阅读说明：本技术 一种双金属低温甲烷化催化剂及其制备方法与应用 (Bimetallic low-temperature methanation catalyst and preparation method and application thereof ) 是由 辛忠 陶淼 于 2018-09-12 设计创作，主要内容包括：本发明公开了一种双金属低温甲烷化催化剂,以介孔分子筛SBA-15为载体,以金属Ni为主要活性组分,以过渡金属或稀土金属中的至少一种作为助金属；其中,金属Ni的含量为5wt％～20wt％,助金属的含量为0.5wt％～2wt％,余量为介孔分子筛SBA-15。所制备的催化剂中活性金属与助金属以合金的形式存在,助金属与活性金属之间存在电子转移,从而使其低温催化性能得到显著提高,同时相互作用力的增强和载体孔道限域作用抑制了活性组分的高温烧结团聚,最终使其具有催化活性高、甲烷选择性好、热稳定性好、催化剂寿命较长等优点；所制备催化剂在低温250℃下可以达到CO转化率100％,甲烷选择性96％,极具工业化前景。(The invention discloses a bimetallic low-temperature methanation catalyst, which takes mesoporous molecular sieve SBA-15 as a carrier, metal Ni as a main active component and at least one of transition metal or rare earth metal as an auxiliary metal; wherein, the content of metal Ni is 5 wt% -20 wt%, the content of auxiliary metal is 0.5 wt% -2 wt%, and the rest is mesoporous molecular sieve SBA-15. The active metal and the assistant metal exist in the prepared catalyst in the form of alloy, and electron transfer exists between the assistant metal and the active metal, so that the low-temperature catalytic performance of the catalyst is obviously improved, and meanwhile, the enhancement of the interaction force and the limitation of the carrier pore channel inhibit the high-temperature sintering agglomeration of the active component, so that the catalyst has the advantages of high catalytic activity, good methane selectivity, good thermal stability, long service life of the catalyst and the like; the prepared catalyst can reach the CO conversion rate of 100 percent and the methane selectivity of 96 percent at the low temperature of 250 ℃, and has great industrial prospect.)

1. A bimetallic low-temperature methanation catalyst is characterized in that: taking mesoporous molecular sieve SBA-15 as a carrier, taking metal Ni as a main active component, and taking at least one of transition metal or rare earth metal as an auxiliary metal; wherein, the content of metal Ni is 5 wt% -20 wt%, the content of auxiliary metal is 0.5 wt% -2 wt%, and the rest is mesoporous molecular sieve SBA-15.

2. The bimetallic low-temperature methanation catalyst of claim 1, characterized in that: the specific surface area of the mesoporous molecular sieve SBA-15 is 600-1000 m²A micropore surface area of 100 to 200m²The pore diameter is 4.6-30 nm, the pore wall is 3-9 nm, and the pore volume is 0.8-1.3 cm³The volume of the micropores is 0.02-0.04 cm³/g。

3. The bimetallic low-temperature methanation catalyst of claim 1, characterized in that: the transition metal is selected from at least one of Fe, Mo and Co;

the rare earth metal is selected from at least one of La and Ce.

4. The bimetallic low-temperature methanation catalyst of claim 1, characterized in that: the specific surface area of the bimetallic low-temperature methanation catalyst is 600-660 m²Per g, the surface area of the micropores is 60-75 m²The pore volume is 0.85-1 cm³The volume of the micropores is 0.01-0.03 cm³(ii)/g, the pore diameter is 5.5 to 5.7 nm.

