There is a growing need to develop the processes to produce renewable fuels and chemicals due to the economical, political, and environmental concerns associated with the fossil fuels. One of the most promising methods for a small scale conversion of biomass into liquid fuels is fast pyrolysis. The liquid product obtained from the fast pyrolysis of biomass is called pyrolysis oil or bio-oil. It is a complex mixture of more than 300 compounds resulting from the depolymerization of biomass building blocks, cellulose; hemi-cellulose; and lignin. Bio-oils have low heating value, high moisture content, are acidic, contain solid char particles, are incompatible with existing petroleum based fuels, are thermally unstable, and degrade with time. They cannot be used directly in a diesel or a gasoline internal combustion engine. One of the challenges with the bio-oil is that it is unstable and can phase separate when stored for long. Its viscosity and molecular weight increases with time. It is important to identify the factors responsible for the bio-oil instability and to stabilize the bio-oil. The stability analysis of the bio-oil showed that the high molecular weight lignin oligomers in the bio-oil are mainly responsible for the instability of bio-oil. The viscosity increase in the bio-oil was due to two reasons: increase in the average molecular weight and increase in the concentration of high molecular weight oligomers. Char can be removed from the bio-oil by microfiltration using ceramic membranes with pore sizes less than 1 µm. Removal of char does not affect the bio-oil stability but is desired as char can cause difficulty in further processing of the bio-oil. Nanofiltration and low temperature hydrogenation were found to be the promising techniques to stabilize the bio-oil. Bio-oil must be catalytically converted into fuels and chemicals if it is to be used as a feedstock to make renewable fuels and chemicals. The water soluble fraction of bio-oil (WSBO) was found to contain C2 to C6 oxygenated hydrocarbons with various functionalities. In this study we showed that both hydrogen and alkanes can be produced with high yields from WSBO using aqueous phase processing. Hydrogen was produced by aqueous phase reforming over Pt/Al2O3 catalyst. Alkanes were produced by hydrodeoxygenation over Pt/SiO2-Al2O3. Both of these processes were preceded by a low temperature hydrogenation step over Ru/C catalyst. This step was critical to achieve high yields of hydrogen and alkanes. WSBO was also converted to gasoline-range alcohols and C2 to C6 diols with up to 46% carbon yield by a two-stage hydrogenation process over Ru/C catalyst (125 °C) followed by over Pt/C (250 °C) catalyst. Temperature and pressure can be used to tune the product selectivity. The hydroprocessing of bio-oil was followed by zeolite upgrading to produce C6 to C8 aromatic hydrocarbons and C2 to C4 olefins. Up to 70% carbon yield to aromatics and olefins was achieved from the hydrogenated aqueous fraction of bio-oil. The hydroprocessing steps prior to the zeolite upgrading increases the thermal stability of bio-oil as well as the intrinsic hydrogen content. Increasing the thermal stability of bio-oil results in reduced coke yields in zeolite upgrading, whereas, increasing the intrinsic hydrogen content results in more oxygen being removed from bio-oil as H2O than CO and CO 2. This results in higher carbon yields to aromatic hydrocarbon and olefins. Integrating hydroprocessing with zeolite upgrading produces a narrow product spectrum and reduces the hydrogen requirement of the process as compared to processes solely based on hydrotreating. Increasing the yield of petrochemical products from biomass therefore requires hydrogen, thus cost of hydrogen dictates the maximum economic potential of the process.

Depletion of fossil fuel reserves along with growing environmental concerns has shifted focus towards renewable energy sources for liquid fuels production, such as biofuels. Most biofuels, like ethanol, are single-component fuels that cannot meet today's engine specifications unless they are blended with petroleum feedstocks. Current transportation infrastructure uses petroleum fuels that are mixtures of compounds. Therefore, it is important to be able to produce multi-component fuels in a cost effective way, from renewable resources. Aqueous-phase hydrogenation reactions are crucial in converting biomass-derived molecules into liquid fuels and chemicals. It is possible to produce multi-component fuels through the hydrogenation of bio-oils in the aqueous phase. One of the hardest functionalities to be hydrogenated in bio-oils is the carboxylic acids. Our findings on acetic acid hydrogenation studies over monometallic catalysts will be discussed combined with insight learned from DFT calculations. Ruthenium has been shown to be the most active and selective catalyst towards ethanol formation. Acetyl species appears to be a key component as its formation is the rate-determining step for almost all catalysts. Another way of making multi-component fuels is by the liquid-phase processing of the hemicellulose portion of biomass. It will be shown that hemicellulose-derived aqueous feedstocks can be converted into a petroleum feedstock that can readily be processed in existing petroleum refineries to make a variety of fuels. Furfural is produced in high yields from the dehydration of hemicellulose-derived sugar streams. The aldol condensation of furfural with acetone gives highly conjugated C13 compounds along with some polymeric adducts. In the presence of supported metal catalyst these compounds undergo hydrogenation, and at the same time, form heavy cyclic molecules via Diels-Alder reactions. Through hydrodeoxygenation and isomerization over bifunctional catalysts these molecules produce refinery feedstocks, or more specifically, fluid catalytic cracker cycle oil substitutes, having carbon numbers up to C31. This integrated catalytic process can be tuned to adjust the yield of the hydrocarbon products thereby selectively producing jet and diesel fuel range compounds or a heavier petroleum refinery feedstock. This study demonstrates that biomass can produce mixtures of components that can fit seamlessly into petroleum refinery infrastructure.

