Catalytic Hydrodechlorination of Tetrachloroethylene over Pd/TiO2 Minimonoliths

The gas phase catalytic hydrodechlorination (CHD) of tetrachloroethylene (TTCE) over 0.8% Pd/TiO2 (Hombikat uv-100) washcoated cordierite minimonoliths has been Studied in the temperature range 120-180 degrees C. Experiments were carried Out operating Under differential regimes at a gas hourly space velocity (GHSV) of 0.45 (g min)/mL and using different concentrations of TTCE (300-1000 ppmv), hydrogen (0-10000 ppmv), ethane (0-850 ppmv), and hydrogen chloride (0-550 ppmv), The turnover frequency, specific rate constant, reaction order, and activation energy were determined. The pseudo-first-order Langmuir-Hinshelwood models adequately represent experimental results. The best adjustment corresponds to models featuring TTCE adsorption (associative or dissociative) as the limiting step. The CHD reaction is favored as TTCE and hydrogen concentrations are increased, while HCl negatively affects kinetic parameters. In order to study the causes of deactivation, fresh and used catalyst samples were characterized by nitrogen adsorption (BET), H-2 chemisorption, thermogravimetric analysis (TGA), Fourier transform infrared (FTIR), and temperature-programmed oxidation Coupled to mass spectrometry. Characterization results indicate that carbonaceous deposits were insignificant Under reaction conditions, while the presence of HCl was the main cause of catalyst deactivation,