硝基苯加氢合成对氨基酚用负载铂催化剂的制备

Preparation of Supported Platinum Catalyst for Selective Hydrogenation of Nitrobenzene to p Aminophenol

用甲醛还原沉积法制备了活性炭负载的铂催化剂 (Pt/AC)和不同载体负载的铂催化剂 ,并考察了催化剂对硝基苯加氢制备对氨基酚反应的催化性能 .结果表明 ,还原Pt(Ⅳ )的甲醛用量是影响催化剂性能的关键因素 ,甲醛必须过量而且存在一个最佳值 .增加催化剂的铂负载量 ,不能有效提高加氢反应速度 ,反而易降低对氨基酚选择性 ;低铂负载量催化剂具有较高的活性、选择性及稳定性 .XPS和TEM表征结果表明 ,金属铂集中分布于活性炭颗粒外部 ,其颗粒大小介于 2～ 12nm间 .炭载体催化剂的活性和选择性明显高于金属氧化物载体催化剂 .

Activated coke supported platinum (Pt/AC) was prepared in aqueous solution by HCHO reduction-precipitation, and other supports, such as carbon and metal oxides, were also used to prepare platinum catalyst. The activity of the samples was evaluated in hydrogenation of nitrobenzene to p-aminophenol. It was demonstrated that the HCHO amount for reducing Pt(IV) is the key-factor to influence the catalyst activity. HCHO must be overdose, but there exists an optimal dose value. Increasing Pt loading can not augment the reaction rate, but can decrease the selectivity for p-aminophenol. The Pt/AC catalyst with low Pt loading (w (Pt) = 1%) has high activity, selectivity and stability, and the results of XPS and TEM indicated that the metallic Pt particles have a size of 1-12 nm and locate outside of the catalyst grain. Both the activity and the selectivity of Pt/C were higher than those of Pt/MO ( metal oxide). Adding an appropriate amount of Mg into Pt/AC can improve its catalytic performance, but adding Pd or Rh does not work.