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.