磷酸镍纳米管的合成及其催化环己烯环氧化反应性能

Synthesis of Nickel Phosphate Nanotubes and Their Catalytic Performance for Cyclohexene Epoxidation

在不添加有机模板剂的情况下,通过尿素缓慢分解调节局部pH值,水热法合成了具有均一孔道直径的磷酸镍纳米管材料(NiPO-NTs).采用N2吸附-脱附、吡啶吸附红外光谱和氨程序升温脱附对材料进行了表征,并将其用于催化H2O2氧化的环己烯反应中,考察了反应条件对环氧化反应性能的影响.结果表明,NiPO-NTs具有狭窄的孔径分布,比表面积为96.6m2/g,其表面酸中心以弱Lewis酸为主.该反应中以乙腈为溶剂较为适宜,高温和高H2O2/环己烯摩尔比有利于提高环己烯转化率;而低温和高H2O2/环己烯摩尔比有利于提高环氧环己烷选择性.在60oC,H2O2/环己烯摩尔比为3,反应6h时,环己烯转化率可达50.6%,环氧环己烷选择性为72.1%.

Nickel phosphate nanotubes（NiPO-NTs） with a uniform pore size distribution were prepared by urea-assisted hydrothermal synthesis in the absence of any organic template.Calculations from N2 adsorption-desorption isotherms of NiPO-NTs revealed a narrow pore distribution around 2.7-4.2 nm and a surface area of 96.6 m^2/g.NiPO-NTs was used to catalyze the epoxidation of cyclohexene using hydrogen peroxide as the oxidant.Infrared spectroscopy of adsorbed pyridine and NH3 temperature-programmed desorption characterization results showed that the weak Lewis acid was predominant on the surface of NiPO-NTs.CH3CN was found to be a suitable solvent for the epoxidation.The reaction conversion increased with increasing reaction temperature and H2O2/cyclohexene molar ratio,whereas the selectivity for epoxycyclohexane increased with decreasing temperature and increasing H2O2/cyclohexene molar ratio.High cyclohexene conversion（50.6%） and selectivity for epoxycyclohexane（72.1%） were obtained at 60 ℃,6 h,and H2O2/cyclohexene of 3.