Preparation method of inznox bimetallic oxide catalyst and application thereof

Abstract

The application discloses InZnO x The application discloses a preparation method and application of a bimetallic oxide catalyst, in particular to the following steps: preparing a mixed solution of In and Zn metal salts and a precipitant aqueous solution, dropping the precipitant aqueous solution into the mixed solution and stirring, static aging, filtration, washing, and drying; grinding the dried precipitate in a mortar, and calcining in a muffle furnace to obtain the product. x The bimetallic oxide catalyst can be used in the preparation of amides by carbon dioxide hydrogenation. The catalyst prepared by the preparation method has the advantages of low cost, simple synthesis method, high synthesis yield, high catalytic activity, and recyclability.

Description

Technical Field

[0001] This invention belongs to the field of catalyst preparation technology, specifically relating to InZnO. x The preparation method of the bimetallic oxide catalyst also involves InZnO. x Application of bimetallic oxide catalysts in the preparation of amides by carbon dioxide hydrogenation. Background Technology

[0002] N-methylformamide (NMF) is an important organic synthesis solvent and intermediate. It can be used not only in the preparation of synthetic leather and artificial leather, pharmaceuticals, and the synthesis of pesticides such as amitraz and bismuth subsalicylate, but also in the extraction of aromatic hydrocarbons from hydrocarbon mixtures. It can also be used as a reaction solvent, refining solvent, and chemical fiber textile solvent.

[0003] N,N-dimethylformamide (DMF) is a widely used chemical raw material, mainly used in the pharmaceutical, pesticide, acrylic fiber, polyurethane, dye, and electronics industries. In organic chemical reactions, DMF is widely used as a reaction solvent and ligand due to its strong polarity and aproticity. It can also be used as a nucleophile and electrophile in chemical reactions.

[0004] The main industrial synthesis methods of formamide are: (1) one-step high-pressure catalytic synthesis of carbon monoxide-amine (Dalian Institute of Chemical Physics, Chinese Academy of Sciences, Publication No.: CN 104710321A). CO is a common toxic small molecule in the raw material and is relatively expensive. Although the process route is short, the product separation and catalyst recycling process is relatively complicated; (2) one-step synthesis of formic acid-amine. The process is simple, but using HCOOH as raw material will cause great corrosion to metal reaction instruments, and the investment in separation equipment is large; (3) two-step synthesis of methanol dehydrogenation-amine (Southwest Chemical Research Institute of the Ministry of Chemical Industry, Publication No.: CN 1049885C; Southwest Chemical Research Institute of the Ministry of Chemical Industry, Publication No.: CN 1123273 A; Suzhou Gaide Fine Materials Co., Ltd., Publication No.: CN 108892623) A; Suqian Xinya Technology Co., Ltd., Publication No.: CN105330559A), synthesizes methyl formate from methanol and formic acid, and then reacts with methylamine in a two-step process to generate formamide. This method is often used for small-scale production, but the raw material cost is high, the operation is intermittent, the process is relatively backward, and there are problems such as formic acid corrosion and acid wastewater treatment; (4) The methanol carbonylation-amine two-step synthesis method, except that CO is a common toxic small molecule, which is inconvenient to use in industry and is relatively expensive, the two-step synthesis method of formamide is complicated and time-consuming. These factors are not in line with the economics of industrial production. If CO2 can be replaced by cheap CO2, and the product can be synthesized directly from the reactants in one step, it will be very beneficial in terms of resource recycling, reducing time and money costs and mitigating the greenhouse effect. The Ding Kuiling research group at Shanghai Jiao Tong University reported a homogeneous transition metal complex catalyst that catalyzes the formation of formamide compounds from carbon dioxide, hydrogen, and amine compounds under organic or solvent-free conditions (Shanghai Institute of Organic Chemistry, Chinese Academy of Sciences, Publication No.: CN105985254 A; Shanghai Institute of Organic Chemistry, Chinese Academy of Sciences, Publication No.: WO2016131371A1). Among these, pincer-type ruthenium complexes have been used industrially to prepare N,N-dimethylformamide, exhibiting advantages such as mild reaction conditions (reaction temperature 80–120℃, total pressure of carbon dioxide and hydrogen not exceeding 70 atm), high catalytic efficiency (single-pot conversion number up to 1.94 million), good selectivity, and a wide range of applicable substrates. However, this catalyst is costly, has a complex synthesis procedure, requires stringent preparation conditions (anhydrous and oxygen-free), exhibits low synthesis yield, and is difficult to separate from the product in actual production. To overcome the above-mentioned unfavorable factors, it is necessary to develop a highly active, recyclable, heterogeneous catalyst that is low in cost, simple to synthesize, unaffected by water and oxygen, and has a high yield. Summary of the Invention

[0005] The purpose of this invention is to provide InZnO xThe proposed method for preparing bimetallic oxide catalysts addresses the problems of high synthesis cost, low synthesis yield, harsh preparation conditions, and difficulty in separating the catalysts from the products.

