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published version features the final layout of the paper including the volume, issue and page numbers. Link to publication General rightsCopyright and moral rights for the publications made accessible in the public portal are retained by the authors and/or other copyright owners and it is a condition of accessing publications that users recognise and abide by the legal requirements associated with these rights.• Users may download and print one copy of any publication from the public portal for the purpose of private study or research. • You may not further distribute the material or use it for any profit-making activity or commercial gain • You may freely distribute the URL identifying the publication in the public portal.If the publication is distributed under the terms of Article 25fa of the Dutch Copyright Act, indicated by the "Taverne" license above, please follow below link for the End User

Non‐oxidative dehydroaromatization of methane (MDA) is a promising catalytic process for direct valorization of natural gas to liquid hydrocarbons. The application of this reaction in practical technology is hindered by a lack of understanding about the mechanism and nature of the active sites in benchmark zeolite‐based Mo/ZSM‐5 catalysts, which precludes the solution of problems such as rapid catalyst deactivation. By applying spectroscopy and microscopy, it is shown that the active centers in Mo/ZSM‐5 are partially reduced single‐atom Mo sites stabilized by the zeolite framework. By combining a pulse reaction technique with isotope labeling of methane, MDA is shown to be governed by a hydrocarbon pool mechanism in which benzene is derived from secondary reactions of confined polyaromatic carbon species with the initial products of methane activation.

No abstract

The hydrogenation of CO 2 to CH 3 OH is an important reaction for future renewable energy scenarios. Herein, we compare Cu/ZnO, Cu/CeO 2 , and Cu/ZnO–CeO 2 catalysts prepared by flame spray pyrolysis. The Cu loading and support composition were varied to understand the role of Cu–ZnO and Cu–CeO 2 interactions. CeO 2 addition improves Cu dispersion with respect to ZnO, owing to stronger Cu–CeO 2 interactions. The ternary Cu/ZnO–CeO 2 catalysts displayed a substantially higher CH 3 OH selectivity than binary Cu/CeO 2 and Cu/ZnO catalysts. The high CH 3 OH selectivity in comparison with a commercial Cu–ZnO catalyst is also confirmed for Cu/ZnO–CeO 2 catalyst prepared with high Cu loading (∼40 wt %). In situ IR spectroscopy was used to probe metal–support interactions in the reduced catalysts and to gain insight into CO 2 hydrogenation over the Cu–Zn–Ce oxide catalysts. The higher CH 3 OH selectivity can be explained by synergistic Cu–CeO 2 and Cu–ZnO interactions. Cu–ZnO interactions promote CO 2 hydrogenation to CH 3 OH by Zn-decorated Cu active sites. Cu–CeO 2 interactions inhibit the reverse water–gas shift reaction due to a high formate coverage of Cu and a high rate of hydrogenation of the CO intermediate to CH 3 OH. These insights emphasize the potential of fine-tuning metal–support interactions to develop improved Cu-based catalysts for CO 2 hydrogenation to CH 3 OH.

published version features the final layout of the paper including the volume, issue and page numbers. Link to publication General rightsCopyright and moral rights for the publications made accessible in the public portal are retained by the authors and/or other copyright owners and it is a condition of accessing publications that users recognise and abide by the legal requirements associated with these rights.• Users may download and print one copy of any publication from the public portal for the purpose of private study or research. • You may not further distribute the material or use it for any profit-making activity or commercial gain • You may freely distribute the URL identifying the publication in the public portal.If the publication is distributed under the terms of Article 25fa of the Dutch Copyright Act, indicated by the "Taverne" license above, please follow below link for the End User

Non-oxidative dehydroaromatization of methane (MDA) is apromising catalytic process for direct valorization of natural gas to liquid hydrocarbons.T he application of this reaction in practical technology is hindered by al acko f understanding about the mechanism and nature of the active sites in benchmark zeolite-based Mo/ZSM-5 catalysts,w hich precludes the solution of problems such as rapid catalyst deactivation. By applying spectroscopya nd microscopy, it is shown that the active centers in Mo/ZSM-5 are partially reduced single-atom Mo sites stabilized by the zeolite framework. By combining ap ulse reaction techniquew ith isotope labeling of methane,M DA is shown to be governed by ah ydrocarbon pool mechanism in whichb enzenei sd erived from secondary reactions of confined polyaromatic carbon species with the initial products of methane activation.The abundance of natural gas reserves calls for the development of an efficient conversion technology to upgrade its principal component, methane,i nto easily transportable chemicals.[1] Several catalytic technologies,w hich could replace the current indirect route involving an expensive synthesis gas generation step,a re being considered. Broadly, we can distinguish between oxidative and non-oxidative direct routes.[2] Among the non-oxidative approaches,c atalytic methane dehydroaromatization (MDA) is one of the most promising methods.A fter the initial reports on MDA almost three decades ago, [3] as ubstantial body of literature has appeared.[4] Thei ndustrial implementation of the MDA process is mainly hindered by rapid catalyst deactivation caused by the deposition of ac arbonaceous material that blocks the catalytically active sites. [5] Although there have been remarkable achievements in regeneration procedures, [6] developing astable MDAcatalyst is still required to arrive at acommercial process.Aprogress in this direction is seriously hampered by limited understanding of the active sites in the benchmark Mo/ZSM-5 catalyst and the mechanism of methane conversion to benzene and hydrogen. Despite considerable debate on the nature of the active phase,t here is ag rowing consensus that the active sites are confined as highly dispersed Mo species by the zeolite pores in working Mo/ZSM-5 catalysts and that Mo 2 Cn anoparticles on the external surface are inactive. [7] Concerning the reaction mechanism, most reports support ab ifunctional pathway in which methane is activated and coupled to ethylene over Mocarbide species,followed by ethylene aromatization over the zeolite Brønsted acid sites. [8] Important challenges in gaining insight into these aspects are the high reaction temperature at which the MDAreaction takes place and its transient nature,w hich involves rapid activation and deactivation stages when the fresh Mo/ZSM-5 catalyst is exposed to am ethane feed. These factors complicate operando spectroscopy and kinetic investigations.A valuable approach in this regard is to increase the temporal resolution by pulsing the reactant over the catalyst an...

Non‐oxidative dehydroaromatization of methane over Mo/ZSM‐5 zeolite catalysts is a promising reaction for the direct conversion of abundant natural gas into liquid aromatics. Rapid coking deactivation hinders the practical implementation of this technology. Herein, we show that catalyst productivity can be improved by nearly an order of magnitude by raising the reaction pressure to 15 bar. The beneficial effect of pressure was found for different Mo/ZSM‐5 catalysts and a wide range of reaction temperatures and space velocities. High‐pressure operando X‐ray absorption spectroscopy demonstrated that the structure of the active Mo‐phase was not affected by operation at elevated pressure. Isotope labeling experiments, supported by mass‐spectrometry and 13 C nuclear magnetic resonance spectroscopy, indicated the reversible nature of coke formation. The improved performance can be attributed to faster coke hydrogenation at increased pressure, overall resulting in a lower coke selectivity and better utilization of the zeolite micropore space.