Composite metal oxide catalyst, its preparation method and application
The preparation method of the composite metal oxide catalyst AOxBOy/M solves the problem of low conversion rate and selectivity of existing catalysts in the process of carbon dioxide hydrogenation to formamide, and realizes efficient and stable formamide production, which is suitable for fixed bed continuous flow reactors.
Patent Information
- Authority / Receiving Office
- CN · China
- Patent Type
- Patents(China)
- Current Assignee / Owner
- LANZHOU UNIV
- Filing Date
- 2023-12-21
- Publication Date
- 2026-05-29
AI Technical Summary
Existing catalysts exhibit low conversion and selectivity, poor stability, and significant decrease in space-time yield after prolonged use at high temperatures. Furthermore, batch reactions are difficult to implement in actual production.
The preparation methods of composite metal oxide catalysts AOxBOy/M include co-precipitation, impregnation or deposition precipitation, for continuous flow reactions of amine compounds with carbon dioxide and hydrogen. The catalyst composition is a composite oxide of Zn, Cd or In with Zr, Ti or Fe, and the support is SiO2, activated carbon or diatomaceous earth. The reaction is carried out in a fixed-bed continuous flow reactor.
It improves the catalytic efficiency and selectivity of carbon dioxide hydrogenation to formamide. The catalyst has good stability, is easy to operate, does not require external solvents or additives, and the space-time yield hardly decreases after running at 300℃ for 1000h. The subsequent separation and purification process is simple.
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Figure CN117654472B_ABST
Abstract
Description
Technical Field
[0001] This invention relates to the field of catalyst technology, and in particular to a composite metal oxide catalyst, its preparation method, and its application. Background Technology
[0002] With the continuous development of human society, the exploitation and utilization of fossil fuels has increased daily, accompanied by a sharp decline in forest vegetation area. This has led to a year-on-year increase in atmospheric carbon dioxide concentration, causing a series of natural environmental and even social problems, including global warming, ocean acidification, and frequent extreme weather events. Therefore, reducing atmospheric carbon dioxide concentration has become an urgent problem to be solved. On the other hand, carbon dioxide is inexpensive, readily available, and abundant, and can replace toxic carbon monoxide as a novel C1 building block. By capturing and encapsulating carbon dioxide through a series of processes, and then reacting it with renewable green hydrogen through a series of catalytic reactions, it can be converted into high-value-added chemicals. This achieves a win-win result of turning waste into treasure, while simultaneously solving the carbon dioxide problem and realizing certain economic benefits.
[0003] Formamides, as important pharmaceutical and pesticide intermediates, can be prepared by the coupling reaction of carbon dioxide hydrogenation with amine compounds. N,N-dimethylformamide, in particular, is a commonly used building block and universal solvent in synthetic chemistry, enjoying a huge market demand. As early as 1970, it was reported that homogeneous noble metal organometallic complexes could catalyze the N-formylation of carbon dioxide to formamide products [US2013 / 0102807 A1]. However, the addition of a basic auxiliary agent was still required, and the reaction required extremely high pressure conditions, placing stringent demands on the equipment. Subsequently, Ru-type complex catalysts [CN1059852MA], alloy catalysts [CN 110833834A], and heterogeneous porous organic compound catalysts [CN111205198 A; WO 2021 / 147622A1] were successively developed, significantly improving catalytic performance and noticeably reducing the amount of noble metals used. Even so, current research on this reaction remains entirely at the stage of batch reactors, far removed from actual production conditions. Furthermore, product separation and catalyst recovery processes still involve numerous steps. Meanwhile, the feed conversion rate and selectivity for formamide in existing catalysts used in the hydrogenation of carbon dioxide need improvement, and the catalysts also suffer from limited lifespan, poor stability, and a significant decrease in space-time yield after prolonged use at high temperatures. Therefore, it is necessary to develop a new catalyst for the hydrogenation of carbon dioxide to formamide to overcome the problems existing in current catalysts. Summary of the Invention
[0004] To address the aforementioned problems, this invention provides a composite metal oxide catalyst that, under certain temperature and pressure conditions, enables the continuous flow reaction of amine compounds with carbon dioxide and hydrogen to prepare formamide compounds.
[0005] The composite metal oxide catalyst of the present invention has the composition AOxBOy / M;
[0006] Where A is Zn, Cd, or In; B is Zr, Ti, or Fe; and M is SiO2, activated carbon, or diatomaceous earth.
