Novel methanol steam reforming activity and selectivity of pure In2O3

Abstract

Pure In 2 O 3 thin film and In 2 O 3 powder catalysts were found to be structurally stable and highly active and CO 2 -selective in methanol steam reforming between 450 and 673 K. No catalytic activity in both routes of the water–gas shift reaction as tested in the same temperature region where the catalysts exhibit high reforming activity and selectivity, could be observed. Electron-microscopy suitable In 2 O 3 thin films prepared by thermal deposition of In 2 O 3 powder in 10 −2 Pa O 2 at 600 K and, for comparison, a commercial polycrystalline In 2 O 3 powder catalyst were tested in methanol steam reforming and in both routes of the water–gas shift reaction as a function of reaction temperature. The effect of oxidative (1 bar O 2 , 373–673 K, 1 h) and reductive (1 bar H 2 , 373–673 K, 1 h) catalyst pre-treatments was assessed. The resulting structural and morphological changes occurring during catalyst activation and catalytic reaction were monitored by (high-resolution) transmission electron microscopy, scanning electron microscopy and surface area measurements by N 2 adsorption according to BET. Both the In 2 O 3 thin film and the powder sample were observed to be structurally stable under typical catalyst pre-treatments in oxygen and hydrogen at temperatures T ≤ 673 K and T < 673 K, respectively, as well as under typical methanol steam reforming conditions at temperatures T ≤ 680 K. No pronounced catalyst sintering was observed below 673 K. Both In 2 O 3 samples were found to be highly active and selective toward CO 2 in methanol steam reforming over a broad temperature range (450 < T < 673 K). Selectivities of >95% toward CO 2 were usually observed, with at maximum 5% or less CO formed. No dependence of selectivity on either reaction temperature or oxidative/reductive pre-treatment was observed. No catalytic activity in both routes of the water–gas shift reaction as tested in the same temperature region where the catalysts exhibit high reforming activity and selectivity, could be observed. Therefore In 2 O 3 based catalysts offer a broad range of temperature not influenced by unwanted CO formation via the inverse water–gas shift process.