【作者】 杜传梅；

【导师】 张明旭；

【作者基本信息】 安徽理工大学 ， 环境工程， 2014， 博士

【摘要】 煤中硫在煤的利用过程中起着不容忽视的作用。量子化学计算方法在煤化学中的应用,已逐步深入到探索煤的结构与反应性之间的关系,逐渐形成了一个新的研究方向。以山西新峪精煤为研究用煤,利用全组分分离实验测定有机硫赋存规律与分布：(1)新峪精煤以有机硫为主,其含量占总硫的83%以上,其中90%左右的有机硫分布于大分子结构的萃余煤中,而轻质组分则几乎不含有机硫。(2)有机硫在各族组分中的相对含量按沥青质组分>精煤组分>萃余煤组分>轻质组分的规律降低。对煤样XPS峰进行了归属及得到了煤中有机硫相对含量,得到了如下结论：煤中有机硫的三种主要赋存形态的相对含量从高到低依次是硫醇(醚)、噻吩、(亚)砜。通过煤全组分分离实验可得到新峪精煤及各族组分中GC/MS可检测含硫小分子化合物共有八种,其中噻吩类硫五种,硫醇醚类硫三种。运用Materials Studio6.0计算软件对新峪精煤中二苯并噻吩、三-甲基-二苯并噻吩等八种含硫模型化合物及新峪精煤局部的模型进行了构建及优化计算。讨论了最高占据轨道和最低未占据轨道的组成与化合物活性的关系,对于二苯并噻吩,最高已占分子轨道主要分布在S7,C3,C5,C9,C11,C12,C2,C13上,对于新峪精煤中八种含硫模型化合物,最高已占分子轨道或最低未占分子轨道主要分布在S上,说明硫原子是亲核活性点或是亲电活性点,这些是影响化合物活性的主要基团。从电荷分析可知,含硫模型化合物的负电荷主要分布在分子中的硫原子上,说明含硫模型化合物中的S原子可能是受亲电试剂进攻的可能性作用点,这就可以预测,在形成配合物时,此原子优先配位。新峪精煤局部的模型结构中在交联程度较高区域的C-S单键是键的强度比较弱的地方,这些键在煤的降解过程中比较容易发生断裂,活性比较高。通过理论计算研究了外电场作用下含硫模型化合物分子的基态性质变化,如分子几何构型、能量、偶极矩、电子转移及热力学性质变化等。当加入外加电场时,分子的活性增强,分子越来越不稳定。另外,随着外电场的加入,分子中各基团的谐振频率向低频移动。温度在300K-800K之间变化时,二苯并噻吩分子总能、结合能、分子体系最高占据轨道(HOMO)能级EH,最低未占据轨道(LUMO)能级EL、能隙EG、总势能、自旋极化能随着温度的变化而变化的很小。分子的极性大小和微波脱硫的难易程度相对应。对比了噻吩类、硫醇醚类和相应类似分子在外加能量场作用下的分子的变化情况。含有S、O、N原子的极性分子对外电场的加入是有响应的,而只有C、H原子构成的1,2-二苯乙烷分子对外加电场没有反应。并且从分子的电偶极矩随外加电场变化的理论计算和微波脱硫的实验结果对比也可得到这个结论；外加电场可以改变含硫模型化合物中硫原子的振动能及分子的零点振动能,并且对分子中各基团的振动光谱强度和振动频率都有影响。开展外电场作用下煤中含硫模型化合物特性和硫降解过程的研究,可以为煤在外加能量场(微波)作用下的结构与反应性研究提供可靠的理论基础。比较噻吩在有无外电场作用下降解生成H2S的路径的分析可得：在有无电场作用下有相同的降解路径,但降解过程中各中间体及过渡态的结构及性能都发生了变化,从噻吩降解的势能剖面图可知,各路径发生的难易程度是不同的。当外加电场为0.001au时,只有第一条路径,在某处过程优化结构找不到说明第二条路径便不可能存在了。因而从理论上说明微波对噻吩的降解生成H2S途径及途径中各中间体和过渡态的性能都会有作用。随着外加电场的加入,二甲基二硫醚和二苯并噻吩的裂解活化能降低,从理论上说明,微波除了具有热效应外,还存在一种不是由温度引起的非热效应。微波作用下的有机反应,改变了反应动力学,降低了反应活化能。从能量机制上说明为什么在新峪精煤微波脱硫实验中,硫醇硫醚类脱除效果比较好,而对于噻吩硫却效果不佳。更多还原

