Sour natural gas is processed to remove the sulfur compounds and recover C4+/C5+ hydrocarbons by scrubbing the gas with an amine solution to remove most of the sulfur, followed cooling the gas to remove C4+/C5+ hydrocarbons and more sulfur compounds as liquid condensate to produce a gas having less than 20 vppm of total sulfur. The condensate is sent to a fractionator to recover the C4+C5+ hydrocarbons. The sulfur and hydrocarbon reduced gas is contacted first with zinc oxide and then nickel, to produce a gas having less than 10 vppb of total sulfur which is passed into a synthesis gas generating unit to form a very low sulfur synthesis gas comprising a mixture of H2 and CO. This synthesis gas is useful for hydrocarbon synthesis with increased life of the hydrocarbon synthesis catalyst and greater hydrocarbon production from the hydrocarbon synthesis reactor. Contacting the synthesis gas with zinc oxide further reduces the sulfur content to below 3 vppb.