Showing papers on "Catalysis published in 1984"
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TL;DR: In this article, the catalytic activity of catalase has been investigated using ultraviolet (UV) spectrophotometry and Titrimetric methods, which is suitable for comparative studies for large series of measurements.
Abstract: Publisher Summary Catalase exerts a dual function: (1) decomposition of H 2 O 2 to give H 2 O and O 2 (catalytic activity) and (2) oxidation of H donors, for example, methanol, ethanol, formic acid, phenols, with the consumption of 1 mol of peroxide (peroxide activity) The kinetics of catalase does not obey the normal pattern Measurements of enzyme activity at substrate saturation or determination of the K s is therefore impossible In contrast to reactions proceeding at substrate saturation, the enzymic decomposition of H 2 O 2 is a first-order reaction, the rate of which is always proportional to the peroxide concentration present Consequently, to avoid a rapid decrease in the initial rate of the reaction, the assay must be carried out with relatively low concentrations of H 2 O 2 (about 001 M) This chapter discusses the catalytic activity of catalase The method of choice for biological material, however, is ultraviolet (UV) spectrophotometry Titrimetric methods are suitable for comparative studies For large series of measurements, there are either simple screening tests, which give a quick indication of the approximative catalase activity, or automated methods
20,238 citations
Patent•
05 Jun 1984TL;DR: In this article, derivatives of mono, bi and tricyclopentadienyl coordination complexes with a transition metal and an alumoxane are employed in a process of producing polyolefins of controlled molecular weight.
Abstract: Catalysts comprising (a) derivatives of mono, bi and tricyclopentadienyl coordination complexes with a transition metal and (b) and an alumoxane are employed in a process of producing polyolefins of controlled molecular weight.
812 citations
TL;DR: The shape-selective catalysis as discussed by the authors was proposed to increase the selectivity of a desired product and reduce the coke formation in zeolite catalysts by reducing the number of catalytic sites inside the pore structure.
556 citations
Patent•
05 Jun 1984TL;DR: Polyolefin reactor blends obtained by polymerization of ethylene and higher alpha-olefins in the presence of a catalyst system comprising two or more metallocenes and alumoxane as mentioned in this paper.
Abstract: Polyolefin reactor blends obtained by polymerization of ethylene and higher alpha-olefins in the presence of a catalyst system comprising two or more metallocenes and alumoxane.
512 citations
TL;DR: In this paper, it has been observed that carbon-free steam reforming of methane can be obtained on a partly sulfur-passivated nickel catalyst under conditions which, without the presence of sulfur, would result in formation of whisker carbon.
494 citations
TL;DR: In this article, high temperature hydrogen adsorption and conventional 298 K adsorptions of hydrogen and carbon monoxide were characterized by unsupported cobalt and cobalt supported on silica, alumina, titania, magnesia, and carbon.
490 citations
TL;DR: In this article, specific activity and selectivity of unsupported cobalt and cobalt supported on alumina, silica, titania, carbon, and magnesia carriers for CO hydrogenation were measured in a single-pass differential reactor at low conversions, 1 atm, and 175-350 °C.
446 citations
368 citations
TL;DR: In this paper, the authors studied the reaction kinetics of CO, C 3 H 6, 1-hexene, and toluene under excess O 2 and found that the olefin oxidation is strongly self-inhibited by HC and more than first-order in O 2, whereas the opposite was found for Rh.
346 citations
TL;DR: In this article, the hydrogenation of ethylene with both hydrogen and deuterium was studied over (111) platinum single-crystal surfaces under a total pressure of 110 torr and a temperature range of 300-370 K.
Abstract: The hydrogenation of ethylene with both hydrogen and deuterium was studied over (111) platinum single-crystal surfaces under a total pressure of 110 torr and a temperature range of 300-370 K. An activation energy (E/sub a/) of 10.8 +/- 0.1 kcal/mol and kinetic orders with respect to hydrogen and ethylene partial pressure of 1.31 +/- 0.05 and -0.60 +/- 0.05, respectively, were observed. The deuterium atom distribution in the product from the reaction with D/sub 2/ peaks at 1-2 deuterium atoms per ethane molecule produced, similar to what has been reported for supported catalysts. The reaction takes place on a partially ordered carbon covered surface, where the carbonaceous deposits have a morphology similar to that of ethylidyne. However, this ethylidyne does not directly participate in the hydrogenation of ethylene, since both its hydrogenation and its deuterium exchange are much slower than the ethane production. A mechanism is proposed to explain the experimental results.
