Oxygen-functionalized activated carbon supported vanadia catalysts: Unexpected improvement in low-temperature NH3-SCR performance

Abstract

To regulate the active phase of carbon-supported catalysts, we report a synthetic protocol for oxygen-functionalized activated carbon (AC) supported vanadium catalysts for low-temperature selective catalytic reduction (LT-SCR) of NOx with NH3 via wet oxidation method using ammonium persulfate ((NH4)2S2O8, APS) as an oxidant. Optimum APS oxidative modification promoted the acid and redox properties of V/OAC2-60-3 and produced abundant reactive oxygen species, which enhance the catalytic activity significantly. Especially, APS activation promoted a high V4+/V5+ ratio on V/OAC2-60-3. The in-situ DRIFTs experiments demonstrated that V/OAC2-60-3 could absorb more NH3 species on Lewis acid sites and both the Eley-Rideal (E-R) and Langmuir-Hinshelwood (L-H) mechanisms were present on V/OAC2-60-3, and then a promotional mechanism for LT-SCR was proposed over V/OAC2-60-3. Enhancement of redox and acid potential cycle proved that this APS oxygen-functionalization is a viable strategy for carbon-based catalysts in NH3-SCR applications at low temperatures.