Biomass routes

There are many different routes to organic chemicals from biomass because of its high polysaccharide content and reactivity. The practical value of the conversion processes selected for commercial use with biomass will depend strongly on the availabiUty and price of the same chemicals produced from petroleum and natural gas. 

Biomass has been pointed out as the most important source for a broad variety of advanced polymeric materials, which can be obtained by different routes employing ... 

Most important, reliable and no-regrettable measures are two move to renewable energies and energy saving/conservation. The concept of renewable energy is shown in Fig. 2. The trials of developments of new route to solar energies, for example production of polycrystalline silicon is important [9, 10]. The conversion of waste oil to fiiel has also been investigated [11]. The study on coal conversion is also developed to the biomass conversion study. 

Figure S The iimula(ed distribution of (u) soluble carbon and (b) microbial biomass in the rhizosphere of maize over a period of 10 days. The Jf axis represents distance (cm) from die rout surface and the Y axis represents time (h). A unifonn exudation rate (S3) is compared to the situation where the. siime amount of exudate is released in the first 24 h (S4). Note that the Z axes have different scales although both represent pg C cm (From Ref. 48.)...

Corma, A., Iborra, S. and Velty, A. (2007) Chemical routes for the transformation of biomass into chemicals. Chemical Reviews, 107 (6), 2411-2502. 

Heterogeneous catalysts, particularly zeolites, have been found suitable for performing transformations of biomass carbohydrates for the production of fine and specialty chemicals.123 From these catalytic routes, the hydrolysis of abundant biomass saccharides, such as cellulose or sucrose, is of particular interest. The latter disaccharide constitutes one of the main renewable raw materials employed for the production of biobased products, notably food additives and pharmaceuticals.124 Hydrolysis of sucrose leads to a 1 1 mixture of glucose and fructose, termed invert sugar and, depending on the reaction conditions, the subsequent formation of 5-hydroxymethylfurfural (HMF) as a by-product resulting from dehydration of fructose. HMF is a versatile intermediate used in industry, and can be derivatized to yield a number of polymerizable furanoid monomers. In particular, HMF has been used in the manufacture of special phenolic resins.125... 

Large-scale gasification reactor technology based on EF gasification from (a) General Electric (GE Texaco process) and (b) Conoco-Phillips (E-Gas). (Adapted from Meier, D. Faix, O. Fast pyrolysis A route for energy and chemicals from wood—fluidized vs. ablative pyrolysis. In Wood and Biomass Utilization for the Carbon Uptake, Seoul National University, Seoul, 2005, pp. 55-68.)... 

Biomass conversion technologies can be divided into direct production technology routes and technologies aimed at the conversion of storable intermediates. Direct routes have the advantage of simplicity. Indirect routes have additional production steps, but have an advantage in that there can be distributed production of the intermediates, minimizing the transportation costs of the biomass. Intermediates can be... 

Direct production of hydrogen from gasification is the simplest route. Gasification is a two-step process in which the solid feedstock is thermochemically converted to a low- or medium-energy-content gas. Natural gas contains 35 MJ/Nm3. Air-blown biomass gasification results in approximately 5 MJ/m3 oxygen-blown in 15 MJ/m3. 

Gasification coupled with water-gas shift is the most widely practiced process route for biomass to hydrogen. Thermal, steam, and partial oxidation gasification technologies are under development. Feedstocks include both dedicated crops and agricultural and forest product residues of hardwood, softwood, and herbaceous species. 

Figure 3.2 Summary of hydrogen production routes from biomass. (Source Milne, T.A. et al. Hydrogen from Biomass State of the Art and Research Challenges, NREL, IEA/H2/TR-02/001).

Figure 3.3 Direct gasification routes to hydrogen conversion from biomass.

Figure 3.3 provides the reader with a summary of the leading direct gasification routes of biomass to hydrogen conversion. 

Second-generation biofuel technologies make use of a much wider range of biomass feedstock (e.g., forest residues, biomass waste, wood, woodchips, grasses and short rotation crops, etc.) for the production of ethanol biofuels based on the fermentation of lignocellulosic material, while other routes include thermo-chemical processes such as biomass gasification followed by a transformation from gas to liquid (e.g., synthesis) to obtain synthetic fuels similar to diesel. The conversion processes for these routes have been available for decades, but none of them have yet reached a high scale commercial level. 

Numerous chemical intermediates are oxygen rich. Methanol, acetic acid and ethylene glycol show a O/C atomic ratio of 1, as does biomass. Other major chemicals intermediates show a lower O/C ratio, typically between 1/3 and 2/3. This holds for instance for propene and butene glycols, ethanol, (meth)acrylic acids, adipic acid and many others. The presence of some oxygen atoms is required to confer the desired physical and chemicals properties to the product. Selective and partial deoxygenation of biomass may represent an attractive and competitive route compared with the selective and partial oxidation of hydrocarbon feedstock. 

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