Catalyst for preparing dimethyl 1, 4-cyclohexanedicarboxylate by catalyzing hydrogenation of dimethyl terephthalate and preparation method of catalyst

Abstract

The invention discloses a catalyst for preparing dimethyl 1, 4-cyclohexanedicarboxylate by catalyzing hydrogenation of dimethyl terephthalate and a preparation method, and belongs to the technical field of chemical production, non-noble metal Ni salt is used as an active component, Ag is used as an auxiliary agent, a precipitator is ammonia water, and the catalyst is prepared by adopting an ammonia distillation method. According to the catalyst for preparing the 1, 4-cyclohexanedicarboxylic acid dimethyl ester, the relatively cheap non-noble metal Ni is adopted as an active component, the production cost of the catalyst is effectively reduced, the reduction temperature of the catalyst is effectively reduced by adding the auxiliary Ag, the sintering inactivation of the catalyst caused by too high reduction temperature is greatly avoided, and the ammonia distillation method is adopted, so that the production cost of the catalyst is greatly reduced. The active components are dispersed on the carrier more uniformly in a manner of dropwise adding by using a peristaltic pump, so that the active sites are increased.

Description

Technical Field

[0001] The present invention relates to the technical field of chemical production, and particularly to a catalyst for catalytic hydrogenation of dimethyl terephthalate to prepare dimethyl 1,4 - cyclohexanedicarboxylate and a preparation method thereof. Background Technique

[0002] Dimethyl 1,4 - cyclohexanedicarboxylate (DMCD) is widely used in the fields of synthetic fibers, high - performance polyester resins, polymer films, high - performance plasticizers, alkyd resins, etc. It is not only a commonly used polyester modification material. Currently, there is only one method for synthesizing DMCD, which is obtained by hydrogenating the benzene ring of DMT. Currently, DMCD products are mainly prepared by hydrogenating the benzene ring of dimethyl terephthalate (DMT). Most of the catalysts used are noble metal catalysts such as ruthenium, rhodium, and palladium, which are costly and require relatively harsh reaction conditions. In the 1960s, Eastman Chemical Company of the United States developed a Pd / Al2O3 catalyst for catalytic hydrogenation of DMT, and the selectivity of DMCD reached 95%. Subsequently, the catalyst was improved by adding metal Rh with a mass fraction of 0.01% - 0.50%. The reaction temperature was 180 °C - 200 °C, and the reaction pressure was 12.5 MPa. Finally, the yield of DMCD could reach 99%.

[0003] Zhang F Z. et al. used the urea method to in - situ synthesize MgAl - LDH on the surface of θ - Al 2 O 3 After calcining the sample, a Pd - based supported catalyst was prepared by the impregnation method. The metal Pd loading was 0.3 wt%, which was used for benzene ring hydrogenation and showed very high activity. The conversion rate of DMT and the selectivity of DMCD both reached 90%.

[0004] Li Wenlong et al. prepared a Ru - based catalyst with a relatively low loading (0.55 wt%) by the impregnation method, and investigated the influence of the surface active species of the catalyst at different calcination temperatures on the hydrogenation activity of DMT in a fixed - bed reactor, and preliminarily explored the reasons for the deactivation of the Ru - based catalyst. Finally, it was concluded that when the calcination temperature of the Ru - Al 2 O 3 catalyst was too high, agglomeration occurred. When the calcination temperature was 200 °C and 350 °C, the selectivity of the product DMCD in the reaction increased. Characterization analysis showed that impurities covered the surface active substance Ru during the reaction process, blocking some carrier pores and reducing the number of active centers, which was one of the reasons for the deactivation of the Ru / Al 2 O 3 catalyst.

