Hexenuronic Acid and Their Removal

The traditional kappa number method was developed in 1960 as a way to more quickly determine the level of lignin remaining in a completed or in-progress pulp. A significantly faster approach than the Klason lignin procedure, the kappa number method is based on the reaction of a strong oxidizing agent (KMnO4) with lignin and small amounts of other organic functional groups present in the pulp, such as hexenuronic acid. While the usefulness of the kappa number for providing information about bleaching requirements and pulp properties has arguably transformed the pulp and paper industry, it has been mostly developed for kraft, sulfite, and soda wood pulps. Nonwood species have a different chemical makeup than hardwood or softwood sources. These chemical differ-ences can influence kappa and Klason measurements on the pulp and lead to wide ranges of error. Both original data from Sustainable Fiber Technologies’ sulfur and chlorine-free pulping process and kappa and Klason data from various nonwood pulp literature sources will be presented to challenge the assumption that the kappa number accurately represents lignin content in nonwood pulps.

Download Full-text

Reactions of aromatic structures in brightness reversion of fully-bleached eucalyptus kraft pulps

Holzforschung ◽

10.1515/hf.2009.047 ◽

2009 ◽

Vol 63 (3) ◽

Cited By ~ 9

Author(s):

Anna-Stiina Jääskeläinen ◽

Katri Toikka ◽

Anni Lähdetie ◽

Tiina Liitiä ◽

Tapani Vuorinen

Keyword(s):

Resonance Raman ◽

Kraft Pulps ◽

Brightness Reversion ◽

Vis Spectroscopy ◽

Uv Resonance Raman ◽

Hexenuronic Acid

Abstract The role of aromatic structures in brightness reversion of fully bleached pulps was studied by UV resonance Raman (UVRR) and reflectance UV-Vis spectroscopy. The results clearly showed that ageing increased the aromatic band at approximately 1600 cm-1 in the UVRR spectra and the lignin band at approximately 280 nm in the UV-Vis spectra. This increase was probably due to increased conjugation of lignin and it was observed for all pulps regardless of the bleaching sequence. In addition to these lignin reactions, other unsaturated structures, such as hexenuronic acid groups, reacted during ageing.

Download Full-text

Evidence for the formation of lignin-hexenuronic acid-xylan complexes during modified kraft pulping processes

Holzforschung ◽

10.1515/hf.2006.022 ◽

2006 ◽

Vol 60 (2) ◽

pp. 137-142 ◽

Cited By ~ 11

Author(s):

Zhi-Hua Jiang ◽

Jean Bouchard ◽

Richard Berry

Keyword(s):

Acid Hydrolysis ◽

Kraft Pulp ◽

Kraft Pulping ◽

Order Kinetic ◽

Kraft Pulps ◽

First Order ◽

Pseudo First Order ◽

Hexenuronic Acid ◽

Kinetics Of ◽

Hydrolysis Of

Abstract The finding that hexenuronic acid (HexA) groups can be selectively removed from kraft pulps by acid hydrolysis has provided an opportunity to reduce bleaching chemicals. However, there is evidence that the acid hydrolysis is not uniform. In this report, we evaluate the kinetics of acid hydrolysis of HexA in a xylan sample enriched with HexA, a conventional kraft pulp, and three modified kraft pulps: anthraquinone pulp (Kraft-AQ), polysulfide pulp (PS), and polysulfide-anthraquinone pulp (PS-AQ). We found that HexA present in the xylan and conventional kraft pulp behaved similarly toward the acid hydrolysis throughout. On the other hand, HexA present in the Kraft-AQ, PS-AQ and PS pulps was heterogeneous toward acid hydrolysis and the reaction can be separated into two pseudo-first-order kinetic phases, each of which has a different rate constant. The kinetic data provide evidence for the formation of lignin-HexA-xylan complexes during modified kraft pulping processes.

Download Full-text

Pre-bleaching of kraft acacia pulp

Nordic Pulp & Paper Research Journal ◽

10.1515/npprj-2018-0082 ◽

2019 ◽

Vol 34 (2) ◽

pp. 165-172 ◽

Cited By ~ 1

Author(s):

Moinul Haque ◽

Moumita Nanjiba ◽

M. Sarwar Jahan ◽

M. A. Quaiyyum ◽

M. Zahangir Alam ◽

...

