Linking pore diffusivity with macropore structure of zeolite adsorbents. Part I: three dimensional structural representation combining scanning electron microscopy with stochastic reconstruction methods

Abstract

In the present study we have employed advanced experimental and computational methods to characterize the structure of a binderless zeolite adsorbent with improved mass transfer characteristics. Hence, we have used standard and hybrid simulated annealing (SA) methods to stochastically reconstruct in three dimensions the adsorbent structure, by matching low order correlations, namely porosity and two point correlation function. These correlations are measured on two dimensional images obtained by Back-Scattered SEM micrographs taken on different samples of the adsorbent. In the standard SA method we have started from a purely random structure, while in the hybrid method we have started from a uniformly consolidated random sphere pack made by the Lubachevsky–Stillinger algorithm. It is found that the hybrid method preserves, besides low order correlations, pore and mass chord length distribution functions, which contain information on higher order correlations, while the standard SA method matches only low order correlations. This is because in the hybrid process we have initiated the SA algorithm starting from a structure that contains structural information of the sintered zeolite powder, in the form of a consolidated random sphere pack with the porosity of the final structure. Evidently, diffusion studies will enable us to further evaluate the structures developed by each method, as will be explored in a subsequent study.