Abstract
HBS pulping process with saving-energy, and non-pollution was investigated using aqueous solvents (HBS) with the boiling point of about 200°C. Softwood, hardwood and annual plants were satisfactorily pulped with HBS process. RHBS obtained by removing only high molecular-weight lignin from HBS pulping spent liquors were reused several times as pulping solvents, though it contained sugars, modified sugars, low molecular-weight lignin and so forth as secondary components in addition to HBS.RHBS was more excellent as the pulping solvent than pure HBS. The delignification accelerated with RHBS was attributed to aldoses present in RHBS Delignification with HBS and RHBS were found to follow two pseudo first-order kinetics, bulk and final phases, respectively. The rate constant of the bulk phase with RHBS was about 1.5 times larger than that with HBS. We propose that the delignification is improved by aldosolysis, When heated with aqueous neutral solvents at temperatures of above 200°C, lignin is depolymerized by homolysis, which is accelerated by aldosolysis.
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