MnCo2O4 spinel catalysts synthesized by nanocasting method followed by different calcination routes for low-temperature reduction of NOx using various reductants

Abstract

The present state of the art to control the vehicular NOx emissions, uses costly VWTi catalysts with urea solution as reductant, which work at higher temperature >200 °C. The present investigation is therefore, devoted to design a detailed experimental work to synthesize low cost and improved low-temperature SCR activity of MnCo2O4 catalyst by comparing preparation methods, calcination strategies and using different reductants in a wide range of temperature 50–450 °C. The catalysts were prepared by co-precipitation (CP) and nanocasting (NC) methods. For selection of the best catalyst, its precursor was calcined in stagnant air, flowing air and under reactive calcination (RC) in CO-air mixture. The SCR of NO was studied using various reductants (H2, LPG and H2-LPG) in a tubular reactor under the following conditions: 200 mg catalyst, 500 ppm NO, 8% O2, 1000 ppm LPG, 1% H2, 0.1% NH3 in Ar with a total flow rate of 100 mL/min. The inlet and outlet of the reactor were analyzed with the help of NO/NO2/NOx analyzer and gas chromatography. The catalysts were characterized by XRD, XPS, BET, SEM-EDX and FTIR. The catalyst prepared by NC method followed by RC route (Cat-R) exhibited the best NO reduction of 98.7% below 200 °C with H2-LPG-SCR. The exceptionally high activity with high N2 selectivity and good stability of Cat-R under the laboratory conditions were found. Characterization signified that the catalyst which exhibited oxygen deficient, higher surface area and the higher rate of LPG oxidation consequently have better SCR activity.