A review of catalytic issues and process conditions for renewable hydrogen and alkanes by aqueous-phase reforming of oxygenated hydrocarbons over supported metal catalysts

We have recently developed a single-step, low-temperature process for the catalytic production of fuels, such as hydrogen and/or alkanes, from renewable biomass-derived oxygenated hydrocarbons. This paper reviews our work in the development of this aqueous-phase reforming (APR) process to produce, hydrogen or alkanes in high yields. First, the thermodynamic and kinetic considerations that form the basis of the process are discussed, after which reaction kinetics results for ethylene glycol APR over different metals and supports are presented. These studies indicate Pt-based catalysts are effective for producing hydrogen via APR. Various reaction pathways may occur, depending on the nature of the catalyst, support, feed and process conditions. The effects of these various factors on the selectivity of the process to make hydrogen versus alkanes are discussed, and it is shown how process conditions can be manipulated to control the molecular weight distribution of the product alkane stream. In addition, process improvements that lead to hydrogen containing low concentrations of CO are discussed, and a dual-reactor strategy for processing high concentrations of glucose feeds is demonstrated. Finally, various strategies are assembled in the form of a composite process that can be used to produce renewable alkanes or fuel-cell grade hydrogen with high selectivity from concentrated feedstocks of oxygenated hydrocarbons. (C) 2004 Elsevier B.V. All rights reserved.