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The influence of Ir content on sulphur tolerance for the selective ring opening of decalin was investigated. Ir/SiO2‐Al2O3 catalysts (70 wt% 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. [ABSTRACT FROM AUTHOR]

Alumina and silica‐alumina supported Ru‐Pt catalysts were evaluated for the ring opening of naphthenes. Pt, Ru, and Ru‐Pt catalysts were prepared by the impregnation of inorganic precursors over γ‐alumina and silica‐alumina supports. The catalysts were evaluated by temperature programmed reduction (TPR), pyridine temperature programmed desorption (TPD), CO‐FTIR, and by test reactions of 33DM1B isomerization, cyclohexane dehydrogenation, cyclopentane hydrogenolysis, and the ring opening of decalin. The strong interaction between the metals (Pt‐Ru) was attributed to their reductions occurring simultaneously. The acidity and strength of the acid sites of the monometallic Ru catalyst were higher than those of the monometallic Pt catalyst. The total acidity (Lewis and Brønsted) and the strength of the acid sites were higher for the silica‐alumina supported catalysts. The silica‐alumina catalysts had 10 times more Brønsted acidity than the γ‐alumina ones and an increased activity and selectivity to decalin ring opening products. Supported monometallic Ru had the best performance for the ring opening reaction. [ABSTRACT FROM AUTHOR]

Bimetallic Rh–Pd catalysts prepared by various impregnation methods were evaluated in the selective ring-opening of decalin and methylcyclohexane (MCH) used as model molecules of hydrogenated aromatics of the Light Cycle Oil fraction. Rh and Pt were deposited on Al 2 O 3 and SiO 2 –Al 2 O 3 (S40) by coimpregnation (CI) or successive impregnations (SI) with different orders of metal addition. Catalysts were characterized by H 2 chemisorption, temperature-programmed reduction, temperature-programmed desorption of pyridine, and test reactions of cyclopentane hydrogenolysis and isomerization of 3,3-dimethyl-1-butene. Their catalytic behaviors for the ring-opening reaction were deeply influenced by the acidity of the support, and in a lesser extent by the metal deposition method. On both supports, the CI catalysts, displaying the highest dispersion values, exhibited the best ring opening performances. In the case of the SI catalysts, the addition order of both metals modified in a moderate way the properties of the catalyst. The yield to ring opening products obtained in MCH ring opening with CI catalysts supported on Al 2 O 3 was 39–69% higher than those prepared by SI (conversion = 55–60%) while for the catalysts supported on S40, the yield to ring opening products was 8–48% higher for the CI catalysts compared to SI catalysts (conversion = 72–77%). The conversion of decalin for the bimetallic catalysts supported on Al 2 O 3 was lower than 20% being dehydrogenated compounds the main reaction products regardless the preparation method. The catalyst supported on S40 showed decalin conversion values between 46 –53% and yield to ring opening near to 30%. Moreover, the CI catalysts have yield to ring opening 10 to 20% higher than the catalysts prepared by SI. The catalyst prepared by coimpregnation supported on S40 was the most appropriate for opening the MCH and decalin due to an optimal balance between the metal and acid functions. [ABSTRACT FROM AUTHOR]

Rh–Pd catalysts supported on Al 2 O 3 , SiO 2 and SiO 2 –Al 2 O 3 (SIRAL 40) were studied for methylcyclohexane (MCH) and decalin ring opening reactions. It was found that the Rh/Pd atomic ratios were similar to the theoretically expected one and the metal dispersion values varied between 30 and 50%. On bimetallic catalysts supported on Al 2 O 3 and SiO 2 , Pd and Rh were present mainly in the form of monometallic particles, whereas a heterogeneous distribution constituted of large Pd particles and small bimetallic ones were observed on SIRAL 40. Total and Bronsted acidities followed the order: SIRAL 40 >> Al 2 O 3 > SiO 2 . Al 2 O 3 supported catalysts were the most suitable for MCH ring opening, while the opening of decalin was favored by using SiO 2 –Al 2 O 3 (SIRAL 40). The catalysts supported on SiO 2 produced mainly dehydrogenated compounds. The higher total and Bronsted acidities of SIRAL 40 series had a great impact on the opening of bicyclic naphthenes, whereas the metal function of the catalyst and the hydrogenolytic activity of Rh had a major role during MCH reaction. Using bimetallic catalysts in the MCH reaction decreased the formation of cracking and dehydrogenated products, and the selective formation of RO products could be optimized by tuning the working temperature. [ABSTRACT FROM AUTHOR]

Highlights: [•] Methylcyclohexane ring opening using Rh–Pd supported on SiO2/Al2O3 was studied. [•] Total and the Brønsted acidity have a higher influence on the activity for decalin ring opening than for single ring opening. [•] The influence of the metal charge is more important on the reaction of MCH. [•] All the catalysts display a high MCH conversion which increases with the reaction temperature. [•] Catalysts with Rh/Pd=2 and monometallic Rh1 supported on SIRAL 40 has the highest yield to ring opening products. [ABSTRACT FROM AUTHOR]

Highlights: [•] Decalin ring opening using Rh–Pd supported on SiO2/Al2O3 was studied. [•] Support acidity is strongly influenced by the SiO2/Al2O3 ratio. [•] Rh and/or Pd modify the conversion and the product distribution. [•] Support acidity has a strong influence on the conversion and product distribution. [•] Rh/Pd=2 and monometallic Rh supported on SIRAL 40 are the most active and selective. [ABSTRACT FROM AUTHOR]

Ring opening of decalin was studied using Rh-Pd(x) catalysts supported on SiO 2 -Al 2 O 3 , prepared by coimpregnation with a variable total metallic content (x = 1, 1.5 and 2 wt%) while maintaining constant the Rh/Pd atomic ratio (equal to 1). The catalytic performances of these bimetallic systems were compared to those of monometallic Pd and Rh (1 wt%) catalysts. Bimetallic Rh-Pd(x) catalysts were unable to achieve decalin conversion and ring opening selectivity as high as those obtained using the Rh catalyst (~71 and ~67%, respectively, after 6 h reaction time). The principal cause was the reduction of the hydrogenolytic activity and acidity caused by the combination of Pd and Rh. In the case of the bimetallic Rh-Pd(x) samples, an increase in the metal content favored the formation of dehydrogenated products, reduced cracking (by reducing the concentration of strong acid sites) and increased coke deposition during decalin ring opening. Conversely, the Rh catalyst showed less deactivation since its efficient hydrogenolytic character eliminates coke precursors. [ABSTRACT FROM AUTHOR]

Abstract: The influence of Ir content on the properties of Pt-Ir/Al2O3 and Pt-Ir/TiO2 catalysts for selective ring opening of naphthenes was studied. It was found that these catalysts display a strong Pt–Ir interaction but only a weak metal–support interaction. Catalyst acidities depend on the metal loading, but opposite effects were observed on alumina (decrease) or titania (increase) as the metal loading increased. The results obtained from test reactions (cyclohexane dehydrogenation and cyclopentane hydrogenolysis) showed that titania supported catalysts were less active than their alumina supported counterparts. This behavior could be due to the partial blockage of metallic sites by migrated TiO x species and the sinterization of metallic phase during the reduction step. The methylcyclopentane ring opening reaction was found to occur through a partially selective mechanism, and an increase in activity as the Ir loading increased was observed. The selective mechanism was favored by higher total metal loadings, possibly due to an increase in the size of metallic aggregates. Alumina supported catalysts present higher ring opening selectivities. The activity for decalin ring opening increased both with metal loading and reaction temperature level. [Copyright &y& Elsevier]