CN117085689A - A copper-based catalyst for hydrogenation of carbon dioxide to methylate and preparation method thereof - Google Patents

Abstract

The invention discloses a copper-based catalyst for preparing methanol by hydrogenation of carbon dioxide and a preparation method thereof, wherein the preparation method takes a copper source, a zinc source and a zirconium source or an aluminum source as raw materials, sodium carbonate as a precipitator and a soluble organic compound as a carbon source, and adopts coprecipitation-in-situ carbonization-reduction to obtain a carbon-modified copper-based catalyst, and the components of the catalyst comprise Cu, znO, zrO ₂ Or Al ₂ O ₃ And C, C is uniformly dispersed on the surface of the catalyst, is tightly combined with the active component copper, promotes copper dispersion and obtains high CO ₂ Conversion and methanol selectivity; meanwhile, the catalyst plays a role in limiting copper species and enhancing the hydrophobicity of the surface of the catalyst, is favorable for timely desorbing water generated by reaction, maintains stable copper valence state, and obtains high heat-resistant stability, and CO before and after heat resistance ₂ The conversion and the methanol selectivity are almost unchanged. The catalyst is used for the reaction of synthesizing methanol by carbon dioxide hydrogenation, the byproduct is only CO, and the liquid phase product only contains methanol and water, so that the catalyst is easy to separate.

Description

A copper-based catalyst for carbon dioxide hydrogenation to produce methoxide and its preparation method

Technical field

The invention belongs to the technical field of catalyst preparation, and is specifically a copper-based catalyst for hydrogenation of carbon dioxide to methylate and a preparation method thereof.

Background technique

With the development and improvement of human industrial civilization, the use of fossil fuels continues to increase, and carbon dioxide emissions increase year by year. High emissions of carbon dioxide will accelerate global warming, seawater acidification, land desertification and other problems. Therefore, carbon dioxide emission reduction and resource utilization have become a research hotspot in current society.

Converting _CO2 into a series of chemicals such as methanol, dimethyl ether, methane, etc. through catalytic hydrogenation technology is an effective means of resource utilization of _CO2 . Among various hydrogenation products, the formation of methanol is the first choice, because methanol is a clean energy that can greatly improve a country's energy depletion crisis. It is also a good carrier of hydrogen energy. Replacing fossil fuels with fuels as energy storage media can improve the energy crisis in the oil and gas era and alleviate the pressure of global climate warming. This has become one of the most promising research areas for the rational utilization of CO ₂ in recent years. Based on the above advantages, hydrogenation of carbon dioxide to methanol has important environmental potential and economic value.

Currently, copper-based catalysts used for the hydrogenation of carbon dioxide to methanol mainly suffer from problems such as low carbon dioxide conversion rate, low methanol selectivity, and poor catalyst stability. Researchers have achieved some effects by adding metal additives such as Ga [Appl. Catal. BEnviron, 2013, 142-143, 241-248]., In [Appl. Catal. A, 2020, 605, 117805], etc. Methanol selection The performance has improved, but the stability has not improved significantly. Some researchers have added carbon materials to improve the stability of the catalyst. Because carbon materials are hydrophobic, they can effectively improve the impact of water generated during the reaction on active components and prevent the growth and deactivation of ZnO. However, currently reported carbon materials Material-modified copper-based catalysts are directly added to the copper-based catalyst with carbon nanotubes [Catal. Today, 2018, 307, 212-223], graphene [Chem. Eng. J, 2018, 334, 1781-1791]. Method Since carbon is insoluble, the prepared catalyst has problems such as uneven mixing of carbon and other components in the copper-based catalyst and difficulty in repeatability.

In response to the above problems, the present invention uses soluble organic compounds as carbon sources and prepares uniformly mixed carbon-modified copper-based catalysts through in-situ carbonization, which can improve methanol selectivity and the heat resistance stability of the catalyst.

Contents of the invention

Based on the problems existing in copper-based catalysts currently used for hydrogenating carbon dioxide to produce methanol, the purpose of the present invention is to provide a copper-based catalyst for hydrogenating carbon dioxide to produce methanol and a preparation method thereof. The present invention uses copper salts, zinc salts, zirconium salts or Aluminum salt is used as raw material, carbonate is used as precipitant, and carbon source is added as auxiliary agent. The prepared copper-based catalyst for carbon dioxide hydrogenation to methanol has the characteristics of high CO ₂ conversion rate, methanol selectivity, and high stability.