5. A method for preparing the bimetallic low-temperature methanation catalyst as claimed in any one of claims 1 to 4, characterized in that: the method comprises the following steps:

dissolving nickel salt, a metal precursor and an additive in deionized water, wherein the mass ratio of the nickel salt to the metal precursor to the additive to the deionized water is (1-100): 1: (0.1-15): (10-1000), soaking the mesoporous molecular sieve SBA-15 in the mixed solution at room temperature for 2-12 hours, wherein the mesoporous molecular sieve SBA-15 accounts for 1-90% of deionized water by mass percent, vacuum drying is carried out at the temperature of 30-80 ℃ for 5-12 hours, roasting is carried out at the temperature of 400-800 ℃ for 1-10 hours, and cooling and grinding are carried out to obtain the bimetallic low-temperature methanation catalyst.

6. The preparation method of the bimetallic low-temperature methanation catalyst according to claim 5, characterized in that: the nickel salt is at least one of nickel chloride, nickel sulfate, nickel acetate, nickel oxalate and nickel nitrate.

7. The preparation method of the bimetallic low-temperature methanation catalyst according to claim 5, characterized in that: the metal precursor is a compound containing at least one of the following metals: fe. Mo, Co, La, Ce; specifically, at least one selected from ammonium molybdate, lanthanum nitrate and ferric nitrate.

8. The preparation method of the bimetallic low-temperature methanation catalyst according to claim 5, characterized in that: the additive is at least one of citric acid, cetyl trimethyl ammonium bromide, ethylene glycol, glucose, sorbitol or sodium dodecyl sulfate.

9. Use of a bimetallic low temperature methanation catalyst as claimed in any one of claims 1 to 4 in the production of methane from synthesis gas.

10. Use of the bimetallic low temperature methanation catalyst of claim 9 in the production of methane from synthesis gas, characterized in that: the conditions for preparing methane from the synthesis gas are as follows: the volume airspeed of the synthetic gas is 3000-30000 mL/g.h, and the pressure is from normal pressure to normal pressure3.0Mpa at 200-500 deg.C, H in synthetic gas₂The ratio of/CO is 2-4.

Technical Field

The invention belongs to the technical field of catalytic chemistry, and particularly relates to a high-dispersion limited-range bimetallic low-temperature methanation catalyst, a preparation method thereof and application thereof in preparation of methane from synthesis gas.

Background

The resource structure of China is characterized in that coal is rich, oil is deficient, and gas is low, about 80% of coal consumption is directly converted through combustion, the gradient utilization of resources cannot be realized, not only is the waste of coal resources caused, but also the heat energy utilization rate is low, and a large amount of pollutants are discharged. And natural gas has incomparable economic and environmental protection benefits as clean and efficient energy. At present, the contradiction between supply and demand of natural gas in China is increasingly prominent, and the external dependence degree shows a rapidly rising trend. The statistical natural gas consumption in 2014 is 1870 billion cubic meters, the increase is 12 percent on the same scale, and the external dependence reaches 32 percent; it is expected that gas consumption will likely reach 4850 billion cubic meters in 2020 and that the external dependence will likely reach 37%. Therefore, the relatively rich coal resources (particularly lignite) in China are optimally utilized to prepare Synthetic Natural Gas (SNG), the supply of the SNG with high energy utilization rate can be increased, the emission of greenhouse gases can be greatly reduced, the win-win effect of energy and environment is achieved, and the economic value and the social significance are great.

For coal-based natural gas, the key is synthesis gas methanation technology, and the development of excellent and efficient methanation catalyst has become one of the important points of methanation technology research. The requirements on the coal SNG industrial methanation catalyst are mainly as follows: low temperature, high efficiency (i.e. low reaction temperature, wide range of hydrogen-carbon ratio of raw material gas, high conversion rate of CO and CH)₄High selectivity, good stability (i.e. wear resistance, high temperature resistance, sintering resistance and poisoning resistance), long service life and low cost. Because a large amount of heat is generated in the methanation process of the synthesis gas, the lower the reaction temperature is, the more favorable the methanation reaction is according to thermodynamic equilibrium calculation, and simultaneously, the requirements on the heat resistance of the catalyst and the reactor are also reduced. When the metal Ru is used as an active component, the catalyst still has good activity at the reaction temperature of 200 ℃, but the Ru is expensive, so that the cost of the catalyst is obviously increased, and the development of the low-temperature high-efficiency nickel-based catalyst is necessary. The operation temperature of the current industrial methanation reaction is generally above 400 ℃.

