GPC analysisThe molecular weights and molecular weight dispersivity of the reaction products were determined on a Toyo Soda HLC-8020 gel Holzforschung / Vol. 55 / 2001 / No. 6 Summary By means of high performance liquid chromatography (HPLC) and gel permeation chromatography (GPC), the yields of the main reaction products and the polymeric portion formed in the reaction of guaiacylglycerol-b-guaiacyl ether (GG) under various acid-catalyzed conditions were quantified as a function of reaction time. Based on their forming sequence and reaction behavior, as well as their structural characteristics, an acid-catalyzed reaction mechanism of GG with phenol was proposed. KeywordsLiquefaction mechanism Lignin model compound Guaiacylglycerol-b-guaiacyl ether Phenolysis Acid catalysis GPC Brought to you by | HEC Bibliotheque Maryriam ET J.

Phenolation of birch wood meal was carried out in the presence of HC1 catalyst by using a reflux condenser system. The effects of reaction time, HC1 catalyst concentration, and phenol/wood ratio on the phenolation extents were determined as a function of liquefaction temperatures covering 60, 90, 120, and 150°C. It was revealed that among the reaction parameters, the reaction temperature had the greatest influence on the residual rate and the amounts of combined phenol. Although the optimum reaction temperature which gave sufficient amounts of combined phenol was found to be 120°C, the residual rates obtained at 150°C were however lower than those for 120°C. It was also found that the flow temperature of the phenolated wood increased with an increase in the amount of combined phenol. In order to improve the thermoflowability, as one of the trials, commercial novolak resin was mixed with the phenolated woods in several different ratios. By this blending with novolak resin, the flow temperatures of the phenolated woods could be reduced to a certain extent.

Guaiacylglycerol-b-guaiacyl ether (GG) was used as a lignin model compound to study the liquefaction reaction mechanism of lignin in the presence of phenol under the catalysis of several typical acids such as sulfuric, phosphoric and oxalic acids. The reaction products were isolated by silicagel column chromatography and high performance liquid chromatography (HPLC). The structures of the obtained compounds were identified by means of GC-MS, 1 H-NMR, 13 C-NMR, 1 H-1 H COSY, HMBC and HMQC. As a result, about 30 compounds were obtained as the main reaction products. It was found that their structural characteristics were significantly different from those yielded at the non-catalyzed liquefaction (Lin et al. 1997a), and independent on the acid species. The dominant products were guaiacylglycerol-a-phenyl-b-guaiacyl ethers, followed by guaiacol, triphenylethanes, diphenylmethanes, benzocyclobutanes and phenylcoumarans. The structural characteristics and yields of these main reaction products indicated that condensation between phenol and GG in its C-a and further cleavages in both the b-O-4 linkage and C b -C g bonding could be the dominant reaction pathways. KeywordsLiquefaction mechanism Lignin model compound Guaiacylglycerol-b-guaiacyl ether Phenolysis of lignin NMR GC-MS Brought to you by | HEC Bibliotheque Maryriam ET J.

Birch (Betula maximowicziana Regel) wood meal was liquefied in the presence of phenol using hydrochloric acid (HC1) as a catalyst at a temperature of 150 ~ for 2 h in an autoclave. It was found out that HC1 acid could be used as an effective catalyst for the hydroxy phenylation of wood under the experimental conditions. In this study the effect of the concentration of the acid catalyst and the phenol-to-wood ratio on the liquefaction were investigated. The results showed that the phenol-to-wood ratio and the concentration should be increased to a certain degree in order to achieve a less residual rate and sufficient amount of combined phenol. The phenolated woods had apparent flow temperatures in the range of 134.4 to 199.8 ~ being higher than that of a commercial novolak resin. Furthermore, increases in the HCI concentration during liquefaction reaction led to increase in the apparent flow temperature of the resulting phenolated woods. However, the changes in the liquid ratio did not bring about evident changes. The relationship between shear stress (x) and shear rate (~) showed that the phenolated wood resin melts were shear thinning fluids. The dependences of the apparent melt-viscosities (q) of the phenolated woods and a commercial novolak resin on the shear rates (~) have the similar tendencies, however, it was found the viscosities of the phenolated woods are about one order higher than that of commercial novolak resin.

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