Hydrocarbon oxidation and three-way catalytic activity on a single step directly coated cordierite monolith: high catalytic activity of Ce_0.98Pd_0.02O_2-δ

Abstract

Catalytic activity of cordierite honeycomb by a completely new coating method for the oxidation of major hydrocarbons in exhaust gas is reported here. The new coating process consists of (a) dipping and growing γ-Al₂O₃ on cordierite by combustion of monolith dipped in the aqueous solution of Al(NO₃)₃ and oxalyldihydrazide (ODH) (or glycine) at 600 °C and active catalyst phase Ce_0.98Pd_0.02O_2-δ on γ-Al₂O₃-coated cordierite again by combustion of monolith dipped in the aqueous solution of ceric ammonium nitrate, ODH and 1.2 × 10^-3 M PdCl₂ solution at 500 °C. Weight of active catalyst can be varied from 0.02 wt% 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. 'HC' oxidation over the monolith catalyst is carried out with a mixture having the composition, 470 ppm of both propene and propane and 870 ppm of both ethylene and acetylene with the varying amount of O₂. Three-way catalytic test is done by putting hydrocarbon mixture along with CO (10 000 ppm), NO (2000 ppm) and O₂ (15 000 ppm). Below 350 °C full conversion is achieved. In this method, handling of nano-material powder is avoided.