Titanium dioxide modified mesoporous nickel catalyst, preparation process and application thereof

Abstract

The present application relates to the technical field of catalyst preparation, in particular to a titanium dioxide modified mesoporous nickel catalyst, a preparation process and application thereof, and the preparation method comprises the following steps: S1, preparation of a titanium dioxide modified mesoporous silica material; S2, adding a nickel-based acidic solution into the titanium dioxide modified mesoporous silica material, after sufficient mixing, ultrasonic treatment for 1h, and standing at room temperature for 24h to carry out an impregnation process, then transferring into an oven, drying at 110 DEG C; S3, grinding the dried solid uniformly, placing the sample in a crucible and transferring into a tube furnace, passing in argon as a protective atmosphere, and increasing the temperature to 550 DEG C at a temperature increasing rate of 1 DEG C / min, and calcining for 6h, so that the titanium dioxide modified mesoporous nickel catalyst is obtained. The present application has high industrialization potential, can replace expensive noble metal catalysts for industrial production, and lays a certain technical foundation for realizing the final industrial production of carbon dioxide methane reforming reaction and integrating the reaction into a green energy storage system.

Description

TECHNICAL FIELD

[0001] The application relates to the technical field of catalyst preparation, in particular to a mesoporous nickel catalyst modified by titanium dioxide, a preparation process and application thereof. BACKGROUND

[0002] The greenhouse effect leads to environmental and social problems such as sea level rise, extreme weather and food production reduction. As the main component of greenhouse gases, carbon dioxide accounts for a large part of greenhouse gas emissions. Therefore, carbon dioxide emission reduction (carbon emission reduction) has become a global consensus. Carbon dioxide catalytic reforming technology (CO2reforming of methane reaction, CO2+CH4=2CO+2H2, CRM) can simultaneously catalytically convert CH4 and CO2, two kinds of greenhouse gases, into high-value synthesis gas (molar ratio close to H2 / CO=1). Therefore, collecting and catalytically converting carbon dioxide in the atmosphere or industrial equipment will be a feasible carbon emission reduction scheme. This process route can be coupled with synthesis gas conversion to simultaneously produce high-value fuels or chemicals such as higher alcohols, olefins and synthetic fuel oil. Thus, carbon cycle or negative carbon cycle can be realized. In addition, by integrating the reaction into a green electricity network, water, light, wind and other green electricity can be directly stored in the form of chemical energy, that is, Power to gas (PtG) project, thereby realizing effective storage and release of renewable energy.

[0003] Nickel-based catalysts have attracted more and more attention in the industry due to their high catalytic performance and low cost. The modification of nickel catalysts currently focuses mainly on the regulation of metal dispersion and the regulation of metal support interface. High metal dispersion can promote the activation and dissociation of CH4 molecules, and the synergistic effect of the metal support interface can improve the activation and dissociation of CO2 molecules. High metal dispersion and metal support interface rich in active sites can inhibit the deposition of a large amount of carbon during the reaction, thereby avoiding the reaction stoppage caused by carbon particle blockage of the catalyst. The high specific surface area and pore volume of mesoporous silica material can help to improve the Ni metal dispersion. Modifying the metal support interface of the metal support interface can improve the alkali site and oxygen vacancy concentration, thereby improving the carbon deposition removal rate. SUMMARY

[0004] In view of the deficiencies of the prior art, the purpose of the present application is to provide a titanium dioxide modified mesoporous nickel catalyst, a preparation process and applications thereof. The catalytic conversion of methane and carbon dioxide to synthesis gas is a kind of reaction with high value. The synthesis gas produced by the reaction can be used to synthesize high-value products such as olefins, fuel oil, higher alcohols, etc. By integrating the reaction into a carbon dioxide comprehensive utilization system, carbon emission reduction and renewable energy storage can be realized at the same time. The nano nickel-based catalyst of the present application has good activity and stability for catalytic conversion of methane and carbon dioxide, and can replace expensive noble metal systems for industrial production. However, the nano nickel catalyst still has problems of nickel grain high-temperature sintering and carbon deposition. Based on the purpose of realizing carbon emission reduction and energy storage, the present application provides a preparation method of a modified silica material supported nano nickel catalyst. By introducing transition metal titanium (Ti) to modify the microstructure of the catalyst surface, the purpose of improving the activity and stability of the catalyst is achieved. The present application lays a foundation for the scaling up of the carbon dioxide catalytic conversion reaction and the integration of the reaction into green energy storage.

[0005] To achieve the above-mentioned purpose, the present application provides the following technical solutions:

[0006] A preparation process of a titanium dioxide modified mesoporous nickel catalyst, comprising the following preparation steps:

[0007] S1. Preparation of a titanium dioxide modified mesoporous silica material:

[0008] S11. Mix 15-20 parts by mass of a template agent with 80-100 parts of an auxiliary organic solvent in a hydrothermal reaction kettle, and continuously stir at a speed of 400-450 r / min at 55℃ for 24 h;

[0009] S12. Adjust the stirring speed to 200-500 r / min, and add 80-100 parts of a titanium-based modification liquid drop by drop, then transfer the reaction kettle to an oven, and continue to react at 85℃ for 48 h;

[0010] S13. After the reaction is completed, hot filtration is performed, and then the material is washed with deionized water and anhydrous ethanol for 3-4 times, dried and ground, transferred to a vacuum tube furnace, heated to 550℃ at a heating rate of 5℃ / min under an argon protective atmosphere with a flow rate of 20 mL / min, and maintained at this temperature for 6 h to obtain a titanium dioxide modified mesoporous silica material;

[0011] S2. Add 80-100 parts of a nickel-based acidic liquid to 55-60 parts of the titanium dioxide modified mesoporous silica material, mix thoroughly, and then ultrasonically treat for 1 h, and then stand at room temperature for 24 h to perform an impregnation process, and then transfer to an oven and dry at 110℃ for 12-24 h;

