Effect of Alkaline Treatment on Pore and Acidity of Nano-ZSM-5 Zeolite

Effect of alkaline treatment on pore and acidity of nano-sized ZSM-5 zeolite(particle size = 20~50 nm,Si/Al=14.5) was investigated by XRD,N2-adsorption,NH3-TPD,TEM,IR and NMR methods.The results show that under alkaline environment,nano-ZSM-5 with low Si/Al ratio mainly has restricted disilication.And it is more difficult for ZSM-5 zeolite with low Si/Al ratio to desilicate than that with high Si/Al ratio.However,Under appropriate alkaline treatment conditions(/ = 0.19～0.35,T = 60～80 ℃,t = 2～5 h),abundant mesopores can be created,which results in the surface areas and pore volume increased;at the same time,the concentration of weak and middle strong acid was increased,especially the proportion of Lewis acid sites.Different from the opinion in literature,we think that the increased Lewis acid sites were mainly caused by the naked framework aluminium(≡Alδ+),which were generated by alkaline treatment.