Method for preparing ethanol through hydrogenation of carbon dioxide under catalysis of cobalt tungsten carbide
The preparation of ethanol by catalyzing carbon dioxide hydrogenation under mild conditions by cobalt-carbide tungsten catalysts has solved the problems of low ethanol selectivity and harsh reaction conditions of existing non-precious metal catalysts, and achieved high selectivity and efficient ethanol preparation.
Patent Information
- Application Number
- CN202510701090.5
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- Filing Date
- 2025-05-28
- Publication Date
- 2025-08-19
AI Technical Summary
When existing non-precious metal catalysts are used to make ethanol by hydrogenation of carbon dioxide, the ethanol selectivity is low and the reaction conditions are harsh, making it difficult to achieve efficient conversion.
Ethanol is prepared by catalyzing carbon dioxide hydrogenation under mild conditions by using cobalt-carbide tungsten catalyst. After replacing air in the reactor, carbon dioxide and hydrogen are introduced, the pressure and temperature are controlled to carry out the reaction, and ethanol is separated by decompression distillation.
It realizes the preparation of ethanol with high selectivity and high efficiency under mild conditions, with high catalyst activity, high ethanol selectivity and space-time yield, and low cost.
Smart Images
Figure CN120504575A_ABST
Abstract
Description
Technical Field
[0001] The invention relates to a method for preparing ethanol by catalytic hydrogenation of carbon dioxide. Background Art
[0002] Against the backdrop of the increasingly stark global conflict between increasing energy demand and declining fossil energy resources, accelerating the development of a clean and renewable energy system is crucial. Notably, atmospheric carbon dioxide concentrations have increased by over 100 ppm over the past century, with an average annual growth rate of approximately 2 ppm in the past decade, placing significant pressure on Earth's ecosystems. However, carbon dioxide is also an inexhaustible, inexpensive, and safe carbon dioxide resource, and its efficient conversion and utilization has become crucial for achieving carbon recycling. Ethanol is an important chemical product, and fermentation of grain is a primary method of producing ethanol. Although cellulosic feedstocks such as sugarcane and switchgrass can replace grain in ethanol production, existing technologies remain inadequate to address the conflict between food security and energy supply. Therefore, the development of new technologies for ethanol production is imperative. Carbon dioxide hydrogenation to ethanol is of great significance, as it not only addresses the issue of carbon dioxide resource utilization but also provides a new route for ethanol production.
[0003] Currently, reported catalytic systems for CO2 hydrogenation to ethanol primarily include precious metal, transition metal, and bimetallic catalysts supported on metal oxides. Among them, Pd and Pt noble metal-based catalysts exhibit high catalytic activity, selectivity, and excellent stability in the CO2 hydrogenation to ethanol reaction. However, their limited reserves and high cost restrict the large-scale use of noble metal catalysts. Consequently, the development of non-precious metal catalysts to replace precious metal catalysts for CO2 hydrogenation to ethanol has attracted widespread attention. Despite their low cost and abundant resources, non-precious metal catalysts still suffer from low catalytic efficiency and demanding reaction conditions. Therefore, the development of novel non-precious metal catalysts that can achieve highly selective CO2 hydrogenation to ethanol under relatively mild conditions is of great significance. Summary of the Invention
[0004] The purpose of the present invention is to solve the problems of low ethanol selectivity and harsh reaction conditions in existing non-precious metal catalyst systems used for carbon dioxide hydrogenation to ethanol, and to provide a method for preparing ethanol with high selectivity by carbon dioxide hydrogenation under mild conditions.
