Tetragonal structure, anionic vacancies and catalytic activity of SO42−-ZrO2 catalysts for n-butane isomerization

Abstract An assessment of the influence of the crystal structure, surface hydroxylation state and previous oxidation/reduction pretreatments on the activity of sulfate-zirconia catalysts for isomerization of n-butane was performed using crystalline and amorphous zirconia supports. Different sulfation methods were used for the preparation of bulk and supported SO42−-ZrO2 with monoclinic, tetragonal and tetragonal+monoclinic structures. Activity was important only for the samples that contained tetragonal crystals. The catalysts prepared from pure monoclinic zirconia showed negligible activity. SO42−-ZrO2 catalysts prepared by sulfation of crystalline zirconia displayed sites with lower acidity and cracking activity than those sulfated in the amorphous state. Prereduction of the zirconia samples with H2 was found to greatly increase the catalytic activity, and a maximum rate was found at a reduction temperature of 550–600 °C, coinciding with a TPR peak supposedly associated with the removal of lattice oxygen and the creation of lattice defects. A weaker dependence of catalytic activity on the density or type of surface OH groups on zirconia (before sulfation) was found in this work. A model of active site generation was constructed in order to stress the dependence on the crystal structure and crystal defects. Current and previous results suggest that tetragonal structure in active SO42−-ZrO2 is a consequence of the stabilization of anionic vacancies in zirconia. Anionic vacancies are in turn supposed to be related to the catalytic activity for n-butane isomerization through the stabilization of electrons from ionized intermediates.Fil: Vera, Carlos Roman. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Santa Fe. Instituto de Investigaciones en Catálisis y Petroquímica ; ArgentinaFil: Pieck, Carlos Luis. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Santa Fe. Instituto de Investigaciones en Catálisis y Petroquímica ; ArgentinaFil: Shimizu, Kiyoyuki. National Institute for Resources and Environment (NIRE) (AIST, MITI); JapónFil: Parera, Jose. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Santa Fe. Instituto de Investigaciones en Catálisis y Petroquímica ; Argentin

Total metallic dispersion of sulfided Pt-Re/Al2O3 naphtha reforming catalysts

Catalysts with Pt, Re and Pt-Re supported on γ alumina were prepared by impregnation or catalytic reduction methods. The activation was performed by calcination–reduction or only direct reduction treatment. These catalysts and a commercial one were sulfided with H2S at 500°C and characterized by chemical analysis, TPR, test reactions (cyclohexane dehydrogenation and cyclopentane hydrogenolysis), chemisorption of H2 and O2 and TEM. The test reactions were affected by S according to the interaction Pt-Re and metallic dispersion of the catalysts, which are functions of the preparation technique. The presence of S inhibits H2 chemisorption, which cannot be used as a measure of the metallic dispersion. Nevertheless, sulfidation or Pt-Re alloying does not affect the O2 chemisorption and this chemisorption can be used to calculate the total (Pt+Re) metallic dispersion with a stoichiometry ratio Pt or Re/O equal to 1.Fil: Pieck, Carlos Luis. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Santa Fe. Instituto de Investigaciones en Catálisis y Petroquímica ; ArgentinaFil: Gonzalez, Monica Beatriz. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Santa Fe. Instituto de Investigaciones en Catálisis y Petroquímica ; ArgentinaFil: Parera, Jose. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Santa Fe. Instituto de Investigaciones en Catálisis y Petroquímica ; Argentin

Effect of water vapor on the activity of Pt-Pd/Al2O3 catalysts for methane combustion

