磷酸镍纳米管的合成及其催化环己烯环氧化反应性能

 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 96.6 m2/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 60 oC, H2O2/环己烯摩尔比为 3, 反应 6 h 时, 环己烯转化率可达 50.6%, 环氧环己烷选择性为 72.1%.

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

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 m2/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 oC, 6 h, and H2O2/cyclohexene of 3.