Lignin hydrolysis products

Lundquist K (1976) Low molecular weight lignin hydrolysis products Appl Polym Symp 28 1393-1407... 

The conclusion that all low molar mass lignins are hemilignins is, however, an oversimplification since it has been shown that, on heating an aqueous solution of glycolignin sulfonic acid acidified with hydrochloric acid or sulfur dioxide and bisulfite, a monomeric sulfonated hydrolysis product is formed (2). 

Under alkaline conditions isolating lignin degradation products which are essentially of a phenyl.ethyl rather than a phenylpropyl nature is structurally important and requires a lignin structure by which the 7-carbon may be removed as a result of a 0-7 carbon-carbon cleavage reaction, either by direct alkaline hydrolysis or alkali-catalyzed hydrogenolysis. 

Figure 7. HPLC analysis of the mixture of monomeric and dimeric lignin derived products obtained after acid hydrolysis of bleached CTMP.

This process can provide some advantages fi>r ethanol production, compared with acid hydrolysis process because of the extremely it >id reaction, ratha small and simple plant may be designed without use of add catalyst hi addition, lignin-derived products are not contaminated as in sulfuric acid lignin in the add hydrolysis process, so that th can be appropriate to be convated into the value-added aromatic products. Thus, the ovaall process would lead to the effidait utilization of the whole lignocellulosics. 

Ishihara et al (1991) designed a different method. The use of a suction filter unit and a reservoir tank that is constantly stirred enables the removal of the lignin-rich build-up. The hydrolysis products can then be removed by an ultrafiltration membrane unit. According to Henley et al (1980), the efficiency of the hydrolysis process can be improved by the addition of a ultrafiltration membrane stirred cell or a hollow-fibre cartridge into the CSTR-UF and CSTR-HC systems. 

Sakakibara A, Nakayama N 1962 Hydrolysis of lignin with dioxane and water. II. Identification of hydrolysis products. Mokuzai Gakkaishi 8 153-162... 

Acidolysis is close related to hydrolysis that is used for bio-ethanol production. The decomposition mechanisms and hydrolysis products of lignocellulosics under various conditions in hot-compressed water were discussed in order to establish preferable conditions among hydrolysis behavior in hot-compressed water, acid, alkaline, and enzymatic hydrolysis [69]. Hydrolysis lignin obtained as a byproduct of bio-ethanol industries can be used as the raw material for the production of lignin-based new environmentally compatible polymers (see Chaps. 5 and 6). 

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