Selective oxidation of methanol and ethanol on supported ruthenium oxide clusters at low temperatures

Journal Article · Thu Mar 04 00:00:00 EST 2004 · Journal of Physical Chemistry B

OSTI ID:837401

Liu, Haichao; Iglesia, Enrique

RuO2 domains supported on SnO2, ZrO2, TiO2, Al2O3, and SiO2 catalyze the oxidative conversion of methanol to formaldehyde, methylformate, and dimethoxymethane with unprecedented rates and high combined selectivity (>99 percent) and yield at low temperatures (300-400 K). Supports influence turnover rates and the ability of RuO2 domains to undergo redox cycles required for oxidation turnovers. Oxidative dehydrogenation turnover rates and rates of stoichiometric reduction of RuO2 in H2 increased in parallel when RuO2 domains were dispersed on more reducible supports. These support effects, the kinetic effects of CH3OH and O2 on reaction rates, and the observed kinetic isotope effects with CH3OD and CD3OD reactants are consistent with a sequence of elementary steps involving kinetically relevant H-abstraction from adsorbed methoxide species using lattice oxygen atoms and with methoxide formation in quasi-equilibrated CH3OH dissociation on nearly stoichiometric RuO2 surfaces. Anaerobic transient experiments confirmed that CH3OH oxidation to HCHO requires lattice oxygen atoms and that selectivities are not influenced by the presence of O2. Residence time effects on selectivity indicate that secondary HCHO-CH3OH acetalization reactions lead to hemiacetal or methoxymethanol intermediates that convert to dimethoxymethane in reactions with CH3OH on support acid sites or dehydrogenate to form methylformate on RuO2 and support redox sites. These conclusions are consistent with the tendency of Al2O3 and SiO2 supports to favor dimethoxymethane formation, while SnO2, ZrO2, and TiO2 preferentially form methylformate. These support effects on secondary reactions were confirmed by measured CH3OH oxidation rates and selectivities on physical mixtures of supported RuO2 catalysts and pure supports. Ethanol also reacts on supported RuO2 domains to form predominately acetaldehyde and diethoxyethane at 300-400 K. The bifunctional nature of these reaction pathways and the remarkable ability of RuO2-based catalysts to oxidize CH3OH to HCHO at unprecedented low temperatures introduce significant opportunities for new routes to complex oxygenates, including some containing C-C bonds, using methanol or ethanol as intermediates derived from natural gas or biomass.

• Research Organization: Lawrence Berkeley National Lab. (LBNL), Berkeley, CA (United States)
• Sponsoring Organization: USDOE Director. Office of Science. Office of Basic Energy Sciences. Chemical Sciences Division; British Petroleum. Methane Conversion Cooperative Research Program. University of California at Berkeley (US)
• DOE Contract Number: AC03-76SF00098
• OSTI ID: 837401
• Report Number(s): LBNL-54295; R&D Project: 404101; TRN: US200506%%109
• Journal Information: Journal of Physical Chemistry B, Vol. 109, Issue 6; Other Information: Submitted to Journal of Physical Chemistry B: Volume 109, No.6; Journal Publication Date: 2005; PBD: 4 Mar 2004
• Country of Publication: United States
• Language: English

Related Subjects

03 NATURAL GAS
09 BIOMASS FUELS
10 SYNTHETIC FUELS
37 INORGANIC
ORGANIC
PHYSICAL AND ANALYTICAL CHEMISTRY
ACETALDEHYDE
BIOMASS
CATALYSTS
DEHYDROGENATION
ETHANOL
FORMALDEHYDE
ISOTOPE EFFECTS
KINETICS
METHANOL
METHYLAL
NATURAL GAS
OXIDATION
REACTION KINETICS
RUTHENIUM OXIDES
SECONDARY REACTIONS
TRANSIENTS
RUTHENIUM OXIDE OXIDATION OF METHANOL AND ETHANOL