Preparation Of Heterogeneous Catalysts Research Articles

MOCVD-loading of mesoporous siliceous matrices with Cu/ZnO: supported catalysts for methanol synthesis.

Consecutive vaporization cycles for the preparation of heterogeneous catalysts: Active Cu- and ZnO-containing methanol-synthesis catalysts were obtained by vaporizing suitable organometallic precursors into mesoporous silicates, followed by thermal treatment (see scheme). The catalytically active components in the final material have nanoscopic dimensions. The methanol production by the catalysts is similar to that of systems synthesized by the classical route. Supporting information for this article is available on the WWW under http://www.wiley-vch.de/contents/jc_2002/2004/z51166_s.pdf or from the author. Please note: The publisher is not responsible for the content or functionality of any supporting information supplied by the authors. Any queries (other than missing content) should be directed to the corresponding author for the article.

Fundamentals in the preparation of heterogeneous catalysts

The preparation of heterogeneous catalysts has by now lost all empirical aspects. The approach is scientific and involves a wide number of specific competencies of solid state chemistry, analytical chemistry, physical chemistry, kinetics, rheology, etc. The fundamental aspects in the preparation of heterogeneous catalysts starting from catalyst design up to the catalyst in its final form are briefly reviewed, with focus on the key factors in each preparation step and the main differences between laboratory and industrial scale preparations. The main properties of monolithic catalysts and their preparation methods are also reported, considering their relevance for environmental applications.

Unusual Approaches to the Preparation of Heterogeneous Catalysts and Supports Using Water in Subcritical and Supercritical States

AbstractFor Abstract see ChemInform Abstract in Full Text.

Unusual approaches to the preparation of heterogeneous catalysts and supports using water in subcritical and supercritical states

The prospective ways of using water in sub- and supercritical states for the preparation of nanocrystal oxide catalysts Ce0.5Zr0.5O2, Ce0.1Y x Zr0.9 – xO2, Zr1 – xY x O2, Zr1 – xIn x O2, La2CuO4 , supported catalysts Pd/Rh/ZrO2and Pd/Rh/TiO2, and supports CeO2, ZrO2, TiO2are discussed. The proposed technique is characterized by high productivity. It is also ecologically friendly and enables one to obtain multicomponent oxide catalysts with chemical and phase composition and properties that can be changed within large ranges. The physicochemical properties of sub- and supercritical water are discussed. A brief review of the present studies on the use of critical media in various physicochemical processes is given.

Temperature programmed studies of Co on MCM-41 and SiO 2

High surface area MCM-41 with mesoporous structure and conventional SiO 2, containing micropores were used as support materials for Co 2(CO) 8 in a gas phase preparation of supported cobalt samples. Two different kinds of preparation methods were used: direct deposition, with continuous adsorption of cobalt carbonyl on to the support over an extended period of time; and a pulsing method with successive deposition/decarbonylation cycles. Since the reduced metal is usually the active phase in catalytic reactions, the aim of the preparation of heterogeneous catalysts is to produce samples in which the supported metal is easily reducible. The effects of the support materials, the gas phase deposition methods and decarbonylation atmospheres on the reactivity of the Co/SiO 2 and Co/MCM-41 samples toward oxygen and hydrogen treatments were compared. According to the results, reducibility of the samples decreased in the order: MCM-41+ pulsing method > SiO 2+ pulsing method > SiO 2+ direct method > MCM-41+ direct method . Oxygen/hydrogen consumptions of the samples decreased in the decarbonylation atmosphere inert>oxidising>reducing. Co/SiO 2 and Co/MCM-41 samples prepared via pulsing method indicated a good stability during oxidation/reduction treatments.

A fluidized bed reactor for low temperature deposition

Abstract A new reactor system was designed a, and constructed for controlled gas-phase preparation of heterogeneous catalysts. The reactor operates at low temperatures (25–200°C) and under inert atmospheres, allowing the use of volatile, air-sensitive precursors like metal carbonyls. Accurate temperature control in the different parts of the reactor system, and effective particle mixing in the fluidized bed, enable controlled preparation. Test results confirmed the usefulness of the reactor in the preparation of Co/SiO2 samples from CD2(CO)8 precursor.

ChemInform Abstract: The Utilization of Saturated Gas‐Solid Reactions in the Preparation of Heterogeneous Catalysts

AbstractChemInform is a weekly Abstracting Service, delivering concise information at a glance that was extracted from about 100 leading journals. To access a ChemInform Abstract of an article which was published elsewhere, please select a “Full Text” option. The original article is trackable via the “References” option.

