Isotopic Labeling and Kinetic Isotope Effects

Bauer, Frank

doi:10.1002/9783527610044.hetcat0081

Cited by 4 publications

(2 citation statements)

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“…As shown in Table , a hydrogen/deuterium isotope effect was observed using perdeuterated ethanol for both acetaldehyde and ethylene formation, which we attribute to a primary kinetic isotope effect (KIE). Notably, there is also a small hydrogen/deuterium isotope effect when using ethanol-OD for acetaldehyde production, which could be an equilibrium isotope effect, or as discussed by Knözinger and Scheglila and Bauer, the value of this isotope effect represents the minimum KIE that would be expected in the limit of the high temperatures used in our reactions.…”

Section: Resultsmentioning

confidence: 79%

Reaction Kinetics Analysis of Ethanol Dehydrogenation Catalyzed by MgO–SiO₂

et al. 2020

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The Mg-catalyzed dehydrogenation of ethanol to yield acetaldehyde is an important step in the Lebedev reaction. In this work, we prepared a model MgO−SiO 2 catalyst by impregnation of MgO onto an SBA-15 support and used this material to study the reaction kinetics of ethanol dehydrogenation to acetaldehyde. The rates of acetaldehyde and ethylene production were measured for ethanol partial pressures ranging from 0.92 to 5.25 kPa. Both rates are fractional order at 723 K, decreasing to nearly zero-order at 648 K. Consistent with the literature for MgO−SiO 2 Lebedev catalysts, both basic sites and Lewis acidic sites were observed on this catalyst. The rates of both acetaldehyde and ethylene were inhibited by pyridine but not by 2,6-ditertbutylpyridine, suggesting that both reactions involve not only basic but also Lewis acidic sites. To elucidate the origin of this cooperativity, a microkinetic model was constructed using a recently published mechanism for the Lebedev reaction catalyzed by MgO. The model was fit to our data using four fitting parameters. The fitting suggests that adsorbed ethanol and hydrogen atoms have a weaker bond with mixed-oxide MgO−SiO 2 catalysts than with bulk MgO catalysts, which we attribute experimentally to an increase in the number of moderate-strength Mg 2+ − O 2− site pairs formed at the expense of strongly basic MgO sites.

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Section: Resultsmentioning

confidence: 79%

Reaction Kinetics Analysis of Ethanol Dehydrogenation Catalyzed by MgO–SiO₂

et al. 2020

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“…The 13 C labeling technique is another possible method, [17] for example, for kinetic studies of [ 12 C]ethene methylation by [ 13 C]methanol using GC-MS isotope analysis and 1 H and 13 C nuclear magnetic resonance (NMR) spectroscopy. [18] MRI can visualize a complex mass transport of compounds through a catalyst bed.…”

Section: Introductionmentioning

confidence: 99%

Three‐Dimensional Imaging of Surface Chemical Processes in Catalysis Using High‐Resolution Positron Emission Tomography

2013

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The positron emission tomography (PET) technique is a well‐known method in nuclear medicine for molecular imaging of biochemical functions in the human body, but it can also be applied to molecular imaging of the chemical processes on the surfaces of heterogeneous catalysts. Dynamic studies of adsorption, desorption, and realignment of 11C positron‐emitter‐labeled compounds can be performed. In the work reported herein, a small PET scanner with approximately 1.3 mm spatial resolution, originally dedicated for small‐animal studies, is applied to image the location and quantitative distribution of [11C]methanol in a catalyst bed of approximately 8 cm3 volume in three dimensions. The PET imaging technique in combination with radio‐gas chromatographic analysis was also used to study different strengths of chemical bonds during catalytic processes on fresh and used Linde A‐type zeolites as catalysts. The PET technique has been highly developed in the last few years with higher resolution and sensitivity and improved image reconstruction algorithms. The commercial human and small‐animal PET scanners have great potential for imaging of well‐functioning, poorly functioning, or partially covered catalyst surfaces in academic and industrial research for the development of catalysts. High‐resolution PET scanning is a great catalysis imaging technique because of both axial and radial imaging of the catalyst bed; therefore, the distribution of radioactive compounds is analyzable in the total catalyst volume.

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On‐Surface Hydrogen/Deuterium Isotope Exchange in Polycyclic Aromatic Hydrocarbons

Wäckerlin

2021

Angewandte Chemie

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Hydrogen plays important roles in the on-surface synthesis of carbon-based materials in ultra-high vacuum. The complex interplay between hydrogen and surface-adsorbed polycyclic aromatic hydrocarbons (PAHs) is tracked by in situ time-of-flight secondary ion mass spectrometry (ToF-SIMS) combined with isotope labeling. In situ deuterium labeling of prototypical PAHs, coronene (CR) and 7-armchair graphene nanoribbons (GNRs), on Au(111) is achieved by annealing either in D 2 gas or in the vapor of perdeuterio-acenaphthene. By following the mass spectra of in situ deuterated CR mixed with hydrogen-CR, it is demonstrated that PAHs adsorbed at hot Au(111) surfaces continuously exchange hydrogen atoms. Also, D 2 present during the Ullmann coupling step leads to incorporation of deuterium and to shorter GNRs.

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Isotopic Labeling and Kinetic Isotope Effects

Abstract: The sections in this article are Introduction Synthesis and Analysis of Labeled Compounds Kinetic Isotope Effects Applications of Labeled Compounds Carbon Isotopes ( 11 C , 13 C , 14 C ) … Show more

Cited by 4 publications

References 152 publications

Reaction Kinetics Analysis of Ethanol Dehydrogenation Catalyzed by MgO–SiO₂

Reaction Kinetics Analysis of Ethanol Dehydrogenation Catalyzed by MgO–SiO₂

Three‐Dimensional Imaging of Surface Chemical Processes in Catalysis Using High‐Resolution Positron Emission Tomography

On‐Surface Hydrogen/Deuterium Isotope Exchange in Polycyclic Aromatic Hydrocarbons

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Isotopic Labeling and Kinetic Isotope Effects

Abstract: The sections in this article are Introduction Synthesis and Analysis of Labeled Compounds Kinetic Isotope Effects Applications of Labeled Compounds Carbon Isotopes ( 11 C , 13 C , 14 C ) … Show more

Cited by 4 publications

References 152 publications

Reaction Kinetics Analysis of Ethanol Dehydrogenation Catalyzed by MgO–SiO2

Reaction Kinetics Analysis of Ethanol Dehydrogenation Catalyzed by MgO–SiO2

Three‐Dimensional Imaging of Surface Chemical Processes in Catalysis Using High‐Resolution Positron Emission Tomography

On‐Surface Hydrogen/Deuterium Isotope Exchange in Polycyclic Aromatic Hydrocarbons

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Reaction Kinetics Analysis of Ethanol Dehydrogenation Catalyzed by MgO–SiO₂

Reaction Kinetics Analysis of Ethanol Dehydrogenation Catalyzed by MgO–SiO₂