The effect of O 2 content in the oxidative steam reforming (OSR) of raw bio-oil has been studied, and the kinetic behavior, particularly deactivation, has been compared between two catalysts (Ni/La 2 O 3 -αAl 2 O 3 and Rh/CeO 2 -ZrO 2 ). The experiments have been carried out in an apparatus with two steps in series: (1) thermal treatment (at 500 °C, for the controlled deposition of pyrolytic lignin) and (2) catalytic in-line reforming in a fluidized bed. The reaction conditions have been as follows: oxygen/carbon ratio (O/C), 0, 0.17, 0.34, and 0.67; 700 °C; steam/carbon ratio (S/C), 6; space time, 0.3 g catalyst h/g bio-oil (for Ni/ La 2 O 3 -αAl 2 O 3 ) and 0.15 g catalyst h/g bio-oil (for Rh/CeO 2 -ZrO 2 ); time on stream, 4 h. The content and morphology of the coke deposited on the catalysts has been determined by temperature-programmed oxidation (TPO), and the deterioration of the metallic properties of the catalysts by temperature-programmed reduction (TPR) and X-ray diffraction (XRD). The results (biooil conversion, product yield and their evolution with time on stream) show that for Rh/CeO 2 -ZrO 2 catalyst the decrease in coke deposition as O/C ratio is increased involves attenuation of catalyst deactivation. Consequently, this catalyst is stable after 24 h operation for high O/C ratios, thus keeping constant the activity for reforming reactions and the WGS reaction, with a high yield of H 2 and low yields of CO, CH 4 , and hydrocarbons. However, for the Ni/La 2 O 3 -αAl 2 O 3 catalyst of lower activity than the Rh/ CeO 2 -ZrO 2 , the decrease in coke content as O/C ratio is increased does not involve a noticeable attenuation in catalyst deactivation, which is due to Ni sintering.

The regenerability of Ni catalysts in reforming reactions is a key factor for process viability. Accordingly, this study addresses the regeneration of two spinel NiAl 2 O 4 type catalysts by reaction-regeneration cycles in the oxidative steam reforming (OSR) of raw bio-oil. The spinel type catalysts were prepared by different methods including a supported Ni/La 2 O 3 -αAl 2 O 3 catalyst and a bulk NiAl 2 O 4 catalyst. The experimental setup consists of two units connected in series for i) the thermal treatment of bio-oil at 500 ºC, in order to control the deposition of pyrolytic lignin, followed by; ii) the oxidative steam reforming (OSR) of the remaining oxygenates in a fluidized bed catalytic reactor.The conditions in the OSR reaction step were: 700 ºC; oxygen/steam/carbon ratio (O/S/C), 0.34/6/1; space time, 0.75 g catalyst h/g bio-oil (for supported catalyst) and 0.15 g catalyst h/g bio-oil (for bulk catalyst). Three different strategies have been studied in the regeneration step by coke combustion, including the in situ regeneration inside the reactor at 650 ºC and 850 ºC, and the ex situ regeneration in an external oven at 850 ºC, for 4 h in all the cases. The behavior of the fresh and regenerated catalysts has been explained according to their metallic properties, determined by different characterization techniques (temperature programmed reduction (TPR), X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS), and transmission electronic microscopy (TEM)). According to these results, the combustion ex situ of the catalyst at 850 °C is able to completely regenerate the bulk catalyst, since these

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A reaction scheme has been proposed for the oxidative steam reforming (OSR) of raw bio-oil on a Rh/CeO 2-ZrO 2 catalyst, based on the study of the effect reaction conditions (temperature, space time, oxygen/carbon ratio and steam/carbon ratio) have on product yields (H 2 , CO, CO 2 , CH 4 , hydrocarbons). The runs were performed in a two-step system, with separation of pyrolytic lignin (first step) followed by catalytic reforming in a fluidized bed reactor (second step), under a wide range of reaction conditions (600-750 ºC; space time, 0.15-0.6 g catalyst h/g bio-oil ; oxygen to carbon molar ratio (O/C), 0-0.67; steam to carbon molar ratio (S/C), 3-9). The catalyst is very active for bio-oil reforming, and produces high H 2 yield (between 0.57 and 0.92), with low CO yield (0.035-0.175) and CH 4 yield (below 0.045) and insignificant light hydrocarbons formation. The proposed reaction scheme considers the catalyzed reactions (reforming, water gas shift (WGS) and combustion) and the thermal routes (decomposition/cracking and 2 combustion). The deactivation of the catalyst affects progressively the reactions in the following order: CH 4 reforming, hydrocarbons reforming, oxygenates reforming, combustion and WGS.

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