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采用柠檬酸(CA)-浸渍法制备了介孔γ-Al_2O_3(γ-MA)负载的高分散Ni-Ce-Zr氧化物,并将其用于二氧化碳甲烷化反应。研究了柠檬酸加入量对催化剂物理化学性质及催化性能的影响。结果表明,柠檬酸的加入可明显提高Ni-Ce-Zr氧化物在γ-Al_2O_3表面的分散性,同时可以增加镍氧化物与载体间的相互作用。制备材料经氢气还原后得到Ni-Ce-Zr/γ-MA催化剂,镍纳米颗粒均匀分散于γ-Al_2O_3表面。Ni-Ce-Zr/γ-MA催化剂在二氧化碳甲烷化反应中表现出了较高的反应活性和几乎100%的甲烷选择性。反应活性随CA/(Ni+Ce+Zr)摩尔比的增加而增加,主要是由于镍颗粒尺寸的减小和Ni-Ce-ZrO_x物种电子和结构性质的提高。CA/(Ni+Ce+Zr)摩尔比为1的Ni-Ce-Zr/γ-MA催化剂在反应300 h内活性仅降低7%,并且没有明显积碳。表明催化剂在二氧化碳甲烷化反应中具有优异的反应稳定性和抗积碳性能。
Mesoporousγ-Al 2 O 3 (γ-MA) supported highly dispersed Ni-Ce-Zr oxides were prepared by citric acid (CA) -in impregnation method and were used for carbon dioxide methanation. The effects of citric acid addition on the physicochemical properties and catalytic performance of the catalyst were studied. The results show that the addition of citric acid can obviously improve the dispersibility of Ni-Ce-Zr oxide on γ-Al 2 O 3 surface and increase the interaction between nickel oxide and support. The Ni-Ce-Zr / γ-MA catalyst was obtained after the prepared material was reduced by hydrogen, and the nickel nanoparticles were uniformly dispersed on the surface of γ-Al 2 O 3. The Ni-Ce-Zr / γ-MA catalyst showed higher reactivity and almost 100% methane selectivity in the carbon dioxide methanation reaction. The reactivity increased with the increase of the molar ratio of CA / (Ni + Ce + Zr), mainly due to the decrease of nickel particle size and the increase of electron and structure properties of Ni-Ce-ZrO_x species. The activity of Ni-Ce-Zr / γ-MA catalyst with CA / (Ni + Ce + Zr) molar ratio of 1 decreased by only 7% within 300 h and no obvious carbon deposition. It shows that the catalyst has excellent reaction stability and carbon deposition resistance in the carbon dioxide methanation reaction.