Search

The effect of surface synergetic oxygen vacancy constructed by bimetallic metal on CO selective catalytic reduction of NO x (CO-SCR) was investigated by loading Fe and Ni on TiO 2. Herein, a series of Ni x Fe 1−x /TiO 2 was prepared by the wet impregnation method. The microstructures, elemental states, and reactivity of the prepared samples were characterized by XRD, HRTEM, EPR, H 2 -TPD, CO-TPD, NO-TPD, and XPS. The results show that the synergistic effect between Ni and Fe effectively optimized the dispersion of Fe and constructed abundant Ni-O-Fe bonds. Furthermore, the excellent CO trapping capacity led to an increased number of cNi-□-Fe structures (SSOV), which effectively promotes NO activation at low temperatures. The in situ DRIFT spectra illustrated that N 2 O intermediate species rapidly transformed into N 2 -based species at 250 ℃, and the catalyst modified with Ni presented excellent NO conversion and N 2 selectivity. The Ni 0.2 Fe 0.8 /TiO 2 sample demonstrated almost 100% NO conversion, 93% N 2 selectivity, and considerable stability with a gas hourly space velocity of 33,000 h-1 at 250 ℃. This work provides a novel way for the design and preparation of a bimetallic NO reduction catalyst to promote the further study of efficient CO-SCR catalysts. [Display omitted] • Ni and Fe constructed Ni-□-Fe (SSOV) to accelerated the breakage of N-O bonds. • Ni regulated the capture of CO and weakened the adsorption of NO. • Ni 0.2 Fe 0.8 /TiO 2 exhibits 100% NO x conversion and 93% N 2 selectivity at 250 ℃. • NO+CO reaction on Ni 0.2 Fe 0.8 /TiO 2 conforms to E-R, L-H and M-K mechanism. [ABSTRACT FROM AUTHOR]

[Display omitted] • Cu-SSZ-13 catalysts with different Cu2+ species were synthesized successfully. • The balance between Cu2+-2Z and [Cu(OH)]+-Z exhibited optimal DeNOx performance. • The optimal ratio of Cu2+ species can promote the rapid formation of intermediates. In diesel vehicle exhaust after-treatment systems, high silica Cu-SSZ-13 has received increasing attention as a commercialized catalyst owing to its high efficiency in selective catalytic reduction reactions with NH 3 (NH 3 -SCR). However, research on the regulation of Cu2+ species within metal active centers in the pore structure of chabazite (CHA)-type zeolite to improve catalytic performance lacks sufficient depth. Herein, SSZ-13 zeolite with various Al distributions was prepared by adjusting the proportion of N,N,N-Trimethyl-1-adamantanaminiumhydroxide (TMAdaOH) and Na in the initial gel. Moreover, three representative Cu-SSZ-13 catalysts with different Cu2+ species were synthesized via an ion exchange method. 23Na MAS NMR and NO adsorption infrared spectroscopy results revealed that with increasing Na content and decreasing TMAdaOH concentration in the initial gel, the number of paired Al in the CHA framework gradually increased. Consequently, this increased the number of Cu2+-2Z sites near six-membered ring (MR) and reduced the amount of [Cu(OH)]+-Z sites near eight-MR. The fresh Cu-SSZ-13 catalyst, with a moderate amount of Cu2+-2Z and [Cu(OH)]+-Z, exhibited optimal catalytic performance across the entire temperature window. After hydrothermal aging, Cu-SSZ-13 with a higher concentration of Cu2+-2Z species featured optimal performance among all Cu-SSZ-13 catalysts above 400 °C. These findings indicated the significance of balancing the amount of both Cu2+-2Z and [Cu(OH)]+-Z in the Cu-SSZ-13 zeolite. Additionally, the results elucidated the reaction intermediates involved in the NH 3 -SCR process catalyzed by Cu-SSZ-13 with various Cu species. [ABSTRACT FROM AUTHOR]

The synergistic effect of Zn and Mg can improve the dispersion of Ag on Al 2 O 3 support and increase the proportion of Ag+ and Ag δ n + , which is beneficial to the selective catalytic reduction of NO by propylene. [Display omitted] • Zn and Mg promote the formation of ZnAl 2 O 4 and MgAl 2 O 4 spinels on the surface of γ-Al 2 O 3 carriers. • Inhibits active ingredient agglomeration and improves dispersion. • Facilitates the transitions regulation of Ag+, Ag δ n + and Ag0. • Improved NO conversion, water and sulfur resistance of AgAl catalysts at low temperatures. The effects of Zn and Mg on selective catalytic reduction (SCR) of NO with C 3 H 6 were studied by introducing Zn and Mg into Ag/Al 2 O 3 catalysts with the rotary evaporation method. The effects of Zn and Mg on the microstructure and denitrification performance were characterized by N 2 adsorption–desorption, XRD, UV–vis spectroscopy, H 2 -TPR, NO + O 2 -TPD, XPS and HR-TEM. The results showed that bimetallic Zn and Mg modification increased the proportion of ZnAl 2 O 4 and MgAl 2 O 4 spinels in Ag/Al 2 O 3 catalysts, regulated the dispersion of Ag on the Al 2 O 3 support, and promoted the conversion of Ag0 to active Ag+ and Ag δ n + , which enhanced the NO adsorption capacity and optimized denitrification performance at low temperature. Furthermore, in-situ DRIFTS suggested that enol and acetate generated by C 3 H 6 in the presence of H 2 will react with NO + O 2 to form more –NCO and –CN intermediate species, which facilitated the formation of N 2 and improved N 2 selectivity. Specially, Ag2.5Zn2.5MgAl exhibited more than 95 % NO x conversion, excellent water resistance and sulfur resistance at 300 °C with GHSV = 100 000 h−1. This process promotes the development of efficient vehicle exhaust treatment technology and the application of related products. [ABSTRACT FROM AUTHOR]