[0007] Furthermore, the molar ratio of A to B is (1-10):(1-10).
[0008] Furthermore, the M content is 0–90 wt%.
[0009] The present invention also provides a method for preparing the catalyst, namely, co-precipitation, impregnation or deposition precipitation.
[0010] Furthermore, the coprecipitation method includes the following steps:
[0011] S1. Dissolve the salts of A and B in water to prepare an aqueous solution of metal salts, and add the aqueous solution of metal salts dropwise into an aqueous solution of precipitant for co-precipitation;
[0012] S2. After drying the obtained precipitate, calcine it to obtain the composite metal oxide catalyst.
[0013] Furthermore, the concentration of the metal salt aqueous solution is 0.01–2 mol / L, and the concentration of the precipitant aqueous solution is 1–5 times the concentration of the metal salt aqueous solution.
[0014] Furthermore, the volume ratio of the metal salt aqueous solution to the precipitant aqueous solution is (1-500):(1-500).
[0015] Furthermore, the coprecipitation temperature is 30℃~90℃, and the coprecipitation pH is 6~12.
[0016] Furthermore, the drying temperature is 60℃~300℃, the drying time is 4~24h, the calcination temperature is 200℃~800℃, and the calcination time is 2~24h.
[0017] Furthermore, the coprecipitation method includes the following steps:
[0018] S1. Dissolve salts A and B in water to prepare an aqueous solution of metal salts. Dissolve the aqueous solution of metal salts in a precipitant solution and add it dropwise to perform co-precipitation.
[0019] S2. After drying the obtained precipitate, calcine it to obtain the composite metal oxide catalyst.
[0020] Furthermore, the concentration of the aqueous solution of the metal salt is 0.01–2 mol / L.
[0021] Furthermore, the volume ratio of the metal salt aqueous solution to the precipitant aqueous solution is (1-500):(1-500).
[0022] Furthermore, the coprecipitation temperature is 30℃~90℃, and the coprecipitation pH is 6~12.
[0023] Furthermore, the drying temperature is 60℃~300℃, the drying time is 4~24h, the calcination temperature is 200℃~800℃, and the calcination time is 2~24h.
[0024] Furthermore, the impregnation method includes the following steps:
[0025] S1. Dissolve the salts of A and B in water to prepare a metal salt aqueous solution. Place M in the metal salt aqueous solution for immersion while stirring during the immersion process.
[0026] S2. After impregnation, remove the solvent, dry the resulting precipitate, and then calcine it to obtain the composite metal oxide catalyst.
[0027] Furthermore, the concentration of the aqueous solution of the metal salt is 0.01–2 mol / L.
[0028] Furthermore, the volume ratio of the metal salt aqueous solution to the precipitant aqueous solution is (1-500):(1-500).
[0029] Furthermore, the stirring temperature is 30℃~90℃, and the stirring time is 2~24h.
[0030] Furthermore, the drying temperature is 60℃~300℃, the drying time is 4~24h, the calcination temperature is 200℃~800℃, and the calcination time is 2~24h.
[0031] Furthermore, the deposition and precipitation method includes the following steps:
[0032] S1. Dissolve the salts of A and B in water to prepare an aqueous solution of metal salts. Place M in the aqueous solution of metal salts and add a water-soluble precipitant dropwise to perform co-deposition precipitation.
[0033] S2. After drying the obtained precipitate, calcine it to obtain the composite metal oxide catalyst.
[0034] Furthermore, the concentration of the metal salt aqueous solution is 0.01–2 mol / L, and the concentration of the precipitant aqueous solution is 1–5 times the concentration of the metal salt aqueous solution.
[0035] Furthermore, the volume ratio of the metal salt aqueous solution to the precipitant aqueous solution is (1-500):(1-500).
[0036] Furthermore, the coprecipitation temperature is 30℃~90℃, and the coprecipitation pH is 6~12.
[0037] Furthermore, the drying temperature is 60℃~300℃, the drying time is 4~24h, the calcination temperature is 200℃~800℃, and the calcination time is 2~24h.
[0038] Furthermore, the salt is one or more of nitrates, acetates, halides, and sulfates.
