CN117225438A - Nickel-based catalyst and preparation method and application thereof - Google Patents

Abstract

The invention discloses a nickel-based catalyst which is a silicon carbide-supported nickel-indium composite oxide, wherein a silicon carbide carrier is beta phase. The invention also discloses a preparation method and application of the catalyst. Indium promoter in the catalyst of the invention helps CO ₂ Adsorption dissociation of (2) to improve the reaction efficiency; the addition of the indium auxiliary agent can enhance the interaction between the metal and the carrier, and plays roles in stabilizing nickel particles, preventing sintering, resisting carbon deposition and prolonging the service life of the catalyst, so that the prepared nickel-based catalyst has higher stability and no obvious carbon deposition after being used for 100 hours.

Description

Nickel-based catalysts and preparation methods and applications thereof

Technical field

The invention relates to the technical field of catalyst preparation for reforming methane and carbon dioxide to produce synthesis gas, and specifically relates to a nickel-based catalyst and its preparation method and application.

Background technique

Energy and environment are the foundation and driving force for human economic and social development. The adjustment and transformation of energy consumption structure is an important strategic policy for the current global energy and environment industry. Methane carbon dioxide catalytic reforming (DRM) technology can effectively convert two greenhouse gases, _CH4 and _CO2, into important industrial raw materials synthesis gas - _H2 and CO. The produced synthesis gas can be further produced through Fischer-Tropsch synthesis to produce various Liquid fuels and high value-added chemicals, DRM reactions can not only meet energy consumption needs but also alleviate the greenhouse effect, occupying an important energy strategic position in economic and social development.

Literature reports on DRM catalysts began in 1928. Fisher, Tropsch and others reported that transition metals Ni, Co, and Fe had CH ₄ reforming activity. By the late 20th century, the DRM catalyst system was initially established, which can generally be divided into precious metal catalysts such as Ru, Rh, Pd, and Pt and non-noble metal catalysts such as Ni, Co, Fe, and Mo. Noble metal-based catalysts have high activity, but their industrial application is limited by high costs. On the contrary, non-noble metal-based catalysts represented by Ni have advantages in catalytic performance, price and reserves, and have good industrial application prospects. Abdullah et al. reviewed the research progress of Ni-based catalysts in DRM reactions. The authors believe that the anti-carbon deposition performance is a key indicator for evaluating the structure and performance of a Ni-based catalyst. The metal-support interaction force will directly affect the anti-carbon deposition performance of the catalyst. Therefore, the selection of carriers, auxiliaries and reaction conditions is crucial to the construction of Ni-based catalysts.

Contents of the invention

In view of the shortcomings of the existing technology, the first technical problem to be solved by the present invention is to provide a new nickel-based catalyst with strong carbon deposition resistance. The catalyst is used for the methane carbon dioxide reforming to synthesis gas reaction and can meet the needs of the catalyst. The life requirement is that under the conditions of 800°C, normal pressure, and air velocity of 36L·h ^-1 ·g ^-1 , it can remain stable after 100 hours of use without obvious carbon deposition.

The second technical problem to be solved by the present invention is to provide a preparation method for the above-mentioned catalyst.

In order to solve the above-mentioned first technical problem, the nickel-based catalyst provided by the present invention is a silicon carbide supported nickel indium composite oxide, and the silicon carbide carrier is a β phase.

In order to solve the above-mentioned second technical problem, the catalyst of the present invention is prepared by adopting the following technical solution:

1) Dissolve nickel salt and indium salt in organic solvent to prepare a solution.

2) Under full rotation in a rotary evaporator, evenly immerse the β-phase silicon carbide carrier into the solution prepared in step 1) several times.

3) After the impregnation is complete, put it into an oven to dry, and then put it into a muffle furnace for roasting to obtain the nickel-based catalyst of the present invention, that is, the silicon carbide-supported nickel indium composite oxide catalyst.

Preferably, the nickel salt in step 1) is nickel nitrate and its hydrate; the indium salt is indium nitrate and its hydrate.

Preferably, the solvent in step 1) is absolute ethanol.

Preferably, the mass ratio of nickel to indium in step 1) is 10-15:1.

