以1,2-二苯乙烷为模型分子,考察了N-羟基邻苯二甲酰亚胺(NHPI)对分子氧氧化断裂木质素分子中C—C键的催化作用,比较了Cu、Co和Mn的多种可溶性盐对NHPI催化活性的促进作用,探究了工艺条件对1,2-二苯乙烷氧化的影响规律.结果表明:NHPI能够在温和条件下催化分子氧氧化1,2-二苯乙烷中的C—C键断裂生成苯甲醛和苯甲酸.可溶性的Cu、Co和Mn盐都具有助催化作用,其中乙酸锰的助催化作用最强.确定了二苯基乙酮为氧化的初级反应产物.发现提高反应温度、增加乙酸锰用量以及延长反应时间,有利于C—C键的氧化断裂和提高小分子产物的选择性.优化的反应条件为NHPI为底物物质的量的10%,乙酸锰和NHPI之比为1:10,反应温度90℃,氧气分压1.0 MPa,反应时间8 h,C—C键的氧化断裂产物苯甲醛和苯甲酸的总选择性可达76.5%.%The catalytic effects ofN-hydroxyl phthalimide combined with various transition metal salts on the oxidative breakage of C—C bond of lignin by O2 under mild conditions were studied. 1,2-diphenylethane was adopted as the model compound of lignin C—C bond. It was found that Mn(OAc)2 showed the highest promotion effect on the catalytic activity of NHPI among the soluble cobaltous, manganous and cupric salts. The oxidative breakage of C—C bonds led to the production of benzyl aldehyde and benzoic acid with high selectivity. 1,2-Diphenyl ethanone was found to be the primary product. Either increase the reaction temperature, Mn(OAc)2 amount as well as the reaction time favored the C—C bond cleavage. Total selectivity of benzyl aldehyde and benzoic acid up to76.5% was achieved in acetic acid under the conditions of 90℃ and 1.0 MPa O2 for 8 h by using 10% NHPI and 1% Mn(OAc)2 with respect to the amount of benzyl phenyl ether as the catalyst.
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