Showing papers in "Reaction Kinetics and Catalysis Letters in 1991"
TL;DR: The Cu complex Cu(L)nCl (L=2-propylamine) has been found to be an advantageous catalyst for the addition of polyhalogenated compounds to chloro substituted ethenes; the 1∶1 adducts were formed almost exclusively in up to 71% yield as discussed by the authors.
Abstract: The Cu complex Cu(L)nCl (L=2-propylamine) has been found to be an advantageous catalyst for the addition of polyhalogenated compounds to chloro substituted ethenes; the 1∶1 adducts were formed almost exclusively in up to 71% yield.
33 citations
TL;DR: In this paper, an updated mechanism for the Briggs-Rauscher reaction (also known as "Iodine clock" reaction) has been investigated by the principal component analysis of the rate sensitivity matrix.
Abstract: An updated mechanism for the Briggs-Rauscher reaction (also known as “Iodine Clock” reaction) has been investigated by the principal component analysis of the rate sensitivity matrix. The analysis revealed that five reactions of the 15-step model were redundant. The results of principal component and of rate-of-production analyses together gave an insight into the basic processes of the “Iodine Clock” reaction.
25 citations
TL;DR: In this paper, the authors analyzed the effect of temperature, acidity, initial concentration of hydrogen peroxide and quantity of added water on the stability of the Bray-Liebhafsky reaction.
Abstract: The resumption of oscillatory trains in the non-oscillatory region subsequent to completion of the last oscillation, as a phenomenon interesting for the stability of any reaction which can reach the oscillatory state in principle, is analyzed here for the case of the Bray-Liebhafsky reaction. It is shown that this effect is affected by temperature, acidity, initial concentration of hydrogen peroxide and quantity of added water.
21 citations
21 citations
TL;DR: In this article, a kinetic study has been carried out of the regeneration of a commercial Cr2O3/Al 2O3 catalyst by coke combustion, and the results obtained show that the reaction rate is several orders of magnitude higher than that obtained on catalysts without transition metals.
Abstract: A kinetic study has been carried out of the regeneration of a commercial Cr2O3/Al2O3 catalyst by coke combustion. The results obtained show that the reaction rate is several orders of magnitude higher than that obtained on catalysts without transition metals.
20 citations
TL;DR: In this paper, it was shown that the order with respect to hydrogen partial pressure (0.04) is extremely low and far removed from the value of unity often assumed for CuO-containing catalysts.
Abstract: For CuO/ZnO reduction has been shown [M. S. W. Vong et al., Catal. Lett.,4, 15 (1990)] to be faster and more extensive with CO than by H2 and here this is shown to be the case for CuO itself, this being so then it may be preferable to characterize CuO-containing catalysts by temperature-programmed reduction with CO than with H2. The activation energies of reduction (57–82 kJ/mol) are those expected for chemical reduction, but it is an important finding that the order with respect to hydrogen partial pressure (0.04) is extremely low and far removed from the value of unity often assumed. Different samples of CuO exhibit different reduction characteristics.
19 citations
TL;DR: In this article, the limits of electron transfer from the oxide surface to the acceptor in electron affinity were reported and the electron acceptors with electron affinity from 1.26 to 2.84 eV on two metal oxides have been studied.
Abstract: Adsorption of electron acceptors with electron affinity from 1.26 to 2.84 eV on two metal oxides have been studied. The limits of electron transfer from the oxide surface to the acceptor in electron affinity are reported.
19 citations
TL;DR: In this paper, the performance of isoprene synthesis from formaldehyde and isobutylene over CuSO4−MOx/SiO2 catalysts has been studied.
Abstract: Vapor-phase synthesis of isoprene from formaldehyde and isobutylene over CuSO4−MOx/SiO2 catalysts has been studied. The results show that CuSO4−MOx/SiO2 catalysts exhibit a good catalytic activity; especially when the metal oxides have appropriate basicity, is isoprene yield greatly enhanced. The results of product analysis indicate that there are side-reactions during isoprene production, which are isoprene hydrogenation, polymerization of isobutylene, copolymerization of isobutylene and isoprene, and reaction of C5 aldehyde and ketone formed during isoprene production. In addition, catalytic behavior of the catalysts and probable mechanism of side-reactions are discussed.