[0039] Furthermore, the precipitant is one or more of ammonia, ammonium carbonate, sodium carbonate, potassium carbonate, sodium bicarbonate, potassium bicarbonate, sodium hydroxide, and potassium hydroxide.
[0040] Another object of the present invention is to provide the application of the catalyst in the preparation of formamide by hydrogenation of carbon dioxide.
[0041] Furthermore, the preparation of formamide by carbon dioxide hydrogenation is carried out in a pressurized fixed-bed continuous flow reactor.
[0042] Furthermore, before use, the catalyst is compressed into tablets, crushed, and passed through a 20-80 mesh sieve.
[0043] Furthermore, the conditions for preparing formamide by carbon dioxide hydrogenation are as follows: reaction pressure 1-10 MPa, reaction temperature 100℃-400℃, gas hourly space velocity (GHSV) 3000-40000 mL / (g·h), n(H2):n(CO2) molar ratio = 1-8; the liquid is dimethylamine or its equivalent dimethylamine carbon dioxide salt, and the liquid hourly space velocity (LHSV) is 1-20 mL / (g·h).
[0044] Furthermore, when the amine compound is dimethylamine or its equivalent dimethylamine carbon dioxide salt, the product is DMF.
[0045] The reaction formula for the preparation of formamide by hydrogenation of carbon dioxide is as follows:
[0046]
[0047] In the reaction formula:
[0048] R1 and R2 are each independently selected from: hydrogen, substituted or unsubstituted C1-C. 20 Alkyl, substituted or unsubstituted C4-C 10 Cycloalkyl, substituted or unsubstituted C6-C 24 Aryl or heteroaryl, substituted or unsubstituted C7-C 25arylalkyl or heteroarylalkyl, -(CH2) n -ORs or -(CH2) n -NR4R5, where η=1-8;
[0049] The term "substituted" refers to the substitution of one or more hydrogen atoms in a group by the following substituents:
[0050] Halogen, C1-C4 alkyl, C1-C4 haloalkyl, C2-C6 alkenyl, C2-C6 alkynyl, C1-C6 alkoxy, hydroxyl, amino, mercapto.
[0051] Compared with the prior art, the beneficial technical effects of the present invention are as follows:
[0052] The composite metal oxide catalyst of this invention exhibits high catalytic efficiency, good selectivity, economic efficiency, environmental friendliness, and simple operation. It requires no external solvents, additives, or other additives and effectively improves the selectivity for the preparation of formamide by carbon dioxide hydrogenation. The optimal operating temperature of this catalyst is 150℃~400℃. It is resistant to sintering and exhibits good stability; after operating at 300℃ for 1000 hours, the space-time yield shows almost no decrease. Using the catalyst of this invention, DMF can be obtained in one step, and subsequent separation and purification processes are simple, which is beneficial for further industrial applications. Attached Figure Description
[0053] The present invention will be further described below with reference to the accompanying drawings.
[0054] Figure 1 This is a schematic diagram of the fixed-bed continuous reaction device of the present invention;
[0055] Figure 2 The graph shows the results of the long-term stability test of the ZnTiO(1:3) catalyst in Example 18 of this invention. Detailed Implementation
[0056] The technical solution provided by the present invention will be further described below with reference to the embodiments.
[0057] Example 1
[0058] Weigh 5 mmol Zn(NO3)2·6H2O and 10 mmol Ti(SO4)2·xH2O to prepare a 100 mL aqueous solution of the metal salt and place it in a 500 mL beaker. Weigh 27.5 mmol (NH4)2CO3 to prepare a 100 mL aqueous solution. Under the conditions of 60 °C and stirring speed of 600 r / min, the prepared (NH4)2CO3 solution is added dropwise to the metal salt aqueous solution at a dropping rate of 3 mL / min. After the (NH4)2CO3 solution is completely consumed, the resulting precipitate mother liquor is aged at 60 °C for 4 h, cooled, filtered naturally, washed 3 times with deionized water, filtered under vacuum, dried at 60 °C, and calcined in air at 500 °C for 3 h to obtain the composite metal oxide catalyst.
[0059] The tablets were compressed at 10 MPa, crushed, and screened at 40-80 mesh for evaluation.
[0060] Weigh 0.5g of the selected catalyst and load it into a reaction tube with an inner diameter of 15mm. Introduce the raw material gas n(H2):n(CO2)=3. The reaction is carried out under the conditions of 2MPa, 300℃, GHSV=24000mL / (h·g), and LHSV=5g / (h·g).
