Preparation of CuMg catalyst by vacuum ammonia evaporation and its application in catalytic conversion of ethanol to butadiene

Abstract

The application provides a CuMg catalyst prepared by vacuum ammonia evaporation and application of the CuMg catalyst in catalytic conversion of ethanol into butadiene. The Cu / MgO-SiO2-VAE catalyst is prepared by vacuum ammonia evaporation with a water-soluble copper salt, a water-soluble magnesium salt and SiO2 as raw materials. Through synergistic effect between Cu and Mg metals, efficient catalytic conversion of ethanol into butadiene is realized. Through the vacuum ammonia evaporation method, the problem that the CuMg catalyst cannot be controllably synthesized by a traditional preparation method is solved, and problems such as low catalyst activity and poor selectivity of target products in the process of catalytic conversion of ethanol into butadiene are solved.

Description

Technical Field

[0001] This invention belongs to the field of biomass catalytic conversion technology, specifically relating to the preparation of CuMg catalyst by vacuum ammonia evaporation and its application in the catalytic conversion of ethanol to butadiene. Background Technology

[0002] With the rapid development of modern society, energy demand is growing rapidly. Given the limited fossil fuel resources, developing new and renewable energy sources is crucial. Biomass ethanol, produced from agricultural and forestry waste such as corn and wheat straw through biochemical methods, is a green and renewable energy source; global industrial-scale bioethanol production technology is now largely mature. Ethanol is an important small molecule platform for the conversion and utilization of biomass resources. Over the past few decades, global bioethanol production technology has made significant progress, reaching approximately 90 million tons in 2023. my country's annual bioethanol production capacity exceeds 6 million tons, ranking third globally. Faced with surplus ethanol, its high-value utilization is particularly important. Under the action of efficient catalysts, ethanol can be catalytically converted into various important organic chemicals, including aldehydes, butadiene, fatty alcohols / aldehydes, and aromatic alcohols / aldehydes. These products are key intermediates in the production of fragrances, perfumes, and pharmaceuticals, or can be used directly as biofuels, solvents, and surfactants.

[0003] 1,3-Butadiene is an important chemical substance, serving as a monomer feedstock for synthetic rubber and resins. Industrially, over 95% of 1,3-butadiene originates as a byproduct of naphtha catalytic cracking to ethylene and propylene, with smaller amounts derived from C4 alkane or olefin dehydrogenation. Due to the discovery of shale gas and condensate oil, industrial ethylene and propylene production is gradually shifting towards ethane and propane dehydrogenation processes, significantly impacting butadiene yields. Therefore, there is a strong need to explore novel renewable energy-based technologies. With advancements in biomass conversion technology and the abundance of bioethanol sources, researching green production processes for the directed catalytic conversion of ethanol to 1,3-butadiene, using ethanol as a key renewable platform compound, is of significant strategic importance for the sustainable development of low-carbon olefins.

[0004] Existing technologies mainly include a 1% Ag / MgO-SiO2 catalyst prepared by dry grinding, which exhibits good catalytic activity at Mg / Si=2 and a reaction temperature of 400 ℃, achieving a conversion rate of 44% and a butadiene selectivity of 46%. Using a four-component composite oxide of AgO / Cr2O3-MgO-SiO2 as a catalyst, the ethanol conversion rate is ≥65% and the butadiene yield is ≥35%. The fundamental reason for the generally low activity and poor selectivity of these catalysts lies in the complexity of the catalytic reaction process, which mainly involves two steps: the first step is the dehydrogenation of ethanol to acetaldehyde; the second step is the aldol condensation reaction between the generated acetaldehyde and ethanol, ultimately producing butadiene. Cu-based catalysts can efficiently catalyze the ethanol dehydrogenation reaction, while Mg-based catalysts can achieve the aldol condensation reaction. However, Mg(OH)2 or MgO can react with water at higher temperatures, making precipitation difficult, while highly active Cu-based catalysts require higher precipitation temperatures. The vacuum ammonia evaporation method described in this invention can effectively control the precipitation of Mg and Cu during the catalyst synthesis process, obtain a highly active CuMg catalyst with controllable ratio, and apply it to the efficient catalytic conversion of ethanol to butadiene, achieving an ethanol conversion rate of >90% and a butadiene selectivity of >55%. Summary of the Invention

[0005] The purpose of this invention is to provide a CuMg catalyst for vacuum ammonia evaporation. This preparation method can achieve a controllable CuMg ratio, and the obtained catalyst can achieve efficient catalytic conversion of ethanol to butadiene with a conversion rate of over 87% and a butadiene selectivity of over 57%. Furthermore, in the high-temperature range (400 ℃~500 ℃), the butadiene yield can reach up to 50%. This solves the problem that traditional preparation methods cannot controllably synthesize CuMg catalysts, as well as the problems of low catalyst activity and poor selectivity of target products in the traditional process of catalytic conversion of ethanol to butadiene.

