Study of reaction intermediates of methanol decomposition and catalytic partial oxidation on Pt/Al2O3

Methanol is considered a promising liquid fuel for hydrogen fuel cell systems. Catalytic partial oxidation (CPO) of methanol offers the potential of producing hydrogen for these systems, and is capable of high hydrogen production rates with no heat addition. However, the mechanism of methanol CPO is not completely understood due to its complexity. In this work, methanol CPO on Pt/Al2O3 catalysts was studied using in situ diffuse reflectance infrared Fourier transform spectroscopy (DRIFTS) and mass spectrometry. Methanol adsorption experiments were conducted on different catalyst states. Methoxy species, CH3OS, were formed during dissociative adsorption of methanol. As temperature was increased, formate adspecies, likely formed by reaction of methoxy species with surface hydroxyls, were increasingly formed. Ignition of CPO was also studied, and it was found to occur at room temperature on both reduced and oxidized powder catalysts. Formate disappeared during this process, while CO species and Co-2 were detected in the products. CPO was studied at different temperatures from 723 K to 973 K, and for methanol to oxygen mole ratios from 2 to 4. It was found that CO2 productivity increased at lower temperatures and H-2 and CO had a higher selectivity at higher temperatures. Fuel lean conditions favored H-2 and HCOOH production. CO2 increased when O-2 concentration increased in the reaction mixture. These results suggest that formate was one of the important intermediates in the methanol partial oxidation reaction pathway. Indirect formate decomposition is dominant for CO2 production in the reactions at higher temperatures. (C) 2008 Elsevier B.V. All rights reserved.