Selective combustion of hydrogen in the presence of hydrocarbons -: 1.: Pt-based catalysts

In this communication we present experimental results showing that under certain reaction conditions the selective combustion of hydrogen in the presence of light hydrocarbons is possible over a PtSn/SiO2 catalyst. This reaction is of importance in the development of new dehydrogenation technology based on partial combustion of hydrogen to generate heat in situ to the endotbermic dehydrogenation processes. Both Sn/SiO2 and PtSn/SiO2 seem to be able to selectively combust hydrogen in a gas mixture with propane and oxygen, whereas Pt/SiPO2 alone is less selective. If propene is added to the gas mixture, Sn/SiO2 is no longer able to selectively combust hydrogen. PtSn/SiO2, on the other hand. can combust hydrogen with about 80% selectivity at 550 degreesC and 90% selectivity at 500 degreesC as long as the oxygen flow is less than half the amount of hydrogen (stoichiometry to water formation). As soon as the oxygen flow exceeds half the amount of hydrogen, the selectivity to COx increases at the expense of water. The results show that surface reactions are involved. (C) 2003 Elsevier B.V. All rights reserved.