Removal of oxygen from (bio-)methane via catalytic oxidation of CH4 - Reaction kinetics for very low O2:CH4 ratios

For evaluation of design specifications for catalytic oxygen removal units, examinations on reaction kinetics of catalytic oxidation of methane at very low O2:CH4 ratios have been performed in the temperature range between 200 < T < 350 °C and pressures below 10 bar, applying a commercial noble metal (Pt) Al2O3-based catalyst. On the basis of the experimental results, a mass based rate equation is proposed, taking into account the influence of both, reactants and products of the reaction on the conversion rate of oxygen. This equation is valid for oxygen inlet pressures of as low as 1 mbar and has further been tested in a balance of methane of up to pCH4 = 10 bar (abs.). For comparison of conversion rates of oxygen with various other reductives, such as ethane, propane and butane, equivalent experiments were performed and kinetic parameters of corresponding power law approaches are given. Finally, the catalytic activity of further noble metals and some transition metal catalysts was tested and compared to the platinum reference catalyst.