阅读说明：本技术 一种催化剂、制备方法及其应用 (Catalyst, preparation method and application thereof ) 是由 孙绍晖 陈千正 张凡英 高健 韩一帆 于 2019-09-18 设计创作，主要内容包括：本发明涉及一种催化剂的制备方法：1)将镍盐均匀分散到极性溶剂中获得浓度为0.007-0.1mol/L的溶液A,将载体TiO<Sub>2</Sub>均匀分散到碱液中获得体系B,将溶液A与体系B混合均匀,室温下老化12-24h,洗涤至中性；或者将镍离子均匀分散到极性溶剂中获得浓度为0.007-0.1mol/L的溶液A,将载体TiO<Sub>2</Sub>均匀分散到极性溶剂中获得体系B,将溶液A与体系B混合均匀；2)然后在70-90℃条件下干燥12-24h,于350-450℃焙烧3-4h,即得。本发明催化剂通过调变溶液环境即可实现选择性的改变,在CO<Sub>2</Sub>加氢反应中表现出优异的低温催化性能,一方面,在CO<Sub>2</Sub>甲烷化反应中甲烷选择性达到99%,活性衰减小；另一方面,在逆水煤气反应中也能高选择性99%的生成一氧化碳,稳定性较强。(The invention relates to a preparation method of a catalyst, which comprises the following steps: 1) uniformly dispersing nickel salt into a polar solvent to obtain a solution A with the concentration of 0.007-0.1mol/L, and adding a carrier TiO 2 Uniformly dispersing the solution A into alkali liquor to obtain a system B, uniformly mixing the solution A and the system B, aging at room temperature for 12-24h, and washing to be neutral; or uniformly dispersing nickel ions into a polar solvent to obtain a solution A with the concentration of 0.007-0.1mol/L, and adding a carrier TiO 2 Uniformly dispersing the solution A into a polar solvent to obtain a system B, and uniformly mixing the solution A and the system B; 2) then drying at 70-90 ℃ for 12-24h, and roasting at 350-450 ℃ for 3-4 h. The catalyst can realize the change of selectivity by changing the solution environment, and CO is subjected to 2 Exhibits excellent low-temperature catalytic performance in hydrogenation reactions, on the one hand, in CO 2 Methane separation in methanation reactionThe selectivity reaches 99%, and the activity is reduced; on the other hand, carbon monoxide can be generated with high selectivity of 99% in the reverse water gas reaction, and the stability is strong.)

1. A preparation method of a catalyst is characterized by comprising the following steps:

1) uniformly dispersing nickel salt into a polar solvent to obtain a solution A with the concentration of 0.007-0.1mol/L, and adding a carrier TiO₂Uniformly dispersing the solution A into alkali liquor to obtain a system B, uniformly mixing the solution A and the system B, aging at room temperature for 12-24h, and washing to be neutral;

or uniformly dispersing nickel ions into a polar solvent to obtain a solution A with the concentration of 0.007-0.1mol/L, and adding a carrier TiO₂Uniformly dispersing the solution A into a polar solvent to obtain a system B, and uniformly mixing the solution A and the system B;

2) then drying at 70-90 ℃ for 12-24h, roasting the dried product at 350-450 ℃ for 3-4h to obtain the TiO₂A supported catalyst.

2. The method for preparing the catalyst according to claim 1, wherein in the step 1), the nickel salt is one or a mixture of more than two of nickel nitrate, nickel acetate, nickel chloride and hydrates thereof in any proportion; the support TiO₂Anatase and/or rutile.

3. The process for preparing the catalyst according to claim 1, wherein in step 1), the supported TiO is present in the system B₂The concentration of the solution A is 0.3-4mol/L, and the volume ratio of the solution A to the system B is 0.4-7: 1, mixing.

4. The method for preparing the catalyst according to claim 1, wherein in the step 1), the polar solvent is one or a mixture of two or more of deionized water, monohydric alcohol of C1-C4 and dihydric alcohol of C2-C4 in any proportion; the alkali liquor is sodium carbonate solution, sodium bicarbonate solution, ammonia water, ammonium bicarbonate solution or ammonium carbonate solution with the concentration of 0.1-0.5 mol/L; ethanol solution with volume concentration of 15-45% is selected for washing.

5. The method for preparing the catalyst according to claim 1, wherein in the step 2), the dried product is heated to the calcination temperature at a heating rate of 2 to 5 ℃/min.

6. A catalyst prepared by the method of any one of claims 1 to 5.

7. Use of the catalyst of claim 6 for catalyzing a carbon dioxide methanation reaction and/or a reverse water gas shift reaction.

