Methanol conversion to hydrocarbons via acidic catalysts

Liu, B

Abstract:: Methanol has long been advanced as a high-energy-density, widely-obtained (from non-oil sources such as coal, and biomass) material with potential as a replacement for the limitedly-distributed, finite-in-current-storage oil resources.

Given the fact that effective methanol conversion has been observed over the acidic, zeolite based catalytic materials, e.g. H-ZSM-5, since the 1970s, it is almost certain that extra catalytic properties, such as an enhanced C-H bond activation, gover...
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APA Style

Liu, B. (2016). Methanol conversion to hydrocarbons via acidic catalysts [PhD thesis]. University of Oxford.

MLA Style

Liu, B. Methanol Conversion to Hydrocarbons via Acidic Catalysts. University of Oxford, 2016.

Chicago Style

Liu, B. 2016. “Methanol Conversion to Hydrocarbons via Acidic Catalysts.” PhD thesis, University of Oxford.
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Files:: Thesis Bonan Liu Dphil 2016 Inorganic Chemistry Laboratory.pdf

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+ Liu, B More by this author

Institution:: University of Oxford
Oxford college:: Wolfson College
Role:: Author

Contributors

+ Edwards, P

Department:: Inorganic Chemistry
Role:: Supervisor

DOI:: 10.5287/ora-koyx5yorb
Type of award:: DPhil
Level of award:: Doctoral
Awarding institution:: University of Oxford

UUID:: uuid:2314ba14-8367-4334-8f53-2ec1c05f0e16
Deposit date:: 2016-10-27

Related item:: Methanol-to-hydrocarbons conversion over MoO3/H-ZSM-5 catalysts prepared via lower temperature calcination: a route to tailor the distribution and evolution of promoter Mo species, and their corresponding catalytic properties
Description:: A series of MoO3/H-ZSM-5 (Si/Al = 25) catalysts were prepared via calcination at a lower-than-usual temperature (400 °C) and subsequently evaluated in the methanol-to-hydrocarbon reaction at that same temperature. The catalytic properties of those catalysts were compared with the sample prepared at the more conventional, higher temperature of 500 °C. For the lower temperature preparations, molybdenum oxide was preferentially dispersed over the zeolite external surface, while only the higher loading level of MoO3 (7.5 wt% or higher) led to observable inner migration of the Mo species into the zeolite channels, with concomitant partial loss of the zeolite Brønsted acidity. On the MoO3 modified samples, the early-period gas yield, especially for valuable propylene and C4 products, was noticeably accelerated, and is gradually converted into an enhanced liquid aromatic formation. The 7.5 wt% MoO3/H-ZSM-5 sample prepared at 400 °C thereby achieved a balance between the zeolite surface dispersion of Mo species, their inner channel migration and the corresponding effect on the intrinsic Brønsted acidity of the acidic zeolite. That loading level also possessed the highest product selectivity (after 5 h reaction) to benzene, toluene and xylenes, as well as higher early-time valuable gas product yields in time-on-stream experiments. However, MoO3 loading levels of 7.5 wt% and above also resulted in earlier catalyst deactivation by enhanced coke accumulation at, or near, the zeolite channel openings. Our research illustrates that the careful adoption of moderate/lower temperature dispersion processes for zeolite catalyst modification gives considerable potential for tailoring and optimizing the system's catalytic performance.
Related item:: Advances in the study of coke formation over zeolite catalysts in the methanol-to-hydrocarbon process
Description:: Methanol-to-hydrocarbon (MTH) process over acidic zeolite catalysts has been widely utilised to yield many types of hydrocarbons, some of which are eventually converted into the highly dehydrogenated (graphitized) carbonaceous species (cokes). The coking process can be divided into two parallel pathways based on the accepted hydrocarbon pool theory. From extensive investigations, it is reasonable to conclude that inner zeollite cavity/channel reactions at acidic sites generate cokes. However, coke formation and accumulation over the zeolite external surfaces play a major role in reaction deactivation as they contribute a great portion to the total coke amount. Herein we have reviewed previous literatures and included some recent works from KOPRC in understanding the nature and mechanism of coke formation, particularly during an H-ZSM-5 catalysed MTH reaction. We specially conclude that rapid aromatics formation at the zeolite crystalite edges is the main reason for later stage coke accumulation on the zeolite external surfaces. Accordingly, the catalyst deactivation is in a great certain to arise at those edge areas due to having the earliest contact with the incoming methanol reactant. The final coke structure is therefore built up with layers of poly-aromatics, as the potential sp2 carbons leading to pre-graphite structure. We have proposed a coke formation model particularly for the acidic catalyst, which we believe will be of assistance in understanding—and hence minimising—the coke formation mechanisms.

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Copyright holder:: Liu, B

Licence:: Terms and Conditions of Use for Oxford University Research Archive

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Methanol conversion to hydrocarbons via acidic catalysts

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