[0005] Zhao Yao et al. prepared (Pd, Ni, Ru, Pt) / β - Al by the impregnation reduction method 2 O 3, in a fixed-bed reactor, the reaction was carried out at 190 °C, 6.0 MPa, and DMCD / DMT = 9. The results showed that when nickel was used as the active metal, the DMT conversion rate was only 42.4%. When platinum was supported on β-Al 2 O 3 , a lower DMT conversion rate was obtained. This result was quite different from the literature reports. The author believes that there may be an error in the catalyst preparation process, resulting in the loss of a part of the platinum metal. When the active metal was palladium, both the DMT conversion rate and selectivity reached over 90%. When ruthenium metal was supported on β-Al 2 O 3 , the DMT conversion rate reached 98.3%, but the selectivity was only 70.3%.

[0006] Zhu Zhiqing et al. prepared Ru / Al 2 O 3 catalyst by the impregnation method and reduced it with formaldehyde solution. The feed ratio of the catalyst to the raw material DMT was 1:20 (mass ratio). After purging with nitrogen in a high-pressure closed reactor, hydrogen was added, and hydrogen was replenished at any time during the reaction. After the reaction, the product was obtained by vacuum distillation. Under the conditions of 140 - 160 °C, 4 - 6 MPa, and 1 - 1.5 h, the DMT yield was over 95%. After the catalyst was recycled 3 times, the yield would decrease, but after replenishing the loss each time, it could be recycled 8 - 10 times.

[0007] In summary, DMT hydrogenation catalysts generally use noble metal catalysts (ruthenium, rhodium, palladium) as active components, which have problems such as high cost, easy deactivation, low service life, harsh reaction conditions, and relatively poor stability. Summary of the Invention

[0008] In order to solve the technical problems mentioned in the above background art, the present invention provides a catalyst for catalytic hydrogenation of dimethyl terephthalate to prepare dimethyl 1,4 - cyclohexanedicarboxylate, and the technical solution adopted is as follows:

[0009] Using non - noble metal Ni salt as the active component, Ag as the promoter, and ammonia water as the precipitant, it is prepared by the ammonia evaporation method.

[0010] The preparation method includes the following steps:

[0011] (1) After calcining γ - Al 2 O 3 , add a certain amount of pure water and prepare ammonia water according to a certain ratio;

[0012] (2) Dissolve the active component Ni salt and the Ag - containing compound as the promoter in pure water according to a certain ratio according to the loading amount;

[0013] (3) Use a peristaltic pump to add an aqueous Ag solution and prepared ammonia water to the γ-Al 2 O 3 solution at a certain rate, and maintain a certain pH value during the process. After the dropping is completed, stir for a period of time to carry out ammonia evaporation. After the loading is completed, filter by suction and calcine to obtain the sample;

[0014] (4) Dissolve the sample in water again. Use a peristaltic pump to add the active component Ni salt and prepared ammonia water to the sample solution at a certain rate, and maintain a certain pH value. After the dropping is completed, stir for a period of time to carry out ammonia evaporation. After the loading is completed, filter by suction and calcine again to obtain the catalyst.

[0015] Furthermore, the temperature of the ammonia evaporation method is 70°C - 95°C.

[0016] Furthermore, the active component Ni salt is a conventional inorganic soluble salt, and the promoter Ag is silver chloride.

[0017] Furthermore, the concentration of the ammonia water prepared in step (1) is 5% - 15%.

[0018] Furthermore, the loading amount of the active component Ni salt in step (2) is 5% - 40%, and the loading amount of the promoter silver chloride is 0.1% - 1%.

[0019] Furthermore, when dropping the aqueous Ag solution in step (3), the pH value of the γ-Al 2 O 3 solution should be maintained at 9 - 12 all the time.

[0020] Furthermore, after the dropping of the aqueous Ag solution in step (3) is completed, stir for 4 - 12 h.

[0021] Furthermore, the calcination temperature of the loaded sample in step (3) is 300°C - 800°C, and the time is 2 - 8 h.

