(75d) Autothermal Reforming of Dodecane Over Ru-Ni-Based Aerogel and Xerogel Catalysts
AIChE Annual Meeting
Monday, November 17, 2008 - 1:30pm to 1:50pm
Conversion of hydrocarbon fuels, such as gasoline, methanol, and diesel fuel by reforming is an attractive alternative for onboard production of hydrogen to reduce vehicular emissions. The successful development of a fuel cell-powered vehicle depends on the development of a reliable fuel processor. The choice of the reforming reaction mode in the fuel processor depends on the operating characteristics of the application (like varying power demand, rapid startup, frequent shutdowns) and the type of fuel cell stack (PEMFC or SOFC).
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 operation variables on the ATR of dodecane, which is selected as a jet fuel surrogate to simplify the reaction study and the interpretation of the test results. Newly designed RuO-NiO-CeO2-Al2O3 aerogel and xerogel catalysts have been successfully prepared with various loadings of Ni by the combination of sol-gel method and supercritical drying technique and oven drying, respectively, for the dodecane reforming. They were characterized by X-ray diffraction (XRD), temperature-programmed reduction (TPR), temperature-programmed oxidation, pore size distribution, and BET surface area measurements. The autothermal reforming of dodecane was investigated in a microreactor setup at different reaction temperatures, space velocity, oxygen/carbon ratio and steam/carbon ratio. The aerogel catalysts exhibit unusual physical and chemical properties, as manifested in very large specific surface area, well-defined pore size distribution and good textural stability when compared to xerogel catalysts, as well as the conventional impregnated catalysts.
The results from the microreactor experiments and catalyst characterization will be presented and the effect of the operation variables on the hydrogen yield, carbon formation and product gas composition will be discussed.