Energy demand continues to climb as the world population grows. Meanwhile petroleum reserves are diminishing. Developing new energy sources and more efficient technologies is extremely important. At the same time, the level of emissions and exhaust gases needs to be reduced to minimize their contribution to the greenhouse effect. Environmentally friendly energy solutions are being sought, especially for mobile applications. For example, the auxiliary power units (APUs) can increase fuel economy by displacing engine idling. The combination of an on-board reformer and a SOFC would enable commercial fuels such as jet fuel and diesel to be used as a hydrogen source because of the existing infrastructure and high energy density of these fuels. More popular in transportation, military, and industrial applications, commercial fuels could be a good first step toward a hydrogen-based society.
The conversion of hydrocarbon fuels to hydrogen can be carried out by several different reforming approaches including steam reforming, partial oxidation, and autothermal reforming. Autothermal reforming (ATR) is regarded as the best option since the combustion of some of the fuel supplies the energy required for the reforming reaction and better sulfur tolerance than steam reforming (SR). ATR reactors are smaller, quick-starting and faster-responding than SR reactors, and give higher hydrogen concentration. Faster startup time and better transient response can be attained by tuning the feed stoichiometry. Additionally, the water gas shift reaction, which proceeds simultaneously, reduces the CO content of the hydrogen-rich gas; also, the methane content of the gas is lower than the other methods. The operation variables have to be optimized according to the catalyst employed to minimize carbon formation and methane production.
The present experimental study has been undertaken to investigate the effect of the operation variables on the ATR of n-dodecane, which is selected as a jet fuel surrogate to simplify the reaction study and the interpretation of the test results.
Promoted nickel xerogel catalysts were prepared by sol-gel method. Catalysts were characterized by XRD, TPR, TPD of H2 & CO2, BET surface area and porosity measurements. The autothermal reforming experiments were performed in a fixed bed micro-reactor system in a temperature range of 600-800°C and space velocity of the order of 100,000 hr-1. The reaction feed containing n-dodecane, water, oxygen and carrier gas were sent through a vertical flow quartz reactor containing the catalyst. The product gases were analyzed by two online GCs.
The results from these experiments will be discussed during the presentation in terms of the effect of operation variables on the hydrogen yield and product gas composition.
Acknowledgement: The authors acknowledge financial support from ARO grant (W911NF-10-1-0514).