In an embodiment, a process of making C2+ hydrocarbons comprises contacting a feed comprising a methane steam reforming gas and an additional carbon dioxide with a manganese oxide-copper oxide catalyst to produce a product syngas in a contacting zone under isothermal conditions at a temperature of 620 to 650° C.; and converting the product syngas to C2+ hydrocarbons in the presence of a Fischer-Tropsch catalyst; wherein the methane steam reforming gas has an initial H2:CO volume ratio greater than 3; wherein the product syngas has a H2:CO volume ratio of 1.5 to 3; and wherein the contacting further comprises removing water.