介孔Al2O3负载PdO催化甲烷燃烧反应性能

Mesoporous Alumina Supported PdO Catalysts for Catalytic Combustion of Methane

采用浸渍法制备了介孔Al2O3(M-Al2O3)负载PdO催化剂,考察了其催化CH4燃烧反应性能.结果表明,以M-Al2O3为载体的PdO催化剂活性比普通Al2O3载体高得多,这很可能与M-Al2O3的孔道结构对PdO物种的限域作用有关.随着PdO/M-Al2O3催化剂焙烧温度的升高,甲烷催化燃烧活性先增加后降低,其中700oC焙烧的催化剂活性最高,400oC反应时CH4转化率为91%.此时Pd物种主要以PdO颗粒形式高度分散在载体的介孔孔道内,而高温焙烧时,Pd物种主要以Pd和PdO的混合晶相存在.尽管900oC焙烧制得的催化剂上CH4的转化率降低,但TOF值最大,这可能与该催化剂中同时存在金属Pd和PdO有关.

Pd catalysts supported on mesoporous alumina （M-Al2O3） were prepared by an impregnation method and tested for CH4 catalytic combustion. PdO/M-Al2O3 was more active than the PdO catalyst supported on conventional Al2O3 because of a higher dispersion of PdO species induced by the mesoporous structure of M-Al2O3. Moreover, with increasing calcination temperature, the conversion of CH4 over PdO/M-Al2O3 catalysts first increased and then decreased. The best catalytic performance was obtained on the PdO/M-Al2O3 catalyst calcined at 700 oC, with a CH4 conversion of 91% at 400 oC. Pd species were mainly in mesoporous channels of the support in the form of highly dispersed PdO particles. When calcined at higher temperature, Pd species were in forms of crystalline Pd and PdO. A decline of reactivity and a higher turnover frequency were obtained on the PdO/M-Al2O3 catalyst calcined at 900 oC, which might be due to the co-existence of metallic Pd and PdO in the catalyst.