Soda lignin production process

FIG U RE 10.18 Oxidation products formed on soda/AQ treatment of a (3-1 lignin model compound. (Hise, R.G., Seyler, D.K., Chen, C.-L., and Gratzl, J.S., Oxidative-Hydrolytic Processes in Alkaline Pulping. Proc Int Symp Wood Pulp Chem, Paris, France, 1, 391-398, 1987.)... 

As discussed elsewhere in this chapter, soda delignification is a well-known process widely practiced for the production of pulp and high purity lignin from non-wood fibres [85]. The cellulose fraction could be converted to alcohol by saccharification and fermentation, particularly if the fibre properties of the feedstock are not the most suitable for paper manufacture. In addition to soda delignification, ammonia explosion and lime are among other alkaline processes being considered. 

Lignin also is commercially used as a resin for paper laminates. Its low cost and availability as a by-product in pulp manufacture make it attractive. One of the most successful products is made with lignin recovered from the spent liquor of the soda pulping process. The lignin may be added to the pulp suspension in solution and precipitated directly among the fibers, or added in a preprecipitated form. 

Mansouri, N.-E. E., and Salvado, J. (2006]. Structural characterization of technical lignins for the production of adhesives Application to lignosulfonate, kraft, soda-anthraquinone, organosolv and ethanol process lignins. Ind. Crops Prod., 24,8-16. 

Main commercial sources of cellulose are wood and, to a lesser extent, cotton. To isolate the cellulose the feedstocks are boiled in boilers under pressure in the presence of caustic soda (soda process), mixture of sodium hydroxide with sodium sulfide (Kraft process) or sulfurous acid and salts thereof (sulfite process) as a result, lignin and hemicelluloses are removed, while cellulose is separated, washed, and dried (Sjostrom et al., 1993). Production volume of wood pulp in the world is huge and reaches 250-300 million tons per year. Production of cotton cellulose is smaller, 20-25 million tons per year. The main part of the cotton fibers is intended for textile industry, and only short fibers and wastes are used for the production of special papers, microciystalline cellulose and cellulose derivatives. 

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