1. G. Lopes, A. Ferreira, A. P. Gonçalves and J. B. Branco Instituto Tecnológico e Nuclear, Estrada Nacional 10, 2686-953 Sacavém, Portugal Unidade de Ciências Químicas e Radiofarmacêuticas The 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. Melting temperatures between 484 ºC and 506 ºC; 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 CeO 2 formation. XRD patterns for the molten salts Characteristic bands of CO 3. New features are not seen before and after the catalytic reaction. Slight contraction of the CeO 2 lattice is observed. The study of the Gas Hourly Space Velocity (GHSV, mL of CH 4 / g of catalyst. h) and CH 4 / O 2 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 (mL CH 4 /g.h), m≈25 g. IR results for the molten salts Selectivity results for GHSV = 2863 and CH4/O2 molar ratio = 2 Lower GHSV and CH 4 /O 2 molar ratio influences the catalyst activity. CO 2 is the only product of the reaction. [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. This work was supported by FCT, under contract number PTDC/QUI/72290/2006 All experiments were carried out using an K 2 CO 3 -Li 2 CO 3 (50:50 wt.%) eutectic mixture (T=600 ºC) as solvent and the cerium molten carbonates prepared by the addition to this mixture of an appropriate amounts of Ce 2 (CO 3 ) 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 o C (hold 15 min) until 1000 o C at a 10 o C/ min heating rate), X-Ray Powder Diffraction (XRD, reflection geometry with a PANalitycal X’Pert Pro diffractometer using Cu, ka monochromatic radiation l=1.5406 Å), 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). Effect of GHSV at CH 4 /O 2 molar ratio = 2 Effect of CH 4 /O 2 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 CeO 2 lattice is observed. DSC tests after catalytic test DSC tests before catalytic test