8. The use of the catalyst of claim 7 in catalyzing carbon dioxide methanation and/or reverse water gas shift reactions, wherein the catalyst is reduced for 3-5h at 400-450 ℃ in a reducing atmosphere before use to obtain xNi/TiO₂A catalyst.

9. Use of the catalyst according to claim 8 for catalysing the methanation and/or reverse water gas shift reactions of carbon dioxide, wherein the reducing atmosphere is hydrogen, carbon monoxide, a mixture of hydrogen and an inert gas, or a mixture of carbon monoxide and an inert gas.

Technical Field

The invention belongs to the technical field of heterogeneous catalysis, and particularly relates to a catalyst, a preparation method and application thereof in catalyzing methanation reaction of carbon dioxide and/or reverse water gas shift reaction, namely application in reaction for preparing methane or carbon monoxide by hydrogenation of carbon dioxide.

Background

In recent years, more and more carbon dioxide is emitted into the atmosphere, which has attracted widespread attention all over the world. Recycling carbon dioxide to reduce the detrimental effects of these emissions is one of the hot spots under investigation because carbon dioxide can be considered as a zero or even negative cost carbon feedstock. The conversion of renewable hydrogen and carbon dioxide into high value-added chemicals is one of the effective methods for recovering carbon dioxide to provide useful fuels, and the current main research content is the conversion of carbon dioxide into C1 products (methanol, carbon monoxide, methane), low-carbon olefins, aromatic hydrocarbons, high-chain hydrocarbons and the like through thermal catalysis or electrocatalysis, which has potential commercial application and environmental benefits.

The methanation reaction of carbon dioxide takes carbon dioxide and hydrogen as raw materials to synthesize the clean energy methane with high calorific value, namely CO₂+4H₂→CH₄+2H₂O, methane is easy to liquefy and can be stored safely in a large amount through existing infrastructure, even the existing natural gas pipeline network can be directly introduced to serve as fuel, the shortage of natural gas resources in China is relieved, and in addition, the function of balancing the stability of a power grid can be realized through electric power-natural gas.

Reverse water gas shift reaction, i.e. hydrogenation of carbon dioxide to carbon monoxide (CO)₂+H₂→CO+H₂O), is considered to be one of the most promising reactions, while this is for CO₂The utilization of and production of energy is of great significance and many researchers believe that CO is also CO₂The key step of hydrogenation to produce long-chain hydrocarbon.

At present, CO₂In the aspect of hydrogenation reaction regulation and control, the size of metal particles is mainly changed, the crystal face or the morphology of metal is changed, the confinement of a molecular sieve is changed, and the synthesis process is complex, so that a new catalyst suitable for carbon dioxide methanation reaction and/or reverse water gas shift reaction needs to be researched urgently.

Disclosure of Invention

The invention aims to overcome the defects of the prior art and aims at CO₂Hydrogenation reaction, and provides a method for preparing catalyst by simply modulating product selectivity, and the catalyst prepared by the method is used in CO₂The catalyst shows excellent catalytic performance in methanation and reverse water gas change reaction, the product is modulated thoroughly, and the selectivity is as high as 99%. The preparation method is simple and convenient, and can be used for preparing other CO₂Hydrogenation reactions provide a certain reference.

In order to achieve the purpose, the invention adopts the following technical scheme:

the invention provides a carbon dioxide hydrogenation catalyst for regulating and controlling selectivity of methane and carbon monoxide, which is used for xNi/TiO₂Wherein the carrier component is TiO₂The active component is Ni, and the selectivity of the product can be adjusted by changing the types of ligands of the precipitator, the pH value, the polarity of a nickel source or a solvent and the like. The catalyst comprises the following raw materials in percentage by mass: 90-99% of carrier component and 1-10% of active component, wherein the sum of the mass percentages is 100%; specifically, the preparation method of the catalyst comprises the following steps:

1) the preparation method comprises the following steps of: uniformly dispersing nickel salt into a polar solvent to obtain a solution A with the concentration of 0.007-0.1mol/L, and adding a carrier TiO₂Uniformly dispersing in alkali liquor to obtain a system B, uniformly mixing the solution A and the system B (preferably dropwise adding the solution A into the system B), aging at room temperature for 12-24h, and washing to neutrality;

or the preparation method comprises the following steps: uniformly dispersing nickel ions into a polar solvent to obtain a solution A with the concentration of 0.007-0.1mol/L, and adding a carrier TiO₂Uniformly dispersing the solution A into a polar solvent to obtain a system B, and uniformly mixing the solution A and the system B;

2) then drying at 70-90 ℃ for 12-24h, roasting the dried product at 350-450 ℃ for 3-4h to obtain the TiO₂A supported catalyst.

