Effect of Interactions between Alkyl Chains and Solvent Structures on Lewis Acid Catalyzed Epoxidations

David S. Potts; Vijaya Sundar Jeyaraj; Ohsung Kwon; Richa Ghosh; Alexander V. Mironenko; David W. Flaherty

doi:10.1021/acscatal.2c03493

Effect of Interactions between Alkyl Chains and Solvent Structures on Lewis Acid Catalyzed Epoxidations

David S. Potts, Vijaya Sundar Jeyaraj, Ohsung Kwon, Richa Ghosh, Alexander V. Mironenko, David W. Flaherty

Chemical and Biomolecular Engineering

Research output: Contribution to journal › Article › peer-review

Abstract

Solvent molecules within zeolite pores provide interactions that influence the stability of reactive intermediates and impact rates and selectivities for catalytic reactions. We show the kinetic and thermodynamic consequences of these interactions and reveal their origins using alkene epoxidations in titanium-substituted *BEA (Ti-BEA) zeolites. Epoxidation turnover rates vary widely among primary n-alkenes (C₆-C₁₈) in hydrophilic (Ti-BEA-OH) and hydrophobic (Ti-BEA-F) catalysts in aqueous acetonitrile (CH₃CN). Apparent activation enthalpies (ΔH_app^‡) and entropies (ΔS_app^‡) increase with alkene carbon number in both catalysts; however, the span of ΔH_app^‡values in Ti-BEA-OH (68 kJ mol^-1) greatly exceeds that in Ti-BEA-F (18 kJ mol^-1). These trends, and commensurate gains in ΔS_app^‡, reflect the displacement and reorganization of solvent molecules that scale with the size of transition states and the numbers of solvent molecules stabilized by silanol defects near active sites. Experimental and computational assessments of intrapore solvent composition from ¹H NMR, infrared spectroscopy, and grand canonical molecular dynamics (GCMD) simulations show that Ti-BEA-OH uptakes larger quantities of both CH₃CN and H₂O than Ti-BEA-F. The Born-Haber decomposition of simulated enthalpies of adsorption (ΔH_ads,epox) for C₆-C₁₈epoxides attributes ΔH_ads,epoxthat become more endothermic for larger adsorbates to the displacement of greater numbers of solvent molecules bound to silanol defects into the bulk solvent. A strong correlation between ΔH_app^‡and ΔH_ads,epox(from GCMD and isothermal titration calorimetry) gives evidence that the disruption of solvent structures provides excess thermodynamic contributions (e.g., G^ϵ) that depend on the solvent composition in the pores, the excluded volume of reactive species, and the density of silanol groups near active sites. Altering G^ϵvalues offers opportunities to control selectivities and rates of reactions through the design of extended active site environments.

Original language	English (US)
Pages (from-to)	13372-13393
Number of pages	22
Journal	ACS Catalysis
Volume	12
Issue number	21
DOIs	https://doi.org/10.1021/acscatal.2c03493
State	Published - Nov 4 2022

Keywords

Born-Haber cycle
confinement effects
enthalpy decomposition
enthalpy of adsorption
molecular dynamics
solid-liquid interfaces
solvent structure
zeolites

ASJC Scopus subject areas

Catalysis
Chemistry(all)

Online availability

10.1021/acscatal.2c03493

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@article{d892aa83917643ff88d1b08b304aa646,

title = "Effect of Interactions between Alkyl Chains and Solvent Structures on Lewis Acid Catalyzed Epoxidations",

