氧化砷对SCR催化剂失活效应与再生研究
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- 论文作者：李俊华 ; 李想 ; 彭悦 ; 李先圣
- 英文论文作者：Junhua Li ; Xiang Li ; Yue Peng ; Xiansheng Li ; Department of Environment ; Tsinghua University
- 年：2016
- 作者机构：清华大学环境学院;
- 论文关键词：脱硝催化剂 ; As2O3 ; 再生 ; 酸性位
- 会议召开时间：2016-07-01
- 会议录名称：中国化学会第30届学术年会摘要集-第二十六分会：环境化学
- 语种：中文
- 分类号：X701;O643.36
- 学会代码：ZGHY
- 会议名称：中国化学会第30届学术年会-第二十六分会 ; 环境化学
- 会议地点：中国辽宁大连
- 主办单位：中国化学会
- 学会名称：中国化学会
- 页数：1
- 文件大小：212k
- 原文格式：D
- 会议级别：全国
摘要
烟气中由于气态As2O3或As4O6的存在,会导致脱硝催化剂反应寿命的大幅下降。先前研究表明气态砷的化合物通过扩散进催化剂表面不但堆积在催化剂孔内形成饱和层,还可以与催化剂的活性位发生作用,使反应活性丧失,阻碍催化反应的进行[1]。传统的硫酸或双氧水对砷的再生,尽管具有较高的砷去除率,但会导致大量的活性成分随之损失[2]。本工作首先通过探究不同含量As沉积对传统催化剂的活性和结构变化,分析探讨As在催化剂表面的存在形态和对反应历程的影响,归纳其中毒机制并开发新型再生液。研究发现:砷含量较低时,其主要以三价形式存在;而继续提高砷含量,大量结晶的五氧化二砷覆盖于催化剂表面。此外,As的存在不但会使催化剂表面的Lewis酸位被破坏,酸性位的热稳定性降低,还会增加体系的氧化性令大量的N2O副产物生成。最后,将中毒催化剂通过碱性硝酸钙溶液结合弱酸清洗,不但使催化活性得以恢复,而且可以极大地限制活性组分钒、钨的流失。
Heavy metal arsenic is serious poison for SCR catalyst deactivation.For regeneration of As poisoning catalysts,although H2O2 and H2SO4 solution was proved as an effective way to reduce the arsenic,parts of the vanadium and surface sulfate on the surface of catalysts are simultaneous removal under specific environment,which is harmful for keeping original catalytic activity.In this research,It is found that arsenic oxide existing form on poisoned catalyst is related to arsenic(As) proportion of catalyst composition.When the surface coverage of(V+W+As) is lower than 1,trivalent arsenic species(AsIII) is the major component and prefers to permeate into bulk-phase channels;while As at high concentration,pentavalent arsenic species(AsIV) covers the surface of catalyst.Finally,Ca(NO3)2–based regeneration method shows a good effect on surface arsenic oxide removal with trivial loss of active components,nevertheless it cannot effectively remove As2O3 in the catalyst micropores.
Heavy metal arsenic is serious poison for SCR catalyst deactivation.For regeneration of As poisoning catalysts,although H2O2 and H2SO4 solution was proved as an effective way to reduce the arsenic,parts of the vanadium and surface sulfate on the surface of catalysts are simultaneous removal under specific environment,which is harmful for keeping original catalytic activity.In this research,It is found that arsenic oxide existing form on poisoned catalyst is related to arsenic(As) proportion of catalyst composition.When the surface coverage of(V+W+As) is lower than 1,trivalent arsenic species(AsIII) is the major component and prefers to permeate into bulk-phase channels;while As at high concentration,pentavalent arsenic species(AsIV) covers the surface of catalyst.Finally,Ca(NO3)2–based regeneration method shows a good effect on surface arsenic oxide removal with trivial loss of active components,nevertheless it cannot effectively remove As2O3 in the catalyst micropores.
引文
[1]X.Li,J.Li,Y.Peng,et al.,Environ.Sci.&Tech.2015,49:9971.
[2]Y.Peng,J.Li,W.Si,et al.,Appl.Catal.B:Environ.2015,168-169:195.
[2]Y.Peng,J.Li,W.Si,et al.,Appl.Catal.B:Environ.2015,168-169:195.