Contribution of mass spectrometry to the determination of basic sites in solid catalysts

Abstract

Abstract This paper reports a new thermal programmed desorption–mass spectrometry (TPD‐MS) method for determining the number and relative strength distribution of basic sites in solid catalysts using CO 2 as titrant. The overall desorbed CO 2 area is proportional to the total basicity, while the number of peaks and their maximum temperature ( T max ) are related to the particular type of basic site and its strength. The activation energy for CO 2 desorption from various basic sites in each catalyst was calculated via TPD‐MS experiments conducted at a variable heating rate for each catalyst, using the Kissinger equation. Diffuse reflectance infrared analysis of the bands at 2000–1000 cm −1 for CO 2 adsorbed on various catalysts allows one to elucidate the nature of the chemical species involved, which depends on the particular type of site. The total basicity results obtained are compared with those provided by an existing spectrophotometric method using benzoic acid (p K a =4.19) as titrant.