abstract = "Solvent molecules within zeolite pores provide interactions that influence the stability of reactive intermediates and impact rates and selectivities for catalytic reactions. We show the kinetic and thermodynamic consequences of these interactions and reveal their origins using alkene epoxidations in titanium-substituted *BEA (Ti-BEA) zeolites. Epoxidation turnover rates vary widely among primary n-alkenes (C6-C18) in hydrophilic (Ti-BEA-OH) and hydrophobic (Ti-BEA-F) catalysts in aqueous acetonitrile (CH3CN). Apparent activation enthalpies (ΔHapp‡) and entropies (ΔSapp‡) increase with alkene carbon number in both catalysts; however, the span of ΔHapp‡values in Ti-BEA-OH (68 kJ mol-1) greatly exceeds that in Ti-BEA-F (18 kJ mol-1). These trends, and commensurate gains in ΔSapp‡, reflect the displacement and reorganization of solvent molecules that scale with the size of transition states and the numbers of solvent molecules stabilized by silanol defects near active sites. Experimental and computational assessments of intrapore solvent composition from 1H NMR, infrared spectroscopy, and grand canonical molecular dynamics (GCMD) simulations show that Ti-BEA-OH uptakes larger quantities of both CH3CN and H2O than Ti-BEA-F. The Born-Haber decomposition of simulated enthalpies of adsorption (ΔHads,epox) for C6-C18epoxides attributes ΔHads,epoxthat become more endothermic for larger adsorbates to the displacement of greater numbers of solvent molecules bound to silanol defects into the bulk solvent. A strong correlation between ΔHapp‡and ΔHads,epox(from GCMD and isothermal titration calorimetry) gives evidence that the disruption of solvent structures provides excess thermodynamic contributions (e.g., Gϵ) that depend on the solvent composition in the pores, the excluded volume of reactive species, and the density of silanol groups near active sites. Altering Gϵvalues offers opportunities to control selectivities and rates of reactions through the design of extended active site environments.",

keywords = "Born-Haber cycle, confinement effects, enthalpy decomposition, enthalpy of adsorption, molecular dynamics, solid-liquid interfaces, solvent structure, zeolites",

author = "Potts, {David S.} and Jeyaraj, {Vijaya Sundar} and Ohsung Kwon and Richa Ghosh and Mironenko, {Alexander V.} and Flaherty, {David W.}",

note = "Funding Information: The authors thank Professor Damien Guironnet for the use of laboratory equipment for the synthesis of Ti-BEA-OH and preparation of H NMR sample solutions. The authors also thank Chris Torres for helpful discussions and for performing the N and Ar adsorption measurements. EDXRF, XRD, and DRUV–vis were carried out in the Frederick Seitz Materials Research Laboratory at the University of Illinois. N and Ar adsorptions were carried out in the Microanalysis Lab at the University of Illinois. This work used the Extreme Science and Engineering Discovery Environment (XSEDE) Stampede2 computational resources through allocation TG-CHM210004. XSEDE was supported by National Science Foundation grant number ACI-1548562. 1 2 2 Funding Information: This work was supported by the Department of Energy (DE-SC0010224). D.S.P. and R.G. acknowledge the National Science Foundation Graduate Research Fellowship program (DGE-1746047). Publisher Copyright: {\textcopyright} 2022 American Chemical Society. All rights reserved.",

year = "2022",

month = nov,

day = "4",

doi = "10.1021/acscatal.2c03493",

language = "English (US)",

volume = "12",

pages = "13372--13393",

journal = "ACS Catalysis",

issn = "2155-5435",

publisher = "American Chemical Society",

number = "21",

}

TY - JOUR

T1 - Effect of Interactions between Alkyl Chains and Solvent Structures on Lewis Acid Catalyzed Epoxidations

AU - Potts, David S.

AU - Jeyaraj, Vijaya Sundar

AU - Kwon, Ohsung

AU - Ghosh, Richa

AU - Mironenko, Alexander V.

AU - Flaherty, David W.

N1 - Funding Information: The authors thank Professor Damien Guironnet for the use of laboratory equipment for the synthesis of Ti-BEA-OH and preparation of H NMR sample solutions. The authors also thank Chris Torres for helpful discussions and for performing the N and Ar adsorption measurements. EDXRF, XRD, and DRUV–vis were carried out in the Frederick Seitz Materials Research Laboratory at the University of Illinois. N and Ar adsorptions were carried out in the Microanalysis Lab at the University of Illinois. This work used the Extreme Science and Engineering Discovery Environment (XSEDE) Stampede2 computational resources through allocation TG-CHM210004. XSEDE was supported by National Science Foundation grant number ACI-1548562. 1 2 2 Funding Information: This work was supported by the Department of Energy (DE-SC0010224). D.S.P. and R.G. acknowledge the National Science Foundation Graduate Research Fellowship program (DGE-1746047). Publisher Copyright: © 2022 American Chemical Society. All rights reserved.