A study on the deactivation phenomena affecting the catalysts of small-scale natural gas catalytic combustors was undertaken in this work. The influence of simulated aging pretreatments on the activity of Pt-Pd catalysts supported over gamma alumina for the catalytic combustion of CH4 was assessed under atmospheric conditions and in the 50–950 °C temperature range. Accelerated deactivation tests consisted of steaming at temperatures between 500–800 °C. The results showed that the activity of the deactivated catalysts depended on two opposite phenomena. An enhancement of the activity was encountered for low aging temperatures and was addressed to chlorine (Cl) elimination (as detected by chemical analysis). Conversely, at higher temperatures the accelerated aging treatment produced a decrease in the activity, and this was allegedly linked to a decrease in the available metal surface area produced by sintering. During the catalyst lifespan and under real operation conditions, a first period is therefore expected where the catalytic activity improves due to the Cl elimination by the water (H2O) produced during combustion. Afterwards, the activity would decrease because of the sintering of the metal phase. Both processes, Cl elimination and sintering, occur simultaneously. Five different catalyst formulations with variable Pt and Pd contents were tried and 0.4%Pt-0.8%Pd was found to be the most active. The results found are discussed in terms of the activity of the monometallic catalysts, the degree of interaction of the Pt and Pd phases and the previously mentioned phenomena of sintering and Cl elimination.Fil: Pieck, Carlos Luis. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Santa Fe. Instituto de Investigaciones en Catálisis y Petroquímica ; ArgentinaFil: Vera, Carlos Roman. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Santa Fe. Instituto de Investigaciones en Catálisis y Petroquímica ; ArgentinaFil: Peirotti, Eduardo M.. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Santa Fe. Instituto de Investigaciones en Catálisis y Petroquímica ; ArgentinaFil: Yori, Juan Carlos. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Santa Fe. Instituto de Investigaciones en Catálisis y Petroquímica ; Argentin

Pt/SO42−-ZrO2 catalysts prepared from Pt organometallic compounds

New Pt/SO42−-ZrO2 catalysts were prepared using precalcined SO42−-ZrO2 and organometallic Pt precursors. The objective was to obtain a bifunctional catalyst with improved metal properties, which are mostly suppressed in Pt/SO42−-ZrO2 prepared in a standard fashion. The synthesis route used low temperatures to form the Pt particles in order to avoid sulfate decomposition and Pt poisoning. The use of precalcined zirconia decreased ionic diffusion, related to crystallization of the gel and encapsulation of Pt particles. As detected by TPR and cyclohexane dehydrogenation tests, after reducing at 270 °C, Pt on the new catalyst had metallic properties. Its dehydrogenation activity was higher than that of a standard Pt/SO42−-ZrO2 catalyst (prepared from H2PtCl6). After activating in air at 300 °C, its activity for n-butane isomerization (300 °C, 1 atm., H2:n-C4=6, WHSV=1 h−1) was low, very likely because of incomplete elimination of adsorbed water. After activation in air at 600 °C, the isomerization activity was almost similar to that of standard Pt/SO42−-ZrO2 but the dehydrogenation activity decreased to negligible values. The deleterious interaction between Pt and SO42−-ZrO2 that occurred during calcination was possibly related to oxidation of the metal. On the other side, high reduction temperatures did not enhance the metal activity beyond the level obtained after reducing at 270 °C. On the contrary, the higher the reduction temperature, the lower the activity for cyclohexane dehydrogenation that was obtained. This effect was seemingly related to poisoning by sulfur compounds. The new materials could be potentially useful for reacting systems needing a bifunctional catalyst and an acid function like SO42−-ZrO2 but their operation is limited if high temperatures in air or H2 are necessary for activation.Fil: Vera, Carlos Roman. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Santa Fe. Instituto de Investigaciones en Catálisis y Petroquímica ; ArgentinaFil: Pieck, Carlos Luis. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Santa Fe. Instituto de Investigaciones en Catálisis y Petroquímica ; ArgentinaFil: Shimizu, Kiyoyuki. National Institute for Advanced Industrial Science and Technology (AIST); JapónFil: Yori, Juan Carlos. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Santa Fe. Instituto de Investigaciones en Catálisis y Petroquímica ; ArgentinaFil: Parera, Jose. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Santa Fe. Instituto de Investigaciones en Catálisis y Petroquímica ; Argentin

