面向环己烷氧化的纳米氧化物负载钛基电催化膜反应器构建及催化协同机制

Controllable catalytic oxidation of cyclohexane with high efficiency and selectivity under mild conditions is a major chanllenge in oxidation chemistry and industrial chemistry. The objective of this proposed project is to develop a three-dimensionally electrocatalytic metal-membrane reactor (ECMMR) with a nano-metallic oxide loading on the porous Ti-based electrocatalytic membrane as a filter and an anode for cyclohexane oxidation to produce cyclohexanol and cyclohexanone as well as adipic acid without any oxidant and initiator added. During the ECMMR operation at 2-5 V, strong oxiding species such as •OH etc. would be generated to facilitate the oxidation of cyclohexane with the function of membrane convection-enhanced mass transfer under mild conditions. The present work focuses on the selection of cyclohexane solution system, the microstructural design and preparation of titanium-based electrocatalytic membrane materials, surface electrochemical and chemical properties, calculation and design of nano-metallic oxide via in situ loading on the 3D Ti-based electrocatalytic membrane based on the density functional theory and the electrochemical principle so as to understand the interaction rules between electrocatalytic efficiency and microstructure of the catalyst. To design the membrane reactor, the relationship among reactor operation parameters, the selectivity of different products, catalytic efficiency and the conversion of reactant etc as well as the synergistic effect of reaction and separation would be investigated. The influence of active species generated in the reactor on the the conversion of reactant and its mechanism would be explored according to molecular dynamics simulation theory of catalytic reaction. Finally, a method to obtain a controllable and high efficiency synthesis of adipic acid would be developed. The successful implementation of this project will enrich and extend the basic theory of membrane technology and electrochemical synthesis. At same time, the present study has a great academic value and promosing practical applications and would provide a novel method for the oxidation of cyclohexane.

环己烷氧化的高效、高选择性是有机合成及工业技术亟待解决的难题。本课题提出以多孔金属钛膜为基膜，原位负载纳米金属氧化物构筑三维电催化金属膜电极体系，以此为阳极构建膜反应器催化氧化环己烷制备环己醇/酮及己二酸。在低压电场作用下（2-5V）诱导电催化膜产生强氧化性的活性物种（如•OH等）并借助膜的分离功能实现环己烷温和条件下的可控氧化。着重研究环己烷多相体系构建，依据密度泛函理论计算从分子尺度上揭示金属氧化物纳米颗粒的微观结构、“微通道”对电极/溶液的界面化学、吸附、催化等性能之间的关联作用。设计膜反应器，探索反应器操作参数、反应物转化率、产物选择性、催化效率等之间的相互关系及反应-分离协同作用机制。通过理论模拟从分子层面诠释活性物种的形成及其作用机制，最终实现己二酸的可控制备。本课题成果的实施将丰富和拓展膜科学以及电化学合成的基础理论，为环己烷氧化提供一种全新的方法，具有重要的学术和应用价值。

本项目以微孔钛膜为基膜，分别采用溶胶-凝胶法、电沉积以及H2还原等方法分别成果制备三维纳米V2O5/Ti、MnOX/Ti、γ-MnO2/Ti、r-V2O5电催化膜电极。通过构建环己烷-水-溶剂（乙醇/乙腈/乙酸/丙酸/丙酮等）三元相图，探索溶剂体系以及催化剂种类对电催化氧化环己烷的影响规律。设计、构建五十级电催化膜反应器（ECMR），通过实验和理论计算模拟、反应动力学等探究反应-分离协同作用机制研究。主要结果如下：（1）通过溶胶-凝胶法制备MnOX/Ti膜电极，并构建ECMR，探索环己烷-水-溶剂三元反应体系的相容性。在最佳的环己烷-水-乙酸三元体系条件下，ECMR环己烷转率14.6% ，环己醇和酮总选择性为 99.8% 。但以溶胶-凝胶法制备的纳米片状 V2O5/Ti膜电极为工作电极，环己烷-水-丙酮为反应体系构筑ECMR，环己烷转化率为16.8%，环己酮选择性为90.2 %。（2）采用溶胶凝胶法，通过调控偏钒酸铵和酒石酸的比例，分别制备出纳米棒、片、球三种形貌膜电极：V2O5 NRs/Ti、V2O5 NSs/Ti和V2O5 NPs/Ti。其中V2O5 NSs/Ti电极表现出高比表面积（35.2 m2 g-1）和电化学活性面积（4.04 cm2），电化学活性最优。且以V2O5 NSs/Ti膜电极为工作电极，通过响应面实验优化，环己烷转化率可达到28.4%，KA油选择性大于99%。同时，采用三电极电沉积法可以制备出更小尺寸V2O5 NRs（直径20～50 nm）负载Ti膜电极，其比表面积和电化学活性面积分别提高至50.1 m2 g-1和7.52 cm2。其构筑的ECMR环己烷转化率达35.5%，KA油的选择性高于99%，表现出更加优异的性能。（3）通过H2还原法在350℃下对电沉积法制备的V2O5 NRs/Ti处理，构筑具有氧空位缺陷的r-V2O5 NRs/Ti膜电极。其构建的ECMR环己烷转化率高达55.5%，KA油选择性高于99%。（4）以r-V2O5 NRs/Ti膜电极为工作电极，过硫酸钠为电解质时，单级ECMR环己烷转化率高达62.73%，环己醇/酮总选择性为99%，己二酸的选择性为28.0%，成功实现从环己烷催化氧化制备己二酸的目标。（5）以r-V2O5 NRs/Ti膜电极构建五十级ECMR，由于累积效应、产物环己酮促进作用等，ECMR环己烷转化率为95.