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The effective catalytic activity of hydrostannation of internal and terminal alkynes has been developed by using aluminum complexes. A novel aluminum complex L1AlMe2 was synthesized and characterized. N‐coordinated aluminum complex LAlH2 was chosen to be the most desirable catalyst. Under relatively mild and solvent‐free conditions, excellent yields, regio‐ and stereoselectivities have been achieved. Possible mechanistic pathways for the formation of major products by hydrostannation of alkynes with HSnBu3 were proposed. [ABSTRACT FROM AUTHOR]

Modulating the physicochemical properties of catalysts through the construction of special crystal structures or microscopic morphology provides new insights for developing high-performance low-temperature denitrification catalysts. This paper explores the effect of morphology structure on catalyst performance and identifies the dominant driving factors. The catalyst activity sequence was found to be MnO x spiny nanospheres (Mn-SNS) > MnO x nanowires (Mn-N) > MnO x nanospheres (Mn-NS) > MnO x nanoparticles (Mn-P). Among these, the Mn-SNS catalyst prepared by the hydrothermal method exhibited the best catalytic activity and the good resistance to water and sulfur. It achieved over 70% NO x conversion at 150 °C, and maintained 100% at 200–350 °C. In the presence of SO 2 and H 2 O, the NO x conversion was maintained at 87%. The spherical structure consisting of nanospikes provides the Mn-SNS catalysts with a large specific surface area, more (Mn4++Mn3+), abundant acid sites, and stronger reducibility, thus exhibiting excellent performance through the "fast-SCR" pathway. It also inhibits oxide crystallization and provides more sites for the adsorption activation of NO x and NH 3. The nanowire structures can provide a large specific surface area and a high concentration of Mn3+ and Mn4+ for MnO x catalyst. Characterization analyses revealed that the specific surface area, the ratio of (Mn4++Mn3+)/Mn, and the number of Lewis acid sites (L-NH 3) are the most important factors affecting the catalytic activity. This present empirical analysis provides new ideas for designing high-performance catalysts with a large specific surface area. [Display omitted] [ABSTRACT FROM AUTHOR]

[Display omitted] Improving the SO 2 resistance of catalysts is crucial to driving commercial applications of Mn-based catalysts. In this work, the phosphotungstic acid (HPW) modification strategy was applied to improve the N 2 selectivity, SO 2 and H 2 O resistance of the Mn-Ce-Co catalyst, and further, the mechanism of HWP modification on enhanced catalytic performance was explored. The results showed that HPW-Mn-Ce-Co catalyst exhibits higher NO x conversion (~100% at 100–250 °C) and N 2 selectivity (exceed 80% at 50–350 °C) due to more oxygen vacancies, greater surface acidity, and lower redox capacity. In situ diffused reflectance infrared Fourier transform spectroscopy (in situ DRIFTS) reveal that HPW changed the reaction path of Mn-Ce-Co catalysts, promoted the adsorption and activation of NH 3 , and reduced the effect of SO 2 on the active bidentate nitrate species, and thereby exhibiting good SO 2 resistance. X-ray photoelectron spectrometer (XPS) and NH 3 temperature-programmed desorption of (NH 3 -TPD) results show that HPW can inhibit the formation of metal sulfate, and SO 2 can be combined with Ce species more easily. The generated Ce 2 (SO 3) 3 can not only protect Mn species but also increase the acid sites and weaken the poisoning effect of metal sulfate. This study provides a simple design strategy for the catalyst to improve the low-temperature catalytic performance and toxicity resistance. [ABSTRACT FROM AUTHOR]

BACKGROUND: Nitrogen oxide (NOx) is one of the important atmospheric pollutants, causing damage to the environment and the human body. Currently, selective catalytic reduction (SCR) technology is the main denitration method, and SCR catalyst is the key to this technology. Iron (Fe)‐based catalysts have recently been widely studied because of their low cost and good catalytic effect on medium and low temperature effects. In this article, iron‐cerium mixed oxide (FeOx‐CeO2) catalysts were prepared by five common preparation methods, and their physicochemical properties and low temperature NH3‐SCR catalytic activity were studied. RESULTS: The results show that the preparation method has a certain influence on the catalytic performance [activity and nitrogen (N2) selectivity] of the catalyst. The order of activity is microemulsion method (MM) ≈ sol–gel (SG) method > coprecipitation method > hydrothermal synthesis method > solid‐phase mixing (SPM) method. CONCLUSION: This result is related to the specific surface area of the catalyst, the microstructure, the valence distribution of the elements, the redox ability and the surface acidic sites. It is worth noting that the activity of the catalyst prepared by the SG method is good, but the selectivity of N2 is poor, which is related to the oxidizing ability of the catalyst. The catalyst prepared by the MM has moderate oxidizing ability and large specific surface area, provides abundant acidic sites and has excellent catalytic performance. © 2019 Society of Chemical Industry [ABSTRACT FROM AUTHOR]

