阅读说明：本技术 一种甲烷干重整反应催化剂及其制备方法和应用 (Methane dry reforming reaction catalyst and preparation method and application thereof ) 是由 盖希坤 杨丹 张桂华 童明亮 杨瑞芹 吕鹏 邢闯 张良佺 于 2019-11-21 设计创作，主要内容包括：本发明公开了一种甲烷干重整反应催化剂及其制备方法和应用,属于催化剂技术领域。本发明的催化剂为核/壳结构,以载体负载的活性组分为核,以SiO<Sub>2</Sub>为壳,其中：所述活性组分是由Ni和M组成的Ni-M合金,M为Cu、Co、Fe、Sn中的任一种。本发明制备的新型甲烷干重整反应催化剂采用Ni基纳米合金作为活性组分具有催化活性高、抗积碳的特性；采用SiC或Al<Sub>2</Sub>O<Sub>3</Sub>作载体,具有化学稳定性好、热导率高、机械强度大、比重小等诸多优点,可与多孔SiO<Sub>2</Sub>壳构成高透过性的骨架结构,快速实现反应物与产物的内外扩散和热扩散,提高催化剂的稳定性和催化效率；核壳结构能够防止催化剂活性组分高温下的烧结,具有广泛的应用前景。(The invention discloses a methane dry reforming reaction catalyst, a preparation method and application thereof, and belongs to the technical field of catalysts. The catalyst of the invention is of a core/shell structure, takes active components loaded by a carrier as a core and takes SiO 2 Is a shell, wherein: the active component is Ni-M alloy consisting of Ni and M, wherein M is any one of Cu, Co, Fe and Sn. The novel methane dry reforming reaction catalyst prepared by the invention adopts Ni-based nano alloy as an active component, and has the characteristics of high catalytic activity and carbon deposition resistance; using SiC or Al 2 O 3 Used as carrier, has the advantages of good chemical stability, high thermal conductivity, high mechanical strength, small specific gravity and the like, and can be used together with porous SiO 2 The shell forms a high-permeability framework structure, internal and external diffusion and thermal diffusion of reactants and products are quickly realized, and the catalyst is improvedStability and catalytic efficiency; the core-shell structure can prevent the sintering of the active components of the catalyst at high temperature, and has wide application prospect.)

1. A catalyst for dry reforming reaction of methane, characterized by: the catalyst is of a core/shell structure, takes active components loaded by a carrier as a core and takes SiO₂Is a shell, wherein: the active component is Ni-M alloy consisting of Ni and M, wherein M is any one of Cu, Co, Fe and Sn.

2. The catalyst for dry reforming of methane according to claim 1, wherein: the catalyst consists of the following components in percentage by mass: 6-20% of active component, 60-92% of carrier and SiO₂2～20％，The sum of the mass percentages of the components is 100 percent.

3. The catalyst for dry reforming of methane according to claim 1, wherein: the carrier is SiC or Al₂O₃。

4. The method for preparing a catalyst for dry reforming of methane according to claim 1, wherein: the method specifically comprises the following steps:

(1) preparing a precursor of the active component of the catalyst into an aqueous solution, and adding the aqueous solution into a carrier to prepare a catalyst precursor;

(2) drying the catalyst precursor prepared in the step (1);

(3) placing the catalyst precursor dried in the step (2) in a microwave reactor, introducing reducing gas into the reactor, then adjusting the microwave power, carrying out flash heating on the microwave reactor at a heating rate of 1000-10000 ℃/s to 400-800 ℃ for carrying out constant-temperature reduction reaction for 0.1-60 min, introducing protective gas into the reactor after the reaction is finished, and finally cooling to room temperature to obtain the Ni-M/carrier nano alloy;

(4) passivating the Ni-M/carrier nano alloy obtained in the step (3);

(5) immersing the Ni-M/carrier nano alloy passivated in the step (4) into ethanol, adding ammonia water to obtain a mixed solution, then continuously adding a silicon source and an auxiliary agent into the mixed solution, uniformly mixing, performing hydrothermal synthesis reaction, naturally cooling to room temperature after the reaction is finished, centrifuging, washing, drying and roasting a product to obtain the methane dry reforming reaction catalyst Ni-M/carrier @ SiO₂。

5. The method for preparing a catalyst for dry reforming reaction of methane according to claim 4, wherein: in the step (3), the reducing gas is H₂Or CO, wherein the volume concentration of the reducing gas is 5-100%.

