超临界水中醋酸锌水解反应的分子动力学模拟.pdf

物理化学学报( li Huaxue Xuebao)
anuary
cta Phys. -Chim. Sin. 2013, 29(1), 23-29
Article
doi:10.3866/PKU.WHXB201210123
www.whxb.pku.edu.cn
超临界水中醋酸锌水解反应的分子动力学模拟
王晓娟李志义刘志军
(大连理工大学化工机械学院,流体与粉体工程设计研究所,辽宁大连116023
摘要:氧化锌(ZnO)是一种重要的化工原料,超临界水热合成法制备纳米ZnO的第一步是锌盐与碱或水发生
水解反应生成Zn(OH)2后者接着脱水生成ZnO.以Zn( Cha COO)为原料,直接和超临界水(SCW)反应能够制
备纳米级的ZnO颗粒,但对反应机理的探讨较少.本研究利用分子动力学模拟超临界条件下Zn( CHA Coo)水
解反应过程中的结构和能量变化,发现Zn(CH.COO)》在SCW中容易聚集成无定形的团簇,1个Zn2平均和5
个 CH Coo和1个H2O配位,形成6配位的八面体结构.处于Zn( CHA coo)2团簇和SCW界面的Z“能够和更
多的H2O配位.水解反应后系统的势能降低,同时伴随Zn( CH: Coo)2团簇结构的改变,反应产物OH分布在
Zn( CHCOO)2团簇内部,富集Zn2,而 CHI COOH则分布在SCW中.本文的工作为超临界水热合成的反应过程
提供了基本的理论依据
关键词:氧化锌;醋酸锌;超临界;水热合成;水解反应;分子动力学模拟
中图分类号:O645
Molecular Dynamics Simulations on Hydrolysis of Zinc Acetate in
Supercritical Water
WANG Xiao-juan LI Zhi-yi LU Zhi-jun
(nstitute offluid and Powder Engineering, College of Chemical Machinery, Dalian University of Technology Dalian 116023,
Liaoning Province, P R. China)
Abstract: Zinc oxide(Zn )is a multifunctional material with wide applications in chemical engineering
Hydrothermal synthesis of Zno under supercritical conditions from salt solutions containing zinc ions is an
environmentally safe process. Two reaction steps are involved, zinc hydroxide sol formation and dehydration
from the sol. However, little is known about the underlying mechanism. In this study, molecular dynamics
simulations were performed to investigate the structural and thermodynamic changes in the zinc acetate
hydrolysis process i., Zn(CH O in surital water()Our esults show that Zn(CHC0) is
prone to aggregate in SCW. On average, one Zn""ion coordinates with five CHACOO species and one Ho
molecule, forming an cheral configuration. However, more water molecules bind Zn? at the SCW
interface to form Zn(CH/COO) clusters. The total potential energy of each system decreases after the
hydrolysis of Z (H uggesting that it is a thermally favorable process in SCW. The OH reaction
product incorporates into the amorphous Zn(CH OO) cluster and Cha COOH is in the SCW phase. Our
results provide a general theoretical framework for the Zn(CH COO) hydrothermal synthesis in SCW
Key Words: Zinc oxide Zinc acetate; upercritical water Hydrothermal synthesis; Hydrolysis
Molecular dynamics simulation
Received: August, 2012; Revised: October 1, 2012; Published on Web: October 12, 2012
Correspondingauthor.Email:liuzi(@lut.edu.cn;Tel:+-86-411-84986285
The project was supported by the Fundamental Research Funds for the Central Universities, China(852001
中央高校基本科研业务费专项资金(852001)资助项目
C Editorial office of Acta Physico-chimica Sinica