Preparation and application of high-selectivity hydrogenation catalyst for dimethyl oxalate

Abstract

The application provides a preparation and application of a high-selectivity dimethyl oxalate hydrogenation catalyst. Black phosphorus is introduced synchronously in the ammonia evaporation process of the catalyst, and is calcined into the high-selectivity dimethyl oxalate hydrogenation catalyst after hydrothermal aging. The prepared catalyst is used in the dimethyl oxalate hydrogenation reaction, black phosphorus is introduced before the catalyst precursor is formed in the ammonia evaporation process, the black phosphorus is more uniformly dispersed in the catalyst, and the black phosphorus is more firmly bonded with the active metal, the electron structure of the active metal is regulated by using the lone pair electrons of the black phosphorus to promote the hydrogenation activity and the selectivity of the target product, the reaction temperature and pressure are effectively reduced, the metal atom dispersion is promoted by using the two-dimensional wrinkle structure of the black phosphorus and the Si-O-P-M bond formed, the interaction with the carrier is enhanced, and the stability and service life of the catalyst are further improved. The modification method adopted in the application is simple in process, convenient to operate and easy to industrialize, and can effectively improve the service life of the catalyst and promote the efficient use of the metal catalyst.

Description

TECHNICAL FIELD

[0001] The application relates to the technical field of preparation of a catalytic material, in particular to preparation and application of a dimethyl oxalate high-selectivity hydrogenation catalyst. BACKGROUND

[0002] The dimethyl oxalate (DMO) hydrogenation reaction is an important link in coal chemical industry. As a typical consecutive reaction, different active components of catalysts can be used to obtain methyl glycolate (MG), ethylene glycol (EG) and ethanol products. MG, as a high-value organic chemical intermediate, is a good solvent for many cellulose, resin and rubber, and is widely used in chemical, pharmaceutical, pesticide, feed, perfume and dye industries. EG, as an important bulk chemical raw material, is widely used in polyester, refrigerant, plastic and other chemical industries.

[0003] Metallic silver is considered to be the best active center for preparing MG from DMO hydrogenation due to its low hydrogenolysis activity. Metallic copper is considered to be the best active site for preparing EG from DMO hydrogenation due to its high activity in ester hydrogenation and low activity in C-C bond breaking. Therefore, Ag / SiO2 is commonly used as a catalyst for preparing MG from DMO hydrogenation in industry, and Cu / SiO2 is commonly used as a catalyst for preparing EG from DMO hydrogenation. However, both of them have the disadvantages of low target product yield, high reaction temperature, short service life and the like. CN202310464639.4 discloses a method for preparing a dendritic mesoporous silica microsphere supported silver-based catalyst and application of the catalyst in dimethyl oxalate hydrogenation. CN202010689903.0 discloses a preparation method of a supported catalyst for catalyzing dimethyl oxalate hydrogenation, which can realize low-temperature, low-pressure and high-efficiency hydrogenation of dimethyl oxalate without reducing the conversion rate of dimethyl oxalate and the selectivity of products. CN202211006090.6 discloses a multi-component hydrogenation catalyst for synthesizing methyl glycolate and a preparation method thereof. The catalyst is treated with ammonia gas induction, and the low-content metal component and non-metallic additive component in the catalyst are treated again to assist the positioning and dispersion of the non-metallic additive component on the surface of the carrier. CN202211606617.9 discloses a copper-based catalyst for catalyzing dimethyl oxalate hydrogenation and a preparation method and application thereof. The catalyst can realize the release of part of Cu + active sites to ensure that the catalyst can be quickly activated, and continuously release Cu + active sites during the reaction process, thereby improving the catalytic performance.