The invention discloses a copper-based catalyst for hydrogenating carbon dioxide to produce methoxide. The components of the catalyst include Cu, ZnO, ZrO ₂ or Al ₂ O ₃ and auxiliary agent C. The catalyst contains Cu, ZnO, ZrO ₂ or Al ₂ O ₃ Evenly dispersed, the additive C is evenly dispersed on the surface of the catalyst, tightly combined with the active component copper species, promoting the dispersion of copper species, and at the same time, it plays a certain limiting role in the copper species, and enhances the hydrophobicity of the catalyst surface, so that the copper species The price remains stable.

Further, the present invention also limits the molar percentage of each component in the catalyst to Cu being 20-70%, Zn being 10-60%, Zr or Al being 1-20%, and C being 1-30%.

Further, the present invention also limits the preparation method of a copper-based catalyst for hydrogenation of carbon dioxide to methoxide, using a copper source, a zinc source, a zirconium source or an aluminum source as raw materials, using sodium carbonate as a precipitant, and using soluble organic compounds as a carbon source, The carbon-modified copper-based catalyst is obtained by coprecipitation-in-situ carbonization-reduction, which specifically includes the following steps:

1) According to the input ratio, dissolve the copper source, zinc source, zirconium source or aluminum source in water to prepare a metal salt solution; dissolve sodium carbonate in water to prepare a sodium carbonate solution, add the carbon source to the water and stir ultrasonically to obtain a solution containing the carbon source;

2) Co-precipitate the metal salt solution and the sodium carbonate solution into the solution containing the carbon source under stirring, and age under stirring. After the precipitation is filtered and washed, the catalyst precursor is obtained;

3) After drying the catalyst precursor obtained in step 2), it is roasted in an inert atmosphere for in-situ carbonization, and then the catalyst is reduced by H ₂ /N ₂ to obtain a carbon-modified copper-based catalyst.

Further, the present invention also limits the carbon source to be one or more of β-cyclodextrin, polyethylene glycol (PEG), ethylene glycol (EG), glucose or soluble starch.

Further, the present invention also limits the copper source to be copper nitrate or copper acetate; the zinc source to be zinc nitrate or zinc acetate; the zirconium source to be zirconium nitrate or zirconium oxynitrate; and the aluminum source to be aluminum nitrate or pseudo-boehmite.

Further, the present invention also limits the molar ratio of the total molar amount of copper source, zinc source, zirconium source or aluminum source to carbon to be 1:0.01-0.3.

Further, the present invention also defines the specific operation of step 2) as follows: at 10-80°C, the metal salt solution and the sodium carbonate solution are titrated in parallel flow into the solution containing the carbon source in step 1), fully stirred and co-precipitated, and the pH is maintained. =7-10, after precipitation, stir and age at 40-100°C for 0.5-24h. The precipitation is washed with deionized water until no sodium ions are detected, and the catalyst precursor is obtained.

Further, the present invention also limits the catalyst precursor drying conditions in step 3) to: drying at 60-160°C for 10-15h; the roasting conditions: roasting at 300-500°C for 3-6h in a nitrogen or argon atmosphere.

In the copper-based catalyst for hydrogenating carbon dioxide to produce methanol, the carbon dioxide feed gas composition is 10-30 vol.% CO ₂ , 30-90 vol. % H ₂ and N ₂ mixed gas as balance gas when hydrogenating carbon dioxide to produce methanol. , where the volume ratio of CO ₂ to H ₂ is approximately 1:3, using a fixed bed reactor, operating at a pressure of 2 to 10MPa, a temperature of 180 to 280°C, and a space velocity of 6000 to 30000mL g _cat ^-1 h ^-1 _CO2 hydrogenation reaction to synthesize methanol.

