This study intends to illustrate the application of transient kinetics in combinatorial research. Thus, it is shown through various case studies how high-throughput transient kinetics may both accelerate the search for new catalytic materials and bring fundamental insights in reaction mechanisms. As a first case study, the cracking reactions of the C-6 isomers (n-hexane, 2-methylpentane, 3-methylpentane, 2,3-dimethylbutane, and 2,3-dimethylbutane) over a fluidised catalytic cracking (FCC) catalyst at temperatures between 300 and 650 degreesC have been studied in a temporal-analysis-of-product (TAP) reactor. A mathematical model taking into account the extra- and intracrystalline transport phenomena was used to determine the diffusion, sorption, and kinetic parameters for the hydrocarbons studied. Sorption and diffusion decrease with increasing branching in agreement with literature data. Except product distribution, the activation energies for the overall cracking of the C-6 isomers are similar for all isomers. As a second case study, a "paralleled" TAP reactor with a multisample holder is shown to be an efficient tool for acquiring adsorption/desorption parameters for a series of zeolites, tested to evaluate their potential as catalyst supports in the oxidative dehydrogenation of ethane. Finally, the applied combinatorial study was found also suitable for discovering new materials precursors of dense oxygen-conducting membranes. From high-throughput transient TAP and TPD experiments, it was possible to derive a strategy directing the rapid combinatorial evolution within the available parameter space. It was shown that high-quality information is accessible from these data, providing all parameters necessary for a well fitting description with a kinetic model. (C) 2003 Elsevier Science (USA). All rights reserved.

The catalytic reduction of NO by CH4 over Co/ZSM-5 zeolite is studied by means of transient in situ DRIFT, SSITK and TAP analyses. Co ions located at the interface of Co clusters and zeolite are found to react with NO in the presence of oxygen to form anchored NOδ+2 species stabilized under reaction conditions. These species form the main active sites for activating methane molecule. Two ways of CO2 formation from the same intermediate including fragments of both NOx and partially dehydrogenated CH4 molecule are proposed in the mechanistic scheme of the reaction.

The oxidative dehydrogenation of propane over a V/MgO catalyst was studied in a TAP-2 reactor. The experiments were carried out using oxygen rich and lean feeds at temperatures between 500 and 650 degrees C. The data can be described adequately by a rate equation based on a reaction sequence involving elementary steps. The rate-determining step is the irreversible adsorption of propane leading to an alkyl intermediate that reacts rapidly to adsorbed propene. Sorption of propene is reversible and further oxidation of adsorbed propene leads to COx. No information on the oxygen activation could be obtained. All kinetic parameters were found to be physically meaningful and sensitive to the oxidation state of the catalyst.

Isotopic transient experiments combined with in situ DRIFT spectroscopy and TAP experiments were used to study the methane dehydrogenation and aromatisation over a Mo/HZSM-5 catalyst. The stoichiometric reduction of both external and internal molybdenum oxide into carbide-like species was clearly observed in the early stage of the reaction. The active sites for the catalytic dimerization of methane into ethylene are in very low concentration and could be internal carbide-like clusters in tight interaction with the zeolite. The methane molecules are also strongly interacting with most of the OH groups in the zeolite via a reversible activation process leading to the OH/OD exchange. However this activation process is not directly related to the aromatisation process. A large reservoir of benzene precursors is also present in the zeolite, also strongly interacting with the OH groups. Benzene appears as a secondary product formed from ethylene. The aromatisation steps could occur directly on the acid sites of the zeolite, available after the initial reduction and clustering of the Mo ions.

The interaction of ammonia with the surface of a model ruthenium sulfide catalyst has been investigated using conventional adsorption measurements, temperature programmed desorption and inelastic neutron scattering. This work has provided evidence that the amount and also the nature of adsorbed species vary with the sulfur to metal ratio of the solid. On the unreduced sample, ammonia interacts weakly with the solid and ammonium ions are not observed. On the partially desulfurized catalyst, the chemisorption of ammonia is dissociative. The NH2 fragment is bonded to a coordinatively unsaturated ruthenium ion formed upon reduction of the solid while the proton is trapped by a sulfur anion leading to the formation of SH groups. It was previously shown that hydrogen adsorption also involves unsaturated sites. Adsorption of ND3, on a hydrogen-covered surface provokes a desorption of HD indicating that a competition of adsorption occurs between hydrogen and ammonia. This result explains why ammonia generally acts as a poison for hydrogenation, hydrodenitrogenation, and hydrodesulfurization reactions.

