WA 98195 and from the U.S. Forest Products Laboratory, Madison, WI 53705 Keywords Kraft lignin Lignin model compounds Hydrocracking Phenols Tetralin Schlüsselwörter (Sachgebiete) Kraftlignin Lignin-Modellverbindungen Hydro-Verkrackung Phenole Tetralin Thermal Degradation of Kraft Lignin in Tetralin SummaryHydrocracking of kraft lignin (Indulin-AT) and of model compounds p-ethylguaiacol and dehydrodihydrodiisoeugenol (DDDI) was studied with tetralin äs hydrogen donor in the temperature ränge 375 to 400° C. It was found that aliphatic oxygen functions reacted most rapidly. The aromatic methoxyl groups underwent either methyl-oxygen or ring-oxygen cleavage forming catechol and phenol groups, respectively. The former process is more prevalent at higher temperatures. Side-chain cleavages resulted in the general lowering of molecular weight and formation of monomeric phenols. Careful analysis of the latter products suggested that these cleavages occurred mostly between the a-and ß-carbon atoms but cleavages between the aromatic ring and the -carbon also occurred. Upon prolonged hydrocracking, guaiacols and catechols disappeared while a mixture of phenol, cresols and ethyl phenols was relatively resistant towards further conversions. Thermischer Abbau von Kraftlignin in TetralinZusammenfassung Die Hydro-Verkrackung von Kraftlignin (Indulin AT) und von Modellverbindungen wie p-Äthyl-guajakol und Dehydrodihydro-Diisoeugenol (DDDI) wurde mit Tetralin als Wasserstoff-Donator im Temperaturbereich von 375 bis 400° C untersucht. Dabei wurde festgestellt, daß die Sauerstofftragenden Seitenketten sehr schnell reagieren. Die aromatischen Methoxylgruppen unterliegen entweder Methyl-Sauerstoff-oder Ring-Sauerstoff-Spaltung, wobei Catechol-bzw. PhenolGruppen gebildet werden. Der erstgenannte Prozeß läuft vorzugsweise bei höheren Temperaturen ab. Infolge der Seitenketten-Spaltung erniedrigt sich allgemein das Molekulargewicht, und es entstehen monomere Phenole. Genaue Analysen der letztgenannten Produkte weisen darauf hin, daß diese Spaltungen meistens zwischen dem a-und /3-Kohlenstoffatom vorkommen, aber auch zwischen dem aromatischen Ring und dem «-Kohlenstoff. Bei längerer Verkrackung verschwinden die Guajakol-und Catechol-Verbindungen, während eine Mischung von Phenol, Kresol und Äthylpheriolen relativ resistent gegen weitere Umwandlungen war.

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Aspen (Populus tremuloides) and black cottonwood (Populus trichocarpa) organosolv pulps produced in a wide range of solvent composition (between 30 and 70% by volume of methanol) and catalysts (H(2)SO(4) and H(3)PO(4)) such that the cooking liquor pH

SynopsisThe kinetics of alkaline degradation of cotton hydrocellulose were determined in 5% NaOH at various temperatures. An activation energy of 24 kcal./mole was found for the endwise degradation reaction, while that of termination to a stable m-saccharinic acid endunit is 32 kcal./mole. Consequently, the DP, of the degradable chain length is highly dependent on the reaction temperature, being 1000 at 65°C. and 140 a t 132°C. A t lower temperatures, the majority of degrading chains terminate to a normal reducing endgroup a t the crystallineamorphous transition region. From the data, the DP, of cellulose chain segments participating in the amorphous regions of the original cotton fibril was calculated to be 143. This result strongly supports the classical micellar fibril structure over the folded model proposed by Manley.