Improving of cold-start and combustion emissions in lean NO conditions with active and selective AgAl mesoporous catalysts

ASPROMONTE, S.G.; BOIX, A.V.

Journal of Environmental Chemical Engineering

ELSEVIER SCIENCE BV

Año: 2019 vol. 7

2213-3437

Mesoporous AgAl-MCM41 catalytic adsorbents were synthesized. Template-ion exchange (tie) and incipient wetimpregnation (iwi) methods were employed to incorporate Ag. The presence of non-structural and structural Ag(I) ionic species were detected. As the former refers to the ions that occupy an active site, the latter are part of thesupport hexagonal network. In addition, Ag2O nanoparticles were observed.The samples were used in C7H8 adsorption at 100 °C and in the selective catalytic reduction of NOx withtoluene as reductant and H2O. The maximum NOx conversion was achieved with AgAl-iwi catalyst. Under dryconditions, a conversion of 84% was reported. With 2 or 10% H2O, the conversion was maintained between 80and 90% and it is maintained at 70% after 50 h of reaction and successive cycles of water incorporation. Inaddition, the amount of toluene adsorbed follows the next order: AgAl-iwi>AgAl-tie>Al-MCM41>MCM41.Instead, the quantity of C7H8 desorbed by the AgAl-tie is 34% above 400 °C. The AgAl-iwi solid show a ratiobetween the adsorbed and desorbed toluene of 99% in a wide range of temperature. This behavior is due to thepresence of non-structural Ag(I) ions, which are the adsorption sites for the toluene.Comparing the performance of these materials with the AgNa-mordenite, the AgAl-iwi is more active catalystand effective adsorbent between 100 and 550 °C. Thus, the mesoporous structure allows a better dispersion ofthe active sites, as well as the diffusion of toluene