Preparation and application of dimethyl oxalate high-selectivity hydrogenation catalyst

Abstract

The invention provides preparation and application of a dimethyl oxalate high-selectivity hydrogenation catalyst. Black phosphorus is synchronously introduced in the ammonia distillation process of the catalyst, after hydrothermal aging, the black phosphorus and the catalyst are roasted and molded together, and finally the dimethyl oxalate high-selectivity hydrogenation catalyst is prepared. The prepared catalyst is used for a dimethyl oxalate hydrogenation reaction, black phosphorus is introduced in the process of forming a catalyst precursor by ammonia distillation, black phosphorus is promoted to be dispersed more uniformly in the catalyst and bonded with active metal more firmly, and black phosphorus lone pair electrons are utilized to regulate the electronic structure of the active metal to promote the hydrogenation activity and the selectivity of a target product to be improved; the reaction temperature and pressure are effectively reduced, the black phosphorus two-dimensional fold structure and the formed Si-O-P-M bond are utilized to promote dispersion of metal atoms, the interaction with the carrier is enhanced, the stability of the catalyst is further improved, and the service life of the catalyst is further prolonged. The adopted modification method is simple in process, convenient to operate and easy to industrialize, meanwhile, the service life of the catalyst can be effectively prolonged, and efficient utilization of the metal catalyst is promoted.

Description

Technical Field

[0001] The invention relates to the technical field of catalytic material preparation, and in particular to the preparation and application of a highly selective dimethyl oxalate hydrogenation catalyst. Background Art

[0002] Due to the characteristics of my country's energy structure of "poor oil, little gas, and relatively abundant coal", the development of coal-based chemicals is of great significance to industrial stability and even national security. The hydrogenation reaction of dimethyl oxalate (DMO) is an important part of coal chemical industry. As a typical series reaction, by using catalysts with different active components, methyl glycolate (MG), ethylene glycol (EG), ethanol and other products can be obtained respectively. Among them, MG, as a high-value-added organic chemical intermediate, is an excellent solvent for many celluloses, resins, and rubbers, and is widely used in industries such as chemicals, medicines, pesticides, feeds, spices and dyes; EG, as an important bulk chemical raw material, is widely used in chemical industries such as polyester, refrigerants, and plastics.

[0003] Silver is considered to be the best active center for DMO hydrogenation to produce MG due to its low hydrogenolysis activity; copper is considered to be the best active site for DMO hydrogenation to produce EG due to its high activity in ester hydrogenation and low activity in CC bond cleavage. Therefore, Ag / SiO2 is often used as a catalyst for DMO hydrogenation to produce MG, and Cu / SiO2 is often used as a catalyst for DMO hydrogenation to produce EG in industry, but both have disadvantages such as low yield of target product, high reaction temperature, and short life. CN202310464639.4 discloses a method for loading a silver-based catalyst on dendritic mesoporous silica microspheres and the application of the catalyst for hydrogenation of dimethyl oxalate; CN202010689903.0 discloses a method for preparing a supported catalyst for catalytic hydrogenation of dimethyl oxalate, which can realize low-temperature, low-pressure and efficient hydrogenation of dimethyl oxalate without reducing the conversion rate of dimethyl oxalate and the selectivity of the product; CN202211006090.6 discloses a multi-component hydrogenation catalyst for synthesizing methyl glycolate and a preparation method thereof, which adopts an ammonia-induced treatment method to perform secondary treatment on low-content metal components and non-metallic auxiliary components in the catalyst, and assists the non-metallic auxiliary components in being dispersed on the surface of the carrier; CN202211606617.9 discloses a copper-based catalyst for catalytic hydrogenation of dimethyl oxalate and its preparation method and application, which can realize the release of part of Cu in the hydrogen pre-reduction process. + The active sites ensure that the catalyst can be activated quickly and continuously release Cu during the reaction. + active sites, thereby improving the catalytic performance.

