Effect of organosulphur, organonitrogen and organooxygen compounds on the hydrodechlorination of tetrachloroethylene over Pd/Al2O3

The performance of a 0.5 wt.% Pd on alumina catalyst used for the hydrodechlorination of tetrachloroethylene, in presence of model organosulphur (thiophene and butanethiol) organonitrogen (quinoline and n-butylamine) and organooxygen (tetrahydrofurane, isobutanol) compounds, was studied in this work. Experiments were carried out in a continuous fixed bed reactor (space time of 1.8 min g/mmol of TTCE) at a pressure of 0.5 MPa and a temperature range of 200–300 °C. Concentrations of heteroatomic molecules in the range 0.5–5% were used in this study.Organosulphur compounds produce strong inhibition on the TTCE hydrodechlorination, decreasing the conversion and increasing the selectivity for partially dechlorinated compounds (trichloroethylene). However, this effect is shown to be highly reversible, the catalyst almost recovering its initial activity when the sulphur source is removed from the feed. Organonitrogen compounds cause a fast and fatal deactivation of the catalysts, being this effect completely irreversible. Different regeneration procedures were tested, being the treatment with hydrogen at 400 °C the only way to partially recover catalytic activity. Finally, organooxygen compounds hardly affect catalyst performance.