Preferably, the number of impregnations in step 2) is 2 to 4 times.

Preferably, the mass ratio of β-phase silicon carbide to nickel in step 2) is 12 to 18:1.

Preferably, in step 3), the muffle furnace baking temperature is 700-800°C, and the programmed temperature rise rate is 2-3°C/min.

The present invention also provides the application of the above-mentioned nickel-based catalyst in the methane carbon dioxide reforming reaction. The application process is as follows:

The catalyst is loaded into the reaction tube, and reduction and catalytic reforming reactions are performed sequentially on the fixed bed reactor, where the reduction conditions are:

1) Under inert atmosphere, heat up at a certain rate.

2) Pour in hydrogen gas for reduction.

Preferably, nitrogen gas is introduced to provide an inert atmosphere when the temperature is raised in step 1).

Preferably, the heating rate in step 1) is 80-120°C/h.

Preferably, the reduction temperature in step 2) is 550-700°C.

Preferably, the hydrogen flow rate in step 2) is 20-40 ml/min.

The catalytic reforming reaction conditions are: 1) After the reduction, the temperature is raised to 800°C at a certain rate, 2) At 800°C, the gas providing an inert atmosphere is gradually switched to CH ₄ and CO ₂ with a total flow rate of 40 to 120 ml/min. The reforming reaction is carried out with a mixture of gases providing an inert atmosphere.

Preferably, the gas used in step 1) is nitrogen, and the heating rate is 80-120°C/h.

Preferably, the reforming reaction conditions of step 2) are mixed gas CH ₄ :CO ₂ :gas providing an inert atmosphere = 1:1:2, normal pressure.

The results show that under the conditions of 800°C, normal pressure, and space velocity of 36L·h ^-1 ·g ^-1 , the CH ₄ conversion rate is more than 50%, and the CO ₂ conversion rate is more than 70%, and the catalyst has no effect after 100 hours of use. There was obvious carbon deposition, but the catalyst remained stable at this time (after 100 hours of reaction, the CH ₄ conversion rate was 67% and the CO ₂ conversion rate was 72%).

Compared with the existing technology, the advantages and beneficial effects of the technical solution of the present invention are as follows:

(1) The nickel-indium/silicon carbide catalyst has high stability, and the catalyst has no obvious carbon deposits after 100 hours of use.

(2) The indium additive of the present invention contributes to the adsorption and dissociation of CO ₂ and improves reaction efficiency.

(3) The addition of indium additives according to the present invention can enhance the metal-carrier interaction. Therefore, the addition of indium additives can stabilize nickel particles, prevent sintering, resist carbon deposition, and extend the life of the catalyst to a certain extent. role.

Description of drawings

Figure 1 is an X-ray diffraction (XRD) pattern of the nickel-indium/silicon carbide catalyst synthesized in Example 1.

Figure 2 is a high-resolution transmission electron microscope (HR-TEM) photo of the nickel-indium/silicon carbide catalyst synthesized in Example 1.

Figure 3 is the HAADF-STEM and EDS-Mapping images of the nickel-indium/silicon carbide catalyst synthesized in Example 1.

Figure 4 is a hydrogen-temperature programmed reduction (H ₂ -TPR) spectrum of the nickel-indium/silicon carbide catalyst, nickel/silicon carbide catalyst and indium/silicon carbide catalyst synthesized in Examples 1, 3 and 4;

Figure 5 is the experimental result of the catalytic methane carbon dioxide reforming reaction life of the nickel-indium/silicon carbide catalyst in Example 5 at 800°C.

Figure 6 is the experimental result of the catalytic methane carbon dioxide reforming reaction life of the nickel-indium/silicon carbide catalyst (water as solvent) in Example 6 (Comparative Example) at 800°C.

Figure 7 is the experimental result of the methane carbon dioxide reforming reaction life of the nickel/silicon carbide catalyst in Example 7 (Comparative Example) at 800°C.

Figure 8 is the experimental result of the methane carbon dioxide reforming reaction life of the indium/silicon carbide catalyst in Example 8 (Comparative Example) at 800°C.