[0005] The method for preparing ethanol by hydrogenating carbon dioxide using cobalt tungsten carbide as a catalyst is implemented by the following steps: Place the cobalt carbide tungsten catalyst and solvent in a (high-pressure) reactor. Replace the air in the reactor with carbon dioxide at room temperature, then continue to introduce carbon dioxide to 0.5-1.5 MPa, and then continue to introduce hydrogen until the total pressure reaches 2.0-6.0 MPa. o C, and then cooled to room temperature to separate the cobalt tungsten carbide catalyst. The reaction solution was then distilled under reduced pressure to separate ethanol. The preparation method of the cobalt tungsten carbide catalyst is as follows: Citric acid, cobalt nitrate and ammonium tungstate were placed in deionized water at a molar ratio of 1: (15-45) of the total amount of cobalt and tungsten to carbon in citric acid, stirred evenly and transferred to a hydrothermal reactor, sealed and heated at 180-200°C. o C undergoes a hydrothermal reaction, and after cooling and drying, a precursor is obtained, which is placed in a tube furnace and calcined in a mixed atmosphere of nitrogen and hydrogen to obtain a cobalt tungsten carbide catalyst.
[0006] The method of preparing ethanol by hydrogenating carbon dioxide using cobalt tungsten carbide as a catalyst has the following beneficial effects: 1. The cobalt tungsten carbide catalyst used in the present invention is low-cost and simple to prepare, overcoming the shortcomings of existing non-metallic catalyst systems for carbon dioxide hydrogenation to ethanol, such as low ethanol selectivity and harsh reaction conditions; 2. The present invention provides a new method for producing ethanol under mild reaction conditions using a cobalt tungsten carbide high-efficiency catalyst. The catalyst has high activity, high ethanol selectivity and high space-time yield. BRIEF DESCRIPTION OF THE DRAWINGS
[0007] Figure 1 is the XRD spectrum of the cobalt tungsten carbide catalyst A prepared in Example 1; Figure 2 This is a scanning electron microscope photograph of the cobalt tungsten carbide catalyst A prepared in Example 1. DETAILED DESCRIPTION
[0008] Specific embodiment 1: This embodiment adopts the method of preparing ethanol by hydrogenation of carbon dioxide catalyzed by cobalt tungsten carbide according to the following steps: Place the cobalt carbide tungsten catalyst and solvent in a (high-pressure) reactor. Replace the air in the reactor with carbon dioxide at room temperature, then continue to introduce carbon dioxide to 0.5-1.5 MPa, and then continue to introduce hydrogen until the total pressure reaches 2.0-6.0 MPa. o C, and then cooled to room temperature to separate the cobalt tungsten carbide catalyst. The reaction solution was then distilled under reduced pressure to separate ethanol. The preparation method of the cobalt tungsten carbide catalyst is as follows: Citric acid, cobalt nitrate and ammonium tungstate were placed in deionized water at a molar ratio of 1: (15-45) of the total amount of cobalt and tungsten to carbon in citric acid, stirred evenly and transferred to a hydrothermal reactor, sealed and heated at 180-200°C. o C undergoes a hydrothermal reaction, and after cooling and drying, a precursor is obtained, which is placed in a tube furnace and calcined in a mixed atmosphere of nitrogen and hydrogen to obtain a cobalt tungsten carbide catalyst.
[0009] In the cobalt tungsten carbide catalyst of this embodiment, the metal carbide is embedded in the in-situ formed carbon material, and can simultaneously catalyze carbon dioxide hydrogenation and carbon-carbon bond coupling reactions, and the product is ethanol. The present invention uses cobalt tungsten carbide as the catalytic active phase and the in-situ formed carbon material as the carrier. Compared with the existing metal alloy catalytic phase, the catalytic activity and ethanol selectivity are higher, and the catalytic product is ethanol, which is different from the principle of existing methanol catalysis.
[0010] Specific embodiment 2: This embodiment differs from specific embodiment 1 in that the solvent is a mixed solvent of N,N-dimethylformamide and water, and the volume ratio of N,N-dimethylformamide to water is 1:2 to 2:1.
[0011] Specific embodiment three: This embodiment differs from specific embodiment one or two in that after replacing the air in the reactor with carbon dioxide at room temperature, carbon dioxide is continuously introduced to 0.5-1.0 MPa, and then hydrogen is continuously introduced to a total pressure of 2.0-3.0 MPa.
[0012] Specific embodiment 4: This embodiment differs from specific embodiments 1 to 3 in that the pressure range is 2.0~6.0MPa and the temperature is 140~190 o C and stirred for 1-9 h.