[0006] Another object of the present invention is to provide the above-mentioned InZnO x Application of bimetallic oxide catalysts in the preparation of amides by carbon dioxide hydrogenation.

[0007] The technical solution adopted in this invention is InZnO x The preparation method of the bimetallic oxide catalyst is carried out according to the following steps:

[0008] Step 1: Prepare a mixed solution of In and Zn metal salts using In salt and Zn salt, and heat and stir the mixed solution;

[0009] Step 2: Prepare an aqueous solution of precipitant at a concentration of 0.1–1.0 mol / L;

[0010] Step 3: Add the precipitant aqueous solution dropwise into the mixed solution from Step 1 and stir.

[0011] Step 4: Static age the mixed solution from Step 3 at 30–100℃ for 0.5–5 hours;

[0012] Step 5: Cool and filter the aged solution from Step 4, then wash the precipitate with ultrapure water, and dry the precipitate in a drying oven.

[0013] Step 6: Grind the dried precipitate from Step 5 into a fine powder using a mortar and pestle, and then calcine it in a muffle furnace. During calcineation, the temperature is increased to 400–700℃ at a heating rate of 0.5–10℃ / min under flowing gas, and held at this temperature for 2–8 hours to obtain the final product.

[0014] The invention is further characterized in that,

[0015] In step 1, the In salt is one or more of the following: chloride, nitrate, acetate, sulfate, oxalate, and acetylacetone; the Zn salt is one or more of the following: chloride, nitrate, acetate, sulfate, oxalate, and acetylacetone; the In molar fraction is 0% < In / (In+Zn) < 100%, and the total molar concentration of metal ions is 0.01-1 mol / L.

[0016] In step 2, the precipitant is one or more of ammonium carbonate, sodium carbonate, and urea.

[0017] Step 3 specifically involves:

[0018] Add the aqueous solution of the precipitant from step 2 to the center of the vortex of the mixed solution from step 1 and stir. During the mixing process, maintain the solution temperature between 70 and 80°C and add the precipitant solution dropwise at a speed of 300–1500 rpm at a drop rate of 0.1–10.0 mL / min until the pH of the mixed solution reaches 6–8. After the addition of the precipitant is completed, continue stirring at 70–80°C for 0.5–5 h.

[0019] In step 6, the flow rate of the flowing gas is 10–150 mL / min; the flowing gas can be one or more of air, oxygen, nitrogen, and helium.

[0020] The beneficial effects of this invention are: the catalyst prepared by the method of this invention has the advantages of low cost, simple synthesis method, high synthesis yield, high catalytic activity, and recyclability. Attached Figure Description

[0021] Figure 1 This refers to ZnO and InZnO prepared by the co-precipitation method in this invention. x (30%), InZnO x (40%), InZnO x (45%), InZnO x (50%), InZnO x Powder X-ray diffraction patterns of (60%) and In2O3 catalysts;

[0022] Figure 2 Different metal ratios of InZnO in this invention x Comparison of catalytic performance of catalysts in the synthesis of N-methylformamide from carbon dioxide, hydrogen, and monomethylamine;

[0023] Figure 3 This invention relates to the InZnO prepared by co-precipitation under different pH conditions. x Comparison of catalytic performance of (50%) catalysts in the synthesis of N-methylformamide from carbon dioxide, hydrogen and monomethylamine;

[0024] Figure 4 InZnO under different reactant gas ratios in this invention x Comparison of catalytic performance of (45%) catalysts in the synthesis of N-methylformamide from carbon dioxide, hydrogen and monomethylamine;

[0025] Figure 5 ZnO and InZnO prepared by the oxalic acid gelation method in this invention. x Powder X-ray diffraction patterns of (60%) and In2O3 catalysts;

[0026] Figure 6 Different metal ratios of InZnO in this inventionx Comparison of catalytic performance of catalysts in the synthesis of N,N-dimethylformamide from carbon dioxide, hydrogen and dimethylamine;

[0027] Figure 7 InZnO in this invention x Schematic diagram of catalyst structure;

[0028] Figure 8 InZnO aged for different times in this invention x (45%) Yield graph of CO2 hydrogenation to NMF catalyzed by catalyst;

[0029] Figure 9 Different qualities of InZnO in this invention x (45%) Effect of catalyst on catalytic activity;

[0030] Figure 10 InZnO in this invention x (45%) Cyclic stability test results of catalyst for CO2 hydrogenation to NMF preparation;

