Preparation Of Zinc Oxyacetate And Its Application In Dimethyl Carbonate Aminolysis Reaction And Nano-ZnO Preparation

Zn₄O?OAc?₆,a multinuclear complex,can be used as catalyst,an additive for lubrication oils and a luminescent material.There are disadvantages associated with the reported preparation methods for Zn₄O?OAc?₆,including complexity,severe operating conditions,and environmental concerns.In this study,a facile and green method for Zn₄O?OAc?₆ preparation is proposed and its application in dimethyl carbonate?DMC?aminolysis reaction and nano ZnO preparation were studied.Zn₄O?OAc?₆ can be prepared using Zn?OAc?₂ and DMC as raw materials under mild reaction conditions.And the product was characterized by FTIR,XRD,¹³C NMR,¹H NMR,TG and elemental analyses.The effects of reaction conditions on Zn₄O?OAc?₆ preparation was investigated.At a 0.004:1 molar ratio of Zn?OAc?₂ to DMC?water contents 0.086%?and a reaction time of 1 h at 130?,Zn₄O?OAc?₆ yield was 95.2%.The H₂O content of DMC has an important effect on Zn₄O?OAc?₆ formation.When the H₂O content was greater than 0.086%,the product purity decreased.Moreover,during the reaction of DMC with Zn?OAc?₂,DMC readily hydrolyzed to form CO₂ and methanol in presence of H₂O.Then,the generated methanol reacted with Zn?OAc?₂ to produce Zn₄O?OAc?₆.In contrast,when Zn?OAc?₂ directly reacted with methanol,the high concentration methanol converted Zn?OAc?₂ into Zn₅?OH?₈?OAc?₂·2H₂O?LHZA?and then into ZnO.The catalytic performance of Zn₄O?OAc?₆ in methyl N-phenyl carbamate?MPC?synthesis was investigated.At a 0.28:1 mass ratio of Zn₄O?OAc?₆ to aniline,a 1:20 molar ratio of aniline to DMC and a reaction time of 3 h at 130?,aniline conversion and MPC yield was 99.8%and 97.6%,respectively.An induction period was found during synthesis of MPC and methylene diphenyl-4,4?-dicarbamate?MDC?,and it was more evident in the case of MDC.The cause for the induction period was the existence of heterogeneous Zn?OAc?₂ at the start of the reaction.The induction period can be shortened to some extent with increasing the reaction temperature or DMC amount,and the effect of reaction temperature was more obvious.During Zn?OAc?₂ catalyzed DMC aminolysis reaction,two catalytic active center existed,Zn?OAc?₂ and Zn₄O?OAc?₆.As for MDC synthesis,Zn₄O?OAc?₆ plays the important role.However,Zn?OAc?₂ plays the leading role in MPC synthesis.Using Zn₄O?OAc?₆ as a zinc source,the preparation of nano-ZnO by hydrothermal method was preliminarily investigated.The nano-ZnO rods,with uniform morphology and a aspect ratio of 23:1,could be prepared at 200?for 24h without addition of acid or base and surface active agent.