High-stability methanol fuel catalyst and preparation method thereof

Abstract

The present application relates to the field of fuel catalyst, in particular to a high stability methanol fuel catalyst and a preparation method thereof.The composition comprises the following components: TiO2@Al2O3 core-shell carrier, block copolymer P123, 3-aminopropyl triethoxysilane, H2PtCl6.6H2O, ascorbic acid, ethylenediamine and tetraethyl orthosilicate.The present application prepares anatase TiO2 core by weak acid precipitation-calcination method, coats γ-Al2O3 shell by mild hydrolysis, constructs oxygen vacancy electron library and Lewis acid site, induces growth of ordered mesoporous SiO2 shell by P123 template to amino-functionalized carrier, and anchors platinum atom in the pore wall by ethylenediamine complexation, so that the hierarchical structure gives the catalyst high stability, anti-coking and reversible regeneration characteristics.

Description

TECHNICAL FIELD

[0001] The present application relates to the field of fuel catalysts, in particular to a high-stability methanol fuel catalyst and a preparation method thereof. BACKGROUND

[0002] As a liquid hydrogen carrier, the efficient catalytic conversion of methanol is the key to hydrogen energy economy and portable energy systems. Existing catalysts are mainly divided into two categories: methanol reforming catalysts, mainly Cu / ZnO / Al2O3, Pd / ZnO or Pt-based catalysts, which produce hydrogen through methanol steam reforming (MSR) or partial oxidation (POX); DMFC anode catalysts, represented by PtRu / C, which directly catalyze the electrochemical oxidation of methanol. Although the above-mentioned catalysts have achieved industrial application, there are significant bottlenecks in long-term operation stability, and the core problem is concentrated in the sintering and aggregation of active components: high-temperature structural instability: at the reforming reaction temperature (200-350℃), Cu, Pt and other metal nanoparticles undergo Ostwald ripening due to surface energy minimization, resulting in significant increase in particle size (such as Cu / ZnO-Al2O3, which significantly reduces activity after 500 hours of operation at 300℃). The high-temperature phase transition of the carrier (such as γ-Al2O3) to α-Al2O3 causes a sharp decrease in specific surface area, accelerating metal migration and aggregation. Poor tolerance to dynamic conditions: temperature cycling stress (such as 50℃ to 300℃ cycling) caused by frequent start-stop of vehicle-mounted or backup power supply repeatedly damages the metal-carrier interface, particles detach from anchor sites and aggregate. Limitations of anti-sintering strategies: structural additives (such as MgO, ZrO2): only delay the sintering rate, but cannot inhibit long-term thermodynamic-driven deactivation. Alloying (such as PtRu) is costly for noble metals, and Ru is easily dissolved at the anode potential; and the preparation process of core-shell structure (such as underpotential deposition) is complex, difficult to scale up, and the shell layer has insufficient thermal stability. Therefore, it is extremely necessary to develop a methanol fuel catalyst with high anti-sintering property, active site accessibility and scalability. SUMMARY

[0003] In view of the defects of the prior art, the purpose of the present application is to provide a high-stability methanol fuel catalyst and a preparation method thereof.

[0004] The technical effects of the present application are realized by the following technical solution: a high-stability methanol fuel catalyst, which comprises the following components: TiO2@Al2O3 core-shell carrier, block copolymer P123, 3-aminopropyl triethoxysilane, H2PtCl6·6H2O, ascorbic acid, ethylenediamine and tetraethyl orthosilicate.

[0005] Preferably, the preparation of the TiO2@Al2O3 core-shell carrier comprises the following steps:

[0006] S1: TiOSO4 and polyethylene glycol are added to deionized water, ammonia water and H2SO4 solution are added dropwise to adjust pH to 3-3.5, the temperature is increased to 70-90℃, 500 rpm stirring is performed for 3-5 h, 60℃ standing is performed for 10-16 h, centrifugation is performed, 0.05M oxalic acid solution and deionized water are repeatedly washed for 3 times, vacuum freeze drying is performed at-50℃ for 24 h, and then calcination treatment is performed at 400℃ for 2-4 h to obtain anatase TiO2 nanospheres;

[0007] S2: Al(OC3H7)3 is added to anhydrous ethanol, and then acetylacetone is added to inhibit hydrolysis, stirring is performed until complete dissolution to obtain solution A; the anatase TiO2 nanospheres of step S1 are ultrasonically dispersed in anhydrous ethanol to obtain a 20wt% suspension B;

[0008] S3: solution A of step S2 is slowly added dropwise to suspension B at 60℃ at a speed of 1 mL / min, an ethanol solution of 0.1M ammonia water is slowly added dropwise, the pH is controlled to be neutral, after the addition of solution A is completed, stirring is performed for 2-3 h, centrifugation is performed, filtration is performed, aging treatment is performed at 70℃ for 12-16 h, the temperature is increased to 300℃ at a speed of 2℃ / min, and then the temperature is maintained for 1-2 h, the temperature is increased to 500℃ at a speed of 1℃ / min, and then the temperature is maintained for 2-4 h to obtain a TiO2@Al2O3 core-shell carrier;