By adopting the above technology, compared with the existing technology, the beneficial effects of the present invention are as follows:

1) The present invention uses copper salt, zinc salt, zirconium salt or aluminum salt as raw material, carbonate as precipitant, soluble carbon source as auxiliary agent, and adopts co-precipitation-in-situ carbonization method to in-situ on the copper-based catalyst. Carbon is generated, and a carbon-modified copper-based catalyst is synthesized. In-situ carbonization generates carbon to modify the catalyst, which can fully mix the additives with the copper species and create a stronger interaction;

2) The carbon component in the catalyst of the present invention plays a certain limiting role on copper species, enhances the hydrophobicity of the catalyst, improves the selectivity of the catalyst in the hydrogenation of carbon dioxide to methanol and the heat resistance stability of the catalyst, and its methanol The selectivity is as high as 95%, and the CO ₂ conversion rate and methanol selectivity are almost unchanged after heat resistance at 350°C;

3) The catalyst of the present invention is used in the hydrogenation of carbon dioxide to synthesize methanol. The reaction by-product is only CO, and the liquid phase product only contains methanol and water, which is easy to separate.

Description of the drawings

Figure 1 is an EDS-mapping diagram of the copper-based catalyst β-CZZ prepared in Example 1;

Figure 2 is a measurement chart of the contact angle of the copper-based catalyst prepared in Example 1 and Comparative Example 1;

Figure 3 is a schematic structural diagram of the copper-based catalyst prepared in Example 1.

Detailed ways

The present invention will be further described below with reference to specific embodiments, but the scope of protection of the present invention is not limited to the described scope.

Example 1

Accurately weigh Cu(NO ₃ ) ₂ ·3H ₂ O 14.50g, Zn(NO ₃ ) ₂ ·6H _{2 O} 8.93g, and Zr(NO ₃ ) ₄ · according to the Cu, Zn, Zr molar ratio of 6:3:1. Dissolve 4.29g of 5H ₂ O in 100 mL of deionized water to prepare a metal salt solution 1 with a total metal ion concentration of 1 mol L ^-1 ; accurately weigh 15.90 g of Na ₂ CO ₃ and dissolve it in 150 mL of deionized water to prepare a metal salt solution of 1 mol L ^- Alkali solution 2 of ¹ ; accurately weigh 0.14g of β-cyclodextrin and add it to 100 mL of deionized water to prepare a carbon-containing source solution 3; co-precipitate the metal salt solution 1 and alkali solution 2 into a carbon-containing solution under stirring at 70°C. In source solution 3, the precipitation process requires sufficient stirring, maintaining pH = 7, and aging at 70°C for 2 hours. The precipitate is washed with deionized water until no sodium ions are detected, dried at 110°C for 12 hours, and roasted at 400°C for 4 hours under _N2 atmosphere. , and then 20% H ₂ /N ₂ was introduced to reduce the catalyst (30 mL min ^-1 ) to obtain a carbon-modified copper-based catalyst with a total molar ratio of copper source, zinc source, and zirconium source to carbon molar ratio of 1:0.05, named is β-CZZ. The schematic structural diagram of the copper-based catalyst is shown in Figure 3.

Example 2

Accurately weigh Cu(NO ₃ ) ₂ ·3H ₂ O 14.50g, Zn(NO ₃ ) ₂ ·6H _{2 O} 8.93g, and Zr(NO ₃ ) ₄ · according to the Cu, Zn, Zr molar ratio of 6:3:1. Dissolve 4.29g of 5H ₂ O in 100 mL of deionized water to prepare a metal salt solution 1 with a total metal ion concentration of 1 mol L ^-1 ; accurately weigh 15.90 g of Na ₂ CO ₃ and dissolve it in 150 mL of deionized water to prepare a metal salt solution of 1 mol L ^- Alkali solution 2 of ¹ ; accurately weigh 0.027g of β-cyclodextrin and add it to 100 mL of deionized water to prepare a carbon-containing source solution 3; co-precipitate the metal salt solution 1 and alkali solution 2 into the carbon-containing solution under stirring at 70°C. In source solution 3, the precipitation process requires sufficient stirring to maintain pH = 7. After precipitation, it is aged at 70°C for 2 hours. The precipitation is washed with deionized water until no sodium ions are detected, dried at 110°C for 12 hours, and 400 in a _N2 atmosphere. Calculate at ℃ for 4 hours, and then introduce 20% H ₂ /N ₂ to reduce the catalyst (30mL min ^-1 ) to obtain a carbon-modified copper base with a total molar ratio of copper source, zinc source, and zirconium source to carbon molar ratio of 1:0.01. The catalyst was named β-CZZ-1.

