The formation of methyl acetate during the conversion of CH4 with N2O and CO over heterogeneous catalysts containing both rhodium and iron phosphate was studied. For two series of Rh-doped FePO4 catalysts prepared by different methods, the optimum atomic ratios of Rh/Fe for methyl acetate formation are 1:600-1:400. The Rh-FePO4 catalyst prepared from a mixed aqueous solution exhibits a higher rate and turnover frequency for methyl acetate formation than the Rh/FePO4 prepared by the impregnation method. Characterizations with XRD, diffuse-reflectance UV-vis, TEM, and H-2-TPR suggest that Rh3+ ions are mainly incorporated into the lattice of FePO4 in the Rh-FePO4 prepared from the mixed aqueous solution, whereas Rh(III) species probably exist on the surface of FePO4 in the Rh/FePO4 prepared by impregnation. The support of Rh(III) species and FePO4 by MCM-41 by a co-impregnation method can drastically increase the rate and turnover frequency for methyl acetate formation, whereas a two-step impregnation method leads to catalysts without methyl acetate formation. The dual site containing Rh(III) species and FePO4 in close proximity is proposed to account for methyl acetate formation. A possible reaction mechanism has been proposed on the basis of kinetic investigations. (c) 2005 Elsevier Inc. All rights reserved.