A ternary catalyst for carbon dioxide hydrogenation to methanol and a preparation method thereof

Abstract

The application discloses a ternary catalyst for carbon dioxide hydrogenation to methanol and a preparation method thereof. The catalyst comprises three metal oxides, and the metal oxides are any three of copper oxide, zinc oxide, zirconium oxide and indium oxide. The mass fraction of each metal oxide in the catalyst is independently 10% to 50%. The multi-metal oxide solid solution catalyst is synthesized by a co-precipitation method, and the preparation method is simple and environment-friendly, and an organic solvent is not needed to be added. The composition and structure of the obtained catalyst are easy to control. Meanwhile, the carbon dioxide conversion rate and the selectivity of the target product methanol of the catalyst can be effectively improved by introducing citrate in the synthesis process.

Description

TECHNICAL FIELD

[0001] The application belongs to the field of carbon dioxide catalytic conversion catalysts, and particularly relates to a ternary catalyst for carbon dioxide hydrogenation to methanol and a preparation method thereof. BACKGROUND

[0002] With the rapid development of economic society, the concentration of greenhouse gases in the atmosphere is rising, among which the volume fraction of carbon dioxide has gradually increased from 280 ppm before industrialization to about 415 ppm, which poses a great threat to the earth's ecological system. At the same time, it is increasingly urgent to reduce the concentration of CO2 in the atmosphere. The existing technology can capture CO2 from industrial sources, but there is still a lack of effective ways to convert and reuse it. Since fossil resources are produced by natural carbon hydrogenation in the process of photosynthesis, it is possible to hydrogenate carbon dioxide as a carbon source to synthesize high-value-added products such as methanol, carbon monoxide, methane, dimethyl ether, etc. Nobel Prize winner Olah proposed the concept of "methanol economy", which puts CO2 hydrogenation to methanol and its derivative chemicals at the core position, and points out that carbon dioxide hydrogenation to methanol is a feasible way to realize green carbon cycle.

[0003] CO2 is a chemically inert molecule in thermodynamics, and usually requires the introduction of high-energy H2 to promote CO2 activation. The key to efficient carbon dioxide hydrogenation lies in the design of the catalyst. The commonly used catalyst systems include Cu-based catalysts, noble metal catalysts, In2O3-based catalysts and other new catalyst systems. However, they all have problems such as low activity and selectivity, poor stability or high cost. The activity of carbon dioxide hydrogenation can be effectively improved by improving the preparation method, adding additives, carrier regulation and other means, but it is still difficult to meet the needs of industrialization. SUMMARY

[0004] The purpose of the present application is to provide a ternary catalyst for carbon dioxide hydrogenation to methanol, which consists of three metal oxides, the metal oxides being any three of copper oxide, zinc oxide, zirconium oxide and indium oxide, and the mass fraction of each metal oxide in the catalyst being 10wt%-50wt%.

[0005] Another purpose of the present application is to provide a preparation method of the above-mentioned catalyst, characterized in that it comprises the following steps:

[0006] S1, mixing any three metal salts of copper salt, zinc salt, zirconium salt and indium salt uniformly in a solvent, adding sodium citrate and stirring thoroughly to obtain a mixed solution A;

[0007] Before the pH is adjusted by adding the alkali solution, an appropriate amount of sodium citrate is added. Due to the special nature of sodium citrate, the addition of sodium citrate here improves the conversion rate of carbon dioxide and the selectivity of methanol. In order to solve the problem that the acidic citric acid used in the prior art, the commonly used dispersants and stabilizers such as polyvinylpyrrolidone, polyethylene glycol, EDTA, etc., the sodium citrate can adjust the particle size of the catalyst to be more uniform, greatly improving the conversion rate of carbon dioxide and the selectivity of methanol.

[0008] S2, slowly adding an alkali solution to the above mixed solution A under a constant temperature T1 state, adjusting the solution pH to 8-11; preferably, adjusting the solution pH to 8-9;

[0009] S3, after sufficient reaction under a constant temperature T2 condition, centrifugation, washing, and drying;

[0010] The centrifugation refers to centrifugal separation of the solid-liquid mixture after sufficient reaction to obtain a solid product.

[0011] S4, after calcination in a hydrogen-containing atmosphere, slowly cooling to room temperature to obtain the ternary catalyst.

[0012] According to an embodiment of the present application, in step S1, the solvent is one or more of methanol, ethanol, glycerol, and water.

[0013] According to an embodiment of the present application, in step S1, the copper salt, zinc salt, zirconium salt, and indium salt are selected from one or more of their corresponding nitrate, hydrochloride, sulfate, and acetylacetone salt.

