DFT Studies on Al Distribution and Bronsted Acid Sites in Zeolite ECR-1

Abstract

Based on the density functional theory (DFT), the distribution of Al and Bronsted acid sites in zeolite ECR-1 were studied by utilization of SIESTA (Spanish Initiative for Electronic Simulations with Thousands of Atoms) code at DZ2P basis set level. The 8 T cluster model was used to calculate the Al substitution energies at 10 independent T sites, the proton affinity energies and the adsorption energies of NH3 and acetone at the acid site were obtained. The results indicate that T1, T2 and T3 are the priority Al substitution sites in the skeleton of zeolite ECR-1, demonstrating that Al in MAZ and MOR layers of zeolite ECR-1 are rich and poor, respectively, which is consistent well with the experimental results. Bronsted acid is preferentially located in Al1(O8H)Si1, Al2(O12H)Si2 and Al3(O13H)Si3, and the most acidic site is Al3(O13H)Si3.