Preparation method for preparing methane dry reforming catalyst through ethanol plasma modification and application

Abstract

The invention discloses a preparation method and application of a methane dry reforming catalyst prepared through ethanol plasma modification, particularly relates to a catalyst for converting two main greenhouse gases of CO2 and CH4 into synthesis gas with the ratio of CO to H2 being 1, and belongs to the field of waste gas treatment technologies and environment-friendly catalytic environments. The preparation method comprises the following steps: firstly, adding a proper amount of H2O into metered Ni (NO3) 2.6 H2O (the mass percent of an active component Ni in the catalyst is 10%) to dissolve the Ni (NO3) 2.6 H2O to obtain a transparent solution; adding the weighed and metered MCM-41 molecular sieve carrier into the obtained transparent solution, uniformly stirring to obtain mixed slurry, and dipping for 45 minutes; drying in a water bath in a constant-temperature heating magnetic stirrer at 80 DEG C, taking out, and drying in a drying oven at 110 DEG C for 12 hours; and putting the obtained product into a radio frequency plasma processing area for activation, the discharge power of the plasma is 200W, the processing atmosphere is EA, and the Ni / M-P (EA) catalyst is obtained. The Ni / M-P (EA) catalyst prepared by the invention has excellent catalytic activity, stability and carbon deposition resistance, and the preparation method is simple in process, easy to operate, short in time consumption and low in cost.

Description

Technical Field

[0001] The present invention relates to a preparation method and application of a methane dry reforming catalyst prepared by ethanol plasma modification, specifically, CO 2 and CH 4 The two main greenhouse gases are converted into CO and H 2 The invention discloses a catalyst for synthesis gas with a ratio of 1, belonging to the field of waste gas treatment technology and environmental catalytic environment. Background Art

[0002] As a large amount of greenhouse gas CO 2 The emission of CO2 has caused global warming and serious environmental problems. In addition, burning fossil fuels is unsustainable due to limited resources. Therefore, storing or recycling CO2 is a 2 Used to produce fuels or chemicals, it is possible to achieve CO 2 The emission reduction target may also produce chemicals that can replace fossil fuels, which can not only reduce greenhouse gas emissions but also alleviate the energy crisis.

[0003] Methane dry reforming is currently the most promising CO 2 Using one of the technologies, CH 4 and CO 2 Two greenhouse gases generate CO and H 2 The ratio is 1 to synthesis gas, which has bilateral advantages in mitigating global warming and providing high value-added chemicals. Therefore, the development of high-activity and high-stability methane dry reforming catalysts is the current research purpose.

[0004] The catalyst for the DRM reaction is mainly Ni-based catalyst, because its catalytic activity is comparable to that of precious metals and its reserves are abundant. However, Ni-based catalysts are prone to sintering and carbon deposition during high-temperature reactions, which causes the catalyst to deactivate rapidly. This is the biggest challenge in the industrialization of Ni-based catalysts for methane dry reforming. Therefore, how to improve the reforming stability and anti-carbon deposition performance of Ni-based catalysts is currently a hot topic in the field of methane dry reforming. Tian et al. used the sol-gel method and calcined at 550°C for 6h to obtain MCM-41 mesoporous molecular sieves. Then, using this as a carrier, the ethanol impregnation method was used to prepare the loaded active component Ni, and a series of Ni were obtained by calcining at 550°C for 4h. X / MCM-41 catalyst and applied it to DRM reaction. in&out / MCM-41 catalyst has good reforming activity and stability at 700°C, but the preparation process is costly, complex, energy-intensive and time-consuming, which is not conducive to industrialization.

[0005] The design idea of ​​this patent is to prepare a supported Ni-based catalyst with strong metal-carrier interaction, high dispersion and small particle size. The literature reports that the MCM-41 mesoporous molecular sieve with high specific surface area is used as a carrier to improve the dispersion and make the Ni-based catalyst active and stable. However, the stability of the catalyst is poor. The literature also reports that the introduction of plasma during the preparation process can significantly improve the dispersion of the catalyst and reduce the particle size of Ni particles. It was thought that good dispersion and smaller Ni particle size can significantly improve the reforming performance of the catalyst, but the reality is that the catalyst has high activity and poor stability. The literature reports that the ethanol modified catalyst has a strong promoting performance, but it was found that the stability of the catalyst is still unsatisfactory. Summary of the invention

