Infrared studies of the adsorption and the catalysis of hydrogen chloride on alumina and on silica

Abstract

Catalytic activity of hydrogen chloride on alumina and silica was studied by infrared technique, and it was found that chemisorption of HCl on dry alumina produced new hydrogen bonded OH groups on the surface. Most of these OH groups exchanged with butenes during the isomerization as fast as the rate proportional to the reaction rate. From these facts and the surface acidity of the HCl-treated alumina, it is concluded that the new OH groups produced by the adsorbed HCl are protonic and participate in the n-butene isomerization as Brönsted acid. On the other hand, HCl scarcely adsorbed on silica. The isomerization of n-butenes on silica did not occur in the presence of gaseous HCl, while OH groups on silica surface exchanged very rapidly with gaseous DCl.