A comparative study of fuels for on-board hydrogen production for fuel-cell-powered automobiles

Seven common fuels are compared for their utility as hydrogen sources for proton-exchange-membrane fuel cells used in automotive propulsion. Methanol, natural gas, gasoline, diesel fuel, aviation jet fuel, ethanol, and hydrogen are the fuels considered. Except for steam-reforming methanol and using pure hydrogen, all processes for generating hydrogen from these fuels require water–gas shift reactors of significant size. This occurs because their higher processing temperatures produce unacceptably large amounts of CO. All processes require low- or zero-sulfur fuels, and this may add cost to some of them. Fuels produced by pure steam-reforming contain ∼70–80% hydrogen, those by pure partial oxidation ∼35–45%. The lower percentages may adversely affect cell performance. Pure steam-reforming suffers from poor transient operation. Theoretical input energies do not differ markedly among the processes for generating hydrogen from organic-chemical fuels. Pure hydrogen has formidable distribution and storage difficulties. The factors considered in this work make some combination of partial oxidation and steam-reforming of methanol technically the leading candidate for on-board generation of hydrogen for automotive propulsion. The possible use of methanol suffers from a lack of infrastructure and solubility in water combined with toxicity. Methanolʹs disadvantages have stimulated extensive current research employing other primary fuels for this purpose.