Example 3

Accurately weigh Cu(NO ₃ ) ₂ ·3H ₂ O 14.50g, Zn(NO ₃ ) ₂ ·6H _{2 O} 8.93g, and Zr(NO ₃ ) ₄ · according to the Cu, Zn, Zr molar ratio of 6:3:1. Dissolve 4.29g of 5H ₂ O in 100 mL of deionized water to prepare a metal salt solution 1 with a total metal ion concentration of 1 mol L ^-1 ; accurately weigh 15.90 g of Na ₂ CO ₃ and dissolve it in 150 mL of deionized water to prepare a metal salt solution of 1 mol L ^- Alkali solution 2 of ¹ ; accurately weigh 0.27g of β-cyclodextrin and add it to 100 mL of deionized water to prepare a carbon-containing source solution 3; co-precipitate the metal salt solution 1 and alkali solution 2 into the carbon-containing solution under stirring at 70°C. In source solution 3, the precipitation process requires sufficient stirring, maintaining pH = 7, and aging at 70°C for 2 hours. The precipitate is washed with deionized water until no sodium ions are detected, dried at 110°C for 12 hours, and roasted at 400°C for 4 hours under _N2 atmosphere. , and then introduce 20% H ₂ /N ₂ to reduce the catalyst (30mL min ^-1 ), and obtain a carbon-modified copper-based catalyst with a total molar ratio of copper source, zinc source, and zirconium source to carbon molar ratio of 1:0.1, named β-CZZ-10.

Example 4

Accurately weigh Cu(NO ₃ ) ₂ ·3H ₂ O 14.50g, Zn(NO ₃ ) ₂ ·6H _{2 O} 8.93g, and Zr(NO ₃ ) ₄ · according to the Cu, Zn, Zr molar ratio of 6:3:1. Dissolve 4.29g of 5H ₂ O in 100 mL of deionized water to prepare a metal salt solution 1 with a total metal ion concentration of 1 mol L ^-1 ; accurately weigh 15.90 g of Na ₂ CO ₃ and dissolve it in 150 mL of deionized water to prepare a metal salt solution of 1 mol L ^- Alkali solution 2 of ¹ ; accurately weigh 0.81g of β-cyclodextrin and add it to 100 mL of deionized water to prepare a carbon-containing source solution 3; co-precipitate the metal salt solution 1 and alkali solution 2 into the carbon-containing solution under stirring at 70°C. In source solution 3, the precipitation process requires sufficient stirring, maintaining pH = 7, and aging at 70°C for 2 hours. The precipitate is washed with deionized water until no sodium ions are detected, dried at 110°C for 12 hours, and roasted at 400°C for 4 hours under _N2 atmosphere. , and then 20% H ₂ /N ₂ was introduced to reduce the catalyst (30mL min ^-1 ) to obtain a carbon-modified copper-based catalyst with a total molar ratio of copper source, zinc source, and zirconium source to carbon molar ratio of 1:0.3, named is β-CZZ-30.

Example 5

Accurately weigh Cu(NO ₃ ) ₂ ·3H ₂ O 14.50g, Zn(NO ₃ ) ₂ ·6H ₂ O8.93g, and Al(NO ₃ ) ₃ · according to the Cu, Zn, and Al molar ratio of 6:3:1. Dissolve 3.75g of 9H ₂ O in 100 mL of deionized water to prepare a metal salt solution 1 with a total metal ion concentration of 1 mol L ^-1 ; accurately weigh 15.90 g of Na ₂ CO ₃ and dissolve it in 150 mL of deionized water to prepare a metal salt solution of 1 mol L ^- Alkaline solution 2 of ¹ ; accurately weigh 0.14g of β-cyclodextrin and add it to 100 mL of deionized water to prepare a carbon source solution 3. Co-precipitate the metal salt solution 1 and the alkali solution 2 into the carbon source solution 3 under stirring at 70°C. The precipitation process requires sufficient stirring to maintain pH = 7, and aging at 70°C for 2 hours. The precipitate is washed with deionized water until there is no sodium ion. Until detection, dry at 110°C for 12h, calcined at 400°C for 4h in _N2 atmosphere, and then pass in 20% _H2 / _N2 to reduce the catalyst (30mL min ^-1 ) to obtain copper source, zinc source, and aluminum The carbon-modified copper-based catalyst with a total molar source to carbon molar ratio of 1:0.05 was named β-CZA.

