Preparation Of MoO₃-Ag Based Nano-catalysts And Their Photothermal Synergistic Catalytic Performance For Cyclohexane Oxidation

Selective oxidation of hydrocarbons is essential for the production of high-value-added chemicals.In particular,cyclohexane oxidation to cyclohexanone(K)or cyclohexanol(A)(also known as KA oil)is widely recognized and used as one of the fundamental processes in organic chemistry and chemical industry.Based on the increasing demand for KA oil and other products in the world today,there are many problems in industrial production,such as high reaction temperature,high energy consumption,low conversion rate,low alcohol and ketone selectivity,complex processes,and more wastes.Therefore,the industry has also put forward higher requirements for the catalytic oxidation process of cyclohexane.The thermocatalytic cyclohexane oxidation reaction has high activity but high energy consumption and poor product selectivity.Photocatalytic technology can achieve high selectivity by adjusting the energy level structure,but the activity is not high and the efficiency is low.Combining the two and adopting photothermal synergistic catalysis The method may take into account the advantages of both,and obtain better catalytic performance than photocatalysis and thermal catalysis alone.Therefore,it is particularly important to continue to develop new photothermal catalysts with high activity,high selectivity and high stability for the study of cyclohexane oxidation.The following researches are mainly made in this article:(1)The blue MoO₃nanorods containing oxygen vacancies were synthesized by hydrothermal method with the assistance of formic acid,and the MoO₃-Ag composites were prepared by in-situ reduction of silver nitrate.The effects of different Ag loading amounts and other factors on the photothermal synergistic catalytic performance of cyclohexane oxidation were investigated.The MoO₃-Ag composite material with an Ag loading of 80 mg presents a significantly improved catalytic performance with a high conversion rate of 8.6%and a high selectivity of 99.0%.The excellent catalytic performance of the MoO₃-Ag composite catalyst can be attributed to the extended light absorption in visible light and near-infrared region by the plasmon resonance effect(SPR)of Ag nanoparticles and oxygen vacancies,and prevented charge recombination by the MoO₃-Ag Schottky heterojunction.(2)The GO-MoO_3-x-Ag ternary composite material was prepared by loading MoO_3-x-Ag on graphene oxide sheets by the scompounding process in solution.The combination of MoO_3-x-Ag and GO sheets can effectively prevent the agglomeration of the MoO_3-xcatalyst to obtain the improved activity and recyclability.The ternary composite material exhibits excellent photothermal synergistic catalytic cyclohexane oxidation activity with a conversion rate of 10.9%and a selectivity of 99.2%.The increased catalytic performance was caused by the increased dispersion,the extended ligh absorption by the unique plasmon resonance effect of silver nanoparticles,the decreased charge recombination and the excellent photothermal synergetic effect.(3)The blue MoO_3-xnanowires containing oxygen vacancies were synthesized by a simple hydrothermal method with the PVP stabilizer,and the MoO_3-x-Ag Pd composite materials of different proportions were prepared by the in-situ reduction method.The microstructure,structural composition,optical and photoelectrochemical properties of the composites were characterized.The increased catalytic performance can be obtained by the MoO_3-xbased composite materials.The best photothermal catalytic performance with the conversion rate of 11.3%,the selectivity of 99.0%,and good cycle stability can be achieved by the MoO_3-x-Ag Pd composite catalyst.The significant increased catalytic activity can be attributed to the synergetic effect of Ag Pd alloy nanoparticles,the optimized band gap structure,and the improved charge separation and transmission efficiency.