[0004] Black phosphorus (BP) is a direct band gap two-dimensional material with a natural wrinkled structure. It has been favored by researchers since 2014 because it has many excellent properties that traditional two-dimensional materials do not have. In the field of catalysis, black phosphorus is used as a carrier or auxiliary agent in the direction of heterogeneous catalysis because of its numerous active sites and lone pairs of electrons, thereby improving the catalytic performance of the catalyst. CN202111469716.2 published a method for preparing a black phosphorus / palladium catalyst for anthraquinone hydrogenation to produce hydrogen peroxide; CN201710182141.3 published a method for preparing a composite material of black phosphorus nanosheets and precious metal nanoparticles; CN202211131270.7 published a black phosphorus modified copper-based catalyst and its new use in organic hydrogenation reduction reactions. Summary of the invention

[0005] The present invention provides the preparation and application of a highly selective dimethyl oxalate hydrogenation catalyst. Black phosphorus is simultaneously introduced during the catalyst preparation process, thereby effectively improving the catalytic performance of the catalyst, improving the selectivity of the target product, and improving the life of the catalyst, thereby effectively reducing the process cost.

[0006] The technical solution adopted by the present invention is as follows: (1) dissolving a metal M salt solution in deionized water to obtain a solution A; (2) adding ammonia water to solution A to adjust the pH to 11-12, heating and stirring to react to form a complex solution, slowly dropping silica sol therein, and obtaining solution B after the dropping is completed; (3) heating B to evaporate ammonia, and adding black phosphorus dispersion thereto during the ammonia evaporation process; (4) subjecting the precursor to aging treatment after the ammonia evaporation is completed; (5) The aged solid is washed, filtered, dried and then calcined to obtain a highly selective hydrogenation catalyst for dimethyl oxalate, BP-M / SiO2.

[0007] 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.

[0008] In some preferred embodiments, the heating conditions in step (2) are a temperature of 50-70° C. and a time of 30-50 min; the dropping time is 30-60 min; and the mass ratio of the metal in solution B to the mass ratio of the silicon dioxide added to the silica gel is 1:3-1:19.

[0009] In some preferred embodiments, the black phosphorus dispersion in step (3) is prepared by dispersing black phosphorus micropowder in water by ultrasonication; the heating and ammonia evaporation conditions are 80-90° C., the pH of the solution is 6-7 at the end of ammonia evaporation, and the mass ratio of black phosphorus to metal is 1:5-1:50.

[0010] In some preferred embodiments, the black phosphorus dispersion in step (3) further contains a surfactant, wherein the surfactant includes at least one of a nonionic surfactant, an anionic surfactant or a cationic surfactant.

[0011] In some preferred embodiments, the concentration of the black phosphorus dispersion in step (3) is 0.5-5 mg / mL; and the adding method is to slowly dropwise add the black phosphorus dispersion at a uniform rate during the ammonia evaporation process until the ammonia evaporation process is completed.

[0012] In some preferred embodiments, the aging conditions in step (4) are aging in a hydrothermal autoclave, the aging temperature is 80-120° C., the aging time is 18-30 h, and the heating method is either a forced air drying oven or a vacuum drying oven.

[0013] In some preferred embodiments, the drying in step (5) is carried out by either forced air drying or vacuum drying, the drying temperature is 110-150°C, and the drying time is 10-14h; the roasting method is a roasting method in air or oxygen atmosphere, the roasting temperature is 350-450°C, and the roasting time is 4-6h.

[0014] The present invention provides a method for preparing the catalyst described in the above technical solution and application of the catalyst in the hydrogenation reaction of dimethyl oxalate (DMO).

[0015] The present invention has the following beneficial effects: (1) The present invention uses black phosphorus as a dopant, and the lone pair of black phosphorus electrons spontaneously bonds with the d orbitals of active metal atoms, thereby adjusting the electronic structure of metal atoms and optimizing intrinsic adsorption; effectively adjusting the activation ability of silver atoms to hydrogen and carbonyl groups, improving catalytic activity, and promoting MG desorption; by improving the copper-silicon catalyst Cu + ratio, thereby improving the catalytic activity and EG selectivity; (2) Due to the weak interaction between the active metal and the silica carrier, the metal particles are easily aggregated on the carrier surface. By adding black phosphorus during the ammonia evaporation process, the metal is uniformly bonded with the black phosphorus during precipitation. The wrinkled structure of the black phosphorus can inhibit the accumulation of active metals and delay the growth of metal crystallites during calcination and reduction. At the same time, after calcination, Si-OPM bonds are uniformly formed to promote the dispersion of active metals on the carrier, enhance the interaction between metal particles and the carrier, and further improve the life of the catalyst. (3) Enhance the bonding strength between black phosphorus and metal particles by hydrothermal aging, while exposing more active species; (4) The catalyst preparation process provided by the present invention is simple and efficient, and the raw materials used are green and pollution-free, which is convenient for industrial production. BRIEF DESCRIPTION OF THE DRAWINGS

