INTERACTION AND CATALYTIC DECOMPOSITION OF 1,1,1-TRICHLOROETHANE ON HIGH SURFACE-AREA ALUMINA - AN INFRARED SPECTROSCOPIC STUDY

Transmission infrared spectroscopy has been used to study the catalytic decomposition of 1,1,1-trichloroethane, CH3CCl3, on high surface area alumina, Al2O3, in the temperature range 300-600 K. At 300 K CH3CCl3 is reversibly adsorbed on the isolated surface hydroxyl groups of Al2O3 via hydrogen bonding. At T greater-than-or-equal-to 400 K an alpha,beta-HCl elimination occurs, forming CH2 = CCl2(g). A small amount of surface carboxylate was also formed by means of a minor reaction pathway. It was found that Lewis acid (Al3+) surface sites were involved in causing the primary reaction. This was shown by the observation that irreversible adsorption of pyridine on the Al3+ sites efficiently quenched the surface reaction. Conversely, surface Al-OH groups are not involved in the CH3CCl3 decomposition.