Effect of temperature, Si/Al and metal loading on the positioning of Pt atoms in MOR-type zeolites

Abstract

Metropolis Monte Carlo (MMC) and molecular dynamics (MD) simulations were performed to study the feasibility of synthesising Pt nanowires inside the pores of zeolites with the MOR framework, such as mordenite. Results show that the temperature, the silicon to aluminium ratio (Si/Al) of the zeolite and the Pt metal loading have an important combined effect on the positioning of Pt atoms inside the framework. MMC simulations indicate that low Si/Al and high metal loadings promote the positioning of Pt atoms inside the main pore channels, which are the places where metal nanowires could be formed. On the other hand, high Si/Al and low metal loadings favour the positioning of Pt atoms in the side pockets of the MOR structure. For Pt loadings of 5% (mol/mol), the guest metal atoms were positioned mainly in the main pore channels for all conditions studied. MD simulation results are in agreement with MMC simulations, showing that when Si/Al = ∞, the trend of single Pt atoms is to move towards the side pockets of the MOR framework, while for Si/Al = 5, the Pt atoms remain in the main pore channel of the structure. Temperature had the effect of increasing the mobility of Pt atoms through the MOR framework.