Comparative characterization of milled wood lignin from furfural residues and corncob

Furfural residues are by-products from the process of furfural production with corncobs. The cellulose in the residues can be used to produce ethanol, but lignin, the other main component in the residues, inevitably exerts unfavourable effects on the enzymatic hydrolysis process. In order to reveal the effects and make an efficient utilization of the lignin, the characteristics, especially the variation during furfural production, should first be investigated. In this paper, the milled wood lignin (MWL) of the furfural residual (FR) and corncob were separated and a comparative study of the MWL fractions was made in terms of the UV, FT-IR, 1H and 13C NMR spectra as well as the molecular weight and the thermal stability. It was found that the proportion of the three structure units in the two kinds of lignin fractions was different and that some reactions had taken place on the benzene rings during furfural manufacture. The methoxyls in the lignin structure units had been removed partially, and the groups conjugated with the benzene rings were destroyed. Moreover, the alcoholichydroxyl in the lignin of the corncob reduced and transformed into carbonyl. Both the degradation of the lignin and the condensation reactions have emerged during the furfural production.

Lignin of corncob in acidic mediums can turn into a novel positively charged construction, which may be attacked by degradation fragments with nucleophilicity, forming novel lignin composition in furfural residues.Figure optionsDownload as PowerPoint slideHighlights
► Furfural residues are lignocellulosic waste of furfural production with corncobs.
► Native lignin of furfural residue was first separated and characterized.
► Comparison of the paper will uncover lignin variation during furfural manufacture.
► Results indict demethoxyl and condensation has taken place on the benzene rings.
► Alcoholichydroxyl has partly transformed into carbonyl during furfural production.