[0016] Figure 1 Comparison of XPS spectra of Cu / SiO2 sample and BP-Cu / SiO2-1 sample. DETAILED DESCRIPTION

[0017] The invention provides the preparation and application of a highly selective hydrogenation catalyst for dimethyl oxalate. Black phosphorus is introduced synchronously during the ammonia evaporation process of the catalyst, and the electronic structure of metal atoms is adjusted after uniform bonding with metals by utilizing the spontaneous bonding property of black phosphorus, thereby promoting the improvement of catalyst activity and target product selectivity. Meanwhile, the wrinkled structure of the black phosphorus is utilized to promote uniform dispersion of metal atoms on a carrier, and aggregation of active metal atoms is avoided after calcination to form Si-OPM bonds, thereby improving catalyst stability and lifespan. The application is to apply the prepared catalyst to the hydrogenation reaction of dimethyl oxalate.

[0018] In order to make the purpose, technical solution and advantages of the present invention more clearly understood, the present invention is described in detail below in conjunction with the accompanying drawings and examples. It should be pointed out that the specific examples described herein are only used to explain the present invention and are not intended to limit the embodiments of the present invention. Any other changes, modifications, combinations, simplifications and substitutions made without departing from the spirit and principle of the present invention shall be equivalent replacement methods and shall be included in the protection scope of the present invention.

[0019] Catalyst performance test: The calcined catalyst powder is tableted, crushed, sieved, and 20-40 mesh catalyst particles are screened. 1g of catalyst particles are placed in a fixed bed reaction tube, and quartz sand is filled on the upper and lower layers of the catalyst bed. First, the catalyst is reduced online with hydrogen, at a reduction temperature of 300°C, a reduction pressure of 0.2MPa, a reduction time of 4h, and a hydrogen flow rate of 200mL / min; after the reduction is completed, the reaction pressure is increased to 1.5MPa, and when the reaction temperature is reduced to 175°C, a 15wt% DMO methanol solution is pumped into the reaction device with a high-pressure steady flow pump, and the liquid hourly space velocity is 4.5h -1 , hydrogen-ester ratio 80, after the reaction stabilizes, intermittent sampling and analysis by gas chromatography, at least three samples are taken for each reaction condition until the value stabilizes.

[0020] Comparative Example 1 1.7 g of silver nitrate solid was weighed and 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 a silver-ammine complex, 32.4 g of 30% silica sol was added dropwise according to the ratio of metallic silver mass to silica mass of 1:9, and the addition time was 40 min; after the addition was completed, ammonia was evaporated at 85 ° C until the pH was 6-7, and then stirred and aged at 80 ° C in the dark for 5 h, then filtered, washed, and placed in a blast drying oven at 120 ° C for 12 h, and finally the obtained solid was placed in a muffle furnace and calcined at 400 ° C for 4 h to obtain the catalyst Ag / SiO 2。 Comparative Example 2 1.88 g of copper nitrate solid was weighed and dissolved in deionized water, 3.5 mL of 25% ammonia solution was slowly added, heated to 60 ° C and stirred for 40 min to form a copper ammonia solution, 6.4 g of 30% silica sol was added dropwise according to the ratio of metal mass to silica mass of 1:3, and the addition time was 40 min; after the addition was completed, ammonia was evaporated at 90 ° C until the pH was 6-7, and then stirred and aged at 80 ° C for 5 h, then filtered, washed, and placed in a blast drying oven at 120 ° C for 12 h, and finally the obtained solid was placed in a muffle furnace and calcined at 400 ° C for 4 h to obtain the catalyst Cu / SiO 2。

[0021] Comparative Example 3 First, 1.88 g of copper nitrate solid was weighed and dissolved in deionized water, and 3.5 mL of 25% ammonia solution was slowly added. The mixture was heated to 50°C and stirred for 50 min to form a copper-ammonia complex. 6.4 g of 30% silica sol was added dropwise according to the ratio of metal copper to silicon dioxide of 1:3 for 30 min. After the addition was completed, ammonia was evaporated at 80°C. After the ammonia was evaporated, 25.6 mL of black phosphorus dispersion with a concentration of 0.5 mg / mL was added according to the mass ratio of black phosphorus to metal copper of 1:50. Polyethylene glycol was added to the dispersion to promote dispersion. The mixture was then placed in a 100 mL hydrothermal autoclave and aged at 80°C for 30 h. After aging, it was filtered and washed, and then placed in a forced air drying oven 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 the DMO hydrogenation reaction.

