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The structural changes of lignin at different stages of growth of Napier grass

100%

Zhou X. F.

tom vol. 60, nr 199

37--45

The aim of this study was to investigate the lignin composition and structure during Napier grass growth. Napier grass showed an increase in lignin, xylan, glucan content and a decrease in acetone extractives and ash content with its growth, while the content of cellulose and holocellulose reached the highest value after four months growth. In addition, milled-wood lignins (MWL) isolated from Napier grass were characterized with 2D-NMR and Py-GC-MS. The results obtained showed that GSH-type substructures were included in Napier grass lignin, whereas the S-G ratio decreased and the abundance of H-substructures increased during lignification. H-units were deposited at the earlier stages, whereas Napier grass was enriched in G-lignin during the late lignification, and S-units were reduced at the final stage. The differences in deposition of lignin units influenced the distribution of the different linkages of lignin units during Napier grass growth. All lignin samples showed the most abundant β-O-4', β-β' resinol linkages, whereas the data obtained by 2D-NMR indicated the similar development in GSH-type substructures with by Py-GC-MS during all stages of lignification.

Oxidation of a lignin model compound of benzyl-ether type linkage in water with H2O2 under an oxygen atmosphere catalyzed by Co(Salen)

51%

Zhou X. F. , Quin J. X. , Wang S. R.

Drewno : prace naukowe, doniesienia, komunikaty

2011

tom vol. 54, nr 186

15-25

The catalytic properties of Cobalt salen? complex in the oxidation of a lignin model compound [veratrylglycerol-beta-guaiacyl-alpha,gamma-dimethylether, VGD] have been investigated in order to obtain the mechanistic aspects of the reaction between Co(salen) and VGD under an oxygen atmosphere using hydrogen peroxide as an oxidant. VGD was found to undergo structural changes in response to the catalytic reaction as characterised by different analytical techniques (FT-IR, H-1 NMR and GC-MS), yielding 2-methoxy phenol and biphenyl. A mechanism for the oxidation of VGD was postulated.

Zbadano katalityczne właściwości kompleksu Co(Salen) w utlenianiu modelowego związku ligniny (veratrylglycerol-alfa-guaiacyl-beta,gamma-dimetyleter, VGD) w celu określenia mechanicznych aspektów reakcji pomiędzy Co(salen) i VGD w atmosferze tlenu przy zastosowaniu nadtlenku wodoru jako utleniacza. Zaobserwowano, że w VGD zaszły zmiany strukturalne w odpowiedzi na reakcję katalityczną, co przedstawiono za pomocą różnych technik analitycznych (FTIR, H-1 NMR oraz GC-MS). W efekcie otrzymano 2-metoksy fenol i bifenyl.