Physicochemical and catalytic properties of silica-alumina catalysts in the reaction of acrolein condensation with ammonia

The influences of the preparation method, composition, and treatment temperature (700-1250 degrees C) of silica-alumina samples on their phase composition and surface area, as well as on the acidic and catalytic properties in the reaction of acrolein condensation with ammonia, are studied. The phase composition of the samples is shown to represent a mixture of silicon and aluminum oxides of a certain modification, which is determined by the calcination temperature, and amorphous silica-alumina. The extent of ordering of the latter increases with increasing pretreatment temperature. The concentration of Bronsted and Lewis acid sites (BAS and LAS) per 1 m(2) tends to increase with diminishing silicon dioxide content in the samples. The acid-strength distribution for LAS is governed by the composition, preparation method, and calcination temperature. The activity and selectivity of the catalysts depend on the concentration of surface OH groups, the concentration of LAS, and, to a lesser extent, on the concentration of BAS. The selectivity to the main reaction product, beta-picoline, increases with decreasing concentration of strong LAS (vCO = 2230 cm(-1)).