Photodegradation of Acidolysis Lignin from BCMP

Mohammad Azadfallah,Ahmad Latibari,Seyed Mirshokraei

doi:10.3390/molecules13123129

Mohammad Azadfallah, Ahmad Latibari + Show 1 more

Open Access

https://doi.org/10.3390/molecules13123129

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Journal: Molecules	Publication Date: Dec 15, 2008
Citations: 18	License type: CC BY 4.0

Affiliation: Islamic Azad University, Karaj, University of Tehran

Abstract

A mild acidic dioxane extraction method was employed to isolate lignin from hardwood bleached chemimechanical pulp (BCMP). The isolated lignin was then purified and undergone elemental analysis. To study the photodegradation behavior, the lignin samples were impregnated onto the Whatman filter papers and irradiated with UV light for various periods. The photolyzed lignin was then recovered and analyzed by 1H-NMR spectroscopy. Phenylpropane-based formula (C9) of CMP pulp lignin and the photolyzed samples were then established with elemental analysis and 1H-NMR spectroscopy data. The results indicated that the benzaldehyde and benzoic acid type compounds were the main photodegradation products of BCMP lignin. The lignin photodegradation probably involved the degradation of phenylcoumaran units. Irradiation also increased the phenolic hydroxyl group content and decreased that of methoxyl groups, due to demethoxylation. The degrees of aromatic ring condensation were increased upon continuing the irradiation time, which imples the formation of condensed structures in photolyzed lignin.

Highlights

Lignin-rich papers made from mechanical pulps turn yellow when exposed to light and this phenomenon is a major barrier for using mechanical pulps in papers that require long-term brightness stability
The results indicated that the benzaldehyde and benzoic acid type compounds were the main photodegradation products of bleached chemimechanical pulp (BCMP) lignin
Our results indicate that photodegradation of acidolysis lignin isolated from hardwood BCMP is accompanied by a decrease in intensity of a part of the aliphatic proton NMR resonanances, while new signals apperar in the aromatic-olefinic and the aldehyde regions, suggesting that Cα-Cβ bond cleavage and formation of benzaldehyde and benzoic acid type compounds could be dominant reactions in the light-induced degradation of BCMP lignin

Summary

Introduction

Lignin-rich papers made from mechanical pulps turn yellow when exposed to light and this phenomenon is a major barrier for using mechanical pulps in papers that require long-term brightness stability. The results indicated that the benzaldehyde and benzoic acid type compounds were the main photodegradation products of BCMP lignin. The degrees of aromatic ring condensation were increased upon continuing the irradiation time, which imples the formation of condensed structures in photolyzed lignin.

Results

Conclusion