Vanina A. Mazzieri

Influence of the operating conditions and kinetic analysis of the selective hydrogenation of methyl oleate on Ru–Sn–B/Al2O3 catalysts

The influence of the operating conditions and preparation methods of Ru–Sn–B/Al2O3 catalysts on the activity and selectivity for the hydrogenation of methyl oleate to oleyl alcohol was studied. It was found that catalysts prepared by incipient wetness (IW) are more active and selective than those prepared by co-impregnation. This better performance is possibly due to a lower level of residual chlorine. The experiences of hydrogenation of methyl oleate showed that activity increases as the reaction temperature increases while the selectivity to oleyl alcohol has a maximum value. This could be due to the higher activation energies for the hydrogenolysis of carboxymethyl groups than those found for C=C double bonds hydrogenation. The increase in operating pressure has a positive effect on the activity but it influences selectivity time patterns in a more complex way. Experiments carried out by varying methyl oleate/n-dodecane ratio show that the selectivity and conversion not depend on this parameter. A simple kinetic model is proposed.

Preparation and characterization oF Ru-Sn/Al2O3 catalysts for the hydrogenation of fatty acid methyl esters

Ru-Sn/Al2O3 catalysts with different Sn loadings were prepared by the coimpregnation method. Several characterization techniques such as TPR, pyridine TPD and catalytic tests for dehydrogenation and hydrogenolysis were used to evaluate and compare such catalysts. TPR results indicate that Sn is deposited both onto the support and as species strongly interacting with Ru. Such non selective deposition modifies the acid and metallic functions of the catalysts. Both total acidity and acid strength distribution are affected: total acidity decreases and new sites of lower acid strength are created. Both dehydrogenating and hydrogenolytic activities are strongly diminished by the addition of Sn. Results of catalytic tests for methyl oleate hydrogenation indicate that methyl stearate is the main product, with only minute amounts of oleyl alcohol produced, and that the addition of Sn diminishes the hydrogenation activity.

Influence of methanol addition during selective hydrogenation of benzene to cyclohexene

The addition of a certain methanol concentration during benzene hydrogenation on Ru/Al2O3 improves the selectivity to cyclohexene because of a preferential adsorption of methanol on the most active Ru sites.

Sulfur Resistance of Pt-W Catalysts

The sulfur resistance of low-loaded monometallic Pt catalysts and bimetallic Pt-W catalysts during the partial selective hydrogenation of styrene, a model compound of Pygas streams, was studied. The effect of metal impregnation sequence on the activity and selectivity was also evaluated. Catalysts were characterized by ICP, TPR, XRD, and XPS techniques. Catalytic tests with sulfur-free and sulfur-doped feeds were performed. All catalysts showed high selectivities (>98%) to ethylbenzene. Activity differences between the catalysts were mainly attributed to electronic effects due to the presence of different electron-rich species of Pt0 and electron-deficient species of . Pt0 promotes the cleavage of H2 while the adsorption of styrene. The catalyst successively impregnated with W and Pt (WPt/Al) was more active and sulfur resistant than the catalyst prepared with an inverse impregnation order (PtW/Al). The higher poison resistance of WPt/Al was attributed to both steric and electronic effects.

Ru-Sn-B/Al2O3 Catalysts for Selective Hydrogenation of Methyl Oleate: Influence of the Ru/Sn Ratio

This study focuses on the influence of the Ru/Sn ratio on the catalytic hydrogenation of methyl oleate to oleyl alcohol using Ru-Sn-B catalysts, notably on the catalytic activity and selectivity. Sn addition acts positively over the oleyl selectivity by reducing the rates of C=O and C=C saturation but also decreases the global activity. The catalyst with the highest activity and selectivity towards oleyl alcohol is Ru(1%)-Sn(2%)-B/Al2O3. At a low Sn loading (0.5%) the catalyst has high activity for hydrogenation of the carbonyl group and the carbon-carbon double bond. As a consequence stearyl alcohol is produced with high yield. At a high Sn content (4%) the catalyst has lower selectivity to oleyl alcohol due to its low capacity for hydrogenating the carbonyl group. However it has enough activity for hydrogenating the C=C double bonds to produce the saturated methyl ester.