Abstract:

Ni-P/TiO₂ amorphous catalyst was prepared by chemical reduction method. By taking the α-pinene hydrogenation as a probe reaction, the effects of the preparation conditions on the catalytic properties were investigated. The suitable preparation conditions were as follows: TiO₂/NiCl₂?6H₂O mass ratio 3∶1, P/Ni molar ratio 2.5∶1, reaction temperature 25℃ and pH 11. Under these conditions, the catalyst showed excellent catalytic activity in the hydrogenation of α-pinene. The conversion of α-pinene, the enantioselective of cis-pinane and were 99.89%, 98.48% and 98.37%, respectively. And the catalyst could be reused for 8 times. XRD, BET, DSC, XPS and TEM were employed to investigate the structure difference of the catalysts before and after deactivation. The results showed that the fresh catalyst was spherical and well dispersed with uniform particle size of about 100nm. The introduction of TiO₂ effectively had improved the thermal stability of the Ni-P particles. The crystallization temperature increased by 78℃, 190℃ and 115.1℃. However, the deactivated catalysts exhibited deteriorated dispersion, and reduced content of Ni⁰, which was considered as the main reasons for the deactivation.

Key words: amorphous catalyst, Ni-P/TiO₂, α-pinene, hydrogenation, selectivity, deactivation

摘要：

采用化学还原法制备Ni-P/TiO₂非晶态催化剂，以α-蒎烯加氢反应为探针反应，考察了催化剂制备条件对其催化性能的影响，得到适宜的制备条件为载体与NiCl₂?6H₂O质量比为3∶1，P/Ni摩尔比为2.5∶1，反应温度为25℃，pH为11。结果表明：该条件下制备的催化剂对α-蒎烯加氢具有较高的催化活性，α-蒎烯转化率为99.89%，顺式蒎烷选择性为98.48%，收率为98.37%，且可重复使用8次。以XRD、BET、DSC、XPS、TEM为表征手段，对催化剂失活前后的结构及形貌进行了分析，结果表明：新鲜催化剂为粒径均一的球形颗粒，粒径约为100nm，分散性较好，引入TiO₂有效提高了Ni-P粒子的热稳定性，将其晶化温度分别提高了78℃、190℃和115.1℃，而失活催化剂的分散度、Ni⁰含量均有下降，出现了活性组分流失、氧化及团聚等现象，这可能是导致催化剂失活的主要原因。

关键词: 非晶态催化剂, Ni-P/TiO₂, α-蒎烯, 加氢, 选择性, 失活