Catalysis

Haensel, Vladimir; Burwell, Robert L.

doi:10.1038/scientificamerican1271-46

Cited by 14 publications

(6 citation statements)

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“…The weak electron binding energy (ca. 0.5 eV) combined with the sharp peak observed in the photoelectron tOn leave at the Chemistry Department, University of Utah, Salt Lake City, UT 84112. spectrum supported their conjecture.2 Ab initio calculations3 by Cardy et al and by Ortiz gave further support to this novel (1) In 1985, the Bowen group reported photoelectron data on NH4" in its normal form (e.g., as solvated H~): Coe, J. V.; Snodgrass, J. T.; Freidhoff, C. B.; McHugh, K. M.; Bowen, K. H. J. Chem. Phys.…”

Section: Introductionmentioning

confidence: 76%

"Dougle-Rydberg" molecular anions

Gutowski¹,

Simons²,

Hernández³

et al. 1988

J. Phys. Chem.

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TABLE III: Relative Concentrations of Ethanes and Ethylenes in CH4/CD4 Experiment (FTIR Measurements) caled" obsd caled" obsd C¡H¡ 34 ± 2 36 ± 4 C^3 4 ± 2 34 ± 2 CD3CH3 49 ± 2 (49)» CD2CH2 49 ± 2 (51)6 C2D6 17 ± 2 15 ± 2 C2D4 17 ± 2 15 ± 2 "For kH/kB = 1.4 ± 0.1. 6By difference.other ethane and CD2CH2 is,the only other ethylene, the contribution of these species may be determined by difference. Table III presents these results together with calculated values based on the kinetic isotope effect (&hAd = 1.4 ± 0.1) and a statistical distribution since the mixed species are more likely than the symmetrical ones. The uncertainty in the magnitude of the kinetic isotope effect is due to the small difference in the results obtained with CH4 alone. The experimental results are in excellent agreement with the calculations and show that exchange of H and D in the product hydrocarbons is insignificant and that the product distribution reflects the relative concentrations of CH3 and CD3.The results may therefore be interpreted as confirmatory evidence for the coupling of methyl radicals in this catalytic system. However, the absence of any significant hydrogen exchange between CH4 and CD4 and also between the product C2 hydrocarbons is surprising since MgO exhibits activity for CH4/D2 exchange at 300 °C16 and activity for CH4/CD4 exchange at 400 °C.17 It is therefore likely that the methyl coupling reaction occurs almost exclusively in the gas phase. This is in agreement with Lunsford's conclusion10 that at least 40-45% of the C2 products were accounted for by gas-phase methyl coupling. The results also suggest that ethane is the source of the ethylene since the distribution of the deuteriated ethylenes is not significantly different from that of the ethanes. It is possible that conversion of ethane to ethylene also occurs predominantly in the gas phase since

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Section: Introductionmentioning

confidence: 76%

"Dougle-Rydberg" molecular anions

Gutowski¹,

Simons²,

Hernández³

et al. 1988

J. Phys. Chem.

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“…Haensel and Burwell [144] point out that catalysts play a major role in the production of goods worth more than $100 billion a year. Even slight improvements in the efficiency, selectivity, stability, and life of a catalyst can have considerable economic impact.…”

Section: Laboratory Applicationsmentioning

confidence: 99%

The National Measurement System for surface properties

Powell¹

1977

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“…However, some solid catalysts also employ catalytically inert portions of their surface for lateral dif'fusion of adsorbed molecules. In such cases efficient catalysis can occur despite a relatively low concentration of active sites ( Haensel and Burwell, 1971). In many biologically important cases, enzymes are present at low concentration and it becomes advantageous to embed the catalyst in a membrane.…”

Section: T4-e Colimentioning

confidence: 99%

Molecular Cytogenetics

1973

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in Gatlinburg, Tennessee. The subject of the symposium was Molecular Cytogenetics and the aim of the meeting was to bring together researchers interested in problems of chromosome organization, activity and regulation in prokaryotes and eukaryotes. Cytological, biochemical and genetic approaches to these questions were included since the collective information gained fr om these disciplines provides an integrated approach to genome structure and function.

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Catalysis

Cited by 14 publications

References 0 publications

"Dougle-Rydberg" molecular anions

"Dougle-Rydberg" molecular anions

The National Measurement System for surface properties

Molecular Cytogenetics

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