Stability and complete regeneration of a Ni/MgAl2O4 catalyst in combined steam/dry reforming of raw bio-oil

The combined steam and dry reforming (CSDR) of bio-oil (the liquid product from biomass pyrolysis) represents an attractive pathway for CO 2 valorization along with sustainable syngas production. This study compares the performance in the CSDR process of a Ni catalyst supported on MgAl 2 O 4 spinel with 15 wt% Ni (15Ni/MgAl 2 O 4 ), with that of Ni catalysts supported on Al 2 O 3 prepared by different methods. The reactions were carried out in an automatized equipment with two units, for controlled pyrolytic lignin deposition in the first unit while the feed is volatilized (thermal treatment), and for reforming of the remaining oxygenates in the second unit in-line (fluidized bed reactor). The catalysts have been used under reaction-regeneration cycles. The reaction conditions were: 700 °C, CO 2 /C molar ratio, 0.6; steam/C ratio, 0.5; space time, 0.042 g Ni ·h/g oxygenates , and; time on stream, 6 h. The regeneration is performed in-situ, by coke combustion with air at 850 ºC for 2 h. The catalytic performance (activity, selectivity, stability and regenerability) is explained on the basis of the characterization results of the used and regenerated catalysts and the deposited coke. Although the initial CO 2 conversion (in the 14–18 % range) and syngas yield (in the 88–98 % range) show no significant differences among the catalysts, variations in catalyst stability and regeneration capacity are remarkable. Specifically, the 15Ni/MgAl 2 O 4 catalyst is the most suitable candidate for scaling up CSDR of bio-oil, due to its high stability (similar to that of the 36Ni/Al 2 O 3 -cp catalyst, obtained by reduction of a stoichiometric NiAl 2 O 4 spinel) and reproducible behavior in reaction-regeneration cycles. • Combined steam/dry reforming (CSDR) of bio-oil allows sustainable syngas production and CO 2 valorization. • Ni catalysts’ performance in the process is compared by reaction-regeneration cycles. • The support has a relevant effect on activity, coke deactivation and regeneration. • Deactivation is mainly due to amorphous coke deposition which blocks the Ni sites. • Ni supported in MgAl 2 O 4 spinel is totally regenerated by in situ coke combustion.