The pyrolysis of softwood (SW) kraft lignin was examined at 400, 500, 600, and 700 °C. The yields of pyrolysis oil, char, and gas were determined to be 35−44%, 57−38% and 8−18%, respectively. The pyrolysis oil has a comparable heating value with ethanol and coal. The elevated temperature of 700 °C was found as the point of primary decomposition of lignin and the secondary decomposition of pyrolysis oil. Gel permeation chromatography (GPC) and quantitative 13C and 31P NMR were used to characterize the pyrolysis oil. A 13C NMR database was created to provide a more accurate chemical shift assignment database for analysis of pyrolysis oils. On the basis of the results of 13C and 31P NMR for the pyrolysis oil, aliphatic hydroxyl, carboxyl, and methoxyl groups are eliminated during pyrolysis. Cleavage of ether bonds in lignin was also shown to be a primary decomposition reaction occurring during thermal treatment. The results of GPC analysis indicated that lower pyrolysis temperatures yielded a bio-oil that had a lower molecular weight and lower polydispersity value.

The analysis of chemical structural characteristics of biorefinery product streams (such as lignin and tannin) has advanced substantially over the past decade, with traditional wet-chemical techniques being replaced or supplemented by NMR methodologies. Quantitative 31 P NMR spectroscopy is a promising technique for the analysis of hydroxyl groups because of its unique characterization capability and broad potential applicability across the biorefinery research community. This protocol describes procedures for (i) the preparation/solubilization of lignin and tannin, (ii) the phosphitylation of their hydroxyl groups, (iii) NMR acquisition details, and (iv) the ensuing data analyses and means to precisely calculate the content of the different types of hydroxyl groups. Compared with traditional wet-chemical techniques, the technique of quantitative 31 P NMR spectroscopy offers unique advantages in measuring hydroxyl groups in a single spectrum with high signal resolution. The method provides complete quantitative information about the hydroxyl groups with small amounts of sample (~30 mg) within a relatively short experimental time (~30-120 min).

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This study investigates the role of β-zeolite acid site density on hydrocarbon and coke yields.

The pyrolysis of softwood kraft lignin, cellulose, and Loblolly pine wood was examined at 400, 500, and 600 °C. The analysis of the yields of pyrolysis products indicated that lignin yielded the largest amount of a heavy oil and char and only trace levels of a light oil. In contrast, cellulose produced minor amounts of a heavy oil and char and more light oil. All of the pyrolysis oils were analyzed by heteronuclear single-quantum correlationÀnuclear magnetic resonance (HSQCÀNMR) to analyze the structural components of the bio-oils, and three chemical-shift databases of compounds reported to be presented in pyrolysis oils produced from lignin, cellulose, and pine wood were employed for data analysis. On the basis of databases, analysis of the HSQCÀNMR spectral data provides chemical-shift assignment of 27 different types of CÀH bonds presented in the pyrolysis oils. The HSQCÀNMR analysis of these pyrolysis oils indicated that there are two different types of methoxyl groups presented in the pyrolysis oils produced from lignin and pine wood, which indicated that the native methoxyl group in the lignin rearranges during the thermal treatment. The content of aromatic CÀH and aliphatic CÀH bonds in the pyrolysis oils produced from lignin and pine wood was increased with increasing pyrolysis temperatures. Levoglucosan was shown to be one of the major components in the pyrolysis oils produced from cellulose and pine wood, and furfurals and phenols were also found as the major components in the cellulose pyrolysis oils. Most aromatic CÀH and aliphatic CÀH bonds in the pine wood pyrolysis oils were produced from the lignin component. The results demonstrate the capability of HSQCÀNMR to provide in-depth analysis of pyrolysis oils.

The pyrolysis of softwood (SW) kraft lignin in the presence of NiCl2 and ZSM-5 zeolite as an additive was examined at 700 °C. Gel permeation chromatography (GPC), quantitative 13C and 31P NMR were used to characterize the pyrolysis oil. Based on the results of 13C and 31P NMR for the pyrolysis oils, the use of zeolite during pyrolysis caused the near complete loss of aliphatic hydroxyl and carboxyl groups in the bio-oil and about 80% of methoxyl groups were also eliminated. The zeolite was shown to improve the decomposition of aliphatic hydroxyl groups, carboxyl, methoxyl groups, and ether bonds in the lignin during pyrolysis. In addition, as determined by 13C NMR, the oxygen content in the bio-oil decreased after the use of zeolite. The results of GPC analysis indicated that the addition of H-ZSM-5 zeolite with lignin provided a bio-oil that had ∼10% lower average molecular weight than the pyrolysis product acquired without the additive.

The pyrolysis of softwood (SW) kraft lignin in the presence of various H-ZSM-5 zeolites with different SiO2/Al2O3 mole ratios from 23/1–280/1 as additives were examined at 600 °C. Nuclear magnetic resonance (NMR), including quantitative 13C, 31P NMR, and heteronuclear single-quantum correlation (HSQC)-NMR, and gel permeation chromatography (GPC) were used to characterize various pyrolysis oils. On the basis of the results of the 13C and 31P NMR for pyrolysis oils, the use of H-ZSM-5 zeolites during the pyrolysis process caused the near complete decomposition of aliphatic hydroxyl and carboxyl groups. With the exception of carboxylic acid, the H-ZSM-5 zeolite with a relatively higher SiO2/Al2O3 mole ratio was more effective at the elimination of methoxyl groups, ether bonds, and aliphatic C–C bonds, and dehydration of aliphatic hydroxyl groups during pyrolysis. However, the H-ZSM-5 zeolite with a very large SiO2/Al2O3 mole ratio, such as 280, has only limited effects on the properties of upgraded pyrolysis oil. After the use of zeolite, the pyrolysis oils contain some polyaromatic hydrocarbons, the content of which decreased with an increasing SiO2/Al2O3 mole ratio of zeolite. GPC results show that the molecular weight decreased by 8–16% after the use of H-ZSM-5 zeolites.

COMING OF AGE: A method for investigating the accelerated aging of biomass pyrolysis oils is reported. The in situ NMR investigation, done by using quantitative ¹H, ¹³C NMR and heteronuclear single-quantum correlation (HSQC)-NMR techniques, reveals the chemical structural changes of pyrolysis oil during the aging process, providing insight into the mechanism of aging process.