活化扩散和支撑层阻力对沸石膜分离性能的影响  

Roles of activated gaseous diffusion and support resistance in MFI zeolite membrane separation

作　　者：甘霏[1] 张舟[1] 朱吉钦[1] 刘辉[1] 李阳[2] 邵潜[2] 贺振富[2] 田辉平[2] 

机构地区：[1]北京化工大学化工资源有效利用国家重点实验室,北京100029 [2]中国石油化工股份有限公司石油化工科学研究院,北京100083

出　　处：《北京化工大学学报（自然科学版）》2008年第6期6-11,共6页Journal of Beijing University of Chemical Technology(Natural Science Edition)

基　　金：国家“973”计划(2004CB719505)

摘　　要：采用Maxwell-Stefan(MS)方程描述分离膜组件中沸石膜及支撑层区域内的晶内扩散、活化扩散、分子扩散和努森扩散,建立了一维定态扩散模型以模型化预测甲烷、乙烷在MFI沸石膜组件中单、双组分的渗透特性。结果表明:支撑层阻力对单组分以及混合物在膜组件中的渗透通量有显著影响,阻力大小与支撑层结构(孔径和空隙率等)相关;支撑层阻力中努森扩散阻力的效应对分子量大的组分以及在较低分离温度下不能忽略;考虑支撑层阻力时,甲烷、乙烷在膜层中气相活化扩散的活化能分别为(8.1±0.2)和(9.2±0.1)kJ/mol,约为文献报道值的1/2;温度越高膜层中气相活化扩散越明显,其对组分总通量的贡献甚至要大于表面扩散。A mass transfer model for predicting permeation fluxes of single gases and a binary mixture of methane and ethane in a modular MFI zeolite membrane and support layer has been developed, in which the surface diffusion and activated gaseous diffusion in the membrane and the bulk and Knudsen diffusion are described by applying the Maxwell-Stefan formulation. It is demonstrated by simulations that the support resistance leads to significantly decreased permeation fluxes of both the single gases and the binary mixture, which is related to the structures of the support layer such as the pore diameter and voidage. It was found that the effect of Knudsen diffusion should be taken into account, particularly for heavier diffusive molecules or at relatively low separation temperatures. The activation energies of surface diffusion of methane and ethane are estimated to be （8.1 ± 0.2） and （9.2 ± 0.1） kJ/mol, respectively, which are about half of the corresponding values reported in literature. The activated gaseous fluxes of methane and ethane increase with increasing temperature, and exceed the corresponding surface diffusion fluxes at elevated temperatures.

关 键 词：甲烷 乙烷 MS方程 渗透通量 支撑层 

分 类 号：TQ028.1[化学工程]