PdO/Al2O3 in catalytic combustion of methane: stabilization and deactivation

In the recently developed catalytically assisted combustors for gas turbines using natural gas, deactivation of the palladium oxide (PdO) catalyst needs to be prevented. The effects of additives such as lanthanum and neodymium in PdO/Al2O3 on the catalytic durability at 1123 K were studied using a conventional fixed-bed flow reactor at atmospheric pressure. The surface properties of the catalysts were investigated using CO chemisorption, XRD, and TPD after CH4 adsorption. The catalyst deactivation during CH4 oxidation followed the equation (phi)=r1[1/(1+(alpha)1t)]^n1+r2[1/(1+(alpha)2t)]^n2, where r, (alpha) and n are constants, subscripts 1 and 2 are the rapid and slow deactivation species, respectively, and t is time on stream. The PdO/Al2O3 catalyst was rapidly deactivated by the transformation of PdO to metallic Pd and slowly deactivated by the particle growth of PdO. The addition of Nd2O3 and La2O3 to PdO/Al2O3 prevented the particle growth of PdO as well as the transformation of PdO to Pd up to high temperature.