Date of Award

Spring 5-3-2024

Level of Access Assigned by Author

Open-Access Thesis

Degree Name

Master of Science (MS)

Department

Chemical Engineering

Advisor

Clayton Wheeler

Second Committee Member

Sampath Gunukula

Third Committee Member

Sampath Karunarathne

Abstract

In order to meet CO2 emission standards, set by the climate accord in 2015, decarbonizing the transportation sector must become a priority globally. While electric vehicles are becoming more widely used, decarbonizing long distance transportation (e.g.., trucks, airplanes, marine vessels) is still a major concern, contributing over 50% of GHG emissions from transportation in 2018. To bridge this limitation of electric vehicles, biofuel is a viable alternative, having high energy density comparable to conventional fuels from crude oil. Renewable crude oil (biofuel) produced by Thermal DeOxygenation (TDO) is an interesting option as a cleaner intermediate to produce diesel and jet fuels.

TDO oil is produced from cellulosic biomass, but distillate fractions of this oil are unusable as drop-in fuels (having low cetane numbers) due to high aromatic content, thus requiring an upgrading process. Hydrogenation and ring opening are current technologies that can employed to achieve this. While hydrogenation only saturates the hydrocarbons, ring opening cleaves C-C bond. Therefore, both hydrogenation and ring opening of TDO oil is required to improve the engine combustion properties. In this work, ring opening is carried out over synthesized catalysts (Ir/SiO2, Ir/Al2O3, Ir/CsBEA and Ir/BEA) in a downflow, packed bed reactor to assess the resulting fuel characteristics. Reactants and products were analyzed by GC-MS, and gaseous products analyzed using a GC-FID.

In this research, we compared the four catalysts using a narrow cut of hydroprocessed TDO oil, we determined that the zeolite-based catalysts performed poorly due to surface acidity. However, the impregnated catalysts fared much better, and the Ir/SiO2 catalyst showed the highest yield to desired ring opening products (e.g., 1-ethyl-2-methylcyclohexane, 1-methyl-2-propylcyclohexane, and 1,4-dimethyl-2-propylcyclohexane), with lower yield to undesired dehydrogenation and cracking products. Using a broader cut of hydroprocessed TDO Oil, similar results were observed.

In optimizing the reaction conditions of using Ir/SiO2, we determined that at temperatures above 310 °C, cracking becomes significant, and a variety of light gases are formed. The properties of the resulting product oil showed close similarity to standard ultra-low sulfur diesel and JP-8 fuels. This research suggests that incorporating hydrogenation and ring opening is enough to achieve an upgraded oil of cetane number (CN) of 39 for use as a blend stock in diesel and aviation applications.

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