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Abstract This study aims to investigate the importance of aromatic structures in tar to the destruction of tar itself during the volatile–char interactions. The same nascent char was subjected to interactions with two distinctly different volatiles (e.g. coal volatiles and biomass volatiles) at 700–900 °C. The results indicate that the aromatic structures in tar are more reactive with char than the non-aromatic structures, especially at high temperature (e.g. 900 °C). At lower temperatures (

Abstract This study aims to investigate the importance of steam to tar destruction during the volatile–char interactions. Steam was supplied in the absence and presence of nascent char during the pyrolysis/gasification of biomass at 850 °C. In the absence of char, steam has more significant effects on the reforming of large aromatic ring systems (e.g. >2 fused benzene rings) than small and isolated aromatics. In the presence of char, steam can significantly enhance the reforming of both large and small aromatic ring systems during the volatile–char interactions, especially when the steam–char reactions are also significant. The results indicate that the steam–char reactions are particularly inhibited in a thin char bed by the volatile–char interactions. It is believed that the steam–char reactions can produce additional active sties on the char, such as the radicals/intermediates of char gasification and/or the O-containing groups, to facilitate tar reforming during the volatile–char interactions.

Abstract Bio-oil cannot be directly used as biofuel mainly due to its abundant oxygen-containing functional groups. Therefore, bio-oil must be upgraded to produce high quality biofuels. As the first part of this series, this paper reports the transformation of GC-detectable light components during the hydrotreatment of bio-oil using noble-metal catalyst Pd/C over a wide range of reaction temperature (150–300 °C). Our results show that aldehydes were easily hydrogenated, with cyclopentanone and 2-methyl cyclopentanone among the observed products. During hydrotreatment, carboxylic acids such as propionic, butanoic and pentanoic acids were also observed in the liquid products. Furthermore, evolution of propyl guaiacol, ethyl guaiacol, methyl guaiacol, guaiacol and syringol confirms the depolymerisation of the lignin-derived oligomers during the hydrotreatment of bio-oil. The hydrogenation of the phenolic compounds also took place. In addition, the FT-IR analysis of the O-containing functional groups, especially carbonyl groups, confirms the trends found by GC–MS.

Abstract Carbohydrates are the intermediates/products during hydrolysis of biomass, which can be converted to value-added chemicals/biofuels via further acid-catalysis. The interactions between the typical carbohydrates/furans including glucose, fructose, raffinose, xylose, and furfural during their acid-catalyzed conversion in water/dimethyl sufoxide were investigated in this study. The insoluble polymer formed from the carbohydrates was measured and characterized with FT-IR, while the soluble polymers were characterized with a UV-fluorescence spectrometer. The interaction or cross-polymerization of xylose/glucose, fructose/raffinose, furfural/glucose, and furfural/fructose does exist, producing more soluble polymer but not significantly more insoluble polymer. The insoluble polymer deactivates the solid acid catalyst, slowing down conversion of sugars/intermediates. In addition, different sugars have very different propensities towards polymerization in water, which follows the order: fructose ~ raffinose

The simple incineration of wood-based panels (WBPs) waste generates a significant amount of NOx, which has led to urgency in developing a new method for treating the N-containing biomass residues. This work aims to examine the N evolution and physiochemical structural changes during the co-pyrolysis of fiberboard and glucose, where the percentage of glucose in the feedstock was varied from 0% to 70%. It was found that N retention in chars was monotonically increased with increasing use of glucose, achieving ~60% N fixation when the glucose accounted for 70% in the mixture. Pyrrole-N (N-5) and Pyridine-N (N-6) were preferentially formed at high ratios of glucose to fiberboard. While the relevant importance of volatile–char interactions to N retention and transformation could be observed, the volatile–volatile reactions from the two feedstocks played a vital role in the increase in abundance of glucose. With the introduction of glucose, the porous structure and porosity in chars from the co-pyrolysis were dramatically altered, whereas the devolatilization of glucose tended to generate larger pores than the fiberboard. The insignificant changes in carbon structure of all chars revealed by Raman spectroscopy would practically allow us to apply the monosaccharides to the WBPs for regulating N evolution without concerns about its side effects for char carbon structures.

Bio-oil tends to polymerize on heating, and understanding the mechanism by which it occurs is of importance for developing the methods for enhancing the polymerization of bio-oil to produce carbon ...

In this study, biochar was prepared via hybrid doping of N, O, and S by applying one-pot pyrolysis of poplar wood and S-containing urea formaldehyde at 900 °C. Different doping ratios were adopted, and the contents of O, N, and S were in the ranges of 2.78–5.56%, 2.16–4.92%, and 1.42–4.98%, respectively. This hybrid doping significantly enhanced the efficiency of the removal of tetracycline (40 mg/L) from wastewater to 71.84% in comparison with that attained by using normal poplar biochar (29.45%). The adsorption kinetics and isotherms indicated that the adsorption process was favorable and was dominated by chemisorption instead of physisorption; the dominant adsorption process may be justified by the existence of abundant functional groups. The adsorption capacity was barely related to the surface area (R2 = 0.478), while it was closely related to the concentration of graphitic N (R2 = 0.985) because graphitic N enhanced the π–π interactions. The adsorption capacity was also highly related to the proportion of oxidized N and oxidized S owing to hydrogen bonding, which may have overlapped with the contribution of O-containing functional groups. This study presents a simple hybrid doping method for biochar modification and provides fundamental insights into the specific effects of O-, N- and S-containing functional groups on the performance of biochar for tetracycline removal.

Abstract Steam reforming of bio-oils is a viable way to produce syngas, but certain challenges need to be overcome before its commercial application. One of the main issues is the formation of tar and coke. Investigation of the evolution/formation of aromatic structures in steam reforming is an effective way to understand the mechanism of tar/coke formation. In this study, the pyrolysis, steam reforming and catalytic steam reforming of mallee wood bio-oil and its lignin-derived oligomers were conducted in a quartz reactor at various temperatures (500–850 °C). The product tars were characterised by ultraviolet (UV) fluorescence spectroscopy. The results indicate that the interactions among the compounds degraded from lignin and cellulose/hemicellulose obviously affect the evolution of aromatic structures during the catalytic steam reforming of bio-oil. Furthermore, Raman spectroscopy of the catalyst provided information on the interactions of the volatile compounds and the deposit on the catalysts.