Catalysis Letters, Vol.112, No.1-2, 69-75, 2006
Single step direct coating of 3-way catalysts on cordierite monolith by solution combustion method: High catalytic activity of Ce0.98Pd0.02O2-delta
A new process of coating of active exhaust catalyst over gamma-Al2O3 coated cordierite honeycomb is reported here. The process consists of (a) growing gamma-Al2O3 on cordierite by solution combustion of Al(NO3)3 and oxylyldihydrazide (ODH) at 600 degrees C and active catalyst phase Ce0.98Pd0.02O2-delta on gamma-Al2O3 coated cordierite again by combustion of ceric ammonium nitrate and ODH with 1.2 x 10(-3) M PdCl2 solution at 500 degrees C. Weight of active catalyst can be varied from 0.02 to 2 wt% which is sufficient but can be loaded even up to 12 wt% by repeating dip dry combustion. Adhesion of catalyst to cordierite surface is via oxide growth which is very strong. About 100% conversion of CO is achieved below 80 degrees C at a space velocity of 880 h(-1). At much higher space velocity of 21,000 h(-1), 100% conversion is obtained below 245 degrees C. Activation energy for CO oxidation is 8.4 kcal/mol. At a space velocity of 880 h(-1) 100% NO conversion is attained below 185 degrees C and 100% conversion of 'HC' C2H2 below 220 degrees C. At same space velocity 3-way catalytic performance over Ce0.98Pd0.02O2-delta coated monolith shows 100% conversion of all the pollutants below 220 degrees C with 15% of excess oxygen. In this method, handling of nano material - powder is avoided.