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5. VOX/Al2O3Catalyzed Oxidative Dehydrogenation of Propane: Focus on Catalyst Characterization and Deactivation Behavior

Author

Passamonti, Francisco J., D’Ippolito, Silvana A., Vicerich, María A., Sanchez, María A., Bocanegra, Sonia, Guignard, Nadia, Especel, Catherine, Epron, Florence, Pieck, Carlos L., and Benítez, Viviana M.

Abstract

Oxidative dehydrogenation of hydrocarbons (ODH) converts propane and/or ethane into propylene and/or ethylene, which are important compounds in the chemical industry. Unlike steam cracking, ODH offers a high theoretical conversion to olefins and lower energy consumption. The ODH reaction of propane to propylene was studied using VOX/Al2O3catalysts prepared by wet impregnation. The reaction conditions were widely varied, with temperatures ranging from 300 to 550 °C, the C3/O2ratio from 1.6 to 3.3, and the vanadium content from 1 to 11 wt %. It was observed that these parameters are key experimental variables that influence the performance of the catalysts in ODH. Catalysts with intermediate vanadium loading exhibit an optimal amount of acidic sites due to the presence of monomeric and polymeric VOXspecies, resulting in high selectivity toward propylene. Temperature-programmed oxidation analyses showed that coke deposition is proportional to the degree of VOXpolymerization.

Published
2025
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26. Selective hydrogenation of oleic acid to fatty alcohols using Rh‐Sn‐B/TiO2 catalysts: Influence of Sn content.

Author

Fonseca Benítez, Cristhian A., Mazzieri, Vanina A., Sánchez, María A., Vicerich, María A., Benitez, Viviana M., and Pieck, Carlos L.

Subjects
FATTY alcohols, OLEIC acid, FATTY acids, TIN, X-ray photoelectron spectroscopy, HYDROGENATION, CATALYST supports, ALCOHOL oxidation
Abstract

The influence of the catalyst Sn content on the production of fatty alcohol from oleic acid by selective hydrogenation was studied using Rh‐Sn‐B catalysts supported on TiO2. The crystal phase of the support was analyzed by X‐ray diffraction (XRD), the reduction state of the metal phase by temperature‐programmed reduction (TPR), and the electronic state of surface species by X‐ray photoelectron spectroscopy (XPS). The metal activity was evaluated by the dehydrogenation of cyclohexane. It was found that the increase in Sn content leads to a proportional drop in the catalytic activity, which could be related to a metallic interaction between Rh and Sn, as shown by TPR. Oxide and metallic Sn, as well as Rh0 and Rh3+, were found by XPS on the catalyst surface. Metallic Rh was, however, found in higher concentration than oxidized Rh in all cases. The yield to fatty alcohols increased with Sn content, and its maximum value for oleyl and stearyl alcohol was 96%. Furthermore, a higher yield (88.3%) was obtained out of unsaturated fatty alcohol (oleyl alcohol), which has proved to be more valuable than saturated alcohol. This was attributed to an adequate Rh/Sn ratio, which modulates the hydrogenating activity of Rh and makes the metal function more selective for hydrogenation of the carbonyl group. The influence of the support on the catalyst performance decreases as the Sn content increases. The support has a practically negligible influence on the catalyst activity for 4–5 wt.% of Sn content. [ABSTRACT FROM AUTHOR]

Published
2023
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30. Influence of the Ir content and the support on the thiotolerance of the Ir/SiO2-Al2O3 catalysts used in selective ring opening of decalin

Author

Florence Epron, Ippolito, Silvana D., Adriana Ballarini, Santiago Rosas, Laurence Pirault-Roy, Catherine ESPECEL, Pieck, Carlos L., Instituto de Investigaciones en Catálisis y Petroquímica 'Ing. José Miguel Parera' [Santa Fe] (INCAPE), Consejo Nacional de Investigaciones Científicas y Técnicas [Buenos Aires] (CONICET)-Universidad Nacional del Litoral [Santa Fe] (UNL), Institut de Chimie des Milieux et Matériaux de Poitiers (IC2MP), and Université de Poitiers-Institut national des sciences de l'Univers (INSU - CNRS)-Institut de Chimie du CNRS (INC)-Centre National de la Recherche Scientifique (CNRS)

Subjects
selective ring opening, decalin, [CHIM]Chemical Sciences, [CHIM.CATA]Chemical Sciences/Catalysis, Ir/SiO2-Al2O3, thiotolerance 2
Abstract