[0009] Preferably, in step S1, the amount ratio of TiOSO4, polyethylene glycol and deionized water is 0.1 mol: 18-24 g: 350-450 mL;

[0010] Preferably, in step S2, the amount ratio of Al(OC3H7)3, anhydrous ethanol and acetylacetone is 0.1 mol: 400-500 mL: 0.2-0.25 mol;

[0011] Preferably, in step S3, the volume amount ratio of solution A and suspension B is 2:1;

[0012] Preferably, another aspect of the present application is to provide a preparation method of a high-stability methanol fuel catalyst, which specifically comprises the following steps:

[0013] S101: the TiO2@Al2O3 core-shell carrier is added to toluene, 3-aminopropyl triethoxysilane is added dropwise, reflux treatment is performed at 100-120℃ for 5-8 h under a nitrogen atmosphere, ethanol is repeatedly washed to remove 3-aminopropyl triethoxysilane, vacuum drying is performed at 60℃ for 16-24 h to obtain an aminated carrier;

[0014] S102: add block copolymer P123 into 0.5M HCl solution, stir until clear at 40℃, then slowly add tetraethyl orthosilicate at a speed of 0.5-1 mL / min, stir for 2h at 40℃ to form silicic acid oligomers, then add the amino carrier prepared in step S101, ultrasonic treatment to disperse uniformly, react at 60-80℃ for 24-48h, cool and filter, dry at 60℃ for 2-4h, remove the template by gradient calcination to obtain a mesoporous carrier;

[0015] S103: add H2PtCl6·6H2O and ethylenediamine into anhydrous ethanol, stir to dissolve uniformly, then add ascorbic acid and the mesoporous carrier prepared in step S102, ultrasonic / vacuum impregnation treatment, freeze-drying, then stage heating calcination to obtain a catalyst;

[0016] Preferably, in step S101, the ratio of the use amounts of the TiO2@Al2O3 core-shell carrier, toluene and 3-aminopropyltriethoxysilane is 1g:15-20mL:0.1-0.15mL;

[0017] Preferably, in step S102, the ratio of the use amounts of the block copolymer P123, HCl solution, amino carrier and tetraethyl orthosilicate is 0.1-0.15g:2-3mL:1g:0.2-0.3mL;

[0018] Preferably, in step S102, the ultrasonic treatment parameters are: 100-150W, 40kHz, time 20-40min;

[0019] Preferably, in step S102, the gradient calcination parameters are: nitrogen atmosphere, 2℃ / min to 300℃ for 1.5-2.5h, 1℃ / min to 500℃ for 2-4h;

[0020] Preferably, in step S103, the ratio of the use amounts of H2PtCl6·6H2O, ethylenediamine, ascorbic acid, anhydrous ethanol and mesoporous carrier is 0.01-0.012g:0.008-0.01g:0.015-0.02g:5-6mL:1g;

[0021] Preferably, in step S103, the ultrasonic / vacuum impregnation treatment parameters are: temperature 50℃, 200-300W, 40kHz, treatment for 3-5h, then -0.1MPa vacuum, treatment for 1-3h;

[0022] Preferably, in step S103, the freeze-drying parameters are: -80℃ vacuum pre-freezing for 2h, -50℃ vacuum freeze-drying for 24h;

[0023] Preferably, in step S103, the parameters of the stage temperature rising calcination are: 1-1.5 h of treatment at 2℃ / min to 150℃, 1-2 h of treatment at 1℃ / min to 320℃ under nitrogen atmosphere; 1-2 h of treatment at 200-220℃ under nitrogen atmosphere containing 5% hydrogen, and fast cooling to room temperature.

[0024] The beneficial effects of the present application are as follows:

[0025] The present application obtains anatase TiO2 core under weak acid precipitation-calcination conditions, and coats the core with a γ-Al2O3 layer by mild hydrolysis-dehydration, thereby introducing an oxygen vacancy electron pool and a Lewis acid site barrier in a single particle. TiO2 can provide electrons for the subsequent step-by-step oxidation-dehydrogenation of methanol molecules, and the dense Al2O3 helps to isolate the core from the acidic medium and provides weak acid coordination sites for the reactants. 3-aminopropyl triethoxysilane condensed by toluene reflux can build a relatively uniform -NH2 brush layer on the outer surface; the organic layer is substantially removed in the subsequent inert atmosphere calcination, leaving only dense ≡Si-OH end groups. Since the ethylenediamine complexing solution is weakly alkaline, part of the ≡Si-OH is deprotonated to SiO - during the impregnation process, and then coordinates with the planar [Pt(en)2] 2+ to anchor the platinum atoms on the pore wall surface in the N2O2 or O4 mode. The mesoporous SiO2 shell grows in situ through acid-catalyzed hydrolysis-condensation induced by block copolymer P123; the template can be completely removed by calcination at 450-500°C in an atmosphere, and the pores still maintain a high degree of order, ensuring smooth diffusion of reactants and products and providing spatial confinement for platinum active centers. The ligand removal stage should first crack most of the organic skeleton at 200-250°C in a nitrogen atmosphere, then remove residual carbon through short-time oxidation at low oxygen partial pressure, and then restore the platinum to a metallic or low-valence state under H2 / N2 mixed gas conditions. Although this temperature range is not sufficient to produce a complete TiO X coating, limited electron migration can already downshift the platinum d-band center, helping to weaken the Pt-CO bond and thus reduce intermediate poisoning. In long-range reactions, strong coordination-bridge bonds and weak electronic coupling together inhibit the migration and aggregation of platinum atoms; the straight pore channels provided by the mesoporous shell reduce the risk of product retention and local overheating, and provide a certain buffer effect when mechanical oscillation or temperature fluctuations occur. When the catalyst activity decreases due to the running time, the surface oxygen vacancies and pore cleanliness can be restored by low-temperature hydrogen or mild air reprocessing; once carbon deposition occurs, it can also be cleaned online with moderate gas-liquid flushing. In summary, after hierarchical structure design and multiple interface regulation, the catalyst exhibits relatively stable activity, certain anti-poisoning ability, and reversible regeneration characteristics in the methanol conversion environment.