Oxidation of o-xylene to phthalic anhydride on Sb-V/ZrO2 catalysts

Zirconia-supported and bulk-mixed vanadium-antimonium catalysts were used for the oxidation of o-xylene to phthalic anhydride. Vanadium promoted the transition of tetragonal to monoclinic zirconia. The simultaneous presence of antimony and vanadium on zirconia at low coverage led to a preferential interaction of individual V and Sb oxides with the zirconia surface rather than the formation of a binary Sb-V oxide, while at higher Sb-V contents, the formation of SbVO4 took place. Sb-V-ZrO2 catalysts showed high activity for o-xylene conversion and better selectivity to phthalic anhydride as compared to V/ZrO2 catalysts. However, their selectivity to phthalic anhydride was poor compared to V/TiO2 commercial catalysts. The improved selectivity of the Sb-containing catalysts was attributed to the blocking of non-effective surface sites of ZrO2, the decrease of the total amount of acid sites and the formation of surface V-O-Sb-O-V structures.Fil: Pieck, Carlos Luis. Consejo Nacional de Investigaciones Científicas y Técnicas; Argentina. Instituto de Catálisis y Petroleoquímica; EspañaFil: del Val, S.. Instituto de Catálisis y Petroleoquímica; EspañaFil: López Granados, M.. Instituto de Catálisis y Petroleoquímica; EspañaFil: Bañares, M.A.. Instituto de Catálisis y Petroleoquímica; EspañaFil: Fierro, J.L.G.. Instituto de Catálisis y Petroleoquímica; Españ

Deactivation study of Ru-Sn-B/Al2O3 catalysts during selective hydrogenation of methyl oleate to fatty alcohol

In this work, the deactivation of the Ru-Sn-B/Al2O3 catalyst prepared by the incipient wetness method in the selective hydrogenation reaction of methyl oleate to fatty alcohol was studied. There was a decrease in both the activity and selectivity of fatty alcohol during successive reaction experiments. The fresh and deactivated catalysts were evaluated by different techniques such as TPR, XPS, TGA, Raman, and FTIR to determine the deactivation causes. Lower Ru and Sn content were found in the deactivated catalyst due to the loss of the active material during hydrogenation reaction. As the metal loss was more important for Ru than for Sn, the Ru/Sn ratio was changed, leading to a decrease of the selectivity. Moreover, the analysis of the XPS peak by the deconvolution of Sn species suggests the more active (SnOx) species for selective hydrogenation are more affected than the less selective (SnOy). Coke deposition was not observed by Raman and FTIR.Fil: Sánchez, María A.. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Santa Fe. Instituto de Investigaciones en Catálisis y Petroquímica "Ing. José Miguel Parera". Universidad Nacional del Litoral. Instituto de Investigaciones en Catálisis y Petroquímica "Ing. José Miguel Parera"; ArgentinaFil: Vicerich, Maria Ana. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Santa Fe. Instituto de Investigaciones en Catálisis y Petroquímica "Ing. José Miguel Parera". Universidad Nacional del Litoral. Instituto de Investigaciones en Catálisis y Petroquímica "Ing. José Miguel Parera"; ArgentinaFil: Mazzieri, Vanina Alejandra. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Santa Fe. Instituto de Investigaciones en Catálisis y Petroquímica "Ing. José Miguel Parera". Universidad Nacional del Litoral. Instituto de Investigaciones en Catálisis y Petroquímica "Ing. José Miguel Parera"; ArgentinaFil: Gioria, Esteban Gaston. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Santa Fe. Instituto de Investigaciones en Catálisis y Petroquímica "Ing. José Miguel Parera". Universidad Nacional del Litoral. Instituto de Investigaciones en Catálisis y Petroquímica "Ing. José Miguel Parera"; ArgentinaFil: Gutierrez, Laura Beatriz. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Santa Fe. Instituto de Investigaciones en Catálisis y Petroquímica "Ing. José Miguel Parera". Universidad Nacional del Litoral. Instituto de Investigaciones en Catálisis y Petroquímica "Ing. José Miguel Parera"; ArgentinaFil: Pieck, Carlos Luis. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Santa Fe. Instituto de Investigaciones en Catálisis y Petroquímica "Ing. José Miguel Parera". Universidad Nacional del Litoral. Instituto de Investigaciones en Catálisis y Petroquímica "Ing. José Miguel Parera"; Argentin

