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Understanding the deactivation phenomena of small-pore Mo/H-SSZ-13 during methane dehydroaromatisation

DOI: 10.3390/molecules25215048 DOI Help

Authors: Miren Agote-aran (University College of London; Diamond Light Source) , Anna B. Kroner (Diamond Light Source) , David S. Wragg (University of Oslo) , Wojciech A. Sławiński (University of Oslo; University of Warsaw) , Martha Briceno (Johnson Matthey Technology Centre) , Husn U. Islam (Johnson Matthey Technology Centr) , Igor V. Sazanovich (Central Laser Facility, Research Complex at Harwell) , María E. Rivas (Johnson Matthey Technology Centre) , Andrew W. J. Smith (Johnson Matthey Technology Centre) , Paul Collier (Johnson Matthey Technology Centre) , Ines Lezcano-gonzalez (University College London; Research Complex at Harwell) , Andrew M. Beale (University College London; Research Complex at Harwell)
Co-authored by industrial partner: Yes

Type: Journal Paper
Journal: Molecules , VOL 25

State: Published (Approved)
Published: November 2020
Diamond Proposal Number(s): 11623

Open Access Open Access

Abstract: Small pore zeolites have shown great potential in a number of catalytic reactions. While Mo-containing medium pore zeolites have been widely studied for methane dehydroaromatisation (MDA), the use of small pore supports has drawn limited attention due to the fast deactivation of the catalyst. This work investigates the structure of the small pore Mo/H-SSZ-13 during catalyst preparation and reaction by operando X-ray absorption spectroscopy (XAS), in situ synchrotron powder diffraction (SPD), and electron microscopy; then, the results are compared with the medium pore Mo/H-ZSM-5. While SPD suggests that during catalyst preparation, part of the MoOx anchors inside the pores, Mo dispersion and subsequent ion exchange was less effective in the small pore catalyst, resulting in the formation of mesopores and Al2(MOO4)3 particles. Unlike Mo/H-ZSM-5, part of the Mo species in Mo/H-SSZ-13 undergoes full reduction to Mo0 during MDA, whereas characterisation of the spent catalyst indicates that differences also exist in the nature of the formed carbon deposits. Hence, the different Mo speciation and the low performance on small pore zeolites can be attributed to mesopores formation during calcination and the ineffective ion exchange into well dispersed Mo-oxo sites. The results open the scope for the optimisation of synthetic routes to explore the potential of small pore topologies.

Journal Keywords: MDA; Mo/CHA; operando XAS/XRD

Subject Areas: Chemistry


Instruments: B18-Core EXAFS

Documents:
molecules-25-05048-v2.pdf