[0006] To achieve the above objectives, the present invention adopts the following technical solution: A CuMg catalyst prepared by vacuum ammonia evaporation, wherein the catalyst components include Cu, an active component for the conversion of ethanol to acetaldehyde, Mg, an active component for the condensation reaction of ethanol and acetaldehyde to generate butadiene, and SiO2, a catalyst support.

[0007] The molar ratio of the active component Cu on the catalyst support SiO2 is 0.5:1000 to 105:1000; the active component Cu is derived from water-soluble copper salt.

[0008] The molar ratio of the active component Mg loaded on the catalyst support SiO2 is 0.5:1 to 100:1; the active component Mg is derived from water-soluble magnesium salts.

[0009] The catalyst support is SiO2.

[0010] The above-mentioned method for preparing CuMg catalyst by vacuum ammonia evaporation, namely the vacuum ammonia evaporation method, includes the following steps: (1) Dissolve the copper compound in deionized water, stir at room temperature, add 5~50 mL of concentrated ammonia, stir for 1~20 min, add SiO2, stir at room temperature for 1~6 h, and then heat in an open water bath at 30~80 ℃ for 1~6 h; (2) The sample obtained in step (1) was dried at 60~90 °C to obtain Cu-SiO2 catalyst precursor; (3) The catalyst precursor obtained in step (2) is calcined and then cooled to room temperature to obtain Cu-SiO2 catalyst; the calcination temperature is 300~800 ℃ and the calcination time is 3~9 h. (4) Dissolve the magnesium compound in deionized water, stir at room temperature for 1-20 min, add the Cu-SiO2 catalyst prepared in step (3), stir at room temperature for 1-20 min, add 10-100 mL of 1 mol / L ammonia water, stir for 10-30 min, add 10-100 mL of concentrated ammonia water, stir at room temperature for 1-6 h, and then stir under vacuum at 40-90 ℃ for 0.5-3 h; (5) The sample obtained in step (4) is dried at 60~90 °C to obtain CuMg catalyst precursor; (6) The catalyst precursor obtained in step (5) is calcined and then cooled to room temperature to obtain CuMg catalyst, which is labeled as Cu / MgO-SiO2-VAE catalyst; the calcination temperature is 300~800 ℃ and the calcination time is 3~9 h.

[0011] Furthermore, the concentration of the concentrated ammonia solution is 13.38 mol / L.

[0012] Furthermore, the Cu / MgO-SiO2-VAE catalyst has a pore volume of 0.2~0.8 cm³. 3 / g, with an average pore size of 2~20nm and a specific surface area of ​​100.0~400.0 m². 2 / g.

[0013] Application: The Cu / MgO-SiO2-VAE catalyst prepared by the above method is used for the catalytic conversion of ethanol to butadiene, including: using ethanol as the reactant, employing a fixed-bed reactor, using nitrogen as the carrier gas, and the ethanol feedstock undergoes a catalytic conversion reaction to generate butadiene.

[0014] The specific steps involve placing the Cu / MgO-SiO2-VAE catalyst in a fixed-bed tubular reactor for reaction. The catalyst pretreatment conditions are as follows: treatment at 200–400 °C with H2 / N2 (5–100 Vol.%) for 0–60 min, followed by treatment at 300–500 °C with pure N2 for 0–60 min. The fixed-bed reaction temperature is 240–500 °C, and the reaction pressure is atmospheric pressure. The feed rate of the ethanol feedstock is a mass hourly space velocity (WHSV) of 0–8.8 h. -1 The volume hourly space velocity (GHSV) is 0~12000 h. -1 The reaction raw material is high-purity ethanol, and no other solvents are added.

