Center for Molecular Modeling - Q. Qian

Identification of intermediates in zeolite-catalyzed reactions using in-situ UV/Vis micro-spectroscopy and a complementary set of molecular simulations

michel — Sat, 18 May 2013 20:05:23 +0000

K. Hemelsoet, Q. Qian, T. De Meyer, K. De Wispelaere, B. De Sterck, B.M. Weckhuysen, M. Waroquier, V. Van Speybroeck

Chemistry - A European Journal

19, 49, 16595-16606

2013

Abstract

The optical absorption properties of (poly)aromatic hydrocarbons occluded in a nanoporous environment were investigated by theoretical and experimental methods. The carbonaceous species are an essential part of a working catalyst for the methanol-to-olefins (MTO) process. In situ UV/Vis microscopy measurements on methanol conversion over the acidic solid catalysts H-SAPO-34 and H-SSZ-13 revealed the growth of various broad absorption bands around 400, 480, and 580 nm. The cationic nature of the involved species was determined by interaction of ammonia with the methanol-treated samples. To determine which organic species contribute to the various bands, a systematic series of aromatics was analyzed by means of time-dependent density functional theory (TDDFT) calculations. Static gas-phase simulations revealed the influence of structurally different hydrocarbons on the absorption spectra, whereas the influence of the zeolitic framework was examined by using supramolecular models within a quantum mechanics/molecular mechanics framework. To fully understand the origin of the main absorption peaks, a molecular dynamics (MD) study on the organic species trapped in the inorganic host was essential. During such simulation the flexibility is fully taken into account and the effect on the UV/Vis spectra is determined by performing TDDFT calculations on various snapshots of the MD run. This procedure allows an energy absorption scale to be provided and the various absorption bands determined from in situ UV/Vis spectra to be assigned to structurally different species.

DOI

http://dx.doi.org/10.1002/chem.201301965

Private attachment

13_chem_eur_ j_xxx_Hemelsoet.pdf

Mechanistic Studies on Chabazite-Type Methanol-to-Olefin Catalysts: Insights from Time-Resolved UV/Vis Microspectroscopy Combined with Theoretical Simulations

michel — Fri, 02 Dec 2011 17:26:57 +0000

V. Van Speybroeck, K. Hemelsoet, K. De Wispelaere, Q. Qian, J. Van der Mynsbrugge, B. De Sterck, B.M. Weckhuysen, M. Waroquier

ChemCatChem

5 (1), 173-184

2013

Abstract

The formation and nature of active sites for methanol conversion over solid acid catalyst materials are studied by using a unique combined spectroscopic and theoretical approach. A working catalyst for the methanol-to-olefin conversion has a hybrid organic–inorganic nature in which a cocatalytic organic species is trapped in zeolite pores. As a case study, microporous materials with the chabazite topology, namely, H-SAPO-34 and H-SSZ-13, are considered with trapped (poly)aromatic species. First-principle rate calculations on methylation reactions and in situ UV/Vis spectroscopy measurements are performed. The theoretical results show that the structure of the organic compound and zeolite composition determine the methylation rates: 1) the rate increases by 6 orders of magnitude if more methyl groups are added on benzenic species, 2) transition state selectivity occurs for organic species with more than one aromatic core and bearing more than three methyl groups, 3) methylation rates for H-SSZ-13 are approximately 3 orders of magnitude higher than on H-SAPO-34 owing to its higher acidity. The formation of (poly)aromatic cationic compounds can be followed by using in situ UV/Vis spectroscopy because these species yield characteristic absorption bands in the visible region of the spectrum. We have monitored the growth of characteristic peaks and derived activation energies of formation for various sets of (poly)aromatic compounds trapped in the zeolite host. The formation–activation barriers deduced by using UV/Vis microspectroscopy correlate well with the activation energies for the methylation of the benzenic species and the lower methylated naphthalenic species. This study shows that a fundamental insight at the molecular level can be obtained by using a combined in situ spectroscopic and theoretical approach for a complex catalyst of industrial relevance.

