Center for Molecular Modeling - B. Ensing

Acidity constant (pKa) calculation of large solvated dye molecules: evaluation of two advanced molecular dynamics methods

michel — Sat, 09 Jul 2016 19:46:50 +0000

T. De Meyer, B. Ensing, S.M.J. Rogge, K. De Clerck, E.J. Meijer, V. Van Speybroeck

ChemPhysChem

17 (21), 3447–3459

2016

Abstract

pH-sensitive dyes are increasingly applied onto polymer substrates for the creation of novel sensor materials. Recently, these dye molecules have been modified to form a covalent bond with the polymer host. This can have a large influence on the pH-sensitive properties, in particular on the acidity constant (pKa). Obtaining molecular control over the factors that influence the pK$_a$ value is mandatory for future intelligent design of sensor materials. Herein, we show that advanced molecular dynamics (MD) methods have reached the level where pKa values of large solvated dye molecules can be predicted with high accuracy. Two MD methods are used in this work: steered or restrained MD and the insertion/deletion scheme. Both are first calibrated on a set of phenol derivatives and afterwards applied to the dye molecule Bromothymol Blue. Excellent agreement with experimental values is obtained, which opens perspectives for using these methods for designing dye molecules.

Open Access version available at UGent repository

DOI

http://dx.doi.org/10.1002/cphc.201600734

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Meyer_et_al-2016-ChemPhysChem.pdf

Insight into the Effect of Water on the Methanol-to-Olefins Conversion in H-SAPO-34 from Molecular Simulations and in Situ Microspectroscopy

kristof — Thu, 04 Jun 2015 13:20:59 +0000

K. De Wispelaere, C.S. Wondergem, B. Ensing, K. Hemelsoet, E.J. Meijer, B.M. Weckhuysen, V. Van Speybroeck, J. Ruiz-Martinez

ACS Catalysis

6, 1991-2002

2016

Abstract

The role of water in the methanol-to-olefins (MTO) process over H-SAPO-34 has been elucidated by a combined theoretical and experimental approach, encompassing advanced molecular dynamics simulations and in-situ micro-spectroscopy. First principle calculations at the molecular level point out that water competes with methanol and propene for direct access to the Brønsted acid sites. This results in less efficient activation of these molecules, which are crucial for the formation of the hydrocarbon pool. Furthermore, lower intrinsic methanol reactivity towards methoxide formation has been observed. These observations are in line with a longer induction period observed from in-situ UV-Vis micro-spectroscopy experiments. These experiments revealed a slower and more homogeneous discoloration of H-SAPO-34, while in-situ confocal fluorescence microscopy confirmed the more homogeneous distribution and larger amount of MTO intermediates when co-feeding water. As such it is show that water induces a more efficient use of the H-SAPO-34 catalyst crystals at the microscopic level. The combined experimental theoretical approach gives a profound insight into the role of water on the catalytic process at the molecular and single particle level.

DOI

http://dx.doi.org/10.1021/acscatal.5b02139

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acscatal%2E5b02139.pdf

Complex reaction environments and competing reaction mechanisms in zeolite catalysis: insights from advanced molecular dynamics

kristof — Fri, 31 Oct 2014 14:33:45 +0000

K. De Wispelaere, B. Ensing, A. Ghysels, E.J. Meijer, V. Van Speybroeck

Chemistry - A European Journal

21 (26), 9385-9396

2015

Abstract

The methanol to olefins process is a show case example of complex zeolite-catalyzed chemistry. At real operating conditions, many factors such as framework flexibility, adsorption of various guest molecules and competitive reaction pathways, affect reactivity. In this paper we show the strength of first principle molecular dynamics techniques to capture this complexity by means of two case studies. Firstly, the adsorption behavior of methanol and water in H-SAPO-34 at 350 °C is investigated. Hereby we observed an important degree of framework flexibility and proton mobility. Secondly, we studied the methylation of benzene by methanol via a competitive direct and stepwise pathway in the AFI topology. Both case studies clearly show that a first principle molecular dynamics approach enables to obtain unprecedented insights into zeolite-catalyzed reactions at the nanometer scale.