[0015] Compared with existing technologies, the present invention has the following advantages: (1) The catalyst with Cu and Mg supported by SiO2 is used in this invention. The active components are highly dispersed and have a strong interaction with SiO2, which can inhibit the aggregation and sintering of active component particles during the reaction process. This overcomes the problems of easy aggregation and deactivation of active components during the catalytic conversion of ethanol to butadiene, and improves the stability of the catalyst.

[0016] (2) The vacuum ammonia evaporation method described in this invention is simple to prepare and effectively controls the ratio of Mg to Cu during the catalyst synthesis process.

[0017] (3) The CuMg catalyst described in this invention does not involve precious metals and has a relatively low cost. In the catalytic conversion of ethanol to butadiene, it exhibits high catalytic activity, achieving an ethanol conversion rate of >90% and a butadiene selectivity of >55%. Attached Figure Description

[0018] To make the content of this invention easier to understand, the technical solution of this invention will be further described below with reference to the accompanying drawings and specific embodiments.

[0019] Figure 1 These are the XRD spectra of Examples 1-6 and Comparative Examples 1-3 of the catalyst for the ethanol-catalyzed preparation of butadiene according to the present invention; Figure 2 This is a comparison chart showing the activity test results of different catalysts obtained in Examples 1-6 and Comparative Examples 1-3 of this invention for the catalytic conversion of ethanol to butadiene at 450 °C. Detailed Implementation

[0020] To enable those skilled in the art to better understand the technical solution of the present invention, the present invention will be further described in detail below with reference to the accompanying drawings and preferred embodiments. Example 1

[0021] The preparation of MgO-VAE catalyst includes the following steps: (1) Dissolve 2.7350 g of Mg(NO3)2·6H2O in 50 mL of deionized water, stir on a magnetic stirrer at room temperature for 10 min at a stirring speed of 500 r / min, add 50 mL of 1 mol / L ammonia water dropwise, stir for 15 min, then add 50 mL of 13.38 mol / L ammonia water dropwise, stir at room temperature for 3 h, and then stir under vacuum conditions (-0.08 MPa) at 50 ℃ for 1 h 15 min; (2) The sample obtained in step (1) was dried at 80°C to obtain the MgO-VAE catalyst precursor; (3) The catalyst precursor obtained in step (2) is calcined and then cooled to room temperature to obtain MgO-VAE catalyst; the calcination temperature is 600 °C and the calcination time is 6 h. Example 2

[0022] The preparation of the MgO-SiO2-VAE catalyst with a molar ratio of Mg:Si = 8 includes the following steps: (1) Dissolve 2.7350 g Mg(NO3)2·6H2O in 50 mL of deionized water, stir on a magnetic stirrer at room temperature for 10 min at a stirring speed of 500 r / min, add 0.0720 g SiO2 and stir at room temperature for 10 min, then add 50 mL of 1 mol / L ammonia water dropwise, stir for 15 min, then add 50 mL of concentrated ammonia water (13.38 mol / L), stir at room temperature for 3 h, and then stir under vacuum conditions (-0.08 MPa) at 50 ℃ for 1 h 15 min; (2) The sample obtained in step (1) was dried at 80 °C to obtain the Mg:Si=8 MgO-SiO2-VAE catalyst precursor; (3) The catalyst precursor obtained in step (2) is calcined and then cooled to room temperature to obtain Mg:Si=8 MgO-SiO2-VAE catalyst; the calcination temperature is 600 ℃ and the calcination time is 6 h. Example 3