International audience; The influence of Ir content on sulphur tolerance for the selective ring opening of decalin was investigated. Ir/SiO2-Al2O3 catalysts (70 and 80 wt% SiO2) were used. In the absence of sulphur, slight differences were observed on the yields according to the metallic content regardless of the support used. Although the results of cyclopentane hydrogenolysis showed that the metallic function acquires importance as the metal content increases, for these metal percentages the acid function limits the rate of decalin opening reaction. Products distribution are strongly modified using decalin with S content compared to pure decalin. The formation of dehydrogenated products is virtually null due to S adsorbed on the metal sites. The support has low influence on the thiotolerance. The results related to the amount of S per Ir surface atom, showed that for a moderate S content (S/Irsurf  0.30) 1.5 Ir/Sy appears to be less poisoned than 1Ir/Sy and 2Ir/Sy.

Published
2021
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37. Optimization of the Metal Phase Composition of Ir–Pd/SiO2–Al2O3 Catalysts to Increase Thiotolerance in Selective Ring Opening of Decalin.

Author

D'Ippolito, Silvana A., Rosas, Santiago M., Ballarini, Adriana D., and Pieck, Carlos L.

Subjects
BIMETALLIC catalysts, DECAHYDRONAPHTHALENE, IRIDIUM catalysts, CATALYSTS, METALS
Abstract

The activity and S-tolerance of monometallic and bimetallic Ir–Pd catalysts with different atomic ratio (Ir/Pd = 0.5, 1 and 2) and the same total metal content (1 wt%) supported on SiO2–Al2O3 were studied in the hydroconversion of decalin. In the absence of sulfur, bimetallic catalysts showed less activity and selectivity to decalin ring opening products compared to the iridium monometallic catalyst. However they exhibited a greater tolerance to thiophene poisoning (S = 10 ppm). The catalysts with Ir/Pd = 1 and 2 (atomic ratio), with similar metal dispersion, had better resistance to sulfur. The optimal ratio found, Ir/Pd = 1, could be related to the formation of bimetallic particles and an adequate acidity. The total acidity of the catalysts decreased with an increasing Ir/Pd atomic ratio. The addition of sulfur did not significantly modify the selectivity to ring opening products but reduced the formation of dehydrogenated (undesirable) and cracking products. The distribution of the cracking products confirmed that in the absence of S the metallic function controls the decalin ring opening mechanism, except with the monometallic Pd catalyst. With the addition of S the acid function predominates because the activity results correlate with the acidity of the catalysts. [ABSTRACT FROM AUTHOR]

Published
2022
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38. Performance and Deactivation of Ir–Pt and Rh–Pt/SiO2–Al2O3Catalysts for Selective Decalin Ring Opening

Author

Rosas, Santiago M., Benitez, Viviana M., Pieck, Carlos L., and D’Ippolito, Silvana A.

Abstract

Bifunctional catalysts of Pt, Rh, and Ir monometallic and bimetallic (Ir–Pt and Rh–Pt, atomic ratio = 1) with total metallic content 1 wt % supported on SiO2–Al2O3were studied for selective ring opening of decalin at 300, 325, and 350 °C. The formation of Ir–Pt and Rh–Pt alloys was determined by temperature-programmed reduction, X-ray photoelectron spectroscopy (XPS), and high-resolution transmission electron microscopy (HRTEM). Small well-dispersed Ir–Pt and Rh–Pt alloy particles were obtained. The acidity and hydrogenolytic activity of the Rh–Pt catalyst were lower than those of the Ir–Pt catalyst. It was found that the decrease in the apparent activation energy of decalin on Pt due to the incorporation of Ir and Rh is more significant for the Rh–Pt catalyst. The selectivity of the formation of decalin ring-opening products at all three reaction temperatures exceeded 60%. At 300 and 325 °C, all catalysts formed low amounts of undesirable products of cracking and dehydrogenates; consequently, the deactivation was low. The bifunctional mechanism predominates in the formation of ring-opening products. At 350 °C, the highest yields of decalin opening products were obtained with the bimetallic catalysts, ∼60%, close to the monometallic iridium. As the reaction temperature increases, the amount of carbon deposited on the acid function of the catalysts increased. In addition, at 350 °C, the lowest carbon deposition was obtained with the bimetallic catalysts. The larger metal particle size of the Rh–Pt catalyst compared to the Ir–Pt catalyst resulted in a lower yield of dehydrogenated products, directly related to the coke formation of the bimetallic catalysts.

Published
2025
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