Surface, Acidic and Catalytic Properties of Silica-Alumina Catalysts in Jtelation to their Chemical Composition

摘要

Silica-alumina catalysts of varying chemical compositions were prepared under controlled conditions, employing the coprecipitation technique. The surface properties were determined from the adsorption of nitrogen at 77 K. The acidity was investigated by determining the adsorption of pyridine at 423 K and by following its thermal desorption up to 773 K. The conversion of 2-propanol at 523 K and the cracking of cumene at 693 K were investigated using the pulse microcatalytic technique. The surface area decreased and the mean pore volume increased with increasing alumina content. The amount of acid present and its surface density increased while the relative acid strength decreased with an increase in the alumina content. The extent of dehydration of 2-propano! increased with increasing surface acid density and proved to be insensitive to the acid strength. The cracking of cumene appears to depend on the surface area, the amount of acid present and the acid strength of the catalyst, although its dependence on these parameters is of a relative complex nature.