Pd and Pd-Pt catalysts supported on SnO2 and γ-Al2O3: Kinetic studies of wet lean methane combustion

Abstract

Kinetic investigation of methane combustion on hydrothermally aged SnO2 and Al2O3 supported 1 wt% Pd and 1 wt% Pd-Pt(1:1) catalysts is reported in the presence of 5 and 10 vol% H2O. First-order to CH4, activation energy of 143 kJ/mol and −1 order to H2O were observed for Pd/Al2O3. Both Pd-Pt catalysts demonstrated −1 order to water and activation energies of 128 kJ/mol, proposing the choice of support is inconsequential with Pt addition from the viewpoint of the activation energy. Pd/SnO2 illustrated −0.2 order to H2O. A rate law was suggested with two active sites, one affected by H2O with −1 order and activation energy of 140 kJ/mol, and the other unaffected by water with activation energy of 88 kJ/mol. Turnover frequencies at wet conditions at 425 degC were found in the order of Pd/Al2O3(“x”) < Pd/SnO2(24x) < Pd-Pt/ Al2O3(102x) < Pd-Pt/SnO2(275x). The Pd-Pt/SnO2 catalyst also demonstrated the least deactivation during hydrothermal ageing.