Catalytic combustion of methane in non-permselective membrane reactors with separate reactant feeds

Catalytic combustion of methane over Pd and Pt/SiO2/alpha-Al2O3 membranes was studied in the temperature range 300-650degreesC. Fuel and oxygen were fed at opposite membrane sides. In order to improve reactor controllability the alpha-Al2O3 membranes were impregnated with SiO2 sol resulting to smaller pore size. Methane conversions up to 100% for the palladium membrane and up to 42% for the platinum membrane were achieved. The results indicated a transition from kinetic to mass transfer control within the temperature range investigated. This was accompanied by reduction of methane slip from tube to shell side with increasing temperature. CO and H-2 were detected in the product gases of the palladium membrane. Their concentration could be reduced by applying a trans-membrane pressure difference. Low concentrations of CO were observed for the Pt/SiO2/alpha-Al2O3 membrane, while no CO or H-2 were detected for a Pd/alpha-Al2O3 membrane operating in dead-end configuration. (C) 2003 Elsevier B.V. All rights reserved