Catalytic conversion of isopropyl alcohol on the heteropolic acid – titanium oxide system

Abstract

A complex of modern physicochemical methods (X-ray phase analysis, low-temperature adsorption of nitrogen, scanning electron microscopy, element analysis) was used to study the phase and texture properties of the phosphomolybdenum heteropoly acid–titanium oxide catalytic system. It was found that the optimal content of phosphomolybdenum heteropoly acid, which leads to an increase in the catalytic activity of titanium dioxide, is 7% wt.: the diisopropyl ether yield is higher, it reaches maximum values in a shorter period of time, and the samples are characterized by greater stability. It is shown that the textural characteristics of the specific surface area and dispersion are not the key factors responsible for the catalytic activity. It has been suggested that the activity of phosphomolybdenum heteropoly acid-containing samples is associated with the emergence of a new type of active centers that exhibit increased electron-donor properties (terminal oxygen atoms of the outer fragments of octahedra М = О heteropolyacids). A drop in the catalytic activity of samples with a phosphomolybdenum heteropoly acid content of more than 7 % wt. associated with the formation of surface metaphosphoric acid and entails a decrease in active centers.