[0026] Specific mechanism, the application firstly through the weak acid hydrolysis, TiOSO4 is decomposed by water to generate metatitanic acid gel TiO(OH)2, and H2SO4 is released; the sulfuric acid in the solution is then neutralized by ammonia water, (NH4)2SO4 by-product is produced, and the pH of the system is adjusted to the range suitable for precipitation. The obtained TiO(OH)2 is converted into anatase TiO2 nanometer core after calcination and dehydration. Then, aluminum isopropoxide is gradually hydrolyzed under the coordination of acetylacetone buffer, Al(OH)3 is first formed, then AlOOH is obtained by low-temperature dehydration, and finally the dehydration and phase transition are completed at about 500°C, and a dense and stable γ-Al2O3 shell layer is constructed. Then, 3-aminopropyltriethoxysilane is condensed with the outer layer hydroxyl to introduce a uniformly distributed -NH2 functional brush on the surface of the particle, providing controllable coordination sites for the subsequent noble metal complex. Through the acid-catalyzed hydrolysis-condensation reaction of tetraethyl orthosilicate, a mesoporous SiO2 shell is in-situ grown on the outer surface; after the removal of the template agent, regular straight pores are left, which lay a spatial foundation for the diffusion of the reactants and the anchoring of monatomic platinum. In the loading stage, platinum chlorate first forms a planar four-coordinated [Pt(en)2] 2+ complex with ethylenediamine; the complex undergoes coordination exchange with the surface -NH2 / deprotonated SiO - sites, and the platinum atom is embedded in the N2O2 planar environment and fixed by bridging two Si-O bonds. After the removal of the organic ligand by heating in an inert atmosphere, the platinum is partially oxidized to a positive state under mild oxygen conditions to form a monatomic site of (≡Si-O)2Pt δ+ , and the Si-O bridge around it still remains, which can inhibit metal migration at a higher temperature. Finally, the platinum can be regulated to a Pt 0 / δ⁺ coexistence state with metal characteristics through low-temperature hydrogen reduction, and the Pt-O-Si anchoring skeleton remains unchanged, providing long-acting and anti-sintering active centers for the electro-thermal conversion reaction of methanol. BRIEF DESCRIPTION OF DRAWINGS

[0027] In order to more clearly illustrate the technical solutions of the present application or the prior art, the following will briefly introduce the drawings needed to be used in the embodiments or prior art description. Obviously, the drawings described below are only a part of the present application, and other drawings can also be obtained by those skilled in the art without any creative effort on the basis of these drawings.

[0028] Figure 1 is a methanol conversion rate test result graph of the catalyst prepared in examples 1-3 and comparative examples 1-3 of the present application;

[0029] Figure 2 is a CO by-product ratio test result graph of the catalyst prepared in examples 1-3 and comparative examples 1-3 of the present application;

[0030] Figure 3is a carbon deposition resistance and regeneration test result diagram of the catalyst prepared in Example 3 and Comparative Examples 1-3 of the present application;

[0031] Figure 4 is a SEM scanning electron microscope diagram of the TiO2@Al2O3 core-shell carrier prepared in Example 3 of the present application. DETAILED DESCRIPTION

[0032] The technical solutions of the present application will be described clearly and completely below in combination 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 of the present application. Based on the embodiments in the present application, all other embodiments obtained by those skilled in the art without creative labor fall within the scope of protection of the present application. It should be noted that, unless otherwise specified, the raw materials involved in the present application are purchased through conventional commercial channels.

[0033] Example 1: A high-stability methanol fuel catalyst, which comprises the following components: TiO2@Al2O3 core-shell carrier, block copolymer P123, 3-aminopropyltriethoxysilane, H2PtCl6·6H2O, ascorbic acid, ethylenediamine and tetraethyl orthosilicate.

