Closed loop filtration systems and methods of the present teachings can provide liquid reformable fuels enriched in light end hydrocarbons and/or having reduced content of sulfur and/or other impurities. Such enriched liquid reformable fuels can be used in fuel cell systems having a vaporizer and hydrocarbon fuel reformer such that the fuel cell system can experience less deleterious impact on its components, for example, coking. Filter elements for use in the systems and methods also are provided.