321 citations
TL;DR: Pecoraro et al. as discussed by the authors used the SCF-Xα calculations of the electronic structure of cluster models of the first and second row transition metal sulfides to identify several electronic factors which appear to be related to the catalytic activity of the sulfides.
TL;DR: In this article, an experimental and theoretical study of the behavior of metal, hydrogen-exchanged Y and USY zeolite cracking catalysts has been conducted using a new theoretical framework for acidity and showed that these data could be correlated against a single parameter, the unit cell constant of the steam deactivated catalyst.
Patent•
08 Mar 1984TL;DR: A process for the preparation of polyketones by polymerizing a mixture of CO and an alkenically unsaturated hydrocarbon in the presence of a Group VIII metal catalyst containing ligands is described in this article.
Abstract: A process for the preparation of polyketones by polymerizing a mixture of CO and an alkenically unsaturated hydrocarbon in the presence of a Group VIII metal catalyst containing ligands, which comprise hydrocarbon groups that are bonded to an element from groub Vb, characterized in that, as catalyst, a complex compound is used that is obtained by reacting a palladium, cobalt or nickel compound, an anion of an acid with a pKa of less than 2, provided it is neither a hydrohalogenic acid nor carboxylic acid and a bidentate ligand of the general formula R 1 R 2 -M-R-M-R 3 R 4 , in which M represents phosphorus, arsenic or antimony, R represents a divalent organic bridging group having at least two carbon atoms in which the bridge, none of these carbon atoms carrying substituents that may cause steric hindrance and in which R 1 , R 2 , R 3 and R 4 are identical or different hydrocarbon groups.
TL;DR: Light olefins will play a dominant role in any future methanol-based chemicals economy as discussed by the authors, and they are initial products in the conversion of methanoline to hydrocarbons over zeolite catalysts.
Abstract: Light olefins will play a dominant role in any future methanol-based chemicals economy. Olefins are initial products in the conversion of methanol to hydrocarbons over zeolite catalysts [1]. The overall reaction path may be represented by
TL;DR: In this article, the conversion of methanol to olefins over ZSM-5 zeolites is described and the interdependence of reaction parameters T, P, contact time, and catalyst Bronsted acidity in controlling olefin selectivity is characterized and interpreted.
TL;DR: L'oxydation catalysee par Pd de dienes-1,3 dans l'acide acetique en utilisant MnO 2 comme oxydant et des quantites catalytiques de benzoquinone-1.4-alcenes-2.
Abstract: L'oxydation catalysee par Pd de dienes-1,3 dans l'acide acetique en utilisant MnO 2 comme oxydant et des quantites catalytiques de benzoquinone-1,4 donne selectivement des diacetoxy-1,4-alcenes-2
TL;DR: In this paper, the authors present a method for oxydation par l'hydroperoxyde de t-butyle, de (methyl p-tolyl), (t-butyl phenyl)-, (benzyl methyl) sulfures et de chloro-4' phenylthio-2 ethanol en presence of propanolate-2 de Ti(IV) and de tartrate de diethyle.
Abstract: Oxydation par l'hydroperoxyde de t-butyle, de (methyl p-tolyl), (t-butyl phenyl)-, (benzyl methyl) sulfures et de chloro-4' phenylthio-2 ethanol en presence de propanolate-2 de Ti(IV) et de tartrate de diethyle
TL;DR: In this article, a detailed model of the chlorine-catalyzed polymerization of methane at 1260 and 1310 K was presented, where the reaction can be separated into two stages, the chlorination of methane and pyrolysis of methylchloride.
