Characteristics of the Pd-only three-way catalysts prepared by sol-gel method

Pd-only three-way catalysts prepared by the sol-gel method were investigate d by the three-way catalytic performance test with a simulated exhaust gas in a continuous U-tube quartz reactor at a gas hourly space velocity of 72 000 h(-1). The catalysts were characterized with XRD, XPS, BET surface area and pore volume. The activity and thermal stability of the Pd-Al2O3 cataly st prepared at pH 10 were superior to those at pH 4 during hydrolysis and c ondensation, which could be explained by the anchoring effect. Zr and V wer e found to be good promoters for the enhancement of the thermal stability a nd SO2\ resistance, respectively. Optimally formulated catalyst, Pd(1)-V(2) -Zr(10)-Al2O3, was thermally stable up to 900 degrees C and showed a much m ore improved low-temperature activity and excellent SO2 resistance. (C) 199 9 Elsevier Science B.V. All rights reserved.