Selective catalytic reduction with NH3 (NH3-SCR) is the most efficient technology to reduce the emission of nitrogen oxides (NOx) from coal-fired industries, diesel engines, etc. Although V2O5-WO3(MoO3)/TiO2 and CHA structured zeolite catalysts have been utilized in commercial applications, the increasing requirements for broad working temperature window, strong SO2/alkali/heavy metal-resistance, and high hydrothermal stability have stimulated the development of new-type NH3-SCR catalysts. This review summarizes the latest SCR reaction mechanisms and emerging poison-resistant mechanisms in the beginning and subsequently gives a comprehensive overview of newly developed SCR catalysts, including metal oxide catalysts ranging from VOx, MnOx, CeO2, and Fe2O3 to CuO based catalysts; acidic compound catalysts containing vanadate, phosphate and sulfate catalysts; ion exchanged zeolite catalysts such as Fe, Cu, Mn, etc. exchanged zeolite catalysts; monolith catalysts including extruded, washcoated, and metal-mesh/foam-based monolith catalysts. The challenges and opportunities for each type of catalysts are proposed while the effective strategies are summarized for enhancing the acidity/redox circle and poison-resistance through modification, creating novel nanostructures, exposing specific crystalline planes, constructing protective/sacrificial sites, etc. Some suggestions are given about future research directions that efforts should be made in. Hopefully, this review can bridge the gap between newly developed catalysts and practical requirements to realize their commercial applications in the near future.

Selective Catalytic Reduction of NOx with NH3 by Using Novel Catalysts: State of the Art and Future Prospects.

http://digitalknowledge.cput.ac.za/bitstream/11189/7476/1/A%20review%20on%20environmental%20monitoring%20of%20water.pdf

A review on environmental monitoring of water organic pollutants identified by EU guidelines

Results from direct and indirect measurements of cosmic rays are reviewed. Emphasis is given to the understanding of the knee in the energy spectrum. The data are compared to contemporary models for the knee. Implications on the present understanding of the origin of galactic cosmic rays are discussed.

On the knee in the energy spectrum of cosmic rays

The Sm doped CeO2-TiO2 mixed oxide catalyst, which exhibited excellent activity and tolerance to H2O and SO2 in the NH3-SCR reaction, was synthesized. The reasons for the high activity and SO2 resistance of the catalyst were investigated by a series of characterization. The H2-TPR and O2-TPD results suggested that the reducibility and oxygen storage capacity (OSC) of CeTi catalyst were promoted by the addition of Sm species, which was beneficial for improving the activity of catalyst. The in situ DRIFTS results revealed that the adsorptive ability of NOx species and activation ability of NH3 were enhanced by Sm doping, which was also propitious to enhance the activity. XPS combined with DFT calculated results confirmed that the transfer of electron by Sm2++Ce4+⇌Sm3++Ce3+ circles occurred in the SmCeTi catalyst. The redox circles may be the reason of the good SO2 tolerance of the SmCeTi catalyst, for which suppressed the electron transferring from adsorbed SO2 to Ce4+. Through in situ DRIFTS and TG-DSC results, it can be concluded that the sulphation of catalyst was lowered by samarium doping into CeTi catalyst. Consequently, the SmCeTi catalyst exhibited significant SO2 tolerance ability.

Improved activity and significant SO2 tolerance of samarium modified CeO2-TiO2 catalyst for NO selective catalytic reduction with NH3

Chlorinated paraffins in the environment: A review on their production, fate, levels and trends between 2010 and 2015.

WO3 promoted Mn–Zr mixed oxide catalyst for the selective catalytic reduction of NOx with NH3

Novel Fe–Ce–Ti catalyst with remarkable performance for the selective catalytic reduction of NOx by NH3

Characterization of the particle size fraction associated heavy metals in tropical arable soils from Hainan Island, China

Ni-Ce-Ti as a superior catalyst for the selective catalytic reduction of NOx with NH3

Pt/TiO2 and WO3 modified Pt/TiO2 catalysts have been investigated for the selective catalytic reduction of NOx by H2 (H2-SCR) in the presence of oxygen. It was found that the addition of WO3 leads to a significant promoting effect on the low-temperature activity of Pt/TiO2 catalyst and the optimal loading is 2%. X-ray absorption near-edge structure (XANES) revealed the electron transfer from WO3 to Pt active sites, leading to the formation of metallic Pt, which is responsible for the low-temperature H2-SCR of NOx. In-situ DRIFTS demonstrated that the introduction of WO3 to Pt catalyst not only contributes to the formation of reactive adsorbed NOx species on the catalyst, but also promotes the formation of NH4+ species. All of these factors, collectively, account for the improved low-temperature activity of Pt-WO3/TiO2 catalyst.

Lingling Ma

Papers

WO3 promoted Mn–Zr mixed oxide catalyst for the selective catalytic reduction of NOx with NH3

Novel Fe–Ce–Ti catalyst with remarkable performance for the selective catalytic reduction of NOx by NH3

Characterization of the particle size fraction associated heavy metals in tropical arable soils from Hainan Island, China

Ni-Ce-Ti as a superior catalyst for the selective catalytic reduction of NOx with NH3

Selective catalytic reduction of NOx with H2 over WO3 promoted Pt/TiO2 catalyst