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

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

Renewable Resources Robert-Jan van Putten,†,‡ Jan C. van der Waal,† Ed de Jong,*,† Carolus B. Rasrendra,‡,⊥ Hero J. Heeres,*,‡ and Johannes G. de Vries* †Avantium Chemicals, Zekeringstraat 29, 1014 BV Amsterdam, the Netherlands ‡Department of Chemical Engineering, University of Groningen, Nijenborgh 4, 9747 AG Groningen, the Netherlands Stratingh Institute for Chemistry, University of Groningen, Nijenborgh 4, 9747 AG Groningen, the Netherlands DSM Innovative Synthesis BV, P.O. Box 18, 6160 MD Geleen, the Netherlands Department of Chemical Engineering, Institut Teknologi Bandung, Ganesha 10, Bandung 40132, Indonesia

Hydroxymethylfurfural, A Versatile Platform Chemical Made from Renewable Resources

This critical review provides a survey illustrated by recent references of different strategies to achieve a sustainable conversion of biomass to bioproducts. Because of the huge number of chemical products that can be potentially manufactured, a selection of starting materials and targeted chemicals has been done. Also, thermochemical conversion processes such as biomass pyrolysis or gasification as well as the synthesis of biofuels were not considered. The synthesis of chemicals by conversion of platform molecules obtained by depolymerisation and fermentation of biopolymers is presently the most widely envisioned approach. Successful catalytic conversion of these building blocks into intermediates, specialties and fine chemicals will be examined. However, the platform molecule value chain is in competition with well-optimised, cost-effective synthesis routes from fossil resources to produce chemicals that have already a market. The literature covering alternative value chains whereby biopolymers are converted in one or few steps to functional materials will be analysed. This approach which does not require the use of isolated, pure chemicals is well adapted to produce high tonnage products, such as paper additives, paints, resins, foams, surfactants, lubricants, and plasticisers. Another objective of the review was to examine critically the green character of conversion processes because using renewables as raw materials does not exempt from abiding by green chemistry principles (368 references).

Conversion of biomass to selected chemical products

Various novel techniques including ultrasound-assisted extraction, microwave-assisted extraction, supercritical fluid extraction, and accelerated solvent extraction have been developed for the extraction of nutraceuticals from plants in order to shorten the extraction time, decrease the solvent consumption, increase the extraction yield, and enhance the quality of extracts. A critical review was conducted to introduce and compare the conventional Soxhlet extraction and the new alternative methods used for the extraction of nutraceuticals from plants. The practical issues of each extraction method were discussed. Potential uses of those methods for the extraction of nutraceuticals from plant materials was finally summarized.

Recent advances in extraction of nutraceuticals from plants

Extraction of protein and amino acids from deoiled rice bran by subcritical water hydrolysis

Lignin as a part of wood biomass has been proposed to be an alternative source of chemical compounds for industrial applications. The degradation of lignin was studied in near and supercritical water at temperatures 623 and 673 K using a batch type reactor. The effects of temperature and reaction time were combined into a single severity parameter that was used to monitor the degradation of lignin to liquid fraction. With an increase in the reaction time at the same conditions, higher molecular weight fractions decreased and the amount of lower molecular weight fractions increased. The chemical species in liquid products and solid residues (char) were analyzed using high performance liquid chromatography with a Jasco MD-2010 Plus and Fourier transform infrared spectrophotometer, respectively. The main products in methanol soluble fraction were catechol (28.37 wt%), phenol (7.53 wt%), m,p-cresol (7.87 wt%) and o-cresol (3.80 wt%). Based on the experimental results, a reaction mechanism for the degradation of lignin was proposed. Next, optimum-operating conditions for high yields of valuable chemicals could be explored.

Recovery of phenolic compounds through the decomposition of lignin in near and supercritical water

The development of chemical recycling of waste plastics by decomposition reactions in sub- and supercritical fluids is reviewed. Decomposition reactions proceed rapidly and selectively using supercritical fluids compared to conventional processes. Condensation polymerization plastics such as polyethylene terephthalate (PET), nylon, and polyurethane, are relatively easily depolymerized to their monomers in supercritical water or alcohols. The monomer components are recovered in high yield. Addition polymerization plastics such as phenol resin, epoxy resin, and polyethylene, are also decomposed to monomer components with or without catalysts. Pilot scale or commercial scale plants have been developed and are operating with sub- and supercritical fluids.

Chemical recycling of plastics using sub- and supercritical fluids

Green materials synthesis with supercritical water

The extraction of essential oil from peppermint leaves with supercritical carbon dioxide was studied in a semibatch-flow extraction apparatus. The extraction rates of the major components, l-menthol and menthone, were measured at various conditions: 313–353 K, 8.83–19.6 MPa. The exit concentration of l-menthol extracted from peppermint leaves was much smaller than the solubility of l-menthol. The extraction curves at various flow rates coincide in the plot of yield versus quantity of CO2 consumed. A mathematical model based on the local adsorption equilibrium of essential oil on lipid in leaves and mass transfer well described the extraction results. The adsorption equilibrium constant determined by filling the theoretical extraction curve to the experimental data increased with temperature and decreased with pressure.

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Papers

Extraction of protein and amino acids from deoiled rice bran by subcritical water hydrolysis

Recovery of phenolic compounds through the decomposition of lignin in near and supercritical water

Chemical recycling of plastics using sub- and supercritical fluids

Green materials synthesis with supercritical water

Extraction of Peppermint Oil by Supercritical Carbon Dioxide