Flower-like Cu/bone biochar for hydrogenation of vanillin: Importance of evolution of organic matter in chicken bone on property of the catalysts

Metal/biochar catalysts are prepared by direct impregnation of metal salts with biochar produced from pyrolysis. However, the surface structure of the catalyst carrier is affected by the pyrolysis temperature. Different pyrolysis temperatures can produce different pore structures, which can affect the dispersion of active metals. To verify this, Cu/bone biochar catalysts were prepared by directly supporting copper nitrate on the biochar from chicken bone pyrolysis at 400, 500, 650, and 800 °C, respectively. Catalytic performance of Cu/bone biochar catalysts for vanillin hydrogenation was evaluated. The results showed that the hydroxyapatite produced after pyrolysis of chicken bones was relatively stable, which made the catalyst with superior activity and reusability. The catalyst prepared by pyrolysis at a lower temperature had fewer pore structures on its surface, and the active metal Cu was easily sintered. With increasing pyrolysis temperature, organic matter gradually decreased and more pore structures were generated on the surface of the catalyst carrier, which was more conducive to the dispersion of metallic Cu species. The catalyst prepared from the chicken bone pre-pyrolyzed at 800 °C exhibited uniform dispersion of metal Cu, with the average particle size of Cu particles of 11.9 nm, achieving the yield of 91.7 % for 2‑methoxy-4-methyl phenol from hydrogenation of vanillin. In-situ IR characterizations also showed that, with the increase of pyrolysis temperature, the surface functional groups of the catalyst were more conducive to the hydrogenation of vanillin.