[0007] The purpose of the present invention is to develop a preparation method with low cost, simple preparation process, green environmental protection and excellent reforming performance. This patent introduces ethanol into a supported Ni-based catalyst by radio frequency plasma, and studies the effect of the simultaneous action of plasma and ethanol on the structure, reforming activity and stability of the Ni-based catalyst. With Ni as the active component and MCM-41 as the carrier, the plasma grafting technology vaporizes the ethanol and simultaneously bombards it with radio frequency plasma. The two jointly enhance the modified Ni-based catalyst, and it is found that the activity and stability of the catalyst activated by different alcohols are significantly different, so the alcohol atmosphere (EA, EG, NPA, IPA) is optimized, and finally the Ni-based catalyst with the best reforming performance is obtained. Compared with the basic Ni / MC catalyst, the initial CH of the Ni / MP (EA) catalyst at 700°C is 4 The conversion rate was 80.98% (increased by 9.46%), and the initial CO 2 The conversion rate was 83.39% (increased by 12.12%), and the CO yield was 68.39% (increased by 8.42%). The 20h DRM stability test showed that after 20h of high temperature reaction, the CH 4 The conversion rate only dropped to 2.62%.

[0008] To achieve the above purpose, the technical solution adopted by the present invention is:

[0009] A method for preparing a methane dry reforming catalyst by ethanol plasma modification comprises the following steps:

[0010] (1) Weigh the active component Ni(NO 3 ) 2 6H 2 O, add 30 ml HO 2 O or EA solution, stirring until completely dissolved to obtain a transparent solution;

[0011] (2) adding a measured amount of MCM-41 molecular sieve carrier to the transparent solution obtained in step (1), and stirring to obtain a mixed slurry;

[0012] (3) soaking the mixed slurry obtained in step (2) for 45 minutes;

[0013] (4) adding a magnetic stirrer to the mixed slurry obtained in step (3), and rotating and stirring in a constant temperature heated magnetic stirrer until the mixture is evaporated to dryness to form a powder;

[0014] (5) placing the powder obtained in step (4) in an oven and drying overnight to obtain a green powder;

[0015] (6) The powder obtained in step (5) is placed in a muffle furnace, calcined, and naturally cooled to room temperature, or placed in a radio frequency plasma device for treatment, pressed into tablets, and ground into catalysts with a size of 20 to 40 mesh, thereby obtaining a methane dry reforming catalyst.

[0016] According to the above scheme, the activation method is baking or radio frequency (RF) plasma.

[0017] According to the above scheme, the solvent is deionized water or ethanol solution.

[0018] According to the above scheme, the treatment time of the RF plasma is 1 hour and the power is 200W.

[0019] According to the above scheme, the RF plasma treatment atmosphere is N 2 , EA, EG, NPA and IPA.

[0020] According to the above scheme, the mass percentage of the carrier is 100%, and the mass percentage of the active component Ni is 10%.

[0021] According to the above scheme, the carrier is MCM-41 molecular sieve.

[0022] According to the above scheme, the stirring temperature is 80°C;

[0023] Preferably, the drying temperature is 110°C;

[0024] The drying time is 12h;

[0025] The calcination temperature is 550°C;

[0026] The calcination time is 4 hours.

[0027] The present invention also provides the use of a methane dry reforming catalyst prepared by the preparation method described in any one of the above technical solutions in carbon dioxide conversion.

[0028] Compared with the prior art, the technical solution of the present invention brings the following beneficial technical effects:

[0029] 1. The Ni-based catalyst prepared by the conventional impregnation method using ethanol plasma enhanced modification is used for methane dry reforming reaction, and its activity is significantly improved compared with the basic Ni-based catalyst. At 700°C, the initial CH 4 and CO 2 The conversion rates reached 80.98% and 83.39% respectively, which was higher than the initial CH 4 and CO 2 The 20h DRM stability test showed that after 20h of high temperature reaction, CH 4 The conversion rate was only reduced by 2.62%, showing excellent stability.

[0030] 2. Use ethanol plasma instead of traditional calcination to activate Ni-based catalysts in a green and efficient manner;

[0031] 3. Ni / MP(EA) catalyst was prepared by "impregnation + plasma treatment". This preparation method has simple process, short time and low cost. It has high activity and good stability for methane dry reforming reaction. It can also be used for methanation and other reactions and is suitable for industrial production.

