Experiment, molecular simulation and density functional theory for investigation of fluid confined in MCM-41

MCM-41 was characterized by experiment and molecular simulation. Using the ASAP2010 volumetric adsorption analyzer, adsorption isotherm of nitrogen in MCM-41 at T = 77 K was measured. The BET specific surface, the BJH adsorption cumulative pore volume and average pore diameter were obtained. Simultaneously, grant canonical Monte Carlo (GCMC) simulation was also carried out to investigate the adsorption of nitrogen in MCM-41 at T = 77 K. A set of parameters characterizing MCM-41 were determined by fitting the experiment and simulation isotherms, which is a basis and bridge for predicting the adsorption of other adsorbates in MCM-41. In addition, from the GCMC simulation, we observed the microstructure and the multi-layer adsorption process of the nitrogen of "contact layer --> second layer --> third layer --> capillary condensation". Sequentially, the GCMC and density functional theory (DFT) were used to predict the adsorption of supercritical methane and CCl4 in MCM-41 at ambient temperatures. The microstructure and adsorption process of the CCl4 from GCMC was also observed. The capillary condensation of the CCl4 directly arises without undergoing a completion of contact layer, which is greatly different from multi-layer adsorption of nitrogen. A reasonable explanation is that MCM-41 pore can hold 4-5 layers nitrogen molecules, while only contains 2-3 layers CCl4 molecules. The results from GCMC and DFT are in good agreement, which provides various investigation routes for the confined fluid. (C) 2003 Elsevier Inc. All rights reserved.