在反应温度400~460℃、压力24MPa、停留时间30~200s,过氧量100%~500%的条件下,分析了对氯苯酚(4-CP)在等温立式柱塞流反应器中的超临界水氧化脱氯反应动力学及机理。首先得出温度为440℃、压力为24MPa、过氧量375%时,4-CP脱氯率可以达到80%的反应效果;过程显示,随着停留时间增大、温度提高,4-CP脱氯率提高,4-CP初始质量浓度和过氧量变化对过程无显著影响;动力学研究发现,4-CP的超临界水氧化技术(SCWO)反应动力学过程符合幂指数方程,通过参数拟合,求得4-CP反应级数为1,H2O2的反应级数为零,反应活化能为92.978KJ·mol-1,指前因子为104.6302,动力学方程能较好地预测实验结果;最后,通过GC/MS方法定性分析的反应中间产物为对苯二酚、邻苯二酚和对苯醌等,推测反应过程中伴随自由基参加的偶合反应占主导。研究结果证明了4-CP的超临界水氧化脱氯过程可行与高效,可望成为工艺应用的基础。
The supercritical water oxidation(SCWO) dechlorination kinetics and mechanism of p-chlorophenol(4-CP) was studied in an isothermal and vertical plug-flow reactor at 400-460 ℃,24 MPa,residence time of 30-200 s,and excess oxygen of 100%-500%.The results showed that the dechlorination rate of 4-CP could reached 80% at 440 ℃,24 MPa and excess H2O2 375%.The dechlorination rate increased with the increase in the temperature and residence time,while it did not obviously change by the initial concentration of 4-CP and excess H2O2.It was found that kinetics for dechlorination of 4-CP was described by a rate law involving first order reaction of 4-CP,zero order reaction of H2O2,92.978 KJ·mol-1 of activation energy,and 104.6302 of Arrhensius pre-exponential factors.The experimental results were forecasted well by the kinetics equation through repeated experiments.The results of GC/MS analysis showed that hydroquinone,catechol and benzene hydroquinone were the major intermediates and the reaction process included the coupling of free radicals.The research revealed the dechlorination process and mechanism of 4-CP in supercritical water and was expected to provide the basis for the engineering application of SCWO technology.