Effects of Pt Precursors on Hydrodechlorination of Carbon Tetrachloride over Pt/Al 2 O 3

Hydrodechlorination of carbon tetrachloride (CCl 4 ) has been studied over 1% Pt/Al 2 O 3 prepared from various Pt precursors. The Pt/Al 2 O 3 catalyst prepared from Pt(II) precursors showed stable, high conversion of CCl 4 above 99% and selectivity of CHCl 3 above 78% at the reaction temperature of 393 K, H 2 /CCl 4 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(NH 3 ) 2 (NO 2 ) 2 indicated a retarded coke formation compared to that from H 2 PtCl 6. 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.