 obtained in step (2) and 5g of terephthalic acid were added to an autoclave, and 100g of water was added. The autoclave was replaced with nitrogen and hydrogen for 3 times, respectively, and then hydrogen was introduced until the pressure reached 3MPa. The reaction temperature was maintained at 120°C, and the reaction was carried out for 5h. The product was analyzed, and the results are shown in Table 1.

[0083] Example 20

[0084] The same method as in Example 19 was used to prepare the catalyst, except that:

[0085] In step (1), the mass fractions of barium nitrate and ferrous chloride solution were changed to 1.5% and 1%, respectively, to obtain catalyst A20. The results are shown in Table 1.

[0086] Example 21

[0087] The same method as in Example 1 was used to prepare the catalyst, except that:

[0088] In step (1), the molecular sieve was mordenite, and the mass fraction of Mg was 2.5%, to obtain catalyst A21. The results are shown in Table 1.

[0089] Example 22

[0090] The same method as in Example 7 was used to prepare the catalyst, except that:

[0091] The molecular sieve in step (1) is BETA molecular sieve, and the mass fraction of Zn is 2.5%, to obtain catalyst A22. The results are shown in Table 1.

[0092] Example 23

[0093] The catalyst is prepared by the same method as in Example 10, except that:

[0094] The molecular sieve in step (1) is MCM-22 molecular sieve, and the mass fraction of Cu is 2.5%, to obtain catalyst A23. The results are shown in Table 1.

[0095] Example 24

[0096] The catalyst is prepared by the same method as in Example 16, except that:

[0097] The molecular sieve in step (1) is ZSM-5 molecular sieve, and the mass fraction of Fe is 2.5%, to obtain catalyst A24. The results are shown in Table 1.

[0098] Comparative Examples 1-5 are used to illustrate the reaction of catalysts prepared without modification of the molecular sieve when preparing 1,4-cyclohexanedicarboxylic acid.

[0099] Comparative Example 1

[0100] (1) Preparation of catalyst. A Pd / mordenite molecular sieve catalyst is prepared, and according to the Pd content in the catalyst being 1%, the corresponding mass of palladium tetraammine nitrate is weighed, and then dissolved in a 45 g aqueous solution, and the pH value is adjusted to 11 by adding ammonia water to form a metal impregnation solution. The impregnation solution is added dropwise to the pretreated carrier, and impregnated at 80°C for 4.5 h, and then the excess water is removed by rotary evaporation. The obtained catalyst precursor is dried at 110°C for 12 h, and then the dried catalyst precursor is reduced in a hydrogen atmosphere at 150°C for 3 h to obtain the final comparative catalyst B1.

[0101] (3) Preparation of 1,4-cyclohexanedicarboxylic acid. 0.5 g of catalyst B1 obtained in step (2) and 5 g of terephthalic acid are added to an autoclave, and 100 g of water is added. The autoclave is replaced with nitrogen and hydrogen for 3 times respectively, and then hydrogen is introduced to increase the pressure to 3 MPa, and the reaction temperature is maintained at 120°C, and the product is analyzed after 5 h of reaction, and the results are shown in Table 1.

[0102] Comparative Examples 2-5

[0103] The carriers in Comparative Examples 2-5 are BETA, Y, MCM-22, and ZSM-5, respectively, which are denoted as comparative catalysts B2, B3, B4, and B5, and the results are shown in Table 1.

[0104] Table 1

[0105]

[0106] From the result data of Table 1, it can be seen that the hydrogenation activity and the selectivity of trans-1,4-cyclohexane dicarboxylic acid of the catalysts are obviously enhanced after the modification of the molecular sieve carrier with alkaline earth metal and / or transition metal, wherein the conversion rate of terephthalic acid is increased by 7.3-16.9%, the content of trans-1,4-cyclohexane dicarboxylic acid is increased from about 70% to 85%-98.4%, and the catalyst activity and the selectivity of the target product are greatly improved.

Claims

1. A process for the preparation of 1,4-cyclohexanedicarboxylic acid, characterized in that, The terephthalic acid is reacted with hydrogen in the presence of a catalyst at a temperature of 100-150℃ and a hydrogen pressure of 2-5MPa; the catalyst is a base earth metal and transition metal and palladium supported molecular sieve catalyst, the base earth metal is Mg and / or Ba, the transition metal is at least one selected from Zn, Fe, and the molecular sieve is Y-type zeolite; the base earth metal and transition metal and palladium supported molecular sieve catalyst is obtained by stirring a molecular sieve with a base earth metal and transition metal salt solution at 70-95℃ for 10-24h, then washing, filtering, drying and calcining to obtain a modified molecular sieve, impregnating the modified molecular sieve with an impregnation liquid containing a palladium precursor, drying, calcining and reducing; wherein the base earth metal and transition metal salt solution is adjusted to a pH value of 3-5 with an acid, and the impregnation liquid containing the palladium precursor is adjusted to a pH value of 9-11 with a base.

2. The process according to claim 1, wherein the amount of the catalyst is 0.1 to 10 parts by weight, based on 100 parts by weight of the total weight of the catalyst. The content of the base earth metal is 0.1%-10%, and the content of the transition metal is 0.1%-10%.

3. The process of claim 1, wherein the amount of said catalyst is from 0.1 to 10 wt.%, based on the total weight of the catalyst. The content of the base earth metal is 0.5%-5%, and the content of the transition metal is 1%-5%.

4. The method according to any one of claims 1 to 3, wherein, The weight ratio of palladium to the base earth metal and the transition metal is 0.2-4.

5. The method of claim 1, wherein, The impregnation is carried out under normal pressure, the impregnation temperature is 25-110℃, and the impregnation time is 1-12h.

6. The method of claim 1, wherein, The steps of vacuumizing the modified molecular sieve before the impregnation and removing water after the impregnation are further included.

7. The method of claim 1, wherein, The acid is one of hydrochloric acid, nitric acid, sulfuric acid and acetic acid, and the base is one of ammonia and ethylenediamine.

8. The method of claim 1, wherein, The palladium-containing precursor is at least one of palladium chloride, palladium nitrate, palladium acetate, tetraammine palladium nitrate and ammonium chloropalladate.

9. The method of claim 1, wherein, Water is used as the solvent.

10. The method of claim 1, wherein, The mass ratio of the terephthalic acid to the catalyst is (15-5):

1.

11. The method of claim 10, wherein, The mass ratio of the terephthalic acid to the catalyst is (10-5):1.

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