Potassium poisoning impact on FeCu selective catalytic reduction catalyst: Structure and mechanism

Alkali metals bring great challenges to the elimination of NOx from stationary emissions in the selective catalytic reduction (SCR) reaction. The FeCu catalyst, as an eco-friendly and high-efficiency catalyst for NOx removal possesses wide application prospects. However, the poisoning effect of potassium is not clear. Therefore, the potassium poisoning catalyst was obtained by the wet impregnation means. The XRD, H2-TPR, NH3-TPD, XPS and DRIFT technologies were performed to study the influence of K poisoning. The results indicate that potassium causes damage to Cu-O-Fe construction. Then the Cu2+ in lattice of Fe2O3 separate out from Fe2O3 and form CuO which leads to the decline of acid sites and excessive NH3 oxidation. And it finally leads to the catalyst deactivation. After K poisoning, NO2, monodentate nitrates and nitrites cannot generate. Only bidentate nitrates can generate and then react with NH3 species on the Lewis acid sites to produce H2O and N2. Hence, the reaction rate has a slide

Enhanced CO oxidation reaction over Pt nanoparticles covered with ultrathin graphitic layers

It has been empirically established that graphitic carbon deposits often result in deactivation of metal catalysts due to the physical blockage of surface active sites. Our recent surface science works however demonstrate that molecules such as CO can adsorb on Pt(111) surface covered by graphene overlayers via an intercalation process, and surface reactions e.g. CO oxidation have been enhanced by the graphene covers. In this work, supported Pt nanocatalysts were coated by ultrathin graphitic carbon layers through chemical vapor deposition process forming Pt@C core-shell nanostructures, which were confirmed by characterizations of Raman spectroscopy, temperature-programmed oxidation and transmission electron microscopy. CO oxidation over the Pt@C catalysts shows a lower apparent activation energy compared with the pure Pt catalysts, and in-situ infrared studies indicate that the reactions occur under the graphitic shells. The present results suggest that coating metal nanocatalysts with ultrathin graphitic overlayers may be used to promote metal catalyzed reactions. (C) 2016 Elsevier Ltd. All rights reserved

Dynamic structural changes of perovskite-supported metal catalysts during cyclic redox treatments and effect on catalytic CO oxidation

CaTiO3-and BaTiO3-supported Ag and Pt catalysts were subjected to cyclic oxidation and reduction treatments and their surface structures were investigated using X-ray diffraction (XRD) and X-ray photoelectron spectroscopy (XPS). The CO oxidation reactions over the Ag and Pt catalysts showed that the oxidized Ag/oxide catalysts performed better in CO oxidation than the reduced ones did, whereas the reduced Pt/oxide catalysts had higher CO oxidation activity than that after oxidation treatment. The XRD and XPS measurements revealed that the oxidation treatment helped to improve the dispersion of Ag nanoparticles, but their metallic state was retained, which enhanced CO oxidation. In contrast, the surfaces of the Pt nanoparticles were dominated by PtO2 after the oxidation treatment, which lowered the CO oxidation activity compared with that of the reduced Pt catalyst. (C) 2013, Dalian Institute of Chemical Physics, Chinese Academy of Sciences. Published by Elsevier B.V. All rights reserved

Selective oxidation of cyclopentene to glutaraldehyde over the WO3/SiO2 catalyst

The WO3/SiO2 catalyst was prepared by sonication-impregnation combination approach using commercial silica gel as support. Influences of various factors on the yield of glutaraldehyde, such as WO3 loading and calcination temperature, were investigated and discussed in terms of the characterizations results of BET, XRD, Raman, FT-IR and XPS. It was found that the yield of glutaraldehyde increased rapidly with increase of WO3 loadings and calcination temperatures while WO3 was in the amorphous state, which reached the maximum value when amorphous WO3 started transforming into the crystalline form. Whereas, the yield of glutaradehyde decreased with further increase of WO3 loadings and calcination temperatures while WO3 has already transformed into the crystalline form. It is concluded that the formation of crystalline WO3 species and the interaction of WO3 with SiO2 play a key role for improving the activity of the WO3/SiO2 catalyst. (C) 2008 Elsevier B.V. All rights reserved

Investigation of CO and formaldehyde oxidation over mesoporous Ag/Co3O4 catalysts

CO and formaldehyde (HCHO) oxidation reactions were investigated over mesoporous Ag/Co3O4 catalysts prepared by one-pot (OP) and impregnation (IM) methods. It was found that the one-pot method was superior to the impregnation method for synthesizing Ag/Co3O4 catalysts with high activity for both reactions. It was also found that the catalytic behavior of mesoporous Co3O4 and Ag/Co3O4 catalysts for the both reactions was different. And the addition of silver on mesoporous Co3O4 did not always enhance the catalytic activity of final catalyst for CO oxidation at room temperature (20 degrees C), but could significantly improve the catalytic activity of final catalyst for HCHO oxidation at low temperature (90 degrees C). The high surface area, uniform pore structure and the pretty good dispersion degree of the silver particle should be responsible for the excellent low-temperature CO oxidation activity. However, for HCHO oxidation, the addition of silver played an important role in the activity enhancement. And the silver particle size and the reducibility of Co3O4 should be indispensable for the high activity of HCHO oxidation at low temperature