Example 6

Accurately weigh Cu(NO ₃ ) ₂ ·3H ₂ O 14.50g, Zn(NO ₃ ) ₂ ·6H _{2 O} 8.93g, and Zr(NO ₃ ) ₄ · according to the Cu, Zn, Zr molar ratio of 6:3:1. Dissolve 4.29g of 5H ₂ O in 100 mL of deionized water to prepare solution 1 with a total metal ion concentration of 1 mol L ^-1 . Accurately weigh 15.90g of Na ₂ CO ₃ and dissolve it in 150 mL of deionized water to prepare 1 mol L ^-1 of alkali solution 2. Accurately weigh 0.11g of PEG-40000 and add it to 100 mL of deionized water to prepare carbon source solution 3. Co-precipitate the metal salt solution 1 and the alkali solution 2 into the carbon source solution 3 under stirring at 70°C. The precipitation process requires sufficient stirring to maintain pH = 7, and aging at 70°C for 2 hours. The precipitate is washed with deionized water until there is no sodium ion. Until detection, dry at 110°C for 12h, calcine at 400°C for 4h in _N2 atmosphere, and then pass in 20% _H2 / _N2 to reduce the catalyst (30mL min ^-1 ) to obtain copper source, zinc source, and zirconium. The carbon-modified copper-based catalyst with a total molar source to carbon molar ratio of 1:0.05 was named PEG-CZZ.

Example 7

Accurately weigh Cu(NO ₃ ) ₂ ·3H ₂ O 14.50g, Zn(NO ₃ ) ₂ ·6H _{2 O} 8.93g, and Zr(NO ₃ ) ₄ · according to the Cu, Zn, Zr molar ratio of 6:3:1. Dissolve 4.29g of 5H ₂ O in 100 mL of deionized water to prepare solution 1 with a total metal ion concentration of 1 mol L ^-1 . Accurately weigh 15.90g of Na ₂ CO ₃ and dissolve it in 150 mL of deionized water to prepare 1 mol L ^-1 of alkali solution 2. Accurately weigh 0.16g of ethylene glycol and add it to 100mL of deionized water to prepare carbon source solution 3. Co-precipitate the metal salt solution 1 and the alkali solution 2 into the carbon source solution 3 under stirring at 70°C. The precipitation process requires sufficient stirring to maintain pH = 7, and aging at 70°C for 2 hours. The precipitate is washed with deionized water until there is no sodium ion. Until detection, dry at 110℃ for 12h, calcine at 400℃ for 4h in _N2 atmosphere, and then pass in 20% _H2 / _N2 to reduce the catalyst (30mLmin ^-1 ) to obtain copper source, zinc source and zirconium source. The carbon-modified copper-based catalyst with a total molar to carbon molar ratio of 1:0.05 was named EG-CZZ.

Example 8

Accurately weigh Cu(NO ₃ ) ₂ ·3H ₂ O 14.50g, Zn(NO ₃ ) ₂ ·6H _{2 O} 8.93g, and Zr(NO ₃ ) ₄ · according to the Cu, Zn, Zr molar ratio of 6:3:1. Dissolve 4.29g of 5H ₂ O in 100 mL of deionized water to prepare solution 1 with a total metal ion concentration of 1 mol L ^-1 . Accurately weigh 15.90g of Na ₂ CO ₃ and dissolve it in 150 mL of deionized water to prepare 1 mol L ^-1 of alkali solution 2. Accurately weigh 0.14g of soluble starch and add it to 100mL of deionized water to prepare carbon source solution 3. Co-precipitate the metal salt solution 1 and the alkali solution 2 into the carbon source solution 3 under stirring at 70°C. The precipitation process requires sufficient stirring to maintain pH = 7, and aging at 70°C for 2 hours. The precipitate is washed with deionized water until there is no sodium ion. Until detection, dry at 110°C for 12h, calcine at 400°C for 4h in _N2 atmosphere, and then pass in 20% _H2 / _N2 to reduce the catalyst (30mL min ^-1 ) to obtain copper source, zinc source, and zirconium. The carbon-modified copper-based catalyst with a total molar source to carbon molar ratio of 1:0.05 was named S-CZZ.

