Comparison of different pretreatment methods for lignocellulosic materials. Part II: Influence of pretreatment on the properties of rye straw lignin.

Several processes have been suggested to convert various types of lignocellulosic biomass into lignin products and saccharides. This paper evaluates the suitability of an organosolv process, a process using soda, a hydrothermal process and a process developed in this work, called the "Aquasolve process" for inclusion into a lignocellulosic biorefinery concept. Part II of this paper investigates the influence of the different pretreatment processes on the properties of rye straw lignin and evaluates their ability to produce high recoveries of high quality lignin. Specifications for high quality lignin products are defined and the isolated lignin fractions are analysed by Klason lignin, carbohydrate and ash content, elemental analysis, thermo-gravimetric analysis, (31)P NMR, and size exclusion chromatography. The organosolv process shows the largest lignin recovery, followed by the soda and Aquasolve processes. Lignin products from the soda process, the Aquasolve process and with reservation the organosolv process show interesting properties for polymer applications.