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.

The synthesis of dimethyl carbonate (DMC) from CO2 and methanol by Zr-doped CeO2 nanorods with different ratios of Zr/Ce has been studied at 6.8 MPa and 140 °C. The catalysts were characterized ext...

Oxygen Vacancy Promoting Dimethyl Carbonate Synthesis from CO2 and Methanol over Zr-Doped CeO2 Nanorods

Four different types of amine-attached MCM-48 silicas were prepared and investigated for CO(2) separation from N(2). Monomeric and polymeric hindered and unhindered amines were attached to the pore surface of the MCM-48 silica and characterized with respect to their CO(2) sorption properties. The pore structures and amino group content in these modified silicas were investigated by XRD, FT-IR, TGA, N(2) adsorption/desorption at 77 K and CHN/Si analysis, which confirmed that in all cases the amino groups were attached to the pore surface of MCM-48 at 1.5-5.2 mmol/g. The N(2) adsorption/desorption analysis showed a considerable decrease of the pore volume and surface area for the MCM-48 silica containing a polymeric amine (e.g., polyethyleneimine). The CO(2) adsorption rates and capacities of the amine-attached MCM-48 samples were studied employing a sorption microbalance. The results obtained indicated that in addition to the concentration of surface-attached amino groups, specific interactions between CO(2) and the surface amino groups, and the resultant pore structure after amine group attachment have a significant impact on CO(2) adsorption properties of these promising adsorbent materials.

Tailoring pore properties of MCM-48 silica for selective adsorption of CO2

Hierarchical zeolites combine the intrinsic catalytic properties of microporous zeolites and the enhanced access and transport of the additional meso- and/or macroporous system. These materials are the most desirable catalysts and sorbents for industry and become a highly evolving field of important current interests. In addition to the enhanced mass transfer leading to high activity, selectivity, and cycle time, another essential merit of the hierarchical structure in zeolite materials is that it can significantly improve the utilization effectiveness of zeolite materials resulting in the minimum energy, time, and raw materials consumption. Substantial progress has been made in the synthesis, characterization, and application of hierarchical zeolites. Herein, we provide an overview of recent achievements in the field, highlighting the significant progress in the past decade on the development of novel and remarkable strategies to create an additional pore system in zeolites. The most innovative synthesis approaches are reviewed according to the principle, versatility, effectiveness, and degree of reality while establishing a firm link between the preparation route and the resultant hierarchical pore quality in zeolites. Zeolites with different hierarchically porous structures, i.e., micro-mesoporous structure, micro-macroporous structure, and micro-meso-macroporous structure, are then analyzed in detail with concrete examples to illustrate their benefits and their fabrications. The significantly improved performances in catalytic, environmental, and biological applications resulting from enhanced mass transport properties are discussed through a series of representative cases. In the concluding part, we envision the emergence of "material-properties-by-quantitative and real rational design" based on the "generalized Murray's Law" that enables the predictable and controlled productions of bioinspired hierarchically structured zeolites. This Review is expected to attract important interests from catalysis, separation, environment, advanced materials, and chemical engineering fields as well as biomedicine for artificial organ and drug delivery systems.

Hierarchically Structured Zeolites: From Design to Application.

A recent report from the United Nations has warned about the excessive CO2 emissions and the necessity of making efforts to keep the increase in global temperature below 2 °C. Current CO2 capture t...

Trends in Solid Adsorbent Materials Development for CO2 Capture

Precisely fabricating Ce-O-Ti structure to enhance performance of Ce-Ti based catalysts for selective catalytic reduction of NO with NH3

Hierarchical porous ZSM-5 (HP-ZSM-5) was constructed using organosilanes as the growth inhibitors for CO2 capture. The properties of adsorbents were characterized by X-ray diffraction, N2 adsorption/desorption, scanning electron microscopy, temperature-programmed desorption of carbon dioxide, and 27Al magic angle spinning nuclear magnetic resonance. It was found that HP-ZSM-5 samples synthesized by organosilanes had a significant effect on the microstructure and morphology. CO2 adsorption capacity of HP-ZSM-5 was up to 58.26 cm3 g–1 at 0 °C and 1 bar, significantly higher than that of the ZSM-5 sample. The effective improvement of CO2 adsorption performance mainly originated from the micro-/mesoporous composite structure and complex surface morphology, which can provide low-resistant pathways for CO2 through the porous network. Besides, in situ Fourier transform infrared spectroscopy was carried out to study the adsorption process on adsorbents, and the results indicated that a faster physical adsorption ...

Enhanced CO2 Adsorption Performance on Hierarchical Porous ZSM-5 Zeolite

Construction of uniform nanodots CeO2 stabilized by porous silica matrix for 1,2-dichloroethane catalytic combustion

Mesoporous Mn–Ti amorphous oxides: a robust low-temperature NH3-SCR catalyst

CexZr1–xO2 oxides prepared by a soft reactive grinding (SRG) procedure have been investigated as the catalysts for HCl oxidation. The results show that the catalytic activities and stabilities of CexZr1–xO2 oxides are remarkably dependent on the Ce/Zr ratio. A correlation between the physicochemical properties and catalytic performances of these samples reveals that the cubic phase in CexZr1–xO2 with higher oxygen storage capacity (OSC) is more active for HCl oxidation, but the tetragonal phase is crucial to the stability of the catalysts. The Ce0.5Zr0.5O2 catalyst with mixed phases and the highest OSC (80 μmolO2·gcat–1) exhibits an excellent activity (1.89 gCl2·gcat–1·h–1 at 430 °C) and stability (300 h) in the target reaction. Kinetic studies show that both O2 and HCl competed for the active sites rendering desorption of surface Cl as the rate-determining step. Accelerating the replacement of surface Cl by O2 is essential for improving the activity of Ce0.5Zr0.5O2.

Cui Mifen

Papers

Precisely fabricating Ce-O-Ti structure to enhance performance of Ce-Ti based catalysts for selective catalytic reduction of NO with NH3

Enhanced CO2 Adsorption Performance on Hierarchical Porous ZSM-5 Zeolite

Construction of uniform nanodots CeO2 stabilized by porous silica matrix for 1,2-dichloroethane catalytic combustion

Mesoporous Mn–Ti amorphous oxides: a robust low-temperature NH3-SCR catalyst

HCl Oxidation for Sustainable Cl2 Recycle over the CexZr1–xO2 Catalysts: Effects of Ce/Zr Ratio on Activity and Stability