Experimental and Theoretical Study of Hydrogen Thiocarbonate for Heterogeneous Reaction of Carbonyl Sulfide on Magnesium Oxide
Experimental and Theoretical Study of Hydrogen Thiocarbonate for Heterogeneous Reaction of Carbonyl Sulfide on Magnesium Oxide
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硫代碳酸氢盐在氧化镁上硫化羰多相反应的实验与理论研究
DOI：
10.1021/jp809887c
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发表时间：
2009-04-09
影响因子：
2.9
通讯作者：
He, Hong
中科院分区：
文献类型：
--
作者：
Liu, Yongchun;He, Hong
采用原位漫反射红外傅里叶变换光谱结合导数光谱分析、二维相关光谱分析和量子化学计算，研究了硫代碳酸氢盐在氧化镁上的红外吸光度归属和分子结构。 COS在MgO上的非均相反应实验中观察到了1283和1257 cm(-1)处的谱带，具有典型的中间体特征。通过二维相关光谱分析和量子化学计算，将1283 cm(-1)处的谱带归属于MgO晶体(100)面上两个相邻Mg原子上形成的桥联硫代碳酸盐的upsilon能带，1257 cm(-1)处的谱带为MgO上单齿硫代碳酸盐的upsilon能带。由于硫代碳酸盐的吸光度较弱且表面碳酸盐的中断，实验中看不见硫代碳酸盐的upsilon(as)(OCO)带。提出了硫代碳酸盐的形成机理，该机制是通过表面-OH基团对预吸附COS的亲核攻击，然后氢原子从-OH基团转移到预吸附COS的硫原子上而发生的。在B3LYP/6-31 +G(d,p)理论水平上，计算出桥联硫代碳酸盐分子内质子转移反应的活化能为18.52 kcal.mol(-1)。
In situ diffuse reflectance infrared Fourier transform spectroscopy combined with derivative spectroscopy analysis, two-dimensional correlation spectroscopy analysis, and quantum chemical calculations were used to investigate the infrared absorbance assignment and the molecular structure of hydrogen thiocarbonate on magnesium oxide. The bands at 1283 and 1257 cm(-1), which had the typical characteristic of intermediate, were observed in experiments for the heterogeneous reaction of COS on MgO. On the basis of two-dimensional correlation spectroscopy analysis and quantum chemical calculations, the band at 1283 cm(-1) was assigned to the upsilon(s) band of bridged thiocarbonate which formed on the two neighboring Mg atoms in the (100) face of MgO crystal, and the band at 1257 cm(-1) was the upsilon(s) band of monodentate thiocarbonate on MgO. The upsilon(as)(OCO) band of thiocarbonates was invisible in the experiment due to their weak absorbance and the interruption of surface carbonate. The formation mechanism of thiocarbonates is proposed, which occurred through a nucleophilic attack of preadsorbed COS by surface -OH groups followed by hydrogen atom transfer from the -OH group to the sulfur atom of preadsorbed COS. The activation energy for the intramolecular proton-transfer reaction of bridged thiocarbonate was calculated to be 18.52 kcal.mol(-1) at the B3LYP/6-31 +G(d,p) level of theory.