铜铈复合氧化物上石化行业典型VOCs的氧化行为与动力学

采用共沉淀法和等体积浸渍法制备了CuCeO x复合催化剂,对材料的物化性质进行了XRD、低温N2吸脱附、H2-TPR和O2-TPD表征.以石化行业典型VOCs(苯、甲苯和正己烷)为探针污染物,研究了污染物组成与浓度、反应空速、O2浓度、H2O浓度和催化剂种类对其氧化行为的影响,并对反应动力学参数进行了模型拟合.共沉淀得到的催化剂具有均匀的活性相、好的低温可还原性能和较多的活性表面氧物种.甲苯氧化率随着污染物浓度升高而降低,高转化率下苯浓度与其氧化率无相关性,正己烷的氧化率与入口浓度呈正比.苯能够显著抑制甲苯的氧化,而甲苯加入有利于苯的氧化.正己烷对苯氧化的影响较小,但能够促进甲苯的转化,苯系物对正己烷氧化有明显的抑制作用.低空速和高氧浓度都有利于污染物的氧化,氧浓度的变化对正己烷和苯的氧化影响较小.水汽对甲苯的氧化有明显的抑制作用,而对苯和正己烷氧化有明显的促进作用.共沉淀催化剂具有更好的甲苯和苯氧化性能,而无水条件下浸渍催化剂具有更好的正己烷氧化性能.拟一级动力学模型能够很好地模拟不同条件下污染物的氧化行为.

Oxidation Behavior and Kinetics of Representative VOCs Emitted from Petrochemical Industry over CuCeOx Composite Oxides

CuCeO_x composite catalysts were synthesized via coprecipitation (COP-CuCeO_x) and incipient impregnation (IMP-CuCeO_x) methods, respectively. The physicochemical properties of the samples were characterized by XRD, low-temperature N₂ sorption, H₂-TPR and O₂-TPD. The influences of reactant composition and concentration, reaction space velocity, O₂ content, H₂O concentration, and catalyst type on the oxidation behaviors of benzene, toluene, and n-hexane emitted from petrochemical industry were systematically investigated. In addition, the related kinetic parameters were model fitted. Compared with IMP-CuCeO_x, COP-CuCeO_x had well-dispersed active phase, better low-temperature reducibility, and more active surface oxygen species. The increase of reactant concentration was unfavorable for toluene oxidation, while the opposite phenomenon could be observed in n-hexane oxidation. The inlet concentration of benzene was irrelevant to its conversion under high oxidation rate. The introduction of benzene obviously inhibited the oxidation of toluene and n-hexane, while the presence of toluene had a positive effect on benzene conversion. The presence of n-hexane could promote the oxidation of toluene, while toluene had a negative influence on n-hexane oxidation. Both low space velocity and high oxygen concentration were beneficial for the oxidation process, and the variation of oxygen content had negligible effect on n-hexane and benzene oxidation. The presence of H₂O noticeably inhibited the oxidation of toluene, while significantly accelerated the oxidation procedure of benzene and n-hexane. COP-CuCeO_x had superior catalytic performance for toluene and benzene oxidation, while IMP-CuCeO_x showed higher n-hexane oxidation activity under dry condition. The oxidation behaviors under different conditions could be well fitted and predicted by the pseudo first-order kinetic model.