[0031] Figure 11 These are X-ray powder diffraction (PXRD) characterization spectra of the catalyst before and after the reaction in this invention; where 'a' represents InZnO after one reaction. x XRD pattern of (45%) catalyst; b represents InZnO after 10 reactions. x XRD pattern of (45%) catalyst;

[0032] Figure 12 In this invention, InZnO is reacted before and after the reaction. x O1s XPS spectrum of the catalyst;

[0033] Figure 13 In this invention, InZnO is reacted before and after the reaction. x XPS spectra of Zn 2p and In 3d catalysts;

[0034] Figure 14 In this invention, InZnO is reacted before and after the reaction. x Auger spectra of catalysts Zn and In. Detailed Implementation

[0035] The present invention will now be described in detail with reference to the accompanying drawings and specific embodiments.

[0036] In this invention, InZnO x The preparation method of the bimetallic oxide catalyst is carried out according to the following steps:

[0037] Step 1: Prepare a mixed solution of In and Zn metal salts using In salt and Zn salt, wherein the molar fraction of In is 0% < In / (In+Zn) < 100%, and the total molar concentration of metal ions is 0.01-1 mol / L. Heat the mixed solution to 30-100℃ and stir continuously at 300-1500 rpm.

[0038] In salts are one or more of the following: chloride salts, nitrate salts, acetate salts, sulfate salts, oxalate salts, and acetylacetone salts.

[0039] Zn salts are one or more of the following: chloride salts, nitrate salts, acetate salts, sulfate salts, oxalate salts, and acetylacetone salts.

[0040] Step 2: Prepare an aqueous solution of precipitant at a concentration of 0.1–1.0 mol / L;

[0041] The precipitant is one or more of ammonium carbonate, sodium carbonate, and urea;

[0042] Step 3: Add the aqueous solution of the precipitant from Step 2 dropwise to the mixed solution from Step 1 and stir. During the mixing process, maintain the solution temperature at 70–80℃ and add the precipitant solution dropwise at a speed of 300–1500 rpm at a drop rate of 0.1–10.0 mL / min until the pH of the mixed solution reaches 6–8. After the addition of the precipitant is completed, continue stirring while heating at 70–80℃ for 0.5–5 h.

[0043] When adding the precipitant, add it dropwise at the center of the vortex in the mixed solution;

[0044] Step 4: Static age the mixed solution from Step 3 at 30–100℃ for 0.5–5 hours;

[0045] Preferably, the aging time is 2 hours;

[0046] Step 5: Cool and filter the aged solution from Step 4, then wash the precipitate with ultrapure water, and place the precipitate in a drying oven to dry at 50–150°C.

[0047] Step 6: Grind the dried precipitate from Step 5 into a fine powder using a mortar and pestle, and then place it in a muffle furnace for calcination. During calcination, the temperature is increased to 400–700℃ at a heating rate of 0.5–10℃ / min under flowing gas, and held at that temperature for 2–8 hours to obtain the final product.

[0048] The flow rate of the flowing gas is 10–150 mL / min;

[0049] The flowing gas may be one or more of the following: air, oxygen, nitrogen, and helium.

[0050] In this invention, InZnOx The preparation method of the bimetallic oxide catalyst is carried out according to the following steps:

[0051] Step 1: Prepare an ethanolic mixed solution of In and Zn metal salts using In salt and Zn salt, wherein the molar fraction of In is 0% < In / (In+Zn) < 100%, and the total molar concentration of metal ions is 0.01-1 mol / L. Under normal temperature conditions, continuously stir at a speed of 300-1500 rpm.

[0052] In salts are one or more of the following: chloride salts, nitrate salts, acetate salts, sulfate salts, oxalate salts, and acetylacetone salts.

[0053] Zn salts are one or more of the following: chloride salts, nitrate salts, acetate salts, sulfate salts, oxalate salts, and acetylacetone salts.

[0054] Step 2: Prepare an ethanol solution of 0.1–1.0 mol / L oxalic acid;

[0055] Step 3: Under the condition of 25–50℃, the metal salt ethanol solution from Step 1 is added dropwise to the oxalic acid ethanol solution from Step 2 at a rate of 0.5–3 mL / min, and the mixture is stirred continuously at 300–1500 rpm for 0.5–5 h to obtain a mixed solution.

[0056] Step 4: Cool the mixed solution from Step 3, filter it, wash the gel with anhydrous ethanol, and dry the resulting gel in a drying oven at 50–150°C.

[0057] Step 5: Grind the dried gel from Step 4 in a mortar and pestle, then calcine it in a muffle furnace at a heating rate of 0.5–10℃ / min under a flowing gas with a flow rate of 10–150 mL / min to 300–700℃ for 2–8 h to obtain the product.

[0058] The flow rate of the flowing gas is 10–150 mL / min;

[0059] The flowing gas may be one or more of the following: air, oxygen, nitrogen, and helium.

