Tailoring the simultaneous abatement of methanol and NO_x on Sb-Ce-Zr catalysts via copper modification

Abstract

● Cu addition enhances CH₃OH oxidation and alleviates its inhibitory effect on SCR.

● Cu addition improves the activation of SCR reactants in the presence of methanol.

● Damaged structure by more Cu addition decreases specific surface area and acidity.

● Excessive Cu addition would lead to the narrowing of SCR temperature window.

Simultaneously removal of NO_x and VOCs over NH₃-SCR catalysts have attracted lots of attention recently. However, the presence of VOCs would have negative effect on deNO_x efficiency especially at low temperature. In this study, copper modification onto Sb_0.5CeZr₂O_x (SCZ) catalyst were performed to enhance the catalytic performance for simultaneous control of NO_x and methanol. It was obtained that copper addition could improve the low-temperature activity of both NO_x conversion and methanol oxidation, where the optimal catalyst (Cu_0.05SCZ) exhibited a deNO_x activity of 96% and a mineralization rate of 97% at 250 °C, which are around 10% higher than that of Cu free sample. The characterization results showed that copper addition could obviously enhance the redox capacity of the catalysts. As such, the inhibition effect of methanol incomplete oxidation on NO adsorption and NH₃ activation were then lessened and the conversion of surface formamide species were also accelerated, resulting in the rising of NO_x conversion at low temperature. However, excessive copper addition would damage the Sb-Ce-Zr oxides solid solution structure owing to Cu-Ce strong interactions, decreasing the surface area and acidity. Meanwhile, due to easier over-oxidation of NH₃ with more Cu addition, the temperature window for NO_x conversion would become quite narrow. These findings could provide useful guidelines for the synergistic removal of VOCs over SCR catalyst in real application.

Graphical abstract

Keywords

Copper modification / Sb-CeZr ₂O _x catalyst / NO _x / Methanol / Simultaneous removal

References

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