Pre-Extraction of Hemicelluloses from Hardwood Chips Using an Alkaline Wood Pulping Solution Followed by Kraft Pulping of the Extracted Wood Chips

Abstract

Mixed southern hardwood chips were extracted with an alkaline wood pulping solution called kraft green liquor. This aqueous solution containing mainly sodium carbonate and sodium sulfide was applied at different alkali charges (expressed as Na 2 O) of 0, 2, 4, and 6% on dry wood weight. The extractions were performed at 160 °C for effective times ranging from about 1-2 h to determine the effect of extraction severity on pulp yield and composition of the extracted liquor. The severity of hemicellulose extraction time and alkaline charge controls the concentration of acetic acid and monosaccharide sugars available for downstream processing, the accumulation of degradation products such as organic acids and furans in the extract, and the pulp yield attainable for the extracted wood chips. As the alkali charge was increased, the amount of acetate side chains on the hemicelluloses and the dissolved lignin in the extract increased but the carbohydrate and sugars in the extract decreased appreciably. Water extraction (0% alkali addition) released the greatest amount of carbohydrates, up to 30 g/L measured as component sugars, but resulted in the greatest decrease in pulp yield, dropping from 47% to 35%. Extraction with 2% green liquor increased the pulp yield to 51% while greatly reducing the component sugars to 8 g/L. Data obtained in this work will allow selection of optimum hemicellulose extraction conditions for integrating the extraction operation into the Kraft pulping process.

Comparison of hot-water extraction and steam treatment for production of high purity-grade dissolving pulp from green bamboo

“…Up until now, numerous methods, including dilute mineral acid (Al-Dajani et al 2009;Jahan 2008) and alkali (Walton et al 2010) prehydrolysis, hot-water extraction (HWE) , organosolv (Fink et al 2004), and acid/alkaline sulfite and steam treatments (STs) (Hinck et al 1985;Sixta 2006), have been subjected to extract hemicelluloses from the lignocellulosic feedstock prior to kraft pulping. However, acidic extraction methods are associated with uncontrollable equipment corrosion problems, significant lignin condensation, high yield loss and polydispersity of cellulose, although they do increase the solubilization rate of hemicellulose than that purewater extraction does (Al-Dajani et al 2009;Fink et al 2004).…”

“…However, acidic extraction methods are associated with uncontrollable equipment corrosion problems, significant lignin condensation, high yield loss and polydispersity of cellulose, although they do increase the solubilization rate of hemicellulose than that purewater extraction does (Al-Dajani et al 2009;Fink et al 2004). Near-neutral organic solvent processing (methanol or ethanol/water systems) and alkali extraction can overcome these shortcomings; unfortunately, the recyclability and costs of solvents for the former process (Fink et al 2004), and the low selectivity of the latter process (Helmerius et al 2010;Walton et al 2010) impair their further development. Therefore, because it uses water as the sole reagent and because it is based on existing equipment and practical production experience within the kraft pulp industry, it is not surprisingly that the water-based prehydrolysis-kraft (PHK) process is currently regarded as the most environmentally friendly and industrially scalable route to produce dissolving pulp as part of a forest biorefinery Li et al 2010;Sixta 2006).…”

Chemical Pretreatments of Wood Chips Prior to Alkaline Pulping - A Review of Pretreatment Alternatives, Chemical Aspects of the Resulting Liquors, and Pulping Outcomes

“…Alkaline pretreatment can shorten the cooking times and lower the need for alkali charge of the subsequent pulp cooking process. Also, alkaline pulping liquors, such as white and green liquors, can be used for pretreatments as such (Ban et al 2003a(Ban et al ,b, 2004Lucia 2003, 2005;Ban et al 2009;Walton et al 2010a;Wu et al 2010;Yoon and van Heiningen 2010;Gonzalez et al 2011;Jun et al 2012;Meng et al 2014;Kim et al 2015;Wang et al 2015). Pretreatments conducted with white and green liquors utilize proven technologies for the sophisticated recovery of all the used chemicals at a very high efficiency, and they can be easily integrated into existing pulp mill operations (Jin et al 2010).…”

“…While the needed energy production can be based on various alternative production systems (wind, solar, hydropower, biomass, nuclear fission, and fusion), the production of materials, such as chemicals, polymers, and fuels, mainly depends on biomass. For these reasons, different biorefinery processes integrated with modern pulp and paper mills have gained great interest, especially during the last few decades (Kamm et al 2006;Ragauskas et al 2006;Huang et al 2010;Walton et al 2010a;Alén 2011;Marinova et al 2014). This approach includes the modification of a conventional pulp mill to incorporate elements of an integrated forest biorefinery (IFBR) mill (van Heiningen 2006;Hämäläinen et al 2011;Baijpai 2012;Resalati et al 2012;Moshkelani et al 2013).…”

Chemometric Study on Alkaline Pre-treatments of Wood Chips Prior to Pulping

“…Of these alternatives, the alkaline extraction of wood chips is the most promising when combined with an existing industrial alkaline pulping process (Yoon et al 2011;von Schenck et al 2013), as it reduces the cooking times and the need for alkali charge in the subsequent pulping process. In addition, green and white pulping liquors can be used for pre-treatments (Walton et al 2010;Yoon and van Heiningen 2010). However, as in chemical pulping, the reaction mechanisms of alkaline pre-treatments are extremely complex, unselective, and not fully understood.…”