In-situ DRIFTs study for synergistic removal of NOx and o-DCB over hydrotalcite-like structured Cr(x)/LDO catalysts

Abstract

Developing efficient and stable catalysts for synergistic removal of NOx and dioxin has always been key for controlling air pollution. For this, the hydrotalcite-like structured Cr(x)/LDO catalysts were successfully synthesized for synergistic removal of NOx and o-DCB using a co-precipitation method. The performance test results show that the Cr(0.25)/LDO catalyst has the best catalytic performance, and the NOx and o-DCB conversions are 89% and 82% at 250 °C, respectively. In addition, the reaction mechanism of NH₃-SCR and o-DCB catalytic oxidation on the surface of the Cr(0.25)/LDO catalyst, and the interaction between the two reactions were investigated by designing in- situ DRIFTS experiments. The results indicate that the NH₃-SCR reaction follows both E–R and L–H reaction mechanisms. The reaction pathway for the o-DCB oxidation process is proposed: o-DCB → chlorinated phenolate → benzoquinone → maleic acid, formic acid, acetic acid, etc. → H₂O, CO₂, HCl. Moreover, there are interactions between NH₃-SCR and catalytic oxidation of o-DCB. At low temperature, there is obvious competitive adsorption between NH₃/NO and o-DCB. The competitive adsorption between NH₃/NO and o-DCB leads to the decrease of the o-DCB conversion. At high temperature, NH₃-SCR and o-DCB oxidation exhibit a synergistic effect, NO₂in situ-generated from the oxidation of NO can further participate in the o-DCB oxidation and reduce the accumulation of o-DCB oxidation intermediates on the catalyst surface. The research results contribute to understanding the reaction processes of Cr(x)/LDO catalysts and provide support for practical applications.