Solid-State NMR Investigation of Bio-chars Produced from Biomass Components and Whole Biomasses

Bio-char is a by-product from thermochemical treatment of biomass and has been identified as an energy condensed product with a comparable heating value as commercial coal. However, the combustion of such solid product as an energy resource is only a preliminary application. It is highly possible to convert bio-char, which always has a condensed aromatic and porous structure to various high-value products. The investigations of the structures and formation pathways for the bio-char are very important to any future applications. In this study, six different biomass components, including cellulose, lignin, and tannin, and three whole biomasses-pine wood, pine residue, and pine bark-have been used to produce bio-char at 400, 500, and 600 A degrees C. Solid-state NMR and FT-IR have been employed in this study to characterize the structures for the bio-chars. The results indicated that the bio-chars produced from lignin contained some methoxyl groups, and the bio-chars produced from tannin contained significantly higher amount of phenolic hydroxyl groups. Compared to the bio-chars produced from pine wood and residue, the bio-chars produced from pine bark contained more aromatic C-O bonds, and aliphatic C-O and C-C bonds, which may be due to the significantly higher amount of lignin and tannin in the pine bark. However, the elevated amounts of aromatic C-O and aliphatic C-O and C-C bonds in the bio-chars from pine bark appeared to be completely decomposed at 600 A degrees C.