Influence of the products of the partial oxidation of methane (POM) on the catalytic performances of Rh/Ti-modified support catalysts

The influence of the addition of 1, 2 or 5 vol.% of CO, H2 or CO2 to the feed during the partial oxidation of methane (POM) was studied over Rh/Ti-modified support catalysts (Rh/Ti–SiO2, Rh/Ti–Al2O3 and Rh/Ti–MgO). The changes observed in the conversion and syngas selectivity in the presence of gaseous co-feeds are due to changes in the kinetics of POM and may be mainly explained by modifications in the oxidation state of rhodium during the reaction. A higher reduction of Rh is observed when 5% of H2 or CO is co-fed while Rh is maintained in a higher oxidation state in the presence of CO2 co-feed. Reversibility tests show that the modifications induced by the gaseous promoters in the catalytic performances are reversible. Such changes can alter not only the kinetics of POM but also the kinetics of the other reactions involved (dry reforming and the reverse water-gas shift) during POM reaction. Results have implications in the expression of the reaction kinetics to be used in the modelling of POM reaction mechanism.

Figure optionsDownload high-quality image (158 K)Download as PowerPoint slideResearch highlights▶ Co-feeding of H2, CO or CO2 (reaction products) affects catalytic performances. ▶ The observed results are not explained by thermodynamics but by kinetic changes. ▶ The modifications on catalytic performances induced by gas co-feeds are reversible. ▶ An optimal oxidation state of Rh could explain the high selectivity of syngas. ▶ H2/CO ratio can be modulated by adding proper amounts of co-feeds during POM.