Simulação computacional de adsorção de nitrogênio em zeólita pelo método Monte Carlo utilizando o software RASPA

Abstract

Adsorption is one of the most common processes of separation and purification in the chemical industry, presenting technological, biological and environmental importance. Usually, adsorption operation is analyzed experimentally, obtaining a macroscopic understanding of the phenomenon, basically through the knowledge of kinetic and thermodynamic parameters. In the studies of the adsorption thermodynamics, information related to the adsorption capacity of a given adsorbent can be obtained, as well as to the spontaneity of the process, whether it is exothermic or endothermic, sorption heat, etc. The present work seek to trace a different path from the usual one, starting from a molecular or microscopic perspective of adsorption. The technique that can help to understand the phenomena involved in this unitary operation at the molecular level is molecular simulation. The realization of theoretical research on industrial issues through simulation can not only promote the expansion of the scale, but also reduce the costs related to the project and assist in the development of new products and/or techniques. To perform the computer simulation, a free molecular simulation software called RASPA was used, capable of simulating the dynamic behavior of liquid, gaseous and solid systems. Monte Carlos simulations were used to model the adsorption of nitrogen gas (N2) on a sodalite zeolite (SOD), as it is a system from which experimental data are available. Thus, the present work aimed to simulate and model the N2/SOD system to obtain microscopic details of adsorption through molecular simulation with the RASPA software. Through the results of the molecular simulation at various pressures, it is possible to obtain adsorption isotherms and from them extract data on how the N2/SOD system adsorption occurs. It was observed that the adsorption in the system occurs in physical form and it has formation of adsorvate multilayers on the surface of the adsorbent. This adsorption is verified by the histograms of radial distribution of pairs that provide a distribution of Nitrogen molecules at different distances from the adsorbent.