[0022] Furthermore, as described in steps (3) and (4), use a peristaltic pump to slowly drop the metal solution and precipitant to improve the dispersion of the metal on the carrier. The calcination temperature of the loaded catalyst sample in step (4) is 350°C - 800°C, and the time is 2 - 8 h.

[0023] The present invention has the following advantages:

[0024] 1. For the catalyst for catalytic hydrogenation of dimethyl terephthalate to prepare dimethyl 1,4-cyclohexanedicarboxylate, its preparation uses relatively cheaper non-noble metal Ni as the active component, effectively reducing the production cost of the catalyst.

[0025] 2. Adding the auxiliary agent Ag effectively reduces the reduction temperature of the catalyst, greatly avoiding the sintering inactivation of the catalyst caused by too high reduction temperature.

[0026] 3. The ammonia evaporation method is adopted, and the peristaltic pump dropping method is used to make the active components more evenly dispersed on the carrier, increasing the active sites. Specific implementation mode

[0027] The technical solutions in the embodiments of the present invention will be clearly and completely described below. Obviously, the described embodiments are only a part of the embodiments of the present invention, rather than all the embodiments. All other embodiments obtained by those of ordinary skill in the art based on the embodiments of the present invention without creative efforts shall fall within the protection scope of the present invention.

[0028] Example 1

[0029] Take 10 g of γ-Al 2 O 3 carrier, roast it in a muffle furnace at a temperature of 600 °C for 8 hours to obtain the roasted γ-Al 2 O 3 carrier. Take 0.018 g of silver chloride solid, add 5 g of deionized water for dissolution, and prepare a 5% ammonia water solution; add 100 g of deionized water to the 10 g of roasted γ-Al 2 O 3 carrier, and then use a peristaltic pump to add the silver chloride aqueous solution and the 5% ammonia water solution to the γ-Al 2 O 3 solution respectively, adjust the pH value to about 9, stir for 4 h, filter, wash, dry at 100 °C for 8 h, and calcine at 450 °C for 4 h to obtain 0.1 wt% Ag-γ-Al 2 O 3 spare sample.

[0030] Take 2.05 g of nickel nitrate, add it to 50 g of deionized water, and add 0.1 wt% Ag-γ-Al 2 O 3 to 50 g of water. Use a peristaltic pump to add the nickel nitrate aqueous solution and the 5% ammonia water solution to the 0.1 wt% Ag-γ-Al 2 O 3 solution respectively, adjust the pH value to about 12, stir for 8 h, evaporate ammonia at a temperature of 80 °C until the pH value is neutral, filter, dry at 100 °C for 8 h, and calcine at 450 °C for 4 h to obtain 5 wt% Ni / 0.1 wt% Ag-γ-Al 2 O 3 catalyst.

[0031] Weigh 0.5 g of the catalyst prepared in Example 1, 1 g of DMT and 20 ml of isopropanol, add them to a high-temperature reaction kettle, tighten the reaction kettle and fill it with H 2 Replace three times to evacuate the residual air in the reaction kettle, and finally fill it with H at 4 Mpa 2 , set the stirring speed to 500 rpm to check for leaks for half an hour, raise the temperature of the reaction kettle to 100 °C and react for 4 h, with stirring at 500 rpm; after the reaction is completed, cool it to room temperature, centrifuge the reaction solution to separate it, remove the supernatant, and use gas chromatography for quantitative analysis by the internal standard method. DMT conversion rate: 62.3%, DMCD selectivity: 82.4%.

[0032] Example 2

[0033] The catalyst was prepared using the same steps as in Example 1, changing the amount of nickel nitrate taken to 4.33 g of nickel nitrate, changing the loading amount of metallic nickel, and keeping other conditions unchanged, to obtain a 10 wt% Ni / 0.1 wt% Ag-γ-Al 2 O 3 catalyst.

[0034] The reaction implementation operation steps are the same as in Example 1. Finally, the DMT conversion rate measured by the instrument is: 78.5%, and the DMCD selectivity is: 86.4%.