Example 9

Accurately weigh Cu(NO ₃ ) ₂ ·3H ₂ O 14.50g, Zn(NO ₃ ) ₂ ·6H _{2 O} 8.93g, and Zr(NO ₃ ) ₄ · according to the Cu, Zn, Zr molar ratio of 6:3:1. Dissolve 4.29g of 5H ₂ O in 100 mL of deionized water to prepare solution 1 with a total metal ion concentration of 1 mol L ^-1 . Accurately weigh 15.90g of Na ₂ CO ₃ and dissolve it in 150 mL of deionized water to prepare 1 mol L ^-1 of alkali solution 2. Accurately weigh 0.15g of glucose and add it to 100mL of deionized water to prepare carbon source solution 3. Co-precipitate the metal salt solution 1 and the alkali solution 2 into the carbon source solution 3 under stirring at 70°C. The precipitation process requires sufficient stirring to maintain pH = 7, and aging at 70°C for 2 hours. The precipitate is washed with deionized water until there is no sodium ion. Until detection, dry at 110℃ for 12h, calcine at 400℃ for 4h in _N2 atmosphere, and then pass in 20% _H2 / _N2 to reduce the catalyst (30mLmin ^-1 ) to obtain copper source, zinc source and zirconium source. The carbon-modified copper-based catalyst with a total molar to carbon molar ratio of 1:0.05 was named GLC-CZZ.

Comparative example 1

Accurately weigh Cu(NO ₃ ) ₂ ·3H ₂ O 14.50g, Zn(NO ₃ ) ₂ ·6H _{2 O} 8.93g, and Zr(NO ₃ ) ₄ · according to the Cu, Zn, Zr molar ratio of 6:3:1. Dissolve 4.29g of 5H ₂ O in 100 mL of deionized water to prepare a metal salt solution 1 with a total metal ion concentration of 1 mol L ^-1 ; accurately weigh 15.90 g of Na ₂ CO ₃ and dissolve it in 150 mL of deionized water to prepare a metal salt solution of 1 mol L ^- Alkali solution 2 of ¹ ; Co-precipitate metal salt solution 1 and alkali solution 2 into 100 mL deionized water under stirring at 70°C. The precipitation process requires sufficient stirring, maintaining pH = 7, aging at 70°C for 2 hours, and the precipitate is washed with deionized water. Until no sodium ions are detected, dry at 110°C for 12h, calcined at 400°C for 4h under _N2 atmosphere, and then pass in 20% _H2 / _N2 to reduce the catalyst (30mLmin ^-1 ). The obtained catalyst is named CZZ.

Comparative example 2

Accurately weigh Cu(NO ₃ ) ₂ ·3H ₂ O 14.50g, Zn(NO ₃ ) ₂ ·6H _{2 O} 8.93g, and Zr(NO ₃ ) ₄ · according to the Cu, Zn, Zr molar ratio of 6:3:1. Dissolve 4.29g of 5H ₂ O in 100 mL of deionized water to prepare solution 1 with a total metal ion concentration of 1 mol L ^-1 . Accurately weigh 15.90g of Na ₂ CO ₃ and dissolve it in 150 mL of deionized water to prepare 1 mol L ^-1 of alkali solution 2. Accurately weigh 0.06g of CNTs and add it to 100mL of deionized water to prepare carbon-containing suspension 3. Co-precipitate the metal salt solution 1 and the alkali solution 2 into the carbon source suspension 3 under stirring at 70°C. The precipitation process requires sufficient stirring to maintain pH = 7, and aging at 70°C for 2 hours. The precipitate is washed with deionized water until it is gone. Until sodium ions are detected, dry at 110°C for 12h, calcined at 400°C for 4h in _N2 atmosphere, and then pass in 20% _H2 / _N2 to reduce the catalyst (30mLmin ^-1 ) to obtain copper source, zinc source, The carbon modified catalyst with a total molar ratio of zirconium source to carbon molar ratio is 1:0.05, named CNTs-CZZ.