[0012] S3. After drying, the solid is ground evenly, the sample is placed in a crucible and transferred to a tube furnace, argon is introduced as a protective atmosphere, the temperature is raised to 550℃ at a rate of 1℃ / min, and calcination is carried out for 6h, thereby obtaining a mesoporous nickel catalyst modified by titanium dioxide;

[0013] Preparation of the titanium-based modification liquid includes the following steps:

[0014] S121. 80-100 parts of a titanium source and 80-100 parts of anhydrous ethanol are mixed, and stirred at a speed of 300-350 r / min until completely dissolved, to obtain a titanium source solution;

[0015] S122. 40-50 parts of acetylacetone, 10-15 parts of vinyltriethoxysilane, and 40-50 parts of anhydrous ethanol are mixed, and stirred at a speed of 300-350 r / min until completely dissolved, and then the titanium source solution is added at a dropping speed of 0.5 mL / min;

[0016] S123. 6-8 parts of ethanolamine are diluted in 40-50 parts of anhydrous ethanol, and then added to the mixture obtained in step S122, and stirred at a speed of 450-500 r / min for 1-2h to obtain a titanium-based modification liquid.

[0017] Preferably, the preparation of the auxiliary organic solvent includes the following steps:

[0018] S111. 80-100 parts of an organic mixed solvent, 25-30 parts of deionized water, and 10-13 parts of saturated concentrated hydrochloric acid are mixed, and stirred at a speed of 400-450 r / min for 60-90min under the condition of a 50℃ water bath;

[0019] S112. 20-30 parts of tetraethyl orthosilicate are added to the mixed solution of step S111 at a speed of 2mL / min, and stirring is continued for 25-30min to obtain an auxiliary organic solvent.

[0020] Preferably, the preparation of the nickel-based acidic liquid includes the following steps:

[0021] S21. 20-22 parts of nickel nitrate hexahydrate are added to 70-75 parts of an acidic mixed liquid, and stirred at a speed of 300-400 r / min for 20-30min under the condition of 60℃ to obtain a preliminary mixed liquid;

[0022] S22. 10-12 parts of ethylene glycol and 1.5-2 parts of polyethylene glycol-400 are added to the preliminary mixed liquid, and stirring is continued for 20-25min to obtain a secondary mixed liquid;

[0023] S23. Disperse the mixture from the second step by ultrasonication at a frequency of 40 kHz for 15-20 min, and filter it through a 0.22 μm nylon filter membrane to obtain a nickel-based acidic solution.

[0024] Preferably, the titanium source is selected from one of tetraisopropyl titanate, titanium n-propoxide, or tetrapropyl titanate, and the purity of each is >98%.

[0025] Preferably, the template agent in step S11 is selected from Pluronic F127.

[0026] Preferably, the organic mixed solvent is composed of n-butanol, isopropanol, and isobutanol in a mass ratio of 1:1:1.

[0027] Preferably, the mass concentration of the saturated concentrated hydrochloric acid is 37%.

[0028] Preferably, the acidic mixture consists of citric acid and oxalic acid in a mass ratio of 1:1.

[0029] A titanium dioxide-modified mesoporous nickel catalyst was prepared by the above-described method.

[0030] The above describes the application of a titanium dioxide-modified mesoporous nickel catalyst in the catalytic conversion of carbon dioxide.

[0031] Compared with the prior art, the beneficial effects of the present invention are:

[0032] 1. The titanium-based modified liquid of this invention works synergistically with the auxiliary organic solvent to form a strong metal-carrier interaction, enhance the anchoring ability of Ni, inhibit the sintering of nickel grains at high temperature, and combine with the high specific surface area carrier to provide more active sites.

[0033] 2. The present invention assists the organic solvent and nickel-based acidic liquid to form a dual complex system, optimize the mesoporous structure, increase the specific surface area and pore volume, form a uniform cage-like mesopore, improve nickel dispersion, and achieve high nickel loading.

[0034] 3. The catalyst prepared by this invention has high industrialization potential and can replace expensive precious metal catalysts for industrial production, laying a certain technical foundation for the final industrial production of carbon dioxide methane reforming reaction and the integration of this reaction into green energy storage system. Attached Figure Description

[0035] Figure 1 This is a process flow diagram for preparing the titanium dioxide-modified mesoporous nickel catalyst of the present invention.

[0036] Figure 2 Line graphs showing the CO2 conversion rate of titanium dioxide-modified mesoporous nickel catalysts obtained in Examples 1 and Comparative Examples 1-3 of this invention under high reactant space-time flow rates;

[0037] Figure 3 CH4 conversion rate plot of the titanium dioxide modified mesoporous nickel catalyst obtained in Example 1 and Comparative Examples 1-3 at a high reaction gas hourly space velocity;

[0038] Figure 4 H2 / CO molar ratio plot of the titanium dioxide modified mesoporous nickel catalyst obtained in Example 1 and Comparative Examples 1-3 at a high reaction gas hourly space velocity;

[0039] Figure 5 CO2 conversion rate plot of the titanium dioxide modified mesoporous nickel catalyst obtained in Example 1 and Comparative Examples 1-3 at a low space time flow rate;

[0040] Figure 6 CH4 conversion rate plot of the titanium dioxide modified mesoporous nickel catalyst obtained in Example 1 and Comparative Examples 1-3 at a low space time flow rate;

[0041] Figure 7 H2 / CO molar ratio plot of the titanium dioxide modified mesoporous nickel catalyst obtained in Example 1 and Comparative Examples 1-3 at a low space time flow rate;

[0042] Figure 8 XRD diffraction spectrum of the titanium dioxide modified mesoporous nickel catalyst obtained in Example 1 of the present application;

[0043] Figure 9 Data comparison chart of the titanium dioxide modified mesoporous nickel catalyst obtained in Comparative Example 2 of the present application with a PDF standard card;

