269209 Autothermal Reforming of Dodecane Over Ni-Based Sol-Gel Catalysts
Increasing energy demand, due to the population growth, urges for new and more efficient technologies, which will, also, reduce the level of exhaust gas emissions into the environment. Eco-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 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 US military is the single largest petroleum consumer in the world and jet fuel represents 64% (volume basis) of all petroleum products consumed1. Hence in the present study, we have chosen to investigate the auto thermal reforming (ATR) of dodecane, which is used as a surrogate of commercial jet fuel, for the production of clean hydrogen.
The current existing technologies for the production of hydrogen from hydrocarbon fuels are steam reforming (SR), partial oxidation (POx), combustion and autothermal reforming (ATR). Among all the above methods, ATR is regarded as the best option, because it is a combination of the endothermic SR and the exothermic POX process and exhibits better sulfur tolerance than SR. ATR reactors are smaller, quick-starting and faster-responding than SR reactors. This process requires less energy and helps reduce the amounts of methane and coke produced while providing a high H2 yield and a low CO yield under optimal operating conditions. Additionally, the water gas shift reaction, which proceeds simultaneously, reduces the CO content of the hydrogen-rich gas.
The main obstacles in the development of ATR catalysts for the reforming of higher hydrocarbons are catalyst deactivation by carbon formation and sulfur intolerance. Although supported noble metal (Rh, Ru, Pt, Pd) catalysts provide higher activity and stability compared to Ni catalysts, the price is the key factor for choosing nickel catalysts. In this experimental study, we synthesized Ni-based catalysts which are resistant to carbon formation by incorporating cerium and zirconium species into the catalyst structure by a typical sol-gel method; these catalysts do not display any compromise on hydrogen production. Preparation of metal oxides by the sol-gel method results in the retention of hydroxyl-rich surfaces, which exhibit unique textural and chemical properties compared with those prepared by other conventional methods, along with the attainment of high surface areas.
In the present study, we have prepared sol-gel derived Ni-based catalysts supported on alumina (Al2O3) for the ATR of dodecane. Catalysts were characterized by X-ray diffraction (XRD), temperature programmed reduction (TPR), pore size distribution, hydrogen chemisorption and BET surface area measurements. The autothermal reforming of dodecane was performed in a microreactor setup at different reaction temperatures, space velocity, oxygen/carbon ratio and steam/carbon ratio. The Ni-Ce-Zr-Al2O3 catalyst showed high catalytic activity, low carbon deposition, good resistance to sintering and prolonged stability compared to the other catalysts prepared in the project. 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.