NMR Characterization of Pyrolysis Oils from Kraft Lignin

Abstract

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.

Fast Pyrolysis of Four Lignins from Different Isolation Processes Using Py-GC/MS

“…The yields of acids and alcohols decreased as the pyrolysis temperature increased. Ben et al also found that the concentration of acetic acid and methanol in light oil produced by lignin pyrolysis decreased as temperature rose [26]. The 13.3% yield of phenols indicated that only a fraction of the EHL decomposition pathway occurred at 350 °C.…”

A Review on The Bioconversion of Lignin to Microbial Lipid with Oleaginous Rhodococcus opacus

“…The liquid products from pyrolysis are known as pyrolysis oils which separate into two immiscible phases: heavy oil and light oil [79]. A pyrolysis light oil fraction of switch grass used as the sole carbon source in a fermentation with R. opacus resulted in increased oleaginicity (22-26%) and improved lipid titers (0.06-0.12 mg/ml) (Table 1, #6).…”

“…A pyrolysis light oil fraction of switch grass used as the sole carbon source in a fermentation with R. opacus resulted in increased oleaginicity (22-26%) and improved lipid titers (0.06-0.12 mg/ml) (Table 1, #6). The pyrolysis resulted in low molecular weight water-soluble substances in light oil fraction which seems to play a role in oleaginicity and improved lipid titers [79].…”

Integrated biorefineries: CO2 utilization for maximum biomass conversion

“…Nevertheless, research into biomass pyrolysis is multi-disciplinary and multi-dimensional. The diverse array of these research activities include advanced analytical chemistry methods for bio-oil characterization [16][17][18], developing kinetic models for the pyrolysis reactions [19], computational fluid dynamic studies [20], design of new reactors [21], developing new heating methods such as microwave assisted pyrolysis [22][23], optimizing the bio-oil yield [24], developing various bio-oil upgrading methods [25], process intensification [26], techno-economic analysis [27,28] and environmental assessment [29], in addition to enterprise-wide and supply chain optimization [30][31][32]. A recent review of the research into biomass fast pyrolysis is provided by Meier et al, [33].…”