[0004] Black phosphorus (BP) is a direct band gap two-dimensional material with a natural corrugated structure. Since 2014, it has been favored by researchers because of its many excellent characteristics that traditional two-dimensional materials do not possess. In the field of catalysis, black phosphorus is used as a carrier or additive in heterogeneous catalysis due to its numerous active sites and lone pair electrons, thereby improving the catalytic performance of the catalyst. CN202111469716.2 discloses a preparation method of a black phosphorus / palladium catalyst for the production of hydrogen peroxide by the hydrogenation of anthraquinone; CN201710182141.3 discloses a preparation method of a black phosphorus nanosheet and noble metal nanoparticle composite material; and CN202211131270.7 discloses a black phosphorus modified copper-based catalyst and its new use in the hydrogenation reduction reaction of organic matter. SUMMARY

[0005] The present application provides a preparation and application of a high-selectivity dimethyl oxalate hydrogenation catalyst. By synchronously introducing black phosphorus during the preparation of the catalyst, the catalytic performance of the catalyst is effectively improved, the selectivity of the target product is improved, and the service life of the catalyst is improved, thereby effectively reducing the process cost.

[0006] The technical solutions adopted by the present application are as follows:

[0007] (1) Dissolve a metal M salt solution in deionized water to obtain solution A;

[0008] (2) Add ammonia water to solution A to adjust the pH to 11-12, heat and stir to form a complex solution, and slowly add silica sol to the complex solution. After the addition is completed, solution B is obtained;

[0009] (3) Perform ammonia evaporation treatment on B, and add black phosphorus dispersion liquid during the ammonia evaporation process;

[0010] (4) Perform aging treatment on the precursor after the ammonia evaporation is completed;

[0011] (5) After washing, filtering, and drying the aged solid, perform calcination to obtain a high-selectivity dimethyl oxalate hydrogenation catalyst BP-M / SiO2.

[0012] In some preferred embodiments, the metal M salt in step (1) includes any one or more of copper nitrate, copper sulfate, copper chloride, copper acetate, copper bromide, silver nitrate, silver acetate, silver acetylacetonate, and silver thiosulfate.

[0013] In some preferred embodiments, the heating condition in step (2) is a temperature of 50-70°C and a time of 30-50 min; the dropwise addition time is 30-60 min; and the mass ratio of the metal in solution B to the mass of silica in the added silica gel is 1:3-1:19.

[0014] In some preferred embodiments, the black phosphorus dispersion liquid in step (3) is prepared by ultrasonic dispersion of black phosphorus micro-powder in water; the ammonia evaporation conditions are 80-90 DEG C, the solution pH is 6-7 at the end of ammonia evaporation, and the mass ratio of black phosphorus to metal is 1:5-1:50.

[0015] In some preferred embodiments, the black phosphorus dispersion liquid in step (3) further contains a surfactant, and the surfactant comprises at least one of a non-ionic surfactant, an anionic surfactant or a cationic surfactant.

[0016] In some preferred embodiments, the concentration of the black phosphorus dispersion liquid in step (3) is 0.5-5 mg / mL; and the adding mode is slow and uniform dropping during the ammonia evaporation process until the end of the ammonia evaporation process.

[0017] In some preferred embodiments, the aging conditions in step (4) are aging in a hydrothermal kettle, the aging temperature is 80-120 DEG C, the aging time is 18-30 h, and the heating mode is any one of a blast drying oven or a vacuum drying oven.

[0018] In some preferred embodiments, the drying in step (5) adopts any one of blast drying or vacuum drying, the drying temperature is 110-150 DEG C, the drying time is 10-14 h, the calcination mode is calcination in an air or oxygen atmosphere, the calcination temperature is 350-450 DEG C, and the calcination time is 4-6 h.

[0019] The application provides a catalyst preparation method and application thereof in a dimethyl oxalate (DMO) hydrogenation reaction.

