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Recently, researcher Gao Peng of the Shanghai Advanced Research Institute of the Chinese Academy of Sciences has made important breakthroughs
in the research of efficient aromatics production under synthetic temperature and conditions.
The research team developed a high-performance bifunctional catalyst with industrial application potential, and proposed a new reaction path
for the hydrogenation of syngas to generate aromatics.
At present, among the existing two reaction paths of syngas to aromatics, the reaction conditions of the coupled catalytic system are harsh (320 °C ~ 430 °C), and the activity, selectivity and stability of the catalyst are difficult to match
.
The research team constructed a scale-wrapped nano-hollow ZSM-5 molecular sieve and a bifunctional catalyst CMA/ZSM-5 coupled with cobalt-manganese-aluminum (CMA) oxide, and proposed a new reaction path
for the hydrogenation of syngas to generate aromatics.
Hydrogenation of carbon monoxide on the surface of prismatic cobalt carbide can generate C2~C4 olefins,C5+ olefins andC2+ oxygen-containing compounds
.
C2~C4 olefins enter the molecular sieve pores by diffusion, and oligomerization reactions occur to generate long-chain olefins, and then through cyclization and aromatization reactions to generate aromatics
.
In addition to direct aromatization reaction,C5+ olefins can also react with carbon monoxide on ZSM-5 to form 2,4-dimethylbenzaldehyde; Carbon monoxide andC2+ oxygenated compounds can also be converted to p-toluene-formaldehyde
by alkyd cyclization on ZSM-5.
These oxygenated compounds undergo dehydration and hydrogenation reactions on molecular sieves to form aromatic hydrocarbons, of which p-toluene-formaldehyde plays a crucial role
in the hydrogenation of carbon monoxide to paraxylene.
In this study, the bifunctional catalyst demonstrated high conversion of carbon monoxide, high aromatic selectivity and high stability under mild reaction conditions, and obtained an unprecedented temporal and spatial yield of
paraxylene.
By growing a scaly zeolite with the same topology on the surface of the nanohollow ZSM-5, the team effectively passivated the acidity of the outer surface without affecting mass transfer, and promoted the selective formation
of paraxylene.
The experimental results showed that under the reaction conditions of 280 °C and catalyst dosage of 1000 ml/g per hour, the conversion rate of carbon monoxide reached 70.
7%, the selectivity of aromatics in hydrocarbon products was greater than 63.
5%, and the proportion of paraxylene in aromatics was as high as 34.
7%, which was better than the previously reported catalytic system
.
In addition, the activity and selectivity of the catalyst can be maintained for more than 700 hours without attenuation, showing excellent industrial application potential
.
