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Two different approaches for the isolation of xylan from hemicelluloserich sources have been investigated: Alkaline extraction from roller-mill pretreated oat spelts and Nitren extraction of birch kraft pulp. For xylan recovery from oat spelts the experiments included extraction with 5% NaOH at 90 8C, followed by precipitation in methanol or 2-propanol without neutralisation in order to facilitate NaOH recovery. A subsequent peroxide bleaching yielded a product of approximately 90% ISO brightness. The work on Nitren extraction of birch kraft pulp included the optimisation of the extraction process with regard to the Nitren charge. Nitren was much more specific in xylan extraction compared to Cuen, and up to 90% of the xylan content of the birch kraft pulp could be removed. It turned out that dried pulps were superior for this process compared to never-dried pulps, since substantial cellulose proportions in never-dried pulps were also mobilised by Nitren treatment. The properties of the recovered xylans from both processes were compared with regard to molar mass and substitution. It could be demonstrated that more or less intact arabinoxylans with molar masses of 30,000 g/mol could be obtained from oat spelts. The arabinoxylans contained 8-10 mol-% arabinofuranose and 2 mol-% 4-O-methylglucuronic acid substituents. Nitren extraction of a birch kraft pulp yielded xylans of 9,400 and 11,200 g/mol. Only traces of 4-O-methyl-glucuronic-and hexenuronic acid substituents could be found.

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Dedicated to Professor Dr. Otto Vogl on the occasion of his 65th birthday Sulphation of cellulose was performed in an homogeneous aprotic system with SO, or C1S03H, resp.,via O-trimethylsilyl celluloses as reactive intermediates. Na-cellulose sulphates completely soluble in water and showing small chain degradation could be obtained at DSS 2 0.25. The DS, in the range between 0.2 and 2.5 as well as the distribution of the sulphate half-ester groups within the AGU were regulated via the DS,, at one hand, the type and amount of sulphating agent at the other. Sulphation was performed either with the isolated and redissolved trimethylsilyl cellulose in N,N-dimethylformamide or tetrahydrofurane, or, starting with an activated cellulose suspension, by achieving silylation and subsequent sulphation in one system of reaction. Obviously, the silyl group acts as a reactive group in subsequent sulphation, and the sites previously silylated are preferentially sulphated in the subsequent step of reaction, and the DS, is limited by the degree of silylation (DS,,) previously obtained. The homogeneous sulphation of trimethysilyl cellulose indicates a reactivity of silyl ether groups in the order of C-6 > C-2 >> C-3. Synihese und Subsiiiuenienverieilung von Na-Cellulosesulfaien unier Venvendung von O-Trimeihylsilylcellulose als ZwischenproduktUnter Verwendung von O-Trimethylsilylcellulose als reaktivem Zwischenprodukt wurde die homogene Sulfatierung von Cellulose mit SO, bzw. CIS0,H untersucht. Sulfatierungsgrad (DS,) und Substituentenverteilung im Anhydroglucosering lieBen sich im DS,-Bereich zwischen 0,2 und 2,5 uber den DS an Silylethergruppen einerseits, die Art und Einsatzmenge des Sulfatierungsmittels andererseits steuern, wobei wasserlosliche, wenig abgebaute Cellulosesulfate ab DS, 2 0,25 erhalten werden. Die Sulfatierung erfolgte sowohl nach Isolierung und Wiederauflosung der O-Trimethylsilylcellulose, als auch, ausgehend von einer Suspension aktivierter Cellulose, durch Silylierung und nachfolgende Sulfatierung im gleichen Reaktionssystem. Offensichtlich wirkt die Silylethergruppe als reaktive Gruppe bei der nachfolgenden Sulfatierung, indem die vorher silylierten Positionen im Anhydroglucosering bevorzugt sulfatiert werden und der erreichbare DS, durch den vorher eingestellten Silylierungsgrad begrenzt wird. Bei der Homogensulfatierung von Trimethylsilylcellulosen wurde eine Reaktivitatsabstufung der Silylgruppen in den verschiedenen Positionen entsprechend C-6 > C-2 >> C-3 beobachtet.