IN-SITU ESR STUDY OF RHHZSM-5 INTERACTION WITH DIFFERENT COMPOUNDS

Interaction between isolated Rh2+-sites stabilized by the H-ZSM-5 matr ix and inorganic and organic molecules (NO, NO2, CO, propene, H-2, CCl 4, benzene, chlorbenzene) was studied by ESR at 120-573 K. In situ ESR monitoring of isolated paramagnetic Rh-species in a flow of gas mixtu res permits the elucidation of the state of the active sites in suppor ted Rh-catalysts under more realistic, i.e. closer to the working stat e, conditions. For instance, strong adsorptive coupling of the Rh ESR- active centers is noted with NO. Weak interaction with physically adso rbed tetrachloromethane can also be observed by ESR. Some preliminary results of methane oxidation catalysis are presented for starting RhZS M-5 and for the sample treated with a phosphite complex. (C) 1998 Else vier Science B.V.