New insights into hierarchical metal-containing zeolites; synthesis and kinetic modelling of mesoporous gallium-containing ZSM-5 for propane aromatization

Ogunronbi, Kehinde E.; Al-Yassir, N.; Al-Khattaf, S.

doi:10.1016/j.molcata.2015.05.005

Cited by 35 publications

(29 citation statements)

References 46 publications

(71 reference statements)

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“…Gallium oxide particles or clusters, located in the channels and/or external surface of the zeolite were usually produced by ion exchange or incipient wetness impregnation [ 50 , 103 , 104 , 105 , 106 ]. The potential existence of octahedral coordinated Ga 3+ or highly dispersed Ga 2 O 3 can be identified by the chemical shift in the range from −7 to 24 ppm on 71 Ga MAS NMR, and the appearance of reductive peaks in H 2 -TPR from 670 to 1170 K [ 45 , 50 , 58 , 70 , 103 , 107 , 108 ].…”

Section: Reactive Species In Ga-modified Zsm-5mentioning

confidence: 99%

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Recent Advances on Gallium-Modified ZSM-5 for Conversion of Light Hydrocarbons

et al. 2021

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Light olefins are key components of modern chemical industry and are feedstocks for the production of many commodity chemicals widely used in our daily life. It would be of great economic significance to convert light alkanes, produced during the refining of crude oil or extracted during the processing of natural gas selectively to value-added products, such as light alkenes, aromatic hydrocarbons, etc., through catalytic dehydrogenation. Among various catalysts developed, Ga-modified ZSM-5-based catalysts exhibit superior catalytic performance and stability in dehydrogenation of light alkanes. In this mini review, we summarize the progress on synthesis and application of Ga-modified ZSM-5 as catalysts in dehydrogenation of light alkanes to olefins, and the dehydroaromatization to aromatics in the past two decades, as well as the discussions on in-situ formation and evolution of reactive Ga species as catalytic centers and the reaction mechanisms.

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Section: Reactive Species In Ga-modified Zsm-5mentioning

confidence: 99%

“…However, the reaction kinetics and thermogravimetric (TG) analysis show that the catalytic performance of Ga-modified ZSM-5 is superior over Ga 2 O 3 clusters [ 46 , 108 ]. The increase of Ga loading may lead to decrease of BAS and enhanced dehydrogenation activity of Ga-modified ZSM-5.…”

Section: Reactive Species In Ga-modified Zsm-5mentioning

confidence: 99%

Recent Advances on Gallium-Modified ZSM-5 for Conversion of Light Hydrocarbons

et al. 2021

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“…Moreover, the average electronegativity value of 1.59 for Ga is lower than the value for Al (1.714), implying a lower acid strength of Brønsted protons for Ga‐substituted zeolites. Previous studies have indicated that gallium‐containing zeolites can effectively decrease the production of lower C1–C5 hydrocarbons and polyaromatic products in many petrochemical processes . This decrease occurs mainly because gallium species deposited on zeolites significantly improve the hydrogenation activity of zeolites and lower the acid strength of the modified zeolites to avoid the over‐cracking of the hydrogenated hydrocarbons.…”

Section: Introductionmentioning

confidence: 99%

“…Previous studies have indicated that gallium-containing zeolitesc an effectively decrease the production of lower C1-C5 hydrocarbonsa nd polyaromatic products in many petrochemical processes. [32,33] This decrease occurs mainly because gallium species deposited on zeolites significantly improve the hydrogenation activity of zeolites and lower the acid strength of the modified zeolites to avoid the over-cracking of the hydrogenated hydrocarbons. Since the mechanistic studies of alkanes aromatizing into aromatics indicates that gallium species deposited on zeolites have as ignificant effect on the adsorption and activation of alkanest op roduce activated C + intermediates, we also hypothesized that gallium-modified zeolites might exhibit extraordinary activity for the isomerization of hydrocarbonsc ompared to conventional ones.…”

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confidence: 99%

Gallium Modified HUSY Zeolite as an Effective Co‐support for NiMo Hydrodesulfurization Catalyst and the Catalyst's High Isomerization Selectivity

Zhou

Wei

et al. 2017

Chemistry A European J

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The effects of metal-modified acidic co-supports on the hydrodesulfurization (HDS) activity and isomerization selectivity of highly refractory organosulfur compounds such as 4,6-dimethyldibenzothiophene have been investigated. Y zeolite crystals with high Si/Al ratios and small crystallite sizes were successfully synthesized by a new hydrothermal synthesis approach. The synthesized Y zeolite crystals were ion-exchanged and stabilized. The prepared samples were then modified with different gallium contents using an impregnation method to adjust their acidity properties, and these modified samples were used as co-supports for NiMo sulfide HDS catalysts. The catalyst containing 10 wt.% zeolite Y modified by 2 wt.% gallium (NiMo/2GaY-ASA-A) exhibited the highest HDS activity, with 4,6-dimethyldibenzothiophene (4,6-DMDBT) conversion nearly double the rate of the catalyst without zeolite at 563 K, 4.0 MPa and liquid hourly space velocity (LHSV) of 40 h . NiMo/2GaY-ASA-A also exhibited superior isomerization ability, with 3,4'-DMBP, 4,4'DMBP, and 3,6-DMDBT as the main products, indicating that the isomerization pathway was the main reaction route over NiMo/2GaY-ASA-A. The superior catalytic performance is related to the synergistic effect of the proper amount of medium and strong Brønsted acid sites. The compounds 3,6-DMDBT and 3,7-DMDBT (isomers of 4,6-DMDBT) and 3,4,6-TMDBT and tetra-methyl-DBT (transmethyl products) were detected simultaneously in the HDS product of 4,6-DMDBT for the first time over NiMo/GaY-ASA-A catalysts. Finally, a new reaction network over NiMo/2GaY-ASA-A was proposed.