Specifically, in the step 1), the nickel salt is one or a mixture of more than two of nickel nitrate, nickel acetate and nickel chloride in any proportion, and the nickel salt can also be a hydrate thereof; the support TiO₂Anatase and/or rutile, titanium dioxide P25 being preferred when anatase and rutile are mixed.

Specifically, in the step 1), the carrier TiO in the system B₂The concentration of the solution A is 0.3-4mol/L, and the volume ratio of the solution A to the system B is 0.4-7: 1, mixing. Further, the solution A can be dropwise added into the system B at a certain speed and stirred simultaneously, and stirring is carried out for 1-5 hours after the dropwise addition is finished; or the two may be mixed together and sonicated for several hours to disperse them uniformly.

Specifically, in the step 1), the polar solvent is any one or a mixture of more than two of deionized water, monohydric alcohol of C1-C4 and dihydric alcohol of C2-C4 in any proportion; the alkali liquor is sodium carbonate solution, sodium bicarbonate solution, ammonia water, ammonium bicarbonate solution or ammonium carbonate solution with the concentration of 0.1-0.5 mol/L; ethanol solution with volume concentration of 15-45% is selected for washing.

Specifically, in the step 2), the temperature of the dried product is increased to the roasting temperature at the temperature increasing rate of 2-5 ℃/min.

The invention provides a catalyst prepared by the preparation method.

The invention also provides application of the catalyst in catalyzing carbon dioxide methanation reaction and/or reverse water gas shift reaction.

The catalyst is applied to catalyzing carbon dioxide methanation reaction and/or reverse water gas shift reaction, and particularly, the catalyst is reduced for 3-5h at the temperature of 400-450 ℃ in a reducing atmosphere in advance before being used to obtain xNi/TiO₂A catalyst. Wherein the flow rate of the reducing atmosphere is 50-100ml/min, and the temperature is raised to 400-450 ℃ at the temperature rise rate of 1-5 ℃/min.

The catalyst is applied to catalyzing carbon dioxide methanation reaction and/or reverse water gas shift reaction, and specifically, the reducing atmosphere is hydrogen, carbon monoxide, a mixed gas of hydrogen and an inert gas, or a mixed gas of carbon monoxide and an inert gas; ar and H in a preferred volume ratio of 3:2₂The mixed gas of (1).

The experimental conditions of the catalyst used for carbon dioxide hydrogenation are as follows: 0.1g of the catalyst was weighed into a fixed bed reactor and thenThe fixed bed reactor was initially heated under argon atmosphere and reduced in a mixed gas stream. After the reduction is finished, the temperature is reduced to the reaction temperature, and then the molar ratio H is introduced₂:CO₂Ar =4:1:3-5, at the temperature of 250-400 ℃, the reaction pressure is normal pressure-2 MPa, and the space velocity is 10000-60000 ml/(g)_catH), the product is passed on to a chromatograph containing FID and a thermal conductivity detector for on-line detection.

Compared with the prior art, the invention has the remarkable advantages that:

1) the nickel-based catalyst for methanation reaction or hydrogenation reaction of carbon dioxide adopts TiO₂The carrier is adopted, non-noble metal Ni is adopted as an active substance, the preparation raw materials are cheap and easy to obtain, and the preparation method is simple and convenient;

2) the product selectivity of the nickel-based catalyst for the methanation reaction or the hydrogenation reaction of the carbon dioxide reaches 99 percent at the highest, the product selectivity can be adjusted within a certain range, and the product selectivity is adjusted relatively thoroughly.

In conclusion, the catalyst has the advantages of simple preparation process, strong operability and low content of nickel in the active component of the catalyst, can realize the change of selectivity by adjusting the solution environment, and can be used for CO₂Shows excellent low-temperature catalytic performance in hydrogenation reaction, and CO₂In the methanation reaction, the selectivity of methane can reach 99 percent at most, and the activity attenuation is small; in addition, CO can reach 99 percent at most when the method is used for reverse water gas reaction. More importantly, the proportion of methane and carbon monoxide can be regulated and controlled within a certain range, the product distribution can be controlled, and the catalysts have high stability.

Drawings

FIG. 1 is a graph of the catalytic performance results for the catalyst described in example 3;

FIG. 2 is the results of the catalytic performance of the catalyst described in example 4;

FIG. 3 is the results of the catalytic performance of the catalyst described in example 7;

FIG. 4 is the results of the catalytic performance of the catalyst described in example 8;

FIG. 5 shows the results of the catalytic performance of the catalyst described in example 9.

Detailed Description

The technical solution of the present invention is further described in detail with reference to the following examples, but the scope of the present invention is not limited thereto.