[0022] Comparative Example 4 First, 1.7 g of silver nitrate solid was weighed and dissolved in deionized water, and 5.5 mL of 10% ammonia solution was slowly added. The mixture was heated to 60°C and stirred for 40 min to form a silver-ammine complex. 32.4 g of 30% silica sol was added dropwise according to the ratio of metallic silver to silica mass of 1:9, and the addition time was 40 min. After the addition was completed, 24 mL of black phosphorus dispersion with a concentration of 3 mg / mL was added according to the mass ratio of black phosphorus to metallic silver of 1:15. Polyethylene glycol was added to the dispersion to promote dispersion, and then ammonia was evaporated at 85°C. The mixture was then placed in a 100 mL hydrothermal autoclave and aged in the dark at 100°C for 24 h. After aging, it was filtered and washed, and then placed in a forced air drying oven for drying 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, and the obtained catalyst was used in the DMO hydrogenation reaction.

[0023] Example 1 First, 1.88 g of copper nitrate solid was weighed and dissolved in deionized water, and 3.5 mL of 25% ammonia solution was slowly added. The mixture was heated to 50°C and stirred for 50 min to form a copper-ammonia complex. 6.4 g of 30% silica sol was added dropwise according to the ratio of metal copper to silicon dioxide of 1:3 for 30 min. After the addition was completed, ammonia was evaporated at 80°C. During the ammonia evaporation process, 25.6 mL of black phosphorus dispersion with a concentration of 0.5 mg / mL was added dropwise according to the mass ratio of black phosphorus to metal copper of 1:50. Polyethylene glycol was added to the dispersion to promote dispersion. The mixture was then placed in a 100 mL hydrothermal autoclave and aged at 80°C for 30 h. After aging, it was filtered and washed, and then placed in a forced air drying oven 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 the DMO hydrogenation reaction.

[0024] Example 2 First, 1.88 g of copper nitrate solid was weighed and dissolved in deionized water, and 3.5 mL of 25% ammonia solution was slowly added. The mixture was heated to 60°C and stirred for 40 min to form a copper-ammonia complex. 8.53 g of 30% silica sol was added dropwise according to the ratio of metal copper to silicon dioxide of 1:4 for 40 min. After the addition was completed, ammonia was evaporated at 85°C. During the ammonia evaporation process, 25.6 mL of black phosphorus dispersion with a concentration of 1 mg / mL was added dropwise according to the mass ratio of black phosphorus to metal copper of 1:25. Polyethylene glycol was added to the dispersion to promote dispersion. The mixture was then placed in a 100 mL hydrothermal autoclave and aged at 100°C for 24 h. After aging, it was filtered and washed, and then placed in a forced air drying oven for drying 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.

[0025] Example 3 First, 1.7 g of silver nitrate solid was weighed and dissolved in deionized water, and 5.5 mL of 10% ammonia solution was slowly added. The mixture was heated to 60°C and stirred for 40 min to form a silver-ammine complex. 32.4 g of 30% silica sol was added dropwise according to the ratio of metallic silver to silica mass of 1:9, and the addition time was 40 min. After the addition was completed, ammonia was evaporated at 85°C. During the ammonia evaporation process, 24 mL of black phosphorus dispersion with a concentration of 3 mg / mL was added dropwise according to the mass ratio of black phosphorus to metallic silver of 1:15. Polyethylene glycol was added to the dispersion to promote dispersion. The mixture was then placed in a 100 mL hydrothermal autoclave and aged in the dark at 100°C for 24 h. After aging, it was filtered and washed, and then placed in a forced air drying oven for drying 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, and the obtained catalyst was used in the DMO hydrogenation reaction.