Due to its low cost and large availability lignocellulosic biomass is being studied worldwide as a feedstock for renewable liquid biofuels. Currently there are several routes being studied to convert solid biomass to a liquid fuel, which involve multiple steps at long residence times thus greatly increasing the cost of biomass processing. Catalytic fast pyrolysis (CFP) is a new promising technology to convert directly solid biomass to gasoline-range aromatics that fit into the current infrastructure. CFP involves the rapid heating of biomass (~500˚C sec-1) in an inert atmosphere to intermediate temperatures (400 to 600 ˚C) in the presence of zeolite catalysts. During CFP, biomass is converted in a single step to produce gasoline-range aromatics which are compatible with the gasoline of the current market. CFP has many advantages over other conversion processes including short residence times (2-10 s) and inexpensive catalysts. The major impediment to the further development of CFP is the lack of fundamental understanding of the underlying chemistry of the process. The first goal of this thesis is to study the underlying chemistry of the CFP process using model compounds in a small pyroprobe micro reactor. For this part of the study the homogeneous thermal decomposition routes of glucose were identified along with the key intermediates. Through isotopic labeling studies the heterogeneous C-C bond forming reactions were determined. Lastly, the relative rates of the homogeneous and heterogeneous reactions were estimated. Since CFP in the small pyroprobe reactor is not scalable the second part of the study focused on designing and building a bench scale fluidized bed reactor to demonstrate CFP on a larger scale. This fluidized bed reactor was used to optimize the CFP of pine wood with ZSM-5 catalyst. The effect of reaction conditions such as temperature and biomass space velocity on the aromatic yield and selectivity was determined. The long term stability of the catalyst was also studied.

<p> Over the past decade, there has been a revival in algal research and attempts at large scale cultivation for bioenergy production. Among various types of microalgae culturing systems, Open Raceway Ponds (ORP) are considered as an economic system for large-scale microalgae cultivation. In order to improve the algal growth and productivities in ORPs, it is very important to understand the effects of design parameters and operating conditions on mixing and light distribution patterns. The goal of this dissertation was to develop computational tools and experimental techniques to assess key variables that affect algal growth and productivity, and to improve microalgal cultivation in ORPs. The effects of major parameters on growth, were investigated and the optimum C. vulgaris growth condition was determined at 52 W/m2, 24&deg;C, and pH of 7.4, using Response Surface Methodology. The C. vulgaris grown in swine wastewater with 102 mg/L nitrogen and 76 mg/L phosphorus at the optimum environmental condition achieved the average growth rate of 0.16 g/L/day, compared to 0.19 g/L/day for its growth in the modified Bold's medium with 100 mg/L nitrogen and 53 mg/L phosphorus, at the same condition. Results indicated that at NC weather conditions, C. vulgaris grown in swine wastewater in a pond with 0.3 m medium depth, can reach a biomass and lipid productivity of 80 and 20 tons/hectare/year, respectively, at the harvesting cell density of 0.1 g/L. However, the algal productivity decreased significantly with the increase of harvesting cell density. A specific growth rate model of C. vulgaris was generated as a function of light intensity, temperature and pH. A Computational Fluid Dynamics (CFD) model was developed to simulate the multiphase flow in ORPs to investigate the effects of operational conditions on biomass concentration and light intensity distribution. Operating large scale ORPs at 0.2 m/s inlet velocity resulted in a significant decrease in dead zone areas in comparison with 0.1 m/s. However, further increase in velocity to 0.3 m/s did not make significant changes. CFD models were then integrated with the growth kinetic model to simulate the dynamic growth of C. vulgaris in ORPs. The predicted algal growth and productivity well agreed with those measured values. The predicted average algal productivities for the 3-week cultivation of C. vulgaris in the lab-scale ORPs were 7.34, 7.4, and 7.46 g/m2/day for medium depths of 0.20, 0.25, and 0.30 m, respectively, which well agreed with the measured values of 6.78, 7.23 and 7.39 g/ m2/day for medium depths 0.20, 0.25, and 0.30 m, respectively. Simulations were conducted to study different harvesting methods. The average algal productivity for the 3-week cultivation in the ORP with 0.2 m depth by harvesting 50% algae at the target 0.2 g/L cell density was 10.5 g/m2/day, which was 54.7% higher than 6.78 g/ m2/day for the 3-week cultivation under the same condition without harvesting. The average algal productivity decreased with the increase of harvesting cell density.</p>