吸附-放电等离子体分解去除NOx研究

采用吸附-放电等离子体分解工艺去除NO_x,考察吸附剂类型和放电方式以及循环操作对NO_x去除性能的影响.所考察的4种分子筛(ZSM-5、MOR、SAPO-34和SSZ-13)中SSZ-13具有较大的NO_x吸附容量和较低的吸附强度,有利于延长吸附时间并促进等离子体作用下NO_x的脱附和分解.程序升温脱附和红外光谱分析结果表明,NO_x主要以物理吸附或较弱化学吸附的形式吸附于SSZ-13表面,少量转化为NO₃^-和NO₂^-等强吸附物种.放电方式显著影响等离子体去除SSZ-13表面NO_x的性能,与N₂吹扫放电和封闭放电相比,采用先封闭放电后N₂吹扫放电的方式可同时获得较高的NO_x去除率和去除能效以及较低的NO_x残留率和N₂O选择性.吸附-等离子体分解循环操作时可获得稳定的NO_x去除性能,循环使用6次后SSZ-13晶相和孔结构无显著变化.

Removal of nitrogen oxides by adsorption-discharge plasma decompositionprocess

Effects of adsorbent type, operating conditions of discharge, and cyclic operation on the removal of NO_x in adsorption-discharge plasma decomposition process were investigated. Among the four kinds of zeolites (ZSM-5, MOR, SAPO-34 and SSZ-13) investigated, SSZ-13 showed the highest NO_x adsorption capacity and lowest adsorption strength, which were beneficial to prolong the adsorption period and promote the desorption and decomposition of NO_xby plasma. The results of temperature-programmed desorption and infrared spectroscopy showed that NO_x was mainly physically or weakly chemically adsorbed on the surface of SSZ-13, while a small amount of NO_x was converted into strongly adsorbed species such as NO₃^? and NO₂^?.The removal of NO_x adsorbed on SSZ-13 by plasma is significantly affected by the operating conditions of discharge. Compared with N₂-purge discharge and sealed-discharge, higher NO_x removal efficiency and energy efficiency, less residual NO_x on the adsorbent, and lower N₂O selectivity can be obtained simultaneously by using sealed-discharge first and thenN₂-purge discharge. The removal performance of NO_x can be maintained during cyclic operation of the adsorption-plasma decomposition process, without significant changes to the crystal and pore structures of SSZ-13 after six cycles.