Hydrodechlorination of carbon tetrachloride over PtNaX zeolite: Deactivation studies

Platinum-containing NaX zeolite showed high activity and high methane selectivity in the hydrodechlorination of carbon tetrachloride. The catalyst showed fast deactivation. To identify the possible causes of deactivation, the fresh and used catalysts were studied by thermogravimetric analysis, X-ray diffraction, thermoprogrammed oxidation, infrared spectroscopy and diffuse reflectance spectroscopy. The results indicate that the deactivation is probably caused by the attack of the HCl produced during the reaction to the zeolite structure forming an amorphous aluminosilicate. The HCl adsorption can also be pointed as a cause for deactivation. It is worthy to mention that no coke formation (oligomers) was observed, which is not consistent to some other observations made for other platinum-containing catalysts.