抗高温失活SCR脱硝催化剂研究进展

Progress in the Development of SCR Denitration Catalysts with Resistance of High-temperature Deactivation

V_(2)O_(5)-WO_(3)(MoO_(3))/TiO_(2)催化剂是目前广泛应用的商用选择性催化还原(SCR)脱硝催化剂。商用选择性催化还原(SCR)脱硝催化剂。然而,在实际工业应用过程,特别是垃圾焚烧锅炉、燃油及燃气轮机等设备的烟气脱硝中,常规钒钨(钼)钛系脱硝催化剂存在各种失活问题,高温烧结是其中重要的原因之一。本文首先介绍了钒钨(钼)钛系脱硝催化剂高温失活的三种主要机理,包括高温下载体TiO_(2)晶格转变、还原剂NH_(3)选择性催化氧化以及水蒸气-NH_(3)竞争性吸附。然后,系统分析了目前提高SCR脱硝催化剂耐高温性能的主要技术手段,包括提高催化剂载体热稳定性及抑制还原剂NH 3被氧化等,其中Ti-Zr、Ti-Si及分子筛是优选的热稳定型催化剂载体,金属氧化物(如Fe_(2)O_(3)、WO_(3))是主要的具有抑制NH 3催化氧化能力的活性组分。此外,本文还对高温催化剂的抗水改性技术手段进行了简要叙述,包括增加抗水助剂和采用疏水型载体,其中可选的抗水助剂包括贵金属(如Pt、Pd等)以及金属氧化物(如WO_(3)、CeO_(2)等)等,其主要目的是提高催化剂表面吸附活化反应组分的能力,而采用疏水型载体(如抗水型分子筛、具有抗水保护层包覆的金属氧化物)则可抑制水蒸气竞争吸附,提高催化剂的耐水性能。最后,基于现有研究进展的分析和总结,本文对未来抗高温失活SCR脱硝催化剂的发展趋势做出了展望,相关结论可对后续SCR脱硝催化剂抗高温失活改性的研究提供重要支撑。

The V_(2)O_(5)-WO_(3)(MoO_(3))/TiO_(2)catalysts are widely utilized in the commercial fields of selective catalytic reduction(SCR)denitration.However,many factors can result in the deactivation of the catalysts in the process of SCR denitration operation,especially in the industrial processes of waste incinerators and oil/gas turbines,among which the thermal deactivation in high-temperature flue gas is important.This review summarizes the deactivation mechanisms of the SCR catalysts at high temperatures,including the crystalline transformation of TiO_(2)support,the catalytic oxidation of NH_(3)by V_(2)O_(5),and the competitive adsorption between water vapor and NH_(3).Then,the developments of SCR denitration catalysts with the resistance of high-temperature deactivation are presented,i.e.,improving the thermal stability of support and inhibiting the catalytic oxidation of gaseous NH_(3).Ti-based composite supports,including Ti-Zr/Ti-Si supports and zeolites,are considered to be optimal for improving the thermal stability of support,while metal oxides,such as Fe_(2)O_(3)and WO_(3),are the main active components to prevent the NH_(3)catalytic oxidation.In addition,the technologies for the thermal resistance improvement of SCR denitration catalysts are briefly discussed,including the addition of anti-water components and the application of hydrophobic supports.With the presence of anti-water components such as noble metals(Pt,Pd)and metal oxides(WO_(3),CeO_(2)),the adsorption of gaseous reactants over the catalyst can be promoted.Besides,using the hydrophobic carriers,such as zeolites and carriers coated with water-resistant layers,can also suppress the adsorption of water vapor.Finally,the developing prospects of SCR denitration catalysts with superior resistance to high temp erature are discussed.This review can provide some fundamental instructions for the improvement of SCR denitration catalysts with the resistance of thermal deactivation in the high-temperature flue gas.