Effects of Pt precursors on hydrodechlorination of carbon tetrachloride over Pt/Al2O3

Abstract

Hydrodechlorination of carbon tetrachloride (CCl4) has been studied over 1% Pt/Al2O3 prepared from various Pt precursors. The Pt/Al2O3 catalyst prepared from Pt(II) precursors showed stable, high conversion of CCl4 above 99% and selectivity of CHCl3 above 78% at the reaction temperature of 393 K, H-2/CCl4 mole ratio of 9 and weight hourly space velocity of 9000 liters/kg/h. Relative to fresh catalyst, amounts of carbon and chlorine increased in catalysts which had been used for the reaction and, in particular, when the catalysts showed deactivation. Used catalyst showed a decrease in the amount of H-2 chemisorption and the decrease was greater for catalysts prepared from Pt(IV) precursors than those from Pt(II) precursors. The catalyst prepared by Pt(NH3)(2)(NO2)(2) indicated a retarded coke formation compared to that from H2PtCl6. From temperature-programmed reduction, temperature-programmed oxidation, and X-ray absorption fine structure measurements, it was concluded that the difference between the catalysts prepared from Pt(II) and Pt(IV) precursors was due to the different oxidation states of Pt. (C) 1997 Academic Press.