介质阻挡放电等离子体与吸附在CuZSM-5上的NO或NO/O2的相互作用

采用吸附和程序升温脱附(TPD)技术研究了介质阻挡放电等离子体对CuZSM-5催化剂上吸附的氮氧化物作用. 实验表明, 介质阻挡放电等离子体使催化剂表面吸附的NO及Cu活性位上吸附的NOx物种脱附, 并引发表面化学反应生成新的氮氧化物. 对于NO/N2体系, 介质阻挡放电等离子体与吸附在CuZSM-5上NO作用, 主要生成N2O和O2. 在富氧体系NO/O2/N2, 则生成较大量的N2O、NO2和NO. 等离子体预处理活性下降的CuZSM-5, 可明显提高其催化分解NO活性. 对比有或无介质阻挡放电等离子体预处理NO或NO/O2饱和吸附的CuZSM-5上的NO-TPD结果表明, 等离子体提高催化剂活性的原因与其使催化剂Cu活性位上吸附的NOx物种脱附有关.

Interactions of Dielectric Barrier Discharge Plasmas with NO or NO/O2 Adsorbed on CuZSM-5

In order to understand the synergistic effects between dielectric barrier discharge (DBD) plasmas and catalysts, the interactions between DBD and NO or NO/O2 saturated CuZSM-5 have been studied by adsorption and temperature programmed desorption (TPD) techniques. The results demonstrated that NO adsorbed on the CuZSM-5 surface and NOx species adsorbed on Cu active sites could be partly desorbed by DBD plasmas. Nitrogen oxides could be formed by plasma-induced surface reactions. A small amount of N2O and O2 could be formed in the NO/N2 system, and a significant amount of NOx (N2O, NO2, and NO) was generated in the NO/O2/N2 system by interactions between DBD plasmas and NO or NO/O2 adsorbed CuZSM-5. NOx removal over CuZSM-5 was tested by means of CuZSM-5 with or without plasma-pretreatment. After CuZSM-5, which had showed lower activity, was pretreated by N2 flow or DBD plasmas, NOx conversions in NO/N2 were 30.3% and 46.7%, respectively. The corresponding NOx conversion over fresh CuZSM-5 catalyst was 39.2%in NO/N2. A comparison of TPD profiles of NO and O2 over CuZSM-5 with or without plasma-pretreatment reveled that the key of the enhancement of NOx conversion on CuZSM-5 was the removal of NOx species present at Cu site by plasma-pretreating CuZSM-5.