Glossary of TermsFast pyrolysis -thermal conversion in the absence of oxygen at short residence time, for woody biomass typical conditions are <2 seconds at ~500 °C Hydrothermal -processing in hot pressurized water Bio-oil -liquid product of fast pyrolysis Biocrude -liquid oil product from hydrothermal liquefaction Upgrading -multi-step hydroprocessing to convert bio-oil in liquid hydrocarbon products Hydrotreating -single-step hydroprocessing to convert biocrude into liquid hydrocarbon products Hydroprocessing -chemical reaction with hydrogen gas, typically a catalytic process operated at elevated pressure, usually to remove heteroatoms, remove unsaturation, and reduce molecular weight.Heavy hydrocarbon --hydrocarbon product distilling at temperatures higher than diesel Nth plant -commercial plant operating an established process, not a pioneer plant 14 http://www.fortum.com/en/mediaroom/Pages/fortum-invests-eur-20-million-to-build-the-worlds-first-industrialscale-integrated-bio-oil-plant.aspx 15

Catalytic wet oxidation (CWO) of aqueous effluents rich in organic compounds is a very promising technology for the treatment of liquid wastes from biomass conversion processes. CWO reactions occur through the formation of free radical species, produced in the presence of an oxidant, which act on organic contaminates in the effluent. Although the reaction is well known, there exists a lack of affordable catalysts to conduct this process at the lower temperatures and pressures in novel bioenergy processes. This study assessed the catalytic effect of nitrogen-doped chars as such an option. Phenol in aqueous solution was used as a model waste effluent. Treatment was conducted at moderate temperatures (190 to 260°C), oxygen partial pressure of 1 MPa, and reaction times of 15, 30, and 45 min in stainless steel and glass-lined tube reactors. High pressure liquid chromatography (HPLC) analyses of the products quantified phenol and by-product concentrations used in the calculation of reaction activation energy. The char catalyst was studied by X-ray photoelectron spectroscopy (XPS), transmission electron microscopy (TEM), and scanning electron microscopy (SEM) in order to gain insight into its structure and surface composition. The results indicate that nitrogen-doped char catalysts accelerate the oxidation of phenol by decreasing its reaction activation energy from 82.2 kJ/mol (non-catalyzed) to 40.4 kJ/mol (catalyzed). An analysis from first principles using density functional theory (DFT) was conducted to ascertain which N functional group has the most significant impact on free radical formation in the presence of oxygen. Among all the N functional groups studied, the dipyridinic functional groups showed the most promising characteristics to facilitate the formation of hydroxyl free radicals.

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This review explores advanced oxidative techniques of wet oxidation (WO) and catalytic wet oxidation (CWO) for treatment of primary aqueous effluents from hydrothermal liquefaction and pyrolysis (with subsequent upgrading) of biomass. Hydrothermal liquefaction and pyrolysis bio-oil upgrading processes produce an aqueous phase rich in organic carbon. However, the characterization of the compounds in such streams is limited and studies on their treatment are even more rare. Few studies have identified major compound families as phenols and smaller carboxylic acids. Often these compounds are overly toxic to existing wastewater treatment operations. Here, advanced oxidative techniques are reviewed with specific focus on how WO and CWO could affect some of these constituents such as phenols and carboxylic acids. Fundamental aspects of such reaction systems are reviewed including the most plausible oxidants (O 2 , O 3 , H 2 O 2 ), the physical and chemical stages of oxidant interactions with the contaminants themselves, and their formation under non-catalytic and catalytic process conditions. Differing types of catalysts (homogeneous, heterogeneous, active carbons) and their novel formation such as carbon nanotubes are considered. Central to the oxidation mechanism, regardless of oxidant or presence of catalyst, is the formation of oxygen-reactive species such as hydroxyl free radicals. While WO processes do generate such oxidative free radicals, it is often under stringent operating conditions. Through the addition of metal catalysts, the oxidative process is successful at removing contaminants at significantly reduced temperatures and pressure. Continuous reactors have shown the best success of removal at both the bench and pilot plant scale. However, many are plagued by oxidant transport deficiencies. To improve transport, novel reactor schemes are emerging for the next generation of oxidative continuous systems. Advanced wet oxidation processes are well suited for the treatment of thermochemical aqueous phase products such that the effluent stream is suitable for processing in wastewater treatment plants or subsequent bioenergy plant water recycle.