NHPI催化分子氧氧化α—O—4型木质素模型分子

Liquid phase oxidation of α—O—4 bond of lignin with O2 in the presence of N—hydroxyl phthalimide under mild conditions

摘要:

本文以苄基苯基醚为模型分子，氧气为氧化剂，考察了N—羟基邻苯二甲酰亚胺（NHPI）对温和条件下分子氧氧化木质素醚键（α—O—4）的催化作用和多种可溶性过渡金属盐的助催化作用，探究了硝酸铜用量、反应温度和氧气分压对NHPI催化活性的影响。结果表明：NHPI能够在温和条件下催化分子氧氧化断裂木质素α—O—4键，生成相应的羰基化合物和酚羟基化合物，在可溶性的钴、锰、镍和铜盐中，铜盐对NHPI的助催化作用最好。在NHPI/Cu(NO3)2催化下，当氧分压高于0.5MPa时，苄基苯基醚的氧化反应对氧气为0级。过高温度会加剧目标产物苯甲醛和苯酚的深度氧化。以乙酸为溶剂，n（苄基苯基醚）：n（NHPI）：n（硝酸铜）=1：0.2：0.02，氧气分压为1.0MPa时，在110℃下反应15h苄基苯基醚的转化率为37.2%，苯甲醛和苯甲酸的总选择性为91.4%。

Abstract:

The catalytic effects of N—hydroxyl phthalimide combined with various transition metal salts on the oxidative breakage ofα—O—4 bond of lignin by O2under mild conditions were studied. Benzyl phenyl ether was adopted as the model compound ofα—O—4 bond.It is found that the cupric salts showed the highestpromotion effect on the catalytic activityof NHPI among the soluble cobaltous, manganous, nickel and cupric salts. Oxygen pressure higher than 0.5MPadoes not necessarily enhance the conversion of benzyl phenyl ether, the activation of α—His most likelythe rate-limiting step.A reaction temperature over 110 ℃ would lead to over oxidation of benzyl aldehyde and phenol.Benzyl phenyl ether conversion of37.2% and the total selectivity of benzyl aldehyde and benzoic acidas high as 91.4% were achieved in acetic acid under the conditions of 110℃, 1.0MPa O2,15hours and using 20% NHPI and 2%Cu(NO3)2with respect to the amount ofbenzyl phenyl etheras the catalyst.