1.0. Introduction 4044 2.0. Biomass Chemistry and Growth Rates 4047 2.1. Lignocellulose and Starch-Based Plants 4047 2.2. Triglyceride-Producing Plants 4049 2.3. Algae 4050 2.4. Terpenes and Rubber-Producing Plants 4052 3.0. Biomass Gasification 4052 3.1. Gasification Chemistry 4052 3.2. Gasification Reactors 4054 3.3. Supercritical Gasification 4054 3.4. Solar Gasification 4055 3.5. Gas Conditioning 4055 4.0. Syn-Gas Utilization 4056 4.1. Hydrogen Production by Water−Gas Shift Reaction 4056

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Synthesis of transportation fuels from biomass: chemistry, catalysts, and engineering.

https://courses.washington.edu/cfr523/documents/Alonso2010CatalyticConversion.pdf

Catalytic conversion of biomass to biofuels

Production of liquid biofuels from renewable resources

Biodiesel is a renewable transportation fuel consisting of fatty acid methyl esters (FAME), generally produced by transesterification of vegetable oils and animal fats. In this review, the fatty acid (FA) profiles of 12 common biodiesel feedstocks were summarized. Considerable compositional variability exists across the range of feedstocks. For example, coconut, palm and tallow contain high amounts of saturated FA; while corn, rapeseed, safflower, soy, and sunflower are dominated by unsaturated FA. Much less information is available regarding the FA profiles of algal lipids that could serve as biodiesel feedstocks. However, some algal species contain considerably higher levels of poly-unsaturated FA than is typically found in vegetable oils. Differences in chemical and physical properties among biodiesel fuels can be explained largely by the fuels’ FA profiles. Two features that are especially influential are the size distribution and the degree of unsaturation within the FA structures. For the 12 biodiesel types reviewed here, it was shown that several fuel properties – including viscosity, specific gravity, cetane number, iodine value, and low temperature performance metrics – are highly correlated with the average unsaturation of the FAME profiles. Due to opposing effects of certain FAME structural features, it is not possible to define a single composition that is optimum with respect to all important fuel properties. However, to ensure satisfactory in-use performance with respect to low temperature operability and oxidative stability, biodiesel should contain relatively low concentrations of both long-chain saturated FAME and poly-unsaturated FAME.

Review of biodiesel composition, properties, and specifications

Recent Advances in Polyoxometalate-Catalyzed Reactions

Biodiesel is synthesized via the transesterification of lipid feedstocks with low molecular weight alcohols. Currently, alkaline bases are used to catalyze the reaction. These catalysts require anhydrous conditions and feedstocks with low levels of free fatty acids (FFAs). Inexpensive feedstocks containing high levels of FFAs cannot be directly used with the base catalysts currently employed. Strong liquid acid catalysts are less sensitive to FFAs and can simultaneously conduct esterification and transesterification. However, they are slower and necessitate higher reaction temperatures. Nonetheless, acid-catalyzed processes could produce biodiesel from low-cost feedstocks, lowering production costs. Better yet, if solid acid catalysts could replace liquid acids, the corrosion and environmental problems associated with them could be avoided and product purification protocols reduced, significantly simplifying biodiesel production and reducing cost. This article reviews some of the research related to biodi...

Synthesis of Biodiesel via Acid Catalysis

Biodiesel is a particularly attractive renewable fuel as it can be used in existing engines, is environmentally friendly, and is readily synthesized from animal fats and vegetable oils. Heterogeneous catalysts offer exciting possibilities for improving the economics of biodiesel synthesis; however, few published investigations have addressed the use of such catalysts to date. The purpose of this research was to investigate the kinetics and selectivities of different solid catalysts for the transesterification of triacetin (a model compound for larger triglycerides as found in vegetable oils and fats) with methanol. Reaction was carried out at 60 °C in a batch reactor with a variety of solid and liquid, acid and base catalysts. The homogeneous phase (i.e., liquid) catalysts (NaOH and H2SO4) were studied for comparison. Amberlyst-15, Nafion NR50, sulfated zirconia, and ETS-10 (Na, K) showed reasonable activities, suggesting that they could be suitable alternatives to liquid catalysts. While on a wt.% basis (of reaction mixture) the homogeneous phase catalysts gave higher rates of reaction, on a rate-per-site basis the solid acids were similar to H2SO4. Sulfated zirconia and tungstated zirconia had comparable turnover frequencies as H2SO4. The deactivation characteristics of some of these catalysts were also studied.

Transesterification of triacetin with methanol on solid acid and base catalysts

Activation and deactivation characteristics of sulfonated carbon catalysts

In this paper, modified zirconias (WZ, SZ, and TiZ) have been extensively compared under the same reaction conditions as catalysts for both the transesterification of triglycerides (TGs) and the esterification of carboxylic acids (free fatty acids, FFAs) with ethanol. In addition, for the first time, the catalyzed rate of hydrolysis/esterification + transesterification of triglycerides has been quantified and compared to that of the rate of simultaneous esterification of FFAs present in the same reaction mixture. Tricaprylin and caprylic acid were used as representative compounds for the comparison of the catalyst for transesterification and esterification since they give reaction rates related to those of larger TGs and FFAs typically present in vegetable oils and animal fats. For the measurement of the kinetics for the simultaneous reaction of a TG-FFA mixture, the reaction of tricaprylin and oleic acid with ethanol was studied using the most promising of the Zr-based catalysts, WZ. Reaction was carried out in a well-mixed batch reactor under mild conditions (75–120 °C). TiZ, while more active than WZ for transesterification, had by far the lowest activity for esterification. SZ, while the most active catalyst (on a weight basis) for both transesterification and esterification reactions, exhibited significant sulfur loss, which greatly reduced its long term activity. As expected, esterification occurred at a much faster rate than transesterification. However, under simultaneous reaction conditions, by virtue of the water being produced in esterification and hydrolysis of the TG taking place, the conversion of the triglycerides to ester products was greatly increased. The resulting caprylic acid from hydrolysis did not accumulate in the reaction mixture due to its rapid esterification to ethyl caprylate. The activity results for WZ indicate how biodiesel can be efficiently produced from free-fatty-acid-containing feedstocks using a solid-acid-catalyzed pre-esterification step, and how a significant fraction of the triglycerides can also be converted at the same time assisted by initial hydrolysis with byproduct water from esterification.

Dora E. López

Papers

Synthesis of Biodiesel via Acid Catalysis

Transesterification of triacetin with methanol on solid acid and base catalysts

Activation and deactivation characteristics of sulfonated carbon catalysts

Esterification and transesterification using modified-zirconia catalysts

Esterification and transesterification on tungstated zirconia: effect of calcination temperature