• Energy Research
• US close

Abstract The influence of barium addition to a Ni/Al2O3 catalyst on the reaction intermediates formed, the activity, resistance of the catalyst to coking, and properties of the coke formed after acetic acid steam reforming were investigated in this study. The results showed the drastic effects of barium addition on the physicochemical properties and performances of the catalyst. The solid-phase reaction between alumina and BaO formed BaAl2O4, which re-constructed the alumina structure, resulting in a decrease in the specific surface area and an increase in the resistance of metallic Ni to sintering. The addition of barium was also beneficial for enhancing the catalytic activity, resulting from the changed catalytic reaction network. The in-situ diffuse reflectance infrared Fourier transform spectroscopy (DRIFTS) study of the acetic acid steam reforming indicated that barium could effectively suppress the accumulation of the reaction intermediates of carbonyl, formate, and C=C functional groups on the catalyst surface, attributed to its relatively high ability to cause the gasification of these species. In addition, coking was considerably more significant over the Ba–Ni/Al2O3 catalyst. Moreover, the Ba–Ni/Al2O3 catalyst was more stable than the Ni/Al2O3 catalyst, owing to the distinct forms of coke formed (carbon nanotube form over the Ba–Ni/Al2O3 catalyst, and the amorphous form over the Ni/Al2O3 catalyst).

In this study a non-aqueous potentiometric titration method has been developed to quantify the carboxylic acids and phenolics in bio-oil. Quarternary ammonium hydroxide was used as the titrant and a mixture of tert-butanol and acetone was used as the solvent to differentiate the acidic components with distinct acidities. The heavy carboxylic acids, which cannot be identified with GC–MS, account for ca. 29–45% (mol basis) of all the carboxylic acids in the bio-oil from mallee wood. In addition, both the heavy and light phenolic components could be identified with the titration method developed, while GC–MS can only identify some light phenolic compounds (3% mol basis). The titration method was further applied to the determination of the concentrations of acidic components in the bio-oils from mallee wood, bark and leaves. The pyrolysis of mallee wood produced the highest yields of acidic components while that of leaves produce the lowest. The successful development of the titration method for quantification of these heavy carboxylic acids and phenolics provides useful information for the further upgrading of bio-oil.

AbstractThe aim of this research was to evaluate the potential for the stabilization of biomass‐derived pyrolysis oils by using acid‐catalyzed (Amberlyst 70) reactions with alcohol (T=140–170 °C, P≈20 bar (1 bar=105 Pa)). The alcohol‐stabilized oils were further upgraded by catalytic hydrotreatment (T=400 °C, non‐sulfided NiMo/Al2O3 catalyst) to give a biofuel. The concept was evaluated experimentally in terms of overall mass and energy balances and biofuel properties. The pyrolysis oil used in this study was obtained by fractional condensation of pyrolysis vapors and had a very low water content that favored the equilibrium conversion of the stabilization reactions. The energy efficiency was between 44 and 48 %. Preliminary results with acid‐leached biomass showed that 43 % of levoglucosan in the pyrolysis oil was converted into methyl levulinate after the pyrolysis oil was purified. The proposed integrated concept of alcoholysis can be applied locally at the pyrolysis oil production site.

Abstract Alkalinity is an important parameter affecting adsorption and evolution of reaction substrates in steam reforming reactions. In this study, steam reforming of guaiacol, a model compounds in the volatiles in gasification of biomass, over Ni/SiO2 modified with Na, Mg or La was investigated. The results showed that the strong alkalinity induced by Na or Mg addition to Ni/SiO2 led to remarkably decreased catalytic activity. The high alkalinity also promoted formation and accumulation of the oxygen-containing species such as CO*, C–O–C aliphatic structure and carbonyl functionalities, which were precursors of the polymeric products with big π-conjugated structures and coke. La addition increased the alkalinity to a mild extent and promoted the nickel dispersion, enhancing the catalytic activity and the resistivity towards coking. The formation of the thermally stable amorphous coke in the Na or Mg modified catalyst wrapped nickel sites and led to rapid catalyst deactivation. Both amorphous form and in carbon nanotube form of coke defective structures were formed over La-Ni/SiO2 and Ni/SiO2 catalysts, resulting from the distinct reaction intermediates formed during the steam reforming of guaiacol.