[0014] According to an embodiment of the present application, in step S1, the mass ratio of sodium citrate to the sum of the masses of the three metal salts is 1:20-1:5.

[0015] According to an embodiment of the present application, in step S2, the alkali solution is one or more of sodium carbonate solution, potassium carbonate solution, ammonium carbonate solution, sodium hydroxide solution, potassium hydroxide solution, and ammonia water, and the concentration of the alkali solution is 0.5-5.0 mol / L.

[0016] According to an embodiment of the present application, in step S2, the temperature T1 is 20-60°C, and preferably room temperature.

[0017] According to an embodiment of the present application, in step S3, the temperature T2 is 40-80°C, and preferably 60°C; and the reaction time is 12-48 hours, and preferably 24 hours.

[0018] According to an embodiment of the present application, in step S4, the hydrogen-containing atmosphere is pure hydrogen or a mixture of hydrogen and inert gas. The inert gas is one or more of hydrogen argon, hydrogen nitrogen, and hydrogen helium.

[0019] The CO2 conversion efficiency is improved by inducing oxygen defect formation through annealing treatment in a hydrogen atmosphere.

[0020] According to an embodiment of the present application, in step S4, the volume concentration of hydrogen in the hydrogen-containing mixed gas is 10%-20%, and the flow rate is 10-80 mL / min.

[0021] According to an embodiment of the present application, in step S4, the calcination treatment temperature is 200-400°C, preferably 250°C; the temperature rising rate is 2-5°C per minute, and the calcination time is 2-8 hours, preferably 2 hours.

[0022] Advantages

[0023] Compared with the prior art, the present application has the following advantages:

[0024] 1. The present application uses a co-precipitation method to synthesize a multi-metal oxide solid solution catalyst, and the preparation method is simple and environmentally friendly, without the need to add organic solvents, and the composition and structure of the obtained catalyst are easy to control. At the same time, by introducing citrate in the synthesis process, the carbon dioxide conversion rate and the selectivity of the target product methanol of the catalyst can be effectively improved.

[0025] 2. The present application further improves the CO2 conversion efficiency by inducing catalyst oxygen defect formation through annealing treatment in a hydrogen atmosphere.

[0026] 3. The catalyst of the present application uses non-noble metal raw materials, which is cheap, has a simple preparation process, good repeatability, and is easy to scale up production.

[0027] The present application will be further described below in conjunction with the accompanying drawings and specific embodiments. BRIEF DESCRIPTION OF DRAWINGS

[0028] Figure 1 is a transmission electron microscope (TEM) image of the ternary catalyst prepared in Example 1.

[0029] Figure 2 is an electron paramagnetic resonance spectrum (EPR) of the ternary catalyst prepared in Example 1.

[0030] Table 1 is the test results of the carbon dioxide catalytic reduction performance of the ternary catalyst for carbon dioxide hydrogenation to methanol. DETAILED DESCRIPTION

[0031] The technical solutions of the present application will be further described below according to specific embodiments. The protection scope of the present application is not limited to the following examples, and these examples are listed only for illustrative purposes and do not limit the present application in any way.

[0032] In the context of the present specification, any matter or item not mentioned, other than explicitly stated, applies directly the matters known in the art without any change being required. Moreover, any embodiment described herein can be freely combined with one or more other embodiments described herein, whereby the technical solutions or technical ideas formed thereby are considered as part of the original disclosure or original description of the present application and should not be considered as new matters or items not disclosed or anticipated herein, unless the combination is considered as obviously unreasonable by the person skilled in the art.

[0033] Carbon dioxide hydrogenation activity test

[0034] Carbon dioxide hydrogenation activity test was carried out by using fixed bed microreactor, the feed gas was H2, CO2 and Ar, the volume ratio was 72:24:4, the space velocity was 6000 mL.g -1 ·min -1 The catalyst loading was 0.5 g, and the quartz sand was 4.5 g, the reaction temperature was 200-300℃, and the sample was analyzed by chromatography equipped with hydrogen flame ion detection and thermal conductivity cell detector.

