芳烃在HZSM-5沸石中的扩散

Diffusion of Aromatics in HZSM 5 Zeolite

苯、甲苯、对二甲苯和间二甲苯在ＨＺＳＭ－５沸石晶内扩散行为采用了活化扩散模型结合非线性程序升温热脱附技术进行了研究，得到扩散活化能（Ｅ）大小顺序是：ＥＢ＜ＥＴ＜Ｅｐ－Ｘ＜Ｅｍ－Ｘ，而且发现从苯到对二甲苯，苯环上每增加一个甲基，Ｅ增加８ｋＪ／ｍｏｌ；常温下扩散系数大小顺序是ＤＢ＞ＤＴ＞Ｄｐ－Ｘ＞Ｄｍ－Ｘ，３５０℃温度时这些Ｄ值近似相等．此外。

Diffusion behaviour of benzene, toluene, p xylene and m xylene in HZSM 5 zeolite has been studied by using an activation model combining a nonlinearity temperature programmed desorption method. The diffusion activation energies obtained are in the order of E B< E T< E p X < E m X .Comparing the activation energies of benzene, toluene and p xylene, it is found that from benzene to p xylene the diffusion energy for increasing a methyl group on aromatic ring increases 8 kJ/mol.The effective diffusivities are in the order of D B> D T> D p X > D m X at 25℃,but almost identical at 350℃. In addition, it is also found that the diffusion activation energy and the intrinsic diffusivity exhibit a compensation effect.