锰基低温NH 3-SCR脱硝催化剂的研究概述

A Review of Mn-based Low Temperature NH 3-SCR Denitration Catalyst

氨气选择性催化还原技术(NH_(3)-SCR)因利用NH_(3)作为还原剂实现NO_(x)的高效转化而受到广泛关注。虽然V_(2)O_(5)-WO_(3)(MoO_(3))/TiO_(2)催化剂已经投入商业化应用,但为了满足更高和更复杂的实际性应用需求,特别是针对低温脱硝催化剂的开发仍然刺激着新型催化剂的发展。在诸多金属氧化物催化剂中,锰氧化物由于具有多变的阳离子价态、表面不稳定氧和优异的氧化还原性能,在低温NH_(3)-SCR反应中展现出巨大的潜力。然而,目前锰基脱硝催化剂的效率仍受制于NO_(x)的转化率、N_(2)选择性、工作温度窗口以及失活物质(SO_(2)和H_(2)O、碱/碱土金属、重金属等)的影响。因此,近年来研究者们主要针对以上四个方面致力于提高锰基低温催化剂的性能,并取得了丰硕的成果,在充分利用锰氧化物优势的前提下大幅提升了其在低温下的工作效率。除了研究单一锰氧化物的效率外,研究者们通过水热法、水浴法、浸渍法等多种合成方法将过渡金属和稀土金属两类元素用于锰氧化物的修饰,复合和掺杂修饰之后所得的多元金属氧化物解决以上四个方面问题的能力显著提升。此外,通过研究负载锰氧化物的不同基底材料,如TiO_(2)、Al_(2)O_(3)、碳材料和无机非金属矿物等,也可以实现催化剂的效率和稳定性的提高。同时,通过深入探究锰基低温催化剂的相关反应机制,包括“Langmuir-Hinshelwood”机制、“Eley-Rideal”机制和“Fast SCR”反应机制,能够对提升催化剂的效率做出理论指导。文中主要总结了近年来研究人员对提升锰基低温催化剂的工作效率而做出的努力,分别介绍了锰基催化剂的挑战、针对锰氧化物的调控和相关反应机理等,概述了锰基低温催化剂所面临的问题并做出了展望,以期为制备高效稳定和环境友好的低温脱硝催化剂提供参考。

Selective catalytic reduction with Ammonia(NH_(3)-SCR),which has received widespread attention by utilizing NH_(3) as reducing agents to achieve high-efficiency conversion of NO_(x).Although commercial V_(2)O_(5)-WO_(3)(MoO_(3))/TiO_(2) catalysts have been came into service,however,in order to meet higher and more complex practical application requirements,especially the exploitation of low-temperature denitration catalysts still stimulate the development of novel SCR catalysts.Among varied metal oxide catalysts,manganese oxide exhibits great potential in low-temperature NH_(3)-SCR reactions,which can be ascribed to its variable cation valence,unstable surface oxygen and excellent redox performance.However,the efficiency of current manganese-based denitration catalysts is still limited by the conversion rate of NO_(x),N_(2) selectivity,operating temperature window,and deactivation substances such as SO_(2) and H_(2)O,alkaline/alkaline earth metals,and heavy metals.Therefore,in recent years,researchers have focused on improving the working efficiency of manganese-based low-temperature catalysts in the above four aspects,and have achieved fruitful results.On the premise of making full use of the advantages of manganese oxide,the work efficiency of manganese-based catalysts at low temperatures is significantly improved.In addition to studying the efficiency of single manganese oxide,researchers have used a variety of synthetic methods such as hydrothermal,water bath,and immersion methods to modify manganese oxides with transition metals and rare earth metals.The multi-element metal oxide formed after compounding and doping modification can greatly improve the ability to address the above four aspects.Moreover,by studying diffe-rent substrate materials supporting manganese oxide,such as TiO_(2),Al_(2)O_(3),carbon materials and inorganic non-metallic minerals,the efficiency and stability of the catalyst can also be improved.And through in-depth exploration of the relevant reaction mechanisms of manganese-based low-temperature catalysts,including“Langmuir-Hinshelwood”“Eley-Rideal”and“Fast SCR”reaction mechanism,which can provide theoretical guidance for improving the efficiency of the catalyst.This review mainly summarizes the efforts made by researchers in recent years to improve the efficiency of manganese-based low-temperature catalysts,and the challenges of manganese-based catalysts,the regulation of manganese oxides and related reaction mechanisms are introduced respectively.Furthermore,we pay attention to the problems that confronting the current state-of-the-art manganese-based low-temperature catalysts and put forward corresponding prospects.It is expected to provide a reference for the preparation of high-efficiency,stable and environment-friendly low-temperature denitration catalysts in the future.