Mn-Fe-CeOx-Al 2 O 3 /HCM catalyst have the potential advantages of good catalytic activity, appropriate production process and moderate shedding rate with shedding modes of internal and interface spalling, comparing to the Mn-Fe-CeOx/Al 2 O 3 /HCM sample. • Mn-Fe-CeOx-Al 2 O 3 /HCM, Mn-Fe-CeOx/Al 2 O 3 /HCM and Mn-Fe-CeOx/HCM were compared for NO oxidation. • Al 2 O 3 -coatings increased surface area and active-components loadings for better enhancement. • Mn-Fe-CeOx-Al 2 O 3 /HCM have good catalytic activity, appropriate production process and moderate shedding rate. • Promoted NO-to-NO 2 via intermediate nitrate-species were benefited from more active oxygen. • Mn-Fe synergetic interaction and Ce-accelerated electron cycles were favorable for catalytic activity. Mn-Fe-Ce multiple oxides with Al 2 O 3 coating supported over honeycomb cordierite monoliths including Mn-Fe-CeOx/Al 2 O 3 /HCM and Mn-Fe-CeOx-Al 2 O 3 /HCM were optimized and compared for the catalytic oxidation of NO. The addition of Al 2 O 3 -coatings increased the specific surface area for more loadings of active components and also making the distribution of active species more uniform. Pseudo-boehmite as coating showed a better enhancement on NO oxidation than nano-Al 2 O 3 coating directly. Whatever Mn-Fe-CeOx/Al 2 O 3 /HCM prepared by sol-gel and impregnation methods or Mn-Fe-CeOx-Al 2 O 3 /HCM prepared by slurry coating of co-precipitated Mn-Fe-CeOx powders and pseudo-boehmite binders onto HCM, the optimized doping amounts of Mn-Fe-CeOx was 15 wt. % with 10 wt. % Al 2 O 3 for good activity than the impregnated Mn-Fe-CeOx/HCM without Al 2 O 3 -coatings. H 2 -TPR, SEM, XPS, NO + O 2 -TPD and DRIFTS characterizations showed that the promoted catalytic oxidation activity of NO-to-NO 2 via the intermediate nitrate-species over Mn-Fe-CeOx/Al 2 O 3 /HCM and Mn-Fe-CeOx-Al 2 O 3 /HCM were benefited from more surface concentrations of active oxygen, efficient synergetic interaction between Fe and Mn ions (Fe2+ + Mn4+ ↔ Mn3+ + Fe3+) and high oxidizing ability accelerated by high Ce4+/Ce3+ ratio. Mn-Fe-CeOx-Al 2 O 3 /HCM catalyst have the potential advantages of good catalytic activity (74.4 % NO conversion at 250 °C) and appropriate production process (3−4 days of preparation period), which also gave the moderate shedding rate with the shedding modes of internal spalling and interface spalling than Mn-Fe-CeOx/Al 2 O 3 /HCM sample. [ABSTRACT FROM AUTHOR]

Developing effective and stable catalysts for low-temperature selective catalytic reduction (SCR) of NO x remains challenging. Herein, we constructed a hierarchical structure by loading CoMn 2 O 4 onto Ti-doped CeO 2 , that CoMn 2 O 4 /CeTiO x catalyst has shown superior deNO x activity (>95% at 100–225 °C), prominent reaction activation energy (28.8 ± 0.9 kJ mol−1) and outstanding stability (>75% at 100–200 °C within H 2 O and SO 2). The "low-temperature active sites" and "dual anti-poisoning sites" contribute to excellent activity and stability. Firstly, the hierarchical structure boosts generation of active metal-support interface, which is conducive to oxygen migration (including adsorbed oxygen (O ads), lattice oxygen (O lat) and oxygen vacancy (O v)) and metal charge transfer (Mn2+/3++Ce4+↔Mn3+/4++Ce3+, Ti4++Ce3+↔Ce4++Ti3+). This is the key to breaking through the limits of catalytic activity stability. Secondly, enhanced surface acidity favors NH 3 adsorption and activation, which accelerates -NH 2 /-NH concatenate with NO x through Eley-Rideal mechanism to generate N 2 and H 2 O. Thirdly, the dual strong SO 2 affinity sites by Ti-induced CeO 2 crystal reconstruction retard the active center affected by the sulfate species, which contributes to striking stability. This work highlights the importance of design of isolated active sites to improve SO 2 and H 2 O endurance. [Display omitted] • The CoMn 2 O 4 /CeTiOx catalyst exhibited excellent low-temperature SCR performance. • The CoMn 2 O 4 /CeTiOx catalyst took on a superior endurance to water and sulfur volatility at low-temperature. • The existence of cooperative interface of metal-support promotes electron cycling and reaction gas adsorption activation. • The supported catalysts were dominated by Eley-Rideal mechanism which was less effected by SO 2. • The presence of dual sacrifice sites delayed the deactivation of low-temperature active components. [ABSTRACT FROM AUTHOR]