摘要
柴油发动机尾气是氮氧化物(NO_(x))主要来源之一,烃类化合物(HC)选择催化还原氮氧化物(HCSCR)技术是一种常见的脱除氮氧化物方法,但是在HC-SCR催化还原NO_(x)中,Ag基氧化物催化剂的低温脱硝活性较差,活性温度窗口较窄。在HC-SCR反应气氛中添加少量氢气(H_(2))能显著提升Ag/γ-Al_(2)O_(3)等催化剂的低温脱硝活性,拓宽活性温度窗口。本文以贫燃柴油发动机尾气脱硝为背景,归纳了H_(2)对活性中心Ag物种种类、烃类化合物和氧气的活化以及活性含氮中间体转化的影响,总结了H_(2)在提升HC-SCR催化剂抗硫和抗水性能起到的作用,列举了近年来新型催化剂在H_(2)辅助HC-SCR (H_(2)-HC-SCR)脱硝体系中的应用。相关研究表明H_(2)促进HC-SCR中具有催化活性的Ag物种的生成,促进O2活化为活性氧物种,加速烃类化合物转化为异氰酸盐、烯醇物种等关键中间体,并减少可毒化活性中心硝酸盐物种的含量,从而提高HC-SCR脱硝活性。H_(2)辅助HC-SCR脱硝技术有望在机动车尾气脱硝中发挥重要作用,推动HC-SCR脱硝技术的发展。
Diesel engine exhaust is one of the sources of nitrogen oxides(NO_(x)).Hydrocarbon(HC)selective catalytic reduction(HC-SCR)of nitrogen oxides is a common technique for NO_(x) reduction.However,the NO_(x) reduction activity of Ag-based oxide catalysts is not sufficiently high in low temperature region and the active temperature window is narrow.The addition of small amounts of hydrogen(H_(2))in HC-SCR reaction atmosphere can significantly increase the low-temperature denitrification activity and broaden the active temperature window of catalysts such as Ag/γ-Al_(2)O_(3).Based on the background of lean-burn diesel engine exhaust denitration,the aim of this review is to summarize the effects of H_(2) on the types of active Ag species,the activation of hydrocarbons and oxygen,and the conversion of active nitrogen-containing intermediates.The role of H_(2) in improving the sulfur and water resistance of HC-SCR catalysts is summarized,and the application of new catalysts in H_(2)-assisted HC-SCR(H_(2)-HC-SCR)reaction in recent years is introduced as well.Relevant studies have shown that H_(2) promotes the formation of the active Ag species in HC-SCR and the activation of O2 into reactive oxygen species.H_(2) also accelerates the conversion of hydrocarbons into key intermediates such as isocyanate and enolic surface species and reduces the content of nitrate species which would poison the catalytic active sites.Blending H_(2) into the feed of the HC-SCR eventually improves the denitrification activity of HC-SCR.H_(2)-assisted HC-SCR denitration technology is expected to play an important role in the denitration of motor vehicle exhaust,and to promote the development of HC-SCR of nitrogen oxides technology.
作者
周强
殷成阳
刘百军
赵震
ZHOU Qiang;YIN Chengyang;LIU Baijun;ZHAO Zhen(State Key Laboratory of Heavy Oil Processing,China University of Petroleum,Beijing 102249,China;Institute of Catalysis for Energy and Environment,College of Chemistry and Chemical Engineering,Shenyang Normal University,Shenyang 110034,Liaoning,China)
出处
《化工进展》
EI
CAS
CSCD
北大核心
2024年第11期6140-6154,共15页
Chemical Industry and Engineering Progress
基金
国家重点研发计划(2021YFB3500603,2021YFB3500601)
国家自然科学基金(U1908204)
沈阳市科技计划(23-407-3-14)。
关键词
选择催化还原
氢气
活化
低温脱硝活性
催化剂
selective catalytic reduction(SCR)
hydrogen
activation
low-temperature denitrification activity
catalyst