[0023] The preparation of a Cu / MgO-SiO2-VAE catalyst with a molar ratio of Cu:Mg:Si = 2.4:8000:1000 includes the following steps: (1) Weigh 0.0085 g Cu(NO3)2·3H2O and dissolve it in 100 mL of deionized water. Stir it on a magnetic stirrer at room temperature for 10 min at a stirring speed of 470 r / min. Add 20 mL of concentrated ammonia (13.38 mol / L) and stir for 10 min. Then add 0.9 g SiO2 and stir at room temperature for 4 h. Then heat it in an open water bath at 50 ℃ for 4 h. (2) The sample obtained in step (1) was dried at 80 °C to obtain Cu:Si=2.4:1000 Cu-SiO2 catalyst precursor; (3) The catalyst precursor obtained in step (2) was calcined and then cooled to room temperature to obtain Cu:Si=2.4:1000 Cu-SiO2 catalyst; the calcination temperature was 600 ℃ and the calcination time was 6 h. (4) Weigh 2.7350 g of Mg(NO3)2·6H2O and dissolve it in 50 mL of deionized water. Stir it on a magnetic stirrer at room temperature for 10 min at a stirring speed of 500 r / min. Add 0.0722 g of Cu:Si=2.4:1000 Cu-SiO2 prepared in step (3) and stir at room temperature for 10 min. Then add 50 mL of 1 mol / L ammonia water and stir for 15 min. Then add 50 mL of concentrated ammonia water (13.38 mol / L) and stir at room temperature for 3 h. Then stir under vacuum conditions (-0.08 MPa) at 50 ℃ for 1 h and 15 min. (5) The sample obtained in step (4) was dried at 80 °C to obtain Cu:Mg:Si=2.4:8000:1000 Cu / MgO-SiO2-VAE catalyst precursor; (6) The catalyst precursor obtained in step (5) is calcined and then cooled to room temperature to obtain Cu:Mg:Si=2.4:8000:1000 Cu / MgO-SiO2-VAE catalyst; the calcination temperature is 600 ℃ and the calcination time is 6 h. Example 4

[0024] The preparation of a Cu / MgO-SiO2-VAE catalyst with a molar ratio of Cu:Mg:Si = 4.7:8000:1000 includes the following steps: (1) Weigh 0.0171 g Cu(NO3)2·3H2O and dissolve it in 100 mL of deionized water. Stir it on a magnetic stirrer at room temperature for 10 min at a stirring speed of 470 r / min. Add 20 mL of concentrated ammonia (13.38 mol / L) and stir for 10 min. Then add 0.9 g SiO2 and stir at room temperature for 4 h. Then heat it in an open water bath at 50 ℃ for 4 h. (2) The sample obtained in step (1) was dried at 80 °C to obtain Cu:Si=4.7:1000 Cu-SiO2 catalyst precursor; (3) The catalyst precursor obtained in step (2) was calcined and then cooled to room temperature to obtain Cu:Si=4.7:1000 Cu-SiO2 catalyst; the calcination temperature was 600 ℃ and the calcination time was 6 h. (4) Weigh 2.7350 g of Mg(NO3)2·6H2O and dissolve it in 50 mL of deionized water. Stir it on a magnetic stirrer at room temperature for 10 min at a stirring speed of 500 r / min. Add 0.0724 g of Cu:Si=4.7:1000 Cu-SiO2 prepared in step (3) and stir at room temperature for 10 min. Then add 50 mL of 1 mol / L ammonia water and stir for 15 min. Then add 50 mL of concentrated ammonia water (13.38 mol / L) and stir at room temperature for 3 h. Then stir under vacuum conditions (-0.08 MPa) at 50 ℃ for 1 h and 15 min. (5) The sample obtained in step (4) was dried at 80 °C to obtain Cu:Mg:Si=4.7:8000:1000 Cu / MgO-SiO2-VAE catalyst precursor; (6) The catalyst precursor obtained in step (5) is calcined and then cooled to room temperature to obtain Cu:Mg:Si=4.7:8000:1000 Cu / MgO-SiO2-VAE catalyst; the calcination temperature is 600 ℃ and the calcination time is 6 h. Example 5

[0025] The preparation of a Cu / MgO-SiO2-VAE catalyst with a molar ratio of Cu:Mg:Si = 9.5:8000:1000 includes the following steps: (1) Weigh 0.0346 g Cu(NO3)2·3H2O and dissolve it in 100 mL of deionized water. Stir it on a magnetic stirrer at room temperature for 10 min at a stirring speed of 470 r / min. Add 20 mL of concentrated ammonia (13.38 mol / L) and stir for 10 min. Then add 0.9 g SiO2 and stir at room temperature for 4 h. Then heat it in an open water bath at 50 ℃ for 4 h. (2) The sample obtained in step (1) was dried at 80 °C to obtain Cu:Si=9.5:1000 Cu-SiO2 catalyst precursor; (3) The catalyst precursor obtained in step (2) was calcined and then cooled to room temperature to obtain Cu:Si=9.5:1000 Cu-SiO2 catalyst; the calcination temperature was 600 ℃ and the calcination time was 6 h. (4) Weigh 2.7350 g of Mg(NO3)2·6H2O and dissolve it in 50 mL of deionized water. Stir it on a magnetic stirrer at room temperature for 10 min at a stirring speed of 500 r / min. Add 0.0727 g of Cu:Si=9.5:1000 Cu-SiO2 prepared in step (3) and stir it at room temperature for 10 min. Then add 50 mL of 1 mol / L ammonia water and stir it for 15 min. Then add 50 mL of concentrated ammonia water (13.38 mol / L) and stir it at room temperature for 3 h. Then stir it under vacuum conditions (-0.08 MPa) at 50 ℃ for 1 h and 15 min. (5) The sample obtained in step (4) was dried at 80 °C to obtain the catalyst Cu:Mg:Si=9.5:8000:1000 Cu / MgO-SiO2-VAE precursor; (6) The catalyst precursor obtained in step (5) is calcined and then cooled to room temperature to obtain Cu:Mg:Si=9.5:8000:1000 Cu / MgO-SiO2-VAE catalyst; the calcination temperature is 600 ℃ and the calcination time is 6 h. Example 6

