Enhanced activity and water resistance of SiO2-coated Co/In-SSZ-13 catalysts in the selective catalytic reduction of NOx with CH4

Abstract

CH4 selective catalytic reduction of NOx (CH4-SCR) is a promising technology to synergistic control of CH4 and NOx emission from LNG-powered vehicles and ships, while its insufficient catalytic activity and H2O resistance are key barriers for application. In this work, SiO2 coated Co3O4/In-SSZ-13 catalysts (Co/In-Z@Si) were prepared to simultaneously improve the CH4-SCR activity and H2O tolerance. The proper Co3O4 introduction enhanced the catalytic performance of the In-SSZ-13, while excessive amount of Co3O4 addition led to more CH4 being oxidized and insufficient CH4 participating in the CH4-SCR reaction. There was a “seesaw effect” between NO oxidation and CH4 oxidation performance of the catalysts. The H2O resistance of the Co/In-Z catalysts significantly enhanced via ultrathin SiO2 coating (~ 6nm). The NOx and CH4 conversion maintained 81% and 90% in the presence of H2O at 500 °C for the Co/In-Z@Si catalyst, respectively. The in situ DRIFTS confirmed that the SiO2 coating could adsorb H2O molecules, prevent H2O from contacting the active sites, and limit the competitive adsorption between H2O and CH4 on the catalyst. This work provides a good candidate with superior catalytic performance and H2O resistance for removal of NOx and CH4 from LNG-powered vehicles and ships simultaneously.