[0044] Figure 10 Hydrogen temperature programmed reduction chart (TPR) of the titanium dioxide modified mesoporous nickel catalyst obtained in Example 1 and Comparative Examples 1-3 of the present application;

[0045] Figure 11 Transmission electron microscope spectrum of the titanium dioxide modified mesoporous nickel catalyst obtained in Comparative Example 3 of the present application after a CO2 methane reforming reaction;

[0046] Figure 12 Transmission electron microscope spectrum of the titanium dioxide modified mesoporous nickel catalyst obtained in Example 1 of the present application after a CO2 methane reforming reaction;

[0047] Figure 13 Thermogravimetric analysis chart (TGA) of the titanium dioxide modified mesoporous nickel catalyst obtained in Example 1 and Comparative Examples 1-3 of the present application after a reforming reaction. DETAILED DESCRIPTION

[0048] The present application will be described clearly and completely below in conjunction with the embodiments of the present application. Obviously, the described embodiments are only a part of the embodiments of the present application, rather than all the embodiments. Based on the embodiments in the present application, all the other embodiments obtained by those skilled in the art without creative work fall within the scope of the present application.

[0049] Please refer to Figures 1-13 The present application provides a technical solution:

[0050] The present application uses an improved one-step hydrothermal synthesis process to prepare titanium dioxide modified mesoporous silica nanomaterial, and uses the same as a carrier to load nickel metal on the carrier through a simple preparation process, thereby preparing a titanium dioxide modified nickel catalyst. By adjusting the content of titanium to adjust the metal carrier interface properties and nickel grain dispersion, high-efficiency catalysis of carbon dioxide to produce synthesis gas at low temperature, normal pressure and high flux (WHSV=270000 mL·g cat -1 ∙h -1 ) is realized. The method lays a technical foundation for carbon emission reduction technology and green energy storage process.

[0051] Embodiment 1

[0052] A preparation process of a titanium dioxide modified mesoporous nickel catalyst:

[0053] Before preparing the titanium dioxide modified mesoporous nickel catalyst, an auxiliary organic solvent, a titanium-based modification liquid and a nickel-based acidic liquid are prepared:

[0054] The preparation of the auxiliary organic solvent includes the following steps:

[0055] S111. 80g of an organic mixed solvent (n-butanol, isopropyl alcohol and isobutyl alcohol in a mass ratio of 1:1:1), 25ml of deionized water and 10ml of saturated concentrated hydrochloric acid with a mass concentration of 37% are mixed, and stirred at a speed of 400r / min under the condition of a water bath at 50℃ for 60min;

[0056] S112. 20g of tetraethyl orthosilicate is added to the mixed solution of step S111 at a speed of 2mL / min, and continues to be stirred for 25min to obtain an auxiliary organic solvent;

[0057] The preparation of the titanium-based modification liquid includes the following steps:

[0058] S121. 80g of titanium isopropylate with a purity of 98.5% and 80g of anhydrous ethanol are mixed, and stirred at a speed of 300r / min until completely dissolved to obtain a titanium source solution;

[0059] S122. 40 g acetylacetone, 10 g vinyltriethoxysilane and 40 g anhydrous ethanol were mixed and stirred at a speed of 300 r / min until completely dissolved, and then the titanium source solution was added at a dropping speed of 0.5 mL / min;

[0060] S123. 6 g ethanolamine was diluted in 40 g anhydrous ethanol, and then added to the mixture obtained in step S122, and stirred at a speed of 450 r / min for 1 h to obtain a titanium-based modification solution;

[0061] Preparation of the nickel-based acidic solution included the following steps:

[0062] S21. 20 g nickel nitrate hexahydrate was added to 70 g acidic mixed solution (mass ratio of citric acid to oxalic acid was 1:1), and stirred at a speed of 300 r / min at 60°C for 20 min to obtain a preliminary mixed solution;

[0063] S22. 10 g ethylene glycol and 1.5 g polyethylene glycol-400 were added to the preliminary mixed solution, and continued to be stirred for 20 min to obtain a secondary mixed solution;

[0064] S23. The secondary mixed solution was ultrasonically dispersed at a frequency of 40 kHz for 15 min, and filtered through a 0.22 μm nylon filter membrane to obtain a nickel-based acidic solution;

[0065] S1. Preparation of the titanium dioxide modified mesoporous silica material:

[0066] S11. 15 g template agent Pluronic F127 was mixed with 80 g auxiliary organic solvent in a hydrothermal reactor, and continuously stirred at a speed of 400 r / min at 55°C for 24 h;

[0067] S12. The stirring speed was adjusted to 200 r / min, and 80 g titanium-based modification solution was added dropwise, and then the reactor was transferred to an oven, and continued to react at 85°C for 48 h;

[0068] S13. After the reaction was completed, hot filtration was performed, and then the product was washed with deionized water and anhydrous ethanol for 3 times, dried and ground, and then transferred to a vacuum tube furnace, and heated to 550°C at a heating rate of 5°C / min under an argon protective atmosphere with a flow rate of 20 mL / min, and maintained at this temperature for 6 h to obtain a titanium dioxide modified mesoporous silica material;

[0069] S2. 80 g nickel-based acidic solution was added to 55 g titanium dioxide modified mesoporous silica material, and then ultrasonically treated for 1 h, and then left to stand at room temperature for 24 h to perform an impregnation process, and then transferred to an oven, and dried at 110°C for 12 h;

[0070] S3. After drying, the solid is ground evenly, the sample is placed in a crucible and transferred to a tube furnace, argon is introduced as a protective atmosphere, the temperature is raised to 550℃ at a rate of 1℃ / min, and calcination is carried out for 6h, thereby obtaining a titanium dioxide modified mesoporous nickel catalyst, wherein the content of Ti is 2wt%.