Figure 9 is the thermogravimetric analysis result of the methane carbon dioxide reforming reaction catalyzed by the nickel-indium/silicon carbide catalyst in Example 5 at 800°C.

Detailed ways

The present invention will be further explained below through the accompanying drawings and specific embodiments. It should be understood that the purpose of the following examples is only to illustrate the technical solutions and technical effects of the present invention, but not to limit the protection scope of the present invention.

Examples 1, 2, 3 and 4 are respectively the preparation of nickel-indium/silicon carbide catalyst, comparative catalyst nickel-indium/silicon carbide catalyst (water as solvent), comparative catalyst nickel/silicon carbide catalyst and comparative catalyst indium/silicon carbide catalyst. Embodiments;

Example 5 is an example to examine the service life of the catalyst prepared in Example 1 when used in the methane carbon dioxide reforming reaction at 800°C;

Examples 6, 7, and 8 (comparative examples) are examples to examine the service life of the catalysts prepared in Examples 2, 3, and 4 when they catalyze the methane carbon dioxide reforming reaction at 800°C.

Example 1

A preparation method of nickel-indium/silicon carbide catalyst, the steps are as follows:

Dissolve 0.446g nickel nitrate hexahydrate and 0.021g hydrated indium nitrate in 2 ml absolute ethanol to obtain an impregnation solution. Under full rotation in a rotary evaporator, 1.40g β-phase silicon carbide carrier is evenly immersed in the above solution three times. , put it into an oven at 80°C to dry for 12h, then put it into a muffle furnace and heat it to 750°C at a rate of 2°C/min for roasting for 5h, to obtain the nickel-indium/silicon carbide catalyst of the present invention, which is recorded as Ni-In/ SiC.

The X-ray diffraction patterns of the nickel-indium/silicon carbide catalyst prepared in this example before and after reduction are shown in Figure 1, the high-resolution transmission electron microscope pictures are shown in Figure 2, and the HAADF-STEM and EDS-Mapping pictures are shown in Figure 3 .

It can be seen from Figure 1 that the fresh catalyst obtained in Example 1 has the characteristic diffraction peak of NiO, which changes into the characteristic diffraction peak of Ni after reduction. As shown in Figure 2, a crystal plane spacing of 0.24nm can be observed in area 1 (the right box area of Figure 2), which belongs to the NiO (111) crystal plane; a 0.26nm spacing can be observed in area 2 (the left box area of Figure 2). The crystal plane spacing belongs to the SiC (111) crystal plane. At the same time, because the content of indium is small, no diffraction peak is observed in the XRD pattern. As shown in Figure 3, indium and nickel are successfully combined to stabilize the nickel particles. According to Figures 2 and 3, it can be seen that in the Ni-In/SiC catalyst synthesized in Example 1, the active metal Ni forms a semi-embedded structure, which enhances the metal-support interaction.

Example 2 (comparative example)

A preparation method of nickel-indium/silicon carbide catalyst, the steps are as follows:

Dissolve 0.446g nickel nitrate hexahydrate and 0.021g hydrated indium nitrate in 2 ml water to obtain an impregnation solution. Under full rotation in a rotary evaporator, 1.40g β-phase silicon carbide carrier is evenly immersed in the above solution three times, and placed Dry in an oven at 80°C for 12h, then put it into a muffle furnace and heat it to 750°C at a rate of 2°C/min for roasting for 5h to obtain the nickel-indium/silicon carbide catalyst of the present invention, which is recorded as Ni-In/SiC (water as a solvent).

Example 3 (comparative example)

A preparation method of nickel/silicon carbide catalyst, the steps are as follows:

Dissolve 0.446g of nickel nitrate hexahydrate in 2ml of absolute ethanol to obtain an impregnation solution. Under full rotation in a rotary evaporator, 1.41g of silicon carbide carrier is evenly immersed in the above solution in multiple batches, and dried in an oven at 80°C. 12h, then put it into a muffle furnace and raise the temperature to 750°C for 5h at a rate of 2°C/min to obtain a nickel/silicon carbide catalyst, which is recorded as Ni/SiC.

