Roger Kieffer

Change of catalytic properties of FeZnO/zeolite composite catalyst in the hydrogenation of carbon dioxide

Abstract The hydrogenation of carbon dioxide was examined using the composite catalysts which were obtained by the physical mixing of Fe ZnO and HY zeolite. Fe ZnO was a typical F-T (Fischer-Tropsch) catalyst and Fe ZnO/HY is a composite catalyst which is able to induce a combined methanol synthesis and MTG (Methanol-to-Gasoline) reaction. To study these unique catalytic behaviors of Fe ZnO/HY, the adsorption and the dissociation of carbon monoxide on Fe ZnO as well as TPR measurements were carried out. Fe ZnO is able to produce hydrocarbons by F-T reaction and methanol. In the absence of zeolite, Fe ZnO exerts its ability for F-T reaction. However, HY diminishes the activity for F-T reaction and hydrocarbons were obtained via methanol formed over the modified Fe ZnO

Oxidative dehydrogenation of propane on rare earth vanadates influence of the presence of CO2 in the feed

Abstract The oxidative dehydrogenation of propane on rare earth vanadates is always in competition with the total oxidation of the alkane which leads to the formation of CO 2 and CO. Addition of CO 2 into the feed results in an increased C 3 H 6 selectivity together with a decreased CO formation through the total oxidation of the alkane or the formed alkene. For the tested rare earth vanadates as well as for the niobium promoted catalysts an enhancement of the C 3 H 6 selectivity at isoconversion and thus of the C 3 H 6 yields is observed upon CO 2 addition into the feed.

Synergetic effect between NiO and Ni3V2O8 in propane oxidative dehydrogenation

The oxidative dehydrogenation (ODH) of propane was investigated on Ni-V-O catalysts in a wide range of vanadium contents (5-40%). The addition of a small amount of vanadium significantly increased the catalytic activity of NiO for oxidative dehydrogenation of propane to propene. The formation of propene has a good correlation with the coexistence of NiO and Ni3V2O8. This result strongly suggests that a synergetic effect exists between them in NiXV1-XOY (X = 0.95 to 0.6). The best results were obtained with a high Ni/V ratio (e.g. X = 0.95 to 0.85). The active sites and selective oxygen species are discussed. The influence of the catalyst preparation technique and the redox properties of the catalyst were also examined.

Oxidative Dehydrogenation of Propane in Presence of Rare Earth Vanadates

Publisher Summary V 2 O 5 -containing materials have been used in the oxidative dehydrogenation of light-molecular-weight alkanes. Only few examples have been reported for the use of non-stoichiometric rare-earth vanadates for the reaction of propane. This chapter reports on the activity of rare-earth vanadates of a definite Zirkon structure, LnVO 4 (Ln = Ce, Pr, Nd, Tb, Er, Tb), in the title reaction of propane. Rare-earth vanadates are an original catalytic system for the activation of propene, which can compete with the more classical Mn vanadate catalyst. For each catalyst, a correlation can be established between propane selectivity and total conversion. A high propane conversion leads to a low olefin selectivity in all cases. The oxygen/propane ratio in the feed influences the conversion and the selectivity. An interesting correlation between C 3 H 8 conversion and C 3 H 6 selectivity can be observed. A Mars Van Krevelen mechanism, taking into account the reaction on oxygen vacancies on the catalytic surface, describes these results well.

Hydrocarbon synthesis from CO2 over composite catalysts

Hydrogenation of CO 2 was carried out using various composite catalysts containing a methanol synthesis catalyst and a zeolite. Hydrocarbons were obtained via methanol by MTG(Methanol to Gasoline) reaction. Cu-Zn-Cr mixed oxide prepared from CuO, ZnO and CrO 3 was an effective component of the composite catalyst for the synthesis of light paraffins. The composite catalyst containing Cu-Zn chromate or Fe-ZnO gave higher hydrocarbons via olefin intermediate formed from methanol. Fe-ZnO had two active sites; iron species formed from Fe 3 O 4 and ZnFe 2 O 4 . When Fe-ZnO was used alone, F-T reaction over iron species was predominant. The addition of HY zeolite to Fe-ZnO deactivated the iron species for F-T reaction, and thus MTG reaction over ZnFe 2 O 4 became predominant.

Investigations on the promoting effect of metal oxides on La-V-O catalyst in propane oxidative dehydrogenation

The addition of reducible metal oxides as promoters shows a positive effect on the catalytic behavior of lanthanum vanadate (LaVO4). A C3H6 yield increase of 6.5% is observed at 500 °C on molybdenum-promoted LaVO4, which can be attributed to the change of the redox properties, the blocking of the strong oxidation sites of the catalysts and to an increase of the accessibility of the labile oxygen toward the reactant. The influence of the catalyst preparation method and of the Mo loading as well as the additional promoting effect of CO2 in the gas feed was also examined.