“双溶剂”浸渍法制备Cu/ZnO/MCM-41催化剂及其在CO_2加氢中的催化性能
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摘要
以"双溶剂"浸渍法制备Cu/ZnO/MCM-41催化剂,考察其在CO_2中的催化性能.结果表明,浸渍过程中加入适量的乙二醇,形成"水-乙二醇"双溶剂,可以促进金属离子进入MCM-41载体孔道,形成较小的金属颗粒并均匀镶嵌在MCM-41孔道内. H_2程序升温还原(H2-temperature program reduction, H_2-TPR)具有相对较低的还原温度,说明还原后催化剂中Cu与ZnO有较强的相互作用,并且高度分散.使用该方法制备的Cu/ZnO/MCM-41催化剂在CO_2加氢制备甲醇反应中表现出稳定的催化性能.通过调整负载量控制Cu颗粒粒径,甲醇选择性和产率可达到64.3%和32.8 g·(kgcat)-1·h-1.因此,使用"双溶剂"浸渍法可以促使MCM-41载体限制活性组分迁移与烧结,调控粒径尺寸,从而得到活性组分高度分散、性能稳定的CO_2加氢制备甲醇催化剂.
Cu/ZnO/MCM-41 catalyst was prepared via a double-solvent impregnation method, and its catalytic performance of CO_2 hydrogenation to methanol was investigated. The water-ethylene glycol double solvent formed by adding an appropriate amount of ethylene glycol to the metal nitrate aqueous solution in the impregnation process promoted metal ions into the channels of MCM-41 support, resulting in the formation of metal particles with very small size. Metal particles were uniformly embedded in MCM-41 channels. The relatively low reduction temperature indicated highly dispersed active sites with strong interaction between Cu and ZnO. Cu/ZnO/MCM-41 catalysts prepared with the method had stable catalytic performance in hydrogenation of CO_2 to methanol. By adjusting loading to control the particle size of Cu, the methanol selectivity and yield could reach 64.3% and 32.8 g·(kgcat)~(-1)·h~(-1). Therefore the double-solvent impregnation method can effectively limit migration and sintering of active components with optimized particle size, so as to obtain catalysts with highly dispersed active sites and stable catalytic performance.
Cu/ZnO/MCM-41 catalyst was prepared via a double-solvent impregnation method, and its catalytic performance of CO_2 hydrogenation to methanol was investigated. The water-ethylene glycol double solvent formed by adding an appropriate amount of ethylene glycol to the metal nitrate aqueous solution in the impregnation process promoted metal ions into the channels of MCM-41 support, resulting in the formation of metal particles with very small size. Metal particles were uniformly embedded in MCM-41 channels. The relatively low reduction temperature indicated highly dispersed active sites with strong interaction between Cu and ZnO. Cu/ZnO/MCM-41 catalysts prepared with the method had stable catalytic performance in hydrogenation of CO_2 to methanol. By adjusting loading to control the particle size of Cu, the methanol selectivity and yield could reach 64.3% and 32.8 g·(kgcat)~(-1)·h~(-1). Therefore the double-solvent impregnation method can effectively limit migration and sintering of active components with optimized particle size, so as to obtain catalysts with highly dispersed active sites and stable catalytic performance.
引文
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[3] Prieto G, Concepcion P, Martinez A, et al. New insights into the role of the electronic properties of oxide promoters in Rh-catalyzed selective synthesis of oxygenates from synthesis gas[J]. Journal of Catalysis, 2011, 280(2):274-288.
[4] Lopez H M, Cies J M, Trasobares S, et al. Imaging nanostructural modifications induced by electronic metal support interaction effects at Au/Cerium-based oxide nanointerfaces[J]. ACS Nano, 2012, 6(8):6812-6820.
[5] Torres G H M, Bitter J H, Davidian T, et al. Iron particle size effects for direct production of lower olefins from synthesis gas[J]. Journal of the American Chemical Society, 2012, 134(39):16207-16215.
[6] Cao A, Veser G. Exceptional high-temperature stability through distillation-like selfstabilization in bimetallic nanoparticles[J]. Nature Materials, 2010, 9(1):75-81.