ChemInform Abstract: Design and Preparation of Heterogeneous Catalysts by Controlled Chemical Reactions with Oxygen and Hydrogen

AbstractChemInform is a weekly Abstracting Service, delivering concise information at a glance that was extracted from about 100 leading journals. To access a ChemInform Abstract of an article which was published elsewhere, please select a “Full Text” option. The original article is trackable via the “References” option.

Polyhedral silsesquioxanes as precursors of tailor-made heterogeneous catalyst centres: I. Water oxidation

Fe-, Ni-, Cu- and Mn-polyhedral oligometallasilsesquioxanes containing (PhSiO 1.5) 12(MO) n L-fragments (where L= ROH, H 2O; n = 6 for Fe, Ni, Mn and n = 4 for Cu; Ni 4Fe 2- and Ni 4Cu 2- complexes were also used) have been used for the preparation of heterogeneous catalysts to investigate the influence of structural factors on the catalytic properties of the hydroxides of these metals. SAXS have been used for the characterization of the distribution of complexes associated in the solution and on the supports surface. It was found that the complex distribution on the carbon support (soot) is close to monomolecular. The highest O 2 yields have been obtained when Fe 6/C were used as catalysts. It has been found that supports have a strong influence on the catalytic properties of supported complexes. The catalysts prepared based on the Fe 6 complexes were more active than those prepared from Ni 4Fe 2 complexes, in which active Fe atoms are separated by inactive Ni atoms. This observation is very important for the mechanism developed by the authors. According to this mechanism it is necessary for the formation of O 2 to have at least two metal ions associated with each other in active centre.

Design and Preparation of Heterogeneous Catalysts by Controlled Chemical Reactions with Oxygen and Hydrogen

ABSTRACTChemical reactions of metals and strongly interacting alloys such as Cu-Mn, Ni-Ti, Ni-Hf and Ni-Zr with oxygen and hydrogen play important roles in the preparation, activation, and regeneration of many important heterogeneous catalytic systems involving supported and unsupported metals and alloys. Recent advances in the understanding of metal and alloy oxidation is bringing new insight into the reactive design and activation of bi- and multi-metallic catalysts. By surface studies of oxidation, thermal annealing and reduction of selected alloys and their thin films and reaction layers and products we have been able to delineate the factors which are most important to the oxide formation processes and the oxide reduction processes. Reaction models developed from these results are permitting the design of new catalyst systems and providing long sought understanding to explain specific aspects of well established metallic catalysts.

Aspects of the preparation of heterogeneous catalysts by impregnation

Some aspects of impregnating supports to produce heterogeneous catalysts have been considered for silica-supported samples: (i) the ease of determining the point of “incipient wetness” of the support, (ii) the reactivity of the support in aqueous solution and (iii) the separation of Ni2+ and Cu2+ when impregnated onto the silica from aqueous and alcoholic solutions.

Preparation of small ?-iron particles from an amorphous Fe91Zr9 alloy

Small α-iron particles with diameter less than 10 nm and enlarged lattice constant have been obtained by low temperature oxidation and reduction of an amorphous Fe91Zr9 alloy.In-situ X-ray diffraction has been used to study the transformation of the alloy at 300 °C which is far below the crystallization temperature. Scanning electron microscopy showed that the reacted sample consisted mainly of aggregates of small iron particles. This might offer a promising method for the effective preparation of heterogeneous catalysts.

ChemInform Abstract: Some Metallorganic Compounds of Ni, Mo, Cr, and W as Materials in the Preparation of Heterogeneous Catalysts

ChemInformVolume 18, Issue 43 Reviews ChemInform Abstract: Some Metallorganic Compounds of Ni, Mo, Cr, and W as Materials in the Preparation of Heterogeneous Catalysts K. JIRATOVA, K. JIRATOVA Ustav teor. zak. chem. techn. CSAV, Praha, CzechoslovakiaSearch for more papers by this authorJ. ROCEK, J. ROCEK Ustav teor. zak. chem. techn. CSAV, Praha, CzechoslovakiaSearch for more papers by this author K. JIRATOVA, K. JIRATOVA Ustav teor. zak. chem. techn. CSAV, Praha, CzechoslovakiaSearch for more papers by this authorJ. ROCEK, J. ROCEK Ustav teor. zak. chem. techn. CSAV, Praha, CzechoslovakiaSearch for more papers by this author First published: October 27, 1987 https://doi.org/10.1002/chin.198743384Read the full textAboutPDF 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 onFacebookTwitterLinked InRedditWechat No abstract is available for this article. Volume18, Issue43October 27, 1987 RelatedInformation

