(583bx) Conversion of Supercritical Bioethanol Into Hydrocarbons Over HZSM-5 Zeolite

Vanous, K., University of Washington
Pfaendtner, J., University of Washington
Resende, F., University of Washington

Ethanol is a major product of the biofuel industry, though its use as a fuel additive presents many issues including costly distillation to separate ethanol from water, and fungibility problems of the gasoline-ethanol blend (e.g. corrosion in transportation pipelines). The direct conversion of ethanol into gasoline has been studied as an alternative route in which bioethanol is converted into a feedstock for directly building hydrocarbon mixtures that comprise gasoline. Benefits to this process include the production of fuels that are compatible with current transportation infrastructure, and reduced energetic costs associated with distillation since aqueous ethanol is suitable for this application. The ethanol-to-gasoline (ETG) process is normally carried out at temperatures of 300-400°C and 1 atm in the presence of a zeolite catalyst (HZSM-5). Extensive catalyst deactivation due to coke deposition inside the zeolite pores represents the major problem for the viability of the ETG process in industrial applications. This research investigates the use of high pressure to reach supercritical ethanol conditions as a potential means to simultaneously reduce coke formation and catalyst deactivation. Supercritical fluids are known for their excellent solvation properties, such as the ability of typically polar solvents to, at supercritical conditions, dissolve organic compounds. It is thus hypothesized that performing the ETG reaction at supercritical ethanol conditions will aid in dissolving the aromatic coke molecules formed during reaction and prevent them from depositing on the catalyst. Initially, ethanol is dehydrated to ethylene and water, producing permanent gases and an aqueous phase, followed by the transformation of ethylene into higher hydrocarbons, leading to organic and solid (coke) phases. GC and GC/MS with FID are currently being used to analyze the aqueous and organic phases, respectively, while GC with TCD is being used to analyze the permanent gases. FTIR and elemental analysis are being used to characterize the coke. Computational studies will be performed to lend additional insight on the ETG process. The reaction mechanism and kinetics will be studied using density functional theory-based molecular simulation, and Car Parinello Molecular Dynamics (CPMD) will be used to model zeolite/aromatic interactions.