Preparation Of Carbon-based Catalysts And Catalytic Oxidation Of Aromatic Alcohols And Terpenes

Carbon-based nanomaterials are a class of excellent new catalytic materials,owing to their unique advantages,such as,high specific surface areas,excellent chemical stability,renewable and recyclable.And this promising materials are widely used as supports of metal-supported carbon catalysts and metal-free carbon catalysts,especially in the selective oxidation process.Thus,designing and developing carbon-based catalysts with excellent performance and broadening their application in various types of oxidation reactions,and exploring its mechanism of activating molecular oxygen during the reaction process is of great scientific and practical research significance.In this work,a series of carbon-based catalysts were developed and applied to the selective oxidation of benzyl alcohol,terpenes and biomass-based alcohols,and good reaction results were obtained.The main results are as follows:Primarily,a series of cobalt-containing deep eutectic solvents were designed,and the corresponding Co-N-C catalysts were prepared by pyrolysis of the deep eutectic solvents,and the catalysts were applied to the selective oxidation of benzyl alcohol.The experimental results show that the Co-N-C catalysts can efficiently catalyze the selective oxidation of benzyl alcohol to corresponding aldehyde/ketone with yields above 90% without the addition of exogenous alkali and using molecular oxygen as the benign oxidant.Further control experiments show that the synergistic catalysis between nitrogen-doped carbon carrier and Co-N species is the main active center.Secondly,the Co/N-C catalysts with ultra-low cobalt loading were prepared by high temperature pyrolysis of cobalt precursors encapsulated in ZIF-8 pore cages,and their catalytic oxidation performance in allylic oxidation was investigated.The selective allylic oxidation of a-pinene to verbenone under mild solvent-free reaction conditions with molecular oxygen as terminal oxidant,the conversion rate of ?-pinene is 90%,and the yield of verbenone is up to 85%.Characterization and control experiments of catalysts show that ZIF-8 template sacrificial agent can disperse cobalt active sites well,making it have excellent catalytic performance.In addition,the catalyst has wide applicability and high catalytic activity for the selective oxidation of cinnamalol and other terpenes.The conversion rate of cinnamalol to cinnamaldehyde is up to 98%.Finally,the ultrahigh nitrogen-doped graphene catalysts were prepared by direct pyrolysis of the nitrogen-rich biomass precursors.And the catalysts can efficiently activate oxygen molecules without additives and cocatalysts,catalyzing the selective oxidation of 5-hydroxymethylfurfural to furan-2,5-dicarbaldehyde with a yield of 60%.Further experimental results show that the high content of graphite-nitrogen species and pyridine-nitrogen species are the key factors for activating oxygen molecules,and the electron paramagnetic resonance capture experiments confirm that the oxygen-active species are superoxide free radicals.This work not only provides a new idea for the efficient oxidation catalyzed by metal-free carbocatalysts,but also provides a feasible strategy for the simple preparation of nitrogen-doped graphene materials.In conclusion,a series of carbon-based nanocatalysts were designed and prepared in this paper,and their catalytic activity and selectivity in selective oxidation process were investigated.And activation mechanism and reaction mechanism of molecular oxygen were systematically studied,which provided a new strategy for the development of new and efficient carbon-based catalysts.