Fractionation of organosolv lignin

Organosolv lignin-PEG was synthesized using a procedure similar to that used for the lignin model compounds. A 20% dioxane solution of 0.4 M NaOH was prepared. To 6 mL of this solution, 0.6 g of the chloroform soluble fraction of organosolv lignin... 

A problem that still has to be solved is the deficiency of water resistance. The sulfonate groups are so polar that the polymerizate is still water-soluble. As was mentioned before, water-soluble fractions of organosolv lignins became insoluble in water after enzymic polymerization (11) Therefore, we hoped that an addition of phenol-rich organosolv lignin would improve the water resistance However, as can be seen in the last line of Table I, this is not the case. 

Organosolv lignin was isolated from black cottonwood (P. trichocarpa) which had been pulped using a methanol/water (70/30) solvent system with NaHSC>4 as a catalyst (28). The chloroform-soluble fraction of this lignin was utilized in this study. lH-nmr broad peaks were observed at 3.7 and 6.7 ppm C-nmr 55.9 (-OCH3), and other typical lignin peaks were observed from 103 ppm to 152 ppm. 

Figure 5. Composite MWD diagram showing the calculated distributions of four of the five master fractions obtained from preparative chromatography of organosolv aspen lignin (fraction number 4 to 1 from left to right). The Mw values for the master fractions from left to right are 1,110, 1,310, 2,420, and 8,050, respectively. The insert shows the elution profile of organosolv aspen lignin from the YMC preparative /z-Styragel column (5 x 200 cm). The 30 fractions collected were pooled into the five master fractions shown.

Table 8.2.2. Weight-average molecular weights of acidic organosolv lignin fractions from black cottonwood determined with a LALLS photometer. (Pla et al. 1986)...

Tables 8.2.2 and 8.2.3 give typical results for two series of polydisperse lignin fractions obtained from acidic organosolv delignification of black cottonwood (Pla et al. 1986) and from alkaline delignification of western hemlock (Dolk et al. 1986). In both cases, LALLS allows accurate determination of low molecular weight values. The nearly identical dn/dc values for a given series of lignin fractions indicate the good reproducibility and accuracy of the technique. However, the second virtal coefficients, A2, vary considerably depending upon the fraction measured.

X Pan, D Lachenal, C Lapierre, B Monties. Structure and reactivity of spruce mechanical pulp lignins Part II. Organosolv fractionation of lignins in a flow-through reactor. J Wood Chem Technol 12 279-298, 1992. 

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