[0034] 1. The preparation of the TiO2@Al2O3 core-shell carrier comprises the following steps:

[0035] S1: 0.1 mol of TiOSO4 and 18 g of polyethylene glycol are added to 350 mL of deionized water, an ammonia water and H2SO4 solution are added dropwise to adjust the pH to 3.5, the temperature is increased to 90°C, and the reaction is stirred at 500 rpm for 3 h, 60°C for 10 h, centrifuged, washed with 0.05 M oxalic acid solution and deionized water for 3 times, vacuum freeze-dried at -50°C for 24 h, and then calcined at 400°C for 4 h to obtain anatase TiO2 nanospheres;

[0036] S2: 0.1 mol of Al(OC3H7)3 is added to 400 mL of anhydrous ethanol, and then 0.2 mol of acetylacetone is added to inhibit hydrolysis, and the mixture is stirred until complete dissolution to obtain solution A; 20 g of anatase TiO2 nanospheres from step S1 are ultrasonically dispersed in 100 mL of anhydrous ethanol to obtain a 20 wt% suspension B;

[0037] S3: 200 mL of solution A from step S2 is slowly added dropwise to 100 mL of suspension B at 60°C at a speed of 1 mL / min, a 0.1 M ammonia water in ethanol solution is slowly added dropwise, the pH is controlled to be neutral, the solution A is stirred for 2 h after the addition is completed, centrifuged, filtered, aged at 70°C for 12 h, heated to 300°C at a speed of 2°C / min, kept for 2 h, heated to 500°C at a speed of 1°C / min, and kept for 4 h to obtain the TiO2@Al2O3 core-shell carrier.

[0038] 2. The preparation of a high-stability methanol fuel catalyst comprises the following steps:

[0039] S101: 10 g of TiO2@Al2O3 core-shell carrier is added to 150 mL of toluene, 1 mL of 3-aminopropyl triethoxysilane is added dropwise, and the mixture is treated under reflux at 120°C for 5 h under a nitrogen atmosphere. The 3-aminopropyl triethoxysilane is removed by repeated washing with ethanol, and the mixture is vacuum dried at 60°C for 24 h to obtain an aminated carrier;

[0040] S102: 1 g of block copolymer P123 is added to 20 mL of 0.5M HCl solution, and stirred at 40°C until clear. Then 2 mL of tetraethyl orthosilicate is slowly added dropwise at a rate of 1 mL / min, and the mixture is stirred at 40°C for 2 h to form a silicic acid oligomer. Then 10 g of the aminated carrier prepared in step S101 is added, and the mixture is ultrasonically treated at 100 W and 40 kHz for 40 min to disperse uniformly. The mixture is reacted at 60°C for 48 h, cooled and filtered, and dried at 60°C for 4 h. The mixture is treated at 300°C for 1.5 h at a rate of 2°C / min under a nitrogen atmosphere, and then treated at 500°C for 2 h at a rate of 1°C / min to remove the template to obtain a mesoporous carrier;

[0041] S103: 0.1 g of H2PtCl6·6H2O and 0.08 g of ethylenediamine are added to 50 mL of anhydrous ethanol, and the mixture is stirred to dissolve uniformly. Then 0.15 g of ascorbic acid and 10 g of the mesoporous carrier prepared in step S102 are added, and the mixture is treated at 200 W and 40 kHz for 5 h at a temperature of 50°C. The mixture is then treated under a vacuum of -0.1 MPa for 1 h, pre-frozen at -80°C for 2 h, and vacuum freeze-dried at -50°C for 24 h. The mixture is then treated at 150°C for 1 h at a rate of 2°C / min under a nitrogen atmosphere, and then treated at 320°C for 1 h at a rate of 1°C / min. The mixture is treated at 200°C for 2 h under a nitrogen atmosphere containing 5% hydrogen, and then rapidly cooled to room temperature to obtain a catalyst.

[0042] Example 2: A high-stability methanol fuel catalyst, which comprises the following components: TiO2@Al2O3 core-shell carrier, block copolymer P123, 3-aminopropyl triethoxysilane, H2PtCl6·6H2O, ascorbic acid, ethylenediamine, and tetraethyl orthosilicate.

[0043] 1. The preparation of a TiO2@Al2O3 core-shell carrier comprises the following steps:

[0044] S1: 0.1 mol TiOSO4 and 20 g polyethylene glycol were added to 400 mL of deionized water, and an ammonia water and H2SO4 solution were added dropwise to adjust the pH to 3, the temperature was increased to 70°C, and the reaction was stirred at 500 rpm for 5 h, 60°C for 16 h, centrifuged, washed with 0.05 M oxalic acid solution and deionized water for 3 times, vacuum freeze-dried at -50°C for 24 h, and then calcined at 400°C for 3 h to obtain anatase TiO2 nanospheres;

[0045] S2: 0.1 mol Al(OC3H7)3 was added to 450 mL of anhydrous ethanol, and then 0.22 mol of acetylacetone was added to inhibit hydrolysis, and the mixture was stirred until completely dissolved to obtain solution A; 20 g of anatase TiO2 nanospheres from step S1 were ultrasonically dispersed in 100 mL of anhydrous ethanol to obtain a 20 wt% suspension B;

