Facile synthesis of hollow nanotube MnCoOx catalyst with superior resistance to SO2 and alkali metal poisons for NH3-SCR removal of NOx

Abstract

A bottleneck of catalyst application to industrial flue gas denitrification is that the toxicity of SO2 and alkali metals in flue gas will result in the deactivation of active sites on the catalyst surface. In this work, in order to retain the active sites and minimize the catalyst deactivation by SO2 and alkali metals, we designed a hollow nanotube structured MnCoOx catalyst (MnCoOx-HNT) with surface anchoring function via a simple, easy to scale up and template free synthesis approach. The formation of hollow nanotube structure could be achieved easily by simply adjusting the metal salt precursor without any template or complicated equipment aids. More importantly, the hollow nanotube structured catalyst achieved excellent catalytic performance (80.1% NOx reduction) at 150 °C even when simultaneously exposed to the synthetic flue gas with coexistence of H2O, SO2 and alkali metals reaction feeds. The outstanding poisoning-resistant property of MnCoOx-HNT could be attributed to its unique hollow nanotube structure effectively protecting the active sites on the inner surface from being poisoned by SO2 or alkali metals. In addition, the abundant OH groups acted as sacrificial sites anchoring SO2 and alkali metals on the catalyst surface, resulting in the formation of sulfate species mainly in the form of surface sulfate rather than bulk sulfate. OH groups also had preference to combine with alkali metals, which delayed the combination of alkali metals with the Mn-Co active sites and consequently the poisoning process. The above excellent performance makes it possible for the MnCoOx-HNT to be applied to denitrification under extreme flue gas, and also provides a new idea for the design of functional materials with satisfactory SO2 and alkali resistance properties.