Example 4 (comparative example)

A preparation method of indium/silicon carbide catalyst, the steps are as follows:

Dissolve 0.021g hydrated indium nitrate in 2ml absolute ethanol to obtain an impregnation solution. Under full rotation in a rotary evaporator, 1.48g silicon carbide carrier is evenly immersed in the above solution in multiple batches, and placed in an 80°C oven to dry for 12 hours. , then put it into a muffle furnace and heat it to 750°C for 5 hours at a rate of 2°C/min to obtain the indium/silicon carbide catalyst of the present invention, which is recorded as In/SiC.

The hydrogen-temperature programmed reduction spectra of the nickel-indium/silicon carbide catalyst, nickel/silicon carbide catalyst and indium/silicon carbide catalyst prepared in Examples 1, 3 and 4 are shown in Figure 4. The results show that the introduction of indium increases the reduction temperature. , which enhances the interaction between metal and carrier, thereby improving the stability of nickel nanoparticles and increasing the catalyst life.

Example 5

Weigh 0.2g of the Ni-In/SiC catalyst prepared in Example 1 and put it into a reaction tube, and perform reduction and catalytic reforming reactions sequentially on the fixed bed reactor. The reduction conditions are: under _N2 atmosphere, first heat up to 600°C at a rate of 100°C/h, and then reduce at this temperature for 3h in an _H2 atmosphere with a flow rate of 30mL/min; the reforming reaction conditions are: after the reduction is completed Then under an inert atmosphere, the temperature is raised to 800°C at a rate of 100°C/h, and directly at 800°C, N ₂ is gradually switched to a mixed gas with a total flow rate of 120mL/min (CH ₄ :CO ₂ :N ₂ =1:1 :2) Carry out reforming reaction with space velocity of 36L·h ^-1 ·g ^-1 and normal pressure. The products (H ₂ , CO, CO ₂ , CH ₄ ) obtained from the reaction were detected by GC-3000 gas chromatography after passing through the six-way valve. The detector was TCD. The catalytic activity and life of the catalyst at 800°C were examined. The results are shown in Figure 5. shown.

The experimental results are shown in Figure 5, which shows that at a reaction temperature of 800°C, the conversion rate of CH ₄ can reach more than 50% and the conversion rate of CO ₂ can reach more than 70% using the Ni-In/SiC catalyst prepared in the present invention. And it remains stable within 100h (after 100h reaction, the CH ₄ conversion rate is 67% and the CO ₂ conversion rate is 72%). At the same time, from the TG results of the catalyst after the reaction in Figure 9, it can be seen that the catalyst has no obvious carbon deposition after the reaction, that is, Ni -In/SiC catalyst has excellent anti-carbon deposition properties. It can be seen that the Ni-In/SiC catalyst of the present invention can achieve high stability in the methane carbon dioxide reforming reaction.

Example 6 (comparative example)

Weigh 0.2g of the Ni-In/SiC (water as solvent) catalyst prepared in Example 2 and put it into a reaction tube, and perform reduction and catalytic reforming reactions sequentially on the fixed bed reactor. The reduction conditions are: under _N2 atmosphere, first heat up to 600°C at a rate of 100°C/h, and then reduce at this temperature for 3h in an _H2 atmosphere with a flow rate of 30mL/min; the reforming reaction conditions are: after the reduction is completed Then under an inert atmosphere, the temperature is raised to 800°C at a rate of 100°C/h, and directly at 800°C, N ₂ is gradually switched to a mixed gas with a total flow rate of 120mL/min (CH ₄ :CO ₂ :N ₂ =1:1 :2) Carry out reforming reaction with space velocity of 36L·h ^-1 ·g ^-1 and normal pressure. The products (H ₂ , CO, CO ₂ , CH ₄ ) obtained from the reaction were detected by GC-3000 gas chromatography after passing through the six-way valve. The detector was TCD. The catalytic activity and life of the catalyst at 800°C were examined. The results are shown in Figure 6 shown.

The experimental results are shown in Figure 6, which shows that at a reaction temperature of 800°C, the conversion rate of CH ₄ using the catalyst prepared in the present invention reaches about 30%, and the conversion rate of CO ₂ reaches more than 50%, and remains stable within 25 hours, but Compared with the Ni-In/SiC catalyst using ethanol as the solvent, the conversion rate and H ₂ /CO were both reduced.

