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

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 gamma-Al2O3, TiO2, CeO2 and MgO were synthesized by a sol-gel method followed by wet impregnation of Pt and characterized by different physicochemical techniques. The conversion of DCM was higher than 90% at 500 degrees C over impregnated and non-impregnated Al2O3, TiO2 and CeO2, even at high GHSV. CO, CH3CI and CH2O were the major byproducts observed and their amounts decreased after Pt impregnation. The CH3CI formation was higher when Lewis acid sites were present while the existence of Bronsted sites promoted the CH2O formation. The complete conversion of DCM was achieved at around 450 degrees C over the Al2O3 and Pt/Al2O3 and at 500 degrees C for Pt/TiO2. These two catalysts exhibited the highest total acidities among the materials tested. The activity of Pt/Al2O3 remained the same also after 55 h of testing, however, increase in Pt particle size and decrease in acidity were observed. Pt/CeO2 while being less active showed smallest amount of byproduct 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. (C) 2016 Elsevier B.V. All rights reserved.