As oil reserves decline, natural gas will become an increasingly important resource. Lahn et al have reported that approximately half the worlds proven natural gas reserves are situated remote from sizeable markets. For off-shore reserves, conversion to liquid hydrocarbons at the field location on board floating facilities is an attractive option as transport as LNG or by pipeline is often technically inconceivable or uneconomic. This chapter focuses on air separation for off-shore gas conversion. Irrespective of the choice of gas conversion route, the Fist step is syn-gas production. Steam reforming is reported to be the most economical for large-scale syn-gas production although combined reforming can be competitive when the gas price is high. Neither scheme can be considered for offshore application being ruled out because of doubts about reformer tube lifetimes under wave-induced motion and the sheer physical size of the radiant furnace. Of the numerous alternative reforming technologies, autothermal reforming, heat exchanger reforming, catalytic partial oxidation and fluidized bed reforming [Lahn et al, 19921 appear the most promising for off-shore application.