Center for Molecular Modeling - J. Ruiz-Martinez

Suppression of the Aromatic Cycle in Methanol-to-Olefins Reaction over ZSM-5 by Post-Synthetic Modification Using Calcium

kristof — Fri, 15 Jan 2016 15:18:56 +0000

I. Yarulina, S. Bailleul, A. Pustovarenko, J. Ruiz-Martinez, K. De Wispelaere, J. Hajek, B.M. Weckhuysen, K. Houben, M. Baldus, V. Van Speybroeck, F. Kapteijn, J. Gascon

ChemCatChem

8 (19) 3057–3063

2016

Abstract

Incorporation of Ca in ZSM-5 results in a twofold increase of propylene selectivity (53 %), a total light-olefin selectivity of 90 %, and a nine times longer catalyst lifetime (throughput 792 gMeOH gcatalyst−1) in the methanol-to-olefins (MTO) reaction. Analysis of the product distribution and theoretical calculations reveal that post-synthetic modification with Ca2+ leads to the formation of CaOCaOH+ that strongly weaken the acid strength of the zeolite. As a result, the rate of hydride transfer and oligomerization reactions on these sites is greatly reduced, resulting in the suppression of the aromatic cycle. Our results further highlight the importance of acid strength on product selectivity and zeolite lifetime in MTO chemistry.

DOI

http://dx.doi.org/10.1002/cctc.201600650

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Yarulina_et_al-2016-ChemCatChem.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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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