[0035] Example 1

[0036] 15 g of copper nitrate, 5 g of zinc nitrate, and 5 g of zirconium nitrate were mixed uniformly in 100 mL of water, then 2.0 g of sodium citrate was added, and after stirring, a mixture was obtained; a 0.5 mol / L sodium carbonate aqueous solution was prepared, and was slowly added to the above mixture at a speed of 2 drops per second under constant temperature at 60℃, and the solution pH was adjusted to 9.0; after sufficient reaction at 60℃ for 24 hours, centrifugation, washing, and drying, the sample was calcined at 250℃ for 2 hours under 10% H2 / Ar atmosphere (gas flow rate was 40 mL / min), and the temperature was raised at a rate of 2℃ per minute, and after cooling to room temperature, a ternary catalyst for carbon dioxide hydrogenation to methanol was obtained. Figure 1 is a TEM image of the ternary catalyst for carbon dioxide hydrogenation to methanol, and it can be seen that the sample has small particle size and good crystallinity. Figure 2 is an EPR spectrum of the sample, and the signal at g = 2.003 confirms the presence of oxygen defects in the sample. As shown in Table 1, in Example 1, at a reaction temperature of 260℃, the carbon dioxide conversion rate was 11.3%, the methanol selectivity was 71.6%, the carbon monoxide selectivity was 27.4%, and the methane selectivity was 1.0%.

[0037] Example 2

[0038] Example 2: 10 g of zinc nitrate, 5 g of zirconium nitrate and 5 g of indium nitrate were mixed uniformly in 100 mL of water, then 3.0 g of sodium citrate was added, and after stirring, a mixture was obtained; a 1.0 mol / L aqueous solution of sodium carbonate was prepared, and was slowly added to the above mixture at a rate of 2 drops per second under the condition of constant temperature at 40°C, and the pH of the solution was adjusted to 8.0; after fully reacting at 60°C for 24 hours, centrifugation, washing, drying, and calcination treatment at 250°C under the condition of 20% H2 / Ar atmosphere (gas flow rate was 40 mL / min) for 2 hours with a temperature rising rate of 2°C per minute, a ternary catalyst for the hydrogenation of carbon dioxide to produce methanol was obtained after cooling to room temperature. As shown in Table 1, in Example 2, when the reaction temperature was 260°C, the carbon dioxide conversion rate was 10.9%, the methanol selectivity was 68.4%, the carbon monoxide selectivity was 31.1%, and the methane selectivity was 0.5%.

[0039] Example 3:

[0040] 10 g of copper nitrate, 5 g of zinc nitrate and 5 g of indium nitrate were mixed uniformly in 100 mL of water, then 3.0 g of sodium citrate was added, and after stirring, a mixture was obtained; a 1.0 mol / L aqueous solution of sodium carbonate was prepared, and was slowly added to the above mixture at a rate of 2 drops per second under the condition of constant temperature at 60°C, and the pH of the solution was adjusted to 8.0; after fully reacting at 60°C for 24 hours, centrifugation, washing, drying, and calcination treatment at 250°C under the condition of 10% H2 / Ar atmosphere (gas flow rate was 60 mL / min) for 2 hours with a temperature rising rate of 2°C per minute, a ternary catalyst for the hydrogenation of carbon dioxide to produce methanol was obtained after cooling to room temperature. As shown in Table 1, in Example 3, when the reaction temperature was 260°C, the carbon dioxide conversion rate was 9.6%, the methanol selectivity was 68.1%, the carbon monoxide selectivity was 31.8%, and the methane selectivity was 0.1%.

[0041] Example 4:

[0042] 5 g of zinc nitrate, 5 g of zirconium nitrate and 10 g of indium nitrate were mixed uniformly in 100 mL of water, then 3.0 g of sodium citrate was added, and after stirring, a mixture was obtained; a 1.0 mol / L aqueous solution of sodium carbonate was prepared, and was slowly added to the above mixture at a rate of 2 drops per second under the condition of constant temperature at 20°C, and the pH of the solution was adjusted to 9.0; after fully reacting at 60°C for 24 hours, centrifugation, washing, drying, and calcination treatment at 250°C under the condition of 10% H2 / Ar atmosphere (gas flow rate was 40 mL / min) for 2 hours with a temperature rising rate of 2°C per minute, a ternary catalyst for the hydrogenation of carbon dioxide to produce methanol was obtained after cooling to room temperature. As shown in Table 1, in Example 4, when the reaction temperature was 260°C, the carbon dioxide conversion rate was 15.4%, the methanol selectivity was 64.9%, the carbon monoxide selectivity was 34.6%, and the methane selectivity was 0.5%.

[0043] Example 5

[0044] 10 g of copper chloride, 5 g of zinc chloride and 5 g of indium nitrate were mixed uniformly in 100 mL of water, and then 1.5 g of sodium citrate was added, and after stirring, a mixture was obtained; a 0.5 mol / L aqueous solution of sodium hydroxide was prepared, and was slowly added to the above mixture at a rate of 2 drops per second under constant temperature conditions at 50°C, and the pH of the solution was adjusted to 9.0; after fully reacting at 80°C for 48 hours, centrifugation, washing, drying, and calcination treatment at 300°C under a 20% H2 / Ar atmosphere (gas flow rate was 40 mL / min) for 2 hours at a temperature increase rate of 2°C per minute, the ternary catalyst for the hydrogenation of carbon dioxide to methanol was obtained after cooling to room temperature. As shown in Table 1, in Example 5, at a reaction temperature of 260°C, the carbon dioxide conversion rate was 16.3%, the methanol selectivity was 73.2%, the carbon monoxide selectivity was 25.4%, and the methane selectivity was 1.4%.