[0026] The preparation of a Cu / MgO-SiO2-VAE catalyst with a molar ratio of Cu:Mg:Si = 105.0:8000:1000 includes the following steps: (1) Weigh 0.3805 g Cu(NO3)2·3H2O and dissolve it in 100 mL of deionized water. Place it on a magnetic stirrer at room temperature and stir for 10 min at a stirring speed of 470 r / min. Add 20 mL of concentrated ammonia (13.38 mol / L) and stir for 10 min. Then add 0.9 g SiO2 and stir at room temperature for 4 h. Then heat in an open water bath at 50 ℃ for 4 h. (2) The sample obtained in step (1) was dried at 80 °C to obtain Cu:Si=105.0:1000 Cu-SiO2 catalyst precursor; (3) The catalyst precursor obtained in step (2) was calcined and then cooled to room temperature to obtain Cu:Si=105.0:1000 Cu-SiO2 catalyst; the calcination temperature was 600 ℃ and the calcination time was 6 h. (4) Weigh 2.7350 g of Mg(NO3)2·6H2O and dissolve it in 50 mL of deionized water. Stir it on a magnetic stirrer at room temperature for 10 min at a stirring speed of 500 r / min. Add 0.0731 g of Cu:Si=105.0:1000Cu-SiO2 prepared in step (3) and stir at room temperature for 10 min. Then add 50 mL of 1 mol / L ammonia water and stir for 15 min. Then add 50 mL of concentrated ammonia water (13.38 mol / L) and stir at room temperature for 3 h. Then stir under vacuum conditions (-0.08 MPa) at 50 ℃ for 1 h and 15 min. (5) The sample obtained in step (4) was dried at 80 °C to obtain Cu:Mg:Si=105.0:8000:1000 Cu / MgO-SiO2-VAE catalyst precursor; (6) The catalyst precursor obtained in step (5) is calcined and then cooled to room temperature to obtain Cu:Mg:Si=105.0:8000:1000 Cu / MgO-SiO2-VAE catalyst; the calcination temperature is 600 ℃ and the calcination time is 6 h.

[0027] Comparative Example 1

[0028] The preparation of a Cu / MgO-SiO2-KOH catalyst with a molar ratio of Cu:Mg:Si = 4.7:8000:1000 includes the following steps: (1) Dissolve 2.7350 g Mg(NO3)2·6H2O and 0.0015 g Cu(NO3)2·3H2O in 50 mL of deionized water, stir on a magnetic stirrer at room temperature for 10 min at a stirring speed of 470 r / min, add 0.0803 g SiO2 and stir at room temperature for 10 min, then add 81 mL of 0.3 mol / L KOH solution dropwise, stir for 15 min, then add 14 mL of 0.9 mol / L KOH solution dropwise, stir at room temperature for 3 h, and then heat in an open water bath at 70 ℃ for 1 h 15 min; (2) The sample obtained in step (1) was dried at 80 °C to obtain Cu:Mg:Si=4.7:8000:1000 Cu / MgO-SiO2-KOH catalyst precursor; (3) The catalyst precursor obtained in step (2) was calcined and then cooled to room temperature to obtain Cu:Mg:Si=4.7:8000:1000 Cu / MgO-SiO2-KOH catalyst; the calcination temperature was 600 ℃ and the calcination time was 6 h.

