Surface barriers are influencing the mass transfer in nanopores, but their origin is unclear and can be quite different in different materials. For MFI and CHA membranes studied here, we show that the surface barrier may be a surface diffusion process with higher activation energy than the surface diffusion process in the pores, but other possible mechanisms such as pore blocking and pore narrowing has not been ruled out. The higher activation energy is probably a result of less interaction between adsorbed molecules at the pore mouth than inside the pores, i.e. the barrier is simply a geometrical effect in these materials. For pure components at low concentration in MFI zeolite, we found that barrier is proportional to the product of the molecular weight and heat of desorption. For MFI and CHA zeolite, we observed that the barrier is a function of concentration and approach zero at high concentration and that the barriers of the components become more similar due to interaction between the components in mixtures, which explains the high and selective mass transfer displayed by these nanoporous materials at high concentration.

表面屏障正在影响纳米孔中的传质，但它们的起源尚不清楚，并且在不同的材料中可能大不相同。对于这里研究的 MFI 和 CHA 膜，我们表明表面屏障可能是一个表面扩散过程，其活化能高于孔隙中的表面扩散过程，但不排除其他可能的机制，如孔隙阻塞和孔隙变窄。较高的活化能可能是由于在孔口处吸附的分子之间的相互作用比在孔内少的结果，即屏障只是这些材料中的几何效应。对于 MFI 沸石中低浓度的纯组分，我们发现屏障与分子量和解吸热的乘积成正比。对于 MFI 和 CHA 沸石，