Chapter 2 - Adsorption phenomena in microporous materials

Abstract

The fact that the sorption behavior of molecules depends on the details of the structure of a microporous material is the basis of many applications of these materials. Compared to pure component adsorption, the knowledge on competitive adsorption in mixtures is very poor. Yet, most applications involve mixtures. Therefore, most of the experimental data on these applications has been analyzed with incomplete data on the number of molecules that are adsorbed. This chapter illustrates the importance of detailed knowledge of sorption behavior to better understand the properties of the system. Over the last few years, molecular simulation techniques have become an attractive alternative to study sorption in microporous materials. Several molecular simulation techniques have been used to study adsorption in zeolites. The earlier studies used molecular mechanics to study the conformation or docking of molecules. All applications of zeolites, however, are at elevated temperatures. Simulations at these conditions require the use of molecular dynamics or Monte Carlo techniques. For such simulations, one needs to sample many million configurations, which requires much more CPU time. The input of simulation is intermolecular potential. It is important to have information on the number of molecules adsorbed in the pores of the zeolite as a function of gas pressure. Molecular simulation gives us molecular insights into some special features of the adsorption isotherms, which include: pure components and mixtures. The chapter concludes with the use of adsorption data to explain some experimental observations in zeolites.