The deactivation of a composite catalyst based on HZSM-5 zeolite (agglomerated in a matrix using boehmite as a binder) has been studied during the transformation of dimethyl ether into light olefins. The location of the trapped/retained species (on the zeolite or on the matrix) has been analyzed by comparing the properties of the fresh and deactivated catalyst after runs at different temperatures, while the nature of those species has been studied using different spectroscopic and thermogravimetric techniques. The reaction occurs on the strongest acid sites of the zeolite micropores through olefins and alkyl-benzenes as intermediates. These species also condensate into bulkier structures (polyaromatics named as coke), particularly at higher temperatures and within the mesoand macropores of the matrix. The critical roles of the matrix and water in the reaction medium have been proved: both attenuating the effect of coke deposition.
Bibliographical noteFunding Information:
Acknowledgments: The financial support of this work was undertaken by the Ministry of Economy and Competitiveness of the Spanish Government, some cofounded with ERDF funds (Project CTQ2013-46172-P, CTQ2013-46173-R and CTQ2016-79646-P projects), by the Basque Government (Project IT748-13) and by the University of the Basque Country (UFI 11/39). M. Ibáñez is grateful for the postgraduate grant from the University of the Basque Country (No. UPV/EHU2016).
© 2017 by the authors. Licensee MDPI, Basel, Switzerland.
- Dimethyl ether (DME)
- Light olefins
- ZSM-5 (MFI) zeolite
ASJC Scopus subject areas
- Physical and Theoretical Chemistry