DETECTION OF ACIDITY ON SILICA-ALUMINA CATALYSTS BY INFRARED SPECTROSCOPY-PYRIDINE CHEMISORPTION - RELATIONSHIPS BETWEEN CATALYST ACIDITY AND ACTIVITY

The Brönsted acidity and catalytic activity of two series of silica-alumina catalysts have been measured. The Brönsted acidity was measured by means of the infrared spectrum of chemisorbed pyridine. Brönsted acid sites can be detected in silica-alumina containing 0.25% alumina. For a constant degree of cross-linking, the Brönsted acidity is proportional to the alumina content of the silica-alumina. For two series of silica-alumina catalysts, containing up to 14% alumina, there is a linear relationship between the Brönsted acidity and the catalytic activity for o-xylene isomerization. It is possible for catalysts to possess carbonium ion type activity while exhibiting no Brönsted acidity detectable by infrared spectroscopy. © 1969.