Zeolites catalyzed methanol-to-olefins （MTO） conversion provides an alternative process to produce light olefins such as ethene and propene from nonpetroleum resources. Despite of successful industrialization of the...Zeolites catalyzed methanol-to-olefins （MTO） conversion provides an alternative process to produce light olefins such as ethene and propene from nonpetroleum resources. Despite of successful industrialization of the MTO process, its detailed reaction mechanism is not yet well understood. Here we summarize our work on the hydrocarbon pool reaction mechanism based on theoretical calculations. We proposed that the olefins themselves are likely to be the dominating hydrocarbon pool species, and the distribution of cracking precursors and diffusion constraints affect the selectivity. The similarities between aromatic-based and olefin-based cycles are highlighted.展开更多
Small pore zeolites, containing 8-rings as the largest, are widely employed as catalysts in the process of methanol-to-olefins （MTO）. Reactants and products dif- fuse with constraints through 8-rings and this is one...Small pore zeolites, containing 8-rings as the largest, are widely employed as catalysts in the process of methanol-to-olefins （MTO）. Reactants and products dif- fuse with constraints through 8-rings and this is one of the reaction bottlenecks related to zeolite micropore topology. Small pore zeolites and silicon-aluminophosphates （SAPOs） containing cavities, where olefins are mainly formed through the hydrocarbon pool （HP） mechanism, are frequently tested for MTO. Shape selectivity of transition states within the side-chain methylation will be reviewed as this is one of the controlling steps of the MTO process, with particular attention to the role of hexam- ethylbenzene （HMB） and heptamethylbenzenium cation （HeptaMB~）, which are the most tipically detected reaction intermediates, common to the paring and side-chain routes within the HP mechanism. The relative stability of these and other species will be reviewed in terms of confinement effects in different cage-based zeolites. The role of the different alkylating agents, methanol, dimethyl ether （DME）, and surface methoxy species （SMS） will also be reviewed from the computational viewpoint.展开更多
文摘Zeolites catalyzed methanol-to-olefins （MTO） conversion provides an alternative process to produce light olefins such as ethene and propene from nonpetroleum resources. Despite of successful industrialization of the MTO process, its detailed reaction mechanism is not yet well understood. Here we summarize our work on the hydrocarbon pool reaction mechanism based on theoretical calculations. We proposed that the olefins themselves are likely to be the dominating hydrocarbon pool species, and the distribution of cracking precursors and diffusion constraints affect the selectivity. The similarities between aromatic-based and olefin-based cycles are highlighted.
文摘Small pore zeolites, containing 8-rings as the largest, are widely employed as catalysts in the process of methanol-to-olefins （MTO）. Reactants and products dif- fuse with constraints through 8-rings and this is one of the reaction bottlenecks related to zeolite micropore topology. Small pore zeolites and silicon-aluminophosphates （SAPOs） containing cavities, where olefins are mainly formed through the hydrocarbon pool （HP） mechanism, are frequently tested for MTO. Shape selectivity of transition states within the side-chain methylation will be reviewed as this is one of the controlling steps of the MTO process, with particular attention to the role of hexam- ethylbenzene （HMB） and heptamethylbenzenium cation （HeptaMB~）, which are the most tipically detected reaction intermediates, common to the paring and side-chain routes within the HP mechanism. The relative stability of these and other species will be reviewed in terms of confinement effects in different cage-based zeolites. The role of the different alkylating agents, methanol, dimethyl ether （DME）, and surface methoxy species （SMS） will also be reviewed from the computational viewpoint.