Comparative example 3

Accurately weigh Cu(NO ₃ ) ₂ ·3H ₂ O 14.50g, Zn(NO ₃ ) ₂ ·6H _{2 O} 8.93g, and Zr(NO ₃ ) ₄ · according to the Cu, Zn, Zr molar ratio of 6:3:1. Dissolve 4.29g of 5H ₂ O in 100 mL of deionized water to prepare a metal salt solution 1 with a total metal ion concentration of 1 mol L ^-1 ; accurately weigh 15.90 g of Na ₂ CO ₃ and dissolve it in 150 mL of deionized water to prepare a metal salt solution of 1 mol L ^- Alkali solution 2 of ¹ ; accurately weigh 0.06g of GO and add it to 100 mL deionized water to prepare a carbon-containing suspension 3; co-precipitate the metal salt solution 1 and alkali solution 2 into a carbon-containing suspension under stirring at 70°C. In liquid 3, the precipitation process requires sufficient stirring, maintaining pH = 7, and aging at 70°C for 2 hours. The precipitate is washed with deionized water until no sodium ions are detected, dried at 110°C for 12 hours, and roasted at 400°C for 4 hours under _N2 atmosphere. Then 20% H ₂ /N ₂ was introduced to reduce the catalyst (30 mL min ^-1 ), and a carbon-modified copper-based catalyst with a total molar ratio of copper source, zinc source, and zirconium source to carbon molar ratio of 1:0.05 was obtained, named GO. -CZZ.

Comparative example 4

Industrial copper-zinc-aluminum methanol synthesis catalyst (industrial catalyst-1).

In order to evaluate the catalytic performance of the prepared catalyst, the performance test of the catalyst for _CO hydrogenation to methanol was carried out through a micro-reaction evaluation device. Use a fixed bed reactor, add each catalyst, and then pass in a CO ₂ /H ₂ /N ₂ (23:69:8) gas mixture with a flow rate of 50mL min ^-1 , and perform CO ₂ hydrogenation at 220°C and 3MPa. Methanol synthesis reaction, the results are shown in Table 1.

Table 1 Reaction performance evaluation results of each embodiment

Reaction conditions: T=220°C, P=3.0MPa, H ₂ /CO ₂ =3, WHSV=6000mLg _cat ^-1 h ^-1

From the results listed in Table 1, it can be found that the catalyst of the present invention uses a soluble carbon source as an auxiliary agent and modifies the catalyst by in-situ carbonization to generate carbon, which improves the activity and methanol selectivity of the copper-based catalyst, significantly Increase the yield of methanol. The methanol selectivity of the catalyst can be improved when the carbon content is in the range of 1 to 30 mol%. As the carbon content increases, the methanol selectivity of the catalyst shows a volcano-shaped curve. The best effect is when the carbon content is 5 mol%. The CO ₂ conversion rate reached 20.3%, and methanol selectivity reached 95.2%. Under the same carbon content, compared with copper-based catalysts directly incorporated into carbon materials, carbon-modified copper-based catalysts prepared by in-situ carbonization using soluble compounds as carbon sources can simultaneously improve carbon dioxide conversion rate and methanol selectivity.

From the EDS-mapping diagram of the copper-based catalyst β-CZZ prepared in Example 1 in Figure 1, it can be found that in the carbon-modified copper-zinc-zirconium catalyst prepared by in-situ carbonization using β-cyclodextrin as the carbon source, C is evenly dispersed in the catalyst surface, tightly bound to the active component copper species.

From the contact angle measurement diagrams of the copper-based catalysts prepared in Example 1 and Comparative Example 1 in Figure 2, it can be found that the copper-based catalyst β-CZZ prepared in Example 1 has a larger contact angle, indicating that carbon modification of the catalyst surface can Improve the hydrophobicity of the catalyst surface to a certain extent.

In order to evaluate the stability of the prepared catalyst, the performance of Example 1, Example 6 and Comparative Example 1 were compared before and after heat resistance. Heat resistance conditions: heat resistance at 350°C for 8 hours. The results are shown in Table 2.