[0046] S3: 200 mL of solution A from step S2 was slowly added dropwise to 100 mL of suspension B at 60°C at a rate of 1 mL / min, and an ethanol solution of 0.1 M ammonia water was slowly added dropwise to control the pH to be neutral, the solution A was added dropwise for 3 h after the addition was completed, centrifuged, filtered, aged at 70°C for 16 h, heated to 300°C at a rate of 2°C / min, and kept at 300°C for 1.5 h, heated to 500°C at a rate of 1°C / min, and kept at 500°C for 3 h to obtain a TiO2@Al2O3 core-shell carrier;

[0047] 2. Preparation of a high-stability methanol fuel catalyst comprising the following steps:

[0048] S101: 10 g of the TiO2@Al2O3 core-shell carrier was added to 180 mL of toluene, and 1.2 mL of 3-aminopropyltriethoxysilane was added dropwise under a nitrogen atmosphere, and the mixture was refluxed at 100°C for 8 h, and then washed with ethanol to remove the 3-aminopropyltriethoxysilane, and vacuum dried at 60°C for 16 h to obtain an aminated carrier;

[0049] S102: 1.2 g of block copolymer P123 was added to 25 mL of 0.5 M HCl solution, and stirred at 40°C until clear, and then 2.5 mL of tetraethyl orthosilicate was slowly added dropwise at a rate of 0.8 mL / min, and stirred at 40°C for 2 h to form a silicic acid oligomer, and then 10 g of the aminated carrier from step S101 was added, and ultrasonically treated at 130 W and 40 kHz for 20 min, and then dispersed uniformly at 80°C for 24 h, and then cooled and filtered, and dried at 60°C for 2 h, and then treated at 300°C at a rate of 2°C / min for 2.5 h under a nitrogen atmosphere, and then heated to 500°C at a rate of 1°C / min for 4 h to remove the template to obtain a mesoporous carrier;

[0050] S103: 0.11 g H2PtCl6·6H2O and 0.09 g ethylenediamine were added into 55 mL anhydrous ethanol, stirred to dissolve uniformly, then 0.18 g ascorbic acid and 10 g mesoporous carrier prepared in step S102 were added, temperature 50℃, 300 W, 40 kHz, treatment 3 h, then -0.1 MPa vacuum, treatment 3 h, -80℃ vacuum pre-freezing 2 h, -50℃ vacuum freeze-drying 24 h, then nitrogen atmosphere, temperature rising to 150℃ at a speed of 2℃ / min, treatment 1.5 h, temperature rising to 320℃ at a speed of 1℃ / min, treatment 2 h; nitrogen atmosphere containing 5% hydrogen, 220℃ treatment 1 h, rapid cooling to room temperature, to obtain the catalyst.

[0051] Example 3: A high-stability methanol fuel catalyst, the composition of which comprises the following components: TiO2@Al2O3core-shell carrier, block copolymer P123, 3-aminopropyl triethoxysilane, H2PtCl6·6H2O, ascorbic acid, ethylenediamine and tetraethyl orthosilicate.

[0052] 1. The preparation of TiO2@Al2O3core-shell carrier comprises the following steps:

[0053] S1: 0.1 mol TiOSO4 and 24 g polyethylene glycol were added into 450 mL deionized water, ammonia water and H2SO4 solution were added dropwise to adjust pH to 3.2, the temperature was increased to 80℃, and the reaction was stirred at 500 rpm for 4 h, then the solution was left to stand at 60℃ for 12 h, centrifuged, washed with 0.05 M oxalic acid solution and deionized water for 3 times, vacuum freeze-dried at -50℃ for 24 h, then calcined at 400℃ for 2 h, to obtain anatase TiO2nanospheres;

[0054] S2: 0.1 mol Al(OC3H7)3 was added into 500 mL anhydrous ethanol, then 0.25 mol acetylacetone was added to inhibit hydrolysis, and the solution was stirred until completely dissolved to obtain solution A; 20 g anatase TiO2nanospheres prepared in step S1 were ultrasonically dispersed in 100 mL anhydrous ethanol to obtain a 20 wt% suspension B;

[0055] S3: 200 mL solution A prepared in step S2 was slowly added dropwise into 100 mL suspension B at 60℃ at a speed of 1 mL / min, and a 0.1 M ammonia water solution in ethanol was slowly added dropwise to control the pH to be neutral, after the addition of solution A was completed, the solution was stirred for 2.5 h, centrifuged, filtered, and aged at 70℃ for 14 h, then the temperature was raised to 300℃ at a speed of 2℃ / min, and maintained for 1 h, then the temperature was raised to 500℃ at a speed of 1℃ / min, and maintained for 2 h, to obtain TiO2@Al2O3core-shell carrier;

[0056] 2. The preparation of high-stability methanol fuel catalyst comprises the following steps:

[0057] S101: 10 g of TiO2@Al2O3 core-shell carrier was added to 200 mL of toluene, 1.5 mL of 3-aminopropyltriethoxysilane was added dropwise, and the mixture was refluxed at 110°C under a nitrogen atmosphere for 6 h. The 3-aminopropyltriethoxysilane was removed by repeated washing with ethanol, and the mixture was vacuum dried at 60°C for 18 h to obtain an aminated carrier;