[7] Wang Y, van de Vyver S, Sharma K, et al. Insights into the stability of gold nanoparticles supported on metal oxides for the base-free oxidation of glucose to gluconic acid[J]. Green Chemistry, 2014, 16(2):719-726.
[8] Li F, Yi X D, Fang W P, et al. Effect of organic nickel precursor on the reduction performance and hydrogenation activity of Ni/Al2O3 catalysts[J]. Catalysis Letters, 2009, 130(3/4):335-340.
[9] Nares R, Ramirez J, Gutierrez A A, et al. Characterization and hydrogenation activity of Ni/Si(Al)-MCM-41 catalysts prepared by deposition-precipitation[J]. Industrial and Engineering Chemistry Research, 2009, 48(3):1154-1162.
[10] Bartholomew C H, Pannell R B, Butler J L, et al. Support and crystallite size effects in CO hydrogenation on nickel[J]. Journal of Catalysis, 1980, 65(2):335-347.
[11] Lu J, Fu B, Kung M C, et al. Coking-and sintering-resistant palladium catalysts achieved through atomic layer deposition[J]. Science, 2012, 335(6073):1205-1208.
[12] Prieto G, Zecevic J, Jovana F, et al. Towards stable catalysts by controlling collective properties of supported metal nanoparticles[J]. Nature Materials, 2013, 12(1):34-39.
[13] Richardson J T. Pore size effects on sintering of Ni/Al2O3 catalysts[J]. Journal of Catalysis,1986, 98(2):457-467.
[14] Sun J, Ma D, Zhang H, et al. Toward monodispersed silver nanoparticles with unusual thermal stability[J]. Journal of the American Chemical Society, 2006, 128(49):15756-15764.
[15] Chen J F, Zhang Y R, Tan L, et al. A simple method for preparing the highly dispersed supported Co3O4 on silica support[J]. Industrial and Engineering Chemistry Research, 2011,50(7):4212-4215.
[16] Ho S W, Su Y S. Effects of ethanol impregnation on the properties of silica-supported cobalt catalysts[J]. Journal of Catalysis, 1997, 44(6):591-596.
[17] Behrens M, Studt F, Kasatkin I. The active site of methanol synthesis over Cu/ZnO/Al2O3industrial catalysts[J]. Science, 2012, 336:893-897.
[18] Rasmussen D B, Janssens T V W, Temel B. The energies of formation and mobilities of Cu surface species on Cu and ZnO in methanol and water gas shift atmospheres studied by DFT[J]. Journal of Catalysis, 2012, 293(1):205-214.
[19] Karelovic A, Ruiz P. The role of copper particle size in low pressure methanol synthesis via CO2 hydrogenation over Cu/ZnO catalysts[J]. Catalysis Science and Technology, 2015, 5(2):869-881.
[20] Kresge C T, Leonowicz M E, Roth W J, et al. Ordered mesoporous molecular sieves synthesized by a liquid-crystal template mechanism[J]. Nature, 1992, 359(6397):710-712.
[21] Bore M T, Pham H N, Roth W J, et al. The role of pore size and structure on the thermal stability of gold nanoparticles within mesoporous Silica[J]. The Journal of Physical Chemistry B, 2005, 109(7):2873-2880.
[22] Lei H, Nie R F, Wu G Q, et al. Hydrogenation of CO2 to CH3OH over Cu/ZnO catalysts with different ZnO morphology[J]. Fuel, 2015, 154:161-166.
[23] Arena F, Mezzatesta G, Zafarana G, et al. How oxide carriers control the catalytic functionality of the Cu-ZnO system in the hydrogenation of CO2 to methanol[J]. Catalysis Today,2013, 210(7):39-46.
[24] Prieto G, Shakeri M, de Jong K P, et al. Quantitative relationship between support porosity and the stability of pore-confined metal nanoparticles studied on CuZnO/SiO2 methanol synthesis catalysts[J]. ACS Nano, 2014, 8(3):2522-2531.