Pd/CeZr/TiO2/Al2O3蜂窝状金属丝网催化剂选择催化还原NOX

采用溶胶-凝胶法和浸渍法制备了Pd/CeZr/TiO2Al2O3蜂窝状金属丝网催化剂,并将其应用于在富氧条件下以丙烯选择催化还原NOx的研究.利用扫描电镜(SEM)分析了钛酸四丁酯的含量以及涂敷次数对TiO2涂层的影响,系统地考察了Pd含量、氧气浓度和空速对蜂窝状金属丝网催化剂催化性能的影响.实验结果表明,采用钛酸四丁酯的含量为20.0%的溶胶,涂敷2次,可以在金属丝网载体上氧化铝涂层表面获得均匀、无皲裂的TiO2涂层;Pd含量在0.23%～1.06%的范围内, NOx的转化率随Pd含量的增加而减小, Pd含量为0.23%时, NOx表现最高的NOx转化率;反应气体中氧气浓度从1.5%增加到6.0%, NOx的转化率随氧气浓度的增加而增大,当氧气浓度高于6.0%, NOx的转化率则随氧气浓度的增加而迅速减小; NOx的转化率随着空速的增加而降低,在高温条件下空速对转化率的影响要大于在低温条件下.

Selective Catalytic Reduction of NOX over Pd/CeZr/TiO2/Al2O3 Wire-Mesh Honeycomb Catalysts

Pd/CeZr/TiO₂/Al₂O₃ wire-mesh honeycomb catalyst was prepared by sol-gel and impregnation. Furthermore, selective catalytic reduction of NO_X over Pd/CeZr/TiO₂/Al₂O₃ wire-mesh honeycomb catalyst with propylene under lean burn condition was studied. The effects of the concentration of tetra-N-butyl titanate and dipcoat cycles on TiO₂ washcoat were studied by SEM, and the effects of Pd concentration, O₂ concentration and gas velocity on catalytic activity were investigated. The experimental results showed that the TiO₂ washcoat on wire-mesh support is even and crack-free when the support is impregnated in 20.0% tetra-N-butyl titanate sol for 2 cycles. The NO_X conversion decreases with Pd concentration increase. When Pd concentration is 0.23%, NO_X conversion is highest. NO_X conversion increases with oxygen concentration increase in the range of 1.5%-6.0%. However, when oxygen concentration is higher than 6.0%, NO_X conversion decreases with increasing oxygen concentration. The NO_X conversion decreases with gas velocity increase and its effect is severer at high temperature than low temperature.