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Abstract
Stringent legislation on control of vehicle exhaust emissions has led to consideration of alternative means of reducing emissions, with hydrogen fuel cell powered vehicles being accepted as one favoured possibility. However, the difficulties of storing and distributing hydrogen as a fuel are such that the conversion of more readily available fuels to hydrogen on board the vehicle may be required. The production of hydrogen by the partial oxidation of isooctane over Rh/Al2O3, Rh/CeO2-?l2O3 and Rh/CeO2-ZrO2 catalysts has been investigated. Oxidation was initiated at temperatures between 200 ?220 oC. The yield of hydrogen was 100%. CeO2-ZrO2 was found to be the best support. The production of hydrogen by the autothermal reforming of artificial gasoline has been studied. Part of gasoline is oxidised to produce heat and steam to promote the steam reforming of unburnt gasoline to produce hydrogen. The use of platinum impregnated on ceria supports (active for oxidation) and a commercial nickel based catalyst (Ni-com), for steam reforming of gasoline have been explored. Initiation of oxidation of artificial gasoline over unreduced platinum based catalysts occurred at temperature as low as 150 oC, depending on the oxygen:carbon ratio and the liquid hydrocarbon used. Detailed kinetic studies of the steam reforming of isooctane and artificial gasoline (a mix of cyclohexane, isooctane and octane) over pre-reduced Ni-com catalysts showed that the reaction was 0.17 order in isooctane and 0.54 order in steam, whilst the reaction was 0.08 order in artificial gasoline and 0.23 order in steam. Mechanisms have been proposed to account for the dual site surface reaction with dissociative adsorption of isooctane or artificial gasoline and steam. Combined oxidation and steam reforming systems (autothermal reforming) using Pt/CeO2 as a front catalyst bed and Ni-com as the rear bed at the feed conditions of oxygen:carbon (O:C) ratio of ca.1.2 and steam:carbon (S:C) ratio of ca.2, produces ca. 3.5 moles of hydrogen per mole of gasoline fed. The system reaction temperature could be controlled by adjusting the O:C and S:C ratios in feed.