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Hydrogen production via steam reforming of bio-oil is a potential method to reduce the dependence on the conventional fossil fuels. To investigate the reactivity of bio-oil and its difference with gasification tar and conventional fossil fuels, the steam reforming of various compounds (benzene, toluene, m-xylene, m-cresol, n-hexane, cyclohexane, 1-propanol, and acetic acid) was conducted in a fixed-bed flow reactor at various temperatures over a high-performance RuNi/BaOAl2O3 catalyst. As a whole, the reactivities of these compounds in steam reforming decrease in the following trend: n-hexane > cyclohexane > benzene > toluene > m-xylene >1-propanol > m-cresol > acetic acid. For the C6 hydrocarbons, benzene showed a lower reactivity than n-hexane and cyclohexane, due to the stable benzene ring. The reactivities of aromatic hydrocarbons decrease with the addition of methyl groups to the benzene ring due to electronic and steric effects. m-Cresol showed a lower reactivity than benzene, toluene, and m-xylene, suggesting that the incorporation of a hydroxyl group to the benzene ring hindered the steam reforming reaction. Besides the steam reforming reactions, the side reactions such as hydrogenolysis, demethylation, decomposition, and methanation of CO and CO2 also occurred. A benzene ring can be formed by the dehydroaromatization of n-hexane or cyclohexane, while the reverse reaction cannot occur due to the thermodynamic limit. The largely containing acetic acid in bio-oil needs a higher reforming temperature than the other compounds and is easy to be thermally decomposed into coke at low temperatures, which increases the difficulty of bio-oil steam reforming.

Two types of SO4 2–/ZrO2 solid acid catalysts with various calcination times were prepared via incipient wetness impregnation of (NH4)2SO4 to hydrothermally synthesized ZrO2 and subsequently employed to catalyze the esterification of palmitic acid with methanol. The resulting catalysts were characterized by X-ray diffraction (XRD), Fourier transform infrared (FTIR) spectroscopy, and temperature-programmed oxidation (TPO) to elucidate their physicochemical properties, morphology, and deactivation mechanism. A calcination procedure is required to transform the amorphous ZrO2 into the crystal form. Both chelating and bridged bidentate SO4 2– coordinate with the ZrO2 surface. The calcination at 600 °C could well eliminate the water in the catalyst and a further higher temperature would accelerate the loss of SO4 2–. Long-time calcination also decreases the catalytic activity due to the transformation of monoclinic ZrO2 into tetragonal one and the slow leaching of SO4 2–. The catalytic activity increases with increasing catalyst loading amount, reaction temperature, and molar ratio of palmitic acid to methanol, while the heating temperature over 65 °C and excess methanol amount are unfavorable to the esterification reaction due to the low-boiling-point methanol and attenuation of the palmitic acid concentration. It appears that the reaction conditions of 65 °C, 6 wt % catalyst, 25:1 of methanol to palmitic acid, and 4 h reaction time are economically optimal under atmospheric pressure. The catalyst could not be well regenerated by the ultrasonic methanol washing method because of refractory organic residues. The catalyst activity could be well recovered without major activity loss by the calcination at 600 °C for 1 h. The catalyst deactivation is due to contamination by the refractory organic residues in the catalyst as well as by the leaching of SO4 2–, and thus both the calcination temperature and time should be strictly controlled to achieve a better catalyst lifetime.