[0029] Comparative Example 2

[0030] The preparation of a physical mixture (PM) catalyst with a molar ratio of Mg:Si=8:1 (MgO-SiO2-KOH) and Cu:Si=4.7:1000 (Cu-SiO2) includes the following steps: (1) Dissolve 2.7350 g of Mg(NO3)2·6H2O in 50 mL of deionized water, stir on a magnetic stirrer at room temperature for 10 min at a stirring speed of 470 r / min, add 0.0803 g of SiO2 and stir at room temperature for 10 min, then add 81 mL of 0.3 mol / L KOH solution dropwise, stir for 15 min, then add 14 mL of 0.9 mol / L KOH solution dropwise, stir at room temperature for 3 h, and then heat in an open water bath at 70 ℃ for 1 h 15 min; (2) The sample obtained in step (1) was dried at 80 °C to obtain a Mg:Si=8:1 MgO-SiO2-KOH catalyst precursor; (3) Weigh 0.0171 g Cu(NO3)2·3H2O and dissolve it in 100 mL of deionized water. Stir it on a magnetic stirrer at room temperature for 10 min at a stirring speed of 470 r / min. Add 20 mL of concentrated ammonia (13.38 mol / L) and stir for 10 min. Then add 0.9 g SiO2 and stir at room temperature for 4 h. Then heat it in an open water bath at 50 ℃ for 4 h. (4) The sample obtained in step (3) was dried at 80 °C to obtain Cu:Si=4.7:1000 Cu-SiO2 catalyst precursor; (5) The catalyst precursors obtained in steps (2) and (4) are calcined and then cooled to room temperature to obtain Mg:Si=8:1MgO-SiO2-KOH catalyst and Cu:Si=4.7:1000 Cu-SiO2 catalyst; the calcination temperature is 600 ℃ and the calcination time is 6 h.

[0031] (6) Take 0.25 g of Mg:Si=8:1 MgO-SiO2-KOH catalyst and 0.0389 g of Cu:Si=4.7:1000 Cu-SiO2 catalyst from the sample obtained in step (5) and physically mix them to obtain Mg:Si=8:1 MgO-SiO2-KOH and Cu:Si=4.7:1000 Cu-SiO2 physical mixed (PM) catalyst.

[0032] Comparative Example 3

[0033] The preparation of a Cu / MgO-SiO2-AE catalyst with a molar ratio of Cu:Mg:Si = 4.7:8000:1000 includes the following steps: (1) Weigh 0.0171 g Cu(NO3)2·3H2O and dissolve it in 100 mL of deionized water. Stir it on a magnetic stirrer at room temperature for 10 min at a stirring speed of 470 r / min. Add 20 mL of concentrated ammonia (13.38 mol / L) and stir for 10 min. Then add 0.9 g SiO2 and stir at room temperature for 4 h. Then heat it in an open water bath at 50 ℃ for 4 h. (2) The sample obtained in step (1) was dried at 80 °C to obtain Cu:Si=4.7:1000 Cu-SiO2 catalyst precursor; (3) The catalyst precursor obtained in step (2) was calcined and then cooled to room temperature to obtain Cu:Si=4.7:1000 Cu-SiO2 catalyst; the calcination temperature was 600 ℃ and the calcination time was 6 h. (4) Weigh 2.7350 g of Mg(NO3)2·6H2O and dissolve it in 50 mL of deionized water. Stir it on a magnetic stirrer at room temperature for 10 min at a stirring speed of 470 r / min. Add 0.0724 g of Cu:Si=4.7:1000 Cu-SiO2 prepared in step (3) and stir it at room temperature for 10 min. Then add 50 mL of 1 mol / L ammonia water and stir it for 15 min. Then add 50 mL of concentrated ammonia water (13.38 mol / L) and stir it at room temperature for 3 h. Then heat it in an open water bath at 70 ℃ for 1 h 15 min. (5) The sample obtained in step (4) was dried at 80 °C to obtain Cu:Mg:Si=4.7:8000:1000 Cu / MgO-SiO2-AE catalyst precursor; (6) The catalyst precursor obtained in step (5) is calcined and then cooled to room temperature to obtain Cu:Mg:Si=4.7:8000:1000 Cu / MgO-SiO2-AE catalyst; the calcination temperature is 600 ℃ and the calcination time is 6 h.

