(21b) Application of Ti-Doped MoO2 microspheres Prepared By Spray Pyrolysis to Partial Oxidation of N-Dodecane

Power generation by hydrogen fuel cells is an important clean energy technology because it increases energy utilization efficiency and decreases greenhouse gas emissions. Hydrogen gas can be produced from reforming of liquid hydrocarbon fuels, such as gasoline, diesel and jet fuel. The reforming of higher hydrocarbons is a challenging proposition because of the severe coking problems. Therefore, development of a catalyst with coking resistance is crucial for successfully reforming a full range of liquid fuels. Mo-based catalyst is another inexpensive catalyst that has been found to be active for fuel reforming and as an alternative anode material for solid oxide fuel cells due to its coking resistance. The present investigation is focused on improving the performance of molybdenum oxide (MoO₂) by doping with Ti for the partial oxidation (POX) of n-dodecane. Ti-doped MoO₂ nanoparticles were synthesized via solvothermal cracking of polycrystalline MoO₃ microparticles prepared by ultrasonic spray pyrolysis in the presence of a Ti precursor. Partial oxidation of n-dodecane was conducted at 850 °C with an O₂/C ratio of 0.5. The 6 at% Ti-doped MoO₂ was fully converted into orthorhombic carbide phase (β-Mo₂C) during the reaction. This carbide sample showed high catalytic activity and stability with conversion and H₂ yield of 94.4% and 86.3% after 24 h on stream, respectively. On the other hand, un-doped MoO₂ was partially converted into the carbide phase during the reaction, which led to mixed oxide and carbide phases. This mixed phase showed poor catalytic activity and rapid deactivation after only 6 h of operation. Our ammonia temperature programmed desorption (TPD) and pyridine diffuse reflectance infrared Fourier transform (DRIFT) tests suggest that the addition of Ti to MoO₂ improves both the density and strength of Lewis acid sites, and hence improves hydrocarbon activation. This increased surface carbon activation would enhance the carburization process of the Ti-doped MoO₂ catalyst and retain the carbide phase under the POX condition.