[0058] S102: 1.5 g of block copolymer P123 was added to 30 mL of 0.5 M HCl solution, and stirred at 40°C until clear. Then 3 mL of tetraethyl orthosilicate was slowly added dropwise at a rate of 0.5 mL / min, and the mixture was stirred at 40°C for 2 h to form a silicic acid oligomer. Then 10 g of the aminated carrier prepared in step S101 was added, and the mixture was ultrasonically treated at 150 W and 40 kHz for 30 min to disperse uniformly. The mixture was reacted at 70°C for 36 h, cooled and filtered, and dried at 60°C for 3 h. The mixture was treated at 300°C at a rate of 2°C / min under a nitrogen atmosphere for 2 h, and then treated at 500°C at a rate of 1°C / min for 3 h to remove the template to obtain a mesoporous carrier;

[0059] S103: 0.12 g of H2PtCl6·6H2O and 0.1 g of ethylenediamine were added to 60 mL of anhydrous ethanol, and the mixture was stirred until dissolved uniformly. Then 0.02 g of ascorbic acid and 10 g of the mesoporous carrier prepared in step S102 were added, and the mixture was treated at 50°C at 250 W and 40 kHz for 4 h, and then treated at -0.1 MPa vacuum for 2 h. The mixture was pre-frozen at -80°C for 2 h, and then vacuum freeze-dried at -50°C for 24 h. The mixture was then treated at 150°C at a rate of 2°C / min under a nitrogen atmosphere for 1.2 h, and then treated at 320°C at a rate of 1°C / min for 1.5 h. The mixture was treated at 210°C under a nitrogen atmosphere containing 5% hydrogen for 1.5 h, and then rapidly cooled to room temperature to obtain a catalyst.

[0060] Comparative Example 1: The operating procedure parameters of Comparative Example 1 and Example 3 were basically the same, except that CTAB was used instead of block copolymer P123 in Comparative Example 1.

[0061] Comparative Example 2: The operating procedure parameters of Comparative Example 2 and Example 3 were basically the same, except that all operations in step S102 were removed in Comparative Example 2, i.e., the growth of mesoporous SiO2 was removed.

[0062] Comparative Example 3: The operating procedure parameters of Comparative Example 3 and Example 3 were basically the same, except that TiO2 carrier was directly used instead of TiO2@Al2O3 core-shell carrier in Comparative Example 3.

[0063] Performance test:

[0064] Methanol vapor reforming test: 200 mg of the catalyst prepared in Examples 1-3 and Comparative Examples 1-3 was placed in a catalytic bed, 5 vol% H2 / N2 mixed gas was introduced at a rate of 50 mL / min, and the temperature was increased to 220°C at a rate of 10°C / min, and then kept for 1 h, and then cooled to 200°C, and then pure N2 was introduced at a rate of 50 mL / min to replace the residual hydrogen; then, methanol was introduced at a rate of 0.04 mL / min under normal pressure, deionized water was introduced at a rate of 0.034 mL / min by a pump, and nitrogen was introduced at a rate of 30 mL / min, the reaction temperature was 240°C, the methanol conversion rate (%) = (molar flow of methanol entering the reactor - molar flow of unreacted methanol leaving the reactor) / molar flow of methanol entering the reactor x 100%; the CO byproduct ratio (%) = molar flow of CO in the outlet gas / (molar flow of CO2 in the outlet gas + molar flow of CO in the outlet gas) x 100%, three sets of parallel samples were set for each test, the results were averaged, the results were rounded to one decimal place, and the results are shown in Figure 1 and Figure 2 .

[0065] From Figure 1 and Figure 2 It can be seen from the results that the catalyst prepared in the application has excellent performance in methanol conversion, and has a lower CO byproduct ratio, and overall has excellent catalytic performance compared with the comparative examples; from the results of Comparative Example 1 and Example 3, it can be seen that the methanol conversion rate decreases and the CO byproduct ratio increases, which may be due to the fact that CTAB often forms smaller pores of 2-3 nm, and the residual chlorine in the template is easy to corrode the carrier, resulting in partial pore blockage; the decrease in order degree and the increase in diffusion resistance result in a slight decrease in conversion rate; the increase in pore wall defects makes the local high temperature area prone to dehydration to generate CO; from the results of Comparative Example 2 and Example 3, it can be seen that the methanol conversion rate decreases significantly and the CO byproduct ratio increases significantly, which may be due to the fact that the lack of SiO2 leads to a significant decrease in specific surface area, limited Pt dispersion and partial sintering; the lack of SiO - anchor points, insufficient Pt-O-Al / Ti anchoring, and decreased CO removal efficiency; the lack of pores leads to product retention and increased side reactions; from the results of Comparative Example 3 and Example 3, it can be seen that the methanol conversion rate decreases extremely significantly and the CO byproduct ratio increases significantly, which may be due to the fact that only TiO2 carriers are used without the barrier of γ-Al2O3, TiO2 is more easily partially reduced in a high-temperature methanol / water atmosphere, and Pt and TiO2 form weaker SMSI; the decrease in Lewis acid sites makes CO removal dependent on a single Pt site, and both the conversion rate and the CO2 selectivity are impaired; the lack of outer layer confinement leads to more significant Pt sintering and hard carbon formation.

