Encapsulation Of Pd Nanoparticles Into Zeolites Via Layer Reassembling Strategy And Their Catalytic Hydrogenation Performances

Zeolites encapsulated metal nanoparticles have distinct catalytic properties of both metal active centers and shape-selectivity of zeolites,which exhibit unique catalytic performances in many reactions.Herein,a layer reassembling strategy was proposed to prepare zeolites encapsulated Pd nonparticles?NPs?using layered zeolite precursors RUB-36 and Al-MCM-22P.The synthesis strategy was confirmed by a series of characterizations such as XRD,SEM,TEM/STEM,N₂ physical sorption,solid-state ¹³C CP/MAS NMR,XPS,etc.The obtained catalysts were employed in size selective hydrogenation of substrates containing C=C and C=O groups as well as in hydrodeoxygenation conversion of biomass-derived platform compound.The main findings are as follows:1)Pd precursors were introduced by opening FER layers in RUB-36 through long-chain certrimethylammonium cations?CTA⁺?swelling and ion-exchange process at ambient temperature.Pd@FER was formed with uniform diameter?1.4 nm?Pd NPs during the topotactic transformation from layered zeolite precursors to 3-dimensional zeolites upon calcination.The as-prepared Pd@FER catalyst shows distinct shape-selective properties in hydrogenation reaction.It has relatively lower activity for 1-hexene and almost no activity for1-phenyl-1-cyclohexene compared with Pd/RUB-37 prepared via wet impregnation due to the restrictions of channels in FER zeolite.On the contrary,Pd@FER shows very high hydrogenation activity of benzaldehyde and very low activity in diphenylmethanone hydrogenation,while Pd/RUB-37 exhibits high hydrogenation activity for both benzaldehyde and diphenylmethanone.2)Similarly,Pd@MCM-22 catalysts were prepared using layered zeolite precursor MCM-22P.The catalysts were evaluated in“one-pot”conversion of furfural and acetone to bio-gasoline.The optimized condition of first-step aldol condensation is 240°C for 3 h with furfural conversion of 97%.The optimized condition of second-step hydrodeoxygenation is300?C for 24 h with gasoline yield of 39%.When Ni and NbOx were introduced as co-catalyst,the obtained Pd-Ni@MCM-22 and Pd-Nb@MCM-22 can further enhance gasoline yields up to 46%and 47%.