Abstract
Efficient use of natural gas to produce aromatics is an attractive subject; the process requires catalysts that possess high-performance active sites to activate stable C–H bonds. Here, we report a facile synthetic strategy to modify HMCM-49 with small molybdenum oxide nanoparticles. Due to the higher sublimability of nano-MoO3 particles than commercial MoO3, they more easily enter into the channels of HMCM-49 and associate with Brønsted acid sites to form active MoCx-type species under calcination and reaction conditions. Compared with commercial MoO3 modified MCM-49, nano-MoO3 modified MCM-49 exhibits higher methane conversion (13.2%), higher aromatics yield (9.1%), and better stability for the methane aromatization reaction.
Highlights
The ongoing discovery of cheap natural gas has stimulated increased interest in converting the main component, methane, to higher value-added fuels and chemicals [1]
It has been reported that non-modified HZSM-5 and Mo/NaZSM-5 catalysts exhibit poor methane dehydro-aromatization (MDA) activity due to a lack of active or acidic sites [5,36,37]
The Mo-oxo species was carburized to MoCx after introducing CH4, and methane conversion and aromatics yield reached quasi-steady values [13,39]
Summary
The ongoing discovery of cheap natural gas has stimulated increased interest in converting the main component, methane, to higher value-added fuels and chemicals [1]. Seeking catalysts with high catalytic activity and stability for this reaction remains a significant challenge. Mo-based MDA catalysts are usually prepared by mechanical mixing, leading to the dispersion of Mo(VI)-oxo species on the outside surface of the zeolite and inside the microporous channel of the zeolite through high-temperature treatment. The dispersion of active centers in different pore systems of MWW zeolites, which are solid acidic catalysts, depends on the accessibility of the acid sites, diffusion lengths, and reaction spaces for the transition state, which will affect the catalytic performance of MDA [22]. A single-site Mo-containing nanosized ZSM-5 zeolite with homogenous dispersion of Mo atoms shows superior catalytic activity and stability [28]. We found that nano-MoO3-doped HMCM-49 showed higher methane conversion, higher benzene yield, and better stability than commercial MoO3-modified HMCM-49
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