Computational Study of the Effect of Confinement within Microporous Structures on the Activity and Selectivity of Metallocene Catalysts for Ethylene Oligomerization

Handle URI:
http://hdl.handle.net/10754/597826
Title:
Computational Study of the Effect of Confinement within Microporous Structures on the Activity and Selectivity of Metallocene Catalysts for Ethylene Oligomerization
Authors:
Toulhoat, Hervé; Lontsi Fomena, Mireille; de Bruin, Theodorus
Abstract:
The effect of confinement within some zeolitic structures on the activity and selectivity of metallocene catalysts for the ethylene oligomerization has been investigated using grand canonical Monte Carlo simulations (GCMC). The following zeolite (host) frameworks displaying different pore sizes, have been studied as solid hosts: mazzite (MAZ), AIPO-8 (AET), UTD-1F (DON), faujasite (FAU), and VPI-5 (VFI). Intermediates and transition states involved in the ethylene trimerization reaction catalyzed by a Ti-based catalyst [(η5-C5H4CMe2C6H 5)TiCl3/MAO] have been used as sorbates (guests). We have demonstrated linear correlations with slope aH,j between the adsorption enthalpy and the molecular volume Vm of the sorbates, each holding for a given microporous host below a host-specific threshold V mmax,j. Beyond this maximal molecular volume, the adsorption vanishes due to steric exclusion. aH,j increases, and Vmmax,j decreases with decreasing host pore size, in line with the confinement concept. We moreover showed that, in the limit of vanishing loading (Henry regime), the enthalpies and entropies of adsorption in a given host are linearly correlated. We have defined a host-specific confinement compensation temperature a j, which refers to a temperature where the stabilizing adsorption enthalpic interactions are canceled out against the loss in entropy. However, calculated aj are much larger than the operating temperatures. With a setup microkinetic model, we predict that the activity and selectivity of the confined Ti-catalyst in ethylene oligomerization can be significantly altered with respect to homogeneous phase conditions, since the adsorption free energies of transition states and intermediates also become functions of aH,j and Vm. We have applied this theory to predict the optimum host pore size to get maximum α-octene production, instead of α-hexene, which is primarily produced in the homogeneous phase. We also predict a significantly increased activity for confined catalysts. © 2011 American Chemical Society.
Citation:
Toulhoat H, Lontsi Fomena M, de Bruin T (2011) Computational Study of the Effect of Confinement within Microporous Structures on the Activity and Selectivity of Metallocene Catalysts for Ethylene Oligomerization. Journal of the American Chemical Society 133: 2481–2491. Available: http://dx.doi.org/10.1021/ja105950z.
Publisher:
American Chemical Society (ACS)
Journal:
Journal of the American Chemical Society
KAUST Grant Number:
UK-C0017
Issue Date:
2-Mar-2011
DOI:
10.1021/ja105950z
PubMed ID:
21302923
Type:
Article
ISSN:
0002-7863; 1520-5126
Sponsors:
This work was supported by Award No. UK-C0017, made by King Abdullah University of Science and Technology (KAUST).
Appears in Collections:
Publications Acknowledging KAUST Support

Full metadata record

DC FieldValue Language
dc.contributor.authorToulhoat, Hervéen
dc.contributor.authorLontsi Fomena, Mireilleen
dc.contributor.authorde Bruin, Theodorusen
dc.date.accessioned2016-02-25T12:57:22Zen
dc.date.available2016-02-25T12:57:22Zen
dc.date.issued2011-03-02en
dc.identifier.citationToulhoat H, Lontsi Fomena M, de Bruin T (2011) Computational Study of the Effect of Confinement within Microporous Structures on the Activity and Selectivity of Metallocene Catalysts for Ethylene Oligomerization. Journal of the American Chemical Society 133: 2481–2491. Available: http://dx.doi.org/10.1021/ja105950z.en
dc.identifier.issn0002-7863en
dc.identifier.issn1520-5126en
dc.identifier.pmid21302923en
dc.identifier.doi10.1021/ja105950zen
dc.identifier.urihttp://hdl.handle.net/10754/597826en
dc.description.abstractThe effect of confinement within some zeolitic structures on the activity and selectivity of metallocene catalysts for the ethylene oligomerization has been investigated using grand canonical Monte Carlo simulations (GCMC). The following zeolite (host) frameworks displaying different pore sizes, have been studied as solid hosts: mazzite (MAZ), AIPO-8 (AET), UTD-1F (DON), faujasite (FAU), and VPI-5 (VFI). Intermediates and transition states involved in the ethylene trimerization reaction catalyzed by a Ti-based catalyst [(η5-C5H4CMe2C6H 5)TiCl3/MAO] have been used as sorbates (guests). We have demonstrated linear correlations with slope aH,j between the adsorption enthalpy and the molecular volume Vm of the sorbates, each holding for a given microporous host below a host-specific threshold V mmax,j. Beyond this maximal molecular volume, the adsorption vanishes due to steric exclusion. aH,j increases, and Vmmax,j decreases with decreasing host pore size, in line with the confinement concept. We moreover showed that, in the limit of vanishing loading (Henry regime), the enthalpies and entropies of adsorption in a given host are linearly correlated. We have defined a host-specific confinement compensation temperature a j, which refers to a temperature where the stabilizing adsorption enthalpic interactions are canceled out against the loss in entropy. However, calculated aj are much larger than the operating temperatures. With a setup microkinetic model, we predict that the activity and selectivity of the confined Ti-catalyst in ethylene oligomerization can be significantly altered with respect to homogeneous phase conditions, since the adsorption free energies of transition states and intermediates also become functions of aH,j and Vm. We have applied this theory to predict the optimum host pore size to get maximum α-octene production, instead of α-hexene, which is primarily produced in the homogeneous phase. We also predict a significantly increased activity for confined catalysts. © 2011 American Chemical Society.en
dc.description.sponsorshipThis work was supported by Award No. UK-C0017, made by King Abdullah University of Science and Technology (KAUST).en
dc.publisherAmerican Chemical Society (ACS)en
dc.titleComputational Study of the Effect of Confinement within Microporous Structures on the Activity and Selectivity of Metallocene Catalysts for Ethylene Oligomerizationen
dc.typeArticleen
dc.identifier.journalJournal of the American Chemical Societyen
dc.contributor.institutionIFP Energies nouvelles, Rueil-Malmaison, Franceen
kaust.grant.numberUK-C0017en
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