甲苯裂解形成碳烟和PAHs的试验研究

Formation of Soot and PAHs in Pyrolysis of Toluene

基于流动反应器,开展了甲苯裂解过程碳烟颗粒及其前驱物多环芳烃(PAHs)的形成规律的试验研究.选取了在950~1450℃温度范围内3个不同停留时间(0.2s、0.5s、0.8s)下,甲苯裂解反应形成碳烟颗粒粒径分布特性,以及2~7环19种颗粒态PAHs的成分谱特征,进一步分析了不同裂解条件下颗粒物的当量毒性.发现甲苯裂解颗粒的生成过程伴随着凝结、凝并和团聚等气溶胶动力学变化,裂解温度越高碳烟颗粒的几何平均粒径越大、颗粒质量越高,颗粒粒径随停留时间增加向大粒子方向偏移;PAHs的浓度随温度的变化多数呈单峰分布,部分呈双峰分布,这与构成分子中的芳香环数和停留时间相关;0.5s颗粒中PAHs当量毒性高于0.8 s和0.2 s时,且峰值位于1050℃左右.

Based on a flow reactor,experiments were carried out on the formation of soot particles and their pre-cursor polycyclic aromatic hydrocarbons(PAHs)in the pyrolysis of toluene.The toluene underwent oxygen-free pyrolysis within the temperature range of 950—1450℃at three different residence times,i.e.,0.2 s,0.5 s and 0.8 s.The particle size distribution and particle-bound PAHs(2—7 rings)from the toluene pyrolysis were measured.The equivalent toxicity of particle-bound PAHs was also studied.The result shows that the formation of soot particles is accompanied by aerosol kinetic changes such as condensation,coagulation and agglomeration,increase in pyrolysis temperature leads to increased geometric mean size and mass of soot particle,and particle size shifts toward larger diameter with increasing residence time.The concentration of PAHs changes with tempera-ture,most of them are of unimodal distributions and a few have a bimodal distribution,which is related to the number of aromatic rings and the length of residence time.The equivalent toxicity of particle-bound PAHs at 0.5s residence time is higher than that at 0.8 s and 0.2s,which reaches the peak at around 1050℃.