Effects of Ti loading on activity and redox behavior of metals in PtCeTi/KIT-6 catalysts for CH4 and CO oxidation

Abstract

Ti-KIT-6 materials having different TiO2 loadings (5%, 10%, 30%) were synthesized, modified by Ce and Pt immobilization, characterized by N2-adsorption/desorption, XRD, SEM, EDX, TEM, XPS and TPR analysis techniques and tested in CH4 combustion and CO oxidation reactions. The mesoporous ordered structure of KIT-6 support was preserved in regard to surface area and pore volume. The average pore size was decreasing due to the effect of titania loading and other metals immobilization. The effects of TiO2 content and immobilization of CeO2 on Pt were studied in view of the catalytic properties. XPS showed the increase in electron density on Pt owing to contribution of TiO2, but on the other hand it was decreasing as result of CeO2 effect. The metal–support interaction, under conditions of varying TiO2–CeO2 mixed oxide composition, as evidenced by XRD and TPR, was correlated with the catalytic results. The highest conversion degree of CH4 was observed with the PtTi-KIT-6 samples within the temperature range 250–400°C and the highest activity was displayed by the PT5K6 sample in both reactions. The slight decrease in activity was observed at the highest Pt0 concentration on samples with 30%TiO2. This can be due to highest dispersion degree of Pt metal and lower surface area of the catalyst. All the samples with supported titania and ceria were active in CH4 and CO oxidation reactions and the selectivity to CO2 varied with temperature.