Date of Award

Fall 12-2020

Level of Access

Open-Access Thesis

Degree Name

Master of Science (MS)

Department

Chemical Engineering

Advisor

M. Clayton Wheeler

Second Committee Member

Thomas J. Schwartz

Third Committee Member

William J. DeSisto

Additional Committee Members

Brian G. Frederick

Douglas W. Bousfield

Abstract

Biomass thermal conversion processes, such as pyrolysis, tend to produce mixtures of mono- and poly-aromatic species. While the high aromatic content is desirable in gasoline fractions, middle-distillate cuts, particularly jet fuel and diesel, require upgrading via hydrogenation and ring opening to achieve better combustion characteristics. There have been many proposed methods for producing drop-in fuels from woody biomass, one of them being Thermal DeOxygenation (TDO). The TDO process converts organic acids from cellulose hydrolysis into a low-oxygen bio-oil containing large amounts of substituted naphthalene compounds.

Poly-aromatic molecules, such as those found in TDO oil, have low cetane numbers (CN), particularly due to their high aromatic content. Even after deep hydrogenation, certain combustion characteristics, such as specific volume, hydrogen content, and CN may still be below required specifications. Thus, naphthenic ring opening coupled with aromatic hydrogenation is the desired process to enhance the fuel characteristics.

This research focuses on the hydrogenation of 2-methylnaphthalene (2-MN) to increase the CN. These reactions are performed industrially using a precious metal catalyst (e.g., based on palladium or platinum), but because of their intrinsically high cost and sensitivity to impurities, we focused on supported nickel catalysts to perform the desired reactions. We hydrogenated 2-MN in a down-flow trickle-bed reactor at a variety of operating conditions.

In this research, we compared several Ni catalysts to a commercial Ni catalyst with respect to reaction rate and product selectivity. Impregnated Ni catalysts showed higher activation energies and lower reaction rates than the commercial catalysts, but coprecipitated Ni catalysts produced products with similar selectivities as the commercial catalyst. We found that higher amounts of Ni in the coprecipitated catalysts slightly increased the cis/trans-methyldecalin ratio, whereas higher temperatures decreased the same ratio. Impregnated coprecipitated catalysts with Ni and a precious metal also changed the cis/trans-methyldecalin ratio. Although bimetallic IrNi and PdNi catalysts barely altered the ratio, the PtNi catalyst was selective towards trans-methyldecalin, whereas RuNi was selective towards cis- methyldecalin. We provided a possible explanation for that observed selectivity as well as other trends throughout this research.

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