Mengfei Luo

Reduction property and catalytic activity of Ce1−XNiXO2 mixed oxide catalysts for CH4 oxidation

Abstract Ce 1− X Ni X O 2 oxides with X varying from 0.05 to 0.5 were prepared by different methods and characterized by XRD and TPR techniques. Ce 0.7 Ni 0.3 O 2 sample prepared by sol–gel method shows the highest reducibility and the highest catalytic activity for methane combustion. Three kinds of Ni phases co-exist in the Ce 1− X Ni X O 2 catalysts prepared by sol–gel method: (i) aggregated NiO on the support CeO 2 , (ii) highly dispersed NiO with strong interaction with CeO 2 and (iii) Ni atoms incorporated into CeO 2 lattice. The distribution of different Ni species strongly depends on the preparation methods. The highly dispersed NiO shows the highest activity for methane combustion. The NiO aggregated on the support CeO 2 shows lower catalytic activity for methane combustion, while the least catalytic activity is found for the Ni species incorporated into CeO 2 . Any oxygen vacancy formed in CeO 2 lattice due to the incorporating of Ni atoms adsorbs and activates the molecular oxygen to form active oxygen species. So the highest catalytic activity for methane combustion on Ce 0.7 Ni 0.3 O 2 catalyst is attributed not only to the highly dispersed Ni species but also to the more active oxygen species formed.

Epoxidation of propylene on NaCl-modified silver catalysts with air as the oxidant

Propylene epoxidation by air was carried out on nacl-modified silver (nacl/ag) catalysts, and the catalysts were characterized by x-ray diffraction (xrd) and x-ray photoelectron spectroscopy (xps). the effects of nacl loadings, propylene to oxygen ratio, and the reaction time on the catalytic performance were investigated. it was found that the addition of nacl to silver significantly increases the propylene oxide (po) selectivity. the po yield has a maximum when the nacl loading is about 10 wt.%. also 12.4% conversion of propylene and 31.6% selectivity to po are obtained on the nacl/ag (10 wt.%) catalyst at 350 degreesc, space velocity 1.8 x 10(4) h(-1) and c3h6:o-2 = 1:2. xps and xrd characterizations show that agcl formed on the silver catalyst was favorable to propylene epoxidation. a compound with highly oxidized ag ion was also found, which may be effective for the reaction. (c) 2002 elsevier science b.v. all rights reserved.

Epoxidation of Propylene over Ag-CuCl Catalysts Using Air as the Oxidant

Ag-CuCl catalysts were found to be active and selective for the epoxidation of propylene using air as the oxidant. Ag catalyst gives a propylene conversion of 31.6%, with a propylene oxide (PO) selectivity of 0.42% at a reaction temperature of 350 °C after 220 min of reaction. Addition of CuCl significantly improves the selectivity to PO, and suppresses the conversion of propylene. The Ag-CuCl (1/0.6) catalyst gives propylene conversion of about 3% and a PO selectivity of about 30% at a reaction temperature of 350 °C after 500 min of reaction. The activity of the Ag-CuCl catalyst increases with the reaction time and the selectivity to PO is very stable for this catalyst. It is found that AgCl and CuO phases formed during the catalyst preparation are beneficial to the epoxidation of propylene.