Hydrodechlorination of CCl4 over Pt/gamma-Al2O3 prepared from different pt precursors

Abstract

The platinum particle size on gamma-Al2O3 prepared from different platinum precursors such as Pt(NH3)(2)(NO2)(2), H2PtCl6, and K2PtCl6, and its effect on hydrodechlorination (HDC) of CCl4 With the variation of calcination temperatures was investigated. It concomitantly affects the products distribution and catalytic stability in HDC of CCl4. To verify the effects of platinum particle size with different platinum precursors on the product distribution, the catalysts have been characterized by HRTEM and CO chemisorption, FF-IR, and TP methods (TPR, TPD and TPSR). The catalysts with small platinum particles, which possess low coordination number and electron-deficient character, favor the complete dechlorination of CCl4 and produce CH4 more selectively. It could be due to the strong adsorption strength of CCl4 or the decreased activation energy of surface intermediates on small platinum particles. FF-IR studies reveal that the maximum peak position of linear-bonded CO shifted to the higher frequency with the increase of platinum particle size in all catalysts prepared from three different platinum precursors. While the selectivity to CH4 increased with the decrease in the platinum particle size, the total amount of carbonaceous species on the platinum particles was enhanced. The larger the platinum particle, the higher the selectivity to CHCl3 was obtained in all tested catalysts under the non-deactivating condition. (c) 2007 Elsevier B.V. All rights reserved