Preparation method of dimethyl terephthalate hydrogenation catalyst

Abstract

The invention discloses a preparation method of a dimethyl terephthalate hydrogenation catalyst, and belongs to the technical field of catalyst preparation, and the preparation method comprises the following steps: S1, taking a carbonate solution, a carrier solution and an active metal salt solution as raw materials, mixing and reacting to obtain a blackish green suspension; and S2, adding alkali liquor to adjust the pH value to be alkaline, turning the color of the turbid liquid from dark green to brown, standing, centrifugally drying, roasting, and carrying out reduction reaction to obtain the catalyst. The invention relates to a preparation method of a dimethyl terephthalate hydrogenation catalyst, the process flow is simple, the prepared catalyst has high catalytic activity, good stability and long service life, the DMT hydrogenation conversion rate is high, and the catalyst can be repeatedly recycled after being cleaned by a solvent or being subjected to subsequent activation treatment. The preparation cost and the production cost of the catalyst are further reduced, and the catalyst has very high economic benefits and industrial application prospects.

Description

Technical Field

[0001] The present invention relates to the field of catalyst preparation, and in particular to a method for preparing a catalyst for hydrogenation of dimethyl terephthalate. Background Art

[0002] Dimethyl 1,4-cyclohexanedicarboxylate (DMCD) is an important organic chemical raw material and pharmaceutical intermediate, and the preparation of DMCD is generally obtained by hydrogenation of dimethyl terephthalate (DMT). In addition, 1,4-cyclohexanedimethanol (CHDM) can be prepared by further hydrogenation of DMCD for the production of high-performance polyesters and copolyesters, such as PETG, Spectar copolyester, PCT, and PCTA. With the continuous update of China's chemical industry, the market demand for DMCD is gradually increasing.

[0003] Catalysts are the key factors in heterogeneous catalytic hydrogenation processes. Different types of catalysts can affect the types of intermediates, the formation of products and the migration of intermediates during the reaction, thereby affecting the activity and selectivity of the reaction. In recent years, scientists have extensively explored and studied catalysts for the preparation of DMCD from DMT. Currently, various catalysts for this reaction have been reported in the literature and patents. Commonly used catalysts for the preparation of DMCD consist of a main active component, a promoter, and a support. The promoters mainly consist of metal elements of Group IIA or IB-VIIB, such as Ca, Ba, Mg, Mo, Mn, Cu, Cr, Zn, etc., and metal elements of Group VIII, such as Fe, Co, Ni, Rh, Ru, Ir, Pt. The main active components are generally metal elements such as Pb, Ru, Ni, and Cu. The support is generally alumina crystallized as α, θ, δ, γ, η, or a mixture thereof. Currently, the catalysts for this reaction are mainly palladium-based, ruthenium-based, and nickel-based catalysts. However, all of the above catalysts have certain defects. For example, the price of palladium noble metal is relatively expensive, and the side reactions during the catalytic process will further inhibit the activity of the catalyst, resulting in a reduction in the catalyst life. Compared with noble metals such as Pt and Pb, the price of Ru is lower, but Ru-based catalysts are prone to over-hydrogenation of DMT, resulting in an increase in the content of by-products and easy deactivation of the catalyst. There are also documents in the prior art that record the preparation of a 0.4% Ru-2Ni% / CNT catalyst using carbon nanotubes as a support. In the DMT hydrogenation reaction, the raw materials are only converted by 68.37%, and the product selectivity is 91.5%, but the reaction effect is not ideal. Although nickel-based catalysts reduce the reaction conditions and production costs to a certain extent and show good stability, the selectivity of DMCD is not high when using nickel-based catalysts without adding promoters. Further improvement and research on the preparation method and component structure of nickel-based catalysts are required for industrial application.

[0004] Based on the above, the present invention provides a preparation method for a DMT hydrogenation catalyst. The prepared catalyst has a high conversion rate for this reaction, and the catalyst preparation is simple and easy to promote. Summary of the Invention

[0005] The object of the present invention is to provide a preparation method for a dimethyl terephthalate hydrogenation catalyst to solve the problems in the background technology.

[0006] To achieve the above object, the present invention provides a preparation method for a dimethyl terephthalate hydrogenation catalyst, including the following steps:

[0007] S1. Using a carbonate solution, a carrier solution, and an active metal salt solution as raw materials, after mixing and reacting, a dark green suspension is obtained;

[0008] S2. Adding an alkali solution to adjust the pH to alkaline, the color of the suspension changes from dark green to coffee color. After standing, centrifuging and drying, and through calcination and reduction reactions, a catalyst is obtained.

