氧化铝真空碳热还原氯化歧化过程中二氯化铝行为研究

Behavior of AlCl_2 in Carbothermic-Chlorination-Disproportionation of Alumina in Vacuum

对氧化铝真空碳热还原氯化歧化过程中AlCl_2的相关反应进行热力学计算,结果表明在1760 K,60 Pa的条件下,Al_2O与C、Al_4C_3与Al_2O_3、Al_4O_4C与C均可发生氯化反应,AlCl_2的歧化反应在冷凝区也可以进行。采用基于密度泛函(DFT)框架下的第一性原理平面波赝势法,并用从头算分子动力学的方法对Al_2O与C的氯化反应和AlCl_2的歧化反应进行了结构优化和动力学模拟。结果表明碳热还原-氯化-歧化过程中的确有AlCl_2生成,吸附态的AlCl_2将进一步与Al_2O和C反应生成吸附态的AlCl分子,在C和AlCl_3(或AlCl_2)存在的条件下,Al_2O气体具有氯化活性,自由态的AlCl_2将在冷凝区歧解为AlCl分子。

Abstract The havior of AlCl2 in carbothennic-chlorination-disproportionation of Al2O in vacuum was theoretically analyzed. First,the impact of the reaction conditions on the chlorination was modeled and calculated with software HSC Chemistry 6.0 and Material Studio. The calculated results show that the chlorination of the reactants, including Al2O and C, Al4C3 and Al2O3,Al4O4C and C,is possible at 1760 K and 60 Pa, and that the disproportionation of AlCl2 occurs in the upper condensation-zone of the furnace.Next, the disproportionation of AlCl2 and the chlorination of Al2O and C were dy- namically simulated,by the first-principles calculation of plane-wave pseudo-potential technology based on density func- tion theory （DFT） and in ab initio molecular dynamics method, to optimize the atomic structures. The simulated results show that AlCl2 does form in carbothermic-chlon＇nation-disproportionation of Al2O in vacuum. The AlCl, produced by the reaction of C and adsorbed AlCl2, remains to be adsorbed on C-surfaces;and the gaseous Al2O is active in the presence of C and AlC13（or AlCl2）. Besides,AlCl2 vapor in the condensation zone could be disproportionated into gaseous AlCl.