Preparation, characterization and regeneration of Pt-Re/Al2O3 naphtha reforming catalysis

Fil: Pieck, Carlos Luis. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Santa Fe. Instituto de Investigaciones en Catálisis y Petroquímica ; Argentin

Influence of indium content on the properties of Pt-Re/Al2O 3 naphtha reforming catalysts

The influence of indium on the properties of Pt-Re/Al2O 3 catalysts used in naphtha reforming is studied. The addition of indium to the Pt-Re/Al2O3 catalyst produces a big decrease of acidity. It also produces an inhibition of the metal function, i.e., dehydrogenation and hydrogenolysis activity. The reaction of n-C5 isomerization shows that indium addition decreases the total activity of the Pt-Re catalyst but increases the selectivity to the i-C5 isomers. The selectivity to low cost light gases (C1-C3) is particularly decreased. The reaction of n-C7 reforming showed that addition of indium increases the stability of the catalyst and the selectivity to aromatics, and decreases the production of light gases.Fil: Benitez, Viviana Monica. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Santa Fe. Instituto de Investigaciones en Catálisis y Petroquímica "Ing. José Miguel Parera". Universidad Nacional del Litoral. Instituto de Investigaciones en Catálisis y Petroquímica "Ing. José Miguel Parera"; ArgentinaFil: Pieck, Carlos Luis. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Santa Fe. Instituto de Investigaciones en Catálisis y Petroquímica "Ing. José Miguel Parera". Universidad Nacional del Litoral. Instituto de Investigaciones en Catálisis y Petroquímica "Ing. José Miguel Parera"; Argentin

Alkane isomerization on MoO3/ZrO2 catalysts

Molybdenum was used as an alternative to sulfate as promoter of zirconia for alkane isomerization reactions. It has similar effects to sulfate, tungstate and phosphate ions, modifying the physicochemical properties of unpromoted zirconia. Mo‐promoted zirconia catalysts do not show any activity for n‐C4 isomerization. For n‐C7 isomerization, the catalytic activity depends on Mo content, crystalline structure of the support and the molybdenum oxospecies present on the surface of the catalysts.Fil: Yori, Juan Carlos. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Santa Fe. Instituto de Investigaciones en Catálisis y Petroquímica "Ing. José Miguel Parera". Universidad Nacional del Litoral. Instituto de Investigaciones en Catálisis y Petroquímica "Ing. José Miguel Parera"; ArgentinaFil: Pieck, Carlos Luis. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Santa Fe. Instituto de Investigaciones en Catálisis y Petroquímica "Ing. José Miguel Parera". Universidad Nacional del Litoral. Instituto de Investigaciones en Catálisis y Petroquímica "Ing. José Miguel Parera"; ArgentinaFil: Parera, Jose. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Santa Fe. Instituto de Investigaciones en Catálisis y Petroquímica "Ing. José Miguel Parera". Universidad Nacional del Litoral. Instituto de Investigaciones en Catálisis y Petroquímica "Ing. José Miguel Parera"; Argentin

Acid or bifunctional mechanism in paraffin isomerization reaction on Pt/SO42−−ZrO2 and Pt/WO3−ZrO2 catalysts

At low temperature (300°C) the isomerization of n-C4H10 on Pt/SZ occurs only by a monofunctional acid mechanism. It is necessary to increase the temperature to produce the amount of olefins requiered for the bifunctional mechanism because of thermodynamic limitations and the decrease of metallic function acvtivity of Pt due to support interactions. Pt is less affected on Pt/WZ, presenting high hydrogenolysis activity. The isomerization of n-C7H16 can proceed at low temperatures by a bifunctional mechanism because due to the easy dehydrogenation to n-C7H14 a very small fraction of metallic function is enough.Fil: Yori, Juan Carlos. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Santa Fe. Instituto de Investigaciones en Catálisis y Petroquímica ; ArgentinaFil: Pieck, Carlos Luis. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Santa Fe. Instituto de Investigaciones en Catálisis y Petroquímica ; ArgentinaFil: Parera, Jose. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Santa Fe. Instituto de Investigaciones en Catálisis y Petroquímica ; Argentin