[0066] Acidic cycle stability test: 100 mg of catalyst prepared in Example 3 and Comparative Examples 1-3 was placed in 50 mL of 0.5 M H2SO4 solution and stirred at 50 °C for 12 h, 10 mL of the suspension was taken (labeled the first cycle supernatant), filtered through a 0.22 µm PES filter membrane into an ICP sample bottle, the filter residue was washed with 30 mL of deionized water until the filtrate was neutral; vacuum dried at 60 °C for 4 h, the mass of the residue was measured as m1; the dried catalyst was re- placed into fresh 50 mL of 0.5 M H2SO4 solution and repeated the treatment for 3 cycles; the element loss percentage (%) of each cycle = (the concentration of element i in the filtrate of the nth cycle x the total volume of the filtrate) / (the mass of the catalyst before the first cycle x the theoretical mass fraction of element i in the catalyst) x 100%, three parallel samples were set for each test, the results were averaged and rounded to two decimal places, the results are shown in Table 1 (the percentage is based on the element content measured by ICP total digestion for the first time as 100%; ND indicates that the element itself does not exist in the sample).

[0067] Table 1. Catalyst cycle stability test results

[0068]

[0069] From the results in Table 1, it can be seen that the catalyst prepared in the application has only a small amount of Ti, Al and Pt loss after multiple cycles, and the overall stability is significantly better than that of each comparative sample; from the results of Comparative Example 1 and Example 3, it can be seen that the pore size is reduced and residual Cl - is introduced by replacing P123 with CTAB, which can accelerate the penetration of acid solution, the defects in the pore wall not only accelerate the dissolution of Al 3+ in the γ-Al2O3 layer, but also weaken the coordination of Pt and SiO - , thereby causing the loss rate of Al and Pt to increase at the same time; from the results of Comparative Example 2 and Example 3, it can be seen that the mesoporous SiO2 shell is removed, and Al2O3 is directly exposed to strong acid H2SO4, which causes continuous hydrolysis-dissolution; acid etching proceeds inward to the TiO2 interface, resulting in a significant increase in the loss of Ti and Pt, and the Pt-O-Al bond is particularly fragile due to the lack of SiO - anchoring; from the results of Comparative Example 3 and Example 3, it can be seen that the Al2O3 barrier is missing, and the acid can directly etch the TiO2 surface layer, at this time Pt is mainly fixed by weak electroadsorption or TiO2-x SMSI effect, and the acid desorption resistance is the lowest, showing the largest element loss.

[0070] Anti-carbon deposition and regeneration test: after the methanol reforming reaction, 20vol% CH3OH / 80vol% N2 (anhydrous) is continuously introduced at 300°C (5°C / min heating) for 4h to make the channel easy to generate polymeric carbon; then switch to 5vol% O2 / N2 mixed gas, 240°C for 1h; then 5vol% H2 / N2 mixed gas, 220°C for 30min; repeat the methanol vapor reforming conversion rate test before and after regeneration, calculate the retention rate (%) = steady-state conversion rate after regeneration / initial steady-state conversion rate x 100%, set three parallel samples for each test, take the average value, the result is rounded to one decimal place, and the result is shown in Figure 3 .

[0071] From Figure 3 It can be seen from the results that the catalyst prepared by the application has excellent anti-carbon deposition and regeneration performance; from the results of Comparative Example 1 and Example 3, it can be seen that CTAB is substituted for P123, the pore size is smaller and the distribution is uneven, and part of the hard carbon is not completely oxidized; Cl - Residual causes local Pt sintering, and the activity slightly decreases after regeneration; from the results of Comparative Example 2 and Example 3, it can be seen that the mesoporous SiO2 shell is removed, and the mesoporous confinement is lacking, Pt agglomeration and carbon deposition occur synchronously; the Al2O3 surface carbon layer is thick, and it is difficult to completely remove during oxidation, and the activity recovery is limited; from the results of Comparative Example 3 and Example 3, it can be seen that the Al2O3 barrier is missing, the acid-base sites are insufficient, and Pt exists in the form of large particles, which easily generates a dense carbon skin in dry methanol at 300°C; although part of the carbon is removed by regeneration oxidation, Pt has been significantly sintered, and the activity loss is the largest.

[0072] Spectrum test: take the TiO2@Al2O3 core-shell carrier sample prepared in Example 3, and perform SEM scanning electron microscope test, and the results are shown in Figure 4 .

[0073] From Figure 4 It can be seen from the results that the particles in the picture are basically near-spherical or sub-spherical, and it is difficult to obtain such regular and independent spherical aggregates at this scale by simply sintering TiO2; the surface of each sphere is composed of small bumps, which has a typical orange peel or raspberry texture; this nanometer roughness conforms to the grain assembly texture produced by the hydrolysis and dehydration shrinkage of γ-Al2O3, and the TiO2 core is still shown as an overall gray scale at this magnification, indicating that the shell particles have hidden the core details from the electron beam signal; the surface of the number of spheres is continuous and has no obvious collapse, indicating that the outer Al2O3 and the inner core shrinkage match well; if the shell layer is only physically adsorbed or partially coated, cracks or flaky peeling often occur after calcination.

