ReaxFF方法研究的褐煤热解过程中硫的迁移机理

SULFUR TRANSFER MECHANISM IN LIGNITE PYROLYSIS PROCESS BY REAXFF MOLECULAR DYNAMICS SIMULATION

采用ReaxFF(reactive force field,活性反应力场)分子动力学方法模拟了褐煤在1000K^2 000K下的热解过程,分析了热解温度对热解产物分布的影响,搜寻到了噻吩、硫酚和硫醚中硫元素迁移的基元反应以及热解产物中硫原子的存在形式.结果表明,热解温度是影响热解产物中硫元素分布的一个重要因素,高温会抑制硫从褐煤中逸出.在热解过程中,噻吩、硫酚和硫醚中的硫原子会通过硫自由基中间体进行相互转化.在热解结束时大多数硫原子以噻吩和硫醚的形式存在.

The pyrolysis processes of lignite at 1 000K-2 000 K were studied using ReaxFF molecular dynamics simulations.The effects of temperature on the product distributions were analyzed.The elementary reactions of sulfur transfer in thiophene,thiophenol and thioether structures,as well as the sulfur forms existed in pyrolysis products were searched.It was determined that the sulfur atom compositions in pyrolysis products were dependent on temperature.At high temperatures,escaping of sulfur atoms from lignite was inhibited.In the pyrolysis process,sulfur atoms in thiophene,thiophenol and thioether structures transferred to each other by the reactive intermediates of sulfur radicals.Most of sulfur atoms existed in thiophene and thioether forms in the final products of pyrolysis.