[0013] Specific embodiment 5: This embodiment differs from the specific embodiment 4 in that the pressure range is 2.0~3.0MPa and the temperature is 160~190 o C and stirred for 5-8 h.
[0014] Specific embodiment 6: This embodiment differs from specific embodiments 1 to 5 in that in the preparation method of the cobalt tungsten carbide catalyst, the molar ratio of metal cobalt to tungsten in cobalt nitrate and ammonium tungstate is controlled to be 0.5-2.0:1.
[0015] Specific embodiment seven: This embodiment differs from specific embodiments one to six in that the preparation method of the cobalt tungsten carbide catalyst is 180-200 o C for hydrothermal reaction for 10-12h.
[0016] Specific embodiment eight: This embodiment differs from specific embodiments one to seven in that the cobalt tungsten carbide catalyst is calcined at a temperature of 600-1000° C. in a mixed atmosphere of nitrogen and hydrogen in the preparation method.
[0017] Specific embodiment 9: This embodiment differs from specific embodiment 8 in that the calcination treatment is performed for 2 to 4 hours in the preparation method of the cobalt tungsten carbide catalyst.
[0018] Example 1: This example uses a method for preparing ethanol by hydrogenating carbon dioxide catalyzed by cobalt tungsten carbide according to the following steps: 75 mg of cobalt carbide tungsten catalyst, 2.5 mL of N,N-dimethylformamide and 2.5 mL of water were placed in a 50 mL high-pressure reactor. After replacing the air in the reactor with carbon dioxide at room temperature, carbon dioxide was continuously introduced to 0.5 MPa, and then hydrogen was continuously introduced to a total pressure of 2.0 MPa. o C, stirred for 6.0 h, then cooled to room temperature, separated the cobalt tungsten carbide catalyst, and then the reaction solution was distilled under reduced pressure to separate ethanol; The preparation method of cobalt tungsten carbide catalyst A is as follows: 2.942g citric acid, 0.407g cobalt nitrate and 0.355g ammonium tungstate were placed in 20mL deionized water, stirred evenly and transferred to a hydrothermal reactor. o C was subjected to hydrothermal reaction for 12 hours, and a precursor was obtained after cooling and drying. The precursor was placed in a tube furnace and calcined at 700° C. for 3 hours in a mixed atmosphere of nitrogen and hydrogen to obtain cobalt tungsten carbide catalyst A.
[0019] The cobalt tungsten carbide catalyst A prepared in this example was characterized by XRD ( Figure 1 ), the results showed that the catalyst had characteristic diffraction peaks belonging to Co6W6C, WC and Co, indicating that the catalyst was composed of three substances: Co6W6C, WC and Co; its SEM photo ( Figure 2 ) shows that the catalyst prepared in this example has the morphology of spherical aggregates.
[0020] When the amount of catalyst A is 75 mg, at 180 o C. After 6.0 h of reaction at 2.0 MPa, the space-time yield of ethanol reached 17.1 mmol / g -1 h -1 , the selectivity of ethanol in organic products reached 99.2%.
[0021] Example 2: The difference between this example and example 1 is that the amount of catalyst A is 100 mg, and the temperature is 180 oC. The reaction was carried out under the condition of 2.0 MPa pressure for 2.0 h. The space-time yield of ethanol was 10.2 mmol / g -1 h -1 , the selectivity of ethanol in organic products is 96.1%.
[0022] Example 3: The difference between this example and example 1 is that the amount of catalyst A is 100 mg, and the temperature is 180 o The reaction was carried out at 3.0 h. The space-time yield of ethanol was 10.9 mmol / l. -1 h -1 , the selectivity of ethanol in organic products is 96.2%.
[0023] Example 4: The difference between this example and example 1 is that the amount of catalyst A is 100 mg, and the temperature is 180 o The reaction was carried out at 4.0 h under the same conditions as in Example 1. The space-time yield of ethanol was 13.6 mmol / l. -1 h -1 , the selectivity of ethanol in organic products is 96.4%.
[0024] Example 5: The difference between this example and example 1 is that the amount of catalyst A is 100 mg, and the temperature is 180 o The reaction was carried out at 5.0 h. The space-time yield of ethanol was 14.3 mmol / l. -1 h -1 , the selectivity of ethanol in organic matter is 99.5%.
