Tracer studies of acid-catalyzed reactions. V. Carbon-14 kinetic studies of n-butene isomerization over alumina and silica-alumina catalysts

Hightower, Joe W.; Hall, W. Keith

doi:10.1021/j100863a038

Cited by 101 publications

(10 citation statements)

References 3 publications

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“…Additional evidence for the differences in acid strength is derived from the product distribution in the cis -2-butene reaction. Differences in the ratio of trans -2-butene to 1-butene and catalyst acidity have been observed over various solid acids. − Higher trans -butene/1-butene ratios were associated with stronger solid acids. Misono et al speculated that the selective formation of one isomer over the other was due to differences in the energy barrier for their formation .…”

Section: Discussionmentioning

confidence: 99%

Acidity of Keggin-Type Heteropolycompounds Evaluated by Catalytic Probe Reactions, Sorption Microcalorimetry, and Density Functional Quantum Chemical Calculations

et al. 1998

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The acidity and its effects on reactivity of Keggin-type heteropolycompounds were examined by catalytic probe reactions, microcalorimetry of ammonia sorption, and density functional quantum chemical calculations. Phosphotungstic, phosphomolybdic, silicotungstic, and silicomolybdic acids were used as model compounds. The specific rates of double-bond isomerization of both 1-butene and cis-2-butene were orders of magnitude greater on the tungsten heteropolyacids than on molybdenum heteropolyacids, which suggests the tungsten-containing solids are stronger acids. The rate of double-bond isomerization over silicotungstic acid was similar to that over phosphotungstic acid, indicating the minor role of the heteroatom. Results from ammonia sorption microcalorimetry showed ΔH sorp on tungsten-based heteropolyacids was approximately 40 kJ mol-1 higher than the corresponding enthalpy obtained on molybdenum-based heteropolyacids. Residual waters of hydration significantly affected both reaction rates and sorption enthalpies. Quantum chemical calculations revealed the most energetically favorable site of the acidic proton to be a bridging oxygen atom in the anhydrous heteropolyacid. Calculations on structurally optimized small metal oxide clusters, as well as the complete Keggin unit, were used to determine the proton affinities by DFT methods. Regardless of cluster size, the proton affinity of a tungsten cluster was always lower than that of an analogous molybdenum cluster by about 20−40 kJ mol-1. The combination of results from experiments and quantum chemical calculations provides a consistent ranking of acid strength for this important class of solid catalysts.

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Section: Discussionmentioning

confidence: 99%

Acidity of Keggin-Type Heteropolycompounds Evaluated by Catalytic Probe Reactions, Sorption Microcalorimetry, and Density Functional Quantum Chemical Calculations

et al. 1998

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“…The isomerization of olefins was studied in a number of publications during the past (18)(19)(20)(21)(22)(23)(24)(25)(26)(27)(28)(29)(30)(31)(32)(33)(34)(35). Double-bond and cis-trans isomerization, as well as the skeletal rearrangement of these substances, were in the focus of interest (e.g., (18,19,33)).…”

Section: Introductionmentioning

confidence: 99%

Dehydrogenation of Light Alkanes over Zeolites

Narbeshuber

Brait

Seshan

et al. 1997

Journal of Catalysis

112

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The conversion of light paraffins to olefins and the secondary reactions of the unsaturated compounds were investigated on H-ZSM5 and H-Y zeolites between 733 and 823 K. Steady stateand transient response-isotope tracing studies revealed that two mechanisms of dehydrogenation are operative. The main pathway is represented by monomolecular, protolytic dehydrogenation. This reaction contributes most to steady state olefin production. Additionally, at the initial stages of the reaction, extra framework aluminum moieties are speculated to participate in high dehydrogenation activity. This pathway is blocked at later stages of the reaction by product (hydrogen) inhibition. The intrinsic rates of protolytic dehydrogenation and olefin desorption range in the same order of magnitude. At high protolytic dehydrogenation rates, olefin desorption represents the rate determining step. Depending on the process conditions, olefins undergo secondary cracking, oligomerization, or isomerization. The latter proceeds via intramolecular rearrangement, possibly via a cyclopropylcarbenium ion at high temperatures and low conversions. At reaction conditions where bimolecular cracking prevails, isomerization is concluded to occur via secondary cracking of di-or oligomers.

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“…Double‐bond migration, cis / trans isomerization, and skeletal isomerization are the characteristic isomerization transformations of alkenes in the presence of acidic catalysts . Double‐bond migration and cis / trans isomerization are facile transformations that can take place under mild conditions and they have been subject of intensive research to investigate the acidity of different catalysts , . Since the thermodynamic stability of alkenes increases with increasing number of substituents on the sp 2 carbon atoms, terminal alkenes exhibit the highest reactivity in double‐bond migration .…”

Section: Resultsmentioning

confidence: 99%

Experimental Investigation of the Reaction Network of Ethene to Propene over Ni/AlMCM‐41 Catalysts

Perea

Felischak

Wolff

et al. 2017

Chemie Ingenieur Technik

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The reaction network of the ethene-to-propene (ETP) reaction over Ni/AlMCM-41 catalysts was studied. This reaction consists of the dimerization of ethene, the isomerization of 1-butene, and the metathesis of ethene and 2-butene to propene. This work focused on the latter. ETP experiments followed by in situ diffuse reflectance infrared Fourier transform spectroscopy were carried out. Metathesis activities were evaluated by the isomerization of butenes, the metathesis of ethene and 2-butene, and the retro-metathesis of propene. Metathesis activities of Ni/AlMCM-41 catalysts were not observed. Thus, a conjunct polymerization of ethene to propene is proposed.

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Tracer studies of acid-catalyzed reactions. V. Carbon-14 kinetic studies of n-butene isomerization over alumina and silica-alumina catalysts

Cited by 101 publications

References 3 publications

Acidity of Keggin-Type Heteropolycompounds Evaluated by Catalytic Probe Reactions, Sorption Microcalorimetry, and Density Functional Quantum Chemical Calculations

Acidity of Keggin-Type Heteropolycompounds Evaluated by Catalytic Probe Reactions, Sorption Microcalorimetry, and Density Functional Quantum Chemical Calculations

Dehydrogenation of Light Alkanes over Zeolites

Experimental Investigation of the Reaction Network of Ethene to Propene over Ni/AlMCM‐41 Catalysts

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