Comparision on the Low-Temperature NH3-SCR Performance of γ-Fe2O3 Catalysts Prepared by Two Different Methods

Abstract

Maghemite (γ-Fe2O3) catalysts were prepared by two different methods, and their activities and selectivities for selective catalytic reduction of NO with NH3 were investigated. The methods of X-ray powder diffraction (XRD), Brunauer–Emmett–Teller (BET), X-ray photoelectron spectroscopy (XPS), hydrogen temperature-programmed reduction (H2-TPR), ammonia temperature-programmed desorption (NH3-TPD), transmission electron microscopy (TEM), Energy-dispersive X-ray spectroscopy (EDS), and in situ diffuse reflectance infrared Fourier transform spectroscopy (in situ DRIFTS) were used to characterize the catalysts. The resulted demonstrated that the γ-Fe2O3 nanoparticles prepared by the facile method (γ-Fe2O3–FM) not only exhibited better NH3-SCR activity and selectivity than the catalyst prepared by the coprecipitation method but also showed improved SO2 tolerance. This superior NH3-SCR performance was credited to the existence of the larger surface area, better pore structure, a high concentration of lattice oxygen and surface-adsorbed oxygen, good reducibility, a lot of acid sites, lower activation energy, adsorption of the reactants, and the existence of unstable nitrates on the surface of the γ-Fe2O3–FM.

Co3−xFexO4 inverse opals with tunable catalytic activity for high-performance overall water splitting

“…Peak positions and relative intensities of the pure Fe sample with diffraction peaks at 30.36°, 35.76°, 43.49°, and 57.29° are indexed to (220), (311), (400), and (511) crystalline planes of cubic spinel γ-Fe 2 O 3 maghemite (JCPDS No. 39-1346), 32 confirming that the main crystalline phase in Fe IO sample is γ-Fe 2 O 3 . Additional diffraction peaks at 2 θ equal to 24.2°, 33.0° and 41.2° coincide with the characteristic peaks of hematite α-Fe 2 O 3 (JCPDS No.…”

Lattice Oxygen Activation Triggered by Ultrasonic Shock Significantly Improves NO Selective Catalytic Reduction

“…According to the literature reports, the H 2 consumption at high temperature is a direct result of reaction with lattice oxygen . Thus, the two high temperature peaks at regions of 350–400 and 500–600 °C can be ascribed to reduction of surface lattice oxygen and bulk lattice oxygen, respectively . It is obvious that after ultrasonic treatment, the profile of α-Fe 2 O 3 exhibited a significant shift to lower temperature, verifying the great promotion of lattice oxygen diffusion due to generation of bulk defects .…”

“…34 Thus, the two high temperature peaks at regions of 350−400 and 500−600 °C can be ascribed to reduction of surface lattice oxygen and bulk lattice oxygen, respectively. 35 It is obvious that after ultrasonic treatment, the profile of α-Fe 2 O 3 exhibited a significant shift to lower temperature, verifying the great promotion of lattice oxygen diffusion due to generation of bulk defects. 20 Meanwhile, according to the quantitative analysis results in Table S2, UT-Fe 2 O 3 shows a hydrogen consumption that is smaller than that of P-Fe 2 O 3 , which can be reasonably attributed to the partial loss of lattice oxygen.…”

Coupling acid catalysis and selective oxidation over MoO3-Fe2O3 for chemical looping oxidative dehydrogenation of propane

“…5a , FeAl sample presented two typical reduction peaks as pure γ-Fe 2 O 3 at 350 °C and 560 °C respectively. The reduction peak at 350 °C was corresponding to the reduction of γ-Fe 2 O 3 to Fe 3 O 4 , while the peak at 560 °C was the integrated results for the reduction of Fe 3 O 4 to FeO and FeO to Fe 58 – 61 . For 1MoxFeAl redox catalysts, the temperature for the first reduction peak was gradually increased with Mo content, and the asymmetric peak could be resolved into pairs (O α and O β ).…”