6. The method for preparing a catalyst for dry reforming reaction of methane according to claim 4, wherein: in the step (4), the passivation process specifically comprises: and (3) at normal temperature, passivating the Ni-M/carrier nano alloy obtained in the step (3) in a passivation gas for 1-60 min, wherein: the oxygen-containing passivation gas is a mixture of nitrogen and air.

7. The method for preparing a catalyst for dry reforming reaction of methane according to claim 4, wherein: in the step (5), the silicon source is any one of sodium silicate, potassium silicate, silica sol, methyl orthosilicate, ethyl orthosilicate, butyl orthosilicate and propyl orthosilicate.

8. The method for preparing a catalyst for dry reforming reaction of methane according to claim 4, wherein: in the step (5), the temperature of the hydrothermal synthesis is 200-400 ℃, and the time of the hydrothermal synthesis is 2-96 hours.

9. The method for preparing a catalyst for dry reforming reaction of methane according to claim 4, wherein: in the step (5), the roasting process is specifically as follows: the roasting temperature is 500-800 ℃, and the roasting time is 0.5-10 h.

10. Use of a catalyst for dry methane reforming reaction according to any one of claims 1 to 3 or a catalyst for dry methane reforming reaction prepared by a method according to any one of claims 4 to 9 in dry methane reforming reaction.

Technical Field

The invention belongs to the technical field of catalysts, and particularly relates to a methane dry reforming reaction catalyst, and a preparation method and application thereof.

Background

How to realize CH₄And CO₂The high-efficiency conversion and utilization is an important subject in the fields of 21 st century catalysis and environmental protection. CH (CH)₄-CO₂Synthesis gas H produced by reforming reaction₂The ratio of the carbon to the oxygen is about 1, the catalyst can be directly used as a raw material for oxo synthesis and Fischer-Tropsch synthesis, and the overlarge hydrogen-carbon ratio (H) of the synthesis gas produced by methane steam reforming is compensated₂CO ≧ 3) is a rational utilization of CH₄、CO₂An effective way of resource. CH (CH)₄-CO₂The development of the reforming technology has important significance for reducing the emission of greenhouse gases and relieving the energy crisis.

CH₄-CO₂Reforming catalysts mainly comprise two main types of precious metals (Ru, Rh, Pd and Pt) and non-precious metals (Ni, Co, Cu and Fe). The noble metal catalyst has the advantages of high catalytic activity, strong carbon deposition resistance, good stability and the like, but the large-scale application of the noble metal catalyst is restricted by limited resources and high price. Among non-noble metals, Ni has activity comparable to noble metals and is recognized as the most promising catalyst for industrial applications, however, Ni-based catalysts have the disadvantage of being prone to carbon deposition and sintering at high temperatures leading to catalyst deactivation. In recent years, CoNi alloy catalysts have been used for CH₄-CO₂Reforming reaction and shows outstanding catalytic performance. Co and Ni form an alloy catalyst, the surface structure and the property of Ni can be changed, and nucleation sites of whisker-shaped carbon can be blocked, so that carbon deposition of the catalyst can be effectively inhibited; meanwhile, the alloy structure can well inhibit the oxidation of Co and Ni in the reaction process, so thatThe catalyst exhibits better stability.

At present, the preparation method of the alloy catalyst mainly comprises a sol-gel method, a solvothermal method, a chemical reduction method and the like, wherein the chemical reduction method is a commonly used method for preparing the alloy catalyst, and a catalyst precursor and a carrier are fully mixed, and then are reduced by a chemical reducing agent or reduced at a high temperature in a hydrogen atmosphere to form an alloy structure. The chemical reduction method adopting gas reduction has the advantages of simple operation, easy realization of large-scale production and the like, but the preparation process is long, and in addition, Co is used²⁺Is liable to Ni²⁺And when the tubular furnace is used for hydrogen reduction, the tubular furnace is heated to the target reduction temperature for a long time due to the slow heating rate of the tubular furnace, different active components are reduced successively in the heating process, the formation of the alloy structure of the catalyst is influenced, and the catalyst generated in the process is different from the catalyst obtained by constant-temperature reduction under the target temperature condition, so that the composition, the particle size and the alloy degree of the prepared alloy catalyst are difficult to control accurately. In addition, the alloy catalyst has smaller particles than that of a Co-based or Ni-based catalyst with the same content, thereby showing more excellent catalytic activity and anti-carbon deposition performance, however, as the particle size is reduced, the surface energy of the alloy is increased sharply, and agglomeration is easy to occur at high temperature, thereby causing the activity of the catalyst to be reduced or even deactivated.

