(343f) Ring-Opening of Thermal Deoxygenation (TDO) Oil over Supported Metal Catalysts to Improve Diesel Engine Properties

While the commercial power sector is improving its carbon footprint, decarbonizing the transport sector still has much room for improvement. Although electric vehicles are becoming more widely used, applications for long distance travel (such as in trucks and airplanes) are still of concern. Renewable crude oil that has been produced by UMaine’s Thermal DeOxygenation Process (TDO oil) is an interesting option as a cleaner alternative to conventional diesel and jet fuels. Simple hydrogenation of crude TDO oil is not sufficient because the hydrogenated oil contains many cyclic hydrocarbons, such as cyclo-hexane, decalin and methyl-decalin, that don’t perform well in diesel engines. Therefore, the oil must be further upgraded. Breaking the cyclic molecules (ring-opening) can improve the diesel engine combustion properties. In this work, ring-opening is carried out over synthesized catalysts (Ir/SiO₂, Ir/Al₂O₃, Ir/CsBEA and Ir/BEA).

Liters of TDO oil were produced from decomposition of calcium salts of levulinic and formic acids which are made from C₆ sugars in woody biomass by acid hydrolysis and dehydration using dilute sulfuric acid as a catalyst. The TDO oil was then hydrogenated in a downflow reactor packed with Ni/SiO₂-Al₂O₃ catalyst to produce the feedstock for the ring-opening studies. The four novel catalysts which were synthesized in our lab were each evaluated for their ring-opening ability in a downflow, packed bed reactor, maintaining the same catalyst mass, and packing methodology for each experiment. The hydrogenated oil and the ring-opening reaction products were analyzed using a gas chromatograph-mass spectrometer GCMS. The reactor temperature and feed flowrate were varied to determine the optimum conditions to yield a mixture of compounds that are predicted to have the best engine performance characteristics. Gas reaction products were analyzed using a gas chromatograph with a flame ionization detector.

The Ir/SiO₂ catalyst showed the highest conversion to desired ring-opened products such as 1,2-diethylcyclohexane, 1-methyl-2-propylcyclohexane, 1,2,4-trimethylcyclohexane, and least conversion to undesired dehydrogenated and cracked products. This is likely because Ir/SiO₂ is a monometallic catalyst on an inert support. Although side products, such as dehydrogenated products, were formed on this catalyst, conversion to target compounds was still above 50%.