X-Ray Imaging of SAPO-34 Molecular Sieves at the Nanoscale: Influence of Steaming on the Methanol-to-Hydrocarbons Reaction

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Title: X-Ray Imaging of SAPO-34 Molecular Sieves at the Nanoscale: Influence of Steaming on the Methanol-to-Hydrocarbons Reaction
Authors: Aramburo, Luis R. | Ruiz Martínez, Javier | Sommer, Linn | Arstad, Bjørnar | Buitrago Sierra, Robison | Sepúlveda-Escribano, Antonio | Zandbergen, Henny W. | Olsbye, Unni | Groot, Frank M.F. de | Weckhuysen, Bert M.
Research Group/s: Materiales Avanzados
Center, Department or Service: Universidad de Alicante. Departamento de Química Inorgánica | Universidad de Alicante. Instituto Universitario de Materiales
Keywords: Carbon | Hydrocarbons | Hydrothermal treatment | Molecular sieves | X-ray absorption
Knowledge Area: Química Inorgánica
Issue Date: Jun-2013
Publisher: Wiley-VCH Verlag GmbH & Co. KGaA
Citation: ChemCatChem. 2013, 5(6): 1386-1394. doi:10.1002/cctc.201200670
Abstract: The effect of a severe steaming treatment on the physicochemical properties and catalytic performance of H-SAPO-34 molecular sieves during the methanol-to-hydrocarbons (MTH) reaction has been investigated with a combination of scanning transmission X-ray microscopy (STXM), catalytic testing, and bulk characterization techniques, including ammonia temperature programmed desorption and 27Al and 29Si magic angle spinning nuclear magnetic resonance. For this purpose, two samples, namely a calcined and a steamed H-SAPO-34 catalyst powder, have been compared. It has been found that calcined H-SAPO-34 displays a high selectivity towards light olefins, yet shows a poor stability as compared to a zeolite H-ZSM-5 catalyst. Moreover, in situ STXM at the carbon K-edge during the MTH reaction allows construction of nanoscale chemical maps of the hydrocarbon species formed within the H-SAPO-34 aggregates as a function of reaction time and steam post-treatment. It was found that there is an initial preferential formation of coke precursor species within the core of the H-SAPO-34 aggregates. For longer times on stream the formation of the coke precursor species is extended to the outer regions, progressively filling the entire H-SAPO-34 catalyst particle. In contrast, the hydrothermally treated H-SAPO-34 showed similar reaction selectivity, but decreased activity and catalyst stability with respect to its calcined counterpart. These variations in MTH performance are related to a faster and more homogeneous formation of coke precursor species filling up the entire steamed H-SAPO-34 catalyst particle. Finally, the chemical imaging capabilities of the STXM method at the Al and Si K-edge are illustrated by visualizing the silicon islands at the nanoscale before and after steaming H-SAPO-34.
URI: http://hdl.handle.net/10045/39544
ISSN: 1867-3880 (Print) | 1867-3899 (Online)
DOI: 10.1002/cctc.201200670
Language: eng
Type: info:eu-repo/semantics/article
Rights: © 2013 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim
Peer Review: si
Publisher version: http://dx.doi.org/10.1002/cctc.201200670
Appears in Collections:INV - LMA - Artículos de Revistas

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