Abstract Owing to the hierarchical porosity and proper acid site, nanosheet ZSM-5 zeolite (ZN-2) has been reported good performance for catalytic cracking of hydrocarbons, but faces mesopores sacrifice by interlayer… Click to show full abstract
Abstract Owing to the hierarchical porosity and proper acid site, nanosheet ZSM-5 zeolite (ZN-2) has been reported good performance for catalytic cracking of hydrocarbons, but faces mesopores sacrifice by interlayer condensation after calcination during preparation. In this work, two pillared nanosheet HZSM-5 zeolites were successfully synthesized to stabilize the hierarchical structure between nanosheet layers, by dual-template ([C22H45N(CH3)2C6H12N(CH3)2C6H13]Br2 and tetrapropylammonium hydroxide) method and Si-precursor (tetraethylorthosilicate) intercalation. Dual-template strategy (DZN-2) was demonstrated preserving more mesopores between individual nanosheet with better channel connections than Si-intercalation method (PZN-2). Effects of pillared structure on catalytic activity, light olefins selectivity as well as catalytic stability for n-decane catalytic cracking were systematically investigated. The uniquely pillar-designed structure facilitated diffusion of product and restricted the secondary reaction such as hydride transfer or aromatization which consumed light olefins (including ethylene, propylene and butene). DZN-2 catalyst gave the highest light olefins selectivity up to 37.8% at 500 °C compared with PZN-2 and the parent ZN-2, with n-decane conversion of ca.92%. PZN-2 prepared by Si intercalation also exhibited a higher light olefin selectivity of 28.2% than ZN-2 (21.2%), whereas a lower conversion ascribing to the decreased Bronsted acidity with the introduction of Si-pillars. Moreover, DZN-2 displayed an outstanding anti-coking stability with deactivation rate (rd) of only 0.88 during 16 h test at 500 °C, ascribing to the facilitated diffusion of coke precursors.
               
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