Abstract: The reaction of CH4 + Cl2 produces predominantly CH3Cl + HCl, which above 1200 K goes to olefins, aromatics, and HCl. Results obtained in laboratory experiments and detailed modeling of the chlorine-catalyzed polymerization of methane at 1260 and 1310 K are presented. The reaction can be separated into two stages, the chlorination of methane and pyrolysis of methylchloride. The pyrolysis of CH3Cl formed C2H4 and C2H2 in increasing yields as the degree of conversion decreased and the excess of methane increased. Changes of temperature, pressure, or additions of HCl had little effect. In the absence of CH4 C2H4 and C2H2 are formed by the recombination of ĊH3 and ĊH2Cl radicals. With added CH4 recombination of ĊH3 forms C2H6, which dehydrogenates to C2H4 + H2. C2H4 in turn dehydrogenates to C2H2 + H2. While HCl, C, CH4, and H2 are the ultimate stable products, C2H4, C2H2, and C6H6 are produced as intermediates and appear to approach stationary concentrations in the system. Their secondary reactions can be described by radical reactions, which can lead to soot formation. ĊH3 - initiated polymerization of ethylene is negligible relative to the Ċ2H3 formation through H abstraction by Cl. The fastest reaction of Ċ2H3 is its decomposition to C2H2. About 20% of the consumption of C2H2 can be accounted for by the addition of Ċ2H3 to it with formation of the butadienyl radical. The addition of the latter to C2H2 is slow relative to its decomposition to vinylacetylene. Successive H abstraction by Cl from C4H4 leading to diacetylene has rates compatible with the experimental values. About 10% of Ċ4H5 abstracts H from HCl and forms butadiene. Successive additions of Ċ2H3 to butadiene and the products of addition can account for the formation of benzene, styrene, naphthalene, and higher polyaromatics. The following rate parameters have been derived on the basis of the experimentally measured reaction rates, the estimated frequency factors, and the currently available heat of formation of the Ċ2H3 radical (69 kcal/mol):
TL;DR: In this paper, the preparation of dibenzofuran, carbazole, fluorenone, phenanthridone, 6H-dibenzo c,e][l,2]thiazine-5,5-dioxide, benzofurano[2,3b]pyridine derivatives is described, and the cyclisation of 3-benzamido-2-chloropyridine to 6-hydroxybenzoc][1,5]naphthyridne illustrates the regiospecificity of the
TL;DR: In this article, the authors identify a heterogeneous catalyst to selectively produce methyl fatty esters from low erucic rapeseed oil, which is a promising fuel for direct injection diesel engines.
Abstract: Methyl fatty esters derived from vegetable oils are a promising fuel for direct injection diesel engines. This study’s purpose was to identify a heterogeneous catalyst to selectively produce methyl fatty esters from low erucic rapeseed oil. Most experiments were at atmospheric pressure and approximately the corresponding boiling point temperature of the mixture, 60–63 C. However, the catalytic activity of an anion exchange resin was tested at 200 C and 68 atm (1000 psig) and at 91 C and 9.2 atm (135 psig). All samples were analyzed by thin layer chromatography with samples from the elevated temperature and pressure experiments also analyzed by mass spectroscopy. The most promising catalyst examined was CaO·MgO. The activities of the catalysts CaO and ZnO appear to be enhanced with the addition of MgO, therefore the transesterification reaction mechanism may be, in this instance, bifunctional. The anion exchange resin catalyst at 200 C and 68 atm generated substantial amounts of both methyl fatty esters and straight-chain hydrocarbons, even though these reactions did not go to completion. At 91 C and 9.2 atm the cracking also occurred but at a substantially reduced rate, and no transesterification was noted.
TL;DR: In this article, the photocatalytic oxidations of several aliphatic and aromatic compounds with water were investigated with powdered Pt/TiO/sub 2/ catalyst suspended in solution.