[0074] While embodiments of the application have been shown and described, it is to be understood that the embodiments described are merely exemplary of the principles and application of the present application. Numerous modifications and adaptions can be effected without departing from the spirit and scope of the present application, which is not limited to the exact construction and arrangement described. It is intended, therefore, to cover all modifications and adaptions that fall within the scope of the claims and their equivalents.

Claims

1. A method for preparing a methanol fuel catalyst, characterized in that, Specifically, the following steps are included: S101: TiO2@Al2O3 core-shell support is added to toluene, 3-aminopropyltriethoxysilane is added dropwise, and the mixture is refluxed under a nitrogen atmosphere. The 3-aminopropyltriethoxysilane is removed by repeated washing with ethanol and then dried under vacuum to obtain the aminated support. S102: Add block copolymer P123 to HCl solution, stir until clear, then slowly add tetraethyl orthosilicate, stir to form silica oligomer, then add the aminated carrier from step S101, sonicate to disperse evenly, heat to react, cool and filter, dry, and gradient calcination to remove the template to obtain mesoporous carrier. S103: Add H2PtCl6·6H2O and ethylenediamine to anhydrous ethanol, stir and dissolve evenly, then add ascorbic acid and the mesoporous support prepared in step S102, ultrasonically / vacuum impregnate, freeze dry, and then calcine at a staged temperature to obtain the catalyst; The preparation of the TiO2@Al2O3 core-shell support includes the following steps: S1: Add TiOSO4 and polyethylene glycol to deionized water, adjust the pH by adding ammonia and H2SO4 solution, increase the temperature, stir the reaction, let it stand, centrifuge, wash repeatedly with oxalic acid solution and deionized water, freeze dry under vacuum, and then calcine to obtain anatase TiO2 nanospheres. S2: Add Al(OC3H7)3 to anhydrous ethanol, then add acetylacetone to inhibit hydrolysis, stir until completely dissolved to obtain solution A; disperse the anatase TiO2 nanospheres from step S1 in anhydrous ethanol by ultrasonication to obtain suspension B; S3: Slowly add solution A from step S2 to suspension B, while simultaneously adding an ethanol solution of ammonia water, keeping the pH neutral. After solution A is added, stir, centrifuge, filter, age, heat and hold, and then heat and hold again to obtain TiO2@Al2O3 core-shell carrier.

2. The method for preparing a methanol fuel catalyst according to claim 1, characterized in that, In step S1, the ratio of TiOSO4, polyethylene glycol, and deionized water is 0.1 mol: 18-24 g: 350-450 mL.

3. The method for preparing a methanol fuel catalyst according to claim 2, characterized in that, In step S2, the ratio of the amounts of Al(OC3H7)3, anhydrous ethanol and acetylacetone is 0.1 mol: 400-500 mL: 0.2-0.25 mol; in step S3, the volume ratio of solution A and suspension B is 2:

1.

4. The method for preparing a methanol fuel catalyst according to claim 3, characterized in that, In step S101, the ratio of the amount of TiO2@Al2O3 core-shell carrier, toluene and 3-aminopropyltriethoxysilane is 1g:15-20mL:0.1-0.15mL.

5. The method for preparing a methanol fuel catalyst according to claim 4, characterized in that, In step S102, the ratio of the amount of the block copolymer P123, HCl solution, aminated carrier and tetraethyl orthosilicate is 0.1-0.15g:2-3mL:1g:0.2-0.3mL.

6. The method for preparing a methanol fuel catalyst according to claim 5, characterized in that, In step S102, the ultrasonic processing parameters are: 100-150W, 40kHz, and 20-40min. The gradient calcination parameters are as follows: under a nitrogen atmosphere, the temperature is increased to 300℃ at a rate of 2℃ / min for 1.5 to 2.5 hours, and then increased to 500℃ at a rate of 1℃ / min for 2 to 4 hours.

7. The method for preparing a methanol fuel catalyst according to claim 6, characterized in that, In step S103, the ratio of the amounts of H2PtCl6·6H2O, ethylenediamine, ascorbic acid, anhydrous ethanol, and mesoporous carrier is 0.01–0.012 g: 0.008–0.01 g: 0.015–0.02 g: 5–6 mL: 1 g; the ultrasonic / vacuum impregnation treatment parameters are: temperature 50°C, 200–300 W, 40 kHz, treatment for 3–5 h, followed by -0.1 MPa vacuum treatment for 1–3 h.

8. The method for preparing a methanol fuel catalyst according to claim 7, characterized in that, In step S103, the freeze-drying parameters are: -80℃ vacuum pre-freezing for 2 hours, -50℃ vacuum freeze-drying for 24 hours; the stage heating and calcination parameters are: under nitrogen atmosphere, heating to 150℃ at a rate of 2℃ / min for 1-1.5 hours, heating to 320℃ at a rate of 1℃ / min for 1-2 hours; under nitrogen atmosphere containing 5% hydrogen, treatment at 200-220℃ for 1-2 hours, and rapid cooling to room temperature.

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