[0060] InZnO prepared by the method of the present invention x The catalyst structure is similar to that of InZnO prepared by co-precipitation. x , structure as Figure 7 As shown, the structural difference between the catalysts obtained by the two preparation methods lies in the amount of In-O-Zn at the phase interface. It is speculated that the precipitation method yields a greater amount of In-O-Zn, while the sol-gel method yields a smaller amount of In-O-Zn. Therefore, the catalyst obtained by this method has lower reactivity.

[0061] This invention uses a co-precipitation method to prepare InZnO x Catalysts and precipitation processes involve complex chemical reactions, and there are many influencing factors during the synthesis process.

[0062] 1) During the synthesis process, with the addition of the precipitating agent, the metal nitrate solution gradually transforms into precipitates (hydroxides and carbonates). Since the solubility product of In(OH)3 is 1.41 × 10⁻⁶, the precipitate is relatively stable. -33 The solubility product of Zn(OH)₂ is less than 1.8 × 10⁻⁶. -14 Therefore, indium ions precipitate first in this process. Since indium hydroxide is amphoteric, adding too much precipitant (alkaline) may cause the precipitate to dissolve again. Indium hydroxide dissolves in alkali to form soluble indium ions, so the pH value at which the precipitate forms is crucial. Therefore, it is explored that the optimal pH value of the solution is 6–8.

[0063] 2) The temperature of the solution during precipitation also affects the particle size, crystal form, purity, and surface properties of the precipitate. At 70–80℃, the solubility of the precipitate is generally high, and the supersaturation is relatively low, thus slowing down the nucleation rate and promoting crystal growth. This results in a more compact precipitate that is easier to settle and wash, thus improving purity. During synthesis, excessively high solution temperatures increase the loss of raw materials.

[0064] 3) The method and rate of precipitant addition both affect the various properties of the precipitate. Adding the precipitant dispersedly at a slow rate, while simultaneously stirring, can prevent localized over-concentration of the solution and the formation of numerous crystal nuclei, which is beneficial for preparing high-purity, large-particle crystalline precipitates. During the experiment, it was found that a large vortex formed in the beaker during stirring. The catalyst yield differed depending on whether the precipitant was added to the center or edge of the vortex; adding the precipitant to the center of the vortex resulted in a higher reaction yield. That is, adding the precipitant to the metal salt solution at a slower linear velocity yields a higher catalyst yield. This is related to the size of the crystallites formed.

[0065] 4) During the aging process, the dissolution of small particles reduces the adsorption and encapsulation of impurities, resulting in a so-called local recrystallization effect, which can improve the purity of the precipitated product. The aging conditions, such as time and temperature, also affect the precipitation performance. It is important to note that if the aging time exceeds a certain range, it may cause post-precipitation, which will actually reduce the purity of the product. Figure 8 The results of aging for 2 hours and 5 hours were compared, and it was found that aging for 5 hours reduced the product yield. Therefore, the optimal aging time adopted in this invention is 2 hours.

[0066] Table 1. Effect of aging time on catalyst.

[0067]

[0068] a Catalyst synthesized with an aging time of 2 hours b Catalyst synthesized with an aging time of 5 hours

[0069] After optimizing the aging time, the catalyst yield was optimal after aging for 2 hours. As shown in the table above, aging time alters the surface In / Zn atomic ratio, which in turn affects the concentration, dispersibility, and proximity of active sites, thus impacting catalytic efficiency.

[0070] 5) During low-temperature calcination, the active sites generated are mainly weakly basic hydroxyl groups, while high-temperature calcination easily generates lattice defects, resulting in more active sites on the catalyst surface, which is beneficial to increasing the reaction activity. However, the calcination temperature should not be too high to avoid catalyst sintering. Furthermore, when the temperature exceeds 700℃, indium hydroxide can be reduced to metal, leading to a decrease in catalyst performance. Therefore, the calcination temperature of this invention is 400–700℃.

[0071] Example 1

[0072] 4.4624 g of Zn(NO3)2·6H2O was weighed and dissolved in a beaker containing 140 mL of deionized water. The solution was heated to 70 °C and continuously stirred at 1000 rpm. Then, a 0.32 mol / L aqueous solution of (NH4)2CO3 was added dropwise at 700 rpm at a rate of 3 mL / min until the pH of the mixed solution reached 7.0. The solution was then stirred continuously at 1000 rpm at 70 °C for 2 h, then the stirring was stopped, and the solution was aged at 70 °C for 2 h, followed by natural cooling to room temperature. The precipitate was filtered and washed three times with ultrapure water. The resulting catalyst was dried overnight at 110 °C in a drying oven. The dried catalyst was then ground finely in a mortar and calcined in a muffle furnace. The temperature was increased to 500 °C at a rate of 1 °C / min in flowing air (100 mL / min) and held for 3 h to obtain the ZnO catalyst.

