Computational and experimental investigation of catalytic hydrocarbon fuel processing for autothermal hydrogen production

Abstract

Catalytic conversion of hydrocarbon fuels within the context of the operation of a fuel processor for supplying hydrogen to vehicular and stationary fuel cells is investigated using computer-based modeling/simulation studies and experimental techniques. The computational part of this work involves the quantitative description of the proposed fuel processor/fuel cell system, and the assessment of various combinations of hydrocarbon fuels and fuel processing routes on the basis of their hydrogen yields. Computer simulations indicate the possible advantages of the conversions of liquefied petroleum gas (propane + n-butane) by an indirect partial oxidation (combined total oxidation/steam reforming) mechanism for use in mobile fuel cell applications and of methane (natural gas) by a direct, one-step partial oxidation mechanism in small-scale stationary fuel cell applications. Experimental studies involve the investigation of total oxidation and steam reforming of propane and n-butane over a bimetallic Pt-Ni catalyst. The catalyst is thought to have the potential of driving indirect partial oxidation efficiently by facilitating heat transfer between the two reactions. For both hydrocarbons (a) the oxidation activities are found to follow the order of Pt>Pt-Ni>Ni, (b) Pt metal seems to drive oxidation qualitatively, (c) dispersion of Pt over Ni is likely to affect the oxidation activities. Steam reforming of n-butane over Ni and Pt-Ni catalysts have shown different characteristics, particularly at 648 K in terms of hydrogen selectivities. Assessment of reaction kinetics at 648 K gave reaction orders of 1.20 and -0.18, with respect to n-butane and steam, respectively and an activation energy of 80.7 kJ mol-1 in the 603 K-668 K range.