Lanthanide-promoted rhodium-containing supported catalysts that are active for catalyzing the net partial oxidation of methane to CO and H2 are disclosed, along with their manner of making and high efficiency processes for producing synthesis gas employing the new catalysts. A preferred catalyst comprises highly dispersed, high surface area rhodium on a granular zirconia support with an intermediate coating of a lanthanide metal and/or oxide thereof and is thermally conditioned during catalyst preparation. In a preferred syngas production process a stream of methane-containing gas and O2 is passed over a thermally conditioned, high surface area Rh/Sm/zirconia granular catalyst in a short contact time reactor to produce a mixture of carbon monoxide and hydrogen.