A fuel supply assembly which receives a supply of liquid fuel feedstock including hydrocarbons having higher and lower hydrocarbon content and high molecular weight sulfur-containing compounds, the higher hydrocarbon content and high molecular weight sulfur containing compounds being less volatile that the lower hydrocarbon content. The fuel supply assembly supplies fuel to a fuel cell assembly and has a housing unit adapted to house the liquid fuel feedstock so that the liquid fuel feedstock is subjected to vaporization conditions to allow at least a portion of the liquid fuel feedstock to vaporize to form fuel feedstock vapor, the vaporization conditions being such that the concentration of lower hydrocarbon content is higher and the concentration of higher hydrocarbon content and high molecular weight sulfur containing compounds is lower in the fuel feedstock vapor than in the liquid fuel feedstock. A collecting unit is also provided in the fuel supply assembly and the collecting unit has a first end coupled with the housing unit and a second end adapted to be coupled with the fuel cell assembly which collects the fuel feedstock vapor from the housing unit to make the fuel feedstock vapor available to the fuel cell assembly.