Molecular Simulation of Hydrogen Storage in Ion-Exchanged X Zeolites

Xiaoming Du

doi:10.1155/2014/189745

Abstract

Grand Canonical Monte Carlo (GCMC) method was employed to simulate the adsorption properties of molecular hydrogen on ion-exchanged X zeolites at 100–293 K and pressures up to 10 MPa in this paper. The effect of cation type, temperature, and pressure on hydrogen adsorption capacity, heat of adsorption, adsorption sites, and adsorption potential energy of ion-exchanged X zeolites was analyzed. The results indicate that the hydrogen adsorption capacity increases with the decrease in temperatures and the increase in pressures and decreases in the order ofKX<LiX<CaX. The isosteric heat of adsorption for all the three zeolites decreases appreciably with the increase in hydrogen adsorption capacity. The hydrogen adsorption sites in the three zeolites were determined by the simulated distribution of hydrogen adsorption energy and the factors that influence their variations were discussed. Adsorption temperature has an important effect on the distribution of hydrogen molecules in zeolite pores.

Highlights

The utilization of hydrogen as a possible substitute for fossil fuels requires the solution of a number of problems related to hydrogen production, transportation, storage, and fuel cell technology [1]
Attention has been focused on light microporous materials such as carbon [5], aluminosilicate zeolites [6, 7], and metal organic frameworks (MOFs) [8] for storing hydrogen by adsorption because the adsorption is reversible and the sorbent can be recycled
Little attention was previously paid to the distribution of adsorption sites and adsorption potential energy for the molecular hydrogen on zeolites

Summary

Introduction

The utilization of hydrogen as a possible substitute for fossil fuels requires the solution of a number of problems related to hydrogen production, transportation, storage, and fuel cell technology [1]. Zeolites are a large class of crystalline aluminosilicate materials that have high thermal stability and regular and single size pores and the diameter of the pores can be controlled by changing the size and charge of the exchangeable cations. They offer enormous potential for storage of gases. The studies on hydrogen storage in X type of zeolites are so far only limited to the conditions of the separate temperatures and low pressure owing to not being readily amenable to experiments. The dependence of the hydrogen adsorption capacity of zeolites on temperature, pressure, cation type, adsorption site distribution, and adsorption potential energy was discussed

Computational Details

Results and Discussion

Conclusions