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在2-硝基-4-乙酰胺基苯甲醚(NMA)催化加氢合成2-氨基-4-乙酰胺基苯甲醚(AMA)反应中,规整纳米Pd/C催化剂表现出很好的催化活性和选择性。但Pd/C催化剂在反应的套用过程中表现出反应活性逐渐降低。通过XRD、BET、EDS、XPS等物性表征以及Na2S滴定法和原子吸收法测定Pd含量的研究表明,钯微晶的长大、钯流失、催化剂中毒等不是引起Pd/C催化剂失活的主要原因,而Pd/C催化剂表面金属钯活性位在反应后被2-氨基-4-乙酰胺基苯甲醚产物等有机物覆盖可能是导致其性能逐渐降低的关键。使用酸洗法可以去除反应后Pd/C催化剂表面覆盖的2-氨基-4-乙酰胺基苯甲醚等有机物,释放金属钯活性位,实现Pd/C催化剂的性能有较大程度的恢复;而其他方法对Pd/C催化剂活性恢复的效果不明显。
In the synthesis of 2-amino-4-acetamidobenzyl ether (AMA) catalyzed by 2-nitro-4-acetamidobenzyl ether (NMA), the structured nano-Pd / C catalyst showed good Catalytic activity and selectivity. However, Pd / C catalysts show a gradual decrease in reactivity during the course of the reaction. The results of XRD, BET, EDS, XPS and other characterization, and the determination of Pd content by Na2S titration and atomic absorption spectrometry showed that the growth of Pd crystallites, the loss of palladium and the poisoning of catalyst were not the main reasons for the deactivation of Pd / C catalyst , While the activity of Pd on the surface of Pd / C catalyst is probably covered by the organic matter such as 2-amino-4-acetamide anisole after the reaction, which may be the key to the gradual reduction of its performance. The pickling method can remove the organic substances such as 2-amino-4-acetamidole and the like which are covered on the surface of the Pd / C catalyst and release the active sites of the Pd, so that the performance of the Pd / C catalyst can be recovered to a great extent. However, the effect of other methods on the recovery of Pd / C catalyst activity is not obvious.