Photocatalytic Cyclohexane Oxidation Performance Of The Doped TiO₂

The oxidation of cyclohexane to KA-oil?cyclohexanone and cyclohexanonl?is an important process for the commercial production of nylon-6,nylon-66 polymers and other fine chemicals.Compared with the traditional thermal catalytic oxidation of cyclohexane in industrial production,photocatalysis is an emerging technology that has the advantages of environmental friendliness,green,energy saving and high efficiency?Therefore,the use of semiconductors for photocatalytic oxidation of cyclohexane has attracted the interest of many researchers.Among many semiconductors,titanium dioxide?Ti O₂?has been extensively studied due to its good stability,superior photocatalytic activity and low cost.Unfortunately,the wide band gap Ti O₂makes it unable to respond under visible-light illumination.Therefore,we modified Ti O₂by doping and applied it to photocatalytic cyclohexane oxidation.In this paper,we firstly synthesized the Ti³⁺self-doped Ti O₂(Ti³⁺/Ti O₂)via a modified facile hydrothermal method.Secondly,the crystal structure,microstructure and the optical performance were investigated by various characterization techniques.Finally,the effects of temperature,time and oxygen pressure were studied to identify the optimal conditions for cyclohexanone formation.The possible reaction mechanism was explored for the visible-light photocatalytic selective oxidation of cyclohexane over Ti³⁺/Ti O₂.Experimental results show that the Ti³⁺/Ti O₂extends the absorption region to visible light spectrum and restrains the reorganization of photoexcited electron-hole pairs and has a high selectivity of cyclohexanone.The doping of non-metal elements can simultaneously expand the absorption region to visible light spectrum and increase photocatalytic activity,therefore we choose to prepared Ti O₂by simply hydrolyzing tetrabutyl titanate and heating the mixture of Ti O₂and urea to obtain the N-Ti O₂.The as-prepared are characterized by UV-vis?UV-vis Diffuse Reflectance Spectra?,PL?Photoluminescence spectroscopy?and XPS?X-ray photoelectron spectroscopy?.Then,the effects of prepared temperature and doping density of N-doped samples were studied,and we explore the possible reaction mechanism for the visible-light photocatalytic selective oxidation of cyclohexane.Experimental results show that the N-Ti O₂improves the selectivity of the KA oil and enhances the convision of cyclohexane.