Abstract
FeVO4 and Fe0.5Er0.5VO4 were prepared and loaded over standard Selective Catalytic Reduction (SCR) supports based on TiO2-WO3-SiO2 (TWS) and redox active supports like CeO2 and CeZrO2 with the aim of finding a suitable formulation for simultaneous soot abatement and NH3-SCR and to understand the level of interaction between the two reactions. A suitable bi-functional material was identified in the composition FeVO4/CeZrO2 where an SCR active component is added over a redox active support, to increase carbon oxidation properties. The influence of the presence of ammonia in soot oxidation and the effect of the presence of soot on SCR reaction have been addressed. It is found that the addition of NO and NO/NH3 mixtures decreases at different levels the oxidation temperature of carbon soot, while the presence of carbon adversely affects the NH3-SCR reaction by increasing the oxidation of NH3 to NO, thus lowering the NO removal efficiency.
Highlights
The study of Diesel exhaust after-treatment technologies is focusing on one side in finding novel formulations for active soot oxidation [1] and de-NOx catalysts [2,3,4] and on the other side in looking for suitable strategies to limit the number of different process units and combine more functionalities in one single step [5]
Selective Catalytic Reduction (SCR) catalyst materials were selected among metal/rare earth vanadates that have been shown to act as efficient catalyst precursors for NH3 -SCR reaction [11,12,13,14,15,16], while among the different supports, standard TiO2 -WO3 -SiO2 (TWS) was used and compared with more efficient carbon oxidation carriers like CeO2 and Ce0.75 Zr0.25 O2 [17]
3 Peak temperature calculated from CO2 profiles during TPO runs in a flow-trough microreactor under 500 ppm NO, 500 ppm NH3, 10% O2, 5% H2 O, atmosphere. These results clearly show that the mechanisms involved in soot oxidation on ceria and ceria-zirconia are different than those observed over TWS and alumina
Summary
The study of Diesel exhaust after-treatment technologies is focusing on one side in finding novel formulations for active soot oxidation [1] and de-NOx catalysts [2,3,4] and on the other side in looking for suitable strategies to limit the number of different process units and combine more functionalities in one single step [5]. The aim of this work is to study the behaviour of a suitable catalyst with acceptable performances both in soot oxidation and in the NH3 -SCR reaction conducted simultaneously. For this purpose, an active SCR catalyst formulation has been loaded over supports showing different soot oxidation functionalities. This work investigates FeVO4 and Catalysts 2018, 8, 130; doi:10.3390/catal8040130 www.mdpi.com/journal/catalysts
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