[0071] Example 2

[0072] A preparation process of a titanium dioxide modified mesoporous nickel catalyst:

[0073] Before preparing the titanium dioxide modified mesoporous nickel catalyst, the preparation of an auxiliary organic solvent, a titanium-based modification liquid and a nickel-based acidic liquid is carried out:

[0074] The preparation of the auxiliary organic solvent includes the following steps:

[0075] S111. 100g of an organic mixed solvent (n-butanol, isopropyl alcohol, isobutyl alcohol in a mass ratio of 1:1:1), 30ml of deionized water and 13ml of saturated concentrated hydrochloric acid with a mass concentration of 37% are mixed, and stirred at a speed of 450r / min for 90min under the condition of a 50℃ water bath;

[0076] S112. 30g of tetraethyl orthosilicate is added to the mixed solution of step S111 at a speed of 2mL / min, and stirring is continued for 30min, thereby obtaining an auxiliary organic solvent;

[0077] The preparation of the titanium-based modification liquid includes the following steps:

[0078] S121. 100g of titanium n-propyl alcohol with a purity of 98.5% and 100g of anhydrous ethanol are mixed and stirred at a speed of 350r / min until completely dissolved, thereby obtaining a titanium source solution;

[0079] S122. 50g of acetylacetone, 15g of vinyltriethoxysilane and 50g of anhydrous ethanol are mixed and stirred at a speed of 350r / min until completely dissolved, and then the titanium source solution is added at a dropping speed of 0.5mL / min;

[0080] S123. 8g of ethanolamine is diluted in 50g of anhydrous ethanol, and then added to the mixed solution obtained in step S122, and stirred at a speed of 500r / min for 2h, thereby obtaining a titanium-based modification liquid;

[0081] The preparation of the nickel-based acidic liquid includes the following steps:

[0082] S21. 22g of nickel nitrate hexahydrate is added to 75g of an acidic mixed liquid (citric acid, oxalic acid in a mass ratio of 1:1), and stirred at a speed of 400r / min for 30min under the condition of 60℃, thereby obtaining a preliminary mixed liquid;

[0083] S22. Add 12 g of ethylene glycol and 2 g of polyethylene glycol-400 to the preliminary mixed solution, continue stirring for 25 min, and obtain a secondary mixed solution;

[0084] S23. Ultrasonically disperse the secondary mixed solution at a frequency of 40 kHz for 20 min, filter through a 0.22 μm nylon filter membrane, and obtain a nickel-based acidic solution;

[0085] S1. Preparation of a titanium dioxide modified mesoporous silica material:

[0086] S11. Mix 20 g of a template agent Pluronic F127 with 100 g of an auxiliary organic solvent in a hydrothermal reactor, continuously stir at a speed of 450 r / min at 55°C for 24 h;

[0087] S12. Adjust the stirring speed to 500 r / min, add 100 g of a titanium-based modification solution dropwise, and then transfer the reactor to an oven, and continue to react at 85°C for 48 h;

[0088] S13. After the reaction is completed, hot-filtrate, sequentially wash with deionized water and anhydrous ethanol 4 times, dry and grind, and then transfer to a vacuum tube furnace, and under the protection of an argon atmosphere with a flow rate of 20 mL / min, heat to 550°C at a heating rate of 5°C / min and maintain the temperature for 6 h, to obtain a titanium dioxide modified mesoporous silica material;

[0089] S2. Add 100 g of a nickel-based acidic solution to 60 g of a titanium dioxide modified mesoporous silica material, mix thoroughly, and then ultrasonically treat for 1 h, and then stand at room temperature for 24 h to perform an impregnation process, and then transfer to an oven, and dry at 110°C for 24 h;

[0090] S3. Grind the dried solid uniformly, place the sample in a crucible and transfer to a tube furnace, introduce argon as a protective atmosphere, and heat to 550°C at a heating rate of 1°C / min, and calcine for 6 h, to obtain a titanium dioxide modified mesoporous nickel catalyst.

[0091] Example 3

[0092] A preparation process of a titanium dioxide modified mesoporous nickel catalyst:

[0093] Before preparing the titanium dioxide modified mesoporous nickel catalyst, an auxiliary organic solvent, a titanium-based modification solution, and a nickel-based acidic solution are prepared:

[0094] The preparation of the auxiliary organic solvent includes the following steps:

[0095] S111. 90 g of an organic mixed solvent (mass ratio of n-butanol, isopropyl alcohol, isobutyl alcohol is 1:1:1), 27 ml of deionized water and 11 ml of saturated concentrated hydrochloric acid with a mass concentration of 37% are mixed, and stirred at a speed of 420 r / min for 70 min under the condition of a water bath at 50℃;

[0096] S112. 22 g of tetraethyl orthosilicate is added to the mixed solution of step S111 at a speed of 2 mL / min, and stirring is continued for 27 min to obtain an auxiliary organic solvent;

[0097] The preparation of the titanium-based modification liquid includes the following steps:

[0098] S121. 85 g of tetrapropyl titanate with a purity of 98.5% and 85 g of anhydrous ethanol are mixed and stirred at a speed of 320 r / min until completely dissolved to obtain a titanium source solution;

[0099] S122. 42 g of acetylacetone, 11 g of vinyltriethoxysilane and 42 g of anhydrous ethanol are mixed and stirred at a speed of 320 r / min until completely dissolved, and then added to the titanium source solution at a dropping speed of 0.5 mL / min;

[0100] S123. 7 g of ethanolamine is diluted in 42 g of anhydrous ethanol, and then added to the mixed solution obtained in step S122, and stirred at a speed of 420 r / min for 1.5 h to obtain a titanium-based modification liquid;

[0101] The preparation of the nickel-based acidic liquid includes the following steps:

[0102] S21. 21 g of nickel nitrate hexahydrate is added to 71 g of an acidic mixed liquid (mass ratio of citric acid to oxalic acid is 1:1), and stirred at a speed of 320 r / min for 22 min under the condition of 60℃ to obtain a preliminary mixed liquid;