DOI

http://dx.doi.org/10.1002/cctc.201200580

Private attachment

13_chemcatchem_5(1)173_VanSpeybroeck.pdf

13_chemcatchem_5(1)173_cover.pdf

Characterisation of aromatic and aliphatic MTO intermediates using theoretical excitation and emission spectra

wim — Mon, 13 Oct 2014 13:35:39 +0000

K. Hemelsoet, Q. Qian, K. De Wispelaere, T. De Meyer, J. Ruiz-Martinez, M. Waroquier, B.M. Weckhuysen, V. Van Speybroeck

ISBN/ISSN:

Poster

Conference / event / venue

6 th FEZA Conference 2014

Leipzig, Germany

Monday, 8 September, 2014 to Thursday, 11 September, 2014

Conference reference

FEZA 2014

A theoretical assignment scale of aromatic and aliphatic MTO intermediates

wim — Thu, 27 Feb 2014 12:59:24 +0000

K. Hemelsoet, Q. Qian, K. De Wispelaere, T. De Meyer, A. Van Yperen-De Deyne, M. Waroquier, B.M. Weckhuysen, V. Van Speybroeck

ISBN/ISSN:

Talk

Conference / event / venue

XVth Netherlands' Catalysis and Chemistry Conference (NCCC XV)

Noordwijkerhout, The Netherlands

Monday, 10 March, 2014 to Wednesday, 12 March, 2014

Abstract (private)

2014_Hemelsoet_NCCC2014.pdf

Conference reference

15th NCCC conference

Identification of intermediates in zeolite-catalyzed reactions using in-situ UV/Vis micro-spectroscopy and a complementary set of molecular simulations

wim — Thu, 26 Sep 2013 12:59:15 +0000

K. Hemelsoet, Q. Qian, T. De Meyer, K. De Wispelaere, B.M. Weckhuysen, M. Waroquier, V. Van Speybroeck

ISBN/ISSN: -

Poster

Conference / event / venue

Annual IAP Meeting

Ghent, Belgium

Wednesday, 18 September, 2013

Conference reference

Annual IAP Meeting (2013)

Characterization of Methanol-to-Olefin Intermediates in Chabazite Zeolites using in-situ UV/Vis Microspectroscopy combined with Ab Initio Simulations

hemel — Thu, 23 May 2013 09:12:15 +0000

K. Hemelsoet, Q. Qian, K. De Wispelaere, T. De Meyer, A. Van Yperen-De Deyne, M. Waroquier, B.M. Weckhuysen, V. Van Speybroeck

ISBN/ISSN:

Talk

Conference / event / venue

XIth European Congress on Catalysis

Lyon - France

Sunday, 1 September, 2013 to Friday, 6 September, 2013

UV/Vis Spectra of Carbonaceous Methanol-to-Olefins Intermediates using TD-DFT combined with Molecular Dynamics

hemel — Wed, 22 May 2013 14:00:59 +0000

K. Hemelsoet, K. De Wispelaere, T. De Meyer, A. Van Yperen-De Deyne, M. Waroquier, V. Van Speybroeck, Q. Qian, B.M. Weckhuysen

ISBN/ISSN:

Talk

Conference / event / venue

TD-DFT Conference

Nantes, France

Tuesday, 23 April, 2013 to Friday, 26 April, 2013

Abstract (private)

2013_TD-DFT_Nantes.pdf

A combined theoretical and in-situ spectroscopy study to obtain mechanistic insight into active MTO routes in chabazite derived topologies

wim — Tue, 10 Jul 2012 12:04:07 +0000

V. Van Speybroeck, K. Hemelsoet, K. De Wispelaere, J. Van der Mynsbrugge, M. Waroquier, Q. Qian, B.M. Weckhuysen

p. **

Talk

Conference / event / venue

15th International Congress on Catalysis (ICC2012)

München, Germany

Sunday, 1 July, 2012 to Friday, 6 July, 2012

Abstract (private)

AbstractICC2012_VanSpeybroeck.pdf

Conference reference

ICC2012

Identification of Carbonaceous Compounds in H-SAPO-34: a Combined TDDFT and In-situ Spectroscopy Study

hemel — Thu, 19 Jan 2012 09:28:53 +0000

K. Hemelsoet, Q. Qian, K. De Wispelaere, J. Van der Mynsbrugge, M. Waroquier, B.M. Weckhuysen, V. Van Speybroeck

p. 74

Talk

Conference / event / venue

ZMPC2012

Hiroshima, Japan

Saturday, 28 July, 2012 to Wednesday, 1 August, 2012

Abstract (private)

ZMPC2012_Hemelsoet.pdf

Conference reference

ZMPC2012

Identification of Carbonaceous Compounds in H-SAPO-34: a Combined TDDFT and In-situ Spectroscopy Study

hemel — Thu, 19 Jan 2012 09:27:38 +0000

K. Hemelsoet, Q. Qian, K. De Wispelaere, M. Waroquier, B.M. Weckhuysen, V. Van Speybroeck

p. 44-45

Talk

Conference / event / venue

ICTAC-14

Vlissingen, The Netherlands

Tuesday, 26 June, 2012 to Saturday, 30 June, 2012

Abstract (private)

2012_ICTAC14_KHemelsoet.pdf

Conference reference

ICTAC-14