AN FTIR AND STATIC SIMS STUDY OF THE ADSORPTION OF PROPYLENE ON CU-ZSM-5 CATALYSTS

Diffuse reflectance infrared spectroscopy and static secondary ion mas s spectrometry (SIMS) were employed to study the surface species forme d during the adsorption and reaction of propylene on a copper-exchange d ZSM-5 catalyst. Propylene showed characteristics of chemisorption on Cu-ZSM-5 at room temperature and total decomposition to CO, CO2 and C H4 at 350 degrees C. The ir bands of =C-H stretching at 3101 cm(-1), = C-C stretching at 916 cm(-1) and C=CH2 twisting at 575 cm(-1) for prop ylene disappeared upon adsorption, indicating the breaking of the C=C double bond, while the decrease in the signal intensity of zeolite iso lated and vicinal SiOH groups at 3700 and 3592 cm(-1) implied that the adsorbed di-sigma species was bound to zeolite SiO-. Static SIMS show ed two distinguished peaks at 73 and 147 amu, which were assigned to t he adsorbed species H2OSi2(C3H5O2) due to the interaction of propylene with ZSM-5 and Cu-ZSM-5. The adsorption and reaction of propylene wer e enhanced by the presence of Cu+ in ZSM-5. The mechanism for these pr ocesses was discussed.