[0073] Synthesis of N-methylformamide: 0.1 g ZnO catalyst was loaded into the glass liner of a reactor. The reactor was placed in an Ar glove box. 1 mL of 30% methylamine-methanol solution was added to the reactor using a syringe, and the reactor head was quickly tightened. The reactor was placed in a heating device and charged with 1 MPa of H2 at 30°C. Then, 3.5 MPa of CO2 was added while stirring at 1000 rpm. Finally, H2 was added until the total pressure reached 7 MPa. Reaction conditions: 7 MPa (30°C, n(H2) / n(CO2) = 1 / 1), 170°C, 10 h, 500 rpm. After the reaction, the reactor was cooled in an ice bath, the pressure was released, the reactor was opened, and 2 mL of methanol and 130 μL of n-butanol were added. The reactor was sealed and refluxed at 90°C and 500 rpm for 30 min. After reflux, the reactor was subjected to an ice bath treatment, and the product liquid was separated. The catalyst evaluation results are shown in Table 2 and [Table data missing]. Figure 2 .

[0074] Example 2

[0075] The metal salt used in the catalyst preparation was 5.5923 g of In(NO3)3·4H2O. Other preparation steps were the same as in Example 1, yielding the desired catalyst: In2O3. The catalyst synthesis steps and reaction conditions were the same as in Example 1. Catalyst evaluation results are shown in Table 2 and... Figure 2 .

[0076] Example 3

[0077] The metal salts used in the catalyst preparation were 1.6777 g of In(NO3)3·4H2O and 3.1225 g of Zn(NO3)2·6H2O. Other preparation steps were the same as in Example 1, yielding the desired catalyst: InZnO. x (30%), the catalyst synthesis steps and reaction conditions were the same as in Example 1. Catalyst evaluation results are shown in Table 2 and... Figure 2 .

[0078] Example 4

[0079] The metal salts used in the catalyst preparation were 2.2369 g of In(NO3)3·4H2O and 2.6764 g of Zn(NO3)2·6H2O. Other preparation steps were the same as in Example 1, yielding the desired catalyst: InZnO. x (40%), the catalyst evaluation procedure and reaction conditions were the same as in Example 1. The catalyst evaluation results are shown in Table 2 and... Figure 2 .

[0080] Example 5

[0081] The metal salts used in the catalyst preparation were 2.5165 g of In(NO3)3·4H2O and 2.4534 g of Zn(NO3)2·6H2O. Other preparation steps were the same as in Example 1, yielding the desired catalyst: InZnO. x (45%), the catalyst evaluation procedure and reaction conditions were the same as in Example 1. The catalyst evaluation results are shown in Table 2 and... Figure 2 .

[0082] Based on the X-ray photoelectron spectroscopy characterization results, InZnO x (45%) The In / Zn ratio on the catalyst surface was 3.11, which was higher than the average value of the bulk phase (In / Zn = 0.82), indicating that In was enriched on the catalyst surface. There was a synergistic effect between the In sites and Zn sites on the catalyst surface (the yield was higher than the sum of the yields of ZnO and In2O3 alone). The two sites activated different substrates respectively. When the concentrations of the two sites reached a certain ratio, this synergistic effect could be maximized, thereby maximizing the yield of the product NMF.

[0083] Example 6

[0084] The metal salts used in the catalyst preparation were 2.7964 g of In(NO3)3·4H2O and 2.2303 g of Zn(NO3)2·6H2O. Other preparation steps were the same as in Example 1, yielding the desired catalyst: InZnO. x (50%), the catalyst evaluation procedure and reaction conditions were the same as in Example 1. The catalyst evaluation results are shown in Table 2 and... Figure 2 .

[0085] Example 7

[0086] The metal salts used in the catalyst preparation were 3.3554 g of In(NO3)3·4H2O and 1.7843 g of Zn(NO3)2·6H2O. Other preparation steps were the same as in Example 1, yielding the desired catalyst: InZnO. x (60%), the catalyst evaluation procedure and reaction conditions were the same as in Example 1. The catalyst evaluation results are shown in Table 2 and... Figure 2 .

[0087] Example 8

[0088] The metal salts used in the catalyst preparation were 3.9146 g of In(NO3)3·4H2O and 1.3382 g of Zn(NO3)2·6H2O. Other preparation steps were the same as in Example 1, yielding the desired catalyst: InZnO. x (70%), the catalyst evaluation procedure and reaction conditions were the same as in Example 1. The catalyst evaluation results are shown in Table 2 and... Figure 2 .