[0026] Example 4 First, 1.7 g of silver nitrate solid was weighed and dissolved in deionized water, and 5.5 mL of 10% ammonia solution was slowly added. The mixture was heated to 70°C and stirred for 30 min to form a silver-ammine complex. 68.4 g of 30% silica sol was added dropwise according to the ratio of metallic silver to silica mass of 1:19, and the addition time was 60 min. After the addition was completed, ammonia was evaporated at 90°C. During the ammonia evaporation process, 43.2 mL of black phosphorus dispersion with a concentration of 5 mg / mL was added dropwise according to the mass ratio of black phosphorus to metallic silver of 1:5. Polyethylene glycol was added to the dispersion to promote dispersion. The mixture was then placed in a 100 mL hydrothermal autoclave and aged in the dark at 120°C for 18 h. After aging, it was filtered and washed, and then placed in a forced air drying oven for drying 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 obtained catalyst was used in the DMO hydrogenation reaction.

[0027] Table 1 Performance test results of catalyst samples of comparative examples and examples Sample name Reaction temperature / ℃ DMO conversion rate % 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 Note: DMO stands for dimethyl oxalate, MG stands for methyl glycolate, MF stands for methyl formate, and EG stands for ethylene glycol.

[0028] From the results in Table 1 and Figure 1It can be seen from the XPS results that the dimethyl oxalate hydrogenation catalyst prepared by the present invention has the characteristics of high low-temperature activity and good selectivity for the target product; by synchronously adding black phosphorus during the ammonia evaporation process to adjust the electronic structure of the active metal, the increase of active species is promoted, and the number of active sites is increased, thereby achieving the purpose of higher activity and higher selectivity, so that the sample with lower active metal content has higher activity and selectivity than the comparative example; for the BP-Cu / SiO2 sample, the use of black phosphorus effectively increases the Cu content in the active copper species of the catalyst. + ratio to achieve higher EG selectivity; for the BP-Ag / SiO2 sample, black phosphorus was used to adjust the dehydrogenation activity of Ag atoms and optimize the adsorption capacity of the catalyst for MG, thereby achieving higher conversion rate and selectivity at low temperature.

Claims

1. A method for preparing a highly selective dimethyl oxalate hydrogenation catalyst, characterized in that: The preparation method comprises the following steps: (1) dissolving a metal M salt solution in deionized water to obtain a solution A; (2) adding ammonia water to solution A to adjust the pH to 11-12, heating and stirring to react to form a complex solution, slowly dropping silica sol therein, and obtaining solution B after the dropping is completed; (3) heating B to evaporate ammonia, and adding black phosphorus dispersion thereto during the ammonia evaporation process; (4) subjecting the precursor to aging treatment after the ammonia evaporation is completed; (5) The aged solid is washed, filtered, dried and then calcined to obtain a highly selective hydrogenation catalyst for dimethyl oxalate, BP-M / SiO2.

2. The preparation method according to claim 1, characterized in that: 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.

3. The preparation method according to claim 1, characterized in that The heating conditions in step (2) are a temperature of 50-70° C. and a time of 30-50 min; the dropping time is 30-60 min; and the mass ratio of the metal in solution B to the mass ratio of the silicon dioxide added to the silica gel is 1:3-1:

19.

4. The preparation method according to claim 1, characterized in that: The black phosphorus dispersion in step (3) is prepared by dispersing black phosphorus micropowder in water by ultrasonic method; the heating and ammonia evaporation conditions are 80-90° C., the pH value of the solution is 6-7 when the ammonia evaporation is completed, and the mass ratio of black phosphorus to metal is 1:5-1:

50.

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

6. The preparation method according to claim 1, characterized in that: The concentration of the black phosphorus dispersion in step (3) is 0.5-5 mg / mL; the adding method is to slowly dropwise add the dispersion at a uniform speed during the ammonia evaporation process until the ammonia evaporation process is completed.

7. The preparation method according to claim 1, characterized in that: The aging conditions in step (4) are aging in a hydrothermal autoclave, the aging temperature is 80-120° C., the aging time is 18-30 h, and the heating method is either a forced air drying oven or a vacuum drying oven.

8. The preparation method according to claim 1, characterized in that: The drying in step (5) is carried out by either forced air drying or vacuum drying, the drying temperature is 110-150°C, and the drying time is 10-14h; the roasting method is a roasting method in air or oxygen atmosphere, the roasting temperature is 350-450°C, and the roasting time is 4-6h.

9. A black phosphorus modified catalyst BP-M / SiO2 prepared by the method according to any one of claims 1 to 8.

10. Use of the catalyst according to claims 1-9 in the hydrogenation reaction of dimethyl oxalate (DMO).

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