Disclosure of Invention

In view of the problems or defects of the prior art, the present invention aims to provide a methane dry reforming reaction catalyst, a preparation method and an application thereof.

In order to achieve the first object of the present invention, the present invention adopts the following technical solutions:

a catalyst for dry reforming reaction of methane is a core/shell structure, which uses active component carried by carrier as core and SiO₂Is a shell, wherein: the active component is Ni-M alloy consisting of Ni and M, wherein M is any one of Cu, Co, Fe and Sn.

Further, according to the technical scheme, the catalyst comprises the following components in percentage by mass: active component 6 ℃20 percent of carrier, 55-92 percent of SiO₂2-20%, and the sum of the mass percentages of the components is 100%.

Further, in the above technical scheme, the carrier is SiC or Al₂O₃。

Preferably, in the above technical solution, the carrier is SiC.

Further, according to the above technical solution, the atomic ratio of Ni and M in the Ni-M alloy is 1: (1-1.5).

Further, according to the technical scheme, the active ingredients are composed of Ni and Co.

The second object of the present invention is to provide a method for preparing the above catalyst for dry reforming of methane, which specifically comprises the following steps:

(1) preparing a precursor of the active component of the catalyst into an aqueous solution, and adding the aqueous solution into a carrier to prepare a catalyst precursor;

(2) drying the catalyst precursor prepared in the step (1);

(3) placing the catalyst precursor dried in the step (2) in a microwave reactor, introducing reducing gas into the reactor, then adjusting the microwave power, carrying out flash heating on the microwave reactor at a heating rate of 1000-10000 ℃/s to 400-800 ℃ for carrying out constant-temperature reduction reaction for 0.1-60 min, introducing protective gas into the reactor after the reaction is finished, and finally cooling to room temperature to obtain the Ni-M/carrier nano alloy;

(4) passivating the Ni-M/carrier nano alloy obtained in the step (3);

(5) immersing the Ni-M/carrier nano alloy passivated in the step (4) into ethanol, adding ammonia water to obtain a mixed solution, then continuously adding a silicon source and an auxiliary agent into the mixed solution, uniformly mixing, performing hydrothermal synthesis reaction, naturally cooling to room temperature after the reaction is finished, centrifuging, washing, drying and roasting a product to obtain the methane dry reforming reaction catalyst Ni-M/carrier @ SiO₂。

Further, in the technical scheme, in the step (1), the alloy catalyst precursor is prepared by adopting an ultrasonic-assisted isometric immersion method.

Further, according to the technical scheme, before the catalyst precursor is reduced, the drying process of the catalyst precursor in the step (2) is step-by-step drying, the drying temperature and time are reasonably controlled, the catalyst precursor is dried for 30-120 min at the temperature of below 80 ℃, and then the temperature is raised as required for further drying, so that the cracking of the catalyst in the drying process can be effectively prevented.

Preferably, in the above technical solution, the step-by-step drying process specifically comprises: firstly, drying for 30-120 min at 50-80 ℃; then heating to 110-130 ℃ and drying for 30-120 min. According to the invention, through distributed drying, the catalyst can be prevented from being heated too fast to cause structural collapse or even breakage.

Further, in the above technical solution, in the step (3), the reducing gas is H₂Or CO, wherein the volume concentration of the reducing gas is 5-100%.

Further, in the above technical scheme, in the step (3), the protective gas is N₂Or any inert gas, and protective gas is filled in the reactor in the process of cooling, so that the nano alloy can be effectively protected from being oxidized.

Specifically, in the above technical solution, in the step (4), in order to prevent the generated nano alloy catalyst from being oxidized, the nano alloy catalyst is passivated.

Further, in the above technical solution, in the step (4), the passivation process specifically includes: and (3) at normal temperature, passivating the Ni-M/carrier nano alloy obtained in the step (3) in a passivation gas for 1-60 min, wherein: the oxygen-containing passivation gas is a mixture of nitrogen and air.

Specifically, in the above technical scheme, the normal temperature refers to a natural room temperature condition in four seasons, no additional cooling or heating treatment is performed, and the normal temperature is generally controlled to be 10-30 ℃, preferably 15-25 ℃.

