煤中脂肪族硫醚结构氧化过程机理

应用Gaussian 03程序,采用密度泛函(DFT)方法,在B3LYP/6-31G(d,p)水平下研究煤中脂肪族硫醚结构(C_6H_5CH_2SCH_3)吸附O_2分子及氧化反应过程的能量变化,确定分子间氧化反应机制,为预防煤炭自燃奠定理论基础。由计算结果可知,煤中C_6H_5CH_2SCH_3结构物理吸附O_2分子形成复合物Ⅰ,形成过程是一个无势垒的过程,在热力学上是稳定的。煤中C_6H_5CH_2SCH_3结构与O2分子的相互作用距离dS-O为2.582A,经CP校正后的相互作用能为-20.60kJ/mol。分析复合物Ⅰ的电子密度变化,可确定其相互作用为范德华力,属于物理吸附。当复合物Ⅰ吸收足够的能量,将进一步发生化学反应。煤中C_6H_5CH_2SCH_3结构氧化反应共有5条反应路径,Path 4是反应的主反应路径,其产物P_3(C_6H_5CH_2SOH+CH_2O)是反应的主产物。经分析发现:煤中C_6H_5CH_2SCH_3结构易发生初步氧化,仅需12.36kJ/mol的能量,物理吸附一个O2分子释放的能量足以提供,但若要深度氧化将Path 4进行下去,需要再从外界吸收相当于物理吸附5个O_2分子释放的能量。

Mechanism of the oxidation process of the aliphatic sulfoether structure in coal

The energy change generated from aliphatic sulfoether structure (C6H5CH2SCH3) in coal adsorbing O2 and oxidation was studied by using Gaussian 03 program and density functional theory (DFT) method at the B3LYP/6-31G (d,p) level,and the oxidation mechanism was analyzed to provide theoretical basis for preventing coal spontaneous combustion.The results show that the energy of complex Ⅰ formed from C6H5CH2SCH3 structure in coal adsorbing O2 is the local least,and the formation is a stable no barrier process in thermodynamics.The interaction distance dS-O between C6H5CH2SCH3 structure in coal and O2 is 2.582 (A),and the interaction energy is-20.60 kJ/mol after CP correction.Analyzing the electron density change of complex Ⅰ shows the interaction is Van der Waals forces,which belongs to physical adsorption.The complex Ⅰ will react when it absorbs enough energy.There are five reaction paths in oxidation reaction of C6H5CH2SCH3 structures in coal,Path 4 is the main reaction path,and P3(C6H5CH2SOH+CH2O) is its principal product.The analysis shows that C6H5CH2SCH3 structure in coal is easy to be preliminarily oxidized,only 12.36 kJ/mol energy is needed and the energy of physically absorbing an O2 molecule is enough.But deep oxidation along with Path 4 needs as much as the energy of physically adsorbing 5 O2 molecules.