HBS PULPING OF SOFT WOOD DELIGNIFICATION MECHANISM

摘要

A phenolic β-O-4 type lignin model compound, guaiacylglycerol-β-guaiacyl ether (GG) was treated with 70 wt% aq 1,3-butanediol solution at 160-200℃ to investigate the delignification mechanism under HBS (high-boiling solvent) pulping conditions. Recovery of GG was determined by GC. The disappearance of GG exhibited a pseudo first-order rate behavior. The pseudo first-order rate constants were as follows: k = 1.20 x 10~(-2) min~(-1) at 160℃; k = 2.31 x 10~(-2) min~(-1) at 170℃; k = 3.65 x 10~(-2) min~(-1) at 180℃; k = 10.4 x 10~(-2) min~(-1) at 200℃. The activation energy was 90.8 kJmol~(-1). The following compounds were identified from the reaction products by use of GC-MS: guaiacol (2), coniferyl alcohol (3), γ-etherified coniferyl alcohols (4) and α-etherified guaiacylglycerol-β-guaiacyl ethers (5), but acidolysis products, such as Hibbert's ketones were not detected. These results indicate that phenolic β-O-4 linkage was cleaved homoliticaly under HBS pulping conditions. The formation of higher molecular-weight compounds was confirmed by GPC. It is highly probable that polymeric products were derived from the recombination of radicals formed by homolysis of the β-aryl ether.