Prof. Freek Kapteiijn (1952) is an Emeritus Professor of Catalysis Engineering at the Technical University of Delft. MSc in Chemistry and Mathematics, received his PhD on ‘Metathesis of alkenes’ in 1980 at the University of Amsterdam. After post-doc positions (Coal Science) in Amsterdam and Nancy (ENSIC), he became Associate professor in Amsterdam. Moved to Delft University of Technology in 1992, became ‘Anthonie van Leeuwenhoek professor’ in 1999, and from 2008 to 2019 chair of Catalysis Engineering, with visiting with visiting professorships at ETH Zürich, Tianjin and Zhejiang Normal University. Research interest focuses on the interplay of catalysis and engineering, comprising structured and multifunctional catalysts, adsorption, separation and (catalytic) membranes. Co-authored over 550 publications in peer-reviewed journals and as book chapters. He is a Clarivate Highly Citer Researcher.
Abstract:
Methanol is an important building block of chemicals via the methanol-to-hydrocarbons (MTH) process. Depending on zeolite catalyst used and reaction conditions the product spectrum can be controlled to certain extent, but still is a mixture of various species, i.e. olefins, paraffins and light aromatics. The complex process has been described as controlled by the ‘dual cycle’ mechanism taking place in the zeolite over organic intermediates, the so-called hydrocarbon pool (HCP). One cycle produces mainly olefins and the other predominantly aromatics and ethylene.
Much research has been and still is devoted to obtain more insight into the reaction mechanism, by revealing the HCP species responsible for the product selectivity, their concentration and their dynamics in the zeolite, the first C-C bond formation and the individual rates of product formation.
In our group we investigate these elements of the MTH process over H-ZSM-5 by transient operation using sequences of pulse injection of methanol and the use of 13C-12C isotope labelling.
In this presentation a new technique FASPA, Fast Scanning Pulse Analysis combined with GC analysis, is introduced. This allows the full quantitative analysis of the whole pulse response product mixture with seconds resolution. This allows the investigation of the MTH with both a temporal and, by using different amounts of catalysts, space resolution. During a methanol pulse to a clean catalyst the HCP build-up can be observed, and the full product spectrum is produced nearly instantaneously after this induction period in a very thin reactive zone. Isotope scrambling hardly occurs, so every new next methanol pulse forms its ‘own’ products.
When the methanol is fully converted the HCP disintegrates releasing still olefins and aromatics that undergo further reactions in the rest of the catalyst bed. The pulse responses are analyzed by the statistical method of moments, a methodology to analyze pulse responses, yielding insight in adsorption and reaction rate behaviour over the catalyst while eliminating the disturbing influence of standard catalysis equipment. Finally, some thoughts are given on the reaction mechanism over H-ZSM-5 and the dynamics of the HCP in this catalyst.