Apparent linear relationship, compensation law and others. Part I

Norwisz, J.; Smieszek, Z.; Kolenda, Zygmunt

doi:10.1016/0040-6031(89)87199-0

Cited by 9 publications

(3 citation statements)

References 3 publications

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“…Correlation between Δ H int ‡ and Δ S int ‡ would not be expected based on reports in the literature (noted in the Introduction) that these quantities are structure-insensitive. Before examining these correlations, however, it is important to address the statistical treatment of uncertainties in Δ H app and Δ S app , because apparent correlations between these parameters can arise from correlations of errors in Δ H app and Δ S app , as well as from underlying physical phenomena. − As described in the Supporting Information (section S.5), the proper way to determine whether an apparent correlation between Δ H app and Δ S app is a statistical artifact is to first determine the 95% confidence regions in the Δ H app –Δ S app plane for each set of values for Δ H app and Δ S app . Correlation beyond these regions is statistically significant.…”

Section: Resultsmentioning

confidence: 99%

Effects of Zeolite Structural Confinement on Adsorption Thermodynamics and Reaction Kinetics for Monomolecular Cracking and Dehydrogenation of n-Butane

et al. 2016

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The effects of zeolite structure on the kinetics of n-butane monomolecular cracking and dehydrogenation are investigated for eight zeolites differing in the topology of channels and cages. Monte Carlo simulations are used to calculate enthalpy and entropy changes for adsorption (ΔHads-H+ and ΔSads-H+) of gas-phase alkanes onto Brønsted protons. These parameters are used to extract intrinsic activation enthalpies (ΔHint‡), entropies (ΔSint‡), and rate coefficients (kint) from measured data. As ΔSads-H+ decreases (i.e., as confinement increases), ΔHint‡ and ΔSint‡ for terminal cracking and dehydrogenation decrease for a given channel topology. These results, together with positive values observed for ΔSint‡, indicate that the transition states for these reactions resemble products. For central cracking (an earlier transition state), ΔHint‡ is relatively constant, while ΔSint‡ increases as ΔSads-H+ decreases because less entropy is lost upon protonation of the alkane. Concurrently, selectivities to terminal cracking and dehydrogenation decrease relative to central cracking because ΔSint‡ decreases for the former reactions. Depending on channel topology, changes in the measured rate coefficients (kapp) with confinement are driven by changes in kint or by changes in the adsorption equilibrium constant (Kads-H+). Values of ΔSint‡ and ΔHint‡ are positively correlated, consistent with weaker interactions between the zeolite and transition state and with the greater freedom of movement of product fragments within more spacious pores. These results differ from earlier reports that ΔHint‡ and ΔSint‡ are structure-insensitive and that kapp is dominated by Kads-H+. They also suggest that ΔSads-H+ is a meaningful descriptor of confinement for zeolites having similar channel topologies.

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Section: Resultsmentioning

confidence: 99%

Effects of Zeolite Structural Confinement on Adsorption Thermodynamics and Reaction Kinetics for Monomolecular Cracking and Dehydrogenation of n-Butane

et al. 2016

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“…Herein, the 95% confidence region is the region in the ln A − E a plane that the true values of the datum pair (ln A and E a ) should be located in at a confidence level of >95%. It can be drawn when the experimental error is known, and usually the experimental errors in ln A and E a are correlated in such a way that the confidence region is of an elliptical shape . Apparently, drawing the confidence regions is based on the same idea as drawing the error bars in Figure .…”

Section: 12 Experimental Values Are Obtained From Arrhenius or Van't ...mentioning

confidence: 99%

“…It can be drawn when the experimental error is known, and usually the experimental errors in ln A and E a are correlated in such a way that the confidence region is of an elliptical shape. 17 Apparently, drawing the confidence regions is based on the same idea as drawing the error bars in Figure 3.…”

Section: Experimental Values Are Obtained From Arrhenius or Van't Hof...mentioning

confidence: 99%