[0032] Figure 1 The catalytic performance test diagram of the catalysts prepared in Examples 1, 2 and 4.

[0033] Figure 2 The catalytic performance test diagram of the catalysts prepared in Examples 1, 3 and 4.

[0034] Figure 3 The catalytic performance test chart of the catalysts prepared in Examples 1, 4, 5, 6 and 7.

[0035] Figure 4 The XRD spectra of the catalysts prepared in Examples 1, 2 and 4 are shown.

[0036] Figure 5 H is the catalyst prepared in Example 1, Example 2 and Example 4. 2 -TPR curve graph.

[0037] Figure 6 The XPS spectra of the catalysts prepared in Examples 1, 2 and 4 are shown. DETAILED DESCRIPTION

[0038] The present invention will be further described below through some implementation examples, but the present invention is not limited thereto.

[0039] Example 1

[0040] The preparation steps for methane dry reforming catalyst are as follows:

[0041] Weigh 0.991 g of Ni(NO 3 ) 2 6H 2 O in a beaker, add 30 ml of H 2 After O is dissolved, 1.8g MCM-41 molecular sieve is added, and after impregnation at room temperature for 45min, it is dried in a water bath in a constant temperature heated magnetic stirrer at 80°C, and then taken out and placed in a 110°C oven for drying for 12h; it is placed in a muffle furnace and calcined in an air atmosphere at 550°C for 4h, and the calcined powder is crushed into 20-40 meshes by a tablet press at a pressure of 8Mp, thereby obtaining a Ni / MC catalyst.

[0042] Catalyst Evaluation

[0043] The stability evaluation of the catalyst was carried out in a self-made continuous flow fixed bed reactor. The reaction tube was a quartz tube with an inner diameter of 6 mm and a length of 33 cm. The reaction temperature was measured by a thermocouple placed in the middle of the reaction tube and controlled by a program temperature controller. The gas flow was controlled by a mass flow meter with an air velocity of 36000 ml / (h·g cat ), reaction raw gas: 24.0ml / min CH 4 , 27.7ml / min CO 2 In the experiment, the catalyst dosage was 0.1 g, the reaction temperature was 700 °C, and samples were taken every half an hour. The gas composition of the reactants and products was analyzed by a profile gas chromatograph (SC3000B) to calculate CH 4 and CO 2 The catalyst reacted with CH at different time points. 4 and CO 2 The conversion curve is as follows Figure 1 As shown, CH 4 and CO 2 The initial conversion rates are shown in Table 1.

[0044] Example 2

[0045] Compared with Example 1, only the activation method is different, and the other processes are the same as Example 1. Specifically, 0.991 g of Ni(NO 3 ) 2 6H 2 O in a beaker, add 30 ml of H 2After dissolving it, 1.8 g MCM-41 molecular sieve was added, and it was immersed at room temperature for 45 min, and then dried in a water bath in a constant temperature heating magnetic stirrer at 80 ° C, and then taken out and placed in a 110 ° C oven for drying for 12 h; it was placed in a plasma treatment area for activation for 1 h, the plasma discharge power was 200 W, and the treatment atmosphere was N 2 The catalyst composition of Example 2 is shown in Table 1.

[0046] Catalyst Evaluation

[0047] According to the evaluation method of Example 1, the catalyst reacted with CH 4 and CO 2 The conversion curve is as follows Figure 1 As shown, CH 4 and CO 2 The initial conversion rates are shown in Table 1.

[0048] Example 3

[0049] Compared with Example 1, only the solvent is different, and the other processes are the same as Example 1, as follows: weigh 0.991g of Ni(NO 3 ) 2 6H 2 O was placed in a beaker, 30 ml of EA solution was added to dissolve it, and then 1.8 g of MCM-41 molecular sieve was added, and the mixture was immersed for 45 min, and dried in a water bath in a magnetic stirrer with constant temperature heating at 80 ° C, and then taken out and placed in an oven at 110 ° C for 12 h; the mixture was placed in a muffle furnace and calcined at 550 ° C in an air atmosphere for 4 h, and the calcined powder was crushed into 20-40 meshes by a tablet press at a pressure of 8 Mp to obtain a Ni / M-EA-C catalyst.