[0045] Example 6

[0046] 10 g of copper nitrate, 10 g of zinc nitrate, and 10 g of zirconium nitrate were mixed uniformly in 100 mL of water, and then 2.5 g of sodium citrate was added, and after stirring, a mixture was obtained; a 0.5 mol / L aqueous solution of potassium hydroxide was prepared, and was slowly added to the above mixture at a rate of 2 drops per second under constant temperature conditions at 60°C, and the pH of the solution was adjusted to 8.0; after fully reacting at 60°C for 24 hours, centrifugation, washing, drying, and calcination treatment at 300°C under a 10% H2 / Ar atmosphere (gas flow rate was 40 mL / min) for 4 hours at a temperature increase rate of 2°C per minute, the ternary catalyst for the hydrogenation of carbon dioxide to methanol was obtained after cooling to room temperature. As shown in Table 1, in Example 6, at a reaction temperature of 260°C, the carbon dioxide conversion rate was 12.1%, the methanol selectivity was 79.1%, the carbon monoxide selectivity was 20.0%, and the methane selectivity was 0.9%.

[0047] Example 7

[0048] 10 g of copper nitrate, 10 g of zirconium nitrate and 5 g of indium nitrate were mixed uniformly in 100 mL of water, and then 3.0 g of sodium citrate was added, and after stirring, a mixture was obtained; a 1.0 mol / L sodium carbonate aqueous solution was prepared, and was slowly added to the above mixture at a speed of 2 drops per second under the condition of 40°C constant temperature, and the solution pH was adjusted to 8.0; after fully reacting at 60°C for 24 hours, centrifugation, washing, drying, and calcination treatment at 250°C under a 20% H2 / Ar atmosphere (gas flow rate was 40 mL / min) for 2 hours with a temperature rising rate of 2°C per minute, the ternary catalyst for carbon dioxide hydrogenation to methanol was obtained after cooling to room temperature. As shown in Table 1, in Example 7, when the reaction temperature was 260°C, the carbon dioxide conversion rate was 17.3%, the methanol selectivity was 65.3%, the carbon monoxide selectivity was 34.2%, and the methane selectivity was 0.5%.

[0049] In addition, through the design of comparative experiments, it is proved that the intermetallic synergistic effect and the existence of oxygen defects play an important role in improving the carbon dioxide hydrogenation activity and methanol selectivity, and the specific scheme is as follows:

[0050] Comparative Example 1

[0051] 15 g of copper nitrate was mixed uniformly in 100 mL of water, and then 2.0 g of sodium citrate was added, and after stirring, a mixture was obtained; a 0.5 mol / L sodium carbonate aqueous solution was prepared, and was slowly added to the above mixture at a speed of 2 drops per second under the condition of 60°C constant temperature, and the solution pH was adjusted to 9.0; after fully reacting at 60°C for 24 hours, centrifugation, washing, drying, and calcination treatment at 250°C under a 10% H2 / Ar atmosphere (gas flow rate was 40 mL / min) for 2 hours with a temperature rising rate of 2°C per minute, Comparative Example 1 was obtained after cooling to room temperature. As shown in Table 1, in Comparative Example 1, when the reaction temperature was 260°C, the carbon dioxide conversion rate was 5.6%, the methanol selectivity was 45.0%, the carbon monoxide selectivity was 51.4%, and the methane selectivity was 3.6%.

[0052] Comparative Example 2

[0053] 15 g of copper nitrate, 5 g of zinc nitrate and 5 g of zirconium nitrate were mixed uniformly in 100 mL of water; a 0.5 mol / L sodium carbonate aqueous solution was prepared, and was slowly added to the above mixture at a speed of 2 drops per second under the condition of 50°C constant temperature, and the solution pH was adjusted to 9.0; after fully reacting at 60°C for 24 hours, centrifugation, washing, drying, and calcination treatment at 250°C under a 10% H2 / Ar atmosphere (gas flow rate was 40 mL / min) for 2 hours with a temperature rising rate of 2°C per minute, Comparative Example 3 was obtained after cooling to room temperature. As shown in Table 1,

[0054] In Comparative Example 2, the carbon dioxide conversion was 1.6%, the methanol selectivity was 45.0%, the carbon monoxide selectivity was 46.2%, and the methane selectivity was 8.8% at a reaction temperature of 260°C.

