非晶态Pd-B/Al2O3催化剂用于邻氯硝基苯加氢合成邻氯苯胺的研究

用化学还原法制得了Pd-B/Al2O3非晶态催化剂,并用于邻氯硝基苯液相加氢反应的研究.采用XRD、SEM、SAED等技术手段对催化剂进行了表征,表明Pd-B以超细颗粒的形式分散在载体上,并且明确了催化剂的非晶态性质、结构形态等.以邻氯硝基苯液相加氢为目标反应,对所制备催化剂的催化性能进行系统评价.在反应温度90℃、氢气压力1.0MPa的反应条件下,邻氯硝基苯的转化率达99.9%,邻氯苯胺的选择性达98.0%;在不加脱卤抑制剂的情况下,脱卤率小于2%,表明负载Pd系非晶态催化剂具有较好的邻氯硝基苯加氢活性及良好的选择性,优于Pd基晶态催化剂和Ni基晶态催化剂.从催化剂的微观结构、金属-载体相互作用、活性组分在载体表面的几何效应和电子效应等方面对非晶态催化剂响影响邻氯硝基苯加氢性能进行了讨论和解释.

Liquid-Phase Hydrogenation of o-Chloronitrobenzene over Pd-B/Al2O3 Amorphous Alloy Catalyst

Hydrodechlorination is a difficult problem when hydrogenation of o-chloronitrobenzene is performed over catalysts without dechlorinating depressant added. In this article an efficient Pd-B/Al2 O3 amorphous alloy catalyst which could increase the conversion of substrates and decrease the dechlorination of the products in such reactions was reported. The catalyst prepared by impregnation-chemistry reduction method was employed in the liquid-phase hydrogenation of o-chloronitrobenzene, and the results of the experiments demonstrate that the catalyst prepared has better catalytic performances than that of the corresponding crystallized Pd/Al2 O3 catalysts and Ni catalysts. When using Pd-B/Al2O3 as catalyst in the reaction, the conversion and selectivity are more than 99.9% and 98% respectively, and the dechlorination of o-chloronitrobenzene is less than 2.0% without any dechlorinating depressant added, while the dechlorination will exceed 8% when the crystallized Pd/Al2O3 catalyst or Ni catalyst is used instead. Based on SEM, XRD and SAED characterization, which disclose the state of the catalyst on the surface of the support and its amorphous nature, the relationship between the interaction of the support and the amorphous metals on its surface and the catalytic performances of the catalyst were discussed. It is concluded that the main factors which effect the hydrogenation of o-chloronitrobenzene are the unique structure of the support and the nature of the amorphous metals on it.