466526 CeO2 Supported Metal Oxide Catalysts for NOx Removal
It has been found that lean burn and diesel engines have much greater efficiency in terms of fuel consumption and power compared to their gasoline engine counterparts. However, due to the high air to fuel ratio of the engine, greater amounts of NOx is produced therefore these more efficient engines are struggling to meet emission regulations set by the Environmental Protection Agency (EPA). Studies have shown that ammonia-based selective catalytic reduction (NH3-SCR) with the use of zeolite catalyst have shown efficient NOx conversion to nitrogen (N2) and water. Due to the high efficiency of lean burn and diesel engine, there is a demand to identify a catalyst that has both high durability for the temperature ranges that a diesel engine operates in and relatively cheap to manufacture. Currently, conversion of NOx requires the use of expensive precious metal loaded catalysts, ergo the need to develop a cheaper solution is in high demand in order to meet the regulation. Various metal-exchanged zeolites-base metal catalysts such as Cu- and Fe-exchanged ZSM-5 (MFI) have been investigated for SCR catalytic activity and stated that the effective temperature ranges for Cu- and Fe-ZSM-5 are 250− 450°C and 350− 650°C, respectively. But De-NOx efficiency at low temperature is still challenging to meet the emission regulation. Mn doped ceria showed improved activity at lower temperature than zeolite based catalysts.
Ceria (CeO2¬) has been studied since it has an oxygen reservoir capacity, which stores and release oxygen via the redox shift between Ce4+ and Ce3+ under oxidizing and reducing conditions, respectively. Metal-doped CeO2 enhanced its oxygen mobility and provide activated oxygen to the reactant. In this study, a series of CeO2-supported transition metal (Mn, Co and Cu) catalysts were investigated for NH3-SCR and NO oxidation. Catalysts were prepared by using the incipient wetness impregnation method (IM) at different surface species loadings (0.5, 1, 2, 10 & 30 wt.%). Operando experiment condition was applied to understand (1) the relationship between catalyst structure and activity/selectivity, (2) surface reaction, and (3) reaction mechanisms. Several spectroscopic techniques, such as XRD, Raman spectrometer and FTIR, were also applied under ex-situ/in-situ conditions.
We gratefully acknowledge the financial support for this study from SBU/BNL 2015 SEED grant and the Department of Materials Science & Engineering at Stony Brook University (SBU) through start-up research funding as well as Brookhaven National Lab and Advance Energy Centre at SBU for laboratory facilities.
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