[0089] Figure 2 The molar ratio of metals In and Zn [n] In / (n In +n Zn )] Optimization was carried out, and the effects of different In contents on InZnO were explored. x The effect of catalyst on the reaction performance of NMF was investigated, and the optimal catalyst composition was found to be InZnO. x (45%).

[0090] Example 9

[0091] The metal salts used in the catalyst preparation were 2.7964 g of In(NO3)3·4H2O and 2.2303 g of Zn(NO3)2·6H2O. The pH of the mixed solution was adjusted to 6.0. Other preparation steps were the same as in Example 1, yielding the desired catalyst: InZnO. x (50%)-6.0, the catalyst evaluation procedure and reaction conditions were the same as in Example 2. The catalyst evaluation results are shown in Table 2 and... Figure 3 .

[0092] Example 10

[0093] The metal salts used in the catalyst preparation were 2.7964 g of In(NO3)3·4H2O and 2.2303 g of Zn(NO3)2·6H2O. The pH of the mixed solution was adjusted to 8.0. Other preparation steps were the same as in Example 1, yielding the desired catalyst: InZnO. x (50%)-8.0, the catalyst evaluation procedure and reaction conditions were the same as in Example 1. The catalyst evaluation results are shown in Table 2 and... Figure 3 .

[0094] Figure 3 The results show that the pH value during catalyst synthesis has a certain impact on the reaction performance. At pH 6, the yield of NMF decreased slightly, while at pH 7 and 8, the yield of NMF remained basically stable.

[0095] Example 11

[0096] The catalyst preparation steps were the same as in Example 6, except that the heating reaction conditions in the catalyst evaluation step were changed to: 7 MPa (30 °C, n(H2) / n(CO2)=2 / 1), 170 °C, 10 h, 500 rpm. The catalyst evaluation results are shown in Table 2 and... Figure 4 .

[0097] Example 12

[0098] The catalyst preparation steps were the same as in Example 6, except that the heating reaction conditions in the catalyst evaluation step were changed to: 7 MPa (30 °C, n(H2) / n(CO2)=1 / 2), 170 °C, 10 h, 500 rpm. The catalyst evaluation results are shown in Table 2 and... Figure 4 .

[0099] Figure 4 The effect of the CO2 / H2 ratio on the NMF yield was investigated. The yield was optimal when CO2 / H2 = 1 / 1; both excessively high and low CO2 / H2 ratios reduced the NMF yield.

[0100] Example 13

[0101] The catalyst was prepared using the oxalic acid gelation method, specifically according to the following steps: 7.4350 g of Zn(NO3)2·6H2O was weighed and dissolved in a beaker containing 25 mL of ethanol. The solution was dissolved by continuous stirring at 1000 rpm at room temperature. Then, 6.2120 g of H2C2O4·2H2O was weighed and dissolved in another beaker containing 25 mL of ethanol. The solution was dissolved by continuous stirring at 1000 rpm at room temperature. Next, the ethanol solution of the metal was added dropwise to the ethanol solution of oxalic acid at a rate of 0.5 mL / min at 1000 rpm, and the mixture was stirred for 2 h. The solution was filtered, and the gel was washed three times with anhydrous ethanol. The resulting catalyst was dried overnight at 110 °C in a drying oven. The dried catalyst was then ground into a fine powder using a mortar and pestle and calcined in a muffle furnace. The temperature was increased to 400℃ in flowing air (air flow rate of 10 mL / min) at a heating rate of 1℃ / min, and then calcined at 400℃ for 4 hours to obtain ZnO.

[0102] Example 14

[0103] The metal salt used in the preparation of the catalyst was 9.3213 g of In(NO3)3·4H2O. The other catalyst preparation steps were the same as in Example 13, yielding In2O3.

[0104] Example 15

[0105] The metal salts used in the catalyst preparation were 1.8642 g of In(NO3)3·4H2O and 5.9498 g of Zn(NO3)2·6H2O. Other preparation steps were the same as in Example 13, yielding InZnO. x (20%).

[0106] Synthesis of N,N-dimethylformamide: 0.1 g of catalyst and 0.4 g of DIMCARB were loaded into a glass liner inside a reactor. The reactor was placed in a heating device and maintained at 50 °C with 1 MPa of H2. Then, 3 MPa of CO2 was introduced with stirring at 1000 rpm, and finally, H2 was added until the total pressure reached 6 MPa. Reaction conditions: 6 MPa (50 °C, n(H2) / n(CO2) = 1 / 1), 230 °C, 15 h, 500 rpm. After the reaction, the reactor was cooled in an ice bath. 2.9 mL of ethanol and 100 μL of n-butanol were added to the reactor. The reactor was sealed and refluxed at 100 °C and 500 rpm for 30 min. After reflux, the product liquid was separated by ice bath treatment. The catalyst evaluation results are shown in Table 2 and [Table data missing]. Figure 6 .

