A Study of the Pyrolysis Products of Kraft Lignin

Abstract

In order to valorize lignin wastes to produce useful aromatic compounds, the thermal degradation pyrolysis of Kraft lignin in the absence of catalysts has been investigated at 350, 450, and 550 °C. The high content of sulfur in the fresh sample led to the formation of S-containing compounds in products whose evolution in the gas phase was monitored through GC-MS analysis. Pyrolytic gas is rich in CH4, CO, CO2, and H2S with the presence of other sulfur compounds in smaller amounts (i.e., CH3SH, CH3-S-CH3, SO2, COS, and CS2). Biochar morphology and elemental composition have been investigated by means of SEM and EDX. The carbon content reaches ~90% after pyrolysis at 550 °C, while the oxygen content showed a decreasing trend with increasing temperature. From GC-MS analysis, bio-oil resulted rich in alkyl-alkoxy phenols, together with (alkyl)dihydroxy benzenes and minor amounts of hydrocarbons and sulfur compounds. NaOH/H2O and EtOH/H2O extraction were performed with the aim of extracting phenolic-like compounds. Sodium hydroxide solution allowed a better but still incomplete extraction of phenolic compounds, leaving a bio-oil richer in sulfur.

Investigating the Effect of Operational Variables on the Yield, Characterization, and Properties of End-of-Life Olive Stone Biomass Pyrolysis Products

“…The effect of reaction time (1 and 3 h) and N 2 flow (batch or semi-batch conditions) on the pyrolysis products distribution is shown in Figure 2 . Biochar (BC) and Liquid (L) yields were determined by gravimetric analysis and then the amount of Pyrolytic Gas (PG) was evaluated relying on total mass balances (by difference) [ 7 ]. Based on the obtained results, changing the reaction time from 1 to 3 h and the N 2 flow conditions, the product distribution remained mainly unaffected.…”

“…Carbonaceous matrix could strongly absorb the IR radiation and cover the characteristic features of still incompletely converted biomass. However, FT-IR spectra show characteristic absorptions in the OH region (3600–3400 and 1700–1500 cm −1 ), due to adsorbed water on KBr, and a weak band of C−C deformation at 1420 cm −1 [ 1 , 7 ] and a complex feature in-between 1000–800 cm −1 . The UV-vis-NIR spectra demonstrate full absorption of light in both the visible and UV range.…”

“…The -OH deformation modes of cellulosic units are also present in this region whereas the band at 1331 cm −1 could be due to -OH in-plane deformation of the phenolic group. The peaks in the range of 1000–1300 cm −1 are related to different C-O and C-C coupling interaction stretching while the peaks below 1000 cm −1 are likely due to -OH and -CH out-of-plane deformation modes [ 1 , 7 ].…”

“…However, there are still significant challenges to be addressed to fully realize the potential of biomasses in meeting the global energy demand. Therefore, the functional impact of biomasses on the global energy cycle is contingent upon conducting further research to assess the practicality of their large-scale implementation and to evaluate the potential for generating valuable chemical intermediates and products [ 7 ]. The olive sector is a major contributor to the agricultural biomass waste stream.…”

Evolution of the Olive Oil Industry along the Entire Production Chain and Related Waste Management

“…Pyrolysis or carbonization instead is realized by previously heating the material to a sufficiently high temperature (about 280 • C) to cause the breakage of the heavy organic molecules and trigger a series of exothermic reactions capable of achieving further heating of the mass up to 500-600 • C. Under these conditions, one obtains practically anhydrous coal and high energy density representing the main product. At the same time, a gas is produced that contains all the water initially present in the feed, the volatile organic substances and the less volatile ones resulting from the thermal splitting of the larger molecules into coal, and compounds that at room temperature have a bituminous appearance [139,140]. When the moisture content of the feedstock is not excessively high, the combustion of the gaseous phase may be sufficient to support the endothermic phase of the pyrolysis process.…”