[0009] Preferably, the specific steps of S1 are: adding the carbonate solution to the carrier solution and mixing evenly to obtain a mixed solution, and dropping the active metal salt solution into the mixed solution for reaction, so that the color of the suspension changes from white to dark green;

[0010] Or adding the carbonate solution and the active metal salt solution together to the carrier solution and mixing evenly, so that the color of the suspension changes from white to dark green.

[0011] Preferably, in S1, the carbonate is sodium carbonate; the carrier is one or more of β-zeolite, USY zeolite, Al-SBA-15, ZSM-5, silica, and alumina.

[0012] Preferably, in S1, the active metal salt is a mixture of palladium salt, nickel salt, cobalt salt, molybdenum salt, iron salt, manganese salt, chromium salt, and zinc salt.

[0013] Preferably, the percentages of each substance in the active metal salt are Pd 1%, Ni 42.08%, Co 30%, Mo 20.1%, Fe 20.0%, Mn 10.0%, Cr 10.0%, and Zn 10.0%.

[0014] Preferably, in S1, the mass ratio of the carrier to the carbonate is 1-6:3.

[0015] Preferably, in S2, the concentration of the alkali solution is 0.1-3 mol / L, and the alkali solution is sodium hydroxide.

[0016] Preferably, in S2, the temperature during pH adjustment is 30-100 °C, the calcination temperature is 400-800 °C, and the calcination time is 2-10 h; the reduction temperature is 300-600 °C, and the reduction time is 2-6 h.

[0017] The present invention prepares a catalyst for hydrogenation of dimethyl terephthalate through the above preparation method.

[0018] Preferably, the prepared catalyst is applied to the hydrogenation of dimethyl terephthalate to prepare dimethyl 1,4-cyclohexanedicarboxylate.

[0019] Therefore, the present invention relates to a preparation method of a catalyst for hydrogenation of dimethyl terephthalate, having the following beneficial effects:

[0020] (1) In the present invention, a salt solution of sodium carbonate and sodium hydroxide or a mixed solution of ammonia water and ammonium bicarbonate is used as a precipitant, the effects of different load contents of active metals on the reaction performance are compared, and it is determined that the final active components contain Pd, Co, Mo, Mn, Cu, Fe, Ni, Cr, Zn, Mg, and their percentages are limited. By preparing the catalyst with the above raw materials combined with a carrier, the obtained nickel-based catalyst is the optimal catalyst for DMT hydrogenation.

[0021] (2) The greatest advantage of the catalyst prepared in the present invention is that it has the advantage of being applied to an industrial fixed-bed reaction device for continuous reaction to achieve continuous production, improving the production scale, and the product quality is easy to control; its preparation process is simple, the prepared catalyst has the advantages of high catalytic activity, good stability and long service life, high DMT hydrogenation conversion rate, and can be repeatedly recovered and used after solvent cleaning or subsequent activation treatment, further reducing the catalyst preparation cost and production cost, and having high economic benefits and industrial application prospects.

[0022] The following further describes the technical solution of the present invention in detail through examples. Detailed implementation mode

[0023] The following further illustrates the technical solution of the present invention through examples.

[0024] To make the objectives, technical solutions and advantages of the embodiments of the present invention clearer, the technical solutions in the embodiments of the present invention will be clearly and completely described below. Obviously, the described embodiments are some, but not all, of the embodiments of the present invention.

[0025] Example 1

[0026] A catalyst was prepared using sodium carbonate and sodium hydroxide as precipitants, and the specific steps are as follows:

[0027] S1. Add 74 g of β zeolite and a certain amount of deionized water to a flask, dissolve it completely, and place it in the flask to obtain a carrier solution; then take 53 g of Na2CO3 and prepare an aqueous solution with a concentration of 5 mol / L, add it to the carrier solution, and mix well to obtain a mixed solution;

[0028] Take 0.028 g of PdCl2, 50 g of Ni(NO3)2·6H2O, 30 g of Co(NO3)2·6H2O, 10 g of Fe(NO3)2·9H2O, 10 g of (NH4)6Mo7O 24 ·4H2O, 10 g of Mn(NO3)2·4H2O, 10 g of Zn(NO3)2·6H2O, 10 g of Cr(NO3)3·9H2O, add a certain amount of water, stir and mix to dissolve them completely to obtain a mixed metal salt solution;

[0029] Dropwise add the mixed metal salt solution to the mixed solution, and the solution turns from a white suspension to a dark green color;

[0030] S2. Adjust the pH value of the suspension to 14 with 1 mol / L sodium hydroxide solution, stir at a constant temperature of 70 °C for 14 h, the solution turns from a dark green suspension to a coffee color, let it stand overnight, then centrifuge and dry, and finally calcine at 550 °C for 10 h. After the calcination is completed, use hydrogen as a reducing agent for the reduction reaction, control the reduction temperature at 600 °C, and react for 6 h to obtain the target catalyst.