[0034] Example 4 and Comparative Example 3 were prepared twice using their respective preparation steps. They were named Example 4-1, Example 4-2, Comparative Example 3-1, and Comparative Example 3-2. XRF characterization tests were performed on them, and the results are shown in Table 1.

[0035] Table 1. XRF test results of the catalysts in Example 4 and Comparative Example 3.

[0036] As can be seen from the results in Table 1, the Mg:Si ratio of Example 4 prepared by vacuum ammonia evaporation method is closer to the theoretical value of 8:1 than that of Comparative Example 3 prepared by ordinary ammonia evaporation method. Moreover, the catalyst prepared by vacuum ammonia evaporation method has a yield of over 90%, which saves more reagent usage.

[0037] Example 4 and Comparative Example 3 were prepared twice using their respective preparation steps. They were named Example 4-1, Example 4-2, Comparative Example 3-1, and Comparative Example 3-2. ICP characterization tests were performed on them, and the results are shown in Table 2.

[0038] Table 2. ICP test results of catalysts in Example 4 and Comparative Example 3

[0039] As can be seen from the results in Table 2, the Mg:Si ratio of Example 4 prepared by vacuum ammonia evaporation method is 7.93:1, which is closer to the theoretical value of 8:1 for Mg:Si than that of Comparative Example 3 prepared by ordinary ammonia evaporation method.

[0040] The performance evaluation of the catalyst in the production of butadiene from biomass ethanol was carried out in a tubular quartz fixed-bed reactor with an inner diameter of 10 mm. Quartz wool, 0.1 g of catalyst, and 1.5 g of quartz sand were added sequentially to the reaction tube for fixed-bed packing. The reactor was then activated for 15 min at a reduction rate of 6 mL / min H2 and 54 mL / min N2 atmosphere at a reduction activation temperature of 300 ℃, followed by activation for 45 min at a reduction activation rate of 55 mL / min N2 atmosphere at a activation temperature of 500 ℃. During the reaction, a temperature gradient of 400 ℃, 425 ℃, 450 ℃, 475 ℃, and 500 ℃ was set in the isothermal zone of the reactor. The reaction was carried out under N2 atmosphere with a gas volumetric flow rate of 30 mL / min. Anhydrous ethanol was used as the raw material, and the liquid phase flow rate was 200 μL / h. The product was directly introduced into a gas chromatograph via a gas phase pipeline for analysis. The results were calculated using the area normalization method, and the test results are shown in Table 3.

[0041] Table 3. Texture parameters and activity test results at 450 °C for the catalysts of the examples and comparative examples.

[0042] As can be seen from the results in Table 3, the Cu / MgO-SiO2-VAE catalysts prepared based on Examples 3, 4, and 5 of this invention exhibit significantly higher ethanol conversion rates and butadiene selectivity at a reaction temperature of 450 °C compared to the catalysts in Comparative Examples 1 and 2. Therefore, the Cu / MgO-SiO2-VAE catalysts for the preparation of butadiene from biomass ethanol described in this invention have better activity than the catalysts in the comparative examples and show good prospects for industrial application.

[0043] The activity of the catalyst Cu:Mg:Si=4.7:8000:1000 Cu / MgO-SiO2-VAE prepared in Example 4 was tested at different temperatures. The specific operation was as follows: anhydrous ethanol was used as the biomass feedstock with a flow rate of 200 μL / h, the catalyst dosage was 0.1 g, the N2 volumetric flow rate was 30 mL / min, the reaction time was 30 min, and the reaction temperatures were 400℃, 425℃, 450℃, 475℃, and 500℃. The results are shown in Table 4.

[0044] Table 4. Ethanol preparation butadiene activity of Cu / MgO-SiO2-VAE at different reaction temperatures (Cu:Mg:Si = 4.7:8000:1000).

[0045] As can be seen from the results in Table 4, the Cu:Mg:Si = 4.7:8000:1000Cu / MgO-SiO2-VAE catalyst prepared based on Example 4 of the present invention has higher butadiene selectivity and yield at a reaction temperature of 450 °C than other comparative temperatures. Therefore, the optimal catalytic temperature for the catalyst for preparing butadiene from biomass ethanol as described in the present invention should be 450 °C.

