Division of Chemistry and Chemical Engineering
California Institute of Technology, Pasadena, CA 91125 USA

Abstract.   Current technologies for conversion of natural gas and petroleum to oxygenates and olefins, while well established, are energy intensive and polluting.  New catalytic processes that are more efficient and “greener” are required to reduce CO₂ emissions and to more effectively utilize our fossil fuel reserves.  A particularly attractive potential approach is direct, selective partial oxidation.  Unfortunately, selectivity for partial oxidation of alkanes with most oxidants, including O₂, is complicated by the increasing reactivity of its oxidation products, such that the yield of the desired product is severely limited.  Organometallic reagents offer potentially more attractive selectivity: e.g. the "Shilov System", stoichiometric oxidation of alkanes to alcohols by aqueous Pt^IV, exhibits unusual selectivity and better compatibility with strong oxidants and protic reagents.  Using a variety of kinetics, isotopic labeling and stereochemical studies, we have examined the mechanisms of the second and third steps of the Shilov cycle, as well as the first step using better behaved model systems.  An alternate approach would involve conversion of light alkanes via steam reforming to syngas, a mixture of carbon monoxide and dihydrogen, then subsequent conversion of syngas to chemicals and liquid fuels.  Although this route suffers from the endothermicity of the steam reforming step, it offers the advantage of being more general, because coal and biomass may also be steam reformed to syngas.  Heterogeneous Fischer-Tropsch synthesis of hydrocarbons and oxygenates is well established, but selectivity is poor and subsequent upgrading to useful products is required.  Recent progress has been made aimed at developing a homogeneous, more selective catalyst system for converting syngas to C_n>1 products by an approach involving two metals: one to coordinate carbon monoxide and to promote C-C bond formation, another to activate H₂ and deliver it to CO and its partially reduced fragments.

Hosted by Graduate Students

Thursday, April 14, 2011

Meet the Speaker at 1:30pm in Room, 328 Havemeyer
Tea & cookies at 4:00pm in Room, 328 Havemeyer
Seminar at 4:30 in Room 209 Havemeyer