Marjolein Velthoen

PhD Candidate
Employed since: September 2014
Phone: +31 6 22736375
Room: 4th floor study area



Lewis acidity probing methods for polymerization, cracking and hydroprocessing catalysts

Sponsor: Albemarle

This research aims for the development of chemical imaging tools enabling the visualization of Lewis acidic sites in three different catalytic systems: Fluid catalytic cracking (FCC) catalysts, hydroprocessing catalysts (HPC) and metallocene polymerization catalysts. This project is carried out in collaboration with Ara Muñoz Murillo, who works in our group as a postdoc

Metallocenes in combination with methylaluminoxane as a cocatalyst form extremely active catalysts for olefin polymerization. Moreover, the choice of ligand determines the zirconocene symmetry and chirality, leading towards a different tacticity of the resulting polymers.[1] In this catalyst, the zirconocene precursor is believed to be activated by the Lewis acidic sites from the silica-supported methylaluminoxane. The chloride ligands are hereby extracted and partially replaced with methyl groups by the MAO, creating a vacant site for ethylene polymerization, as can be seen in Figure 1.

My project involves the use of micro-spectroscopic techniques in combination with probe molecules to determine the strength and distribution of the Lewis acidic sites on the supported MAO and, subsequently, the distribution of the active zirconocene species with the aim to correlate the results to the catalyst polymerization activity. This micro-spectroscopic study of the solid catalyst builds on previously reported spectroscopic studies of this system in solution.[2] Furthermore, the UV-Vis micro-spectroscopic study of single particles is compared to in-situ UV-Vis DRS measurements during gas phase polymerization reactions.

Figure 1: The zirconocene precursor is activated by the Lewis acidic sites of the silica-supported MAO, yielding the active species for olefin polymerization.

[1] Kaminsky, Catalysis Today 20, 257 – 271 (1994)
[2] D. Coevoet et al., Macromol. Chem. Phys. 199, 1451 – 1457 (1998)




2014 – present:
PhD research at the department of Inorganic Chemistry and Catalysis, Utrecht University under the supervision of Prof. dr. ir. B.M. Weckhuysen

Half year research project at SUNCAT center for interface science and catalysis, Stanford University, USA

2012 – 2014:
Master’s degree: “Nanomaterials: Chemistry and Physics”, Utrecht University
Thesis: “Study of Acidic and Basic Properties of Silica-Magnesia Catalysts in the Conversion of Ethanol into 1,3-Butadiene” (supervision of C. Angelici, dr P.C.A. Bruijnincx and prof. B.M. Weckhuysen)

2009 – 2012:
Bachelor’s degree in Chemistry, Utrecht University
Thesis: “Influence of Particle Size and Distribution in Nickel/Silica catalysts on deactivation during methanation” (supervision of P. Munnik and prof. K.P. de Jong)

2003 – 2009:
Secondary School: “Christelijk Lyceum Zeist”, the Netherlands

Born June 29th in Zeist, the Netherlands


Velthoen, M E Z; Nab, S; Weckhuysen, B M

Probing acid sites in solid catalysts with pyridine UV-Vis spectroscopy Journal Article

Physical Chemistry Chemical Physics, 20 (33), pp. 21647-21659, 2018, (cited By 0).

Links | BibTeX

Velthoen, M E Z; Boereboom, J M; Bulo, R E; Weckhuysen, B M

Insights into the activation of silica-supported metallocene olefin polymerization catalysts by methylaluminoxane Journal Article

Catalysis Today, 2018, (cited By 0; Article in Press).

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Velthoen, M E Z; Muñoz-Murillo, A; Bouhmadi, A; Cecius, M; Diefenbach, S; Weckhuysen, B M

The Multifaceted Role of Methylaluminoxane in Metallocene-Based Olefin Polymerization Catalysis Journal Article

Macromolecules, 51 (2), pp. 343-355, 2018, (cited By 6).

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Velthoen, M E Z; Meeldijk, J D; Meirer, F; Weckhuysen, B M

Intra- and Interparticle Heterogeneities in Solid Activators for Single-Site Olefin Polymerization Catalysis as Revealed by Micro-Spectroscopy Journal Article

Chemistry - A European Journal, 24 (46), pp. 11944-11953, 2018, (cited By 1).

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Piovano, A; Pletcher, P; Velthoen, M E Z; Zanoni, S; Chung, S -H; Bossers, K; Jongkind, M K; Fiore, G; Groppo, E; Weckhuysen, B M

Genesis of MgCl2-based Ziegler-Natta Catalysts as Probed with Operando Spectroscopy Journal Article

ChemPhysChem, 19 (20), pp. 2662-2671, 2018, (cited By 0).

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Mance, D; der Zwan, Van J; Velthoen, M E Z; Meirer, F; Weckhuysen, B M; Baldus, M; Vogt, E T C

A DNP-supported solid-state NMR study of carbon species in fluid catalytic cracking catalysts Journal Article

Chemical Communications, 53 (28), pp. 3933-3936, 2017, (cited By 7).

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Angelici, C; Velthoen, M E Z; Weckhuysen, B M; Bruijnincx, P C A

Influence of acid-base properties on the Lebedev ethanol-to-butadiene process catalyzed by SiO<inf>2</inf>-MgO materials Journal Article

Catalysis Science and Technology, 5 (5), pp. 2869-2879, 2015, (cited By 53).

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Munnik, P; Velthoen, M E Z; Jongh, De P E; Jong, De K P; Gommes, C J

Nanoparticle growth in supported nickel catalysts during methanation reaction - Larger is better Journal Article

Angewandte Chemie - International Edition, 53 (36), pp. 9493-9497, 2014, (cited By 38).

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Angelici, C; Velthoen, M E Z; Weckhuysen, B M; Bruijnincx, P C A

Effect of Preparation Method and CuO Promotion in the Conversion of Ethanol into 1,3-Butadiene over SiO2–MgO Catalysts Journal Article

ChemSusChem, 7 (9), pp. 2505-2515, 2014, (cited By 61).

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