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Upgrading Paper-grade Softwood Kraft Pulp to Dissolving Pulp by Cold Caustic Extraction
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Author NameAffiliation
Chao Tian1,2,3 1. China National Pulp and Paper Research Institute, Beijing, 100102, China
2. Limerick Pulp and Paper Centre, Department of Chemical Engineering, University of New Brunswick, Fredericton, NB, E3B 5A3, Canada
3. Tianjin Key Laboratory of Pulp and Paper, Tianjin University of Science and Technology, Tianjin300457, China 
QingXian Miao4 4. College of Material Engineering, Fujian Agriculture and Forestry University, Fuzhou Fujian Pro-vince, 350002, China 
LinQiang Zheng2 2. Limerick Pulp and Paper Centre, Department of Chemical Engineering, University of New Brunswick, Fredericton, NB, E3B 5A3, Canada 
YongHao Ni2,3* 2. Limerick Pulp and Paper Centre, Department of Chemical Engineering, University of New Brunswick, Fredericton, NB, E3B 5A3, Canada
3. Tianjin Key Laboratory of Pulp and Paper, Tianjin University of Science and Technology, Tianjin300457, China 
Fund Project:The authors gratefully acknowledge the financial support from the Canada Research Chairs and NSERC CRD program, and the Tianjin Municipal Science and Technology Commission (Grant No. 12ZCZDGX01100).
 
Abstract:Cold caustic extraction has potential applications in the production of dissolving-grade pulps due to its ability to selectively remove hemicellulose from lignocellulosic materials.In this study, we demonstrate the conversion of paper-grade kraft pulp into dissolving pulp by a single-stage cold caustic extraction. Under the extraction conditions of 12 wt%NaOH lye, 11% pulp consistency, a temperature of 35℃, and 2 h, a paper-grade softwood kraft pulp was purified to high-grade dissolving pulp with 97.1% α-cellulose content, 1.2% pentosane content, and narrowed molecular weight distribution. The resulting extraction filtrate was concentrated by nano-filtration to obtain the hemicellulose content of 59.0 g/L, while the permeate was a clear NaOH solution with 10.9 wt%concentration. A process configuration was also proposed, integrating this cold caustic extraction process with existing pulp and paper production and multi-purpose utilization of the extraction filtrate.
keywords:cold caustic extraction  dissolving pulp  α-cellulose  membrane filtration  hemicellulose
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