[0046] Figure 1 The XRD patterns of the catalysts in the embodiments and comparative examples of this invention are shown in the figures. It can be seen from the figures that the main characteristic peaks of Examples 1-6 and Comparative Examples 1-3 are located near 37.07 °, 42.91 °, 62.25 °, 74.68 °, and 78.67 °, which are basically consistent with the characteristic peaks of MgO (PDF 01-075-0447). There are no obvious characteristic peaks of supported Cu metal ions, indicating that they are well dispersed on the support. Figure 2 The graph shows a comparison of the activity test results of different catalysts obtained in Application Examples 1-6 and Comparative Examples 1-3 of the present invention for the catalytic preparation of butadiene from ethanol at 450 °C. It can be seen from the graph that the conversion rate and butadiene selectivity of the catalysts in Examples 2-5 at a reaction temperature of 450 °C are significantly higher than those of the catalysts in Comparative Examples 1-2.

[0047] The above description is only a preferred embodiment of the present invention. All equivalent changes and modifications made within the scope of the claims of the present invention should be included in the scope of the present invention.

Claims

1. A CuMg catalyst, characterized in that: The CuMg catalyst includes an active component Cu for catalytic conversion of ethanol to acetaldehyde; an active component Mg for catalytic conversion of the generated acetaldehyde and ethanol into butadiene; and a catalyst support SiO2.

2. The CuMg catalyst according to claim 1, characterized in that: The molar ratio of the active component Cu on the catalyst support SiO2 is 0.5:1000 to 105:1000; the active component Cu is derived from water-soluble copper salt.

3. The CuMg catalyst according to claim 1, characterized in that: The molar ratio of the active component Mg loaded on the catalyst support SiO2 is 0.5:1 to 100:1; the active component Mg is derived from water-soluble magnesium salts.

4. The method for preparing the CuMg catalyst according to any one of claims 1-3, characterized in that: The preparation of CuMg catalyst by vacuum ammonia evaporation includes the following steps: (1) Dissolve the water-soluble copper salt in deionized water, add 5~50 mL of 13.38 mol / L ammonia water, stir for 1~20 min, add SiO2, stir at room temperature for 1~6 h, and then heat in an open water bath at 30~80 ℃ for 1~6 h; (2) The sample obtained in step (1) was dried at 60~90 °C to obtain Cu-SiO2 catalyst precursor; (3) The catalyst precursor obtained in step (2) is calcined and then cooled to room temperature to obtain Cu-SiO2 catalyst; the calcination temperature is 300~800 ℃ and the calcination time is 3~9 h. (4) Dissolve the water-soluble magnesium salt in deionized water, add the Cu-SiO2 catalyst prepared in step (3), stir at room temperature for 1~20 min, add 10~100 mL of 1 mol / L ammonia water, stir for 10~30 min, add 10~100 mL of 13.38 mol / L ammonia water, stir for 1~6 h, and then stir under vacuum at 40~90 ℃ for 0.5~3 h; (5) The sample obtained in step (4) is dried at 60~90 °C to obtain CuMg catalyst precursor; (6) The catalyst precursor obtained in step (5) is calcined to obtain CuMg catalyst. The calcination temperature is 300~800 ℃ and the calcination time is 3~9 h.

5. The preparation method according to claim 4, characterized in that: The CuMg catalyst has a pore volume of 0.2~0.8 cm³. 3 / g, with an average pore size of 2~20 nm and a specific surface area of ​​100.0~400.0 m². 2 / g.

6. The application of the CuMg catalyst according to any one of claims 1-3 in the catalytic conversion of ethanol to butadiene, characterized in that, Using ethanol as the reactant, a fixed-bed reactor is employed with nitrogen as the carrier gas. The ethanol feedstock undergoes a catalytic conversion reaction to produce butadiene.

7. The application according to claim 6, characterized in that, The reaction conditions include the following: 1) The reaction raw material is high-purity ethanol, and no other solvents are added; 2) The pretreatment conditions for CuMg catalyst are as follows: treatment at 200~400 ℃ and H2 / N2 (5~100 Vol.%) for 0~60 min, followed by treatment at 300~500 ℃ under pure N2 conditions for 0~60 min; 3) The reaction temperature in the fixed bed is 240~500 ℃, and the reaction pressure is atmospheric pressure; 4) The feed rate of the ethanol feedstock is 0~8.8 h⁻¹ (WHSV). -1 The volume hourly space velocity (GHSV) is 0~12000 h. -1 .

Images