铂、钯蜂窝催化剂高温老化对甲醇深度氧化的影响

本研究对铂、钯蜂窝催化剂及分别添加助化剂CeO_2或WO_3,并于500℃、700℃、900℃或1100℃下经受热老化4h后,考察催化剂比表面、晶相结构及其对甲醇深度氧化活性、产物分布及反应动力学网络变化的情况。实验证明,添加CeO_2后,降低了铂催化剂的耐高温性能,但对钯催化剂无明显影响。添加WO_3,降低了钯催化剂对甲醇的氧化活性。经X-线衍射分析证明,在1100℃高温下,WO_3与堇青石载体中的氧化镁和氧化钙发生强相互作用,生成了相应的钨酸盐。甲醇氧化反应动力学研究表明,甲醇在新鲜和高温热老化的铂催化剂上,反应动力学网络表示式是有区别的。

INFLUENCE OF HIGH TEMPERATURE AGING ON Pt AND Pd HONEYCOMB CATALYSTS FOR DEEP OXIDATION OF METHANOL

Honeycomb catalysts of Pt and PD, with and without CeO₂ or WO₃ as promoter, were treated thermally at 500°C, 700°C, 900°C and 1100°C for 4 hours respectively. The changes in catalyst specific surface area, crystallized structure, catalytic activity towards methanol oxidation, products distribution and the reaction kinetics network were studied. It was showed that the addition of CeO₂ to the Pt catalyst decreased its high temperature stability but with less effect on Pd Catalyst. Addition of WO₃ to Pd catalyst suppressed its activity towards methanol oxidation. Tungstates were formed through strong interaction of WO₃ with MgO and CaO from cordierite support as determined by X-Ray diffraction. The study on reaction kinetics for methanol oxidation on the fresh and high temperature aged Pt catalyst showed that the expression in kinetics network was changed.