This work reports a systematic study of the changes in the catalytic activities and in adsorptive of ruthenium sulphide with sulphur removal. From physicochemical characterization of the reduced samples it is shown that 50% of the initial sulphur content can be eliminated without changing the structure and the morphology of the pyrite phase. The adsorption of CO, NO and H2S increases with the degree of reduction of the solid. However, the maximum of adsorption capacities for these probe molecules does not correspond to the maximum of catalytic activity observed for the reactions of H-2-D2 exchange and 1-butene hydrogenation. This suggests that distinct sites are required for adsorption and for catalysis. The use of ammonia as probe molecule seems to be a good tool for determining the Bronsted acidic surface sites. From thermoflash desorption of hydrogen, it has been demonstrated that two different species are retained by the catalyst : one adsorbed on surface sulphur atoms and the other one adsorbed on coordinatively unsaturated ruthenium cation. The concentration of the latter correlates fairly well with the catalytic activities.

A vast majority of refineries uses alumina supported Co/Ni–Mo/W catalysts in their hydrotreating units. As several Ni compounds are classified as carcinogens category 1A or 1B and some soluble Co compounds are classified as carcinogens category 1B and toxic to reproduction category 1B, catalyst manufacturers are required to look for suitable substitutes with a less severe hazard profile under the existing workplace legislation.There is extensive literature on alternatives to using Co and Ni in hydrotreating catalysts. Several compositions were reported to have high activities in various hydrotreating reactions. However, in reality, the options are limited as many alternative compositions are either very expensive, are not available in sufficient amounts for commercial use, or are known to be toxic. Most noble metal compositions proposed in the literature are several orders of magnitude more expensive than normal hydrotreating catalysts. Other compositions that are acceptable from the cost point of view do not show sufficient activity. This is illustrated by a series of ultra-low sulfur diesel (ULSD) and VGO FCC-pretreat tests. These tests use alumina supported single transition metals as well as combinations of first row transition metals with Mo or W. All catalysts tested have much lower activities than the commercial catalysts.The consequences of using such low active catalysts in existing refinery units are also discussed. To achieve the same product quality and cycle length a catalyst with half the activity of a reference catalyst requires a 50% reduction in space velocity, which is infeasible for virtually every refinery. The refiner can either significantly increase reactor temperature or invest in additional reactors. Either way, the additional refining costs will increase the fuel price paid by the consumer at the pump and have a major negative impact on the competitiveness of many European refineries.

Bulletin des Sociétés Chimiques BelgesVolume 100, Issue 11-12 p. 907-913 Article Selectivity of Y-Zeolite and Alumina Supported Ruthenium Sulphide in Hydrodesulfurization of Thiophene S. Göbölös, Institut de Recherches sur la Catalyse, CNRS, 2, Avenue Albert Einstein, 69626 Villeurbanne Cédex, France On leave from the Central Research Institute for Chemistry of the Hungarian Academy of Sciences, 1025 Budapest, II. Pusztaszeri ut 59-67, HungarySearch for more papers by this authorM. Lacroix, Institut de Recherches sur la Catalyse, CNRS, 2, Avenue Albert Einstein, 69626 Villeurbanne Cédex, FranceSearch for more papers by this authorT. Decamp, Institut de Recherches sur la Catalyse, CNRS, 2, Avenue Albert Einstein, 69626 Villeurbanne Cédex, FranceSearch for more papers by this authorM. Vrinat, Institut de Recherches sur la Catalyse, CNRS, 2, Avenue Albert Einstein, 69626 Villeurbanne Cédex, FranceSearch for more papers by this authorM. Breysse, Institut de Recherches sur la Catalyse, CNRS, 2, Avenue Albert Einstein, 69626 Villeurbanne Cédex, FranceSearch for more papers by this author S. Göbölös, Institut de Recherches sur la Catalyse, CNRS, 2, Avenue Albert Einstein, 69626 Villeurbanne Cédex, France On leave from the Central Research Institute for Chemistry of the Hungarian Academy of Sciences, 1025 Budapest, II. Pusztaszeri ut 59-67, HungarySearch for more papers by this authorM. Lacroix, Institut de Recherches sur la Catalyse, CNRS, 2, Avenue Albert Einstein, 69626 Villeurbanne Cédex, FranceSearch for more papers by this authorT. Decamp, Institut de Recherches sur la Catalyse, CNRS, 2, Avenue Albert Einstein, 69626 Villeurbanne Cédex, FranceSearch for more papers by this authorM. Vrinat, Institut de Recherches sur la Catalyse, CNRS, 2, Avenue Albert Einstein, 69626 Villeurbanne Cédex, FranceSearch for more papers by this authorM. Breysse, Institut de Recherches sur la Catalyse, CNRS, 2, Avenue Albert Einstein, 69626 Villeurbanne Cédex, FranceSearch for more papers by this author First published: 1991 https://doi.org/10.1002/bscb.19911001116Citations: 8 AboutPDF ToolsRequest permissionExport citationAdd to favoritesTrack citation ShareShare Give accessShare full text accessShare full-text accessPlease review our Terms and Conditions of Use and check box below to share full-text version of article.I have read and accept the Wiley Online Library Terms and Conditions of UseShareable LinkUse the link below to share a full-text version of this article with your friends and colleagues. Learn more.Copy URL Share a linkShare onEmailFacebookTwitterLinked InRedditWechat Citing Literature Volume100, Issue11-121991Pages 907-913 RelatedInformation

