Methanol decomposition to synthesis gas at low temperature over palladium supported on ceria-zirconia solid solutions

The CexZr1-xO2 solid solution was used as a support of a palladium catalyst for methanol decomposition to synthesis gas at low temperature. All Pd-con taining catalysts tested in this study showed high selectivity to synthesis gas lover 96%). The Pd supported on the composite oxide with a Ce/Zr molar ratio of 4/1 exhibited the highest activity. Pd/Ce0.8Zr0.2O7 (17 wt.%) (co p) (prepared by coprecipitation method) showed a conversion of 51.2% for th e methanol decomposition at 473 K, which was higher than those over 17 wt.% Pd/CeO2 (cop) (40.7%) and 17 wt.% Pd/ZrO2 (cop) (24.3%) at 473 K, The 17 w t,% Pd/Ce0.8Zr0.2O2 (cop) catalyst showed a higher BET surface area and sma ller Pd particles than those of 17 wt,% Pd/CeO2 (cop), Moreover, a more act ive Pdsigma+ state could be maintained by Zr4+ ion modification due to prom otion of the oxygen mobility and enhancement of the reductibility and incre ase in the acid sites of the CeO2 support. The 17 wt.% Pd/Ce0.8Zr0.2O2 (cop ) catalyst showed a much higher conversion (51.2%) than that over 17 wt.% P d/Ce0.8Zr0.2O2 limp) (prepared tay impregnation method) (17.2%) at 473 K. T his is due to the 17 wt.% Pd/Ce0.8Zr0.2O2 (cop) possessing many small Pd pa rticles. The 17 wt.% Pd/Ce0.8Zr0.2O2 (cop) catalyst showed an initial conve rsion of 51.2% at 473 K but the conversion decreased to 43.1% after 24 h on stream. This deactivation was attributed to carbonaceous deposit on the ca talyst surface. The amounts of coke on the 17 wt.% Pd/Ce0.8Zr0.2O2 (cop) ca talyst were 0.9 wt.% after 24 h on stream at 473 K and 2.1 wt,% after 1 h o n stream at 523 K. (C) 2001 Elsevier Science B,V. All rights reserved.