Date of Award

Summer 7-17-2015

Level of Access

Campus-Only Dissertation

Degree Name

Doctor of Philosophy (PhD)

Department

Chemical Engineering

Advisor

Adriaan van Heiningen

Second Committee Member

M. Clayton Wheeler

Third Committee Member

William J. DeSisto

Abstract

In the effort to mitigate greenhouse gas emissions and reduce dependency upon fossil fuel resources, lignocellulosic biomass has attracted considerable interest due to its renewable nature, natural abundance, and ability to sequester carbon dioxide. A long-time consumer of lignocellulosic biomass, the pulp and paper industry produces an organic-rich by-product stream known as spent liquor which contains lignin, carbohydrate degradation products, and extractives along with inorganic chemicals used during pulping. This liquor is burned for steam and energy generation as well as chemical recovery, but in many modern mills this operation is the bottleneck of the process. Up to one-third of this by-product stream can be repurposed without affecting steam and energy requirements of the facility and has the potential to be a feedstock for the production of value-added products.

Thermochemical conversion of hardwood soda-anthraquinone spent liquor into bio-oil was studied for producing a significantly deoxygenated bio-oil that could be used in lieu of fossil fuel resources for fuels and chemicals synthesis. This work began with fast pyrolysis of an oxidized lignin model compound, muconic acid, mixed with stoichiometric amounts of formic acid and neutralized using various alkali and alkaline earth cations. The motivation for studying these salts is that it was recently shown that pyrolysis of mixtures of biomass-derived levulinic acid and formic acid calcium salts produced a highly deoxygenated bio-oil; furthermore, pyrolysis of mixtures of lignin and formate produced a bio-oil with an improved yield and energy density over traditional pyrolysis oils. The volatile products obtained were highly deoxygenated.

Following the model compound studies, soda-anthraquinone spent pulping liquor was subjected to oxidation and thermal pretreatments to see if the recalcitrance of the lignin fraction of the liquor to thermochemical conversion could be overcome upon pyrolysis with and without the addition of sodium formate as an in situ hydrogen donor and catalyst. Both weak and concentrated (18.6 and 41 wt% dry solids, respectively) spent liquor were studied. The dominant compounds in the bio-oil obtained are phenols. The addition of sodium formate in this work increases the yield of the bio-oil, but does not have an effect on the quality.

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