Preparation and Characterization of Chemical Pulps from Wood and Reed Canary Grass

Abstract: This thesis presents laboratory results from ethanol pulping of reed canary grass for the production of paper pulp. The focus was on the influence of cooking pa-rameters on the delignification. The strength of the grass pulps was found to be low and the use of such pulps will therefore be limited to a few products.



The use of reed canary grass pulp for the preparation of microcrystalline cellulose by acid hydrolysis was also studied.



The degradation of cellulose in different pulps during acid hydrolysis was investi-gated mainly through the levelling-off degree of polymerization (LODP) and the weight loss. The effect of hydrolysis conditions on the LODP and on the weight loss was studied, and a method for determining LODP was established.



Pulps from birch, eucalyptus and reed canary grass with different hemicellulose contents were prepared. The hemicellulose content was reduced either by a prehy-drolysis step before kraft pulping or by alkali treatment of the bleached pulps. The crystallite size, as determined by LODP, of the pulps was strongly affected by the xylan content in the pulps after acid hydrolysis. A mechanism for the degradation of cellulose in pulps with different hemicellulose content was suggested.



The size of the fiber fragments after acid hydrolysis was also influenced by the xy-lan content. At a given xylan content the fiber fragments from reed canary grass were smaller than those from the hardwoods.