Co-N-C catalyst modified by alkaline additive for hydrogenation

Abstract

The development of M-N-C catalysts (M = Fe, Co, Ni, etc.) was hindered by poor distribution of metal species and large particle size. In this work, alkaline additives were introduced during the precursor synthesis stage to regulate the distribution of metal components. Through hydrothermal and pyrolysis methods, Co-N-C catalysts (Co-N-C-NH3, Co-N-CO3, and Co-N-C-OH) were synthesized by using folic acid as the carbon and nitrogen source, cobalt chloride as metal salt, and ammonia solution, sodium carbonate solution, and sodium hydroxide solution as alkaline additives, respectively. The influence of different alkaline additives on the morphology, composition, and structure of Co-N-C catalysts was systematically analyzed through systematic characterization methods. The results indicated that the Co-N-CO3 catalyst prepared using sodium carbonate solution has a largest specific surface area, smallest and most evenly distributed Co nanoparticles. Moreover, the catalytic activity of the prepared Co-N-C catalyst in the hydrogenation of nitrobenzene was evaluated, and the influence of alkaline additives on its catalytic performance was further explored. Among them, the Co-N-CO3 catalyst achieved the best in the hydrogenation of nitrobenzene after reacting at 110 °C and under 1 MPa hydrogen for 3 hours, with a nitrobenzene conversion rate of over 99%. Comparative experiments confirmed that Co nanoparticles and Co-Nx sites constituted the active centers of the catalytic reaction. This strategy provides theoretical support and practical basis for optimizing the performance of Co-N-C catalyst.