[0031] Example 2

[0032] Prepare a catalyst using sodium carbonate and sodium hydroxide as precipitants, and the specific steps are as follows:

[0033] S1. Add 74 g of ZSM-5 and a certain amount of deionized water to a flask, dissolve it completely, and place it in the flask to obtain a carrier solution;

[0034] Then take 53 g of Na2CO3 and prepare an aqueous solution with a concentration of 5 mol / L; take 0.028 g of PdCl2, 50 g of Ni(NO3)2·6H2O, 30 g of Co(NO3)2·6H2O, 10 g of Fe(NO3)2·9H2O, 10 g of (NH4)6Mo7O 24 ·4H2O, 10 g of Mn(NO3)2·4H2O, 10 g of Zn(NO3)2·6H2O, 10 g of Cr(NO3)3·9H2O, add a certain amount of water, stir and mix to dissolve them completely to obtain a mixed metal salt solution;

[0035] Then add the mixed metal salt solution and the sodium carbonate aqueous solution to the carrier solution simultaneously and mix well, and the suspension turns dark green;

[0036] S2. Adjust the pH value of the suspension to 14 with 1 mol / L sodium hydroxide solution, stir for 14 h at a constant temperature of 70 °C. The solution changes from dark green suspension to coffee color. After standing overnight, centrifuge and dry, and finally calcine at 500 °C for 12 h. After the calcination, use hydrogen as a reducing agent for the reduction reaction, control the reduction temperature at 500 °C, and obtain the target catalyst after reacting for 5 h.

[0037] Example 3

[0038] The preparation steps in this example are the same as those in Example 1, except that the β-zeolite in step S1 is replaced with a mixture of silica and Al-SBA-15.

[0039] Example 4

[0040] The preparation steps in this example are the same as those in Example 2, except that the ZSM-5 zeolite in step S1 is replaced with alumina.

[0041] Comparative Example 1

[0042] The preparation steps in this comparative example are the same as those in Example 1, except that the mass ratio of the carrier to sodium carbonate in Example 1 is modified to 3:1.

[0043] Comparative Example 2

[0044] The preparation steps in this comparative example are the same as those in Example 1, except that the mass ratio of the carrier to sodium carbonate in Example 1 is modified to 1:4.

[0045] Comparative Example 3

[0046] The preparation steps in this comparative example are the same as those in Example 1, except that the precipitating agent in Example 1 is modified to ammonia water and ammonium bicarbonate. The specific steps are as follows:

[0047] S1. Add 74 g of β-zeolite and a certain amount of deionized water to a flask to completely dissolve it, and place it in the flask to obtain a carrier solution; then take 120.7 g of (NH4)2CO3 and prepare a 5 mol / L aqueous solution, add it to the carrier solution and mix well to obtain a mixed solution;

[0048] Take 0.028 g of PdCl2, 50 g of Ni(NO3)2·6H2O, 30 g of Co(NO3)2·6H2O, 10 g of Fe(NO3)2·9H2O, 10 g of (NH4)6Mo7O 24 ·4H2O, 10 g of Mn(NO3)2·4H2O, 10 g of Zn(NO3)2·6H2O, 10 g of Cr(NO3)3·9H2O and add a certain amount of water and stir to mix until completely dissolved to obtain a mixed metal salt solution;

[0049] Drop the mixed metal salt solution into the mixed solution, and the solution turns from a white suspension to dark green.

[0050] S2. Adjust the pH value of the suspension to 14 with 1 mol / L ammonia water, stir for 14 h under the condition of constant temperature at 70 °C. The solution turns from a dark green suspension to coffee color. After standing, it is found that the solution shows a layering phenomenon, that is, the upper layer is blue and the lower layer is coffee color. After centrifuging and drying overnight, finally, it is calcined at 650 °C for 8 h. After the calcination is completed, hydrogen is used as a reducing agent for the reduction reaction. The reduction temperature is controlled at 600 °C, and the target catalyst is obtained after reacting for 6 h.