[0020] The application has the following beneficial effects:

[0021] (1) The application uses black phosphorus as a dopant, and the black phosphorus lone pair electrons spontaneously form bonds with the d orbitals of active metal atoms, thereby adjusting the electronic structure of the metal atoms and optimizing the intrinsic adsorption; the activation ability of silver atoms to hydrogen and carbonyl is effectively adjusted, the catalytic activity is improved, and the MG desorption is promoted; the Cu + ratio is improved, thereby improving the catalytic activity and EG selectivity;

[0022] (2) Since the interaction between the active metal and the silica carrier is weak, the metal particles are prone to agglomeration on the carrier surface; by adding black phosphorus during the ammonia evaporation process, the metal is bonded with the black phosphorus uniformly during precipitation, the accumulation of active metal is inhibited by using the wrinkle structure, the growth of metal microcrystals during calcination and reduction is delayed, Si-O-P-M bonds are uniformly formed after calcination to promote the dispersion of active metal on the carrier, the interaction between the metal particles and the carrier is enhanced, and the service life of the catalyst is further improved.

[0023] (3) By means of hydrothermal aging, the bonding strength of black phosphorus and metal particles is enhanced, and more active species are exposed;

[0024] (4) The catalyst provided by the application has simple and efficient preparation process, green and non-polluted raw materials, and is convenient for industrial production. BRIEF DESCRIPTION OF DRAWINGS

[0025] Figure 1 XPS spectrum comparison of Cu / SiO2 sample and BP-Cu / SiO2-1 sample. DETAILED DESCRIPTION

[0026] The application provides a preparation and application of a dimethyl oxalate high-selectivity hydrogenation catalyst, black phosphorus is synchronously introduced in an ammonia evaporation process of the catalyst, electronic structures of metal atoms are adjusted by using the characteristics of spontaneous bonding of the black phosphorus and the metal after uniform bonding, catalyst activity and selectivity of a target product are promoted, the black phosphorus is used to promote uniform dispersion of metal atoms on a carrier, aggregation of active metal atoms is avoided after the Si-O-P-M bond is formed by calcination, and catalyst stability and service life are improved, and the application is that the prepared catalyst is applied to a dimethyl oxalate hydrogenation reaction.

[0027] In order to make the purpose, technical scheme and advantages of the application clearer and more apparent, the application is described in detail below with reference to the drawings and examples. It should be pointed out that the specific examples described herein are only used to explain the application, and are not intended to limit the implementation mode of the application. Any change, modification, combination, simplification or replacement made without departing from the spirit and principle of the application should be equivalent replacement mode, and should be included in the protection scope of the application.

[0028] Catalyst performance test: after the calcination is completed, the catalyst powder is tabletted, broken, sieved, and the catalyst particles with a size of 20-40 meshes are screened, 1g of the catalyst particles is placed in a fixed bed reaction tube, and quartz sand is filled above and below the catalyst bed. First, the catalyst is reduced online by using hydrogen, the reduction temperature is 300 DEG C, the reduction pressure is 0.2 MPa, the reduction time is 4h, and the hydrogen flow is 200mL / min; after the reduction is completed, the reaction pressure is increased to 1.5 MPa, and when the reaction control temperature is reduced to 175 DEG C, a 15wt% DMO methanol solution is injected into the reaction device by using a high-pressure constant-flow pump, the liquid hourly space velocity is 4.5h -1 , the hydrogen ester ratio is 80, and after the reaction is stable, intermittent sampling is performed and gas chromatography analysis is performed, at least three samples are taken under each reaction condition until the value is stable.

[0029] Comparative example 1

[0030] Take 1.7 g of silver nitrate solid dissolved in deionized water, slowly add 5.5 mL of 10% ammonia solution, heat to 60°C and stir for 40 min to form silver ammonia complex, according to the mass of silver and the mass of silicon dioxide 1:9, add 32.4 g of 30% silica sol, the dropwise adding time is 40 min; After the dropwise adding is completed, ammonia evaporation treatment is carried out, the ammonia evaporation condition is 85°C, and the treatment is ended until the pH is 6-7, after the ending, the mixture is stirred at 80°C under the light-proof condition for 5 h, then the mixture is filtered, washed and placed in a blast drying oven for drying at 120°C for 12 h, finally, the obtained solid is placed in a muffle furnace for calcination at 400°C for 4 h to obtain the catalyst Ag / SiO 2。 Comparative Example 2

