A site-sensitive quasi-in situ strategy to characterize Mo/HZSM-5 during activation (2024)

Vollmer, I., Kosinov, N., Szécsényi, Á., Li, G., Yarulina, I., Abou-Hamad, E., Gurinov, A., Ould-Chikh, S., Aguilar-Tapia, A., Hazemann, J. L., Pidko, E., Hensen, E., Kapteijn, F., & Gascon, J. (2019). A site-sensitive quasi-in situ strategy to characterize Mo/HZSM-5 during activation. Journal of Catalysis, 370, 321-331. https://doi.org/10.1016/j.jcat.2019.01.013

Vollmer, Ina ; Kosinov, Nikolay ; Szécsényi, Ágnes et al. / A site-sensitive quasi-in situ strategy to characterize Mo/HZSM-5 during activation. In: Journal of Catalysis. 2019 ; Vol. 370. pp. 321-331.

@article{5e92a33b1d434643b798c0ee5ee798d1,

title = "A site-sensitive quasi-in situ strategy to characterize Mo/HZSM-5 during activation",

abstract = "The active sites on the methane dehydroaromatization (MDA) catalyst Mo/HZSM-5 are very hard to characterize, because they are present in various geometries and sizes and only form under reaction conditions with methane at 700 °C. To address these issues an experimental strategy is presented that enables distinguishing different active sites for MDA present on Mo/HZSM-5 and helps determining the Mo charge, nuclearity and chemical composition. This approach combines a CO pretreatment to separate the active Mo site formation from co*ke formation, quasi-in situ spectroscopic observations using DNP, 13C NMR, CO IR and theory. This allows the discrimination between three different types of active sites. Distinct spectroscopic features were observed corresponding to two types of mono- or dimeric Mo (oxy-)carbide sites as well as a third site assigned to Mo2C nanoparticles on the outer surface of the zeolite. Their formal Mo oxidation state was found to be between 4+ and 6+. Dynamic nuclear polarization (DNP) measurements of samples carburized in CO as well as in CH4 confirm the assignment and also show that accumulated aromatic carbon covers the bigger Mo nanoparticles on the outer surface of the zeolite, causing deactivation. It was previously observed that after an initial period where no desired products are formed yet, benzene starts slowly forming until reaching its maximum productivity. Direct observation of the active site with 13C NMR confirmed that Mo-sites do not transform further once benzene starts forming, meaning that they are fully activated during the period where no desired products are observed yet. Therefore the slow increase of the benzene formation rate cannot be attributed to a further transformation of Mo sites.",

keywords = "C NMR, CO IR, Dimeric species, DNP SENS, Methane dehydroaromatization, Mo (oxy-)carbide, Mo/HZSM-5, MoC, Monomeric species, Well-defined species",

author = "Ina Vollmer and Nikolay Kosinov and {\'A}gnes Sz{\'e}cs{\'e}nyi and Guanna Li and Irina Yarulina and Edy Abou-Hamad and Andrei Gurinov and Samy Ould-Chikh and Antonio Aguilar-Tapia and Hazemann, {Jean Louis} and Evgeny Pidko and Emiel Hensen and Freek Kapteijn and Jorge Gascon",

year = "2019",

month = feb,

day = "1",

doi = "10.1016/j.jcat.2019.01.013",

language = "English",

volume = "370",

pages = "321--331",

journal = "Journal of Catalysis",

issn = "0021-9517",

publisher = "Academic Press Inc.",

}

Vollmer, I, Kosinov, N, Szécsényi, Á, Li, G, Yarulina, I, Abou-Hamad, E, Gurinov, A, Ould-Chikh, S, Aguilar-Tapia, A, Hazemann, JL, Pidko, E, Hensen, E, Kapteijn, F & Gascon, J 2019, 'A site-sensitive quasi-in situ strategy to characterize Mo/HZSM-5 during activation', Journal of Catalysis, vol. 370, pp. 321-331. https://doi.org/10.1016/j.jcat.2019.01.013

A site-sensitive quasi-in situ strategy to characterize Mo/HZSM-5 during activation. / Vollmer, Ina; Kosinov, Nikolay; Szécsényi, Ágnes et al.
In: Journal of Catalysis, Vol. 370, 01.02.2019, p. 321-331.