18 citations
TL;DR: In this article, the catalytic behavior of bifunctional Pt- or Pd-containing Zn- and Mn-ZSM-5 zeolites in ethane aromatization was investigated.
Abstract: The catalytic behavior of bifunctional Pt- or Pd-containing Zn- and Mn-ZSM-5 zeolites in ethane aromatization was investigated. The results are discussed considering the electronic interaction between metallic sites and electron acceptor sites of the support.
17 citations
TL;DR: In this paper, the formation of mono-and dicarbonyl species during CO adsorption has been theoretically studied in order to obtain a mathematical model of the adorption isotherms.
Abstract: The formation of mono- and dicarbonyl species during CO adsorption has been theoretically studied in order to obtain a mathematical model of the adsorption isotherms. The dependences proposed describe well the results of other authors and allow better utilization of the experimental data.
16 citations
TL;DR: In this paper, the reactivity of m=xylene, phenol and benzene over vanadium oxides layered on TiO2 and ZrO2 was observed by in situ FTIR spectroscopy.
Abstract: Reactivities of m=xylene, phenol and benzene over vanadium oxides layered on TiO2 and ZrO2 have been observed by in situ FTIR spectroscopy.
TL;DR: In this paper, a complex two-spike shape of CL oscillations is shown to be caused primarily by the sharp increase in the concentration of hydroxymalonyl radicals due to the drop in those of HOBr and BrO 2
Abstract: A complex “two-spike” shape of CL oscillations is shown to be caused primarily by the sharp increase in the concentration of hydroxymalonyl radicals due to the drop in those of HOBr and BrO
2
.
, reacting rapidly with these radicals and hydroxymalonic acid itself at the critical concentration of Br− in the system.
TL;DR: In this article, the conversion of propane into aromatic hydrocarbons was studied at 400-540°C, using H-ZSM-11, Zn-ZM-11 and ZSM-5 zeolites.
Abstract: The conversion of propane into aromatic hydrocarbons has been studied at 400–540°C, using H-ZSM-11, Zn-ZSM-11, H-ZSM-5 and Zn-ZSM-5 zeolites. The zinc-exchanged forms of ZSM-11 and ZSM-5 were more active and gave better aromatic selectivity. The aromatics yield increased with the temperature and BTX selectivity increased with space velocity.
TL;DR: In this paper, a method to measure concentrations of strong surface acceptor centers on aluminosilicate catalysts by their titration with a solution of TEMPON (2,2,6,6-tetramethyl-4-oxypiperidine-1-oxyl) is suggested.
Abstract: A method to measure concentrations of strong surface acceptor centers on aluminosilicate catalysts by their titration with a solution of TEMPON (2,2,6,6-tetramethyl-4-oxypiperidine-1-oxyl) is suggested. The concentration of these centers corresponds to that of CO test molecules for the strongest acceptor centers (νCO ⩾2210 cm−1) obtained using IR spectroscopy. It is shown that for ZSM-5 zeolites most of these centers are localized on their external surface.
TL;DR: In this article, a gas phase hydrogenation of m-xylene on palladium supported catalysts was studied and compared with the hydrogenation o -xylene, and the modification in the stereoselectivity of palladium due to an increase in the acidity of the support is explained in terms of an increased residence time of the reactive species on the active surface.
Abstract: Gas phase hydrogenation of m-xylene on palladium supported catalysts was studied and compared with the hydrogenation of o-xylene. The modification in the stereoselectivity of palladium due to an increase in the acidity of the support is explained in terms of an increased residence time of the reactive species on the active surface, leading to a product composition closer to that predicted by thermodynamics.