The activity of the catalyst mainly comes from active reaction centers provided by active components, and the distribution and structural properties of the active components Ni on the surface of the carrier directly determine the number of effective active reaction centers, so that the activity, selectivity and stability of the catalyst are influenced finally. From the current research reports, the size of metal particles, the loading amount of active components and metal-carrier interaction are main factors influencing the distribution of Ni on the surface of the carrier, and the structural properties of the active components are closely related to the Ni species type on the surface of the carrier, the atomic arrangement on the surface of the metal particles and the electronic state. The auxiliary agents of the methanation catalyst are mainly divided into two categories: (1) electron assistant: changing the electron transfer property of the catalyst; (2) structural auxiliary agents: the dispersity and thermal stability of metals in the catalyst are improved by changing the chemical composition, crystal structure, pore structure, dispersion state of active components and mechanical strength of the catalyst. In addition, some oxide assistants have both of these functions.

The carrier plays an important role in heterogeneous catalysts in gas-solid reactions, and generally influences the interaction force between metal and the carrier and the dispersion degree of the metal, thereby further influencing the activity, selectivity and stability of the catalyst. So far, metal oxides (Al)₂O₃、SiO₂、ZrO₂、TiO₂、CeO₂Etc.), composite supports (hexaaluminate, solid clay, perovskite) and SiC supports may all be used as supports for methanation catalysts. Among these supports, alumina Al₂O₃Is the most typical and widely studied one, but it readily forms NiAl with Ni at high temperatures₂O₄Spinel, which at the same time sinters under the effect of water vapor and leads to rapid deactivation of the catalyst. Amorphous SiO₂Are also frequently used as supports for catalysts. SiO relative to other supports₂There is a major advantage in that the pore size, specific surface area and pore volume are easily adjustable and controllable. But increase SiO as well as alumina support₂The hydrothermal stability of the support also requires further investigation. Compared with common silicon dioxide and aluminum oxide, the mesoporous molecular sieve SBA-15 has obvious advantages as a catalyst carrier, and has excellent physicochemical properties, larger specific surface area and ordered pore structure, so that the dispersion of metal can be effectively improved, and the catalytic performance of the mesoporous molecular sieve SBA-15 is improved. In addition, the nonionic surfactant is adopted as the template agent in the preparation process, so that the acting force between the formed micelle and the silicon precursor is reduced, a thicker pore wall can be formed, and the structure of the SBA-15 is further enabled to be realizedThe stability is improved, and the thermal and hydrothermal stability of the catalyst is further improved.

At present, methanation catalysts are mostly prepared by coprecipitation or common impregnation methods, and the uniform distribution of active components can not be basically realized. Patent CN105709741A discloses a preparation method capable of distributing active components in an eggshell, and the CO conversion rate of the prepared catalyst can only reach 23.4% at 250 ℃. Patent CN104815662A provides a nano composite methanation catalyst and a preparation method thereof, which uses nano TiO₂With Al₂O₃The composite material is used as a carrier, the nickel-iron alloy is used as an active component, and the catalyst is complex in preparation process, high in cost and not suitable for large-scale production.

Disclosure of Invention

The invention aims to provide a high-dispersion limited-range bimetallic low-temperature methanation catalyst.

The invention also aims to provide a preparation method of the high-dispersion limited-range bimetallic low-temperature methanation catalyst.

The invention further aims to provide application of the high-dispersion limited-range bimetallic low-temperature methanation catalyst in preparation of methane from synthesis gas.

