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.

Selective catalytic reduction (SCR) technology has been widely used for the removal of NOx from flue gas. However, it is still a challenge to develop novel low-temperature catalysts for SCR of NOx, especially at temperatures below 200 °C. This paper reviewed the recent progress on the Mn-based catalysts for low-temperature SCR de-NOx with NH3. Catalysts were divided into four categories, single MnOx, Mn-based multi-metal oxide, Mn-based multi-metal oxide with support, and Mn-based monolith catalyst. In the section of single MnOx, the effects of several factors, such as Mn oxidation state, crystallization state, specific surface area and morphology on catalytic activity were systematically reviewed. In the section of multi-metal oxide catalysts, the various roles played by the components of catalysts were intentionally summarized from four aspects, improving de-NOx efficiency, enhancing N2 selectivity, improving resistance to SO2 and H2O, extending operation temperature window, respectively. Moreover, the newly emerging morphology-dependent nanocatalysts were highlighted at the end of this section. In the introduction of supported metal oxide catalysts, the effects of supports were systematically analyzed according to their types, such as Al2O3, TiO2, carbon materials, etc. Considering the actual operation, Mn-based monolith catalysts were also introduced with regard to monolith supports, such as ceramics, metal wire mesh, etc. Subsequently, NH3-SCR mechanisms at low temperature, including E-R and L-H mechanisms, were discussed. At last, the perspective and the future direction of low-temperature SCR of NOx were proposed.

Manganese oxide-based catalysts for low-temperature selective catalytic reduction of NOx with NH3: A 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 rol...

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

Ceria-based catalysts for low-temperature selective catalytic reduction of NO with NH3

Copper-containing cerium oxide materials have received considerable attention both in catalysis and electro-catalysis fields due to their unique physicochemical characteristics in conjunction to their lower cost compared to noble metals (NMs)-based catalysts. Nowadays, it is well documented that the complex Copper–Ceria interactions (either geometric or electronic) have a key role on the catalytic performance. Hence, considerable efforts have been devoted on the understanding and the fine-tuning of metal–oxide interactions. Despite the growing progress in the field, several crucial issues related to the influence of: i) particle’s shape and size, ii) active site’s chemical state, iii) charge transfer between interfacial sites, and iv) intrinsic defects (e.g., surface oxygen vacancies) on the interfacial activity are still under investigation. This survey summarizes the recent advances in the last 10 years on the fundamental origin of Copper–Ceria interactions and their implications on the catalytic activity. The insights lately obtained by means of: i) ex situ advanced characterization techniques, ii) in situ sophisticated studies (e.g., operando techniques), iii) theoretical analysis (e.g., DFT calculations), and iv) innovative probing approaches (such as the inverse CeO2/CuO model system) are provided. The state-of-the-art catalytic applications of CuO/CeO2 binary oxides (water gas shift (WGS) reaction, preferential oxidation (PROX) of CO, CO2 hydrogenation, selective catalytic reduction (SCR), N2O decomposition, etc.) in relation to the aforementioned aspects are discussed. Some guidelines towards the fine-tuning of the surface chemistry of CuO/CeO2 catalysts for real life energy and environmental application are provided.

The role of Copper–Ceria interactions in catalysis science: Recent theoretical and experimental advances

Effect of preparation methods on the performance of CeO2/Al2O3 catalysts for selective catalytic reduction of NO with NH3

Effect of Cu doping on the SCR activity of CeO2 catalyst prepared by citric acid method

CeO-CuO catalysts were prepared by citric acid method at different calcination temperatures. The purpose of this study is to investigate the influence of calcination temperature on the catalytic activity of CeO2-CuO catalyst for the selective catalytic reduction of NO with NH3. As can be seen from the results, Ce-Cu(450) is of the best low temperature selective catalytic reduction (SCR) activity among the three catalysts, which may be resulted from its large surface area, good redox ability, strong NH3 adsorption capacity, and high concentration of Cu2+ and active oxygen species on the surface. © 2013 American Institute of Chemical Engineers Environ Prog, 33: 385–389, 2014

Influence of calcination temperature on CeO2-CuO catalyst for the selective catalytic reduction of NO with NH3

Effect of support on the performance of Mn–Cu oxides for low temperature selective catalytic reduction of NO with NH3

The invention discloses a heterogeneous Fenton reagent and a preparation method of the heterogeneous Fenton reagent and a method for removing NO out of smoke by wet oxidization by using the heterogeneous Fenton reagent The heterogeneous Fenton reagent is a mixed solution which comprises an H2O2 water solution and an Al2O3 loaded Fe catalyst and has a pH of 5-6, wherein the concentration of the H2O2 waters solution in the mixed solution is 05-15mol/L, and the concentration of the Al2O3 loaded Fe catalyst is 2g/L According to the method, NO is removed out of smoke by wet oxidization by using the heterogeneous Fenton reagent; particularly, the heterogeneous Fenton reagent is added in a conventional bubble tower, NO in the smoke is oxidized into HNO3, and thus the purpose of removing NO is reached The method for removing NO out of the smoke by wet oxidization by using the heterogeneous Fenton reagent is low in denitration cost and does not cause secondary pollution

Jie-nan Hong

Papers

Effect of preparation methods on the performance of CeO2/Al2O3 catalysts for selective catalytic reduction of NO with NH3

Effect of Cu doping on the SCR activity of CeO2 catalyst prepared by citric acid method

Influence of calcination temperature on CeO2-CuO catalyst for the selective catalytic reduction of NO with NH3

Effect of support on the performance of Mn–Cu oxides for low temperature selective catalytic reduction of NO with NH3

Heterogeneous Fenton reagent and preparation method and application thereof