【Abstract】 The sulfur in coal have great influence on coal utilization. The quantum chemistry calculation method has been gradually used to study the correlation between coal structure and reactivity in coal chemistry, and has been gradually formed a new research direction.Taking XingYu clean coal from Shanxi as the research object, we determine the occurrence and distribution of organic sulfur using the whole group separation experiment.(1)The main sulfur in XingYu clean coal is organic sulfur, the organic sulfur content accounts for more than83%, about90%of organic sulfur distribute in residue coal of the macromolecular structure, and lightweight components contain almost no organic sulfur.(2)The relative contents of organic sulfur in all groups decrease according to asphaltene component>refined coal groups>residue coal component>light components.The coal XPS peaks were assigned and we get the relative content of organic sulfur in coal, the conclusions are as follow: the relative content of three kinds of main forms of organic sulfur in coal from high to low is athiol(ether),thiophene,(sub)sulfone. It can get eight small molecular compounds in XingYu clean coal and the total coal components detected by GC/MS through the total groups separation experiments. It contains five kinds thiophene sulfur and three kinds mercaptan sulfur ether.We build the new partial model and carry out the optimization calculation of the eight sulfur model compounds (Dibenxothiophene,3-methyl-dibenzothiophene et al)and XingYu coal. The relationship between the highest occupied orbital and the lowest unoccupied orbital of the activity of compounds are discussed. For dibenzothiophene, the highest occupied molecular orbitals are mainly distributed on S7,C3,C5,C9,C11,C12,C2,C13; For the eight model sulfur compounds in Xingyu clean coal, the highest occupied molecular orbitals and the lowest unoccupied molecular orbitals are mainly distributed on S, it illustrates that the sulfur atom is electrophilic activity or nucleophilic activity, these are the main groups which influence the compounds activity. It shows that the negative charge of the model sulfur compounds mainly distributed on the sulfur atoms through the charge population analysis, and illustrate that the sulfur atom in sulfur model compounds may be the possibility offensive point affected by the electrophilic reagents. It can predict that the atom prefer to coordinate in the formation of complexes. The bond strength of C-S single bond in the region of the crosslinking degree in XingYu coal is little weak, these bond are more easy to break during the coal fracturing, and the activity is higher.The ground state properties of the sulfur model compounds under the external electric fields are studied through the theoretical calculation, such as molecular equilibrium geometries, energy, dipole moment, electron transferring and the change of thermodynamic properties. When the external electric field is applied, the molecular activity is enhanced and the molecules are more and more unstable. In addition, with the external electric field, the resonant frequency of groups in molecule changed and moved to the low frequency. When temperature change in the range of300K-800K, the total energy, binding energy, the energy of the highest occupied molecular orbital(HOMO), the energy of the lowest unoccupied molecular orbital(LUMO), the energy gap, the total potential energy, spin polarization energy change with the temperature slightly. The degree of difficulty and easy of microwave desulfurization have certain relation with the large and small of the molecular polarity. The change of thiophene, thiol ether and similar molecular under the external energy field are compared. The polar molecules containing S,O,N are sensitive to the external electric field, and1,2dibenzene ethane molecules only constituting with C,H atom has no reaction to the external electric field. And it can get the conclusion from the theoretical calculation of the molecular electric dipole moment changing with the external electric field and comparison of experimental results of microwave desulfurization.Studying on the character of the sulfur model compounds in coal and the process of the sulfur degradation, it can provide reliable theoretical basis for researching on the structure and reactivity of coal under the function of the external electric field. Comparing with the path analysis of degrading to being H2S under the external electric field0.0005au and without the external electric field, it can get that there have the same degradation path with or without the external electric field, but the structure and performance of all the intermediates and transition states in degradation process have changed. The degree of difficulty of each path are different from the potential energy profile of the thiophene degradation. When the external electric field is0.001au, there only have the first path, the second path might not exist when the optimization structure was not found in somewhere progress. It illustrate indirectly from the theory that the microwave have effect on the path of generating H2S, the intermediates and transition states through pyrolysis. The activation energy of Dimethyl disulfide and Dibenzothiophene through pyrolysis is reduced with the increase of the external electric field. It illustrate that the microwave not only have the heating effect but also have non-thermal effect which is not caused by temperature in theory. The organic reactions under the action of microwave changed the reaction kinetics and reduced the reaction activation energy.It can explain from energy mechanism why the removal effect is better for the mercaptan sulfur and is poor effect for the thiophenic sulfur in the microwave desulfurization experiment of XingYu clean coal.更多还原