Effect of TiO[sub.2] on Pd/La[sub.2]O[sub.3]-CeO[sub.2]-Al[sub.2]O[sub.3] Systems during Catalytic Oxidation of Methane in the Presence of H[sub.2]O and SO[sub.2]

New results on the effect of TiO[sub.2] on Pd/La[sub.2]O[sub.3]-CeO[sub.2]-Al[sub.2]O[sub.3] systems for catalytic oxidation of methane in the presence of H[sub.2]O and SO[sub.2] have been received. Low-temperature N[sub.2]-adsorption, XRD, SEM, HRTEM, XPS, EPR and FTIR techniques were used to characterize the catalyst. The presence of Ce[sup.3+] 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[sub.2] from anatase to larger particles of rutile; and (iii)—the increase in PdO/Pd—ratio above its optimum. The modification by Ti of the La[sub.2]O[sub.3]-CeO[sub.2]-Al[sub.2]O[sub.3] system leads to higher resistance towards the presence of SO[sub.2] 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/La[sub.2]O[sub.3]-CeO[sub.2]-TiO[sub.2]-Al[sub.2]O[sub.3] catalyst follows the Mars–van Krevelen mechanism. For evaluation of the possible practical application of the obtained material, a sample of Pd/La[sub.2]O[sub.3]-CeO[sub.2]-TiO[sub.2]-Al[sub.2]O[sub.3], supported on rolled aluminum-containing stainless steel (Aluchrom VDM[sup.®]), was prepared and tested. Methane oxidation in an industrial-scale monolithic reactor was simulated using a two-dimensional heterogeneous reactor model.