Research output: Contribution to journal › Article › Academic › peer-review

TY - JOUR

T1 - A site-sensitive quasi-in situ strategy to characterize Mo/HZSM-5 during activation

AU - Vollmer, Ina

AU - Kosinov, Nikolay

AU - Szécsényi, Ágnes

AU - Li, Guanna

AU - Yarulina, Irina

AU - Abou-Hamad, Edy

AU - Gurinov, Andrei

AU - Ould-Chikh, Samy

AU - Aguilar-Tapia, Antonio

AU - Hazemann, Jean Louis

AU - Pidko, Evgeny

AU - Hensen, Emiel

AU - Kapteijn, Freek

AU - Gascon, Jorge

PY - 2019/2/1

Y1 - 2019/2/1

N2 - The active sites on the methane dehydroaromatization (MDA) catalyst Mo/HZSM-5 are very hard to characterize, because they are present in various geometries and sizes and only form under reaction conditions with methane at 700 °C. To address these issues an experimental strategy is presented that enables distinguishing different active sites for MDA present on Mo/HZSM-5 and helps determining the Mo charge, nuclearity and chemical composition. This approach combines a CO pretreatment to separate the active Mo site formation from co*ke formation, quasi-in situ spectroscopic observations using DNP, 13C NMR, CO IR and theory. This allows the discrimination between three different types of active sites. Distinct spectroscopic features were observed corresponding to two types of mono- or dimeric Mo (oxy-)carbide sites as well as a third site assigned to Mo2C nanoparticles on the outer surface of the zeolite. Their formal Mo oxidation state was found to be between 4+ and 6+. Dynamic nuclear polarization (DNP) measurements of samples carburized in CO as well as in CH4 confirm the assignment and also show that accumulated aromatic carbon covers the bigger Mo nanoparticles on the outer surface of the zeolite, causing deactivation. It was previously observed that after an initial period where no desired products are formed yet, benzene starts slowly forming until reaching its maximum productivity. Direct observation of the active site with 13C NMR confirmed that Mo-sites do not transform further once benzene starts forming, meaning that they are fully activated during the period where no desired products are observed yet. Therefore the slow increase of the benzene formation rate cannot be attributed to a further transformation of Mo sites.

AB - The active sites on the methane dehydroaromatization (MDA) catalyst Mo/HZSM-5 are very hard to characterize, because they are present in various geometries and sizes and only form under reaction conditions with methane at 700 °C. To address these issues an experimental strategy is presented that enables distinguishing different active sites for MDA present on Mo/HZSM-5 and helps determining the Mo charge, nuclearity and chemical composition. This approach combines a CO pretreatment to separate the active Mo site formation from co*ke formation, quasi-in situ spectroscopic observations using DNP, 13C NMR, CO IR and theory. This allows the discrimination between three different types of active sites. Distinct spectroscopic features were observed corresponding to two types of mono- or dimeric Mo (oxy-)carbide sites as well as a third site assigned to Mo2C nanoparticles on the outer surface of the zeolite. Their formal Mo oxidation state was found to be between 4+ and 6+. Dynamic nuclear polarization (DNP) measurements of samples carburized in CO as well as in CH4 confirm the assignment and also show that accumulated aromatic carbon covers the bigger Mo nanoparticles on the outer surface of the zeolite, causing deactivation. It was previously observed that after an initial period where no desired products are formed yet, benzene starts slowly forming until reaching its maximum productivity. Direct observation of the active site with 13C NMR confirmed that Mo-sites do not transform further once benzene starts forming, meaning that they are fully activated during the period where no desired products are observed yet. Therefore the slow increase of the benzene formation rate cannot be attributed to a further transformation of Mo sites.

KW - C NMR

KW - CO IR

KW - Dimeric species

KW - DNP SENS

KW - Methane dehydroaromatization

KW - Mo (oxy-)carbide

KW - Mo/HZSM-5

KW - MoC

KW - Monomeric species

KW - Well-defined species

UR - http://www.scopus.com/inward/record.url?scp=85060229656&partnerID=8YFLogxK

U2 - 10.1016/j.jcat.2019.01.013

DO - 10.1016/j.jcat.2019.01.013

M3 - Article

AN - SCOPUS:85060229656

SN - 0021-9517

VL - 370

SP - 321

EP - 331

JO - Journal of Catalysis

JF - Journal of Catalysis

ER -

Vollmer I, Kosinov N, Szécsényi Á, Li G, Yarulina I, Abou-Hamad E et al. A site-sensitive quasi-in situ strategy to characterize Mo/HZSM-5 during activation. Journal of Catalysis. 2019 Feb 1;370:321-331. doi: 10.1016/j.jcat.2019.01.013