[0107] Example 16

[0108] The metal salts used in the catalyst preparation were 3.7286 g of In(NO3)3·4H2O and 4.4624 g of Zn(NO3)2·6H2O. Other preparation steps were the same as in Example 13, yielding the desired catalyst: InZnO. x (40%), the catalyst evaluation procedure and reaction conditions were the same as in Example 15. The catalyst evaluation results are shown in Table 3 and... Figure 6 .

[0109] Example 17

[0110] The metal salts used in the catalyst preparation were 4.1946 g of In(NO3)3·4H2O and 2.2305 g of Zn(NO3)2·6H2O. Other preparation steps were the same as in Example 13, yielding the desired catalyst: InZnO. x (60%), the catalyst evaluation procedure and reaction conditions were the same as in Example 15. The catalyst evaluation results are shown in Table 3. Figure 5 as well as Figure 6 As shown;

[0111] Example 18

[0112] The metal salts used in the catalyst preparation were 7.4570 g of In(NO3)3·4H2O and 1.4870 g of Zn(NO3)2·6H2O. Other preparation steps were the same as in Example 13, yielding the desired catalyst: InZnO. x (80%), the catalyst evaluation procedure and reaction conditions were the same as in Example 15. The catalyst evaluation results are shown in Table 3 and... Figure 6 .

[0113] Example 19

[0114] The metal salts used in the catalyst preparation were 8.3892 g of In(NO3)3·4H2O and 0.7438 g of Zn(NO3)2·6H2O. Other preparation steps were the same as in Example 13, yielding the desired catalyst, denoted as InZnO. x (90%), the catalyst evaluation procedure and reaction conditions were the same as in Example 15. The catalyst evaluation results are shown in Table 3 and... Figure 6 .

[0115] Figure 6 InZnO with different In contents was investigated x The reaction performance of the catalyst for DMF production was investigated, and the optimal catalyst ratio was found to be InZnO. x (80%).

[0116] Table 2 below shows InZnO prepared by precipitation method with different metal ratios. x Catalytic evaluation results of NMF preparation under different catalysts, preparation conditions and different proportions of reactant gases (heating reaction conditions: 170℃, 10h, 500rpm).

[0117] Table 2 Catalytic evaluation results of the catalysts in Examples 1-12

[0118]

[0119]

[0120] Table 2 shows that the pure ZnO catalyst exhibits significantly higher activity for N-methylformamide synthesis than the pure In₂O₃ catalyst. Different metal ratios (30%, 40%, 45%, 50%, 60%, 70%) of InZnO catalysts are also shown. x The N-methylformamide synthesis activity of the catalysts exhibits a volcanic trend, with InZnO showing the most significant activity. x (45%) catalyst exhibited the best performance in the catalytic synthesis of N-methylformamide from carbon dioxide, hydrogen, and monomethylamine: under reaction conditions of 7 MPa (30 °C, n(H2) / n(CO2)=1 / 1), 170 °C, 10 h, and 500 rpm, InZnO x (45%) The catalyst has a yield of 44.0% N-methylformamide. Figure 1 and Figure 2 Furthermore, under the same reaction conditions, as the solution pH in the catalyst preparation method increased from 6.0 to 8.0, the yield of N-methylformamide reached 38.5%, which was approximately the same as at pH 7.0. Figure 3 Meanwhile, when only the proportion of reactant gases is changed, the optimal yield of N-methylformamide is observed at n(H2) / n(CO2) = 1 / 1. Figure 4 ).

[0121] Table 3 below shows InZnO prepared by the oxalic acid gel method with different metal ratios. x Evaluation results of catalyst-catalyzed preparation of DMF (heating reaction conditions: 230℃, 15h, 500rpm).

[0122] Table 3 Catalytic evaluation results of the catalysts in Examples 15-19

[0123]

[0124]

[0125] Table 3 shows that InZnO with different metal ratios (20%, 40%, 60%, 80%, 90%) x The activity of the catalysts in the synthesis of N,N-dimethylformamide exhibits a volcano-shaped curve trend, among which InZnO... x (80%) catalyst exhibited the best performance in the hydrogenation of dimethylamine to N,N-dimethylformamide via carbon dioxide: under reaction conditions of 6 MPa (50 °C, n(H2) / n(CO2)=1 / 1), 230 °C, 15 h, and 500 rpm, InZnO x (80%) catalyst has a yield of 28.6% N,N-dimethylformamide. Figure 6 ).

[0126] Figure 9 The NMF yield was investigated as a function of catalyst dosage. We found that the NMF yield gradually increased with increasing catalyst dosage, and the NMF yield did not reach saturation until the catalyst dosage reached 100 mg. This indicates that it is reasonable to verify the catalyst's cycling performance by adding fresh catalyst during the cycling test.

