Dominique Vanhove

Catalytic oxidation of 1-butene and butadiene: Study of MoO3TiO2 catalysts

Abstract MoTiO catalysts have been investigated in order to obtain active and selective catalysts for the oxidation of butenes to maleic anhydride. Three methods of catalyst preparation have been used, namely, impregnation, coprecipitation, and decomposition of tartrates. The results suggest that, with all catalysts, active and selective sites are formed at the interface of the two oxides by action of TiO 2 on molybdenum oxide. Catalysts obtained by the decomposition of tartrates are amorphous, more active and selective than the others. The highest activities and selectivities are obtained with MoTiO catalysts containing about 15 mole% MoO 3 (selectivity 53% at 60% conversion). It has been shown that bases such as water or halide ions can change the activity of impregnated catalysts by increasing the surface acidity. The relation between acidity and activity in olefin oxidation is thus confirmed.

Catalytic oxidation of o-xylene

Abstract Oxidation of o -xylene to phthalic anhydride over V 2 O 5 -TiO 2 catalyst has been studied in order to detect the intermediates of this conversion. The oxidation of alcohols such as o -methylbenzyl alcohol and o -xylene-α,α′-diol yields the same compounds as those obtained from the hydrocarbon in the same conditions, whereas oxidation of o -toluic acid yields mainly the lactone, phthalide. Moreover, a competitive oxidation of inactive o -methylbenzyl alcohol, and o -xylene (methyl- 14 C) results in the formation of o -tolualdehyde, phthalide, and phthalic anhydride, having different specific radioactivities, and demonstrates that different reaction paths are involved. A mechanism is proposed in which the selective incorporation of oxygen occurs after abstraction of one hydrogen atom so as to produce a surface alcoholate ion, whereas degradation into maleic anhydrides and carbon oxides arises from substitution of hydrogen atoms of the aromatic nucleus by oxygen.

Hydrocarbon selectivity in fischer-tropsch synthesis in relation to textural properties of supported cobalt catalysts

Abstract Cobalt catalysts for the synthesis of paraffins from carbon monoxide and hydrogen have been prepared by low temperature thermal treatment of dicobalt octacarbonyl impregnated porous supports (alumina, silica-alumina). An catalysts exhibited high selectivities for restrained hydrocarbon cuts, provided there was a low metal loading. The chain length of hydrocarbons was clearly related to the mean pore diameter of the supports and the hydrocarbon cut was restrained by the design of the supports. Adsorption-desorption kinetics have shown that pore condensation and filling can occur at a chain length related to the pore size and thus modify the residence times of hydrocarbons on the catalyst. It is proposed that this physical effect of the support is the limiting factor of the chain length because of the subsequent hydrogenolysis of the condensed hydrocarbons inside the pores when light paraffins are not retained and can easily desorb. With high amounts of metal and conventional catalysts, the metal is mainly at the external surface of the support and this effect can not be seen.

Selective production of alkenes and alcohols on cobalt catalysts in the liquid phase

Syngas (CO-H2, 1:1) conversion on a Ziegler-type cobalt slurry in the liquid phase produces under pressure with good activity a narrow range of light hydrocarbons, essentially alkenes, as well as oxygenated compounds, mainly alcohols in the C1–C4 range.

Cobalt catalysts for the liquid phase synthesis of light olefins from CO and H2

Methane and a C2–C6 cut containing up to 75% olefins are synthesized from CO and H2 at 199 °C and under atmospheric pressure with a catalyst prepared by the reduction of cobalt(II) acetylacetonate with triethylaluminium with an alkylterphenyl solvent.

Selective catalytic synthesis of linear paraffins from CO and H2 over cobalt supported catalysts

Cobalt catalysts, prepared from cobalt carbonyl and alumina, produce from CO and H2 linear paraffins whose molecular weights depend on the porosity of the support.

Fischer-Tropsch Synthesis in a Gas-Liquid-Solid Medium: Selectivities Induced by Phase Equilibria

The Fischer-Tropsch synthesis of hydrocarbons, when using common iron or cobalt industrial catalysts, usually exhibits poor selectivity, especially regarding the carbon chain length.