In order to achieve the purpose, the technical scheme adopted by the invention is as follows:

the invention provides a high-dispersion limited-range bimetallic low-temperature methanation catalyst, which takes mesoporous molecular sieve SBA-15 as a carrier, metal Ni as a main active component and at least one of transition metal or rare earth metal as an auxiliary metal; wherein, the content of metal Ni is 5 wt% -20 wt%, the content of auxiliary metal is 0.5 wt% -2 wt%, the rest is mesoporous molecular sieve SBA-15, and the active component nickel and the auxiliary metal exist in the catalyst in the form of alloy.

The mesoporous molecular sieve SBA-15 has stable chemical property, good heat conduction performance and large specific surface area of 600-1000 m²A micropore surface area of 100 to 200m²The pore size is adjustable within 4.6-30 nm, the pore wall is thicker (3-9 nm), and the pore volume can reach 0.8-1.3 cm³Per g, micropore volume of 0.02E0.04cm³(ii) in terms of/g. The mesoporous molecular sieve carrier SBA-15 is a molecular sieve material with a larger pore diameter at present, and the SBA-15 has a larger pore diameter size, a thicker pore wall structure and better hydrothermal stability than the traditional MCM-41 while keeping a highly ordered two-dimensional hexagonal structure, so that the mesoporous molecular sieve carrier has wide potential application prospects in the fields of adsorption, catalysis, biomedicine, new material processing and the like.

The transition metal is selected from at least one of Fe, Mo and Co.

The rare earth metal is selected from at least one of La and Ce.

The specific surface area of the high-dispersion limited-range bimetallic low-temperature methanation catalyst is 600-660 m²Per g, the surface area of the micropores is 60-75 m²The pore volume is 0.85-1 cm³The volume of the micropores is 0.01-0.03 cm³(ii)/g, the pore diameter is 5.5 to 5.7 nm.

The second aspect of the invention also provides a preparation method of the high-dispersion limited-range bimetallic low-temperature methanation catalyst, which comprises the following steps:

dissolving nickel salt, a metal precursor and an additive in deionized water, wherein the mass ratio of the nickel salt to the metal precursor to the additive to the deionized water is (1-100): 1: (0.1-15): (10-1000), soaking the mesoporous molecular sieve SBA-15 in the mixed solution at room temperature for 2-12 hours, wherein the mesoporous molecular sieve SBA-15 accounts for 1-90% of deionized water by mass percent, vacuum drying is carried out at the temperature of 30-80 ℃ for 5-12 hours, roasting is carried out at the temperature of 400-800 ℃ for 1-10 hours, and cooling and grinding are carried out to obtain the bimetallic low-temperature methanation catalyst.

The nickel salt is at least one of nickel chloride, nickel sulfate, nickel acetate, nickel oxalate and nickel nitrate.

The metal precursor is a compound containing at least one of the following metals: fe. Mo, Co, La, Ce; specifically, at least one selected from ammonium molybdate, lanthanum nitrate and ferric nitrate.

The additive is at least one of citric acid, Cetyl Trimethyl Ammonium Bromide (CTAB), ethylene glycol, glucose, sorbitol or sodium dodecyl sulfate.

The invention provides application of the high-dispersion limited-range bimetallic low-temperature methanation catalyst in preparation of methane from synthesis gas.

The conditions for preparing methane from the synthesis gas are as follows: the volume space velocity of the synthesis gas is 3000-30000 mL/g.h, the pressure is from normal pressure to 3.0Mpa, the temperature is 200-500 ℃, and H in the synthesis gas₂The ratio of/CO is 2-4.

Due to the adoption of the technical scheme, the invention has the following advantages and beneficial effects:

the high-dispersion limited-range bimetallic low-temperature methanation catalyst provided by the invention shows excellent activity and methane selectivity in the reaction of preparing methane from synthesis gas, the catalyst has activity in a temperature range of 200-500 ℃, the CO conversion rate can reach more than 98% at a low temperature of 250 ℃, and the methane selectivity can reach more than 92%.