Table 2 Thermal stability evaluation results of each example

Reaction conditions: T=220°C, P=3.0MPa, H ₂ /CO ₂ =3, WHSV=6000mLg _cat ^-1 h ^-1

Heat-resistant conditions: 350℃ heat-resistant for 8 hours

From the results listed in Table 2, it can be found that compared with Comparative Example 1, the CO ₂ conversion rate and methanol selectivity of the catalyst described in the present invention before and after heat resistance are almost not reduced, indicating that the carbon-modified copper base obtained by the preparation method of the present invention The catalyst has good structural stability. Surface carbon plays a role in structural confinement of copper species, inhibiting the agglomeration and deactivation of Cu active components during the heat-resistant process. Moreover, the modification of carbon enhances the hydrophobicity of the catalyst surface, making the reaction process The timely desorption of H ₂ O generated in the catalyst helps to maintain the stability of the valence state of copper species. Therefore, after heat resistance, the catalyst still maintains high CO ₂ conversion rate and methanol selectivity, showing high heat resistance stability.

Claims (8)

1. A copper-based catalyst for the hydrogenation of carbon dioxide to methanol, characterized in that the components of the catalyst include Cu, ZnO, ZrO ₂ or Al ₂ O ₃ and auxiliary agent C, and Cu, ZnO, ZrO ₂ or Al ₂ O in the catalyst _3. Evenly dispersed. The additive C is evenly dispersed on the surface of the catalyst and closely combines with the active component copper species to promote the dispersion of the copper species. At the same time, it plays a certain limiting role in the copper species and enhances the hydrophobicity of the catalyst surface, making the copper The price of species remains stable. 2. A kind of copper-based catalyst for carbon dioxide hydrogenation to methanol according to claim 1, characterized in that each component in the catalyst is based on molar percentage, Cu is 20-70%, Zn is 10-60%, Zr or Al 1-20%, C 1-30%. 3. A method for preparing a copper-based catalyst for carbon dioxide hydrogenation to methylate according to claim 1 or 2, using a copper source, a zinc source, a zirconium source or an aluminum source as raw materials, sodium carbonate as a precipitant, and soluble organic The compound is used as a carbon source, and coprecipitation-in-situ carbonization-reduction is used to obtain a carbon-modified copper-based catalyst, which is characterized by specifically including the following steps: 1) According to the input ratio, dissolve the copper source, zinc source, zirconium source or aluminum source in water to prepare a metal salt solution; dissolve sodium carbonate in water to prepare a sodium carbonate solution, add the carbon source to the water and stir ultrasonically to obtain a solution containing the carbon source; 2) Co-precipitate the metal salt solution and the sodium carbonate solution into the solution containing the carbon source under stirring, and age under stirring. After the precipitation is filtered and washed, the catalyst precursor is obtained; 3) After drying the catalyst precursor obtained in step 2), it is roasted in an inert atmosphere for in-situ carbonization, and then subjected to reduction treatment with H ₂ /N ₂ to obtain a copper methoxide-based catalyst for carbon dioxide hydrogenation. 4. The preparation method of a copper-based catalyst for carbon dioxide hydrogenation to methylate according to claim 3, characterized in that the carbon source is β-cyclodextrin, polyethylene glycol (PEG), ethylene glycol (EG), One or more of glucose or soluble starch. 5. The preparation method of a copper-based catalyst for carbon dioxide hydrogenation to methylate according to claim 3, characterized in that the copper source is copper nitrate or copper acetate; the zinc source is zinc nitrate or zinc acetate; the zirconium source is zirconium nitrate or Zirconyl nitrate; the aluminum source is aluminum nitrate or pseudo-boehmite. 6. A method for preparing a copper-based catalyst for carbon dioxide hydrogenation to methylate according to claim 3, characterized in that the molar ratio of the total molar amount of copper source, zinc source, zirconium source or aluminum source to carbon is 1:0.01- 0.3. 7. The preparation method of a copper-based catalyst for carbon dioxide hydrogenation to methylate according to claim 3, characterized in that the specific operation of step 2) is as follows: at 10-80°C, the metal salt solution and the sodium carbonate solution flow together. Titrate into the solution containing the carbon source in step 1) and stir thoroughly to co-precipitate, keeping the pH = 7-10. After precipitation, stir and age at 40-100°C for 0.5-24 hours. The precipitate is washed with deionized water until no sodium ions are detected. A catalyst precursor is obtained. 8. A method for preparing a copper-based catalyst for carbon dioxide hydrogenation to methylate according to claim 3, characterized in that the catalyst precursor drying conditions in step 3) are: drying at 60-160°C for 10-15h; roasting The conditions are: roasting at 300-500°C for 3-6 hours under nitrogen or argon atmosphere.