Date of Award

Summer 8-2-2024

Degree Type

Thesis

Degree Name

Master of Science in General Engineering

Department

Mechanical Engineering

Committee Chair

Richard LaDouceur

First Advisor

Blaine Berrington

Second Advisor

Jack Skinner

Abstract

  • 07Bio-oil is a pyrolysis byproduct that consists of heavily oxygenated organic fractions with low caloric values. There are very few industrial-sized facilities that can process bio-oil into useful hydrocarbons comparable to petroleum products. With the increase in biochar production for remediation efforts and forest clean-up, there is a demand for portable, small-scale refineries that do not require extensive process and safety equipment to convert byproducts into usable fuels. Refining bio-oil via atmospheric hydrodeoxygenation (HDO), the removal of the oxygenated functional groups under an unpressurized hydrogenated atmosphere, results in the upgradation of the heavy hydrocarbons within the bio-oil. This process is understudied due to the lack of control over reaction kinetics and product selectivity at atmospheric pressure. Atmospheric HDO is a desirable process to utilize for the upgradation of bio-oils due to the low costs associated with reaction conditions, less required safety equipment, and an adequate product yield to cost ratio. Iron was selected as the active metal catalyst for this process, due to the simplicity of magnetic recovery for catalyst reuse as well as low cost. Bovine bones are a waste material primarily made of calcium and potassium-rich hydroxyapatite. Pyrolyzing bone creates a thermally stable, high surface area support for metal catalysts with a mesoporous structure and available elements for high activity metal complex formation. The iron/bone-char catalysts for this process design were synthesized using four distinct procedures and characterized. Hydrodeoxygenation was performed with the reaction of the iron/bone-char catalysts and a mixed-feedstock bio-oil produced from a batch pyrolysis reactor within the lab. A bench-size reactor was fabricated to perform catalyst synthesis, hydrodeoxygenation, and condensation, requiring the confinement of the process chemistry within a small-footprint design. It was found that incipient impregnation of aqueous ferric nitrate into the bone-char support improved metal dispersion and created smaller metal clusters on the catalyst surface in comparison with resonant vibratory mixed insoluble magnetite dispersion. Hydrodeoxygenation was performed for each catalyst, resulting in conversions from methyl formate and low molecular weight hydroxyketones towards methanol and ethanol products. The semi-continuous lab-scale reactor was designed with lab-scale pyrolysis reactor output in mind, creating a simple 4-step process for the upgradation, condensation, and distillation of the hydrodeoxygenation products.

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