Lignin dioxane

Table III. Mn of Narrow Fractions of Spruce Dioxane Lignin...

Dioxane Lignin. Spruce wood meal was extracted with a boiling solution composed of 1000 ml dioxane and 10 ml HC1 (sp. gr. = 1.19) (18). The resulting lignin was then Soxhlet-extracted with diethyl ether and fractionated by SEC (4,18) to obtain narrow fractions. 

The idea of lignin s reacting chemically to become solubilized has some support in our own unpublished work 4) in which periodate lignins from various sources were extracted with acidic aqueous dioxane, whereupon they dissolved to a considerable extent, and the soluble portion, after precipitation, showed all the characteristics (analytical and spectroscopic) of the corresponding dioxane lignins, including enhanced absorption at 1710 cm.-1... 

Photolysis of Lignin Part 1. Deaerated Solutions of Dioxane-Lignin", Polymer Photochem., 1986, 7, 401. 

Figure 4.8.8 shows the TG curves of softwood dioxane lignin at various heating rates, k (Hirose and Hatakeyama 1986). Applying Eq. (7) to the TG curves, the linear relationship shown in Fig. 4.8.9 is obtained. The activation energy calculated from the data is 136kJ/mol. 

Fig. 4.8.12. Diagram showing the effect of degree of acetylation and water content on the glass transition temperature, Tx, of dioxane lignin. (Hatakeyama and Hatakeyama 1983)...

Fig. 4.8.14. Heat capacity (Cp) curves of quenched (cooled rapidly) and annealed (heat-treated) dioxane lignin A quenched from 423 K to 310 K, B annealed at 395 K for — 60 min, — lOOmin, - 940min, 1300min (Hatakeyama et al 1982)...

The Cp values for the glassy and transition regions reflect the structural change in the amorphous state of lignin and are dependent on the temperature of measurement A typical Cp value for dioxane lignin at 350 K is 1 342 J/(g K) Figure 4 8 14 shows Cp curves of dioxane lignin as a function of temperature under various treatment conditions (Hatakeyama et al 1982) The appearance... 

Rezanowich A, Yean WQ, Goring DAI (1963) The molecular properties of milled wood and dioxane lignins sedimentation, diffusion, viscosity, refractive index increment and ultraviolet absorption Sven Papperstidn 66 141-149 Sarkanen KV, Chang H-M, Allan GG (1967) Species variations in lignin (2) Conifer lignins (3) Hardwood lignins Tappi 50 583-590... 

Funaoka M, Abe I (1978a) The reaction of lignin under the presence of phenol and boron trifluoride I On the formation of catechol from MWL, dioxane lignin and kraft lignin Mokuzai Gakkaishi 24 256-261... 

Chum HL, Ratcliff M, Schroeder HA, Sopher DW (1984)Electrochemistry of biomass-derived materials. I. Characterization, fractionation, and reductive electrolysis of ethanol-extracted explosively depressurized aspen lignin. J Wood Chem Technol 4 505-532 Crozier TE, Johnson DC, Thompson NS (1979) Changes in a southern pine dioxane lignin on oxidation with oxygen in sodium carbonate media. Tappi 62 107-111 Ekman K, Enkvist T (1955) Some determinations of weak and strong acids in various lignin preparations and pulps. Pap Puu 37 369-382... 

Table 8.2.4. Weight-average molecular weights of fractions of spruce dioxane lignin (Pla et al. 1977)...

Table 8.3.2. Number-average molecular weights of spruce dioxane lignin fractionated by preparative size exclusion chromatography (Pla and Robert 1974a, Froment and Robert 1977)...

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