The active metal and the assistant metal exist in the form of alloy in the high-dispersion limited-range bimetal low-temperature methanation catalyst provided by the invention, and electron transfer exists between the assistant metal and the active metal, so that the low-temperature catalytic performance of the catalyst is obviously improved, and meanwhile, the high-temperature sintering agglomeration of active components is inhibited by the enhancement of interaction force and the limited-range action of carrier pore channels, so that the catalyst has the advantages of high catalytic activity, good methane selectivity, good thermal stability, long service life of the catalyst and the like; the prepared catalyst can reach the CO conversion rate of 100 percent and the methane selectivity of 96 percent at the low temperature of 250 ℃, and has great industrial prospect.

According to the high-dispersion limited-range bimetallic low-temperature methanation catalyst provided by the invention, in the preparation process of the catalyst, the additive is added, so that the size of active component particles can be reduced, the active component particles are uniformly dispersed in pore channels of a carrier, and the limitation effect can prevent the active component particles from sintering, so that the dispersion of the active component particles is improved, and the activity and the stability of the catalyst are finally improved; the catalyst has the advantages of simple and easy preparation method, higher performance and larger advantage in cost performance, and is suitable for industrial large-scale production.

The high-dispersion limited-range bimetallic low-temperature methanation catalyst provided by the invention improves the utilization rate of active components, so that the catalyst has good catalytic performance at low temperature, and meanwhile, the prepared catalyst has excellent high-temperature resistance and long-term stability, is simple in preparation process, and is suitable for industrial large-scale production.

Drawings

FIG. 1 is a HRTEM-EDS spectrum of a bimetallic low-temperature methanation catalyst Mo-Ni/S15-CA prepared in example 1 of the invention, wherein the left-hand side shows the structure of the catalyst and the distribution of active metals, black particles are active metals, and the right-hand side shows the energy spectrum diagram which shows the elements present in the left-hand side.

FIG. 2 is a HRTEM-EDS spectrum of La-Ni/S15-EG prepared by the bimetallic low-temperature methanation catalyst of example 2 of the present invention, wherein the left graph shows the structure of the catalyst and the distribution of active metals, black particles are active metals, and the right graph is a spectrum graph showing elements present in the left graph.

FIG. 3 is an HRTEM-EDS spectrum of a bimetallic low-temperature methanation catalyst Fe-Ni/S15-CTAB prepared in example 3 of the present invention, wherein the left-hand side shows the structure of the catalyst and the distribution of active metals, the black particles are active metals, and the right-hand side shows the energy spectrum diagram, which shows the elements present in the left-hand side.

FIG. 4 is a comparative schematic of the low temperature methanation performance of the catalysts prepared in examples 1-3 and comparative example 1 of this invention in example 4.

FIG. 5 is an HRTEM spectrum of the bimetallic low-temperature methanation catalyst in example 5 of the invention after the bimetallic low-temperature methanation catalyst Mo-Ni/S15-CA prepared in example 1 is tested for high temperature resistance in the reaction of preparing methane from synthesis gas.

FIG. 6 is an HRTEM spectrum of the bimetallic low-temperature methanation catalyst in example 5 of the invention after the bimetallic low-temperature methanation catalyst La-Ni/S15-EG prepared in example 2 is used for testing high-temperature resistance in a reaction for preparing methane from synthesis gas.

FIG. 7 is an HRTEM spectrum of the bimetallic low-temperature methanation catalyst after the bimetallic low-temperature methanation catalyst Fe-Ni/S15-CTAB prepared in example 5 is used for testing high-temperature resistance in a reaction for preparing methane from synthesis gas.

Detailed Description

In order to more clearly illustrate the invention, the invention is further described below in connection with preferred embodiments. It is to be understood by persons skilled in the art that the following detailed description is illustrative and not restrictive, and is not to be taken as limiting the scope of the invention.

The experimental procedures, in which specific conditions are not noted in the following examples, are generally carried out under conventional conditions or conditions recommended by the manufacturers.