Charge-Transfer Complexes in Kraft Lignin Part 1: Occurrence

Abstract

Dedicated t o P r o f . Dr. K a r l K r a t e l ABSTRACT C h a r g e -t r a n s f e r complexes were found t o o c c u r between k r a f t l i g n i n and a n added model quinone, 3 , 5 -d i -~-b u t y 1 -1 , 2 -b e n z o q u i n o n e . The o c c u r r e n c e of c h a r g e -t r a n s f e r i n t e r a c t i o n s was a l s o a p p a r e n t i n an o x i d i z e d k r a f t l i g n i n w i t h a n i n c r e a s e d quinone c o n t e n t . I n t h e s e systems, f r e e p h e n o l i c groups w i t h i n t h e l i g n i n were cons i d e r e d t h e donor s p e c i e s and ortho-quinones t h e complementary a c c e p t o r m o i e t i e s . Carbon-I4 l a b e l i n g r e v e a l e d t h a t t h e quinone c o n t e n t of t h e i n v e s t i g a t e d k r a f t l i g n i n averaged 3%. These q u i n o n e s were determined t o have a molar a b s o r p t i v i t y of 528 L/mol-cm. Upon sodium borohydride r e d u c t i o n of t h i s l i g n i n , o n l y o n e -t h i r d of t h e absorbance d e c r e a s e c o u l d be accounted f o r by t h i s number of quinones. The remaining t w o -t h i r d s of t h e d e c r e a s e i n absorbance was a s s i g n e d t o t h e d i s r u p t i o n of c h a r g e -t r a n s f e r complexes. The quinones, t h e r e f o r e , played a d u a

Lignin modification in the initial phase of softwood kraft pulp delignification with polyoxometalates (POMs)

“…An increase in the band at 1650 cm -1 is consistent with quinone production as proposed by Weinstock et al (1993) based on NIR, FT-Raman and UV/Vis spectral studies of softwood KP during POM delignification. Similar FTIR results were obtained after different oxidative treatments and attributed to quinone group formation in lignin (Furman and Lonsky 1988;Poppius-Levlin et al 1999). A lower intensity of the aromatic skeletal vibration indicates a loss of aromaticity (Kirk and Chang 1975), which may be caused by quinone formation or by aromatic ring Brought to you by | University of Georgia Libraries Authenticated Download Date | 6/7/15 8:47 PM cleavage, in the course of which muconic acid or cyclic carbonate-type compounds are formed.…”

Characterization of the transformations of lignocellulosic structures upon degradation in planted soil

“…Lignin modification with Si-oligomers promotes condensation/aromatization of HL matrix upon incubation in soil during the first vegetation season. For KL, having high content of stilbene and styrene sub-structures [42], aromatization and condensation of the structure is observed at earlier incubation time (12 weeks) and the effect of Simodification in this case is not as potent as it is observed for HL.…”

Ionomers From Kraft Lignin for Renewable Energy Applications

“…Of the plant cell wall polymers, cellulose has been widely explored to make green electron (Zhu et al, 2016 ) or ion-conducting materials (Seo et al, 2009 ; Bayer et al, 2016 ; Zhu et al, 2016 ; Vilela et al, 2019 ). However, lignin has been underutilized as an ionomer and majorly used to synthesize porous carbon (graphene, carbon fiber) (Kontturi, 1988 ; Naseem et al, 2016 ) or charge storage materials (Kontturi, 1988 ) [requiring oxidation of phenol groups of lignin to quinone (Furman and Lonsky, 1988 ; Milczarek and Inganas, 2012 ; Milczarek and Nowicki, 2013 ; Thakur et al, 2014 ; Zhu et al, 2016 ) or mixing with quinone (Furman and Lonsky, 1988 )]. Lignin is a three-dimensional (3D) amorphous, aromatic polymer functionalized with polar ether linkages (-O-) and hydroxyl (–OH) groups.…”