TL;DR: In this article, a series of cation-substituted forms of oxidized carbon has been prepared and the catalytic activity tested for 2-propanol decomposition.
Abstract: A series of cation-substituted forms of oxidized carbon has been prepared and the catalytic activity tested for 2-propanol decomposition. It was found that the carbons promote both dehydration and dehydrogenation of the alcohol. The products are propene, diisopropyl ether, and acetone, respectively. The cation exchange enhances the dehydrogenation activity at the expense of the dehydration activity.
TL;DR: Transalkylation of 2,6-di-tert-butyl-4-R-phenols over solid heteropoly acids (H3PW12O40, H4SiW 12O40/SiO2) in the presence of toluene or o-xylene as acceptors of a tertbutyl group at 100-140 °C produces 4-Rphenols with 92-98% yield (R = H, alkyl, aryl, etc.).
Abstract: Transalkylation of 2,6-di-tert-butyl-4-R-phenols over solid heteropoly acids (H3PW12O40, H4SiW12O40, H3PW12O40/SiO2, H4SiW12O40/SiO2) in the presence of toluene or o-xylene as acceptors of a tert-butyl group at 100–140 °C produces 4-R-phenols with 92–98% yield (R = H, alkyl, aryl, etc.). HPAs are effective catalysts for the transalkylation of p-cresol and 2, 6-ditert-butyl-4-methylphenol.
TL;DR: In this paper, the positive order with regard to CO concentration varies with the precise range of CO partial pressure and occurs with no evidence of Cu2O formation as reported (Porta et al. 1989).
Abstract: CO reduction of CuO in CuO/ZnO samples at 423 K isnot retarded by the support and occurs with no evidence of Cu2O formation as reported (Porta et al. 1989). The positive order with regard to CO concentration varies with the precise range of CO partial pressure.
TL;DR: In this paper, the effect of reduction temperature of the catalyst, reaction temperature, space velocity, and component of feed gas were examined on the catalyst for the hydrogenation of carbon dioxide.
Abstract: Hydrogenation of carbon dioxide was carried out over reduced Fe3O4 catalyst. Effect of reduction temperature of the catalyst, reaction temperature, space velocity, and component of feed gas were examined on the catalyst. From various experiments, the proper conditions for the hydrogenation of carbon dioxide are proposed. In addition, oxidation of the catalyst took place simultaneously during the hydrogenation of CO2.
TL;DR: Some transition metal (Co, Ni, Zn, Cd and mixed Ca−Cd, Co−Zn) phosphomolybdates, unsupported or supported on alumina, were tested as catalysts for the gas phase hydration of acetylene, with or without air, to acetaldehyde and acetic acid as mentioned in this paper.
Abstract: Some transition metal (Co, Ni, Zn, Cd and mixed Ca−Cd, Co−Zn) phosphomolybdates, unsupported or supported on alumina, were tested as catalysts for the gas phase hydration of acetylene, with or without air, to acetaldehyde and acetic acid.
TL;DR: In this paper, a self-catalytic effect attributed to Mn2+ ions was observed when studying the oxidation of L-threonine by permanganate ions, and the proposed mechanism includes two pathways of oxidation: one without participation of Mn2+, and the other catalyzed by them.
Abstract: A self-catalytic effect attributed to Mn2+ ions was observed when studying the oxidation of L-threonine by permanganate ions. The process obeys the rate equation:
$$ - d[MnO_4^ - ]/dt = k'_1 [MnO_4^ - ] + k'_2 [MnO_4^ - ][Mn^{2 + } ]$$
k1′ and k2′ being calculated using an autocatalytic kinetic scheme. The proposed mechanism includes two pathways of oxidation: one without participation of Mn2+ ions and the other catalyzed by them.
TL;DR: In this article, the authors deduced the thermodynamic data of vanadyl octaethylporphyrin VO(OEP) from experiments performed in a batch reactor. And they showed that the rate order relative to H2 is equal to one.