Heterogeneous Catalyst Preparation

Heterogeneous Catalyst Preparation

Polymetallic catalysts derived from intermetallic hydrides

A new method of preparation of heterogeneous catalysts, derived from the intermetallic hydrides of ZrNiH x , ZrCoH x , HfNiH x , HfCoH x , ZrFeH x , ZrNiCuH x , ZrCoCuH x , TiCuH x and TiMoH x (0.5 ⩽ x ⩽ 3), has been recently developed. The phenomenon of surface segregation of metals due to oxidation serves as the basis of the method. It was established that the effect of the surface segregation due to the oxidation is enhanced by the influence of hydrogen, evolved from the bulk of the hydrides. The catalysts derived from the intermetallic hydrides are shown to be quite active in the reactions of hydro-dehydrogenation, hydrogenolysis, dehydrocyclization and hydrodealkylation of hydrocarbons. These catalysts are more active than those of the individual as well as supported metallic catalysts in comparable conditions. Moreover, these systems exhibit higher stability in all the investigated reactions. A mechanism has been proposed for the formation of the catalytically active surface on the intermetallic hydrides.

G. Poncelet, P. Grange, P. A. Jacobs (Eds.): Preparation of Catalysts III, Scientific Bases for the Preparation of Heterogeneous Catalysts, Vol. 16 aus: Studies in Surface Science and Catalysis, Elsevier Scientific Publishing Company, Amsterdam and New York 1983. 854 Seiten, Preis: Dfl 400,–.

Berichte der Bunsengesellschaft für physikalische ChemieVolume 88, Issue 1 p. 82-82 Buchbesprechung G. Poncelet, P. Grange, P. A. Jacobs (Eds.): Preparation of Catalysts III, Scientific Bases for the Preparation of Heterogeneous Catalysts, Vol. 16 aus: Studies in Surface Science and Catalysis, Elsevier Scientific Publishing Company, Amsterdam and New York 1983. 854 Seiten, Preis: Dfl 400,–. H. G. Lintz, Search for more papers by this author H. G. Lintz, Search for more papers by this author First published: Januar 1984 https://doi.org/10.1002/bbpc.19840880121AboutPDF 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 No abstract is available for this article. Volume88, Issue1Januar 1984Pages 82-82 RelatedInformation

Industrial aspects of cluster chemistry

The reasons for industrial interest in metal clusters and cluster catalysis are described. These may be summarized as attempting to bridge the gap between homogeneous and heterogeneous catalysis, specifically by combining the high selectivities typical of the former with the high activities associated with the latter. Progress towards the realization of this objective is illustrated by using examples of our work in both areas. Thus, some results from an investigation of homogeneous ruthenium and rhodium catalysts (as both separate components and mixtures) for the synthesis of oxygenated products from CO-H2are summarized and correlated with high-pressure infrared spectroscopic measurements. The cluster anion [Rh5(CO)15] - is shown from spectroscopic evidence to be very closely related to the catalytically active species in the rhodium-catalysed reactions. Also, the distinction between the behaviour of supported catalysts derived from Group VIII metal cluster compounds and those obtained by more conventional methods of heterogeneous catalyst preparation is discussed. For example, in the case of ruthenium, cluster-derived catalysts are shown to display greatly enhanced activity for the complete hydrogenolysis of straight-chain aliphatic hydrocarbons to methane and provide a temperature advantage of 150°C relative to conventionally prepared ruthenium catalysts, where only moderate hydrocarbon conversions are noted. The increased activity superficially correlates with the smaller metal crystallite sizes (15-20 A; 1.5-2.0 nm) reproducibly obtainable with metal cluster compounds as catalyst precursors.

Preparation of Heterogeneous Catalysts

Over three hundred participants met in Louvain-la-Neuve, Belgium, at the beginning of September 1978 to attend a Second International Symposium, sponsored by the International Union of Pure and Applied Chemistry and the Division de Catalyse of the Société Chimique de Belgique, to discuss the scientific bases for the preparation of heterogeneous catalysts. Papers described the preparation of active oxides, carbides and metals; a considerable fraction concerned the platinum group metals and a brief review of some of these is now presented.

Clay minerals as heterogeneous catalysts in preparation of model humic substances

Huminstoffbildung unter katalytischer Einwirkung der Tonminerale im ModellversuchIn Gegenwart von Tonmineralien und Quarz verläuft die oxydative Polymerisation von Protocatechusäure zu Huminstoffen. Fulvosäuren treten hauptsächlich in der Lösungsphase auf, während Huminsäuren mit dem Bodensatz niedergeschlagen werden. Die Polymerisation wird von Abbau‐ und Mineralisierungsprozessen der verschiedenen organischen Zwischenprodukte begleitet, die über oxydative Ringsprengungen verlaufen. In ihrer katalytischen Wirkung ließen sich die Minerale in die Reihe Illit > Montmorillonit > Kaolinit > Quarz einordnen. Der Mechanismus der Katalyse wird diskutiert.