(445f) Insight into the Mechanism of Alkali Resistance over Cunbti Catalyst for the Selective Catalytic Reduction of NOx with NH3

Authors: 
Li, S. J., Zhejiang University
Wang, X., Key Laboratory of Biomass Chemical Engineering of Ministry of Education, Institute of Industrial Ecology and Environment, College of Chemical and Biological Engineering, Zhejiang University
Li, W., Zhejiang University

line-height:20.0pt;layout-grid-mode:char"> 14.0pt;font-family:" times new roman>Insight into the mechanism of
alkali resistance over CuNbTi catalyst for the selective catalytic reduction of
NOx with NH3

line-height:12.0pt;layout-grid-mode:char"> 11.0pt;font-family:" times new roman>Sujing Li*, " times new roman> Xiaoxiang Wang, Wei
Li*

layout-grid-mode:char"> " times new roman>Key Laboratory of Biomass Chemical
Engineering of Ministry of Education, Institute of
Industrial Ecology and Environment,
College of Chemical and Biological Engineering, Zhejiang
University, Hangzhou 310027, China

white">Abstract:
Alkaline
metals in the flue gas usually deactivated the SCR catalyst seriously in the
practical application. Compared with traditionally commercial VWTi catalyst,
CuNbTi catalyst exhibited a higher alkali resistance. CuNbTi maintained 80% NOx
conversion while VWTi catalyst fully deactivated. Different alkali metals were
individually employed to poison the catalysts and K showed the most toxic for
VWTi and CuNbTi catalysts. For VWTi catalyst, the variation of structure and
loss of active sites and reducibility resulted in the deactivation after 2%K2O
poisoning. By contrast, experimental and computational results indicated that
the alkali resistance of CuNbTi was mainly due to the trapping effect, namely
the interaction between Ti2NbOx support and K atoms. K
atoms were preferentially bound to Nb-OH and Nb=O with a lower bonding energy
of -2.33 eV - -2.83 eV to form KNbO3 when Cu atoms were coordinated
to Ti=O with a binding energy of -1.54 eV. This protected the active copper
species from linking to alkali and the active sites were preserved. Moreover, Ti2NbOx
support could weaken the impact of potassium on NH3 adsorbing and
activating on the surface of CuNbTi catalyst while the preserved copper species
provided adsorption sites and redox ability for NH3-SCR reaction. This
mechanism would provide a general strategy for developing novel anti-alkali
poisoning NH3-SCR catalyst in the future. Meanwhile, both
Eley-Rideal (E-R) and Langmuir-Hinshelwood (H-L) mechanisms with adsorbed NH3
coordinated to the Lewis acid sites and bidentate nitrate as the dominating
intermediate species existed during the NH3-SCR reaction procedure
over 2%K2O-CuNbTi at 225 oC.

white">Key
words:
CuNbTi
catalyst; VWTi catalyst; Alkali metal resistance

layout-grid-mode:char"> " times new roman>Fig.1. Schematic model of the alkali resistance
mechanism over CuNbTi catalyst.

 

References

text-indent:-18.0pt;layout-grid-mode:char"> font-family:" times new roman>[1] X.X. Wang, Y. Shi, S. J. Li*,
W. Li, Appl. Catal. B: Environ., 220 (2018) 234-250.

[2]
X.X. Wang, Q.L. Cong, L. Chen, Y. Shi, Y. Shi, S.J. Li*, W. Li*,
Appl. Catal. B: Environ., 246 (2019) 166-179.