摘要
Three series of dealuminated Y zeolites have been prepared by chemical extraction of hydrothermally dealuminated Y zeolite(USY)with H_2Na_2EDTA,HCl and H_4EDTA.The unit cell constant,mesopore distribution,acidity and extraframework aluminum(EFAL)of the zeolites were studied with XRD,chemical analyses,adsorption,IR and NH_3-TPD techniques. It was shown that H_2Na_2EDTA only removed EFAL species deposited in the pores of USY, by contrast,HCl and H_4EDTA extract both extraframework and framework aluminum,and make the zeolite framework further dealuminated.Adsorption tests gave evidence that a second- ary pore system exists in these dealuminated zeolites.H_2Na_2EDTA extraction increased both micropore and mesopore volumes,but after HCl and H_4EDTA treatments,new mesopores formed and the micropore volume was decreased.The pyridine-IR and NH_3-TPD measurements demon- strated that EFAL had no evident contribution to the zeolite acidity.
Three series of dealuminated Y zeolites have been prepared by chemical extraction of hydrothermally dealuminated Y zeolite(USY)with H_2Na_2EDTA,HCl and H_4EDTA.The unit cell constant,mesopore distribution,acidity and extraframework aluminum(EFAL)of the zeolites were studied with XRD,chemical analyses,adsorption,IR and NH_3-TPD techniques. It was shown that H_2Na_2EDTA only removed EFAL species deposited in the pores of USY, by contrast,HCl and H_4EDTA extract both extraframework and framework aluminum,and make the zeolite framework further dealuminated.Adsorption tests gave evidence that a second- ary pore system exists in these dealuminated zeolites.H_2Na_2EDTA extraction increased both micropore and mesopore volumes,but after HCl and H_4EDTA treatments,new mesopores formed and the micropore volume was decreased.The pyridine-IR and NH_3-TPD measurements demon- strated that EFAL had no evident contribution to the zeolite acidity.
