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High nitrogen content in Spirulina platensis -derived bio-oil is a highly undesirable feature in upgrading of bio-oil to biofuel via hydrodeoxygenation. However, the nitrogen species could be potentially used as dopant for tailoring the catalytic behaviors of metallic sites in heterogeneous catalysts. In this study, the nitrogen species in the bio-oil from hydrothermal carbonization (HTC) of Spirulina platensis was used to modify Co-based catalyst for enhancing their catalytic activity for hydrogenation of o -chloronitrobenzene (o -CNB). The results showed that the introduction of N species not only promoted dispersion of Co particles via formation of Co–N sites, but also generated extra pores and significantly increased H 2 uptake. The abundant Co–N sites, high dispersion of Co and higher surface area of N-doped catalyst (CoFeAl–N) jointly contributed to the enhanced catalytic activity for hydrogenation of o -CNB, achieving the yield of 90.3% for o -chloroaniline (o -CA) and lowering the activation energy from 63.0 kJ mol−1 (with N-free CoFeAl catalyst) to 55.1 kJ mol−1. The effectiveness of introducing nitrogen for enhancing catalytic activity for hydrogenation of o -CNB was also confirmed in the experiments for doping Co/Al 2 O 3 (prepared via impregnation) and CoAl (prepared via co-precipitation) catalysts with the Spirulina platensis derived bio-oil. Spirulina platensis derived bio-oil was used as N dopant for modifying cobalt catalysts for the hydrogenation of o-chloronitrobenzene. [Display omitted] • Functionalizing CoFeAl with N from Spirulina platensis bio-oil enhances Co dispersion. • N species react with Co, forming Co–N sites, increasing H 2 uptake by 71.5%. • N species enhances interaction with –NO 2 , lowering E a (12.5%) for hydrogenation. • CoFeAl–N achieves higher o -chloroaniline yield (90.3%) than N-free catalyst (6.0%). • Co–N sites, high dispersion of Co and developed pores enhance the hydrogenation activity. [ABSTRACT FROM AUTHOR]

Bio-oil as a carbon source can be used to prepare hybrid metal@carbon material while the polymerization of which generally prevents metals from exposure. In this study, melamine was used as a structural regulating agent for preparing Co/N/C catalyst via heating the mixture of cobalt nitrate, melamine and bio-oil for hydrogenation of o-chloronitrobenzene (o-CNB). The results showed that the Co species was encapsulated in the carbon structure from cross-polymerization of melamine and bio-oil at 600 °C. The further heating to 900 °C led to decomposition of melamine-derived substance, and meanwhile cobalt oxide was reduced and confined in the resulting carbon structure. The formed metallic Co catalyzed the growth of long carbon nanotube with cobalt on the tip, forming the Co/N/C catalyst of higher specific surface area (128.2 m2/g) and metallic Co dispersion (3.7%), rendering the superior activity for hydrogenation of o-CNB with the yield of o-chloroaniline up to 90.2%. The encapsulation or exposure of Co species was closely related to relative ratio of bio-oil and melamine in the catalyst precursors. Additionally, leaching of cobalt, due to dechlorination of o-CNB, was found to be an issue of Co/N/C catalyst but not for that of Ni/N/C catalyst. [Display omitted] • Heating mixture of CoNO 3 , bio-oil and melamine produces pin-like Co/N/C catalyst. • Bio-oil acts as a source of carbon skeleton to confine Co from aggregation. • Complexation with Co is essential for dispersion of Co in Co/N/C. • Balance of bio-oil and melamine determines exposure and access of metallic Co. • Catalyst obtained at 900 °C minimizes Co encapsulation, rendering superior activity. [ABSTRACT FROM AUTHOR]