Cédric Gennequin

Titanium oxide nanotubes as supports of Au or Pd nano-sized catalysts for total oxidation of VOCs

Abstract Titanium oxide nanotubes (TNTs) have been synthesized via laboratory-made TiO2 A and commercial TiO2 P25. 1.5wt% gold or palladium were deposited on TNTA and TNTP25 supports and the catalytic activity was evaluated in propene, methyl ethyl ketone (MEK) and toluene total oxidation. The catalytic properties of supported TNT were correlated with the structural peculiarity and the nature of the TNT, but also with the nature of the noble metal and the kind of the VOC.

Hydrogen Production by Methane Steam Reforming Over Ru and Cu Supported on Hydrotalcite Precursors

Co6Al2 oxide was prepared using the hydrotalcite route. The obtained solid was thermally stabilized at 500°C and then impregnated with 5 wt.% copper or 1 wt.% ruthenium nitrate solution followed by calcination at 500°C under an air flow. X-ray diffraction results showed that the calcination of the impregnated solids led to the formation of various oxides (CuO, RuO2, Co3O4, CoAl2O4, CoAl2O4). The different impregnated and non impregnated solids were tested in the methane steam reforming reaction (MSR). Methane conversion did not exceed 5% at 800°C in the case of the non impregnated solid, whereas the impregnation strongly enhanced the reactivity: ~89% and ~92% conversions were reached at 600°C for Cu and Ru respectively. The good reactivity of ruthenium impregnated catalyst was attributed to the formation of easily reducible ruthenium and cobalt oxide species at the surface of the support. The addition of ruthenium made the reduction of surface and bulk cobalt oxides possible at lower temperatures.

Detection of adsorbed O2− species on CeO2 solid impregnated with Ag2+ ions during its thermal treatment under a H2 atmosphere, an EPR study

10% Ag/CeO2 solid was prepared by the impregnation method. When the solid is calcined at 400 °C, three types of Ag2+ species are formed. One of them is more thermally stable compared to the others. The adsorption on the solid of O2 or H2 molecules gives an adsorbed O2- species on the surface, detected by electron paramagnetic resonance (EPR). The mobility of oxygen in CeO2 and the nature of cations loaded on this support can be the origin of the adsorbed O2- species particularly when the solid is treated under H2 molecules.

Promoting Effect of CeO2 Addition on Activity and Catalytic Stability in Steam Reforming of Methane over Ni/Al2O3

Hydrogen production by steam reforming of methane was studied over Ni catalysts supported on CeO2, Al2O3 and CeO2-Al2O3. These catalysts were prepared using the impregnation method and characterized by XRD. The effect of CeO2 promoter on the catalytic performance of Ni/Al2O3 catalyst for methane steam reforming reaction was investigated. In fact, CeO2 had a positive effect on the catalytic activity in this reaction. Experimental results demonstrated that Ni/CeO2-Al2O3 catalyst showed excellent catalytic activity and high reaction performance. In addition, the effects of reaction temperature and metal content on the conversion of CH4 and H2/CO ratio were also investigated. Results indicated that CH4 conversion increased significantly with the increase of the reaction temperature and metal content.

H2 production by dry reforming of biogas over Ni-Co-Mg-Al mixed oxides prepared via hydrotalcite route

Ni, Co, Mg and Al mixed-oxide catalysts derived from hydrotalcite were synthesized by coprecipitation for the dry reforming of biogas. The catalysts were characterized using X-ray diffraction, Differential Scanning Calorimetry and Thermogravimetric analysis. The specific surfaces were determined by the BET method. After calcination under an air flow, hydrotalcite-like precursors were completely decomposed. The dry reforming of biogas was carried out using a mixture of CH4:CO2 (1:1) after 2 hours of reduction under an H2 flow at 800 °C. Ni-Co containing catalyst revealed better catalytic activity than the monometallic Co catalyst.

Preparation and characterization of Ni-Co-Mg-Al mixed oxides derived from layered double hydroxides and their performance in the dry reforming of methane

The hydrotalcite route was used to prepare Ni and Co oxides catalysts, with different Ni/Co contents. The catalytic performance of these oxides was investigated with the dry reforming of methane in order to produce energy vector from renewable energy. The samples were characterized, before and after calcination, by X-ray diffraction (XRD), differential scanning calorimetry (DSC), thermogravimetric analysis (TG), Fourier Transform Infrared spectroscopy (IR), and determination of the specific surfaces by the BET method. After calcination at 800 °C under an air flow, the hydrotalcite structure was completely decomposed. The dry reforming of methane was carried out using a mixture of CH4:CO2 (1:1) after 2 hours of reduction under an H2 flow at 800 °C. Ni-Co based catalysts revealed better catalytic activity than the Co based one.

The Performance of the Cu-Zn/CeO2 Catalysts in the Steam Reforming of Methanol Reaction

The performances of different xCu10Ce and xZn10Ce (x = 1, 3, and 5) catalysts prepared by impregnation method then pelletised, were investigated in the steam reforming of methanol (SRM) under a GHSV = 15500 h-1 with H2O/CH3OH = 2. The impregnation of copper over ceria supports shows better results than that of zinc. The catalytic activity in the Cu-based depends on the dispersion of the copper species. The methanol conversion rate is related to the formation of an optimum content of reduced copper species.

Dry reforming of methane over NixMg6−xAl1.8La0.2 catalysts

Two Ni_xMg_6-xAl_1.8La_0.2 (x=0,2) catalysts were synthesized via hydrotalcite route and calcined at 800°C. For comparison, a second Ni_xMg_6-xAl_1.8La_0.2(x=2) was also prepared via hydrotalcite route but with hydrothermal treatment to evaluate the difference between conventional preparation and preparation with hydrothermal treatment. Physico-chemical characterizations were conducted before and after calcination. These characterization techniques included X-ray Diffraction (XRD), Fourier Transform Infrared Spectroscopy (FTIR) and Temperature Programmed Reduction (TPR). The catalytic performance of these catalysts was also tested in the Dry Reforming of Methane (DRM). Catalytic test results of the more efficient catalyst were compared to the results of a similar NixMg_6-xAl₂ catalyst such as to evaluate the role of lanthanum doping and its impact on the catalytic activity of the catalysts. It was found that the addition of lanthanum resulted in improved catalytic activity in the DRM reaction. This improvement can be attributed to the formation of more basic sites and the presence of La₂O₃ after calcination which reduces coke formation.

Steam reforming of toluene for hydrogen production over NiMgALCe catalysts prepared via hydrotalcite route

Ni_xMg_6-xAl_1.8Ce_0.2 (with 0 ≤ x ≤ 6) mixed oxides catalysts were prepared by hydrotalcite route. All the oxides were calcined at 800°C and characterized by different physicochemical methods and their catalytic performances were tested toward steam reforming of Toluene. In the steam reforming process, reducing pretreatment is a necessary step to activate the catalyst. Ni₂Mg₄Al_1.8Ce_0.2 shows the better toluene conversion and the best performance (H₂ production) among all the catalysts.

Catalytic performance of nickel-based solid materials in the steam reforming of methane

Ni_xMg_6-xAl₂ (with 0 ≤ x ≤ 6) mixed oxides catalysts were synthesized via hydrotalcite route followed by calcination under air at 800 °C. Their catalytic performances were studied towards steam reforming of methane. A performant catalyst should show simultaneously good activity, stability of crystallite size of metal particles during the test and resistance to carbon deposit.