金属氧化物催化尿素与苯酚合成水杨酰胺

Synthesis of Salicylamide from Urea and Phenol Catalyzed by Metal Oxides

在反应釜中考察了几种金属氧化物催化尿素与苯酚反应合成水杨酰胺的活性,并对催化活性较高的ZnO和CaO的催化机理进行了探讨。实验结果表明,ZnO和CaO都具有较高的催化能力,这是因为两者都有利于尿素热分解形成活性中间体异氰酸。ZnO能与异氰酸配位使其活化,高效合成水杨酰胺;CaO能稳定苯酚中的苯氧负离子,高效地活化苯酚。ZnO是该合成反应均相催化剂的前体,CaO是该反应的多相催化剂。在相同反应条件下,ZnO的催化活性高于CaO。研究ZnO与CaO混合物的催化效果发现,二者的混合物能同时活化两个反应物从而起到协同作用,达到最佳的催化效果。以0.10 g ZnO和0.10 g CaO的混合物为催化剂,在反应温度240℃、反应时间12 h、尿素用量6 g、苯酚用量94 g的条件下,水杨酰胺的收率为54.3%。

The synthesis of salicylamide from urea and phenol over metallic oxide catalysts were investigated in a batch reactor. The results revealed that zinc oxide and calcium oxide exhibited high catalytic ability because the both could promote urea decomposition to isocyanate acid. Zinc oxide could improve the salicylamide synthesis by coordination with isocyanate acid and calcium oxide could activate phenol by stabilizing the phenoxy anions. Under same reaction conditions, the activity of zinc oxide was higher than that of calcium oxide. The mixture of the two oxides possesses a synergistic effect on activating both urea and phenol simultaneously, which results in the highest salicylamide yield. Under the reaction conditions： reaction temperature 240 ℃, reaction time 12 h, phenol dosage 94 g, urea dosage 6 g and the mixture of 0.10 g zinc oxide and 0.10 g calcium oxide as the catalyst, the yield of salicylamide could be 54.3%.