Abstract
The importance of the low-temperature selective catalytic reduction (LT-SCR) of NOx by NH3 is increasing due to the recent severe pollution regulations being imposed around the world. Supported and mixed transition metal oxides have been widely investigated for LT-SCR technology. However, these catalytic materials have some drawbacks, especially in terms of catalyst poisoning by H2O or/and SO2. Hence, the development of catalysts for the LT-SCR process is still under active investigation throughout seeking better performance. Extensive research efforts have been made to develop new advanced materials for this technology. This article critically reviews the recent research progress on supported transition and mixed transition metal oxide catalysts for the LT-SCR reaction. The review covered the description of the influence of operating conditions and promoters on the LT-SCR performance. The reaction mechanism, reaction intermediates, and active sites are also discussed in detail using isotopic labelling and in situ FT-IR studies.
Highlights
The non-renewable fossil fuels are continuing to remain the dominant energy source in power plants and automobiles to satisfy the ever-growing energy demands
This review demonstrated the action of different promoters and supports on the catalytic performance and SO2 /H2 O tolerance of the transition metal-based catalysts in NH3 -SCR of nitrogen oxide (NOx)
Since the emission standards for NOx are becoming more stringent to keep our atmosphere Since the emission standards for NOx are becoming more stringent to keep our atmosphere clean, the widespread use of fossil fuel in automobiles and industries require advanced catalytic clean, the widespread use of fossil fuel in automobiles and industries require advanced catalytic materials for NOx emission control
Summary
The non-renewable fossil fuels are continuing to remain the dominant energy source in power plants and automobiles to satisfy the ever-growing energy demands. Many researchers continue to develop highly active catalysts for low-temperature NH3 -SCR in a wide temperature window With this perspective, several transition metal oxide-based catalysts have been extensively investigated for low-temperature NH3 -SCR reaction due to their excellent redox properties, low price, Catalysts 2019, 9, 349; doi:10.3390/catal9040349 www.mdpi.com/journal/catalysts. We published a series of papers on Mn-based SCR catalysts that showed a highly promising deNOx potential in the low-temperature region [5,22,23,24,25,26] These catalysts are very sensitive to the presence of SO2 in the feed and exhibit lower N2 selectivity [8,27,28,29]. The reported catalysts were divided into four categories, such as binary, ternary/multi, supported single, and supported binary/multi-transition metal-based catalysts
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