Intracrystalline Diffusion in Molecular Sieve Zeolites by the Tracer-Pulse Method

扩散系数是吸附分离系统、气体净化和催化转化过程设计的一个重要性质。多孔沸石系统通常被用来执行输送过程。分子筛分子筛中扩散系数的测量导致了吸附技术和核磁共振方法测得的值之间存在巨大的、无法解释的差异。这些差异的可能解释是(1)没有考虑热效应，(2)没有考虑传质阻力，(3)没有考虑晶体表面的表面势垒阻力，(4)吸附剂晶体结构的差异，以及(5)吸附剂再生的差异。现在有一种独特的可能性，可以用三种独立的方法同时测量相同系统中的扩散系数。对结果的分析将对文献中所报道的巨大差异的困境产生重要的见解，该研究可能为涉及气体在微孔介质中扩散的传质过程提供改进的设计能力。

Diffusivity is an important property for the design of adsorption separation systems, gas purification, and catalytic conversion processes. Porous zeolite systems are often used to perform the transport processes. The measurement of diffusivities in molecular sieve zeolites has resulted in large, unexplained differences between values determined by adsorption techniques and the nuclear magnetic resonance (NMR) method. The possible explanations for these differences are (1) failure to account for thermal effects, (2) failure to account for mass transfer resistance, (3) failure to account for a surface barrier resistance at the crystal surface, (4) differences in the crystal structure of the adsorbent, and (5) differences in the regeneration of the adsorbent. There is now the unique possibility of simultaneously measuring the diffusivities in identical systems by three independent methods. Analysis of the results will yield significant insights into the dilemma of the large differences reported in the literature, and this study may provide improved design capabilities for mass transfer processes involving gas diffusion in microporous media.