Keyword(s):

Acacia Mangium ◽

Kappa Number ◽

Acacia Auriculiformis ◽

Kraft Pulps ◽

Oxygen Delignification ◽

Acid Pretreatment ◽

Acacia Hybrid ◽

Pre Treatment ◽

Hexenuronic Acid ◽

Peroxyformic Acid

Abstract Kraft pulps from acacia hybrid, Acacia mangium of 8 years old and Acacia auriculiformis of 6, 8 and 10 years old were pre-treated with oxygen, peroxyformic acid and acid treatment prior to bleaching. The kappa number reduction was 52–63 % by oxygen delignification, 31–35 % by peroxyformic acid (PFA) pre-treatment and 11–13 % by acid pre-treatment. Oxygen delignified pulp required less chlorine dioxide charge to reach target brightness. At the consumption of 30 kg ClO2/ton of pulp, the pulp brightness reached to 65–71 % for the untreated pulp, 81–85 % for the oxygen delignified pulp, 81–82 % for the PFA treatment and 79–80 % for acid pre-treated pulp. COD load in bleached effluent was much lower in oxygen delignified pulp. Cold alkali extraction of unbleached and oxygen delignified pulps was also carried out with varying alkali charge to remove hexenuronic acid (HexA) from the pulp. Xylan removal from the pulp was insignificant and resulted in no removal of HexA. Acid pretreatment removed 55.7 % to 17.8 % HexA from acacia hybrid, 57.5 % to 16.3 % from A. auriculiformis of 10 years and 58.6 % to 20.1 % from A. auriculiformis of 6 years old, resulting in improved final pulp brightness.

Download Full-text

Impact on the Filtrate from Bleached Pulp Treated with Peroxymonosulfuric Acid for Effective Removal of Hexenuronic Acid

JAPAN TAPPI JOURNAL ◽

10.2524/jtappij.65.1071 ◽

2011 ◽

Vol 65 (10) ◽

pp. 1071-1075 ◽

Cited By ~ 7

Author(s):

Eiko Kuwabara ◽

Tetsuo Koshitsuka ◽

Mikio Kajiyama ◽

Hiroshi Ohi

Keyword(s):

Bleached Pulp ◽

Effective Removal ◽

Hexenuronic Acid

Download Full-text

Kinetics of delignification and hexenuronic acid decomposition during kraft pulp bleaching with peroxyacetic acid

Nordic Pulp & Paper Research Journal ◽

10.3183/npprj-2000-15-02-p142-149 ◽

2000 ◽

Vol 15 (2) ◽

pp. 142-149 ◽

Cited By ~ 5

Author(s):

Anna-Stiina Jääskeläinen ◽

Kristiina Poppius-Levlin

Keyword(s):

Kraft Pulp ◽

Peroxyacetic Acid ◽

Acid Decomposition ◽

Pulp Bleaching ◽

Kraft Pulp Bleaching ◽

Hexenuronic Acid ◽

Kinetics Of

Download Full-text

Voltammetric analysis of the bleachability of softwood kraft pulps

Holzforschung ◽

10.1515/hf.2004.111 ◽

2004 ◽

Vol 58 (6) ◽

pp. 581-587 ◽

Cited By ~ 1

Author(s):

Robert Bourbonnais ◽

Loredana Valeanu ◽

Michael G. Paice

Keyword(s):

Chlorine Dioxide ◽

Acid Content ◽

Black Spruce ◽

Kappa Number ◽

Western Hemlock ◽

Kraft Pulps ◽

Residual Lignin ◽

Redox Mediators ◽

Voltammetric Analysis ◽

Hexenuronic Acid

Abstract Kraft and oxygen delignified pulps with various kappa numbers were prepared from black spruce and western hemlock chips. The bleachability (ratio of kappa number decrease to chlorine dioxide applied) of the different pulps at the same kappa number varied with both wood furnish and delignification process. Thus, unbleached kappa number alone is not a reliable indicator of bleachability for these pulps. This may be due in part to the variable hexenuronic acid content of the pulps; those with higher ratio of hexenuronic acid content to kappa number (HexA/kappa) are harder to bleach. Voltammetric analysis of the same kraft pulps in the presence of redox mediators was found to measure both the content and reactivity of residual lignin. Peak current ratios of redox mediators correlated with pulp bleachability for all pulps. These ratios may therefore provide a more accurate prediction of bleachability than unbleached kappa number.

Download Full-text