PY - 2022/11/4

Y1 - 2022/11/4

N2 - Solvent molecules within zeolite pores provide interactions that influence the stability of reactive intermediates and impact rates and selectivities for catalytic reactions. We show the kinetic and thermodynamic consequences of these interactions and reveal their origins using alkene epoxidations in titanium-substituted *BEA (Ti-BEA) zeolites. Epoxidation turnover rates vary widely among primary n-alkenes (C6-C18) in hydrophilic (Ti-BEA-OH) and hydrophobic (Ti-BEA-F) catalysts in aqueous acetonitrile (CH3CN). Apparent activation enthalpies (ΔHapp‡) and entropies (ΔSapp‡) increase with alkene carbon number in both catalysts; however, the span of ΔHapp‡values in Ti-BEA-OH (68 kJ mol-1) greatly exceeds that in Ti-BEA-F (18 kJ mol-1). These trends, and commensurate gains in ΔSapp‡, reflect the displacement and reorganization of solvent molecules that scale with the size of transition states and the numbers of solvent molecules stabilized by silanol defects near active sites. Experimental and computational assessments of intrapore solvent composition from 1H NMR, infrared spectroscopy, and grand canonical molecular dynamics (GCMD) simulations show that Ti-BEA-OH uptakes larger quantities of both CH3CN and H2O than Ti-BEA-F. The Born-Haber decomposition of simulated enthalpies of adsorption (ΔHads,epox) for C6-C18epoxides attributes ΔHads,epoxthat become more endothermic for larger adsorbates to the displacement of greater numbers of solvent molecules bound to silanol defects into the bulk solvent. A strong correlation between ΔHapp‡and ΔHads,epox(from GCMD and isothermal titration calorimetry) gives evidence that the disruption of solvent structures provides excess thermodynamic contributions (e.g., Gϵ) that depend on the solvent composition in the pores, the excluded volume of reactive species, and the density of silanol groups near active sites. Altering Gϵvalues offers opportunities to control selectivities and rates of reactions through the design of extended active site environments.

AB - Solvent molecules within zeolite pores provide interactions that influence the stability of reactive intermediates and impact rates and selectivities for catalytic reactions. We show the kinetic and thermodynamic consequences of these interactions and reveal their origins using alkene epoxidations in titanium-substituted *BEA (Ti-BEA) zeolites. Epoxidation turnover rates vary widely among primary n-alkenes (C6-C18) in hydrophilic (Ti-BEA-OH) and hydrophobic (Ti-BEA-F) catalysts in aqueous acetonitrile (CH3CN). Apparent activation enthalpies (ΔHapp‡) and entropies (ΔSapp‡) increase with alkene carbon number in both catalysts; however, the span of ΔHapp‡values in Ti-BEA-OH (68 kJ mol-1) greatly exceeds that in Ti-BEA-F (18 kJ mol-1). These trends, and commensurate gains in ΔSapp‡, reflect the displacement and reorganization of solvent molecules that scale with the size of transition states and the numbers of solvent molecules stabilized by silanol defects near active sites. Experimental and computational assessments of intrapore solvent composition from 1H NMR, infrared spectroscopy, and grand canonical molecular dynamics (GCMD) simulations show that Ti-BEA-OH uptakes larger quantities of both CH3CN and H2O than Ti-BEA-F. The Born-Haber decomposition of simulated enthalpies of adsorption (ΔHads,epox) for C6-C18epoxides attributes ΔHads,epoxthat become more endothermic for larger adsorbates to the displacement of greater numbers of solvent molecules bound to silanol defects into the bulk solvent. A strong correlation between ΔHapp‡and ΔHads,epox(from GCMD and isothermal titration calorimetry) gives evidence that the disruption of solvent structures provides excess thermodynamic contributions (e.g., Gϵ) that depend on the solvent composition in the pores, the excluded volume of reactive species, and the density of silanol groups near active sites. Altering Gϵvalues offers opportunities to control selectivities and rates of reactions through the design of extended active site environments.

KW - Born-Haber cycle

KW - confinement effects

KW - enthalpy decomposition

KW - enthalpy of adsorption

KW - molecular dynamics

KW - solid-liquid interfaces

KW - solvent structure

KW - zeolites

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U2 - 10.1021/acscatal.2c03493

DO - 10.1021/acscatal.2c03493

M3 - Article

AN - SCOPUS:85140623227

SN - 2155-5435

VL - 12

SP - 13372

EP - 13393

JO - ACS Catalysis

JF - ACS Catalysis

IS - 21

ER -

Effect of Interactions between Alkyl Chains and Solvent Structures on Lewis Acid Catalyzed Epoxidations

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