Abstract: Hydrogenation of the vanadyloctaethylporphyrin VO(OEP), is a reversible reaction which may occur without a catalyst. The thermodynamic data have been deduced from experiments performed in a batch reactor. Both ΔHo and ΔSo are positive; this can be explained by the aromatic character of chlorin, the reaction product. From a kinetic point of view, the rate order relative to H2 is equal to one.
TL;DR: In this article, the effect of metal precursor, support and reduction temperature on surface reduction of Pd on α-Al2O3 and SiO2 has been studied and it was shown that for catalysts prepared from PdCl2, temperatures as high as 450 °C are necessary to obtain surface Pd0.
Abstract: The effect of metal precursor, support and reduction temperature on the surface reduction of Pd on α-Al2O3 and SiO2 has been studied. For catalysts prepared from PdCl2, temperatures as high as 450 °C are necessary to obtain surface Pd0.
TL;DR: In this paper, SO2 and H2S are found to be strong poisons of metal rhodium and palladium catalysts for liquid-phase hydrogenation of 3-thiolene-1, 1-dioxide and thiophene.
Abstract: SO2 and H2S are found to be strong poisons of metal rhodium and palladium catalysts for liquid-phase hydrogenation of 3-thiolene-1, 1-dioxide and thiophene.
TL;DR: In this paper, the binding energies of Mg2p and 01s shift with Ar etching, which is related to the surface basicity of the MgO catalysts.
Abstract: High activity of magnesium oxide prepared by thermal decomposition of magnesium oxalate for the hydrogenation of 1,3-butadiene has been examined by XPS and IR, together with the isomerization of 1-butene. XPS spectra of MgO differed from those of two other MgO catalysts. With Ar etching, the binding energies of Mg2p and 01s shift, which is related to the surface basicity. Both basic and acidic sites are responsible for hydrogenation, but isomerization proceeds only on basic sites.
TL;DR: In this paper, selectivity of 1,2-cis-and 1, 2-trans-dimethylcyclohexane products was studied in o-xylene hydrogenation over Pt, Pd, Rh and Ru supported catalysts.
Abstract: Selectivity to 1,2-cis- and 1,2-trans-dimethylcyclohexane products was studied in o-xylene hydrogenation over Pt, Pd, Rh and Ru supported catalysts. The results show that selectivity is sensitive to particle size.
TL;DR: In this paper, the impregnation preparation of H-zeolite over amorphous aluminosilicate solids (cracking catalysts) is compared with new synthesis procedures based on sol-gel process.
Abstract: The impregnation preparation of H-zeolite over amorphous aluminosilicate solids (cracking catalysts) is compared with new synthesis procedures based on sol-gel process. The characterization results show that the H-zeolite reacts with the intermediates of the amorphous aluminosilicate.
TL;DR: In this paper, γ-Al2O3 was synthesized from trisec-butoxide by the sol-gel method and pH was varied during reaction and solvents of different polarity were used.
Abstract: γ-Al2O3 was synthesized from trisec-butoxide by the sol-gel method. pH was varied during reaction and solvents of different polarity were used. Solids with specific areas, greater than 200 m2/g, were obtained, which depend directly on the reaction parameters.
TL;DR: In the experimental praxis of our chemical laboratory, we have been surprised and impressed by a few uncontrollable results caused by plastics as discussed by the authors, which require careful consideration and control of the properties and quality of plastics before using them even in the simplest chemical experiments.
Abstract: In the experimental praxis of our chemical laboratory we have been surprised and impressed by a few uncontrollable results caused by plastics. These materials are generally considered to be chemically more or less unreactive and inert. Absorption and chemical degradation—especially during long use—can activate the surface of silicon rubber, polyethylene or teflon, which are constituents of tubes, reaction vessels, stirring bars and other parts of instruments. In a few cases catalytic activation can be interpreted in terms of the interaction between the microporous surfaces of plastics and reactants. These observations require careful consideration and control of the properties and quality of plastics before using them even in the simplest chemical experiments.