[0031] Take 1.88 g of copper nitrate solid dissolved in deionized water, slowly add 3.5 mL of 25% ammonia solution, heat to 60°C and stir for 40 min to form copper ammonia solution, according to the mass of copper and the mass of silicon dioxide 1:3, add 6.4 g of 30% silica sol, the dropwise adding time is 40 min; After the dropwise adding is completed, ammonia evaporation treatment is carried out, the ammonia evaporation condition is 90°C, and the treatment is ended until the pH is 6-7, after the ending, the mixture is stirred at 80°C for 5 h, then the mixture is filtered, washed and placed in a blast drying oven for drying at 120°C for 12 h, finally, the obtained solid is placed in a muffle furnace for calcination at 400°C for 4 h to obtain the catalyst Cu / SiO 2。

[0032] Comparative Example 3

[0033] First, take 1.88 g of copper nitrate solid dissolved in deionized water, slowly add 3.5 mL of 25% ammonia solution, heat to 50°C and stir for 50 min to form copper ammonia complex, according to the mass of copper and the mass of silicon dioxide 1:3, add 6.4 g of 30% silica sol, the dropwise adding time is 30 min; After the dropwise adding is completed, ammonia evaporation treatment is carried out at 80°C, after the ammonia evaporation is ended, 25.6 mL of black phosphorus dispersion solution with a concentration of 0.5 mg / mL is added according to the mass ratio of black phosphorus to copper 1:50, polyethylene glycol is added in the dispersion solution to promote dispersion, then the mixture is placed in a 100 mL hydrothermal kettle for aging at 80°C for 30 h, after the aging is completed, the mixture is filtered, washed and placed in a blast drying oven for drying at 110°C for 14 h, finally, the obtained solid is placed in a muffle furnace for calcination at 350°C for 6 h to obtain the catalyst BP-Cu / SiO2-1, and the prepared catalyst is used in DMO hydrogenation reaction.

[0034] Comparative Example 4

[0035] Firstly, 1.7 g of silver nitrate solid was dissolved in deionized water, 5.5 mL of 10% ammonia solution was slowly added, heated to 60°C and stirred for 40 min to form silver ammonia complex, 30% silica sol 32.4 g was added according to the mass ratio of silver to silica 1:9, the dropwise adding time was 40 min; after the dropwise adding was completed, 24 mL of black phosphorus dispersion solution with a concentration of 3 mg / mL was added according to the mass ratio of black phosphorus to silver 1:15, polyethylene glycol was added in the dispersion solution to promote dispersion, then ammonia evaporation treatment was carried out at 85°C, then the mixture was placed in a 100 mL hydrothermal kettle and aged at 100°C in the dark for 24 h, after aging, filtration and washing, the mixture was placed in a blast drying oven and dried at 120°C for 12 h, finally the obtained solid was placed in a muffle furnace and calcined at 400°C for 5 h to obtain the catalyst BP-Ag / SiO2-1, which was used in DMO hydrogenation reaction.

[0036] Example 1

[0037] Firstly, 1.88 g of copper nitrate solid was dissolved in deionized water, 3.5 mL of 25% ammonia solution was slowly added, heated to 50°C and stirred for 50 min to form copper ammonia complex, 30% silica sol 6.4 g was added according to the mass ratio of copper to silica 1:3, the dropwise adding time was 30 min; after the dropwise adding was completed, ammonia evaporation treatment was carried out at 80°C, during the ammonia evaporation process, 25.6 mL of black phosphorus dispersion solution with a concentration of 0.5 mg / mL was added according to the mass ratio of black phosphorus to copper 1:50, polyethylene glycol was added in the dispersion solution to promote dispersion, then the mixture was placed in a 100 mL hydrothermal kettle and aged at 80°C for 30 h, after aging, filtration and washing, the mixture was placed in a blast drying oven and dried at 110°C for 14 h, finally the obtained solid was placed in a muffle furnace and calcined at 350°C for 6 h to obtain the catalyst BP-Cu / SiO2-1, which was used in DMO hydrogenation reaction.

