posted on 2023-12-14, 16:33authored byJiaying Xing, Qitong Xue, Jianjun Chen, Jinxing Mi, Xiaoping Chen, Jianqiang Shi, Zhiming Liu, Junhua Li
Vanadium-based catalysts play a pivotal role in the emission
control
of industrial NOx via selective catalytic
reduction (SCR) technology. However, little attention has been paid
to the potential emission of greenhouse gas N2O under complex
working conditions. This work reports that a commercial V2O5/TiO2 catalyst may lead to significant N2O emission without greatly changing the outlet NOx concentration after chromium (Cr) deposition. With
a Cr loading of 2 wt %, N2O concentration increased from
27.8 to 199.2 ppm at 350 °C with the value of outlet N2O/(N2O+N2) from 2.5% to 19.4%. Experimental
results combined with DFT+U calculations suggest that nonselective
catalytic reduction (NSCR) is the main route for N2O formation
in a wide temperature range of 250 ∼ 400 °C. It is stemmed
from the fact that the covalent interaction between Cr and V species
on the V2O5/TiO2 surface accelerates
the conversion of V4+ + Cr6+ → V5+ + Cr3+, leading to a larger proportion of surface
V5+. More importantly, surface V5+ is highly
related to the redox property of the V2O5/TiO2 catalyst, which is beneficial to NSCR reaction rather than
the standard SCR process. The work suggests that to better inhibit
the emission of greenhouse gases during the NH3–SCR
process, monitoring N2O emission should be included along
with the NOx concentrations, especially
in complex flue gases.