Organosolv process

The chemical and technological aspects of lignin modification and utilization are discussed. Competition with petrochemicals does not, for a number of reasons, permit the commercial utilization of non-oil based products made from lignin. However, pressure from governments and the public for a cleaner environment and new pulping processes (organosolv processes) may inevitably result in full scale industrial use of lignin other than fuel within the not too distant future. 

The principles of the MD-Organosolv process, developed in Germany, are illustrated in Fig. 28.13. The process consists of first impregnating softwood chips with 50 percent aqueous methanol before they enter the first-... 

In almost all organosolv processes, chemical catalysis plays a necessary role, as solvents alone do not function effectively for the separation of biomass.403 The most commonly employed processes, based on the treatment of biomass with aqueous alcohols at elevated temperatures, are autocatalyzed. Acetic acid is generated during the separation process through hydrolysis of acetate groups present on the hemicellulose polymer.397,404 406 Alternatively, acid can be added to the separation medium prior to the process. Adding acid catalyst normally allows lower separation temperatures and milder conditions. Chemical catalysis has proven to be of particular importance for the... 

Formacell An Organosolv process using formic acid. 

A variety of methods exits to extract native (nonmodified) lignin totally or partially from lig-nocellulose biomass. These methods use organic solvents like methanol or ethanol (Organosolv process [43]) or even pure water (steam explosion process, Aquasolv process [41,44-47]), but... 

Because of the recalcitrance of lignin, processing of Ugnin-rich biomass by solvents requires the use of aggressive solvents (Abels et al., 2013). Two commercial treatment jM ocesses of wooden biomass with strong solvents have been developed (1) the Kraft process and (2) the Organosolv process (Figure 11.3). 

The solid cellulose fraction from the organosolv process and the solid cellulose-lignin complex from the aquathermolysis can be hydrolyzed to glucose by using enzymes or acid catalysts. The glucose is subsequendy fermented into a broth from which the bioethanol is recovered by distillation. This is a standard procedure in new second-generation lignoceUulosic biomass-based biorefineries for bioethanol. 

Several methods for the fractionation of hemicellulose from lignocellulose have been described in the literature. These include physical methods such as steam treatment (7-73), and chemical methods such as for exanq>le organosolv processes (d, 14, 75). In addition, microwave irradiation of lignocellulose in the presence of water has been investigated for the purpose of enzymatic saccharification and ethanol production (7d-7S) and within our project for the extraction of hemicellulose (7). 

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