Reforming of Diesel Fuel in a Micro Reactor

Abstract

Reforming of diesel fuel is challenging but very attractive for hydrogen production. It can facilitate the market entrance of fuel cells due to the existing infrastructure for distribution of diesel fuel. Reforming in micro reactors enables good heat transfer and therefore small and compact fuel processing systems e.g. for electrical energy generation in auxiliary power units.Due to the complexity of diesel, reforming of different diesel components and conversion intermediates in a micro reactor is investigated systematically within this work. Methane and propane were applied as conversion intermediates and hexadecane as a diesel surrogate. All experiments were conducted over a rhodium catalyst on Al2O3 or CeO2.For evaporation of the higher boiling hydrocarbons a micro structured injection nozzle was fabricated to create a fine hydrocarbon spray which evaporates in water vapour. Furthermore a complex gas chromatographic method to analyse hydrocarbons up to C16 and the permanent gases in one analysis run was developed.Experimental results show that the turnover frequency of the fuel molecules in the feed decreases linearly for straight chain hydrocarbons with an increasing number of carbon atoms. Calculations show that the observed conversions and product gas compositions are close to the thermodynamic equilibrium. The catalyst system Rh/CeO2 offers better reforming performance and higher resistance to coking apparently due to less acidic sites compared to Al2O3 and the oxygen storage capacity of CeO2.The ongoing work will examine the reforming behaviour of more model diesel fuel components e.g. mixtures of hexadecane and methylnaphthalene or synthetic diesel fuel. Experiments will be conducted in an optimised micro reformer, which disposes the heating energy by burning e.g. fuel cell off-gases. This also offers the consideration of start up and load changing behaviour.