Dealumination of Zeolite Frameworks and Lewis Acid Catalyst Activation for Transfer Hydrogenation

摘要

This study examines a selective removal of Al metal from Al-Beta (BEA), Al-Faujasite (FAU, type Y) and Al-Mordenite (MOR) whose frameworks have high and close Si/Al ratios ≥ 30. Dealumination was performed using acid leaching (nitric acid, 13 M) solution at 100 °C for 20 h. Unlike Al-BEA, Al-FAU and Al-MOR were hardly dealuminated for their ultrastable structure. Solid-state incorporation (SSI) method was applied to incorporate Lewis acidic Sn metal in dealuminated zeolitic frameworks. Newly formed zeolites have numerous vacant tetrahedral sites with a siliceous-rich framework. These zeolites were characterized by powder XRD, elemental analysis, N_2 sorption, DRIFT and ~(27)Al MAS NMR spectroscopies. Meerwein–Ponndorf–Verley (MPV) was selected as a reaction to assess the catalytic performance of prepared zeolites. While SSI-Sn-BEA exhibited superior catalytic activity for the presence of Lewis acid-Sn, FAU and MOR showed less catalytic activity due to their confined structural effects, presence of silanol nest and inadequate Sn incorporation.