Research On The Reaction Of NO Reduction By CO Over Ag-Co/CeO₂ Catalyst

Using CeO₂ as the support, silver as catalyst and cobalt as promoter, a new material: Ag-Co/CeO₂ is preparaed and tested in the catalytic removal reaction of NO and CO simultaneously. The effects of the preparation method of support , silver loading, mole ratio of silver to cobalt, GHSV and oxygen on the catalytic activity of Ag-Co/CeO₂ were investigated and some useful conclusions show as follows:1. Preparation methods have great effect on the catalytic activities. CeO₂ prepared by homogeneous precipitation method with urea as precipitator is superior.2. Addition of silver to CeO₂ greatly decreases the "light-off"temperature of NO-CO reaction, and the addition of cobalt improves the activity of Ag/CeO₂ at high temperature greatly. Ag-Co/CeO₂ catalyst has better activity in a broader temperature window due to the synergetic effect of silver and cobalt.3. Ag-Co/CeO₂ catalyst has good activity and durability in the absence or presence of stoichimetric oxygen system (GHSV=120 000 h^-1;300℃, NO conversion is 100%;the activity did not decrease even after 50 h).4.The state of silver species on CeO₂ was investigated by XRD and temperature programmed decomposition of AgNO₃ on CeO₂, the results indicate when silver loading is below 4 wt.%, silver can be highly dispersed on CeO₂, and there is not silver congregate in bulk phase;but once the silver loading is above 7 wt.%, it will form silver cluster, which will grow up with silver loading increase. Based on the reaction resluts, only the silver cluster whthin certain size, the catalyst exhibits best.