Supercritical solvothermal synthesis under reducing conditions to increase stability and durability of Mo/ZSM-5 catalysts in methane dehydroaromatization

Julián, Ignacio; Roedern, Morten B.; Hueso, José L.; Irusta, Silvia; Baden, Ane K.; Mallada, Reyes; Davis, Zachary; Santamarı́a, Jesús

doi:10.1016/j.apcatb.2019.118360

Cited by 48 publications

(52 citation statements)

References 57 publications

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“…Our best methane conversion results are among the highest reported ones after 5 h on stream. However, slightly lower overall yield to C 2+ products are obtained with respect to those reported by e.g., Julian et al [28] and Liu et al [40]. Specifically, the Mo/ZSM-5 catalyst prepared by Julián et al [28] under supercritical solvothermal synthesis under reduced conditions provided the best long-term aromatics yield among all results in literature (9.0% also after 15 h on stream).…”

Section: Reference X Ch4 (5h) (%) Y C2+ (5h) (%)mentioning

confidence: 61%

“…As previously discussed, the coke detected during the first minutes of reaction is attributed to the presence of Mo 2 C formed during the induction period as a result of the reduction of molybdenum oxide species. The coke selectivity increase after two hours on stream can be related with the parallel formation pre-graphitic coke from polyaromatic hydrocarbons (hard coke), apart from the graphitic coke formed at the oxycarbide active sites (soft coke) [28]. In this regard, the nature and extent of coke deposits after 6 h on stream were evaluated by Raman spectroscopy and thermogravimetric analysis for the four catalytic samples.…”

Section: Influence Of Ultrasonic Irradiation On the Catalytic Activitymentioning

confidence: 99%

“…Julian et al [28] 12.7 9.0 Han et al [7] 8.1 7.5 Tan [37] 10.5 8.4 Martinez and Penis [38] 8.2 6.0 Liu et al [39] 11.2 6.9 Song et al [26] 11.7 8.7 Liu et al [40] 13. Our best methane conversion results are among the highest reported ones after 5 h on stream.…”

Section: Reference X Ch4 (5h) (%) Y C2+ (5h) (%)mentioning

confidence: 99%

“…They demonstrated an enhanced metal dispersion on the aluminosilicate support at lower loading and more active and selective catalysts prepared with POM, which was key to partially suppress catalyst coking and improve stability. Furthermore, the same research group proposed a novel synthesis method for the same catalyst based on a solvothermal incorporation of molybdenum into the zeolite under supercritical conditions and reducing atmosphere [28]. The preparation method provided atom-like metal dispersion at the zeolite pores, resulting in a Mo/ZSM-5 catalyst with outstanding stability and the highest long-term hydrocarbon yield for MDA (8.9% after 15 h on stream).…”

Section: Introductionmentioning

confidence: 99%

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Ultrasound-Assisted Preparation of Mo/ZSM-5 Zeolite Catalyst for Non-Oxidative Methane Dehydroaromatization

et al. 2021

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The activity and selectivity of Mo/ZSM-5, benchmarking catalyst for the non-oxidative dehydroaromatization of methane, strongly depend on the cluster size, spatial distribution, and chemical environment of the Mo-based active sites. This study discloses the use of an ultrasound-assisted ion-exchange (US-IE) technique as an alternative Mo/ZSM-5 synthesis procedure in order to promote metal dispersion along the zeolite framework. For this purpose, a plate transducer (91.8 kHz) is employed to transmit the ultrasonic irradiation (US) into the ion-exchange reactor. The physico-chemical properties and catalytic activity of samples prepared under the said irradiation procedure and traditional impregnation (IWI) method are critically evaluated. Characterization results suggest that US neither affects the crystalline structure nor the particle size of the parent zeolite. However, US-IE promotes molybdenum species dispersion, avoids clustering at the external fresh zeolite surface and enhances molybdate species anchoring to the zeolite framework with respect to IWI. Despite the improved metal dispersion, the catalytic activity between catalysts synthesized by US-IE and IWI is comparable. This suggests that the sole initial dispersion enhancement does not suffice to boost the catalyst productivity and further actions such ZSM-5 support and catalyst pre-conditioning are required. Nevertheless, the successful implementation of US-IE and the resulting metal dispersion enhancement pave the way toward the application of this technique to the synthesis of other dispersed catalysts and materials of interest.

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Section: Reference X Ch4 (5h) (%) Y C2+ (5h) (%)mentioning

confidence: 61%

Section: Influence Of Ultrasonic Irradiation On the Catalytic Activitymentioning

confidence: 99%

Section: Reference X Ch4 (5h) (%) Y C2+ (5h) (%)mentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

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Ultrasound-Assisted Preparation of Mo/ZSM-5 Zeolite Catalyst for Non-Oxidative Methane Dehydroaromatization

et al. 2021

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“…Secondly, if the catalyst coking proceeds via formation of carbon nanotubes or graphitized species, as a result of an initial low metal dispersion and presence of MoO3 agglomerates at the external surface of the zeolite [25], the carbonaceous materials would absorb MW-radiation preferentially with respect to SiC supports due to their comparatively higher loss factor (ε''). This last scenario may result in the transient shift of the resonant frequency of the cavity and in a potentially Regarding the effect of the metal loading, we previously observed that the higher the Mo content in the sample, the greater its MW-absorption capacity is [25,26]. The loss factor of all fresh Mo/ZSM-5 samples is very low and similar at temperatures under 300 • C, which is related to dehydration.…”

Section: Dielectric Properties Of Selected Materialsmentioning

confidence: 95%

Overcoming Stability Problems in Microwave-Assisted Heterogeneous Catalytic Processes Affected by Catalyst Coking

et al. 2019

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Microwave-assisted heterogeneous catalysis (MHC) is gaining attention due to its exciting prospects related to selective catalyst heating, enhanced energy-efficiency, and partial inhibition of detrimental side gas-phase reactions. The induced temperature difference between the catalyst and the comparatively colder surrounding reactive atmosphere is pointed as the main factor of the process selectivity enhancement towards the products of interest in a number of hydrocarbon conversion processes. However, MHC is traditionally restricted to catalytic reactions in the absence of catalyst coking. As excellent MW-susceptors, carbon deposits represent an enormous drawback of the MHC technology, being main responsible of long-term process malfunctions. This work addresses the potentials and limitations of MHC for such processes affected by coking (MHCC). It also intends to evaluate the use of different catalyst and reactor configurations to overcome heating stability problems derived from the undesired coke deposits. The concept of long-term MHCC operation has been experimentally tested/applied to for the methane non-oxidative coupling reaction at 700 °C on Mo/ZSM-5@SiC structured catalysts. Preliminary process scalability tests suggest that a 6-fold power input increases the processing of methane flow by 150 times under the same controlled temperature and spatial velocity conditions. This finding paves the way for the implementation of high-capacity MHCC processes at up-scaled facilities.

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Tan

Yang

et al. 2023

Industrial Arene Chemistry

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Supercritical solvothermal synthesis under reducing conditions to increase stability and durability of Mo/ZSM-5 catalysts in methane dehydroaromatization

Cited by 48 publications

References 57 publications

Ultrasound-Assisted Preparation of Mo/ZSM-5 Zeolite Catalyst for Non-Oxidative Methane Dehydroaromatization

Ultrasound-Assisted Preparation of Mo/ZSM-5 Zeolite Catalyst for Non-Oxidative Methane Dehydroaromatization

Overcoming Stability Problems in Microwave-Assisted Heterogeneous Catalytic Processes Affected by Catalyst Coking

BTX from Light Hydrocarbons

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