Effect of TiO on Pd/LaO-CeO-AlO Systems during Catalytic Oxidation of Methane in the Presence of HO and SO.

New results on the effect of TiO on Pd/LaO-CeO-AlO systems for catalytic oxidation of methane in the presence of HO and SO have been received. Low-temperature N-adsorption, XRD, SEM, HRTEM, XPS, EPR and FTIR techniques were used to characterize the catalyst. The presence of Ce on the catalytic surface and in the volume near the lantana was revealed by EPR and XPS. After aging, the following changes are observed: (i) agglomeration of the Pd-clusters (from 8 nm to 12 nm); (ii) transformation of part of the TiO from anatase to larger particles of rutile; and (iii)-the increase in PdO/Pd-ratio above its optimum. The modification by Ti of the LaO-CeO-AlO system leads to higher resistance towards the presence of SO most likely due to the prevailing formation of unstable surface sulfites instead of thermally stable sulfates. Based on kinetic model calculations, the reaction pathway over the Pd/LaO-CeO-TiO-AlO catalyst follows the Mars-van Krevelen mechanism. For evaluation of the possible practical application of the obtained material, a sample of Pd/LaO-CeO-TiO-AlO, supported on rolled aluminum-containing stainless steel (Aluchrom VDM), was prepared and tested. Methane oxidation in an industrial-scale monolithic reactor was simulated using a two-dimensional heterogeneous reactor model.