Low-temperature Catalytic Reduction Of NO Research Articles

Graphene Based Mesoporous Manganese-Cerium Oxides Catalysts: Preparation and Low-temperature Catalytic Reduction of NO

Graphene Based Mesoporous Manganese-Cerium Oxides Catalysts: Preparation and Low-temperature Catalytic Reduction of NO

UiO66-Derived Catalyst for Low Temperature Catalytic Reduction of NO with NH3.

Diesel exhaust emissions are major outdoor air pollutants. Reducing the emission of NOx by diesel commercial vehicles and related machineries is at present a great challenge. In this study, we synthesize a catalyst for low-temperature catalytic reduction of NO using calcinated UiO-66(Zr) as a host for the doping of cerium, manganese, and titanium by the incipient wetness impregnation, followed by the dispersion of 1.0 wt % platinum. A solid solution of Ce0.15Zr0.54Mn0.11Ti0.20O2/1.0Pt (CZMTO/Pt) is synthesized as evident by the structural characterizations. The catalyst demonstrates significant NO reduction in the laboratory due to the synergistic effect of various elements, with NO conversion above 80% at 160 °C.

Hierarchically interconnected porous MnxCo3-xO4 spinels for Low-temperature catalytic reduction of NO by CO

Developing efficient catalysts for low reaction-temperature catalytic reduction of NO by CO (CO–DeNOx) is desirable but very challenging. Here, we report that hierarchically interconnected porous (HIP) MnxCo3-xO4 spinels, synthesized by a facile citric acid-assisted sol–gel method, can act as highly efficient catalysts for CO–DeNOx. The obtained Mn0.3Co2.7O4 displayed a much-enhanced catalytic performance with 87% NO removal at 100 °C and a wide active-temperature window (100–400 °C). Its superior activity stems from the following reasons: (i) the high-valence of Mn3+, Mn4+, and Co3+ species in the Co–O–Mn structure enables the high catalytic activity and the effective redox-cycling of the Co3+ and Co2+ adsorption sites; (ii) the HIP structure can significantly enhance gas diffusion. This work offers an avenue to design metal oxide catalysts for CO–DeNOx by effectively controlling the doping metal concentration and oxidation states of the active components.

Low-temperature Catalytic Reaction over Manganese-cerium Composite Oxide Supported on Titania

A series of catalysts of manganese-cerium (Mn-Ce) active components supported on TiO2 prepared through sol-gel process were used for low-temperature catalytic reduction of NO with ammonia as reductant. The catalysts were characterized by scanning electron microscopy (SEM) and X-ray diffraction (XRD). The results showed that the particle size of the catalysts is smaller and the active components are highly dispersed on the support. Doping Ce exhibited an inhibitory effect on the crystal transition of TiO2 from anatase to rutile phase. Furthermore, the TiO2 support got the entire anatase phase at 450°C, with an improved the property of the catalyst. The catalyst with the highest activity was obtained with a mass Ce(0.8)-Mn/TiO2 ratio of 0.15, andcalcinated at 450°C, providing 99.01% NO conversion at 140°C at a high space velocity of 67, 000 h-1. Withthe increasing of Ce-Mn loading amount and Ce/Mn molar ratio, the NO conversion increased firstly and then decreased. With the increasing of NH3/NO molar ratio in inlet flue gas, NO conversion increased firstly and then tended to be stable. .

Low-temperature catalytic reduction of NO by NH3 over vanadia-based nanoparticles prepared by flame-assisted spray pyrolysis: Influence of various supports

A series of V/CeO2, V/TiO2, V/Al2O3, V/ZrO2, V/CeO2–ZrO2, V/TiO2–Al2O3, and V/CeO2–Al2O3 metal oxide nanoparticles were synthesized by a one-step rapid FSP (flame spray pyrolysis) synthesis technique. Benefiting from the short residence time and high quenching rate during the single-step flame spray process, V4+, V3+ ions are successfully incorporated into the crystal lattice of various metal oxide supports. Our XRD, BET studies reveal that the V doping into Al2O3, Al2O3–TiO2, and CeO2–Al2O3 favors the formation of highly dispersed surface vanadia nanoparticles (5.8–9.4nm), whereas, the V doping into ZrO2, CeO2–ZrO2 and CeO2 led to the primary particle size (19–45.5nm, formation of bulk particles) growth and thus inhibition in the catalytic activity. It is remarkable to note that the average particle size (nm) of vanadia in our flame-made catalysts has direct relation with the SCR activity. As can be envisaged from XPS spectra, as-synthesized V/ZrO2 sample primarily consists of V5+ species due to the formation of ZrV2O7 solid solution as a result of zirconia migration into the V2O5 crystallites. Our XPS results imply that the formation of surface V2O3 species is improved enormously by the addition of Al2O3 (V3+/Vn+=0.36, 0.38, and 0.41 for V/TiO2–Al2O3, V/Al2O3, V/CeO2–Al2O3, respectively), whereas, the addition of TiO2 led to the formation of surface VO2 species (V4+/V5+=0.88, 1.57 for V/TiO2, V/TiO2–AlO3, respectively). Among all the catalysts, high surface (V3++V4+)/Vn+, and V4+/Vn+ concentrations were observed for the V/TiO2–Al2O3, V/Al2O3, V/CeO2–Al2O3, respectively. It is highly remarkable to note that the SCR performance of all the as-prepared catalysts is indeed correlated with the surface (V3++V4+)/Vn+, and V4+/V5+ concentrations. The reduction (H2-TPR) profiles reveal that the vanadium oxide reduction peak has shifted to much lower temperatures in Al-modified catalysts, indicating high reduction potential of the high-coverage VOx species. This is primarily due to the penetration of the active component into the pores of the support during the flame spray pyrolysis step itself, which in turn, results in a high dispersion of the active component on the support. Clearly, the close proximity of the support to these sites will mean that the support exerts some influence on the behavior of the oxygen species attached to the vanadium. The catalytic performance of various V/M′ (M′=Ce, Al, Ti, Zr, Ce–Zr, Ti–Al, and Ce–Al) flame-made catalysts (with consistent V content V/M′=0.17) was studied for the low-temperature SCR reaction at a range of temperatures (140–360°C) at gas hourly space velocity (GHSV)=24,000h−1. The intrinsic activity of V/Ti–Al, V/Al, V/Ce–Al catalysts with V/M′=0.17 atomic ratio measured under differential reaction conditions, was found to be highly active, selective toward nitrogen and broadening the temperature window for optimal operation of this reaction.