Infrared spectroscopy to study the mechanism of catalytic reaction on molecular scale from diffusion to limiting stage kinetics

Reported here are results recently obtained at the Institute of Catalysis w ith the IRS of adsorbed molecules used to study the mechanisms of catalytic reactions occurring on the surface of heterogeneous catalysts. It has been found that the structure and strength of OH groups complexes with diffusin g molecules (M) are the key factors determining the rate of molecules trans fer inside the zeolite crystals. Stoichiometry 2M:1OH appears to provide a higher diffusion rate. Original procedures allowing the identification of s urface species nature were designed. One of these procedures is based on a quantitative measurement and dosing at a joint adsorption of reagents and p robe molecules. Using a joint adsorption of CO and tert-butyl chloride on f luorinated alumina, we have proved that tert-butyl chloride forms complexes with the Lewis sites through the chlorine atoms. The alternating adsorptio n of aromatic molecules and ammonia proved the aromatic molecule protonatio n on V2O5/Al2O3 catalyst. A lot of examples of IR mechanistic studies of ca talytic reaction on surface are presented. There are butyl alcohol dehydrat ion, methane partial oxidation, n-butyl amine deamination, NOx selective re duction. (C) 2000 Elsevier Science B.V. All rights reserved.