THE EFFECT OF GEL WATER ON CATALYTIC ACTIVITY: III. THE DECOMPOSITION OF FORMIC ACID OVER ALUMINA

Abstract

The effect of gel water content on the catalytic activity of alumina in the decomposition of formic acid at 215 and 250 °C. has been investigated. The previous observations on the dehydration of ethyl alcohol to ether and ethylene are paralleled by the results with formic acid. There are two peaks in the curves showing the relation between activity and gel water content. The ratio CO/CO2 changes with gel water content, i.e., the course of the reaction can be altered by surface modification of the catalyst. The gel showing maximum catalytic activity exhibits greatest sorption. The temperature of activation of a hydrous oxide is not as accurate a measure of the catalytic power as the gel water content. X-ray studies of the catalysts show a threefold change in the structure in the 36 to 0% range of water content, but the fibril structure of the gel of maximum activity (5.3% water) is the same as that for minimum activity. An explanation is suggested.