Platinum Inhibits Low‐Temperature Dry Lean Methane Combustion through Palladium Reduction in Pd−Pt/Al2O3: An In Situ X‐ray Absorption Study

NSERCPeer ReviewedPalladium–platinum bimetallic catalysts supported on alumina with palladium/platinum molar ratios ranging from 0.25 to 4 are studied in dry lean methane combustion in the temperature range of 200 to 500 °C. Platinum addition decreases the catalyst activity, which cannot be explained by the decrease in dispersion or the structure sensitivity of the reaction. In situ X‐ray absorption near‐edge structure and extended X‐ray absorption fine structure spectroscopy measurements have been conducted for monometallic Pd, Pt, and 2:1 Pd−Pt catalysts. Monometallic palladium is fully oxidized in the full temperature range, whereas platinum addition promotes palladium reduction, even in a reactive oxidizing environment. The Pd/PdO weight ratio in bimetallic Pd−Pt 2:1 catalysts decreases from 98/2 to 10/90 in the 200–500 °C temperature range under the reaction conditions. Thus, platinum promotes the formation of the reduced palladium phase with a significantly lower activity than that of oxidized palladium. The study sheds light on the effect of platinum on the state of the active palladium surface under low‐temperature dry lean methane combustion conditions, which is important for methane‐emission control devices

Johann Christoph Müller: Harmonist Pioneer, Composer, and Apostate

Johann Christoph Müller, a physician who served George Rapp’s Harmony Society as “doctor, music director, schoolteacher, printer, archivist, [and] museum curator,” was both a member of Rapp’s elite inner circle and a dissenting voice within the Society. Documentary evidence reveals flares of conflict between Müller and Rapp predating their immigration and culminating in Müller’s departure in the Schism of 1832, yet Müller was also a trusted Harmonist leader and one of an advance party of five men who came to the United States to prepare the way for the mass immigration of Rapp’s Separatists. Although some scholars have defined Müller as a man of science whose rationalism was at odds with Rapp’s mysticism, investigation of Müller’s hymn texts—and his involvement with the Society’s mystic-scientific alchemical experiments—paint a more complex portrait

Pt–Pd bimetallic catalysts for methane emissions abatement

International audienceBimetallic Pd–Pt catalysts with constant 2 wt% metal loading and varying Pt/Pd ratios were prepared, characterized and studied in the catalytic combustion of methane at low temperature under lean conditions in view of their use for CH4 abatement from lean-burn NGV heavy duty vehicles exhausts. The influence of mild steam ageing featuring long-term use of the catalysts was also addressed together with their tolerance to H2S. Catalysts were characterised by Transmission Electron Microscopy and Temperature Programmed Oxidation experiments. Experimental data agreed to suggest an interaction between Pd and Pt in Pdrich catalysts, thus explaining their improved catalytic activity, even after mild ageing, compared to reference Pd/Al2O3. This interaction has no effect on the sulfur tolerance

Correlation between structure and performanceof vacuum gas oil hydrocracking catalysts in a batch reactor

International @ RAFFINAGE+RHE:MTF:PAF:CLOInternational audienceIn order to satisfy the future demand in light and intermediate oil products, refining industry is facing new challenges because of the rarefaction of light and easily exploitable petroleum resources. It needs to upgrade heavier oils through high selectivity conversion processes, such as hydrocracking, while respecting ever more stringent regulations. Thus, the behavior of hydrocracking catalysts needs to be better understood and in order to improve their performance. Relationships between the composition, the structure of the catalysts and their performance are to be investigated. A new approach for studying and modeling complex reaction kinetics with a batch reactor test has been developed. A batch reactor apparatus was therefore developed. Triphasic reactions then took place in a laboratory-scale reactor equipped with a Robinson-Mahoney stationary basket, a hydrogen injection system and liquid/vapor sampling system. Feedstock was a hydrotreated vacuum gas oil, and reaction conditions were 400°C and 120 bars. Different bifunctional catalysts sulfide nickel-molybdenum on a zeolite-containing alumina support were characterized and tested over 3 hour and 6 hour-reactions. Gas and liquid samples were then analyzed by one and two-dimensional gas chromatography, in order to obtain precise composition of each phase during the reaction. The repeatability of conversion and middle distillate selectivity under the test conditions described above was under 1.5 and 1.6%, respectively. The lack of mass transfer limitations at vapor-liquid interface and at liquid-solid interface was confirmed by modifying the stirring speed and the size of the catalyst pellets. This method therefore allows accessing to intrinsic kinetic properties of the catalysts. Afterwards, an experimental design was set up, with the purpose to test catalysts containing different amounts of molybdenum and zeolite. The effects of the bifunctional structure of the catalyst on its reactivity and its selectivity have been observed and discussed

