Abstract
Light olefins including ethylene, propylene and butylene are important building blocks in petrochemical industries to produce various chemicals such as polyethylene, polypropylene, ethylene oxide and cumene. Traditionally, light olefins are produced via a steam cracking process operated at an extremely high temperature. The catalytic conversion, in which zeolites have been widely used, is an alternative pathway using a lower temperature. However, conventional zeolites, composed of a pure microporous structure, restrict the diffusion of large molecules into the framework, resulting in coke formation and further side reactions. To overcome these problems, hierarchical zeolites composed of additional mesoporous and/or macroporous structures have been widely researched over the past decade. In this review, the recent development of hierarchical zeolite nanosheets and nanoparticle assemblies together with opening up their applications in various light olefin productions such as catalytic cracking, ethanol dehydration to ethylene, methanol to olefins (MTO) and other reactions will be presented.
Highlights
Light olefins including ethylene, propylene and butylene are one of the most important chemical building blocks, which are widely used as precursors for many products in petrochemical industries such as polyethylene, polypropylene, acrylonitrile and propylene oxide
Ethylene and propylene are produced via various processes such as steam cracking, fluid catalytic cracking (FCC)
A high portion of light olefins has been produced via steam cracking, which requires severe conditions operated at a very high temperature (>850 ◦ C), eventually yielding a high amount of methane and carbon dioxide as by-products [2,3]
Summary
Propylene and butylene are one of the most important chemical building blocks, which are widely used as precursors for many products in petrochemical industries such as polyethylene, polypropylene, acrylonitrile and propylene oxide. Catalysts 2020, 10, 245 windows, they can be divided into three different categories including large porous, medium porous and small porous zeolites, which are composed of a different number of tetrahedral units, or T atoms of 12, 10 and 8 membered rings, respectively These behaviors make each zeolite serving unique shape selective properties, which are very important for the appropriate applications. Some bulky molecules cannot penetrate into active sites located at microporous channels, and a poor catalytic performance due to a very low reaction rate and a fast deactivation of catalysts is observed To overcome these limitations and to improve the accessibility of molecules into active sites, in recent years modified zeolites obtained by introducing additional larger porous structures have been extensively developed [5,6,7,8]. This comprehensive review opens up perspectives of the recent synthesis approaches of hierarchical zeolite nanosheets and nanoparticle assemblies, as well as the successful production of light olefins via catalytic cracking, ethanol dehydration to ethylene, methanol to olefins (MTO) and other reactions
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