Catalytic Reduction of NO with NH3 over V2O5-MnOX/TiO2-Carbon Nanotube Composites

Highly dispersed MnOx–FeOx supported by silicalite-1 for the selective catalytic reduction of NOx with NH3 at low temperatures

MnO_x–FeO_x-Loaded silicalite-1 catalysts exhibit high NO_x conversion at low temperatures.

Gaseous Heterogeneous Catalytic Reactions over Mn-Based Oxides for Environmental Applications: A Critical Review

Manganese oxide has been recognized as one of the most promising gaseous heterogeneous catalysts due to its low cost, environmental friendliness, and high catalytic oxidation performance. Mn-based oxides can be classified into four types: (1) single manganese oxide (MnOx), (2) supported manganese oxide (MnOx/support), (3) composite manganese oxides (MnOx-X), and (4) special crystalline manganese oxides (S-MnOx). These Mn-based oxides have been widely used as catalysts for the elimination of gaseous pollutants. This review aims to describe the environmental applications of these manganese oxides and provide perspectives. It gives detailed descriptions of environmental applications of the selective catalytic reduction of NOx with NH₃, the catalytic combustion of volatile organic compounds, Hg⁰ oxidation and adsorption, and soot oxidation, in addition to some other environmental applications. Furthermore, this review mainly focuses on the effects of structure, morphology, and modified elements and on the role of catalyst supports in gaseous heterogeneous catalytic reactions. Finally, future research directions for developing manganese oxide catalysts are proposed.

Uniformly active phase loaded selective catalytic reduction catalysts (V2O5/TNTs) with superior alkaline resistance performance

In this work, protonated titanate nanotubes was performed as a potential useful support and different vanadium precursors (NH₄VO₃ and VOSO₄) were used to synthesize deNO_x catalysts. The results showed that VOSO₄ exhibited better synergistic effect with titanate nanotubes than NH₄VO₃, which was caused by the ion-exchange reaction. Then high loading content of vanadium, uniformly active phase distribution, better dispersion of vanadium, more acid sites, better V⁵⁺/V⁴⁺ redox cycles and superior oxygen mobility were achieved. Besides, VOSO₄-based titanate nanotubes catalysts also showed enhanced alkaline resistance than particles (P25) based catalysts. It was strongly associated with its abundant acid sites, large surface area, flexible redox cycles and oxygen transfer ability. For the loading on protonated titanate nanotubes, active metal with cation groups was better precursors than anion ones. V₂O₅/TNTs catalyst was a promising substitute for the commercial vanadium catalysts and the work conducted herein provided a useful idea to design uniformly active phase loaded catalyst.

Low-Temperature Catalytic Decomposition of 130 Tetra- to Octa-PCDD/Fs Congeners over CuOX and MnOX Modified V2O5/TiO2-CNTs with the Assistance of O3

In this study, a reliable and steady PCDD/F generation system was utilized to investigate the performance of catalysts, in which 130 congeners of tetra- to octapolychlorinated dibenzo-p-dioxins and dibenzofurans (PCDD/Fs) vapors were studied under simulated flue gas with/without O₃. TiO₂ and carbon nanotubes (CNTs) supported vanadium oxides (VO_X/TiO₂-CNTs) modified with MnO_X and CuO_X, which were reported to be beneficial to the decomposition of model molecules, were found to have a negative effect on the removal of real PCDD/Fs in the simulated flue gas without O₃. Moreover, the addition of MnO_X presented different effects depending on whether CuO_X existed in catalysts or not, which was also contrary to its effects on the degradation of model molecules. In an O₃-containing atmosphere, low chlorination level PCDD/Fs congeners were removed well over VO_X-MnO_X/TiO₂-CNTs, while high chlorination level PCDD/Fs congeners were removed well over VO_X-CuO_X/TiO₂-CNTs. Fortunately, all PCDD/Fs congeners decomposed well over VO_X-MnO_X-CuO_X/TiO₂-CNTs. Finally, the effects of tetra- to octachlorination level for the adsorption and degradation behaviors of PCDD/Fs congeners were also investigated.

Selective catalytic reduction of NO by NH3 over CuO–CeO2 in the presence of SO2

The reaction between NO₂ and NH₃/NH₄⁺ induced the formation of NH_X<3 species with high oxidability; NH_X<3 promoted the surface sulfate decomposition; high de-NO_X performance was achieved in the presence of SO₂ at low temperature.

Mechanistic study of selective catalytic reduction of NO with NH3 over highly dispersed Fe2O3 loaded on Fe-ZSM-5

Highly dispersed Fe_xO_y clusters loaded on Fe-ZSM-5 with a Fe³⁺ concentration up to 22 wt% promoted the de-NO_X activity with an efficiency of 91%. The reaction route was temperature dependent.

Effect of preparation methods on the activity of VOx/CeO2 catalysts for the selective catalytic reduction of NOx with NH3

VO_x/CeO₂ catalysts prepared by a homogeneous precipitation method exhibited high NO_x conversion and strong SO₂ resistance in NH₃-SCR reaction.

Influence of hexagonal boron nitride on the selective catalytic reduction of NO with NH3over CuOX/TiO2

hBN promoted NO conversion over CuO_X/TiO₂, hBN promoted the oxidation of NO to NO₂, hBN suppressed the NH₃oxidation, a de-NO_Xactivity of 90.6% was achieved at 275 °C and SO₂promoted the activity at 350 °C.

Low temperature chlorobenzene catalytic oxidation over MnOx/CNTs with the assistance of ozone

O₃ promotes chlorobenzene catalytic oxidation over p-type MnO_x/CNTs between 80–240 °C. A CB complete oxidation of 95% is achieved below 120 °C. The reaction follows the L–H mechanism with apparent activation energy of 15.0 kJ mol⁻¹.