Carbon molecular sieves as catalysts and catalyst supports

Article abstract of DOI:10.1021/ja00005a029

Ultrahigh surface area (>2500 m²/g) carbon molecular sieves (CMS's) are shown to be very effective catalysts and catalyst supports for the oxidative dehydrogenation and dehydration of a variety of substrates. Studies of methanol, ethanol, 1- and 2-propanol, and propanal provide mechanistic insight concerning the reactivity of these materials. The activities are superior to many inorganic oxide based systems. As catalysts, CMS systems are shown to have the ability to function via hydride or hydrogen atom abstraction mechanisms, depending on the nature of the substrate. As catalyst supports, a synergism is demonstrated between the CMS support and metal dopants, which enables the system to have greater activity than that of either of the constituents alone. The highly reactive surface, the ability to disperse and stabilize metal clusters, and the extraordinary adsorption capabilities of the CMS materials are the key contributors to their high activity. One of the catalysts studied (a 15% MoO₃/CMS system) has pronounced activity toward methanol oxidation: 70% of the substrate is converted to methyl formate in a single pass with over 95% selectivity. A further significant finding involves the metal-catalyzed conversion of the carbonaceous support itself to small molecular weight products via reactions with methanol fragments. This finding has fundamental implications in heterogeneous catalyzed CO reductions and in the conversion of methanol to gasoline in zeolites.