[0055] Comparative Example 3

[0056] Comparative Example 4

[0057] Comparative Example 5

[0058] Comparative Example 6

[0059] Comparative Example 7

[0060] Comparative Example 8

[0061] Comparative Example 9

[0062] Comparative Example 10

[0063] Comparative Example 11

[0064] The other conditions are the same as in Example 1, except that sodium citrate is replaced by citric acid. As shown in Table 1, in Comparative Example 7, at a reaction temperature of 260°C, the carbon dioxide conversion is 3.2%, the methanol selectivity is 46.4%, the carbon monoxide selectivity is 37.1%, and the methane selectivity is 16.5%.

[0065] Comparative Example 8

[0066] The other conditions are the same as in Example 1, except that sodium citrate is replaced by polyvinylpyrrolidone. As shown in Table 1, in Comparative Example 8, at a reaction temperature of 260°C, the carbon dioxide conversion is 4.2%, the methanol selectivity is 48.2%, the carbon monoxide selectivity is 40.1%, and the methane selectivity is 11.7%.

[0067] Comparative Example 9

[0068] The other conditions are the same as in Example 1, except that sodium citrate is replaced by polyethylene glycol. As shown in Table 1, in Comparative Example 9, at a reaction temperature of 260°C, the carbon dioxide conversion is 2.9%, the methanol selectivity is 51.3%, the carbon monoxide selectivity is 38.6%, and the methane selectivity is 10.1%.

[0069] Table 1 is the test result of carbon dioxide catalytic reduction performance of ternary catalysts for carbon dioxide hydrogenation to methanol.

[0070] Table 1

[0071]

[0072]

Claims

1. Use of a three-way catalyst in the hydrogenation of carbon dioxide to methanol, characterized in that, The composition of the catalyst comprises three metal oxides, the three metal oxides being any three of copper oxide, zinc oxide, zirconium oxide, and indium oxide; the mass fraction of each metal oxide in the catalyst is independently 10%-50%; The preparation method of the catalyst comprises the following steps: S1. Optionally, mix three metal salts of copper salt, zinc salt, zirconium salt, and indium salt in a solvent, add sodium citrate, and fully stir to obtain a mixed solution A; S2. Add an alkali solution to the mixed solution A at a temperature T1, and adjust the pH of the solution to 8-11; S3. After fully reacting at a temperature T2, centrifuge, wash, and dry; S4. After calcination in a hydrogen-containing atmosphere, cool to room temperature to obtain the ternary catalyst.

2. Use according to claim 1, characterized in that, In step S2, the pH of the solution is adjusted to 8-9.

3. Use according to claim 1, characterized in that, In step S1, the solvent is one or more of methanol, ethanol, glycerol, and water.

4. Use according to claim 1, characterized in that, In step S1, the copper salt, zinc salt, zirconium salt, and indium salt are selected from one or more of their corresponding nitrate, hydrochloride, sulfate, and acetylacetone salt.

5. The use according to claim 1, characterized in that, In step S1, the mass ratio of sodium citrate to the mass sum of the three metal salts is 1:20-1:

5.

6. Use according to claim 1, characterized in that, In step S2, the alkali solution is one or more of sodium carbonate solution, potassium carbonate solution, ammonium carbonate solution, sodium hydroxide solution, potassium hydroxide solution, and ammonia water, and the concentration of the alkali solution is 0.5-5.0 mol / L.

7. Use according to claim 1, characterized in that, In step S2, the temperature T1 is 20-60℃.

8. The use according to claim 1, characterized in that, In step S3, the temperature T2 is 40-80℃, and the reaction time is 12-48 hours.

9. Use according to claim 8, characterized in that, In step S3, the temperature T2 is 60℃, and the reaction time is 24 hours.

10. The use according to claim 1, characterized in that, In step S4, the hydrogen-containing atmosphere is pure hydrogen, hydrogen-nitrogen, or a mixture of hydrogen and inert gas.

11. Use according to claim 10, characterized in that, The volume concentration of hydrogen in the mixture of hydrogen and inert gas is 10%-20%, and the flow rate is 10-80 mL / min.

12. The use according to claim 10, characterized in that, The mixture of hydrogen and inert gas is one or more of hydrogen-argon and hydrogen-helium.

13. The use according to claim 1, characterized in that, In step S4, the calcination temperature is 200-400℃, and the calcination time is 2-8 hours.

14. Use according to claim 13, characterized in that, In step S4, the calcination temperature is 250℃, and the calcination time is 2 hours.

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