There is, I think, something ethereal about i —the square root of minus one. I remember first hearing about it at school. It seemed an odd beast at that time—an intruder hovering on the edge of reality.

Usually familiarity dulls this sense of the bizarre, but in the case of i it was the reverse: over the years the sense of its surreal nature intensified. It seemed that it was impossible to write mathematics that described the real world in …

I and i

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

/pdf/synthesis-of-transportation-fuels-from-biomass-chemistry-3sckhzoqoz.pdf

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

Sustainable production of renewable energy is being hotly debated globally since it is increasingly understood that first generation biofuels, primarily produced from food crops and mostly oil seeds are limited in their ability to achieve targets for biofuel production, climate change mitigation and economic growth. These concerns have increased the interest in developing second generation biofuels produced from non-food feedstocks such as microalgae, which potentially offer greatest opportunities in the longer term. This paper reviews the current status of microalgae use for biodiesel production, including their cultivation, harvesting, and processing. The microalgae species most used for biodiesel production are presented and their main advantages described in comparison with other available biodiesel feedstocks. The various aspects associated with the design of microalgae production units are described, giving an overview of the current state of development of algae cultivation systems (photo-bioreactors and open ponds). Other potential applications and products from microalgae are also presented such as for biological sequestration of CO 2 , wastewater treatment, in human health, as food additive, and for aquaculture.

/pdf/microalgae-for-biodiesel-production-and-other-applications-a-54vmwufrsu.pdf

Microalgae for biodiesel production and other applications: A review

Biomass is an important feedstock for the renewable production of fuels, chemicals, and energy. As of 2005, over 3% of the total energy consumption in the United States was supplied by biomass, and it recently surpassed hydroelectric energy as the largest domestic source of renewable energy. Similarly, the European Union received 66.1% of its renewable energy from biomass, which thus surpassed the total combined contribution from hydropower, wind power, geothermal energy, and solar power. In addition to energy, the production of chemicals from biomass is also essential; indeed, the only renewable source of liquid transportation fuels is currently obtained from biomass.

The Catalytic Valorization of Lignin for the Production of Renewable Chemicals

Biofuels produced from various lignocellulosic materials, such as wood, agricultural, or forest residues, have the potential to be a valuable substitute for, or complement to, gasoline. Many physicochemical structural and compositional factors hinder the hydrolysis of cellulose present in biomass to sugars and other organic compounds that can later be converted to fuels. The goal of pretreatment is to make the cellulose accessible to hydrolysis for conversion to fuels. Various pretreatment techniques change the physical and chemical structure of the lignocellulosic biomass and improve hydrolysis rates. During the past few years a large number of pretreatment methods have been developed, including alkali treatment, ammonia explosion, and others. Many methods have been shown to result in high sugar yields, above 90% of the theoretical yield for lignocellulosic biomasses such as woods, grasses, corn, and so on. In this review, we discuss the various pretreatment process methods and the recent literature that...

http://ucce.ucdavis.edu/files/datastore/234-1388.pdf

Methods for Pretreatment of Lignocellulosic Biomass for Efficient Hydrolysis and Biofuel Production

/pdf/two-step-conversion-of-acetic-acid-to-bioethanol-by-ethyl-1j0yagcb69.pdf

Two-step Conversion of Acetic Acid to Bioethanol by Ethyl Esterification and Catalytic Hydrogenolysis

Levoglucosan, the major intermediate in cellulose pyrolysis, is stable up to around 500 °C in the gas phase. To study whether this stability is a characteristic property of levoglucosan, the gas-phase reactivity was compared with those of methyl α- and β-glucosides at 200–500 °C (residence time 1.2–2.0 s). The methyl glucosides decomposed even at 200 and 300 °C to form levoglucosan exclusively. This selective transglycosylation was explained with a concerted mechanism. Fragmentation of the glucosides forming C1–C3 carbonyl compounds started at 400 °C, a temperature lower than that of levoglucosan (500 °C). Thus, levoglucosan is a special carbohydrate that is stable in the gas phase, and the stability is explained by the steric hindrance of the bicyclic ring. Formation of the anhydrofuranose isomer and furans was negligible from the gas-phase pyrolysis of these compounds, suggesting that these are produced mainly from the molten-phase pyrolysis. These results show the roles of gas- and molten-phase reactions during carbohydrate pyrolysis, providing insights for upgrading biomass pyrolysis/gasification processes.