Open Access version available at UGent repository

DOI

http://dx.doi.org/10.1002/chem.201500473

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15_ChemEurJ_xxxx_De_Wispelaere.pdf

De-Wispelaere_et_al-2015-Chemistry_-_A_European_Journal.pdf

Investigating the outstanding dynamic behavior of protons on UiO-66 defective sites

chiara — Mon, 29 Jan 2018 09:15:33 +0000

C. Caratelli, A. Tiwari, M. Waroquier, B. Ensing, E.J. Meijer, V. Van Speybroeck

ISBN/ISSN:

Poster

Conference / event / venue

EuroMOF 2017

Delft, The Netherlands

Sunday, 29 October, 2017 to Wednesday, 1 November, 2017

pKa calculations based on advanced MD simulations

thierry — Thu, 24 Dec 2015 15:48:08 +0000

T. De Meyer, B. Ensing, K. Hemelsoet, K. De Clerck, V. Van Speybroeck, E.J. Meijer

ISBN/ISSN:

Poster

Conference / event / venue

CHAINS 2015

Veldhoven, Amsterdam

Tuesday, 1 December, 2015 to Wednesday, 2 December, 2015

pKa calculations based on advanced MD simulations

thierry — Tue, 17 Nov 2015 09:52:46 +0000

T. De Meyer, B. Ensing, K. Hemelsoet, K. De Clerck, V. Van Speybroeck, E.J. Meijer

ISBN/ISSN:

Poster

Conference / event / venue

Holland Research School of Molecular Chemistry Symposium 2015

Vrije Universiteit, Amsterdam, The Netherlands

Thursday, 5 November, 2015

Exploring New Frontiers in Modeling Complex Zeolite-Catalyzed Reactions Using Advanced Molecular Dynamics Techniques

kristof — Mon, 16 Feb 2015 10:49:40 +0000

K. De Wispelaere, B. Ensing, A. Ghysels, E.J. Meijer, V. Van Speybroeck

O-Th-408-13

ISBN/ISSN:

Talk

Conference / event / venue

24th North American Catalysis Society Meeting (NAM24)

Pittsburgh, PA, USA

Sunday, 14 June, 2015 to Friday, 19 June, 2015

Abstract (private)

Abstract_NAM24_KDW.pdf

Abstract

Paper_12530_extendedabstract_3413_0.pdf

Conference reference

NAM24

The influence of proton mobility on the zeolite-catalyzed methanol conversion process

wim — Tue, 02 Dec 2014 07:32:57 +0000

K. De Wispelaere, B. Ensing, S.L. Moors, K. Hemelsoet, M. Waroquier, E.J. Meijer, V. Van Speybroeck

ISBN/ISSN:

Talk

Conference / event / venue

2nd Euro-Asia Zeolite Conference 2015

Nice, France

Sunday, 25 January, 2015 to Wednesday, 28 January, 2015

Abstract (private)

Abstract Euro-Asian Conference 2015 -KDW.pdf

Conference reference

2nd Euro-Asia Zeolite Conference 2015

Molecular dynamics kinetic study on the zeolite-catalyzed methanol conversion process

kristof — Tue, 04 Mar 2014 09:02:09 +0000

K. De Wispelaere, S.L. Moors, B. Ensing, K. Hemelsoet, E.J. Meijer, M. Waroquier, V. Van Speybroeck

ISBN/ISSN:

Talk

Conference / event / venue

15th Int. Conference of Theoretical Aspects of Catalysis (ICTAC-15)

London, United Kingdom

Monday, 30 June, 2014 to Friday, 4 July, 2014

Abstract (private)

Kristof_DeWispelaere.pdf

Conference reference

ICTAC-15

Unraveling the reaction mechanism of methanol conversion: insights from molecular dynamics simulations

kristof — Sat, 01 Feb 2014 14:35:14 +0000

K. De Wispelaere, B. Ensing, S.L. Moors, K. Hemelsoet, V. Van Speybroeck, E.J. Meijer

ISBN/ISSN:

Poster

Conference / event / venue

Study Group Meeting: Chemistry in Relation to Physics and Materials Sciences

Veldhoven, The Netherlands

Monday, 10 February, 2014 to Tuesday, 11 February, 2014