New Carbon-based Hybrid Catalysts Design And The Study Of Their Application In Dehydrogenation Reaction

Butenes and butadiene are widely used as monomers in the manufacture of polymers and fine chemicals.Owing to the abundance of light alkanes,the direct use of this low-cost raw material to produce butenes and butadiene is a high value-added reaction in petrochemical industry.Activated carbon(AC)has a porous structure,abundant edge and large specific surface area which results in a great propensity for oxygen chemisorption and generation of oxygen groups.Additionally,the low-cost and scalable production from various biomass sources in recent studies make AC feasible for practical industrial application.However,due to the amorphous structure,AC is unstable in presence of O2 at high temperature and the carbonyl groups can’t be selectively formed,which hinders its application in oxidative dehydrogenation(ODH)reactions.Nanocarbon materials(carbon nanotubes,CNTs)with well-ordered structure exhibit remarkable stability and coke-resistance in ODH reactions,and the surface quinone and ketonic groups were proven to be central to the dehydrogenation pathway.Liquid-phase oxidation with HNO3 is one way to generate various oxygen functionalities on the CNT surface but it produces a large amount of acid waste,limiting its industrial application.This thesis focuses on the functionalization of carbon catalysts and their catalytic performance for ODH reactions,and further investigate the relationship between the structure and the catalytic performance of the catalysts.1.A facile and efficient oxidative method to prepare highly selective CNT catalysts for ODH of n-butane is reported.Magnesium nitrate salts as precursors were used to produce defect-rich CNTs through solid-phase oxidation.Skeleton defects induced on the CNT surface result in the selective formation of quinone groups active for the selective dehydrogenation.The as-prepared catalyst exhibits a considerable selectivity(58%)and yield(11.4%)to C4 olefins,which is superior to that of CNTs oxidized with liquid HNO3.Through the introduction of MgO nanoparticles on the CNT surface,the desorption of alkenes can be accelerated dramatically,thus enhancing the selectivity.This study provides an attractive way to develop new nanocarbon catalysts.2.Cubic MgO nanoparticles were successfully introduced on the surface of reduced-graphene oxide(rGO)by the above-mentioned "solid-solid" method using magnesium nitrate as precursor.The obtained MgO nanoparticles are uniformly assembled on the surface of rGO,forming a sandwich structure which is beneficial to the mass transfer in catalytic reaction.The introduction of-highly basic MgO nanoparticles could promote the desorption of products and inhibits deep oxidation.This strategy can be also used to modif-y nanocarbon catalysts with other nitrate salts like cerium nitrate,which can create nanopores on CNT catalysts,while this structure is unstable in ODH reaction of n-butane and shows low catalytic stability.3.Partially graphitic AC decorated with few-layer graphene is facilely fabricated by the simple high-temperature calcination.The graphitic transformation significantly enhances the anti-oxidation property,long-term stability of AC during the ODH reaction,and especially dramatically increases the graphitic edge areas where the active ketonic carbonyl groups are selectively formed in ODH reactions.A high reactivity with 41.5%selectivity and 13.2%yield to C4 alkenes over the optimized catalyst was achieved,which is superior to all the previous reported carbon catalysts and shows a great potential for industrial application.