[0061] The reaction tail gas was discharged to atmospheric pressure via a back pressure valve and sampled at 180℃ using a 10-port gas chromatograph. Online analysis was performed using a thermal conductivity detector (TCD) and flame ionization detector (FID) on an Agilent GC-8890B gas chromatograph. The TCD used a 3m long column coupled with a Propark Q 5A molecular sieve (Agilent), operating at 85℃, to separate and detect CO2, Ar, and CO. The FID used a TG-BOND Q capillary column (Thermo Fisher Scientific), 30m × 0.32mm × 10μm, using Ar as the carrier gas, to separate and detect low-carbon hydrocarbons and alcohols. CO2 conversion and the C-based selectivity and space-time yield of CO, alcohols, and hydrocarbons were calculated using the C-based normalization method.
[0062] Example 2
[0063] The metal salts used in the catalyst preparation were 5 mmol In(NO3)3·5H2O and 10 mmol Ti(SO4)2·xH2O, and the precipitant was 30.3 mmol (NH4)2CO3. Other preparation and evaluation steps were the same as in Example 1.
[0064] Example 3
[0065] The metal salts used in the catalyst preparation were 5 mmol Cd(NO3)2·4H2O and 10 mmol Ti(SO4)2·xH2O, and the precipitant was 27.5 mmol (NH4)2CO3. Other preparation and evaluation steps were the same as in Example 1.
[0066] Example 4
[0067] The metal salts used in the catalyst preparation were 5 mmol Zn(NO3)2·6H2O and 10 mmol Zr(NO3)4·5H2O, and the precipitant used was 27.5 mmol (NH4)2CO3. Other preparation and evaluation steps were the same as in Example 1.
[0068] Example 5
[0069] The metal salts used in the catalyst preparation were 5 mmol In(NO3)3·5H2O and 10 mmol Zr(NO3)4·5H2O, and the precipitant was 30.3 mmol (NH4)2CO3. Other preparation and evaluation steps were the same as in Example 1.
[0070] Example 6
[0071] The metal salts used in the catalyst preparation were 5 mmol Cd(NO3)2·4H2O and 10 mmol Zr(NO3)4·5H2O, and the precipitant was 27.5 mmol (NH4)2CO3. Other preparation and evaluation steps were the same as in Example 1.
[0072] Example 7
[0073] The metal salts used in the catalyst preparation were 10 mmol Zn(NO3)2·6H2O and 10 mmol Cr(NO3)3·9H2O, and the precipitant was 27.5 mmol (NH4)2CO3. Other preparation and evaluation steps were the same as in Example 1.
[0074] Example 8
[0075] The metal salts used in the catalyst preparation were 4.5 mmol In(NO3)3·5H2O and 0.5 mmol Cr(NO3)3·9H2O, and the precipitant was 8.3 mmol (NH4)2CO3. Other preparation and evaluation steps were the same as in Example 1.
[0076] Example 9
[0077] The metal salts used in the catalyst preparation were 5 mmol Cd(NO3)2·4H2O and 10 mmol Cr(NO3)3·9H2O, and the precipitant was 22 mmol (NH4)2CO3. Other preparation and evaluation steps were the same as in Example 1.
[0078] Example 10
[0079] The metal salts used in the catalyst preparation were 10 mmol Zn(NO3)2·6H2O, 10 mmol Ti(SO4)2·xH2O, and 10 mmol Zr(NO3)4·5H2O. The precipitant used was 55 mmol (NH4)2CO3. Other preparation and evaluation steps were the same as in Example 1.
[0080] Example 11
[0081] The metal salts used in the catalyst preparation were 10 mmol In(NO3)3·5H2O, 10 mmol Ti(SO4)2·xH2O, and 10 mmol Zr(NO3)4·5H2O. The precipitant used was 60.5 mmol (NH4)2CO3. Other preparation and evaluation steps were the same as in Example 1.
[0082] Example 12
[0083] The metal salts used in the catalyst preparation were 10 mmol Cd(NO3)2·4H2O, 10 mmol Ti(SO4)2·xH2O, and 10 mmol Zr(NO3)4·5H2O. The precipitant used was 55 mmol (NH4)2CO3. Other preparation and evaluation steps were the same as in Example 1.