[0025] Example 6: The difference between this example and example 1 is that the amount of catalyst A is 100 mg, and the temperature is 180 o The reaction was carried out at 40 °C for 6.0 h. The space-time yield of ethanol was 15.3 mmol / l. -1 h -1 , the selectivity of ethanol in organic products is 99.6%.
[0026] Example 7: The difference between this example and example 1 is that the amount of catalyst A is 100 mg, and the temperature is 180 o The reaction was carried out at 40 °C for 7.0 h. The space-time yield of ethanol was 11.4 mmol / l. -1 h -1 , the selectivity of ethanol in organic products is 96.3%.
[0027] Example 8: The difference between this example and example 1 is that the amount of catalyst A is 100 mg, and the temperature is 180 o The reaction was carried out at 40 °C for 8.0 h. The space-time yield of ethanol was 9.9 mmol / l. -1 h -1, the selectivity of ethanol in organic products is 99.0%.
[0028] Example 9: The difference between this example and example 1 is that the amount of catalyst A is 100 mg, and the temperature is 140 o The reaction was carried out at 40 °C for 6.0 h. The space-time yield of ethanol was 1.8 mmol / l. -1 h -1 , the selectivity of ethanol in organic products is 86.4%.
[0029] Example 10: The difference between this example and example 1 is that the amount of catalyst A is 100 mg, and the temperature is 150 o The reaction was carried out at 40 °C for 6.0 h. The space-time yield of ethanol was 3.7 mmol / l. -1 h -1 , the selectivity of ethanol in organic products is 92.3%.
[0030] Example 11: The difference between this example and example 1 is that the amount of catalyst A is 100 mg, and the temperature is 160 o The reaction was carried out at 40 °C for 6.0 h. The space-time yield of ethanol was 9.9 mmol / l. -1 h -1 , the selectivity of ethanol in organic products is 99.7%.
[0031] Example 12: This example is different from Example 1 in that the amount of catalyst A is 100 mg and the temperature is 170 o The reaction was carried out at 40 °C for 6.0 h. The space-time yield of ethanol was 12.3 mmol / l. -1 h -1 , the selectivity of ethanol in organic products is 99.4%.
[0032] Example 13: The difference between this example and example 1 is that the amount of catalyst A is 50 mg, and the temperature is 180 o The reaction was carried out at 40 °C for 6.0 h. The space-time yield of ethanol was 13.2 mmol / l. -1 h -1 , the selectivity of ethanol in organic products is 98.1%.
[0033] Example 14: The difference between this example and example 1 is that the amount of catalyst A is 125 mg, and the temperature is 180 o The reaction was carried out at 40 °C for 6.0 h. The space-time yield of ethanol was 7.1 mmol / l. -1 h -1 , the selectivity of ethanol in organic products is 99.0%.
[0034] Example 15: The difference between this example and example 1 is that the amount of catalyst A is 150 mg, and the temperature is 180o The reaction was carried out at 40 °C for 6.0 h. The space-time yield of ethanol was 6.8 mmol / l. -1 h -1 , the selectivity of ethanol in organic products is 98.9%.
[0035] Example 16: This example is different from Example 2 in that the catalyst used is 800 o Catalyst B was prepared by calcining C for 3 h. The space-time yield of ethanol was 14.2 mmol g -1 h -1 , the selectivity of ethanol in organic products is 98.9%.
[0036] Example 17: This example is different from Example 2 in that the catalyst used is 900 o Catalyst C was prepared by calcining C for 3 h. The space-time yield of ethanol was 11.7 mmol g -1 h -1 , the selectivity of ethanol in organic products is 99.6%.
[0037] Example 18: This example differs from Example 2 in that the catalyst used is a catalyst D prepared by mixing carbon, cobalt and tungsten in a precursor at a molar ratio of 15. The space-time yield of ethanol is 10.8 mmol / g. -1 h -1 , the selectivity of ethanol in organic products is 99.7%.
