Estanislao L. Jablonski

Effect of the carbon pre-treatment on the properties and performance for nitrobenzene hydrogenation of Pt/C catalysts

Abstract This paper reports a study of the effect of the purification and functionalization treatments of a peach pit derived carbon on the properties and performance for nitrobenzene hydrogenation reaction of Pt/C catalysts. Results show that the elimination of inorganic impurities, mainly sulphur, enhances the nitrobenzene hydrogenation rate. Moreover, the functionalization treatments of purified carbon with ozone and hydrogen peroxide have a positive effect both on the Pt dispersion and on the hydrogenation capacity of the catalyst, while the HNO3-treatment has a lower effect. The effect of the different oxidants can be related to the nature of the functional groups developed on the carbon surface. Thus, HNO3-treated carbon displays a high density of both strong and weak acid sites, while H2O2- and O3-treated carbons show an important concentration of weak acid sites but a low concentration of strong acid sites, according to the TPD results. Moreover, the H2PtCl6 isotherms in liquid phase at 298 K show a stronger interaction of the metallic precursor with the carbons of low acidity (like those treated with H2O2 or O3) than with the most acidic carbon (treated with HNO3). Carbons functionalized with weak oxidants, which develop acidic sites with moderate strength and show strong interaction with H2PtCl6 during impregnation, would favour the Pt dispersion on the carbon surface and consequently the catalytic behaviour.

Preparation of Pt catalysts supported on activated carbon felts (ACF)

Activated carbon felts (ACFs) have been used as supports for Pt catalysts. The preparation was carried out by the impregnation method using chloroplatinic acid as metal precursor. The effect of impregnation time and surface chemistry of the support on the catalytic properties and the characteristics of the metallic phase have been investigated. Nitrobenzene (Nbz) hydrogenation in liquid phase at 25 °C and cyclohexane (CH) dehydrogenation in gas phase at 300 °C were used as catalytic tests. The state of platinum in reduced catalysts (at 100 and 350 °C) was studied by TPR and XPS. Oxygen surface groups only produce a slight effect on the catalytic properties. The use of low impregnation times (30 min) during the preparation of Pt/ACF leads to catalysts with Pt mainly deposited in the outer shell of the fibers, while at higher impregnation times, the metallic atoms seem to be deposited inside the pores. Pt(0) species appear in catalysts reduced at 100 °C by effect of the reducing properties of the carbon fiber exhibiting a considerable catalytic activity for Nbz hydrogenation.

Hydrogenation of carvone on Pt–Sn/Al2O3 catalysts

Abstract The effect of Sn concentration in Pt–Sn/Al 2 O 3 catalysts prepared by different procedures on the catalytic behavior in the carvone hydrogenation in liquid phase was studied. Results indicated that the increase of the Sn amount added to Pt modified the catalytic behavior, favoring the formation of unsaturated ketones and the simultaneous production of small quantities of unsaturated alcohols as reaction intermediaries. On the other hand, Pt/Al 2 O 3 catalyst only produced carvomenthone as the main reaction intermediary.

Highly selective and stable multimetallic catalysts for propane dehydrogenation

Different mono (Pt), bi (Pt–Sn, Pt–Pb, Pt–Ga) and trimetallic (Pt–Sn–Ga) catalysts based on Pt and supported on different materials (Al2O3, Al2O3–K and ZnAl2O4) were tested under severe process conditions in the propane dehydrogenation reaction (both in continuous and in pulse reactors). Results show that the Pt–Sn–Ga/ZnAl2O4 catalyst has a better and more stable performance in propane dehydrogenation (high yield to propene and low coke deposition), than the other bi- and trimetallic systems and a commercial catalyst. Thus, the use of an adequate support (ZnAl2O4) in combination with the addition of Ga to the Pt–Sn bimetallic system enhances the catalytic performance. © 2000 Society of Chemical Industry

Estudio de Catalizadores de Rutenio para la obtención de Gas de Síntesis a partir del Reformado Seco de Metano

This work studies the catalytic performance in dry reforming of Ru catalysts supported on γ-Al2O3 promoted with Na, K, Mg, Ca and Ba. The supports and the catalysts were characterized and tested in the reaction of CH4 reforming with CO2. Ru/Al2O3-Na and Ru/Al2O3-K catalysts showed higher conversions and better H2/CO molar ratios. This catalytic behavior would be related with the higher metallic dispersions and with the basicity of the support. When the reduction time in H2 was shortened, a decrease of the conversions for all the catalysts, except for Ru/Al2O3-Na, was observed. This phenomenon would not be due to the thermal effect but to the reduction time.