[0084] Example 13
[0085] The metal salts used in the catalyst preparation were 10 mmol Zn(NO3)2·6H2O, 10 mmol In(NO3)3·5H2O, and 10 mmol Cd(NO3)2·4H2O. The precipitant used was 38.5 mmol (NH4)2CO3. Other preparation and evaluation steps were the same as in Example 1.
[0086] Example 14
[0087] The metal salts used in the catalyst preparation were 10 mmol Zn(NO3)2·6H2O, 10 mmol In(NO3)3·5H2O, and 10 mmol Ti(SO4)2·xH2O. The precipitant used was 49.5 mmol (NH4)2CO3. Other preparation and evaluation steps were the same as in Example 1.
[0088] Example 15
[0089] The metal salts used in the catalyst preparation were 10 mmol Zn(NO3)2·6H2O, 10 mmol In(NO3)3·5H2O, and 10 mmol Zr(NO3)4·5H2O. The precipitant used was 49.5 mmol (NH4)2CO3. Other preparation and evaluation steps were the same as in Example 1.
[0090] Example 16
[0091] The metal salts used in the catalyst preparation were 10 mmol In(NO3)3·5H2O, 10 mmol Zr(NO3)4·5H2O, and 10 mmol Cd(NO3)2·4H2O. The precipitant used was 49.5 mmol (NH4)2CO3. Other preparation and evaluation steps were the same as in Example 1.
[0092] Example 17
[0093] The metal salts used in the catalyst preparation were 4 mmol In(NO3)3·5H2O and 1 mmol Ti(SO4)2·xH2O, and the precipitant was 8.8 mmol (NH4)2CO3. The catalyst was evaluated under the conditions of 2 MPa, 310 °C, and GHSV = 24000 mL / (h·g). Other preparation and evaluation steps were the same as in Example 1.
[0094] Example 18
[0095] The metal salts used in the catalyst preparation were 2.5 mmol Zn(NO3)2·6H2O and 7.5 mmol Ti(SO4)2·xH2O, and the precipitant was 19.3 mmol (NH4)2CO3. Other preparation and evaluation steps were the same as in Example 1.
[0096] Example 19
[0097] The metal salts used in the catalyst preparation were 2.5 mmol Zn(NO3)2·6H2O and 7.5 mmol Zr(NO3)4·5H2O, and the precipitant was 19.3 mmol (NH4)2CO3. Other preparation and evaluation steps were the same as in Example 1.
[0098] Example 20
[0099] Weigh 5 mmol Zn(NO3)2·6H2O and 10 mmol Ti(SO4)2·xH2O to prepare a 100 mL aqueous solution and place it in a 500 mL beaker. Add 5 g SiO2 to the solution and maintain the temperature at 60 °C and a stirring speed of 600 r / min for 6 h. Remove the solvent by rotary evaporation. Dry the resulting solid at 60 °C and calcine it in air at 500 °C for 3 h to obtain the composite oxide catalyst. Other preparation and evaluation steps are the same as in Example 1. The catalyst evaluation results are shown in Table 1.
[0100] Example 21
[0101] Weigh 5 mmol Zn(NO3)2·6H2O and 10 mmol Ti(SO4)2·xH2O to prepare a 100 mL aqueous solution and place it in a 500 mL beaker. Add 5 g SiO2 to the solution. Weigh 27.5 mmol (NH4)2CO3 to prepare a 100 mL aqueous solution. Add the precipitant dropwise to the metal salt aqueous solution at 60 °C and a stirring speed of 1000 r / min. After the addition is complete, continue heating and stirring for 2 h. Centrifuge and wash three times with deionized water. Dry the resulting solid at 60 °C and calcine it in air at 500 °C for 3 h to obtain the composite oxide catalyst. Other preparation and evaluation steps are the same as in Example 1.
[0102] Comparative Example 1
[0103] Weigh 18 mmol Cu(NO3)2·3H2O, 9 mmol Zn(NO3)2·6H2O, and 3 mmol Al(NO3)3·9H2O to prepare a 100 mL aqueous solution. Weigh 36 mmol Na2CO3 to prepare a 100 mL aqueous solution. Place 200 mL of deionized water in a 500 mL beaker, insert a pH meter, and co-precipitate the metal salt aqueous solution and Na2CO3 aqueous solution in a parallel flow at 70 °C. Stir at 600 r / min, control the pH to 7, and the precipitation rate to 3 mL / min. Age the resulting precipitate mother liquor at 70 °C for 1 h, cool, filter naturally, wash 5 times with deionized water until no sodium ions are present in the filtrate, filter under vacuum, dry at 60 °C, and calcine in air at 350 °C for 3 h to obtain the catalyst oxidized precursor.