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“…22 However, the method usually causes the change of surface acidity or partial crystallinity loss of the zeolite. The soft-template method (e.g., organosilanes, 23 surfactants, 24 and polymers 25 ) is a relatively facile way, but it usually causes phase separation. Also, the synthetic cost and use of toxic organic template further hinder the practical industrial application.…”

Section: ■ Introductionmentioning

confidence: 99%

Hydrogenation of CO₂ to Dimethyl Ether over Tandem Catalysts Based on Biotemplated Hierarchical ZSM-5 and Pd/ZnO

Wang

Zhan

et al. 2020

ACS Sustainable Chem. Eng.

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The chemical transformation of CO 2 to valueadded chemicals and fuels remains a daunting research challenge, requiring the development of more efficient catalysts. The present work offers highly active integrated nanocatalysts for CO 2 hydrogenation to dimethyl ether (DME) through tandem catalysis, that is, Pd/ZnO converts CO 2 to methanol, and bio-ZSM-5 further catalyzes methanol dehydration to DME. Notably, the hierarchically porous bio-ZSM-5 with high pore connectivity was prepared by using low-cost rice husk and luffa sponge as biotemplates. The formation of bio-ZSM-5 involved three consecutive steps, including (i) diffusion of precursor species, (ii) confined crystal growth, and (iii) calcination treatment to remove the residual biomass. Interestingly, the obtained bio-ZSM-5 possesses abundant hierarchical porosity, including the intrinsic micropores from ZSM-5 frameworks, the mesopores from intracrystalline void space or pinholes in the intergrown zeolite layers, and the macroscopic channels from the original biomass architecture. It was found that the tetrapropylammonium hydroxide amount and Si/Al ratio were two critical factors affecting the crystallinity and porosity of the bio-ZSM-5. The silicon content in biomass (8.3 wt % in rice husk and 0.016 wt % in luffa sponge) also played a crucial role in the synthesis of bio-ZSM-5. Different spatial configurations of Pd/ZnO and bio-ZSM-5 significantly affected the DME yield, wherein spatial distances between the bio-ZSM-5 and Pd/ZnO components were adjusted by controlling the size of Pd/ZnO or the integration manners. The current results indicated that the closest proximity of the bifunctional catalyst was unfavorable for DME production (selectivity < 3%), because of which low-valent Zn cations from Pd/ZnO could displace the Brønsted acid sites on bio-ZSM-5 by ion exchange, and the powder mixing in the mortar was the best combination configuration of Pd/ZnO and bio-ZSM-5, promoting the CO 2 conversion (10.8%) with a DME selectivity of 31% under the reaction of 300 °C and 30 bar. Furthermore, as compared to the traditional ZSM-5 based catalyst, the obtained Pd/ZnO/bio-ZSM-5 bifunctional catalysts showed excellent longterm stability in 60 h on stream with a less amount of coke formed in the spent catalysts.

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New insights into hierarchical metal-containing zeolites; synthesis and kinetic modelling of mesoporous gallium-containing ZSM-5 for propane aromatization

Cited by 35 publications

References 46 publications

Recent Advances on Gallium-Modified ZSM-5 for Conversion of Light Hydrocarbons

Recent Advances on Gallium-Modified ZSM-5 for Conversion of Light Hydrocarbons

Gallium Modified HUSY Zeolite as an Effective Co‐support for NiMo Hydrodesulfurization Catalyst and the Catalyst's High Isomerization Selectivity

Hydrogenation of CO₂ to Dimethyl Ether over Tandem Catalysts Based on Biotemplated Hierarchical ZSM-5 and Pd/ZnO

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New insights into hierarchical metal-containing zeolites; synthesis and kinetic modelling of mesoporous gallium-containing ZSM-5 for propane aromatization

Cited by 35 publications

References 46 publications

Recent Advances on Gallium-Modified ZSM-5 for Conversion of Light Hydrocarbons

Recent Advances on Gallium-Modified ZSM-5 for Conversion of Light Hydrocarbons

Gallium Modified HUSY Zeolite as an Effective Co‐support for NiMo Hydrodesulfurization Catalyst and the Catalyst's High Isomerization Selectivity

Hydrogenation of CO2 to Dimethyl Ether over Tandem Catalysts Based on Biotemplated Hierarchical ZSM-5 and Pd/ZnO

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Hydrogenation of CO₂ to Dimethyl Ether over Tandem Catalysts Based on Biotemplated Hierarchical ZSM-5 and Pd/ZnO