Reaction Performance of Cracking of Methanol over Supported Platinum Catalysts

Abstract

To establish a catalytic process for the cracking of methanol (CH₃OH=CO+2H₂), various supported platinum (such as rhodium, palladium, ruthenium) catalysts (supports : Al₂O₃ (γ, α), CaO, CeO₂, Cr₂O₃, La₂O₃, MgO, Nb₂O₅, SiO₂, TiO₂ (anatase), Y₂O₃, ZnO, ZrO₂) were prepared and the relationship between the reaction conditions and the catalytic activity-selectivity was investigated, together with the measurement of surface acidity by the temperature-programmed desorption method.
The experiments were carried out using a fixed-bed flow reactor under atmospheric pressure, mainly at 300°C and 350°C. The inlet gas was mainly 10% CH₃OH-N₂, the total flow rate was 250 cm³ N · min^-1 per ml of each catalyst with an average diameter of 1.0 mm, and the residence time was 0.24 s.
The main results obtained were as follows. (1) Activity and selectivity were widely different according to kind of support, and CH₃OCH₃, CH₄, CO₂, H₂O were more or less formed as by-products, in amounts that were larger at the acidic supports. (2) As side reactions, 2CH₃ OH=CH₃OCH₃ +H₂O, CH₃OCH₃ = CH₄ + CO + H₂, CO+ 3H₂= CH₄+ H₂O and CO+H₂O=CO₂+H₂ were considered. (3) Pt/MgO was the most suitable catalyst, giving good activity and selectivity to CO and H₂ among the catalysts used in this study.