焙烧温度对Al2O3载体的性质及其负载的煤制合成气制代用天然气镍基催化剂性能的影响

以拟薄水铝石为前驱体，经不同温度焙烧制得Al₂O₃载体，等体积浸渍法制备Ni/Al₂O₃催化剂，采用X射线衍射、N₂-物理吸附、扫描电镜、程序升温还原等对载体及催化剂进行表征，考察载体焙烧温度对Al₂O₃载体性质及其负载的镍基催化剂催化性能的影响。结果表明，随着焙烧温度的升高，Al₂O₃载体的比表面积减小，平均孔径增大，结晶度升高，晶粒度增大，晶型逐步转变为γ-Al₂O₃［(500~800) ℃］、δ-Al₂O₃［ (900~1 100) ℃］和α-Al₂O₃［(1 250) ℃］。合成气制甲烷催化剂活性变化趋势为:Ni/γ-Al₂O₃>Ni/δ-Al₂O₃>Ni/α-Al₂O₃，其中,800 ℃焙烧的γ-Al₂O₃负载的Ni基催化剂因稳定的晶型结构以及与NiO之间适当的相互作用而表现出最佳的催化活性及稳定性。

Effect of calcination temperature on the properties of Al2O3 support and catalytic performance of nickel-based catalyst for SNG from coal

Using Al₂O₃ as the support obtained by calcining the precursor pseudo-boehmite at different temperatures,Ni/Al₂O₃ catalysts were prepared by impregnation method.The support and the catalysts were characterized by X-ray diffraction,N₂ adsorption-desorption and temperature-programmed reduction by H₂ and scanning electron microscope.The effects of calcination temperature on the properties of Al₂O₃ support and catalytic performance of Ni/Al₂O₃ catalysts for methane synthesis from syngas were investigated.The results showed that the surface area of Al₂O₃ support decreased,average pore diameter,crystallite size and crystallinity increased with the enhancement of calcination temperature.As the calcination temperature increased,the crystal phase of the supports changed obviously.The samples obtained at calcination temperature (500-800) ℃ were γ-Al₂O₃;when the temperature reached (900-1 100) ℃,partial δ-Al₂O₃ was observed;when the temperature was 1 250 ℃, the sample changed to α-Al₂O₃ completely.Ni/γ-Al₂O₃ catalysts showed the highest activity and the best stability than Ni/δ-Al₂O₃ and Ni/α-Al₂O_3.Ni/γ-Al₂O₃ catalyst prepared with γ-Al₂O₃ calcined at 800 ℃ exhibited optimal catalytic activity and stability due to its stability of crystal phase and the appropriate interaction force between γ-Al₂O₃ and NiO.