氧化锌催化二苯甲烷二氨基甲酸甲酯分解反应

Catalytic Decomposition of Methylene Di(Phenylene Carbamate) by ZnO

对氧化锌催化二苯甲烷二氨基甲酸甲酯(MDC)分解制二苯甲烷二异氰酸酯(MDI)反应进行了研究,考察了反应温度、反应时间、催化剂用量以及原料浓度等对反应的影响. 结果表明,适宜的反应条件为催化剂用量2.1%, MDC浓度3.5%, 反应温度260 ℃, 反应时间20～30 min, 此时MDC转化率为99.5%, MDI产率为40.0%, 碳化二亚胺改性二苯甲烷二异氰酸酯(C-MDI)的产率为49.7%. 进一步研究发现,15%的醋酸锌溶液经草酸铵沉淀(不陈化)后,在500 ℃下焙烧4 h得到六方相的氧化锌,晶体的平均粒径为100～200 nm, 以其为催化剂时MDC转化率为99.1%, MDI的产率为52.1%, 同时还得到27.7%的 C-MDI.

The synthesis of methylene di（phenylene isocyanate） （MDI） from methylene di（phenylene carbamate） （MDC） over zinc oxide was studied. The influences of reaction conditions were investigated. Under the normal pressure, the optimum conditions were 2.1% catalyst, 3.5 % MDC, reaction temperature 260℃ and reaction time 20-30 min. As a result, the conversion of MDC was 99.5 %, the yield of MDI was 40.0 % and the yield of carbodiazide MDI （C-MDI） was 49.7 %. Furthermore, the zinc oxalate obtained by the precipitation reaction of 1596 zinc acetate and ammonium oxalate was calcinated at 500℃ for 4 h to get ZnO, which is 100- 200 nm in diameter and has fine dispersion. The conversion of MDC was 99.1%, the yield of MDI was 52.1% and the yield of C-MDI was 27.7 % for the decomposition reaction over this ZnO.