Dual Promotional Effects of TiO-Decorated Acid-Treated MnO Octahedral Molecular Sieve Catalysts for Alkali-Resistant Reduction of NO .

Alkali metals generated during waste incineration in power stations are not conducive to the control of nitrogen oxide (NO ) emission. Hence, improved selective catalytic reduction of NO with ammonia (NH-SCR) in the presence of alkali metals is a major issue for practical NO removal. In this work, we developed a novel TiO-decorated acid-treated MnO octahedral molecular sieve (OMS-5(H)@TiO) catalyst with improved alkali-resistant NO reduction at low temperature, and the dual promotional effects of OMS-5(H)@TiO catalysts were clarified. It was found that the special structure of the acid-treated MnO octahedral molecular sieve (OMS-5(H)) was responsible for the trapping of alkali metals and high deNO activity at low temperature. Subsequently, the decoration by TiO further improved the redox properties by accelerating the high ratio of Mn and O on the surface of the highly active (OMS-5(H)@TiO) catalyst. Moreover, a thorough mechanism study via in situ diffuse reflectance infrared Fourier transform spectroscopy (in situ DRIFTs) demonstrated that the acid treatment led to remarkable increment of acid sites, which enabled the catalyst to resist alkali metals in the form of ion exchange. Meanwhile, the decoration of TiO further increased the strength of the Lewis acid sites, assisting more active intermediate species to effectively take part in the deNO reaction. Besides, a "fast SCR" process was observed to certify that the decoration of TiO promoted the improvement of low-temperature activity in the presence of alkali metals. The dual effects combining OMS-5(H) with TiO decoration in terms of alkali metal resistance and high catalytic activity at low temperature proved that the high-performance deNO catalyst was successfully developed in this work. The work paves a way for the development of superior low-temperature SCR catalysts with improved NO reduction efficiency in the presence of alkali metals.