[0051] Test the catalysts obtained in the above Examples 1-4 and Comparative Examples in a fixed bed. The specific test method is as follows:

[0052] Using dissolved DMT as the raw material for feeding, the catalyst dosage is 5-25% of the raw material dosage, the reaction temperature is 200-230 °C, the pressure is 0.1-1 MPa, the liquid-phase feeding flow rate is 0.1-0.15 ml / min, and the hydrogen flow rate is 0.1-8 ml / min. The products are detected respectively, and the results are shown in Table 1 below:

[0053] Table 1 Product detection results

[0054]

[0055]

[0056] The results show that when the mass ratio of the carrier to sodium carbonate is maintained within the range defined in the present invention, the conversion rate of DMT and the selectivity of DMCD are both optimal. In Comparative Example 1, the mass ratio of the carrier to sodium carbonate was modified to 3:1, and in Comparative Example 4, the mass ratio of the carrier to sodium carbonate was modified to 1:4, and the conversion rate of DMT decreased significantly.

[0057] In Comparative Example 3, the precipitating agent was modified to ammonia water and ammonium bicarbonate, and the conversion rate of DMT decreased significantly, indicating that the precipitating agent selected in the present invention has the best effect.

[0058] Recover the β-zeolite-supported nickel-based metal catalyst used in the fixed bed test in Example 1, wash it with water, wash it with ethanol and then dry it, and use it again in the fixed bed for the hydrogenation of DMT to prepare DMCD. After repeating the experiment many times, it is found that the conversion rate of DMT can be maintained at about 97.1%, indicating that it can be reused.

[0059] Therefore, the present invention relates to a method for preparing a catalyst for the hydrogenation of dimethyl terephthalate, which has a simple process flow. The prepared catalyst has high catalytic activity, good stability and a long service life. Its DMT hydrogenation conversion rate is high, and it can be repeatedly recovered and utilized after solvent cleaning or subsequent activation treatment, further reducing the catalyst preparation cost and production cost, and having high economic benefits and industrial application prospects.

[0060] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention and are not intended to limit them. Although the present invention has been described in detail with reference to the preferred embodiments, those of ordinary skill in the art should understand that they can still modify or equivalently replace the technical solutions of the present invention, and these modifications or equivalent replacements cannot make the modified technical solutions deviate from the spirit and scope of the technical solutions of the present invention.

Claims

1. A preparation method of a dimethyl terephthalate hydrogenation catalyst, characterized in that, It includes the following steps: S1. Using a carbonate solution, a carrier solution, and an active metal salt solution as raw materials, after mixing and reacting, a dark green suspension is obtained; S2. Adding an alkali solution to adjust the pH to alkaline, the color of the suspension changes from dark green to coffee color, after standing, centrifuging and drying, and after calcination and reduction reaction, a catalyst is obtained.

2. The preparation method of a dimethyl terephthalate hydrogenation catalyst according to claim 1, characterized in that: The specific steps of S1 are: adding the carbonate solution to the carrier solution and mixing evenly to obtain a mixed solution, and dropping the active metal salt solution into the mixed solution for reaction, so that the color of the suspension changes from white to dark green; Or adding the carbonate solution and the active metal salt solution together to the carrier solution and mixing evenly, so that the color of the suspension changes from white to dark green.

3. The preparation method of a dimethyl terephthalate hydrogenation catalyst according to claim 1, characterized in that: In S1, the carbonate is sodium carbonate; the carrier is one or more of β-zeolite, USY zeolite, Al-SBA-15, ZSM-5, silica, and alumina.

4. The preparation method of a dimethyl terephthalate hydrogenation catalyst according to claim 1, characterized in that: In S1, the active metal salt is a mixture of palladium salt, nickel salt, cobalt salt, molybdenum salt, iron salt, manganese salt, chromium salt, and zinc salt.

5. The preparation method of a dimethyl terephthalate hydrogenation catalyst according to claim 1, characterized in that: In S1, the mass ratio of the carrier to the carbonate is 1-6:

3.

6. The preparation method of a dimethyl terephthalate hydrogenation catalyst according to claim 3, characterized in that: In S2, the concentration of the alkali solution is 0.1-3 mol / L, and the alkali solution is sodium hydroxide.

7. The preparation method of a dimethyl terephthalate hydrogenation catalyst according to claim 1, characterized in that: In S2, the temperature during the pH adjustment process is 30-100 °C, the calcination temperature is 400-800 °C, and the calcination time is 2-10 h; the reduction temperature is 300-600 °C, and the reduction time is 2-6 h.

8. A dimethyl terephthalate hydrogenation catalyst, characterized in that: Prepared by the preparation method according to any one of the above claims 1-7.

9. A dimethyl terephthalate hydrogenation catalyst according to claim 8, characterized in that: Applying the prepared catalyst to the hydrogenation of dimethyl terephthalate to prepare dimethyl 1,4-cyclohexanedicarboxylate.

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