The Catalytic Properties Of Cobalt Carbonyl Complexes In Carbonylation Synthesis Of Malonic Ester

Malonic ester is an important organic chemical intermediates. It can be alkylation, amine alkylation and other substitution reactions, because of its active methylene group, that is easy to be replaced by other groups. The current method to synthesize malonic ester is sodium cyanide method, in which there was complex process, pollution of the environment and some other drawbacks. Therefore, the research of environment-friendly green synthetic process, and easy separation of recyclable catalytic system, has important practical and theoretical significance.We studied the green synthesizing technology of malonic ester in catalytic carbonylation, and investigate the effects of the temperature, pressure, feed means and the types of bases on the carbonylation reaction. Besides, we established the methods of analysis, separation and purification of malonic ester. The results show that [Co(CO)₄]^- performed the best catalytic activity, when Zn powder was used as a reducing agent, Na₂SO₃ as an auxiliary agent, and CoCl₂, Na₂SO₃, Zn with the molar ratio of 1:1:1.33 in the synthesis of [Co(CO)₄]^-, the conversion of chloroacetate was 99.5%, the yield of malonic ester was 94%.In addition, we also synthesized different types of [Co(CO)₄]^-/ IL catalysts by ion exchange in situ, and the catalytic properties were evaluated in the carbonylation synthesis of dimethyl malonate. The results showed that [Bmim][Co(CO)4] was the best catalyst. Under the reaction conditions: PCO=2.0 MPa, T=85℃, t=3 hrs, the average conversion of chloroactic acid, the yield of malonic ester were 95% and 92.4% for [Bmim][Co(CO)4] catalyst after recycling four times.Besides, the technics separation and purification of malonic ester were studied. The experimental results showed that the purity of malonic ester could be 99% and recovery could be 98% at an optimized condition: the temperature of distillation was 125℃to eliminate alcohol, and the product was extracted with toluene, eliminated benzene by distillation at 155℃, then vacuum distillation at 125℃.