IR spectroscopy of hydrotreating catalysts

Abstract

A correlation between IR spectra and catalyst activity has been investigated via in situ diffuse reflectance IR spectroscopy of probe molecules, adsorbed onto hydrotreating catalysts. This technique allows very high quality spectra to be obtained with minimal sample preparation. The use of an in situ cell has allowed the detection of CO physisorbed on Al³⁺ and weakly chemisorbed on reduced Co and Mo sites. Chemisorbed NO was shown to be desorbed readily in a vacuum; this occurs to a greater extent from the Co sites than the Mo sites. A comparison of the measured catalyst performance with the ratio of the Co to Mo nitrosyl bands suggests that the method is not sufficiently sensitive to distinguish between the small differences in activity that are commercially important.