/pdf/gas-phase-pyrolysis-of-methyl-glucosides-and-levoglucosan-4abzd7mk11.pdf

Gas-phase pyrolysis of methyl glucosides and levoglucosan

Because cellulose triacetate is prepared from low-grade dissolving pulp, a considerable amount of the insoluble residue was present in the acetylation medium of the acetic acid/acetic anhydride/sulfuric acid system. To reduce the insoluble residues, a solvent, such as nitromethane, nitroethane, or dichloroacetic acid, added to the acetylation medium was found to be very effective for its reduction. By exploring the optimum conditions for acetylation with these solvents, nitromethane added and dichloroacetic acid added systems with solvent/acetic acid = 3/7 (v/v) were found to have a particularly high transmittance at λ = 670 nm in their acetylation solution with a low insoluble residue. The obtained acetates revealed good thermal properties similar to that from high-grade dissolving pulps. Therefore, a high quality cellulose triacetate can be manufactured from acetylation systems with even low-grade dissolving pulps with an appropriate solvent added. © 1996 John Wiley & Sons, Inc.

Thermal properties of cellulose triacetate as prepared from low‐grade dissolving pulp

Thermochemical processes, especially gasification and fast pyrolysis are promising ways to convert woody biomass into fuels and useful chemicals. However, low product selectivity exists as a drawback to commercialization. In order to increase product selectivity, knowledge of the pyrolysis mechanism, a fundamental process of these thermochemical processes, provides useful information. In this chapter, recent data of the pyrolysis mechanism of woody biomass is presented. Particular emphasis is made on the key reactions which govern product selectivity between low-molecular-mass (MW) products and solid carbonized products. Data on the controlled pyrolysis of cellulose into low MW products and other useful chemicals such as levoglucosenone and furfurals, based on the proposed mechanism, is also discussed.

Pyrolysis Mechanism of Woody Biomass Relating to Product Selectivity

Primary pyrolysis and secondary reactions of Japanese cedar (Cryptomeria japonica, a softwood) and Japanese beech (Fagus crenata, a hardwood) wood lignins were studied with open-top and closed-ampoule reactors in N2 at 400–600°C. Milled wood lignins (MWL) isolated from these wood samples were used along with several model aromatic compounds (guaiacol and syringol and their pyrolysis intermediates). Although the low molecular weight products from beech MWL included more syringyl-type of aromatic rings in primary pyrolysis, in the secondary reaction step, the yields of syringyl-characteristic products were quite lower than those of guaiacyl-characteristic products. Contrary to this, the beech MWL and syringol produced more coke. These results suggest that the syringyl-characteristic products are converted preferentially into coke, instead of other low MW products. The molecular mechanisms of these tar conversions are also discussed with the model compound data. Additional OCH3 group in syringyl-unit enhances the coke formation through double opportunity of the OCH3 rearrangement pathway, which includes o-quinonemethide as a key intermediate step for coke formation.

Shiro Saka

Papers

Two-step Conversion of Acetic Acid to Bioethanol by Ethyl Esterification and Catalytic Hydrogenolysis

Gas-phase pyrolysis of methyl glucosides and levoglucosan

Thermal properties of cellulose triacetate as prepared from low‐grade dissolving pulp

Pyrolysis Mechanism of Woody Biomass Relating to Product Selectivity

Pyrolysis and secondary reaction mechanisms of softwood and hardwood lignins at the molecular level