Dissolved Lignin and Other Aromatic Substances in Thermomechanical Pulp Waters

Abstract

Dissolved aromatic substances in water suspensions of unbleached and peroxide-bleached spruce thermomechanical pulp (TMP) were isolated by sorption on XAD-8 resin and fractionated into lignin and oligomeric aromatic substances (OAS). The fractions were characterized by chromatographic (GC and HP-SEC) and spectrometric (FT-IR, 13 C-NMR, GC-MS) methods, as well as by GC after direct on-line pyrolysis and thermally assisted hydrolysis and methylation. The dissolved lignin in unbleached TMP water was structurally similar to spruce milled-wood lignin (MWL), but its average molar-mass was lower and the mass distribution more narrow. The oligomeric aromatic substances included phenolic dimers, trimers, and tetramers that were structurally different from those of MWL. After peroxide bleaching the amount of dissolved semipolar (MTBE) extractives and oligomeric aromatic substances was We thank M.Sc Nina Å kerback for the FT-IR analyses of lignin samples. Thanks are due to Kenneth Sundberg for valuable comments on the manuscript.109 much lower. The amount of dissolved lignin from wood fibers was, on the contrary, much higher. The lignin released from TMP after bleaching was extensively oxidized and had a slightly higher average molar-mass than lignin released from unbleached TMP.

Separation of Galactoglucomannans, Lignin, and Lignin-Carbohydrate Complexes From Hot-Water-Extracted Norway Spruce by Cross-Flow Filtration and Adsorption Chromatography

“…Attempting to characterize the aromatic material, Pranovich et al (2005) dissolved TMP through heat treatment combined with mechanical treatment and used XAD resin to adsorb aromatic species. About 10% of the sorbate was insoluble in methanol after freeze drying and was characterized to contain 11% mannose, glucose, and galactose in a 4.8:1.3:1 relation.…”

“…The sugars suggest a GGM structure and were suggested to be covalently bound to the aromatic species isolated on the resin. With regard to the application of XAD resins for fractionating lignocellulosics in the solution state (Pranovich et al 2005), to trap aromatics dissolved from TMP, Schwartz and Lawoko (2010) applied it successfully to separate acid soluble lignin and furfural from monosugars resulting from the acid hydrolysis of hemicellulose extracts. In contrast, the present work deals with the separation of a lignocellulosic solution of a polymeric/ oligomeric nature.…”

“…Sorptive means have long since been used to remove aromatic substances from industry waste waters, and there are numerous evaluations of the cost and performance of such sorbent material (Lin and Juang 2009). The most frequently used sorbents in lignin carbohydrate research are the XAD and DAX series of polystyrene-divinylbenzene and polyacrylic resins from Rohm and Haas (Willfor et al 2003a;Schwartz and Lawoko 2010;Pranovich, et al 2005). The popularity of these sorbents is due to their low cost and preference for aromatic material in ligno-cellulosic suspensions.…”

Mechanical Pulping: Peroxide-based ATMP refining of spruce: energy efficiency, fibre properties and pulp quality

“…It also deacetylates hemicellulose (galactoglucomannan) and demethylates pectins (Sjöström 1989, Pranovich et al 2003, Konn 2006, Saarimaa 2007. Hydrogen peroxide, on the other hand, is responsible for introducing new carboxylic acid groups in lignin through oxidation (Thornton et al 1993, Pranovich et al 1994, Sundberg 1999 and it seems also to be able to defragment the lignin network leading to lower degree of cross-linking (Gierer et al 1993, Gierer et al 1994. This leads to some dissolution of low-molecular lignin compounds, but the effect of hydrogen peroxide is still considered to be of ligninpreserving nature and non-delignifying character (Chang, Allan 1971, Gierer, Imsgard 1977, Gratzl 1986, 1987.…”

Water Barrier Arabinoxylan Hemicelluloses from Sugarcane Bagasse

“…The structural composition of lignin was determined by pyrolysis GC-MS with tetramethylammonium hydroxide (TMAH) addition (Pranovich et al, 2005). …”