[0104] The tablets were compressed at 10 MPa, crushed, and screened at 40-80 mesh for evaluation.
[0105] Weigh 0.5g of the selected catalyst and load it into a reaction tube with an inner diameter of 15mm. Reduce the catalyst for 2 hours at atmospheric pressure, 300℃, and a hydrogen flow rate of 50mL / min. Then, introduce the feed gas (n(H2):n(CO2) = 3) and proceed with the reaction at 2MPa, 240℃, and GHSV = 24000mL / (h·g).
[0106] Comparative Example 2
[0107] 18 mmol of Cu(NO3)2·3H2O was weighed and prepared into a 100 mL aqueous solution. 36 mmol of Na2CO3 was weighed and prepared into a 100 mL aqueous solution. 200 mL of deionized water was placed in a 500 mL beaker, and a pH meter was inserted. The metal salt aqueous solution and Na2CO3 aqueous solution were co-precipitated at 70 °C under concurrent flow. The stirring speed was 600 r / min, the pH was controlled at 7, and the precipitation rate was 3 mL / min. The resulting precipitate mother liquor was aged at 70 °C for 1 h, cooled, and naturally filtered. The filtrate was washed five times with deionized water until no sodium ions were present. It was then filtered under vacuum, dried at 60 °C, and calcined in air at 350 °C for 3 h to obtain the oxidized precursor of the catalyst. The precursor was compressed into tablets at 10 MPa, crushed, and sieved through a 40–80 mesh screen for evaluation.
[0108] 0.5 g of the selected catalyst was weighed and loaded into a reaction tube with an inner diameter of 15 mm. Reduction was carried out for 2 h at atmospheric pressure, 300 °C, and a hydrogen flow rate of 50 mL / min. Then, a feed gas with an n(H2):n(CO2) ratio of 3 was introduced, and the reaction was carried out at 2 MPa, 240 °C, and GHSV = 24000 mL / (h·g). The catalyst evaluation results are shown in Table 1.
[0109] Comparative Example 3
[0110] Weigh 18 mmol Cu(NO3)2·3H2O and 18 mmol Zn(NO3)2·6H2O to prepare 100 mL of aqueous solution, weigh 36 mmol Na2CO3 to prepare 100 mL of aqueous solution, place 200 mL of deionized water in a 500 mL beaker, insert a pH meter, and co-precipitate the metal salt aqueous solution and Na2CO3 aqueous solution in parallel flow at 70 °C. Stir at 600 r / min, control pH = 7, and precipitation rate 3 mL / min. The resulting precipitate mother liquor is aged at 70 °C for 1 h, cooled, filtered naturally, washed 5 times with deionized water until no sodium ions are present in the filtrate, filtered by suction, dried at 60 °C, and calcined in air at 350 °C for 3 h to obtain the catalyst oxidized precursor.
[0111] The tablets were compressed at 10 MPa, crushed, and screened at 40-80 mesh for evaluation.
[0112] Weigh 0.5g of the selected catalyst and load it into a reaction tube with an inner diameter of 15mm. Reduce it for 2h at atmospheric pressure, 300℃ and hydrogen flow rate of 50mL / min. Then introduce the raw material gas n(H2):n(CO2)=3. The reaction is carried out at 2MPa, 240℃ and GHSV=24000mL / (h·g).
[0113] Comparative Example 4
[0114] Weigh 18 mmol Cu(NO3)2·3H2O and 18 mmol Zr(NO3)2·5H2O to prepare 100 mL of aqueous solution, weigh 36 mmol Na2CO3 to prepare 100 mL of aqueous solution, place 200 mL of deionized water in a 500 mL beaker, insert a pH meter, and co-precipitate the metal salt aqueous solution and Na2CO3 aqueous solution in parallel flow at 70 °C. Stir at 600 r / min, control pH = 7, and precipitation rate 3 mL / min. The resulting precipitate mother liquor is aged at 70 °C for 1 h, cooled, filtered naturally, washed 5 times with deionized water until no sodium ions are present in the filtrate, filtered by suction, dried at 60 °C, and calcined in air at 350 °C for 3 h to obtain the catalyst oxidized precursor.
