Comparative study on the support properties in the total oxidation of dichloromethane over Pt catalysts

Abstract The aim of this work was to study the influence of the support oxide properties on the total oxidation of dichloromethane in moist conditions. The support materials γ-Al 2 O 3 , TiO 2 , CeO 2 and MgO were synthesized by a sol-gel method followed by wet impregnation of Pt and characterized by different physico-chemical techniques. The conversion of DCM was higher than 90% at 500 °C over impregnated and non-impregnated Al 2 O 3 , TiO 2 and CeO 2 , even at high GHSV. CO, CH 3 Cl and CH 2 O were the major by-products observed and their amounts decreased after Pt impregnation. The CH 3 Cl formation was higher when Lewis acid sites were present while the existence of Bronsted sites promoted the CH 2 O formation. The complete conversion of DCM was achieved at around 450 °C over the Al 2 O 3 and Pt/Al 2 O 3 and at 500 °C for Pt/TiO 2 . These two catalysts exhibited the highest total acidities among the materials tested. The activity of Pt/Al 2 O 3 remained the same also after 55 h of testing, however, increase in Pt particle size and decrease in acidity were observed. Pt/CeO 2 while being less active showed smallest amount of by-product formation during the whole temperature range used in light-off tests. This is most probably due to its easy reduction ability. The textural parameters of the supports did not appear to be the key parameters when considering the activity and selectivity of the catalysts.