基于调控存储位点实现甲苯的“存储-原位氧化”循环净化  

Toluene removal through“storage-in situ oxidation”cycling via modulating the storage sites

作　　者：张岚岚 郝泽龙 刘丹宇 石川[1] 陈冰冰[1] ZHANG Lanlan;HAO Zelong;LIU Danyu;SHI Chuan;CHEN Bingbing(State Key Laboratory of Fine Chemicals,School of Chemistry,Dalian University of Technology,Dalian 116024,China)

机构地区：[1]大连理工大学化学学院,精细化工国家重点实验室,大连116024

出　　处：《环境工程学报》2023年第11期3706-3711,共6页Chinese Journal of Environmental Engineering

基　　金：国家自然科学基金资助项目(22276023,21932002);国家重点研发计划项目(2021YFA1501102,2017YFA0700103);中央高校基本科研业务费专项基金项目(DUT22ZD212,DUT22LAB602,DUT22QN207);辽宁省“兴辽计划”项目(XLYC2008032)。

摘　　要：“存储-原位氧化”循环净化气态污染物(VOCs)的方法是利用存储材料对VOCs的选择吸附,在室温先将VOCs富集并存储在催化剂上。当存储饱和后,通过升温使催化剂催化氧化活性提高,短时间内将存储的VOCs完全氧化为CO_(2)和H_(2)O,使得催化剂得以原位氧化再生。选择分子筛材料用于“存储-原位氧化”循环净化甲苯的关键问题是:大部分的甲苯以物理吸附的形式存储于分子筛催化剂的孔道中,脱附温度低,导致原位催化氧化过程中甲苯未被氧化前就脱附逃逸,造成二次污染。以不同银负载量的Ag_(x)/β-25催化剂作为研究对象,利用XRD和UV-vis对分子筛催化剂表面Ag物种的存在状态进行识别。将Ag物种状态与甲苯程序升温脱附结果定性关联,明确了甲苯在不同状态的Ag物种上的存储强弱。位于离子交换位上的Ag^(+)与甲苯键合最强,其次为Ag_(n)^(δ+)团簇,键合最弱的为金属银粒子。通过控制存储时间,可调控甲苯在Ag_(x)/β-25催化剂上的存储位点,使甲苯优先选择吸附在位于离子交换位上的Ag^(+)或Ag_(n)^(δ+)团簇上,当脱附温度高于氧化温度,即可实现低浓度甲苯的“存储-原位氧化”循环再生净化。通过该研究,可初步得出调控分子筛表面存储位点强弱的方法,并构建适宜的催化剂,为指导设计低浓度甲苯脱除的双功能催化材料提供参考。“Storage-in situ oxidation”cycling process includes storing low concentration of volatile organic chemicals(VOCs)on the catalyst at room temperature and complete oxidation the stored species into CO_(2)and H_(2O)at elevated temperature in a short time,and the catalyst can be oxidized and regenerated in situ.The key issue for application of this approach over zeolite materials is in situ regeneration of the zeolite materials without any release of the toluene or generation of secondary pollutants.Therefore,in this study,a series of Ag_x/β-25catalysts were prepared and the status of surface Ag species were characterized through XRD and UV-vis.By qualitative analysis,the C_7H_8-temperature-programmed desorption results with the status of Ag species,the different storage sites and bond strength for C_7H_(8)storage were clarified.Ag+at the ion exchange site had the strongest bond to toluene,followed by Ag_n^(δ+)clusters,and the weakest bond was silver.The storage site could be modulated by controlling the storage time,so that toluene could be preferentially adsorbed on strong adsorption sites(Ag~+and Ag_n^(δ+)),which could enable the in situ thermal oxidation regeneration of toluene when the desorption temperature was higher than oxidation temperature.The method of regulating the strength of storage sites on the surface of molecular sieve was preliminarily mastered,and a suitable catalyst was constructed in this study,which can provide a promising strategy to synthesis and design bifunctional catalyst for toluene removal through“storage-in situ oxidation”cycling.

关 键 词：甲苯 银物种存在状态 存储位点调控 “存储-原位氧化”循环 

分 类 号：X511[环境科学与工程—环境工程]