[0038] Example 2

[0039] Firstly, 1.88 g of copper nitrate solid was dissolved in deionized water, 3.5 mL of ammonia solution with a concentration of 25% was slowly added, heated to 60°C and stirred for 40 min to form a copper ammonia complex, 8.53 g of 30% silica sol was added according to the mass ratio of copper to silica of 1:4, and the dropping time was 40 min; after the dropping was completed, ammonia evaporation treatment was carried out at 85°C, and 25.6 mL of black phosphorus dispersion solution with a concentration of 1 mg / mL was added according to the mass ratio of black phosphorus to copper of 1:25 during the ammonia evaporation process, polyethylene glycol was added in the dispersion solution to promote dispersion, then the mixture was placed in a 100 mL hydrothermal kettle and aged at 100°C for 24 h, after aging, filtration and washing, the mixture was placed in a blast drying oven and dried at 120°C for 12 h, finally the obtained solid was placed in a muffle furnace and calcined at 400°C for 5 h to obtain the catalyst BP-Cu / SiO2-2, which was used in the DMO hydrogenation reaction.

[0040] Example 3

[0041] Firstly, 1.88 g of copper nitrate solid was dissolved in deionized water, 3.5 mL of ammonia solution with a concentration of 25% was slowly added, heated to 60°C and stirred for 40 min to form a copper ammonia complex, 8.53 g of 30% silica sol was added according to the mass ratio of copper to silica of 1:4, and the dropping time was 40 min; after the dropping was completed, ammonia evaporation treatment was carried out at 85°C, and 25.6 mL of black phosphorus dispersion solution with a concentration of 1 mg / mL was added according to the mass ratio of black phosphorus to copper of 1:25 during the ammonia evaporation process, polyethylene glycol was added in the dispersion solution to promote dispersion, then the mixture was placed in a 100 mL hydrothermal kettle and aged at 100°C for 24 h, after aging, filtration and washing, the mixture was placed in a blast drying oven and dried at 120°C for 12 h, finally the obtained solid was placed in a muffle furnace and calcined at 400°C for 5 h to obtain the catalyst BP-Cu / SiO2-2, which was used in the DMO hydrogenation reaction.

[0042] Example 4

[0043] Firstly, 1.7 g of silver nitrate solid was dissolved in deionized water, 5.5 mL of 10% ammonia water solution was slowly added, heated to 70°C and stirred for 30 min to form silver ammonia complex, 68.4 g of 30% silica sol was added according to the mass ratio of silver to silica of 1:19, and the dropping time was 60 min; after the dropping was completed, ammonia evaporation treatment was carried out at 90°C, and during the ammonia evaporation process, 43.2 mL of black phosphorus dispersion solution with a concentration of 5 mg / mL was added according to the mass ratio of black phosphorus to silver of 1:5, polyethylene glycol was added in the dispersion solution to promote dispersion, then the mixture was placed in a 100 mL hydrothermal kettle and aged at 120°C in the dark for 18 h, after aging, filtration and washing, the mixture was placed in a blast drying oven and dried at 150°C for 10 h, finally the obtained solid was placed in a muffle furnace and calcined at 450°C for 4 h to obtain the catalyst BP-Ag / SiO2-2, and the prepared catalyst was used in DMO hydrogenation reaction.

[0044] Table 1. Performance test results of catalyst samples of the comparative examples and the examples

[0045] Sample name Reaction temperature / °C DMO conversion % MG selectivity % MF selectivity % EG selectivity % Example 1 170 100 0.02 0 99.1 Example 2 171 99.3 2.1 0 97.4 Example 3 168 100 99.2 0.05 0.02 Example 4 173 89.6 97.9 1.9 0.01 Comparative Example 1 175 70.3 81.3 17.9 0.8 Comparative Example 2 175 83.7 41.3 0 58.1 Comparative Example 3 172 98.9 2.41 0 96.3 Comparative Example 4 174 88.3 90.2 9.1 0.6

[0046] Note: DMO represents dimethyl oxalate, MG represents methyl glycolate, MF represents methyl formate, and EG represents ethylene glycol.

