Evaluation of the selectivity for methanol decomposition over anodized aluminum plate catalyst coated with silica

A plate type methanol decomposition catalyst which has higher heat conductivity was prepared based on anodic oxidation of aluminum. In order to reduce the formation of dimethyl ether as a by-product at the acid site of alumina, silica was coated on the anodized alumina plate. By the measurement of ammonia TPD, it was found that the acidity of the silica coated catalyst was lower than that of the plate without coating. As for the silica coated plate, the profile of methanol TPD also showed that the formation of dimethyl ether was smaller and peak temperature was higher, although those without silica coating indicated a large amount of dimethyl ether formation. After Pd was loaded on the plate, the catalytic activity of methanol decomposition to hydrogen and carbon monoxide and the formation of dimethyl ether as a by-product were evaluated at 200 and 250 degreesC by a continuous fixed bed reactor. The content and dispersion of Pd of silica coated catalysts were smaller than that of the hydrated catalyst without silica coating and the formation rate of carbon monoxide was increased with increasing metal surface area of Pd. The formation rate of dimethyl ether over the silica coated catalyst was approximately 1/20 of that of the catalyst without silica coating and it was independent of silica contents.