[0038] Example 19: This example differs from Example 2 in that the catalyst used is a catalyst E prepared with a molar ratio of carbon, metallic cobalt, and tungsten in the precursor of 45. The space-time yield of ethanol is 9.2 mmol / g. -1 h -1 , the selectivity of ethanol in organic products is 94.7%.
[0039] Table 1 summarizes the space-time yield of ethanol and the selectivity of ethanol in organic matter in Examples 1 to 19.
[0040] Table 1 Reaction results of carbon dioxide hydrogenation to ethanol *Ethanol selectivity refers to the percentage of ethanol in the organic product.
Claims
1. A method for preparing ethanol by hydrogenating carbon dioxide using cobalt tungsten carbide catalyst, characterized in that The method for preparing ethanol by hydrogenating carbon dioxide using cobalt tungsten carbide catalyst is achieved by the following steps: The cobalt carbide tungsten catalyst and solvent were placed in a reactor. After replacing the air in the reactor with carbon dioxide at room temperature, carbon dioxide was continuously introduced to 0.5-1.5 MPa. Then hydrogen was continuously introduced to a total pressure of 2.0-6.0 MPa. o C, and then cooled to room temperature to separate the cobalt tungsten carbide catalyst. The reaction solution was then distilled under reduced pressure to separate ethanol. The preparation method of the cobalt tungsten carbide catalyst is as follows: Citric acid, cobalt nitrate and ammonium tungstate were placed in deionized water at a molar ratio of 1: (15-45) of the total amount of cobalt and tungsten to carbon in citric acid, stirred evenly and transferred to a hydrothermal reactor, sealed and heated at 180-200°C. o C undergoes a hydrothermal reaction, and after cooling and drying, a precursor is obtained, which is placed in a tube furnace and calcined in a mixed atmosphere of nitrogen and hydrogen to obtain a cobalt tungsten carbide catalyst.
2. The method for preparing ethanol by hydrogenation of carbon dioxide catalyzed by cobalt tungsten carbide according to claim 1, characterized in that The solvent is a mixed solvent of N,N-dimethylformamide and water, and the volume ratio of N,N-dimethylformamide to water is 1:2-2:
1.
3. The method for preparing ethanol by hydrogenation of carbon dioxide catalyzed by cobalt tungsten carbide according to claim 1, characterized in that After replacing the air in the reactor with carbon dioxide at room temperature, continue to introduce carbon dioxide to 0.5-1.0 MPa, and then continue to introduce hydrogen until the total pressure reaches 2.0-3.0 MPa.
4. The method for preparing ethanol by hydrogenation of carbon dioxide catalyzed by cobalt tungsten carbide according to claim 1, characterized in that In the pressure range of 2.0~6.0MPa and temperature of 140~190 o C and stirred for 1-9 h.
5. The method for preparing ethanol by hydrogenation of carbon dioxide catalyzed by cobalt tungsten carbide according to claim 4, characterized in that In the pressure range of 2.0~3.0MPa and temperature of 160~190 o C and stirred for 5-8 h.
6. The method for preparing ethanol by hydrogenation of carbon dioxide catalyzed by cobalt tungsten carbide according to claim 1, characterized in that In the preparation method of the cobalt tungsten carbide catalyst, the molar ratio of metal cobalt to tungsten in cobalt nitrate and ammonium tungstate is controlled to be 0.5-2.0:
1.
7. The method for preparing ethanol by hydrogenation of carbon dioxide catalyzed by cobalt tungsten carbide according to claim 1, characterized in that In the preparation method of cobalt tungsten carbide catalyst, 180~200 o C for hydrothermal reaction for 10-12h.
8. The method for preparing ethanol by hydrogenation of carbon dioxide catalyzed by cobalt tungsten carbide according to claim 1, characterized in that In the preparation method of the cobalt tungsten carbide catalyst, a calcination treatment is performed at a temperature of 600 to 1000° C. in a mixed atmosphere of nitrogen and hydrogen.
9. The method for preparing ethanol by hydrogenation of carbon dioxide catalyzed by cobalt tungsten carbide according to claim 8, characterized in that The preparation method of the cobalt tungsten carbide catalyst is calcined for 2 to 4 hours.