[0050] Catalyst Evaluation

[0051] According to the evaluation method of Example 1, the catalyst reacted with CH 4 and CO 2 The conversion curve is as follows Figure 2 As shown, CH 4 and CO 2 The initial conversion rates are shown in Table 1.

[0052] Embodiment 4-7

[0053] Compared with Example 1, only the activation method is different, and the other processes are the same as Example 1. Specifically, 0.991 g of Ni(NO 3 ) 2 6H 2 O in a beaker, add 30 ml of H 2After dissolving it, add 1.8g MCM-41 molecular sieve, soak at room temperature for 45min, dry it in a water bath in a constant temperature heated magnetic stirrer at 80℃, then take it out and place it in a 110℃ oven to dry for 12h; gasify the alcohol with a plasma grafting instrument and pass it into the radio frequency plasma treatment area. At the same time, place the dried catalyst precursor in the plasma treatment area for activation for 1h, the plasma discharge power is 200W, and the treatment atmosphere is alcohol, so that Ni / MP(X) catalyst is obtained. The catalyst compositions of Examples 4 to 7 are shown in Table 1.

[0054] Catalyst Evaluation

[0055] According to the evaluation method of Example 1, the catalyst reacted with CH 4 and CO 2 The conversion curve is as follows Figure 3 As shown, CH 4 and CO 2 The initial conversion rates are shown in Table 1.

[0056] Example Molecular sieve catalyst composition table:

[0057] Specific examples of molecular sieve catalyst processing parameters and activity evaluation are shown in Table 1:

[0058] Stability Evaluation of Molecular Sieve Catalysts

[0059] The catalytic performance of the catalyst was evaluated in a self-made continuous flow fixed bed reactor. The reaction tube was a quartz tube with an inner diameter of 6 mm and a length of 33 cm. The reaction temperature was measured by a thermocouple placed in the middle of the reaction tube and controlled by a program temperature controller. The gas flow was controlled by a mass flow meter with an air velocity of 36000 ml / (h·g cat ), reaction raw gas: 24.0ml / min CH 4 , 27.7ml / min CO 2 In the experiment, the catalyst dosage was 0.1 g, the reaction temperature was 700°C, and samples were taken every half an hour for a total of 20 hours. The gas composition of the reactants and products was analyzed by a profile gas chromatograph (SC3000B). The catalytic performance curves of the catalysts prepared in Examples 1, 2, 3, 4, 5, 6 and 7 at different time points are shown in the figure below: Figure 1 , Figure 2 as well as Figure 3 shown.

[0060] The specific catalyst stability evaluation results are shown in Table 2:

[0061] XRD characterization

[0062] The XRD curves of the catalysts activated by different plasma atmospheres before the reaction are shown in Figure 2. Figure 4 As shown, the peak at 2θ = 22° is amorphous SiO 2 Characteristic diffraction peaks, Ni / MC catalysts have obvious NiO characteristic diffraction peaks at 2θ=37.2°, 43.3°, 62.9°, 75.4° and 79.4° [PDF#47-1049]. Compared with conventional Ni / MC catalysts, the intensity of characteristic diffraction peaks of plasma-activated Ni-based catalysts is significantly reduced, and the peaks are almost invisible, indicating that the introduction of plasma can significantly improve the dispersion of Ni particles on the carrier surface, making NiO highly dispersed on the surface of MCM-41 carrier or in an amorphous form, reducing the crystallinity of the catalyst, thereby reducing the particle size of Ni particles.

[0063] H 2 -TPR Characterization

[0064] H of catalysts activated by different plasma atmospheres before reaction 2 -TPR curve diagram Figure 4 As shown in Figure 2, the Ni / MC catalyst has H at both 357℃ and 505℃. 2 Reduction peaks correspond to medium and strong metal-support interactions, respectively. Compared with Ni / MC catalysts, all reduction peaks of plasma-activated Ni-based catalysts shift to low temperatures, and the area of ​​medium-temperature reduction peaks increases significantly, indicating that plasma can enhance the metal-support interaction. In addition, a new low-temperature reduction peak appears, which has a weak interaction force and is easy to reduce. This shows that while plasma enhances the metal-support interaction of the catalyst, it also improves the reducibility of the catalyst, provides more active sites for the reaction, and improves the reforming performance of the catalyst. Among them, the catalyst activated by ethanol plasma has the highest reduction degree, indicating that the catalyst has good reforming performance.

