TEMPERATURE-PROGRAMMED DESORPTION STUDIES OF THE INTERACTIONS OF H2, CO, AND CO2 WITH CU/SIO2

The interactions of H2, CO, and CO2 with a Cu/SiO2 catalyst have been investigated using temperature-programmed desorption spectroscopy. The heats of adsorption of H2 and CO were obtained from analysis of the experimentally observed spectra, and the activation energy for H2 adsorption was obtained from isothermal measurements of the adsorption rate. The heat of adsorption of H2 increases from 10.1 to 13.8 kcal/mol for 0.07 ≤ θH ≤ 0.26. The activation energy for H2 adsorption is 10.5 kcal/mol. and the activation energy for H2 desorption increases from 20.6 to 24.3 kcal/mol for 0.07 ≤ θH ≤ 0.26. The heat of adsorption of CO decreases with coverage from 16.4 to 12.5 kcal/mol for 0.01 ≤ θCO ≤ 0.18. The coverage by molecularly adsorbed CO2 was below the detectable limits for adsorption temperatures above 250 K. Evidence was found, however, for a small amount of dissociatively adsorbed CO2. The present findings are in very good agreement with recent studies on Cu single-crystal surfaces. © 1993 by Academic Press, Inc.