球磨法制备NiO/MgAl2O4催化剂用于低浓度甲烷催化燃烧

Preparation of NiO/MgAl2O4 catalysts by ball-milling method for catalytic lean burn of high-diluted methane

摘要:

用球磨法制备了MgAl2O4尖晶石负载的NiO催化剂，考察了镍源、NiO负载量、球料比、球磨转速、焙烧温度对低浓度甲烷催化燃烧的影响，并用H2-TPR、BET、XRD、SEM等手段对催化剂进行了表征。结果表明：与沉淀-沉积法或浸渍法相比，球磨法制备的催化剂前驱体与载体的相互作用较弱，焙烧后生成了高活性NiO物种。球磨法制备时，镍盐种类及其负载量、球料比、转速，以及焙烧温度均会改变载体表面NiO晶粒的大小和结合状态，从而影响其活性。以乙酸镍为镍源、NiO质量分数10%、球料比2∶1、球磨转速400 r/min、经700℃焙烧，制得的NiO/MgAl2O4催化剂稳定性和活性较好；600℃下测得拟一级反应速率常数k600为0.489 L/(g·s)，高于MgAl2O4尖晶石负载的La0.8Ca0.2FeO3或La0.8Sr0.2MnO3钙钛矿催化剂。

Abstract:

NiO catalysts supported on MgAl2O4 spinel were prepared by ball-milling method, and the effects of Ni source, NiO loading, ball-to-powder ratio, ball-milling speed and calcination temperature on catalytic lean burn of high-diluted methane were investigated with instruments like H2-TPR, BET, XRD and SEM, etc. Weaker interaction between the Ni precursor and carrier was found in catalysts prepared by ball-milling than by impregnation or deposition-precipitation, to produce the NiO species with higher catalytic activity after calcination. In ball milling, the factors of Ni source and loading, ball-to-powder ratio and ball-milling speed, and calcination temperature as well, all can affect catalytic performance by altering the grain size or bonding state of NiO species on carrier surface. The NiO/MgAl2O4 catalyst prepared from nickel acetate with 10% in mass fraction of NiO loading, ball-milled at ball-to-powder ratio of 2∶1 and 400 r/min, and calcined at 700℃ has demonstrated better stability and activity, and its pseudo first-order reaction rate constant at 600℃ was 0.489 L/(g·s), which is higher than that of La0.8Ca0.2FeO3 or La0.8Sr0.2MnO3 perovskite supported on MgAl2O4 spinel.