[0103] S22. 11 g of ethylene glycol and 1.7 g of polyethylene glycol-400 are added to the preliminary mixed liquid, and stirring is continued for 22 min to obtain a secondary mixed liquid;

[0104] S23. The secondary mixed liquid is ultrasonically dispersed at a frequency of 40 kHz for 17 min, and filtered through a 0.22 μm nylon filter membrane to obtain a nickel-based acidic liquid;

[0105] S1. Preparation of titanium dioxide modified mesoporous silica material:

[0106] S11. 17 g of template agent Pluronic F127 is mixed with 85 g of auxiliary organic solvent in a hydrothermal reaction kettle, and stirred at a speed of 420 r / min for 24 h at 55℃;

[0107] S12. Adjust the stirring speed to 300 r / min, and add 85 g of titanium-based modification liquid drop by drop. Then, transfer the reaction kettle to the oven, and continue the reaction at 85°C for 48 h;

[0108] S13. After the reaction is completed, hot filtration is performed. Then, the product is washed with deionized water and anhydrous ethanol for three times, respectively. After drying and grinding, the product is transferred to a vacuum tube furnace. Under the protection of an argon atmosphere with a flow rate of 20 mL / min, the temperature is increased to 550°C at a rate of 5°C / min, and the temperature is maintained for 6 h. Thus, a titanium dioxide modified mesoporous silica material is obtained;

[0109] S2. Add 85 g of nickel-based acidic liquid to 57 g of the titanium dioxide modified mesoporous silica material. After mixing and ultrasonic treatment for 1 h, the product is left to stand at room temperature for 24 h for the impregnation process. Then, the product is transferred to an oven, and dried at 110°C for 15 h;

[0110] S3. After drying, the solid is ground uniformly. The sample is placed in a crucible and transferred to a tube furnace. Argon is introduced as a protective atmosphere. The temperature is increased to 550°C at a rate of 1°C / min, and the product is calcined for 6 h. Thus, a titanium dioxide modified mesoporous nickel catalyst is obtained.

[0111] Example 4

[0112] A preparation process of a titanium dioxide modified mesoporous nickel catalyst:

[0113] Before preparing the titanium dioxide modified mesoporous nickel catalyst, the preparation of an auxiliary organic solvent, a titanium-based modification liquid, and a nickel-based acidic liquid is performed:

[0114] The preparation of the auxiliary organic solvent includes the following steps:

[0115] S111. Mix 95 g of an organic mixed solvent (n-butanol, isopropyl alcohol, and isobutyl alcohol with a mass ratio of 1:1:1), 28 mL of deionized water, and 12 mL of saturated concentrated hydrochloric acid with a mass concentration of 37%. Stir at a speed of 440 r / min for 80 min under the condition of a 50°C water bath;

[0116] S112. Add 28 g of tetraethyl orthosilicate to the mixed solution of step S111 at a rate of 2 mL / min. Continue stirring for 28 min to obtain an auxiliary organic solvent;

[0117] The preparation of the titanium-based modification liquid includes the following steps:

[0118] S121. Mix 95 g of titanium isopropylate with a purity of 98.5% and 95 g of anhydrous ethanol. Stir at a speed of 340 r / min until completely dissolved to obtain a titanium source solution;

[0119] S122. Mix 48 g acetylacetone, 14 g vinyltriethoxysilane and 48 g anhydrous ethanol, stir at a rotation speed of 340 r / min until completely dissolved, then add the titanium source solution at a dropping speed of 0.5 mL / min;

[0120] S123. Dilute 7.5 g ethanolamine in 48 g anhydrous ethanol, then add the mixture obtained in step S122, and stir at a rotation speed of 480 r / min for 1.5 h to obtain a titanium-based modification solution;

[0121] Preparation of the nickel-based acidic solution includes the following steps:

[0122] S21. Add 21.5 g nickel nitrate hexahydrate to 74 g acidic mixed solution (mass ratio of citric acid to oxalic acid is 1:1), stir at a rotation speed of 360 r / min at 60°C for 28 min to obtain a preliminary mixed solution;

[0123] S22. Add 11.5 g ethylene glycol and 1.8 g polyethylene glycol-400 to the preliminary mixed solution, continue to stir for 24 min to obtain a secondary mixed solution;

[0124] S23. Ultrasonically disperse the secondary mixed solution at a frequency of 40 kHz for 18 min, filter through a 0.22 μm nylon filter membrane to obtain a nickel-based acidic solution;

[0125] S1. Preparation of the titanium dioxide modified mesoporous silica material:

[0126] S11. Mix 18 g template agent Pluronic F127 with 95 g auxiliary organic solvent in a hydrothermal reactor, continuously stir at a rotation speed of 440 r / min at 55°C for 24 h;

[0127] S12. Adjust the stirring speed to 350 r / min, add 95 g titanium-based modification solution dropwise, then transfer the reactor to an oven, continue to react at 85°C for 48 h;

[0128] S13. After the reaction is completed, hot filtration is performed, then sequentially wash with deionized water and anhydrous ethanol for 4 times, dry and grind, then transfer to a vacuum tube furnace, under the protection of argon atmosphere with a flow rate of 20 mL / min, heat to 550°C at a heating rate of 5°C / min and maintain the temperature for 6 h to obtain a titanium dioxide modified mesoporous silica material;

[0129] S2. Add 95 g nickel-based acidic solution to 58 g titanium dioxide modified mesoporous silica material, mix thoroughly, then ultrasonically treat for 1 h, then stand at room temperature for 24 h to perform an impregnation process, then transfer to an oven, dry at 110°C for 20 h;

[0130] S3. After drying, the solid is ground evenly, the sample is placed in a crucible and transferred to a tube furnace, argon is introduced as a protective atmosphere, the temperature is raised to 550℃ at a rate of 1℃ / min, and calcination is carried out for 6h, to obtain a mesoporous nickel catalyst modified by titanium dioxide.