[0047] From the results in Table 1 and Figure 1 XPS results can be seen that the dimethyl oxalate hydrogenation catalyst prepared by the present application has the characteristics of low temperature activity and high selectivity of target product; by synchronously adding black phosphorus during ammonia evaporation process to adjust the electronic structure of active metal and promote the increase of active species, the number of active sites is increased, so as to achieve the purpose of higher activity and higher selectivity, so that the sample with lower active metal content in the comparative example has higher activity and selectivity; for the BP-Cu / SiO2 sample, the black phosphorus is used to effectively improve the Cu + content in the active copper species of the catalyst, so as to achieve higher EG selectivity; for the BP-Ag / SiO2 sample, the black phosphorus is used to adjust the dehydrogenation activity of Ag atoms and optimize the adsorption capacity of the catalyst for MG, so as to achieve higher conversion rate and selectivity at low temperature.

Claims

1. A method for preparing a high-selectivity catalyst for the hydrogenation of dimethyl oxalate, characterized in that: The preparation method comprises the following steps: (1) dissolving a metal M salt solution in deionized water to obtain solution A, wherein the metal M salt comprises any one or more of copper nitrate, copper sulfate, copper chloride, copper acetate, copper bromide, silver nitrate, silver acetate, silver acetylacetonate, and silver thiosulfate; (2) adding ammonia water to solution A to adjust the pH to 11-12, and heating and stirring to form a complex solution, and slowly adding silica sol into the complex solution, to obtain solution B after the addition is completed; (3) performing ammonia evaporation treatment on B, and adding a black phosphorus dispersion liquid into B during the ammonia evaporation process, wherein the black phosphorus dispersion liquid is prepared by dispersing black phosphorus powder in water through ultrasonic treatment; the ammonia evaporation treatment is performed at a temperature of 80-90 DEG C, and the pH of the solution is 6-7 when the ammonia evaporation process is completed; the black phosphorus dispersion liquid is slowly added at a constant speed during the ammonia evaporation process until the ammonia evaporation process is completed; (4) performing aging treatment on the precursor after the ammonia evaporation process is completed; (5) performing washing, filtering, drying, and calcination on the solid after the aging treatment, to obtain a dimethyl oxalate high-selectivity hydrogenation catalyst BP-M / SiO2.

2. The production method according to claim 1, characterized by, In step (2), the heating condition is a temperature of 50-70 DEG C and a time of 30-50 min; and the dropwise addition time is 30-60 min.

3. The preparation method according to claim 2, characterized in that In solution B, the mass ratio of the metal to the silica in the silica sol is 1:3-1:

19.

4. The method of claim 1, wherein, In step (3), the mass ratio of the added black phosphorus to the metal is 1:5-1:

50.

5. The preparation method according to claim 1, characterized in that In step (3), the black phosphorus dispersion liquid further comprises a surfactant, and the surfactant comprises at least one of a nonionic surfactant, an anionic surfactant, or a cationic surfactant.

6. The method of claim 1, wherein, In step (3), the concentration of the black phosphorus dispersion liquid is 0.5-5 mg / mL.

7. The preparation method according to claim 1, characterized in that In step (4), the aging condition is aging in a hydrothermal kettle, the aging temperature is 80-120 DEG C, the aging time is 18-30 h, and the heating mode is any one of a blast drying oven or a vacuum drying oven.

8. The method of claim 1, wherein, In step (5), the drying is performed by any one of blast drying or vacuum drying, the drying temperature is 110-150 DEG C, the drying time is 10-14 h, the calcination is performed in an air or oxygen atmosphere, the calcination temperature is 350-450 DEG C, and the calcination time is 4-6 h.

9. Application of a black phosphorus modified catalyst BP-M / SiO2 prepared by the method in any one of claims 1-8 to a dimethyl oxalate DMO hydrogenation reaction.

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