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Bioderived lipids offer a potentially promising intermediate to displace petroleum-derived diesel. One of the key challenges for the production of lipids via microbial cell mass is that these products are stored intracellularly and must be extracted and recovered efficiently and economically. Thus, improved methods of cell lysis and lipid extraction are needed. In this study, we examine lipid extraction from wet oleaginous yeast in combination with seven different cell lysis approaches encompassing both physical and chemical techniques (high-pressure homogenization, microwave and conventional thermal treatments, bead beating, acid, base, and enzymatic treatments) to facilitate lipid extraction from a model oleaginous yeast strain, Lipomyces starkeyi. Of the seven techniques investigated, acid treatment led to the highest lipid recovery yields. Further exploration of acid treatment and integration with an economic model revealed that treatment at 170 °C for 60 min at 1 wt % H2SO4 and 8 wt % yeast solids re...

Algal lipids represent a promising feedstock for production of renewable diesel, but there is little information available regarding the integration of pretreatment, extraction, and catalytic upgrading steps. In this work, we examined oil bleaching by two methods and the effects of bleaching on oil deoxygenation over Pd/C and hydroisomerization over Pt/SAPO-11 catalysts. The raw oil was completely deoxygenated and 90% denitrogenated after dilution to 25 wt % in hexanes. The bleaching operations (using either a polar adsorbent or concentrated H3PO4) removed 85–90% of the nitrogen and led to 95–99% nitrogen removal after deoxygenation. Oil processability was also improved by bleaching. The bulk chemistry of the deoxygenation and isomerization was not strongly affected by bleaching, as post-isomerization products with cloud points less than −10 °C and boiling ranges within or close to specification for No. 2 diesel fuel were obtained through 10 h time on stream with or without bleaching.

The main paths by which zeolites carry out the dehydration of fructose to HMF and the rehydration of HMF to levulinic acid in aqueous solutions are elucidated using an H-BEA zeolite with SiO2/Al2O3 = 18 (H-BEA-18) as a representative solid acid catalyst. Specifically, the relative role of homogeneous chemistry (both solvent- and zeolite-induced), the effect of external surface acid sites, and the effect of adsorption of products and reactants on the catalyst for these reactions is delineated. We found that H-BEA-18 increases the conversion of fructose and HMF in part by catalyzing fructose isomerization to glucose and HMF rehydration to formic and levulinic acids, respectively. The glucose-to-fructose isomerization is caused by octahedral aluminum atoms that act as Lewis acid sites as shown by 1H and 13C NMR. These Lewis sites are formed during calcination and are stable under reaction conditions. They also catalyze reactions to unknown products from both fructose and HMF. The acids produced from HMF rehy...

The development of biofuels produced from biomass-derived pyrolysis oils (bio-oil) requires a deeper understanding of the bio-oil vaporization required for catalytic hydrodeoxygenation, reforming and combustion processes. Through the use of high-speed photography, bio-oil droplets on a 500 °C alumina disk in nitrogen gas were observed to undergo violent microexplosions capable of rapidly dispersing the fuel. High speed photography of the entire droplet lifetime was used to determine explosion times, frequency and evaporation rates of the bio-oil samples that have been preprocessed by filtering or addition of methanol. Filtration of the oil prior to evaporation significantly reduced the fraction of droplets that explode from 50% to below 5%. Addition of methanol to bio-oil led to uniform vaporization while also increasing the fraction of droplets that exploded. Experiments support the necessity of dissolvable solids for the formation of a volatile core and heavy shell which ruptures and rapidly expands to ...

This work aims to clarify preferred chemical routes in an autothermal system by investigating individually two-carbon molecules containing the functional groups found in bio-oil. In part 2, conversion and selectivity to major compounds are compared in the presence and absence of α-Al2O3 support and oxygen. Oxygen significantly increases conversion, even at feed rates insufficient to sustain autothermal operation. In general, below 450 °C, homogeneous reactions in the absence of oxygen are insignificant for all molecules; in the presence of oxygen, the reaction onset temperature is somewhat lower. The role of the α-Al2O3 support appears to be a combination of improved heat transfer and the radical quenching ability of the foam structure. Acid catalysis appears minor compared to these other functions. With no O2 co-feed, acids, ethers, and aldehydes appear to be more stable than alcohols and esters. With O2 co-feed, acids and ethers may be less reactive in the gas phase than the other functionalities studie...

Autothermal partial oxidation is a promising technique to upgrade bio-oil into syngas and commodity chemicals. This work aims to clarify preferred chemical routes in an autothermal system by investigating individually two-carbon molecules containing the functional groups found in bio-oil. Acids, alcohols, aldehydes, esters, ethers, and polyols were reacted over Pt– and Rh–Al2O3 catalysts. Also, to investigate thermal effects independent of O2-induced reactions, these molecules were passed over the same catalysts under similar conditions but in the absence of O2. Oxygen and adsorption geometry (the latter deduced from surface science literature) appear to play a key role in reaction initiation (manifested via overall conversion) and in the subsequent reaction of intermediate compounds. The catalyst identity also played a significant role in the observed product spectrum, and conversion was higher over the Rh catalyst. Polyols, ethers, and acids were the least reactive, while esters were the most reactive. ...

We performed a long-term study of the autothermal reforming of glycerol. Liquid glycerol and water were introduced into a quartz reactor at room temperature and mixed with air in a nebulizer. The aerosol reacted to form H2, H2O, CO, and CO2 over a bed of spherical Rh−Ce/CeO2/Al2O3 particles, with minor production of C2+ species. Catalyst deactivation was exhibited by a decrease in the production of H2 and CO2 and increases in CO and temperature over 450 h. The product changes suggest reduction in the water−gas shift reaction, which is typically promoted by Ce. SEM analysis indicated sintering of the catalyst due to high reaction temperatures, and EDS showed inorganic deposits on the walls of the quartz reactor and on the catalyst spheres. Etching of the quartz reactor shell was also observed.

Structure-directing agents based on iridium(III) complexes provide a hydrothermally robust alternative to the corresponding cobalt compounds. The slight size difference between Co(III) and Ir(III) does not dramatically influence the nature of the AlPO products that are obtained from hydrothermal synthesis using complexes based upon the ligands 1,2-diaminoethane and trans-1,2-diaminocyclohexane (chxn). However, the very slow ligand exchange kinetics of the Ir(III) complexes facilitate the use of increased hydrothermal synthesis temperatures when compared to the corresponding Co(III) complexes. For the two systems that they have examined, the use of Ir(III) allows the synthesis temperatures to be increased by {approximately} 40 C over the maximum that is viable for the corresponding cobalt complexes. This increase allowed us to prepare AlPO single crystals using Ir({+-}chxn){sub 3}{sup 3+}, whereas they authors could only obtain powders using the corresponding cobalt complexes. The use of iridium in place of cobalt increases the range of ligands that can be considered in constructing chelate complexes for use as structure-directing agents and may facilitate the preparation of different AlPO products from those found using cobalt complexes, as higher hydrothermal synthesis temperatures can be employed.