Methodology for the study of vacuum gas oil hydrocracking catalysts Coupling of GC-2D data with vapour-liquid equilibrium

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Vacuum gas oil hydrocracking performance of bifunctional Mo/ Y Zeolite catalysts in a semi-batch reactor

International @ RAFFINAGE+RHE:MTF:PAF:CLOInternational audienceA new approach has been developed to characterize bifunctional catalysts in a complex matrix of hydrotreated vacuum gas oil, 370°C+ using a batch reactor test. Triphasic reactions were carried out in a reactor equipped with a stationary basket, hydrogen injection and products sampling systems. Bifunctional catalysts containing different relative amounts of alumina-supported NiMo sulfide and zeolite were tested at 400°C under 120 bars over different reaction times. The repeatability of the test conditions was validated and the lack of mass transfer limitations at phase interfaces was confirmed. Gas and liquid samples were analyzed by one and two-dimensional gas chromatography (2D-GCGCxGC) respectively to obtain quantitative distributions of linear and branched paraffins, olefins, naphthenes and aromatics. The details of the products distribution provided by the chromatography were analyzed using model kinetic mechanisms of bifunctional catalysis. It has been established that the limiting step defining the total conversion is scission of the hydrocarbon chains on zeolite sites. The increase of the molybdenum to zeolite ratio provided an improvement of selectivity to middle distillate (150-370°C

Vapor-Liquid Equilibrium of Hydrogen, Vacuum Gas Oil, and Middle Distillate Fractions

RAFFINAGE+BBR:RHE:PAF:#30:MTFVapor-liquid equilibrium (VLE) data for hydrogen/hydrocarbon mixtures based on real feedstocks at high temperature and pressure is scarce and is needed to model hydrocracking systems accurately. Experiments with a vacuum gas oil have been used to generate VLE data for real hydrogen/hydrocarbon mixtures under hydrocracking conditions in a semibatch reactor with a range of compositions. Flash calculations were performed using a process simulation program and compared to the experimental results. The data was used to verify the existence of equilibrium conditions in the reactor and to show that the Grayson Streed activity coefficient model, combined with Peng-Robinson equation of state, provides a good estimate of liquid phase and vapor phase compositions and individual component volatility

Vacuum gas oil hydrocracking performance of bifunctional Mo/Y zeolite catalysts in a semi-batch reactor

RAFFINAGE+RHE:MTF:PAF:CLO:#30A new approach has been developed to characterize bifunctional catalysts in a complex matrix of hydrotreated vacuum gas oil using a batch reactor test. Triphasic reactions were carried out in a reactor equipped with a stationary basket, hydrogen injection and products sampling systems. Bifunctional catalysts containing different relative amounts of alumina-supported NiMo sulfide and zeolite were tested at 400 degrees C under 120 bars over different reaction times. The repeatability of the test conditions was validated and the lack of mass transfer limitations at phase interfaces was confirmed. Gas and liquid samples were analyzed by one and two-dimensional gas chromatography (GC x GC) respectively to obtain quantitative distributions of linear and branched paraffins, naphthenes and aromatics. The details of the products distribution provided by chromatography were explained using mechanisms of bifunctional catalysis. It has been established that the limiting step defining the total conversion is the scission of the hydrocarbon chains on acid sites of the zeolite. The increase of the molybdenum to zeolite ratio provided an improvement of middle distillate selectivity. (C) 2013 Elsevier B.V. All rights reserved

Methodology and Modeling For Correlating Structure and Performance of Vacuum Gas Oil Hydrocracking Catalysts in a Batch Reactor

International @ RAFFINAGE+RHE:MTF:PAF:CLOInternational audienceA new approach has been developed to characterize bifunctional catalysts in a complex matrix of hydrotreated vacuum gas oil, 370°C+ using a batch reactor test. Triphasic reactions were carried out in a reactor equipped with a stationary basket, hydrogen injection and products sampling systems. Bifunctional mesoporous catalysts containing different relative amounts of alumina-supported NiMo sulfide and zeolite were tested at 400°C under 120 bars over different reaction times. The repeatability of the test conditions was validated and the lack of mass transfer limitations at phase interfaces was confirmed. Gas and liquid samples were analyzed by one and two-dimensional gas chromatography (2D-GC) respectively to obtain quantitative distributions of linear and branched paraffins, olefins, naphthenes and aromatics. The details of the products distribution provided by the chromatography were analyzed using model kinetic mechanisms of bifunctional catalysis. It has been established that the ratio of the molybdenum to zeolite in the bifunctional catalyst affects its activity and selectivity. The increase of the molybdenum to zeolite ratio provided an improvement of selectivity to middle distillate (150-370°C) and an increase of the total conversion of 370°C+ per gram of zeolite