[0127] Figure 10 The cyclic stability of the catalyst was investigated. Experimental results showed that after 10 cycles, the NMF yield did not decrease significantly, indicating that the catalyst exhibits good stability in its reactivity.

[0128] Figure 11 We compared the XRD patterns of the fresh catalyst and the catalyst after the reaction. We found that the characteristic diffraction peaks of ZnO disappeared, indicating that InZnO... x (45%) The catalyst underwent remodeling before and after the reaction. Comparison of InZnO after one and ten cycles. x (45%) The catalyst XRD pattern showed no significant changes, indicating that the catalyst structure stabilized after catalyst reconstruction.

[0129] Figure 12 It is the InZnO before and after the reaction xXPS spectrum of catalyst O1s (45%). XPS study results of O1s show slight changes, which may be mainly due to the adsorption of organic products on the catalyst.

[0130] Figure 13 and Figure 14 These are InZnO before and after the reaction. x Experimental results for Zn 2p and In 3d, Zn LMN and In MNN catalysts (45%). The study shows that the binding energies of Zn 2p and In 3d and the Auger spectra of Zn and In do not change significantly, indicating that the valence states of Zn and In do not change significantly before and after the reaction.

Claims

1. InZnO x The application of bimetallic oxide catalysts in the hydrogenation of carbon dioxide to amides is characterized by, The amide is N-methylformamide or N,N-dimethylformamide; the InZnO x The preparation method of the bimetallic oxide catalyst is carried out according to the following steps: Step 1: Prepare a mixed solution of In and Zn metal salts using In salt and Zn salt, and heat and stir the mixed solution; Step 2: Prepare a 0.1-1.0 mol / L aqueous solution of precipitant; the precipitant is one or more of ammonium carbonate, sodium carbonate, and urea. Step 3: Add the precipitant aqueous solution dropwise to the mixed solution from Step 1 and stir; specifically: Add the aqueous solution of the precipitant from step 2 to the center of the vortex of the mixed solution from step 1 and stir. During the mixing process, maintain the solution temperature at 70-80℃ and add the precipitant solution dropwise at a speed of 300-1500 rpm at a drop rate of 0.1-10.0 mL / min until the pH of the mixed solution reaches 6-8. After the addition of the precipitant, continue stirring at 70-80℃ for 0.5-5 h. Step 4: Static age the mixed solution from Step 3 at 30-100℃ for 0.5-5 hours; Step 5: Cool and filter the aged solution from Step 4, then wash the precipitate with ultrapure water, and dry the precipitate in a drying oven. Step 6: Grind the dried precipitate from Step 5 into a fine powder using a mortar and pestle, and then calcine it in a muffle furnace. During calcineation, the temperature is increased to 400-700℃ at a heating rate of 0.5-10℃ / min under flowing gas, and held at that temperature for 2-8 hours to obtain the final product.

2. InZnO x The application of bimetallic oxide catalysts in the hydrogenation of carbon dioxide to amides is characterized by, The amide is N-methylformamide or N,N-dimethylformamide; InZnO x The preparation method of the bimetallic oxide catalyst is carried out according to the following steps: Step 1: Prepare an ethanolic solution of In and Zn metal salts using In and Zn salts, and stir continuously at room temperature; Step 2: Prepare an ethanol solution of 0.1-1.0 mol / L oxalic acid; Step 3: Under the condition of 25-50℃, the metal salt ethanol solution from Step 1 is added dropwise to the oxalic acid ethanol solution from Step 2 at a rate of 0.5-3 mL / min, and the mixture is stirred continuously at 300-1500 rpm for 0.5-5 h to obtain a mixed solution. Step 4: Cool the mixed solution from Step 3, filter it, wash the gel with anhydrous ethanol, and dry the resulting gel in a drying oven. Step 5: Grind the dried gel from Step 4 in a mortar and pestle, then calcine it in a muffle furnace at a heating rate of 0.5-10℃ / min under a flowing gas with a flow rate of 10-150 mL / min to 300-700℃ for 2-8 h to obtain the final product.

3. The application according to claim 1 or 2, characterized in that, In step 1, the In salt is one or more of chloride, nitrate, acetate, sulfate, oxalate, and acetylacetone; the Zn salt is one or more of chloride, nitrate, acetate, sulfate, oxalate, and acetylacetone; the In molar fraction is 0% < In / (In + Zn) < 100%, and the total molar concentration of metal ions is 0.01-1 mol / L.

4. The application according to claim 1, characterized in that, In step 6, the flow rate of the flowing gas is 10-150 mL / min; the flowing gas is selected from one or more of air, oxygen, nitrogen, and helium.

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