Example 7 (comparative example)

Weigh 0.2g Ni/SiC catalyst into the reaction tube, and perform reduction and catalytic reforming reactions in the fixed bed reactor in sequence. The reduction conditions are: first raise the temperature to 600°C at a rate of 100°C/h, and then reduce at this temperature for 3h in an _H2 atmosphere with a flow rate of 30mL/min; the reforming reaction conditions are: after the reduction is completed, the temperature is reduced to 100°C/h. The temperature is raised to 800°C at a rate of h, and N ₂ is gradually switched to a mixed gas with a total flow rate of 120mL/min for reforming reaction directly at 800°C, with a space velocity of 36L·h ^-1 ·g ^-1 and normal pressure. The products (H ₂ , CO, CO ₂ , CH ₄ ) obtained from the reaction were detected by GC-3000 gas chromatography after passing through the six-way valve. The detector was TCD. The catalytic activity and life of the catalyst at 800°C were examined. The results are shown in Figure 7 shown.

The results shown in Figure 7 indicate that the comparative catalyst has lower catalytic activity. It is counter-proven that the introduction of indium in the present invention enhances the metal-support interaction and improves the catalytic activity.

Example 8 (comparative example)

Take 0.2g of the In/SiC catalyst and conduct a test to evaluate the activity and life of the catalyst using the same conditions as in Examples 5, 6, and 7. The results are shown in Figure 8. The results showed that the comparative catalyst had no catalytic activity at a reaction temperature of 800°C.

Claims (9)

1. A nickel-based catalyst, characterized in that the nickel-based catalyst is a silicon carbide supported nickel-indium composite oxide, and the silicon carbide carrier is beta phase.

2. A method for preparing a nickel-based catalyst, comprising the steps of:

1) Dissolving nickel salt and indium salt in an organic solvent to prepare a solution;

2) Uniformly dipping the beta-phase silicon carbide carrier into the solution prepared in the step 1) for a plurality of times under the condition of full rotation in a rotary evaporator;

3) And after the impregnation is completed, drying the mixture in an oven, and then roasting the mixture in a muffle furnace to obtain the nickel-based catalyst, namely the silicon carbide-supported nickel-indium composite oxide catalyst.

3. The method for preparing a nickel-based catalyst according to claim 2, wherein the nickel salt in the step 1) is a nitrate of nickel and a hydrate thereof; the indium salt is nitrate of indium and hydrate thereof.

4. A method for preparing a nickel-based catalyst according to claim 2 or 3, wherein the solvent in step 1) is absolute ethanol.

5. A method of preparing a nickel-based catalyst according to claim 2 or 3, wherein the mass ratio of nickel to indium in step 1) is 10 to 15:1.

6. A method of preparing a nickel-based catalyst according to claim 2 or 3, wherein the number of impregnations in step 2) is 2 to 4.

7. A method of preparing a nickel-based catalyst according to claim 2 or 3, wherein the ratio of beta-phase silicon carbide to nickel mass in step 2) is 12-18:1.

8. A method for preparing a nickel-based catalyst according to claim 2 or 3, wherein the muffle furnace baking temperature in step 3) is 700-800 ℃ and the programmed heating rate is 2-3 ℃/min. .

9. Use of the nickel-based catalyst according to claim 1 in a methane carbon dioxide reforming reaction, wherein the use is as follows:

loading a catalyst into a reaction tube, and sequentially carrying out reduction and catalytic reforming reactions on a fixed bed reactor;

wherein the reduction conditions are as follows:

1) Heating at a certain rate in an inert atmosphere;

2) Introducing hydrogen for reduction;

the catalytic reforming reaction conditions are:

1) Heating to 800 ℃ at a certain rate after the reduction is finished;

2) Gradually switching the gas providing inert atmosphere into CH with total flow of 40-120 ml/min at 800 DEG C ₄ 、CO ₂ And a mixture gas of inert atmosphere provided gas is subjected to reforming reaction.