A Theoretical Investigation of the Thermal Decomposition of Zinc Acetate and Zn-oxo Complex Based on the Pyrolysis Characteristics of the Zinc-containing Spent Catalyst

摘要

Zinc acetate and Zn-oxo complex of Zn_4O(CH_3COO)_6 containing in the spent catalyst of vinyl synthesis were investigated by means of the first principles of density functional (DFT) methods. The geometries, energies, charge populations and local electron density distributions of the two compounds and their formate analogues were analyzed. Based on the pyrolysis characteristics of the spent catalyst, the thermodynamic properties of AG, AH and AS for possible decomposition reactions of zinc acetate and Zn_4O(CH_3COO)_6 were calculated as functions of temperature. The results provide a theoretical evidence that Zn_4O(CH_3COO)_6 is more stable than zinc acetate due to the regular Zn_4O and ZnO_4 tetrahedral coordination between Zn atoms and two kinds of O atoms. The preparation of Zn_4O(CH_3COO)_6 via the hydrolysis of zinc acetate is thermodynamically feasible. Zn_4O(CH_3COO)_6 is further decomposed into ZnO via a decarboxylation reaction rather than a hydrolysis reaction.