[0131] Comparative Example 1

[0132] Comparative Example 1 and Example 1 differ only in that in Comparative Example 1, the amount of titanium-based modification solution is controlled so that the content of Ti is 5wt%, and the remaining steps in Comparative Example 1 and Example 1 are exactly the same.

[0133] Comparative Example 2

[0134] Comparative Example 2 and Example 1 differ only in that in Comparative Example 2, the amount of titanium-based modification solution is controlled so that the content of Ti is 10wt%, and the remaining steps in Comparative Example 2 and Example 1 are exactly the same.

[0135] Comparative Example 3

[0136] Comparative Example 3 and Example 1 differ only in that in Comparative Example 3, the addition of titanium-based modification solution is omitted, and the remaining steps in Comparative Example 3 and Example 1 are exactly the same.

[0137] Comparative Example 4

[0138] Comparative Example 4 and Example 1 differ only in that in Comparative Example 4, the organic mixed solvent is used, and the remaining steps in Comparative Example 4 and Example 1 are exactly the same.

[0139] Comparative Example 5

[0140] Comparative Example 5 and Example 1 differ only in that in Comparative Example 5, the addition of auxiliary organic solvent is omitted, and the remaining steps in Comparative Example 5 and Example 1 are exactly the same.

[0141] Performance test:

[0142] In order to facilitate the naming in the performance test, the mesoporous nickel catalyst modified by titanium dioxide obtained in Example 1 and Comparative Examples 1-3 is named as Ni / S-2Ti, Ni / S-5Ti, Ni / S-10Ti, Ni / S.

[0143] 1. Explore the influence of Ti content, organic mixed solvent, auxiliary organic solvent and titanium-based modification solution on the structural properties of mesoporous silica materials

[0144] The present application statistically analyzes the influence of the composition of the organic mixed solvent, the auxiliary organic solvent and the titanium-based modification liquid on the structural properties of the mesoporous silica material. As can be seen from Table 1, through the testing of the titanium dioxide modified mesoporous nickel catalyst obtained by Example 1 and Comparative Examples 1-5, the solvent of Example 1 can obtain the silica material with the largest specific surface area and pore volume, and the modification of the mesoporous silica material is best when the content of Ti is 2wt%, and the results are as shown in the following Table 1:

[0145] Table 1

[0146]

[0147] 2, Reaction performance test of the titanium dioxide modified mesoporous nickel catalyst in the catalytic conversion of methane and carbon dioxide to synthesis gas

[0148] The catalytic reaction was carried out in a fixed bed micro-reactor. The reaction tube was a micro-straight tube type quartz reaction tube with an inner diameter of 9mm. The titanium dioxide modified mesoporous nickel catalyst particles obtained by Example 1 were loaded in the middle position of the reaction tube. The reaction tube was heated by an electric furnace, and a K-type thermocouple was used to detect the temperature of the catalyst bed, and a temperature controller was used to control the heating rate and temperature. The gas flow was controlled by a high-performance mass flowmeter. After the reaction, the tail gas was dried by a water trap instrument, and then detected by a gas chromatograph equipped with a thermal conductivity cell detector (TCD).

[0149] The mass of the titanium dioxide modified mesoporous nickel catalyst obtained by Example 1 was 20mg, and the space time yield WHSV=270000mL·g cat -1 ·h -1 Before the reaction, the catalyst was reduced at 800℃ for 1h by using a reducing gas (a mixture of hydrogen and argon, H2 / Ar=10 / 95, the flow rate was 100mL / min), so as to reduce the nickel oxide to metal nickel (Ni) and promote the reduction of part of TiO2. After the reduction was completed, the temperature was lowered to room temperature, and the surface of the catalyst was purged with argon, and then the reaction gas was introduced, and the gas composition was a mixture of carbon dioxide, methane and argon (CO2 / CH4 / Ar=30 / 40, the gas flow rate was 100mL / min), and the reaction time was 6h. The space time yield of the raw material gas was WHSV=270000mL·g cat -1 ·h -1 .

[0150] The chemical reaction equation is: CO2+CH4=2CO+2H2;

[0151] The activity calculation method: CO2 conversion rate (X CO2 ), CH4 conversion rate (X CH4 ) and product molar ratio (H2 / CO) are calculated by the following formulas (1)-(3):

[0152] (1) X CO2 (%) = [(CO2)] in -(CO2) out ] / (CO2) in ×100%;

[0153] (2) X CH4 (%) = [(CH4) in -(CH4) out ] / (CH4) in ×100%;

[0154] (3) H2 / CO=(H2) out / (CO) out .

[0155] Appendix Figures 2-4 The activity graphs of the titanium dioxide-modified mesoporous nickel catalysts obtained in Examples 1 and Comparative Examples 1-3 for the catalytic conversion of carbon dioxide into methane under high reactant space-time flow rates are attached. Figures 2-4 (These are line graphs showing the CO2 conversion, CH4 conversion, and H2 / CO molar ratio of the titanium dioxide-modified mesoporous nickel catalysts obtained in Examples 1 and Comparative Examples 1-3 under high reactant space-time flow rates.) Figures 2-4 It can be seen that all catalysts exhibited high catalytic activity at very high reactant space-time flow rates and 800℃. Furthermore, low Ti doping content resulted in the greatest improvement in the activity of the Ni catalyst, while excessively high Ti content was detrimental to catalyst activity. In Example 1, the 2wt% Ti-doped Ni catalyst exhibited the highest CO2 and CH4 conversion rates and the highest H2 / CO molar ratio. Throughout the entire test time (400 min), the 2wt% Ti-doped Ni catalyst also exhibited the highest activity and stability.