[0115] The tablets were compressed at 10 MPa, crushed, and screened at 40-80 mesh for evaluation.
[0116] Weigh 0.5g of the selected catalyst and load it into a reaction tube with an inner diameter of 15mm. Reduce it for 2h at atmospheric pressure, 300℃ and hydrogen flow rate of 50mL / min. Then introduce the raw material gas n(H2):n(CO2)=3. The reaction is carried out at 2MPa, 240℃ and GHSV=24000mL / (h·g).
[0117] The catalytic effects of the catalysts in Examples 1-21 and Comparative Examples 1-4 were tested using the conversion rate of dimethylamine (DMA) and the selectivity of N,N-dimethylformamide (DMF) as indicators. The results are as follows:
[0118]
[0119]
[0120] Example 22
[0121] The catalyst prepared in Example 18 was operated at 300°C for 1000 h, and the conversion rate and selectivity of the catalyst were determined. The results are as follows: Figure 2 As shown.
[0122] Depend on Figure 2 It can be seen that the catalyst has excellent stability, and the space-time yield hardly decreased after running at 300℃ for 1000 hours.
[0123] This document uses specific examples to illustrate the principles and implementation methods of the present invention. The descriptions of the above embodiments are only for the purpose of helping to understand the method and core ideas of the present invention. Furthermore, those skilled in the art will recognize that, based on the ideas of the present invention, there will be changes in the specific implementation methods and application scope. Therefore, the content of this specification should not be construed as a limitation of the present invention.
Claims
1. The application of a composite metal oxide catalyst in the hydrogenation of carbon dioxide to formamide, characterized in that, The catalyst has the composition AOxBOy / M; Where A is Zn, Cd, or In; B is Zr, Ti, or Fe; and M is SiO2, activated carbon, or diatomaceous earth. The molar ratio of A to B is (1-10):(1-10); The M content is 0~90wt%; The feed gas for the preparation of formamide by hydrogenation of carbon dioxide has a ratio of n(H2):n(CO2)=3, and the feed liquid is dimethylamine or its equivalent dimethylamine carbon dioxide salt. The reaction is carried out under the conditions of 2 MPa, 300℃, GHSV=24000 mL / (h·g), and LHSV=5 g / (h·g).
2. The application according to claim 1, characterized in that, The catalyst is prepared by co-precipitation, impregnation, or deposition precipitation.
3. The application according to claim 2, characterized in that, The coprecipitation method includes the following steps: S1. Dissolve salts A and B in water to prepare an aqueous solution of metal salts, and add the aqueous solution of precipitant dropwise into the aqueous solution of metal salts for co-precipitation; S2. After drying the obtained precipitate, calcine it to obtain the composite metal oxide catalyst.
4. The application according to claim 2, characterized in that, The coprecipitation method includes the following steps: S1. Dissolve salts A and B in water to prepare an aqueous solution of metal salts. Add the aqueous solution of metal salts and the precipitant solution dropwise in parallel to perform co-precipitation. S2. After drying the obtained precipitate, calcine it to obtain the composite metal oxide catalyst.
5. The application according to claim 2, characterized in that, The impregnation method includes the following steps: S1. Dissolve the salts of A and B in water to prepare a metal salt aqueous solution. Place M in the metal salt aqueous solution for immersion while stirring during the immersion process. S2. After impregnation, remove the solvent, dry the resulting precipitate, and then calcine it to obtain the composite metal oxide catalyst.
6. The application according to claim 2, characterized in that, The deposition and precipitation method includes the following steps: S1. Dissolve the salts of A and B in water to prepare an aqueous solution of metal salts. Place M in the aqueous solution of metal salts and add a water-soluble precipitant dropwise for co-precipitation. S2. After drying the obtained precipitate, calcine it to obtain the composite metal oxide catalyst.
7. The application according to any one of claims 3 to 6, characterized in that, The salt is one or more of nitrates, acetates, halides, and sulfates.
8. The application according to any one of claims 3, 4, and 6, characterized in that, The precipitant is one or more of ammonia, ammonium carbonate, sodium carbonate, potassium carbonate, sodium bicarbonate, potassium bicarbonate, sodium hydroxide, and potassium hydroxide.