Catalysts containing ca.2% (w/w) of ruthenium were prepared by using [Ru(NH3)6]Cl3 as a precursor compound and HY, NaY and KY zeolites as supports. Ru/KY catalyst modified by Na2S via impregnation was also investigated. Prior to the catalytic tests, the catalysts were sulphided with a H2-H2S mixture. The hydrodesulphurization (HDS) of thiophene at atmospheric pressure, the conversion of biphenyl, the hydrogenation (HN) of pyridine and the hydrodenitrogenation (HDN) of piperidine under medium-high pressure were carried out under dynamic conditions. The fast deactivation and, thus, the low activity of Ru/HY and Ru/NaY catalysts in the HDS of thiophene are attributed to coke formation on the Brönsted acid sites of the support. The stability and the activity of the catalysts in this reaction can be improved by decreasing the strength of the Brönsted acid sites. In the conversion of biphenyl, the activity towards the formation of cracking products increases with the acidity of the supports. The activity of the catalysts in the HN of pyridine and in the HDN of piperidine is less affected by the acid strength of the support. Only a slight decrease on the activities is observed for the most acidic support.

Alumina supported Ni-W catalysts with contents of components varying over a wide range were systematically studied in order to optimize a catalyst for further industrial use, mainly for HDN reactions.

The authors discuss their investigation of the effect of support acidity in different hydrotreating reactions. Catalysts containing ruthenium were prepared by using (Ru(NH/sub 3/)/sub 6/)Cl/sub 3/ as a precursor compound and HY, NaY and KY zeolites as supports. Ru/KY catalyst modified by Na/sub 2/S via impregnation was also investigated. Prior to activity tests, the catalysts were sulfided by H/sub 22/-H/sub 2/S mixture. The HDS of thiophene, at atmospheric pressure, and the conversion of biphenyl, the HN of pyridine and the HDN of piperidine, under medium high pressure, were carried out in dynamic conditions.

Alumina supported NiW catalysts with components concentrations varying in a wide range were systematically studied in order to optimize a catalyst for further industrial uses. The genesis of the active phase was examined by using several physicochemical techniques and the catalytic properties were determined in different reactions characteristic of the hydrotreating process i. e. dibenzothiophene and thiophene HDS, biphenyl and pyridine hydrogenation as well as piperidine HDN. The promoting effect of Ni is always observed but the synergy is greatly dependent on the nature of the molecule to be treated. In addition to these activity determinations, the differences in behaviour towards sulfiding conditions and relationships with probe molecules adsorptions suggest that hydrogenation and hydrogenolysis reactions take place on different catalytic sites. The nature of these sites is discussed in terms of the mixed phase model. The selected most active catalyst for performing HDN reactions was studied for real feedstock conversion. Its activity is compared to the properties of conventional nickel molybdenum and nickel tungsten catalysts.