Shuiju Wang

Magnesia-carbon nanotubes (MgO-CNTs) nanocomposite: novel support of Ru catalyst for the generation of COx-free hydrogen from ammonia

Magnesia–carbon nanotubes (abbreviated as MgO–CNTs) nanocomposites were prepared by impregnation of CNTs with Mg(NO3)2·6H2O in ethanol solution, followed by drying at 353 K and calcination at 873 K, respectively. The nanocomposites are thermally more stable than CNTs in a H2 flow. The use of the nanocomposites as support yielded more efficient Ru catalysts for the generation of COx-free hydrogen from NH3 decomposition.

Effect of the oxidation state of gold on the complete oxidation of isobutane on Au/CeO2 catalysts

Catalysts of highly dispersed gold supported on ceria were prepared by deposition precipitation method. Au is dispersed as Au0, Au+ and Au3+ species on ceria. The content of Au+ and Au3+ was highest on catalyst prepared on uncalcined ceria, which possess least ordered surface. It is inferred that oxygen vacancy on disordered ceria surface is essential for the preparation of highly dispersed gold catalysts and in stabilizing monolayer surface Au+ clusters while cationic vacancies are sites for substitutional Au3+. Au/CeO2 catalysts showed low-temperature isobutane oxidation activity with maximum conversion at 150–180°C. Ex-situ XPS results demonstrated that the low temperature isobutane oxidation activity was closely related to the content of Au+ which we interpreted as surface gold oxide formed under reaction conditions. Isobutane oxidation activity associated with ceria at temperature above 300°C was enhanced by substitutional Au3+.

THE OXIDATIVE COUPLING OF METHANE AND THE ACTIVATION OF MOLECULAR O2 ON CEO2/BAF2

CeO2/BaF2 was used as the catalyst for the oxidative coupling of methane (OCM). At 800°C and CH4∶O2=2.7∶1,CH4 conversion of 34% with C2 hydrocarbon selectivity of 54.3% was obtained. XRD measurement showed that partial anion (O2−,F−) and/or cation (Ce4+,Ba2+) exchange between CeO2 and BaF2 lattices occurred. ESR study showed that O− species existed on degassed catalyst. XPS study revealed that, when BaF2 was added to CeO2, the binding energy of Be 3d5/2 was 2.2 eV lower than that in CeO2, and the “electron-enriched lattice oxygen” species was detected. XPS, ESR and Raman study showed that, under O2 adsorbing conditions, O22− and O−2 species were detected on CeO2/BaF2.

Methane and Light Alkane (C 2 -C 4 ) Conversion Over Metal Fluoride-Metal Oxide Catalyst System in Presence of Oxygen

A novel series of metal fluoride-metal oxide catalysts with good to excellent catalytic performance for oxidative coupling of methane and oxidative dehydrogenation of ethane, propane and iso-butane were developed. XRD analysis suggested that, with the addition of metal fluorides to metal oxides, partial substitution of cations and/or anions happened between fluorides and oxides, leading to the formation of new phases ( e.g. LaOF ) and expansion/contraction of lattices ( e.g. in CeO2-BaF2 ). O2 n- (1 ≤ n ≤ 2) species were detected by the Raman spectroscopy over the catalysts after O2 adsorption. O2- species was observed by in situ FTIR spectroscopies at 650°C over SrF2-La2Q3 catalyst.