Catalytic reduction of NO with NH3 over carbons impregnated with Cu and Fe

New insight into electrochemical denitrification using a self-organized nanoporous VO-Co3O4/Co cathode: Plasma-assistant oxygen vacancies catalyzed efficient nitrate reduction

A novel self-organized nanoporous V_O-Co₃O₄/Co cathode was prepared via anodization and plasma treatment and obtained a significant nitrate reduction efficiency. In the anodization, an oxide layer with the nano-sized pore structure initially grew in-situ on the Co substrate and showed a better surface area. Subsequently, He-plasma increased surface oxygen vacancies (V_O) from 24 % to 57 %. Electrons in vacancies were charged into empty e_g orbital of low-spin Co³⁺(O_h, octahedral) and firstly generated high-spin Co²⁺(O_h) with the configuration of t_2g⁶e_g¹, accounting for 71.7 % of cobalt species. Accordingly, two original mechanisms (Vo-catalyzed and Co²⁺(O_h)-catalyzed) were concluded in this study. Oxygen vacancies increased the charge intensity and served as absorption sites in nitrate reduction. Meanwhile, massive Co²⁺(O_h) provided electrons in the e_g orbital with a higher energy state and mediated the faster electron transfer through a Co²⁺-Co³⁺-Co²⁺ redox cycle, compared with Co²⁺ (T_d, tetrahedral). Ultimately, a faster reaction kinetic of 0.0220 min^-1 was achieved by V_O-Co₃O₄ than other cathodes e.g., Co₃O₄ (0.0150 min^-1). Such V_O-Co₃O₄/Co cathode-based denitrification strategy displayed great advantages in engineering application and completely removed 90 % of TN from actual wastewater.

Improved NO reduction by using metal-organic framework derived MnO x -ZnO

Derivatives based on metal frameworks (MOFs) are attracting more and more attention in various research fields. MOF-based derivatives x% MnO _x -ZnO are easily synthesized by the thermal decomposition of Mn/MOF-5 precursors. Multiple technological characterizations have been conducted to ascertain the strengthening interaction between Mn species (Mn²⁺ or Mn³⁺) and Zn²⁺ (e.g., XRD, FTIR, TG, XPS, SEM, H₂-TPR and Py-FTIR). The 5% MnO _x -ZnO exhibits the highest NO conversion of 75.5% under C₃H₆-SCR. In situ FTIR and NO-TPD analysis showed that monodentate nitrates, bidentate nitrates, bridged bidentate nitrates, nitrosyl groups and C _x H _y O _z species were formed on the surface, and further hydrocarbonates or carbonates were formed as intermediates, directly generating N₂, CO₂ and H₂O.

Enhancing low-temperature SCR de-NOx and alkali metal poisoning resistance of a 3Mn10Fe/Ni catalyst by adding Co

Alkaline K poisoned and Co-modified catalysts were prepared using Fe and Mn as active components, nickel foam as a carrier, and Co as a trace additive.

Synthesis of nanosphere TiO2 with flower-like micro-composition and its application for the selective catalytic reduction of NO with NH3 at low temperature

TiO₂ nanospheres consisting of flower-like nanopowders were synthesized by a solvothermal method, and Cu/TiO₂(T) catalysts were prepared via an impregnation method.

Synthesis, characterization and catalytic performances of Cu- and Mn-containing ordered mesoporous carbons for the selective catalytic reduction of NO with NH3

The synergetic catalytic effect of Cu and Mn for CuxMny-OMCs catalysts on NO conversion with NH₃.

Rational design of 3D hierarchical foam-like Fe2O3@CuOxmonolith catalysts for selective catalytic reduction of NO with NH3

A high-performance monolith catalyst based on 3D hierarchical foam-like Fe₂O₃@CuO_xwas developed for selective catalytic reduction of NO.

Environmentally-benign catalysts for the selective catalytic reduction of NOxfrom diesel engines: structure–activity relationship and reaction mechanism aspects

The structure–activity relationship of vanadium-free NH₃-SCR catalysts and the HC-SCR reaction mechanism over the Ag/Al₂O₃catalyst are comprehensively summarized.

Structural Feature and Catalytic Performance of Cu Species Distributed over TiO2 Nanotubes

Copper oxide was deposited on tubular TiO2 via Cu2+ introduction into a titanate nanotube aggregate followed by calcination. The titanate has a layered structure allowing Cu intercalation and can readily transform into anatase TiO2 via calcination for condensation of the constituting layers. The activity of the tubular catalysts, with a Cu content of 2 wt %, in selective NO reduction with NH3 was compared with those of other 2 wt % Cu/TiO2 catalysts using TiO2 nanoparticles as the support. The Cu species supported on the nanotubes showed a higher activity than those supported on the nanoparticles. X-ray absorption near-edge structure (XANES) analysis showed that the Cu species on all the TiO2 supports are in the +2 state. Extended X-ray absorption fine structure (EXAFS) investigations of these catalysts reflected higher degrees of CuO dispersion and Cu2+ dissolution into the TiO2 lattice for the tubular Cu/TiO2 catalysts. Absence of CuO bulk detection by a temperature-programmed reduction analysis for the tubular catalysts confirmed the high CuO-dispersion feature of the tubular catalysts. The dissolution of Cu2+ to form a CuxTi1-xO2 type of solid solution was improved by using an in-situ ion-intercalation method for Cu deposition on the nanotubes. A fraction as high as 40% for Cu2+ dissolution was obtained for the tubular catalysts while only 20% was obtained for the particulate catalysts. The CuxTi1-xO2 species were considered one form of the active sites on the Cu/TiO2 catalysts.

Nitrous oxide emissions from waste incineration

EU energy and environmental policy in waste management leads to increasing interest in developing methods for waste disposal with minimum emissions of greenhouse gases and minimum environmental impacts.

From the point of view of nitrous oxide (N2O) emissions, waste incineration and waste co-combustion is very acceptable method of waste disposal. Two factors are important for attaining very low N2O emissions from waste incineration, particularly for waste with higher nitrogen content (e.g. sewage sludge, leather, etc.): temperature of incineration over 900°C and avoiding selective noncatalytic reduction (SNCR) de-NOx method based on urea. For reduction of N2O emissions retrofitting such plants to ammonia-based SNCR is recommendable. The modern selective catalytic reduction facilities for de-NOx at waste incineration plants are only negligible source of N2O.

Nitrous oxide (N2O) emissions from waste and biomass to energy plants

Following the Kyoto protocol with respect to reducing emissions of greenhouse gases emissions, and EU energy policy and sustainability in waste management, there has been an increased interest in the reduction of emissions from waste disposal operations. From the point of view of nitrous oxide (N2O) emissions, waste incineration and waste co-combustion are very acceptable methods for waste disposal. In order to achieve very low N2O emissions from waste incineration, particularly for waste with higher nitrogen content (e.g. sewage sludge), two factors are important: temperature of incineration over 900 degrees C and avoiding the selective non-catalytic reduction (SNCR) de-NO(X) method based on urea or ammonia treatments. The more modern selective catalytic reduction (SCR) systems for de-NO(X) give rise to negligible sources of N2O.