PARTIAL

PARTIAL OXIDATION OF METHANE OVER POTASSIUM-CERIUM MOLTEN CARBONATESG. Lopes, A. Ferreira, A. P. Gonalves and J. B. BrancoInstituto Tecnolgico e Nuclear, Estrada Nacional 10, 2686-953 Sacavm, PortugalUnidade de Cincias Qumicas e Radiofarmacuticas

Introduction and ObjectiveThe applications of molten salts have been well recognized for more than a century. In spite of the use of high temperature corrosive liquids, molten salts offer unique opportunities. Low temperature multi component molten salts, as well as room temperature ionic liquids have been developed for materials processing. Currently, molten salts are finding applications in fuel cell technology, in the field of separation processes of minor actinides from the rest of the fission products that are contained in the irradiated nuclear fuel, for the direct catalytic conversion of methane under mild conditions and the partial oxidation of methane to synthesis gas [1]. Here, we report the synthesis, characterization and behaviour for the partial oxidation of methane of potassium-cerium (K-Ce) molten carbonates. Catalysts Characterization

Melting temperatures between 484 C and 506 C; The addition and increase of cerium % decreases the transition temperature XRD tests were performed before and after the catalytic tests. The melting of the salts leads to the CeO2 formation.XRD patterns for the molten salts

Characteristic bands of CO3.

New features are not seen before and after the catalytic reaction.

Slight contraction of the CeO2 lattice is observed.

Catalytic ResultsThe study of the Gas Hourly Space Velocity (GHSV, mL of CH4 / g of catalyst. h) and CH4 / O2 molar ratio was undertaken. The outlet gas composition was analyzed on-line by gas chromatography (GC) with a thermal conductivity detector (TCD). Catalyst activity was defined as the number of mL of methane converted per g of catalyst and per hour (mLCH4/g.h), m25 g.IR results for the molten saltsSelectivity results for GHSV = 2863 and CH4/O2 molar ratio = 2Lower GHSV and CH4/O2 molar ratio influences the catalyst activity. CO2 is the only product of the reaction.References[1] a) B. Mishra et al., Journal of Physics and Chemistry of Solids, 2005, 66, 396; b) T.R. Griffiths et al., Journal of Alloys and Compounds, 2006, 418, 116; c) J.J. Peng, et al., Applied Catalysis A: General, 2000, 201, L55; d) Y.G. Wei, et al., Journal of Natural Gas Chemistry, 2007, 16, 6.AcknowledgementsThis work was supported by FCT, under contract number PTDC/QUI/72290/2006All experiments were carried out using an K2CO3-Li2CO3 (50:50 wt.%) eutectic mixture (T=600 C) as solvent and the cerium molten carbonates prepared by the addition to this mixture of an appropriate amounts of Ce2(CO3)3 (5 and 15 wt.%). The molten salts were characterized by Differential Scanning Calorimetry (PAC-ATD ADI prototype, DSC recorded under argon-50 mL/min, 20 oC (hold 15 min) until 1000 oC at a 10 oC/ min heating rate), X-Ray Powder Diffraction (XRD, reflection geometry with a PANalitycal XPert Pro diffractometer using Cu, ka monochromatic radiation l=1.5406 ), Infrared Spectroscopy (IR, recorded on a Bruker spectrometer with samples mounted as Nujol mulls) as well as Elemental Analysis (C,H,N, S and O, performed on a CE instrument EA1110 automatic analyzer).ExperimentalEffect of GHSV at CH4/O2 molar ratio = 2Effect of CH4/O2 molar ratio at GHSV= 8520

Molten carbonate with 15% Ce is the only that shows selectivities to hydrocarbons Conversion of methane increases with the increase of the cerium amount.

Phase diagram for the eutectic mixture New features are not seen before and after the catalytic reaction. Slight contraction of the CeO2 lattice is observed.DSC tests after catalytic test

DSC tests before catalytic test