[0065] XPS characterization

[0066] XPS spectra of catalysts activated by different plasma atmospheres before reaction are shown in Figure 2. Figure 5 As shown. In Ni 2p 3 / 2 In the energy spectrum, Ni of Ni / MC catalyst 2+ The main peaks are at 854.63eV and 856.49eV, and the peak near 863eV belongs to Ni 2+Compared with Ni / MC catalyst, the binding energy of plasma-activated Ni-based catalysts moves upward, among which the binding energy of Ni / MP(EA) catalyst is the highest. This indicates that alcohol plasma bombardment of the catalyst surface is conducive to the movement of electrons from Ni species to the support, and Ni is confined in the support, which improves the metal-support interaction of the catalyst, which is consistent with the H 2 -TPR results are consistent. In addition, in the O1s spectrum, all catalysts have three peaks related to oxygen, namely hydroxyl (O III ), adsorbed oxygen or surface hydroxyl groups (O II ) and lattice oxygen (O I ). Compared with Ni / MC catalyst, the adsorbed oxygen of catalysts activated by alcohol plasma increased, among which Ni / MP(EA) catalyst had the highest adsorbed oxygen. This indicates that alcohol plasma bombarded the catalyst surface with high-energy electrons, breaking the Si-O bond. It also indirectly indicates that hydroxyl groups were successfully introduced, increasing the adsorbed oxygen content and enhancing CO 2 The adsorption capacity is beneficial to inhibit the formation of carbon deposits, thereby improving the stability of the catalyst.

Claims

1. A method for preparing a methane dry reforming catalyst by ethanol plasma modification and its application, characterized in that: The method comprises the following steps: (1) Weigh the active component Ni(NO3)2·6H2O in a stoichiometric ratio, add 30 ml of H2O or EA solution, and stir until it is completely dissolved to obtain a transparent solution; (2) adding a measured amount of MCM-41 molecular sieve carrier to the transparent solution obtained in step (1) to obtain a mixed slurry; (3) soaking the mixed slurry obtained in step (2) for 45 minutes; (4) adding a magnetic stirrer to the mixed slurry obtained in step (3), and rotating and stirring in a constant temperature heated magnetic stirrer until the mixture is evaporated to dryness to form a powder; (5) placing the powder obtained in step (4) in an oven and drying overnight to obtain a green powder; (6) The powder obtained in step (5) is placed in a muffle furnace, calcined, and naturally cooled to room temperature, or placed in a radio frequency plasma device for treatment, pressed into tablets, and ground into catalysts with a size of 20 to 40 mesh, thereby obtaining a methane dry reforming catalyst.

2. The method for preparing a methane dry reforming catalyst by ethanol plasma modification according to claim 1-1, characterized in that: The activation method is baking or radio frequency (RF) plasma.

3. The method for preparing a methane dry reforming catalyst by ethanol plasma modification according to claim 1-2, characterized in that: The solvent is H2O or EA.

4. The method for preparing a methane dry reforming catalyst by ethanol plasma modification according to claims 1-3, characterized in that: The treatment time of the radio frequency plasma is 1 hour, and the power is 200W.

5. The method for preparing a methane dry reforming catalyst by ethanol plasma modification according to any one of claims 1 to 4, characterized in that: The carrier is MCM-41 molecular sieve.

6. The method for preparing a methane dry reforming catalyst by ethanol plasma modification according to any one of claims 1 to 5, characterized in that: The mass percentage of the carrier is 100%, and the mass percentage of the active component Ni is 10%.

7. The method for preparing a methane dry reforming catalyst by ethanol plasma modification according to any one of claims 1 to 6, characterized in that: The plasma treatment atmospheres were N2, EA, EG, NPA and IPA.

8. The method for preparing a methane dry reforming catalyst by ethanol plasma modification according to any one of claims 1 to 7, characterized in that: The stirring temperature is 80° C.; the drying temperature is 110° C.; and the drying time is 12 hours.

9. Use of the methane dry reforming catalyst prepared by ethanol plasma modification according to any one of claims 1 to 8 in CO2 conversion.

Images