Gabriele Schild

Analysis of degradation products in rayon spinning baths

Abstract An analytical method for the determination and quantification of the main organic degradation products of viscose spinning baths was outlined herein and successfully applied. Samples were ethoximated and silylated for GC-MS analysis. The main challenge in the analysis was the quantification of the degradation products because standard compounds are often not commercially available. Analyte recovery was optimized with regard to pH and lyophilization conditions. Given that the spinning bath analytes showed a very broad range of volatility, internal standardization by the degradation product of uniformly 13C-labeled glucose in alkaline media was used. This approach allowed for the first time for the accounting of a major part of the organic components in the viscose spinning baths. On average, 57% of total organic carbon was characterized by quantifying 21 individual substances. The methodology opens new perspectives of keeping track of the formation and origin of organic degradation products. It is a prerequisite to all further efforts to avoid contamination of the spinning bath and achieve a higher product quality and a better closure of process cycles. Furthermore, it can be easily applied to other highly complex industrial process streams involving polysaccharide degradation products as they are emerging, for instance, in biorefineries.

A precise study on effects that trigger alkaline hemicellulose extraction efficiency.

The conversion of paper-grade pulps into dissolving pulps requires efficient strategies and process steps to remove low-molecular noncellulosic macromolecules generally known as hemicelluloses. Current strategies include alkaline extractions and enzymatic treatments. This study focused on the evaluation of extraction efficiencies in alkaline extractions of three economically interesting hardwood species: beech (Fagus sylvatica), birch (Betula papyrifera), and eucalyptus (Eucalyptus globulus). Substrate pulps were subjected to alkaline treatments at different temperatures and alkalinities using white liquor as the alkali source, followed by analyses of both pulps and hemicellulose-containing extraction lyes. The extracted hardwood xylans have strong potential as an ingredient in the food and pharmaceutical industries. Subsequent analyses revealed strong dependencies of the extraction efficiencies and molar mass distributions of hemicelluloses on the process variables of temperature and effective alkalinity. The hemicellulose content of the initial pulps, the hardwood species, and the type of applied base played minor roles.

Lignin profiling in extracted xylans by size-exclusion chromatography

Utilization of the polymeric parts of lignocellulose is expected to gain increasing importance in future biorefinery scenarios. In that respect, a particular focus is placed on hemicelluloses from different wood species gained from an industrially feasible upgrading step in the production of dissolving pulps from paper pulps. During alkaline post-extractions for hemicellulose removal, residual lignins are extracted as well. They are either covalently linked to the extracted hardwood xylans or simply co-dissolved in the alkaline lye. In order to better describe the lignin in xylan containing lyes, a method for lignin profiling was set up by hyphenating size-exclusion chromatography of xylans with UV detection which facilitates visualization of the residual lignin distribution. Simultaneous lignin quantification was achieved with lignin standards prepared from Kraft cooking liquors. The setup presented may serve as advanced characterization for novel xylan products.