[0035] Example 3

[0036] The catalyst was prepared using the same steps as in Example 1, changing the amount of nickel nitrate taken to 9.75 g of nickel nitrate, changing the loading amount of metallic nickel, and keeping other conditions unchanged, to obtain a 20 wt% Ni / 0.1 wt% Ag-γ-Al 2 O 3 catalyst.

[0037] The reaction implementation operation steps are the same as in Example 1. Finally, the DMT conversion rate measured by the instrument is: 99.1%, and the DMCD selectivity is: 94.6%.

[0038] Example 4

[0039] Take 9.75 g of nickel nitrate and add it to 50 g of deionized water. Add the γ-Al 2 O 3 calcined at 600 °C to 50 g of water. Use a peristaltic pump to simultaneously add the nickel nitrate aqueous solution and 5% ammonia aqueous solution to the γ-Al 2 O 3 solution, adjust the pH value to about 12, stir for 8 h, distill ammonia at 80 °C until the pH value is slightly neutral, filter by suction, dry at 100 °C for 8 h, and calcine at 450 °C for 4 h to obtain a 20 wt% Ni-γ-Al 2 O 3 catalyst.

[0040] The reaction implementation operation steps were the same as those in Example 1. Finally, the DMT conversion rate measured by the instrument was 70.3%, and the DMCD selectivity was 83.3%.

[0041] Comparative Example 1

[0042] Take 10 g of γ-Al 2 O 3 support, and calcine it in a muffle furnace at a temperature of 600 °C for 8 hours to obtain the calcined γ-Al 2 O 3 support. Take 0.018 g of silver chloride solid and impregnate it in γ-Al 2 O 3 support for 5 h, dry it at 100 °C for 8 h, and calcine it at 450 °C for 4 h to obtain 0.1 wt% Ag-γ-Al 2 O 3 spare sample.

[0043] Take 2.05 g of nickel nitrate, and impregnate nickel nitrate in 0.1 wt% Ag-γ-Al 2 O 3 , for 5 h, dry it at 100 °C for 8 h, and calcine it at 450 °C for 4 h to obtain 5 wt% Ni / 0.1 wt% Ag-γ-Al 2 O 3 catalyst.

[0044] The reaction implementation operation steps were the same as those in Example 1. Finally, the DMT conversion rate measured by the instrument was 18.5%, and the DMCD selectivity was 78.6%.

[0045] Comparative Example 2

[0046] The catalyst was prepared using the same steps as in Comparative Example 1. Change the amount of nickel nitrate to 4.33 g of nickel nitrate, change the metal nickel loading, and keep other conditions unchanged to obtain 10 wt% Ni / 0.1 wt% Ag-γ-Al 2 O 3 catalyst.

[0047] The reaction implementation operation steps were the same as those in Example 1. Finally, the DMT conversion rate measured by the instrument was 32.8%, and the DMCD selectivity was 80.5%.

[0048] Comparative Example 3

[0049] The catalyst was prepared using the same steps as in Comparative Example 1. Change the amount of nickel nitrate to 9.75 g of nickel nitrate, change the metal nickel loading, and keep other conditions unchanged to obtain 20 wt% Ni / 0.1 wt% Ag-γ-Al 2 O 3Catalyst.

[0050] The reaction implementation operation steps are the same as those in Example 1. Finally, the DMT conversion rate measured by the instrument is 45.3%, and the DMCD selectivity is 87.5%.

[0051] The operation of the present invention is simple and convenient to use, and is suitable for comprehensive promotion and application. Although the embodiments of the present invention have been shown and described, those of ordinary skill in the art can understand that various changes, modifications, substitutions, and variations can be made to these embodiments without departing from the principles and spirit of the present invention. The scope of the present invention is defined by the appended claims and their equivalents.

