Process for steam reforming of hydrocarbons

In a process for steam reforming gaseous hydrocarbons selected from the group consisting of methane, liquefied natural gas, liquefied petroleum gas, butane, hexane, petroleum light distillates, naphtha and off-gas from processes utilizing various hydrocarbons as feeds, wherein the hydrocarbons are passed in a gaseous state through a catalyst together with steam at an elevated temperature under pressure whereby the hydrocarbons are subjected to a steam reforming reaction wherein the resulting product gas consists mainly of hydrogen, carbon monoxide, carbon dioxide, methane and steam with the relationship among these product components being represented by the following equilibrium equations:

• CH.sub.4 + H.sub.2 O.revreaction.CO + 3H.sub.2
• co + h.sub.2 o.revreaction.co.sub.2 + h.sub.2
• the improvement wherein when said off-gas is the feed, said off-gas comprises paraffinic hydrocarbons and up to about 15% by volume of olefinic hydrocarbons and wherein said catalyst consists essentially of from 3% to 30% by weight of nickel in terms of NiO, based on the catalyst, at least 2 mg-atoms of silver per 100 gram of the catalyst, at least one rare earth element in an atomic ratio of the rare earth element to silver of 0.2 to 10, and a heat-resistant carrier, the elevated temperature being from 350 to 900.degree. C. and the pressure being from 1 to 50 kg/cm.sup.2.