Abstract: Photocatalytic H/sub 2/ production from several aliphatic and aromatic compounds with water was investigated with powdered Pt/TiO/sub 2/ catalyst suspended in solution. Various fossil fuels such as coal, tar sand, and pitch also reacted with water, producing both H/sub 2/ and CO/sub 2/ from an early stage of irradiation. The photocatalytic oxidations of their model compounds, especially a linear hydrocarbon and benzene, were studied in the presence of silver ion as an electron acceptor. For aliphatic hydrocarbons, they are oxidized to alcohols, aldehydes, and carboxylic acids, successively. CO/sub 2/ was found to be formed through the photo-Kolbe type of reaction of carboxylic acids produced, which explained well the result of the complete decomposition of n-hexadecane. For benzene, we could detect phenol, catechol, hydroquinone, and muconic acid. On the basis of these results, the possibility of the direct oxidation of benzene by photogenerated holes and its ring-opening process peculiar to the photocatalytic reaction are discussed. The main reaction path for CO/sub 2/ production was suggested in which the benzene ring opens not by way of phenol and catechol, but by way of the intermediates whose reactivities are much larger than that of benzene. 41 references, 5 figures, 4 tables.
TL;DR: In this paper, a closed system between 200 and 300 °C was used for redispersion of carbon monoxide layer over the platinum crystallites, and isotopic dilution experiments using 12CO13CO mixtures showed that the CO molecules are free of dipole-dipole coupling after the redispersive treatment.
TL;DR: In this article, the authors studied the mechanism of the selective oxidation of ethylene to ethylene epoxide on a well-characterized Ag(110) surface by combining high-pressure kinetic measurements with ultrahigh vacuum surface analysis in a single apparatus.
TL;DR: In this paper, various aliphatic and aromatic nitro compounds were selectively and rapidly reduced to their corresponding amino derivatives in very good yield using anhydrous ammonium formate as a catalytic hydrogen transfer agent.
TL;DR: N-Substituted aziridines are formed by Fe- or Mn-Porphyrin catalysed reactions of PhlNR compounds (R = tosyl or COCF7) with alkenes; the stereochemical characteristics of these reactions are very different from those of the analogous epoxidation of theAlkenes by PhlO.
Abstract: N-Substituted aziridines are formed by Fe- or Mn-Porphyrin catalysed reactions of PhlNR compounds (R = tosyl or COCF7) with alkenes; the stereochemical characteristics of these reactions are very different from those of the analogous epoxidation of the alkenes by PhlO.
Book•
01 May 1984
TL;DR: In this paper, a transition metal-carbon monoxide interaction was studied. But the authors focused on the interaction between transition metal and transition metal surfaces and did not consider the interaction of transition metal with transition metal structures.
Abstract: 1 Introduction.- 1.1 References.- 2 Transition Metal-Hydrogen Interactions.- 2.1 Reaction of Hydrogen with Transition Metal Complexes and Surfaces.- 2.2 Metal-Hydrogen Bond Energy.- 2.3 Different Types of Metal-Hydrogen Bonding and the M-H Bond Length.- 2.4 Polarity of the M-H Bond.- 2.5 Mobility of Hydrogen Ligands.- 2.6 Conclusion.- 2.7 References.- 3 Transition Metal-Carbon Monoxide Interactions.- 3.1 The CO Molecule.- 3.2 Coordination Chemistry of CO in Molecular Complexes and Clusters.- 3.3 Molecular Carbon Monoxide on Metal Surfaces.- 3.4 CO Dissociation on Metal Surfaces.- 3.5 Conclusion.- 3.6 References.