[0156] Low-throughput testing: (attached) Figures 5-7 To enable the catalyst to operate at a lower space-time flow rate (GHSV = 12000 h⁻¹) -1 Activity test results under (attached) Figures 5-7 The figures show line graphs of CO2 conversion, CH4 conversion, and H2 / CO molar ratio of the titanium dioxide-modified mesoporous nickel catalysts obtained in Example 1 and Comparative Examples 1-3 at relatively low space-time flow rates. Figures 5-7 It can be seen that both the unadded Ti and Ti-doped catalysts exhibit high reaction conversion rates (over 95%) at 800℃, and the H2 / CO molar ratio is close to 1; meanwhile, the Ti-doped sample exhibits higher activity and stability.

[0157] 3. Material Characterization

[0158] The titanium dioxide modified mesoporous nickel catalysts obtained in Example 1 and Comparative Examples 1-3 and the carrier (titanium dioxide modified mesoporous silica material) obtained in Example 1 were characterized by BET specific surface area analyzer, XRD test, transmission electron microscopy (TEM), and the obtained structures are shown in Table 2 below:

[0159] Table 2

[0160]

[0161] As can be seen from Table 2, the titanium dioxide modified mesoporous nickel catalyst obtained in Example 1 has a high specific surface area and pore volume. The specific surface area and pore volume of the catalyst are obviously decreased compared with the carrier, which is caused by the deposition of Ni and Ti oxides in the pores of the carrier. With the increase of the Ti doping amount, the NiO particles have a decreasing trend, indicating that Ti doping can promote the increase of the dispersion degree of Ni species; the same trend can also be seen from the Ni metal grain size counted from the TEM electron microscope image, and the catalyst after Ti doping has smaller Ni metal particles. In addition, high content of Ti will lead to the generation of NiTiO3 species, which is not conducive to the reactivity of the catalyst.

[0162] Figure 1 Figure 8 Figure 1 is an XRD diffraction spectrum of the titanium dioxide modified mesoporous nickel catalyst obtained in Example 1. As can be seen from the figure, the peak type of the catalyst without Ti doping is relatively sharp, and the results in Table 2 show that the NiO particles are relatively large. With the increase of the Ti content, the peak type of NiO gradually becomes wide, indicating that the NiO particles become smaller, which corresponds to the data in Table 2. By comparing the XRD diffraction spectrum of the catalyst obtained in Comparative Example 2 with the data of the PDF standard card, it can be seen that when the Ti content reaches 10wt%, the diffraction peak of the NiO particles is not obvious, and the NiO grain size cannot be calculated; at the same time, by comparing the PDF standard card, the diffraction peaks of anatase TiO2 and NiTiO3 are detected, and the NiTiO3 grain is as large as 19.6nm. According to the literature and the experimental research of the present application, NiTiO3 is not conducive to the CO2 methane reforming reaction. Figure 9 The titanium dioxide modified mesoporous nickel catalysts obtained in Example 1 and Comparative Examples 1-3 were detected by X-ray photoelectron spectroscopy (XPS), and the data of the molar ratio of elements on the surface of the catalyst and the bonding energy position are shown in Table 3 below:

[0163] Table 3

[0164]

[0165]

[0166] ​As can be seen from Table 3, the Ti doping leads to the rearrangement of Ni species on the support surface. The low content of Ti is highly dispersed on the support surface, which is consistent with the XRD detection results. In addition, the low content of Ti (2 wt%) leads to the high dispersion of Ni on the support surface. Due to the Ti doping, the content of surface active hydroxyl oxygen (-OH) of the catalyst is also increased, and the sample doped with 2 wt% Ti contains the highest content of hydroxyl oxygen. The hydroxyl oxygen has been proved by scientists to be an active component of the carbon dioxide methane reforming reaction. The Ti doping also leads to the change of the Ni2p binding energy position, which indicates that there is a strong interaction between Ni and Ti.

[0167] The Figure 10 The hydrogen temperature programmed reduction (TPR) diagrams of the titanium dioxide modified mesoporous nickel catalysts obtained in Example 1 and Comparative Examples 1-3 are obtained. As can be seen from the diagrams, the reduction peaks are mainly divided into three categories: the α peak represents the surface hydroxyl oxygen, and the β and γ peaks represent the NiO grains of different particle sizes. TiO2 is generally rarely reduced at the test temperature. The Ti doping causes the β and γ peaks of the NiO species to move to the high temperature zone, indicating that the interaction between Ni and the support or TiO2 is enhanced. This is probably caused by the small NiO particles. The small particle NiO existing in the pores of the support is difficult to reduce, and the Ti doping promotes the generation of small particle NiO, thus leading to a higher reduction temperature.

[0168] The hydrogen consumption amounts corresponding to the respective peaks of the titanium dioxide modified mesoporous nickel catalysts obtained in Example 1 and Comparative Examples 1-3 are calculated with the pure CuO sample as a control sample, and the results are as follows in Table 4:

[0169] Table 4 Hydrogen consumption data of the titanium dioxide modified mesoporous nickel catalysts obtained in Example 1 and Comparative Examples 1-3 in the TPR spectrum

[0170]

[0171] As can be seen from Table 4, the low content of Ti (2 wt%) promotes the increase of the hydrogen consumption of the catalyst, indicating that the reducible NiO species is increased. However, too high content of Ti is not conducive to the reduction of the NiO species. The increase of the hydrogen consumption of the α peak indicates the increase of the surface hydroxyl oxygen species.

[0172] The basic site content is determined according to the carbon dioxide temperature programmed desorption diagram (CO2-TPD), and the obtained data are as follows in Table 5:

[0173] Table 5 Basic site distribution calculated from the CO2 temperature programmed desorption (CO2-TPD) spectrum

[0174]

[0175] From Table 5, it can be found that the Ti doping causes the rearrangement of the basic sites on the catalyst surface. The introduction of Ti increases the weak basic sites and the medium strength basic sites, and decreases the strong basic sites. The increase of the weak basic sites and the medium strength basic sites is important for the activation and dissociation of the reaction molecules in the CO2 methane reforming reaction. Therefore, the increase of such basic sites is beneficial to the increase of the activity and stability of the catalyst.