Claims

1. A catalyst for catalyzing the hydrogenation of dimethyl terephthalate to prepare dimethyl 1,4-cyclohexanedicarboxylate, characterized in that: The method is prepared by using ammonia evaporation method with non-precious metal Ni salt as active component, Ag as auxiliary agent and ammonia water as precipitant.

2. The method for preparing a catalyst for preparing dimethyl 1,4-cyclohexanedicarboxylate by catalyzing the hydrogenation of dimethyl terephthalate according to claim 1, characterized in that: The preparation method comprises the following steps: (1) After calcining γ-Al2O3, add a certain amount of pure water and prepare ammonia water in a certain proportion; (2) dissolving the active component Ni salt and the auxiliary Ag-containing compound in pure water in a certain proportion according to the loading amount; (3) using a peristaltic pump to add the Ag-containing aqueous solution and the prepared ammonia water into the γ-Al2O3 solution at a certain rate, maintaining a certain pH value during the process, and after the addition is completed, stirring for a period of time to evaporate ammonia. After the loading is completed, the sample is filtered and roasted to obtain a sample; (4) The sample is dissolved in water again, and the active component Ni salt is added to the sample solution in the prepared ammonia water at a certain rate using a peristaltic pump while maintaining a certain pH value. After the addition is completed, the solution is stirred for a period of time to evaporate ammonia. After the loading is completed, the solution is filtered and calcined again to obtain the catalyst.

3. A method for preparing a catalyst for preparing dimethyl 1,4-cyclohexanedicarboxylate by catalytic hydrogenation of dimethyl terephthalate according to claim 2, characterized in that: The temperature of the ammonia distillation method is 70℃-95℃.

4. The method for preparing a catalyst for preparing dimethyl 1,4-cyclohexanedicarboxylate by catalyzing the hydrogenation of dimethyl terephthalate according to claim 2, characterized in that: The active component Ni salt is a conventional inorganic soluble salt, and the auxiliary agent Ag is silver chloride.

5. The method for preparing a catalyst for preparing dimethyl 1,4-cyclohexanedicarboxylate by catalyzing the hydrogenation of dimethyl terephthalate according to claim 2, characterized in that: The concentration of the ammonia water in step (1) is 5%-15%.

6. The method for preparing a catalyst for preparing dimethyl 1,4-cyclohexanedicarboxylate by catalyzing the hydrogenation of dimethyl terephthalate according to claim 2, characterized in that: In step (2), the loading amount of the active component Ni salt is 5%-40%, and the loading amount of the auxiliary agent silver chloride is 0.1%-1%.

7. The method for preparing a catalyst for preparing dimethyl 1,4-cyclohexanedicarboxylate by catalyzing the hydrogenation of dimethyl terephthalate according to claim 2, characterized in that: When the Ag-containing aqueous solution is added dropwise in step (3), the pH value of the γ-Al2O3 solution should be maintained at 9-12.

8. The method for preparing a catalyst for preparing dimethyl 1,4-cyclohexanedicarboxylate by catalyzing the hydrogenation of dimethyl terephthalate according to claim 2, characterized in that: After the addition of the Ag-containing aqueous solution in step (3) is completed, stirring is performed for 4-12 hours.

9. The method for preparing a catalyst for preparing dimethyl 1,4-cyclohexanedicarboxylate by catalyzing the hydrogenation of dimethyl terephthalate according to claim 2, characterized in that: The loaded sample in step (3) is calcined at a temperature of 300°C-800°C for 2-8h.

10. The method for preparing a catalyst for preparing dimethyl 1,4-cyclohexanedicarboxylate by catalyzing the hydrogenation of dimethyl terephthalate according to claim 2, characterized in that: In steps (3) and (4), a peristaltic pump is used to slowly drip the metal solution and the precipitant to improve the dispersion of the metal in the carrier. The loaded catalyst sample in step (4) is calcined at a temperature of 350°C-800°C for 2-8h.