MFI沸石上对二甲苯的热脱附

MFI沸石（ZS－5型）的骨架结构内含十氧元环的二维孔道［‘］，孔容积0．18cm‘·g－‘，硅沸石（Silicallte－1）是骨架中不合铝的ZSM－5．’‘StMASNMR话可揭示沸石的结构对称性、硅铝比和局部缺陷［习．Nagy等人间提出St－OH缺陷在含铅量高时形成．Woolery等门则认为出OH完全是由于骨架内包藏的桂的存在而产生，并随铝合量降低而增大．ZSM－5、硅沸石的结构特征和对二甲苯（Px）的性质决定了Px在ZSM－5上的吸附特性·本文用’‘StMASNLDEL表征硅沸石及不同含铅量的H、Na型ZSM－5的结构，并用＊W＊＊G巾TA分析吸附于…

The Influence of Micro Structures of Silicalite and Rich-Silica ZSM-5 on Desorption Properties of p-xylene

The structures of silicalite-1 and H、 Na form of ZSM-5 with various SiO2/Al2O3 ratios were characterized by powder XRD, 29Si MAS NMR, and the desorption process of р-xylene (p-x) on the zeolites was investigated by using TG/DTG/DTA. SiOH defects of ZSM-5 have no relation with the content of structural Al. Silicalite-1 possesses perfect framework structure without SiOH defects and structural Al. On a curve of TG/DTG/DTA, p-x adsorbed by silicalite completely desorbs in the range of 57-174℃ by two steps, accompanied with endothermal effect. While on the TG/DTG/DTA curves of H, Na-ZSM-5, there is a third adsorption step of p-x in the range of 180-600℃ with exothermic effect. Below 180℃ the number of desorbed p-x molecules is related to pore space, but over 180℃, it is related to SiOH and positive ion linking with the structural Al.