[0176] Figure 2 is a TEM image of the mesoporous nickel catalyst modified by TiO2 according to the present application. Figures 11-12 Figure 3 is a TEM image of the mesoporous nickel catalyst modified by TiO2 according to the present application.

[0177] Figure 4 is a TGA image of the mesoporous nickel catalyst modified by TiO2 according to the present application. Figure 13 Figure 4 is a TGA image of the mesoporous nickel catalyst modified by TiO2 according to the present application.

[0178] While the embodiments of the application have been illustrated and described, it will be understood by those skilled in the art that various changes, modifications, substitutions and alterations can be made therein without departing from the spirit and scope of the application, which is defined by the appended claims and their equivalents.

Claims

1. A process for preparing a titanium dioxide-modified mesoporous nickel catalyst for catalytic reforming of carbon dioxide to syngas, characterized in that, The preparation steps include the following: S1. Preparation of titanium dioxide modified mesoporous silica materials: S11. By mass, mix 15-20 parts of template agent with 80-100 parts of auxiliary organic solvent in a hydrothermal reactor and stir continuously at 55°C and 400-450 r / min for 24 h. S12. Adjust the stirring speed to 200-500 r / min, add 80-100 parts of titanium-based modified liquid dropwise, then transfer the reactor to an oven and continue the reaction at 85℃ for 48 h. S13. After the reaction is complete, filter while hot, wash with deionized water and anhydrous ethanol 3-4 times in sequence, dry and grind, transfer to a vacuum tube furnace, and calcine at 5℃ / min at a heating rate of 5℃ / min under an argon protective atmosphere to obtain titanium dioxide modified mesoporous silica material. S2. Add 80-100 parts of nickel-based acidic liquid to 55-60 parts of titanium dioxide modified mesoporous silica material, mix thoroughly, ultrasonically treat for 1 hour, let stand at room temperature for 24 hours for impregnation, and then transfer to an oven to dry at 110℃ for 12-24 hours. S3. After drying, the solid is ground uniformly. The sample is placed in a crucible and transferred to a tube furnace. Argon gas is introduced as a protective atmosphere, and the temperature is raised to 550℃ at a rate of 1℃ / min. After calcination for 6 hours, titanium dioxide-modified mesoporous nickel catalyst is obtained, in which the Ti content is 2wt%. The preparation of the titanium-based modified liquid includes the following steps: S121. By mass, mix 80-100 parts of titanium source and 80-100 parts of anhydrous ethanol, and stir at 300-350 r / min until completely dissolved to obtain a titanium source solution. S122. Mix 40-50 parts of acetylacetone, 10-15 parts of vinyltriethoxysilane and 40-50 parts of anhydrous ethanol, stir at 300-350 r / min until completely dissolved, and then add to the titanium source solution at a dropping rate of 0.5 mL / min. S123. Dilute 6-8 parts of ethanolamine with 40-50 parts of anhydrous ethanol, then add it to the mixture obtained in step S122, and stir at 450-500 r / min for 1-2 h to obtain titanium-based modified solution. The preparation of the auxiliary organic solvent includes the following steps: S111. By mass, mix 80-100 parts of organic mixed solvent, 25-30 parts of deionized water and 10-13 parts of saturated concentrated hydrochloric acid, and stir at 400-450 r / min for 60-90 min in a water bath at 50℃. S112. Add 20-30 parts of tetraethyl orthosilicate to the mixed solution in step S111 at a rate of 2 mL / min, and continue stirring for 25-30 min to obtain the auxiliary organic solvent; The preparation of the nickel-based acidic solution includes the following steps: S21. By mass, add 20-22 parts of nickel nitrate hexahydrate to 70-75 parts of acidic mixture, and stir at 300-400 r / min for 20-30 min at 60℃ to obtain a preliminary mixture; S22. Add 10-12 parts of ethylene glycol and 1.5-2 parts of polyethylene glycol-400 to the preliminary mixture, and continue stirring for 20-25 minutes to obtain the secondary mixture; S23. The mixture from the second step is ultrasonically dispersed at a frequency of 40kHz for 15-20min, and then filtered through a 0.22μm nylon filter membrane to obtain a nickel-based acidic solution; The organic mixed solvent is composed of n-butanol, isopropanol, and isobutanol in a mass ratio of 1:1:

1.

2. The preparation process of a titanium dioxide-modified mesoporous nickel catalyst for catalytic reforming of carbon dioxide to syngas according to claim 1, characterized in that, The titanium source is selected from one of tetraisopropyl titanate, titanium n-propoxide, or tetrapropyl titanate, and the purity of each is >98%.

3. The preparation process of a titanium dioxide-modified mesoporous nickel catalyst for catalytic reforming of carbon dioxide to syngas according to claim 1, characterized in that, In step S11, the template agent is selected from Pluronic F127.

4. The preparation process of a titanium dioxide-modified mesoporous nickel catalyst for catalytic reforming of carbon dioxide to syngas according to claim 1, characterized in that, The mass concentration of the saturated hydrochloric acid is 37%.

5. The preparation process of a titanium dioxide-modified mesoporous nickel catalyst for catalytic reforming of carbon dioxide to syngas according to claim 1, characterized in that, The acidic mixture consists of citric acid and oxalic acid in a mass ratio of 1:

1.

6. A titanium dioxide-modified mesoporous nickel catalyst for catalytic reforming of carbon dioxide to syngas, characterized in that, The titanium dioxide-modified mesoporous nickel catalyst is prepared by the preparation process described in any one of claims 1-5.

7. The application of the titanium dioxide-modified mesoporous nickel catalyst according to claim 6 in the reforming and conversion of carbon dioxide to syngas.

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