Photodegradation of acidolysis lignin from BCMP.

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 (1)H-NMR spectroscopy. Phenylpropane-based formula (C(9)) of CMP pulp lignin and the photolyzed samples were then established with elemental analysis and (1)H-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.

Synthesis, spectroscopic characterization and DFT calculations of ß-O-4 type lignin model compounds.

ß-O-4 type lignin model compounds with the title of Erythro-2-(2-methoxyphenoxy)-1-(3,4,5-trimethoxyphenyl)-1,3-propanediol and Erythro-2-(2-methoxyphenoxy)-1-(4-Hydroxy-3,5-dimethoxyphenyl)-1,3-propanediol were synthesised and some modifications and improvements on them were introduced. These compounds were characterized by IR, Mass and NMR spectroscopy. Density functional theory (DFT) calculations were performed for the title compounds using the standard 6-31G(*) basis set. IR, (13)C and (1)H NMR of the title compounds were calculated at the DFT-B3LYP level of theory using the 6-31G(*) basis set. In this work comparison between the experimental and the theoretical results indicates that the DFT-B3LYP method is able to provide satisfactory results for predicting the properties of the considered compounds.