- 4 Non-Catalytic Interaction of CO with H2.- 4.1 On Metal Surfaces.- 4.2 CO/H2 Interaction in Transition Metal Complexes.- 4.2.1 Hydridocarbonyl Complexes.- 4.2.2 Formyl Complexes.- 4.2.3 Formaldehyde Complexes.- 4.2.4 A Methoxy Complex.- 4.2.5 Carbide Complexes.- 4.3 Conclusions.- 4.4 References.- 5 Key Reactions in Catalysis.- 5.1 Oxidative Addition.- 5.2 Reductive Elimination.- 5.2.1 Intramolecular Reductive Elimination.- 5.2.2 Intermolecular Reductive Elimination.- 5.3 Migratory Insertion Reactions.- 5.3.1 CO Insertion into Metal-Alkyl Bonds.- 5.3.2 Alkyl Migration versus CO Migration.- 5.3.3 Promotion of Migratory CO Insertion.- 5.3.4 Absence of Acyl-to-CO Migration.- 5.3.5 CO Insertion into Metal-H Bonds.- 5.3.6 Migratory Insertions involving Carbene Ligands.- 5.3.7 Olefin Insertion.- 5.3.8 Coinsertion of Ethylene and CO.- 5.3.9 Insertion of Formaldehyde.- 5.4 Hydrogen Eliminiation Reactions.- 5.4.1 ?-Hydrogen Elimination.- 5.4.2 ?-Elimination of Hydrogen.- 5.4.3 ?- and ?-Elimination of Hydrogen.- 5.5 Ligand Influences.- 5.5.1 In Molecular Complexes.- 5.5.2 On Metal Surfaces.- 5.6 Conclusion.- 5.7 References.- 6 Catalysts and Supports.- 6.1 Molecular Complexes and Metal Surfaces - Analogies and Differences.- 6.2 Supported Metal Catalysts.- 6.2.1 Metals and Supports Used for CO Hydrogenation.- 6.2.2 Metal-Support Interactions.- 6.2.3 Steric Constraints in Zeolites.- 6.3 Conclusions.- 6.4 References.- 7 Methanation.- 7.1 Carbide Mechanism.- 7.2 CO Insertion Mechanism.- 7.3 Inverse H/D Isotope Effects.- 7.4 Conclusion.- 7.5 References.- 8 Methanol from CO + H2.- 8.1 Nondissociative Incorporation of CO.- 8.2 Homogeneous Methanol Formation.- 8.3 Methanol Synthesis with Supported Noble Metal Catalysts.- 8.4 Synergism in the Cu/ZnO Catalyst.- 8.5 Conclusions.- 8.6 References.- 9 Fischer-Tropsch Synthesis.- 9.1 Early Developments and Present State of Commercial Fischer-Tropsch Synthesis.- 9.2 The Products of the FT Synthesis.- 9.2.1 Primary Products.- 9.2.2 Secondary Reactions of the ?-Olefins.- 9.2.3 Modified FT Synthesis.- 9.3 Distribution of Molecular Weights.- 9.3.1 The Schulz-Flory Distribution Function.- 9.3.2 Experimental Molecular Weight Distributions.- 9.4 Kinetics and Thermodynamics of the FT Reaction.- 9.5 Reaction Mechanism.- 9.5.1 Suggested Mechanisms.- 9.5.2 The Carbide Theory in the Light of Homogeneous Coordination Chemistry.- 9.5.3 Details and Support for the CO Insertion Mechanism.- 9.5.4 The Chain Initiating Step.- 9.5.5 Secondary Reactions.- 9.6 Influence of the Dispersity of Metal Centers.- 9.7 Influence of the Temperature and Pressure.- 9.7.1 Hydrocarbons versus Oxygenates.- 9.7.2 The Particular Case of Ruthenium Catalysts.- 9.8 The Role of Alkali Promoters.- 9.9 Product Selectivity.- 9.9.1 Consequences of the Schulz-Flory Molecular Weight Distribution.- 9.9.2 Deviations from the Schulz-Flory Distribution.- 9.10 Conclusion.- 9.11 References.- 10 Homogeneous CO Hydrogenation.- 10.1 Hydroformylation of Olefins (Oxo Reaction).- 10.2 Hydroformylation of Formaldehyde.- 10.3 Polyalcohols from CO + H2, and Related Homogeneous Syntheses.- 10.4 Conclusion.- 10.5 References.- 11 Methanol as Raw Material.- 11.1 Carbonylation of Methanol (Acetic Acid Synthesis)..- 11.2 Methanol Homologation.- 11.3 Hydrocarbons from Methanol Dehydration and Condensation.- 11.4 Conclusion.- 11.5 References.- 12 Attempt of a Unified View.- 12.1 References.- 13 Subject Index.
TL;DR: In this paper, a back-mixed flow reaction was carried out in a back mixed flow reactor in the presence of 0.04 wt.% Pd/Al 2 O 3 catalyst containing 0:100, 30:70, and 80:20 atoms Cu:atoms Pd.