NOVELTY - A method (M1) of subjecting olefin containing gas to hydrogen treatment involves introducing hydrogen and hydrocarbon feed gas (1a, 1b) containing olefins, alkanes, hydrogen, carbon dioxide, and sulfur compounds into hydrotreater; where the hydrotreater is a shell and tube catalytic reactor (4) with catalyst filled tubes, the shell having inlet for introduction of heat exchange medium to cool the tubes, and outlet for removal of the heat exchange medium; and removing the hydrocarbon feed gas from the tubes    USE - For subjecting an olefin containing gas to hydrogen treatment for converting olefin compounds into saturated compounds; for reducing organic sulfur compound content from hydrocarbon gas (claimed); for producing enriched hydrogen gas from hydrocarbon fuel sources such as natural gas.    ADVANTAGE - The process reduces olefin content of hydrocarbon feed stream by subjecting the hydrocarbon feed to isothermal hydrotreatment, in a shell and tube reactor, this arrangement allows for better control of the temperature of the resultant dehydrogenated hydrocarbon stream. The isothermal arrangement requires less capital expenditure than the multiple stage arrangement. The isothermal arrangement can be used in situations where the hydrogen content of the feed gas is not easily controllable, whereas the multiple stage arrangement can not.    DETAILED DESCRIPTION - A method (M1) of subjecting an olefin containing gas to a hydrogen treatment where olefin compounds are converted into saturated compounds, involves introducing hydrogen and a hydrocarbon feed gas (1a, 1b) containing olefins, alkanes, hydrogen, carbon dioxide, and sulfur compounds into a hydrotreater where olefins are converted into saturated compounds and organic sulfur compounds are converted into hydrogen sulfide; where the hydrotreater is a shell and tube catalytic reactor (4) containing catalyst filled tubes, the hydrogen and hydrocarbon feed gas is introduced into the catalyst filled tubes, and the shell having at least one inlet for introduction of a heat exchange medium to cool the catalyst filled tubes, and at least one outlet for removal of the heat exchange medium, and where the hydrocarbon feed gas is introduced into the catalyst filled tubes at an inlet temperature of 400-525 degrees F; and removing the hydrocarbon feed gas from the catalyst filled tubes of the hydrotreater at a temperature that differs from the inlet temperature by not greater than 30 degrees F.    INDEPENDENT CLAIMS are included for the following:    (1) a method (M2) of treating a hydrocarbon gas to reduce the olefin content and organic sulfur compound content involving the method (M1); and subjecting the hydrocarbon feed removed from the hydrotreater to a desulfurization step; and    (2) a system for preparing a hydrogen-enriched gas from a hydrocarbon feed stream, comprising a catalytic hydrotreater containing a shell and tube reactor where the tubes contain a catalyst for hydrogenation of olefins, the shell and tube reactor further having a first inlet for introducing a hydrocarbon feed, or a mixture of hydrocarbons and hydrogen, into the tube-side of the reactor, and a first outlet for removing a hydrocarbon stream having reduced olefin content from the tube-side of the reactor, the shell and tube reactor further having a second inlet for introducing a heat exchange medium to the shell-side of the reactor, and a second outlet for removing the heat exchange medium from the shell-side of the reactor, an adsorber having an adsorbent bed containing an adsorbent for removal of hydrogen sulfide from a hydrocarbon gas stream, the adsorber further containing an inlet for introduction of a hydrocarbon gas stream containing sulfur compounds, and an outlet for discharging a desulfurized hydrocarbon gas stream, a first conduit in fluid communication with the first outlet of the reactor and in fluid communication with the inlet of the adsorber for introducing at least a portion of the hydrocarbon stream having reduced olefin content to the adsorber, a hydrocarbon reformer comprising an inlet for introducing a desulfurized hydrocarbon gas stream and an outlet for discharging a hydrogen-enriched synthesis gas, and a second conduit in fluid communication with the outlet of the adsorber and in fluid communication with the inlet of the reformer for introducing at least a portion of the desulfurized hydrocarbon gas stream to the reformer.    DESCRIPTION OF DRAWING(S) - The figure shows a flow chart of the process of subjecting an olefin containing gas to hydrogen treatment where olefin compounds are converted into saturated compounds.    Hydrocarbon feed (1)    Natural gas (1a)    Refinery gas (1b)    Hydrogen stream (2)    Heat exchanger (3)    Catalytic reactor (4)    Adsorbers (7, 8)    Desulfurized/hydrotreated gas. (9)