Behaviour of the major resin- and fatty acids of slash pine (Pinus elliottii) during organosolv pulping
Creators: name: Quinde Abad, Augusto
Publisher: name: University of British Columbia
Year: 2011

description: A high extractive-content temperate conifer wood (Pinus elliottii) was examined as a pulpwood source by organosolv pulping. Particularly, the behavior of the resin- and fatty acids during the lignin solvolysis process was studied in detail. For this purpose the resin-and fatty acids were characterized in the wood, and after pulping trials in order to reveal their fate during pulping, using catalyzed 80% aqueous alcohol (methanol) as solvent. Wood extractives were removed by both methanolic cold maceration and Soxhlet extraction techniques. The resin-and fatty acid fractions thus collected were saponified and/or methylated and characterized by gas liquid chromatography (GC) and gas chromatography-mass spectrometry (GC-MS). No significant differences were found in regard to extraction efficiencies between the two types of cold extractions. Furthermore, there was no significant difference between these two types of cold extractions in comparison with the procedure described by TAPPI standard T 204 os-76. Pulping experiments were performed at 205°C for periods of 5, 20, 40, and 60 min. Lignins, which precipitated on cooling of the black liquor (Lignin fraction I), were set aside for further extractions and chemical analyses. The molecular weight distribution of these lignins was determined by size exclusion chromatography on an HPLC and their quantity was determined either gravimetrically or volumetrically. Precipitated Lignin Fraction I, suspected of containing some adsorbed extractives and some fiber fragments, was transferred to a tared crucible. The lignin and extractives were sequentially dissolved by using tetrahydrofuran (THF), acetone and methanol. This solution was evaporated, the residue redissolved in methanol-water (80:20) and the solution liquid-liquid extracted with diethyl ether in a separatory funnel followed by methylation prior to GC and GC-MS analysis. Quantification of the resin- and fatty acids in the wood and those recovered after organosolv pulping was performed using an internal standard (methyl heptadecanoate) added prior to the extraction steps. The extractives dissolved in the black liquor were isolated by a ternary liquid-liquid extraction scheme using diethyl ether, methylated with fresh diazomethane, and the resin- and fatty acids methyl esters characterized by GC and GC-MS. The extractives present in the pulp were isolated (removed) by a Soxhlet extraction procedure with methanol and" the resin- and fatty acids fractions characterized as above. Resin- and fatty acids surviving the high-temperature pulping process, were found mainly in the black liquor. After the 60 min cook, the black liquor contained 78.1% and 71.6% of resin- and fatty acids, respectively, while the pulp retained 11.7% and 8.2%, respectively of the extractives originally present in wood. "Lignin fraction I" adsorbed 10.2% and 20.2% of the resin- and fatty acids, respectively. Contrarily, if all of the lignin is precipitated (Lignin fraction II). prior to liquid/liquid extraction of the black liquor with diethyl ether, 98% and 60.4% of the resin- and fatty acids co-precipitate with the lignin and 2.0% and 39.6%, respectively, remain dissolved in the aqueous filtrate. Industrial organosolv lignin isolated after solvent pulping of pine was thus shown to contain most (98%) of the resin acids and 39.6% of the fatty acids normally found in pines. Although not tested, it is supposed that lignins isolated by precipitation from the black liquor after organosolv pulping of other species cannot be considered as "pristine lignins" as described hitherto in the technical literature, since such lignins are heavily contaminated by the extractives of the wood species. In light of these findings all data on chemical and physical characterization of organosolv lignins and their reactivity will have to be reexamined and reassessed to remove the effect of the extractives as contaminants.