Preferably, in the above technical solution, the oxygen-containing passivation gas is a mixture of nitrogen and air, wherein the oxygen volume percentage concentration is 0.5% to 5%, and more preferably 0.5% to 2%.

Further, in the technical scheme, in the step (5), the concentration of the ammonia water is 20-40 wt%.

Further, in the above technical solution, in the step (5), the silicon source is any one of sodium silicate, potassium silicate, silica sol, methyl orthosilicate, ethyl orthosilicate, butyl orthosilicate, or propyl orthosilicate.

Further, in the above technical solution, in the step (5), the assistant includes a surfactant and a pore-expanding agent.

Further, in the above technical scheme, in the step (5), the temperature of the hydrothermal synthesis is 200-400 ℃, and the time of the hydrothermal synthesis is 2-96 hours.

Further, in the above technical scheme, in the step (5), the roasting process is specifically as follows: the roasting temperature is 500-800 ℃, and the roasting time is 0.5-10 h.

A third object of the present invention is to provide the use of the above catalyst in dry reforming reactions of methane.

Compared with the prior art, the invention has the following beneficial effects:

(1) the novel methane dry reforming reaction catalyst prepared by the invention organically combines the high activity and the anti-carbon deposition characteristic of the nano alloy with the anti-sintering characteristic of the core-shell structure, solves the problems of easy carbon deposition and sintering of the Ni-based catalyst at high temperature, improves the activity of the catalyst, and has wide application prospect.

(2) The invention develops a microwave reduction method for preparing an alloy catalyst based on the advantage of high-efficiency mass and heat transfer of microwave heating.

(3) The microwave reactor adopted by the invention has the characteristic of flash temperature rise, and the time for raising the microwave reactor to the target reduction temperature is negligible, so that the whole reduction process of the catalyst precursor of the invention can be considered to be carried out under the constant temperature condition, therefore, the composition, the particle size and the alloying degree of the alloy catalyst product finally prepared by the invention can be controlled, and the catalyst prepared by the invention has the advantages of small particle, large specific surface area and high alloying degree.

Drawings

FIG. 1 is a schematic structural view of a catalyst prepared in example 1 of the present invention.

Detailed Description

The present invention will be described in further detail below with reference to examples. The present invention is implemented on the premise of the technology of the present invention, and the detailed embodiments and specific procedures are given to illustrate the inventive aspects of the present invention, but the scope of the present invention is not limited to the following embodiments.

Various modifications to the precise description of the invention will be readily apparent to those skilled in the art from the information contained herein without departing from the spirit and scope of the appended claims. It is to be understood that the scope of the invention is not limited to the procedures, properties, or components defined, as these embodiments, as well as others described, are intended to be merely illustrative of particular aspects of the invention. Indeed, various modifications of the embodiments of the invention which are obvious to those skilled in the art or related fields are intended to be covered by the scope of the appended claims.

For a better understanding of the invention, and not as a limitation on the scope thereof, all numbers expressing quantities, percentages, and other numerical values used in this application are to be understood as being modified in all instances by the term "about". Accordingly, unless expressly indicated otherwise, the numerical parameters set forth in the specification and attached claims are approximations that may vary depending upon the desired properties sought to be obtained. At the very least, each numerical parameter should at least be construed in light of the number of reported significant digits and by applying ordinary rounding techniques.

The catalyst for dry reforming reaction of methane is prepared from carrier SiC or Al₂O₃Loading active component and coating SiO₂The shell layer is an alloy with an active component consisting of Ni and M, wherein M is one of Cu, Co, Fe and Sn. The nano alloy structure has the characteristics of high catalytic activity and carbon deposition resistance; using SiC or Al₂O₃Used as carrier, has the advantages of good chemical stability, high thermal conductivity, high mechanical strength, etc., and can be used in combination with porous SiO₂The shell forms a high-permeability framework structure, internal and external diffusion and thermal diffusion of reactants and products are quickly realized, and the stability and heat diffusion of the catalyst are improvedThe catalytic efficiency; the core-shell structure can prevent the sintering of the active components of the catalyst at high temperature.

The methane dry reforming reaction catalyst prepared by the invention organically combines the high activity and the anti-carbon deposition characteristic of the nano alloy with the anti-sintering characteristic of the core-shell structure, not only solves the problem that the Ni-based catalyst is easy to deposit carbon and sinter at high temperature, but also improves the activity of the catalyst, and has wide application prospect.