Role of Acid Site Density and Pore Type on the Brønsted Acid Strength of Zeolite H-ZSM-5

Abstract The Brønsted acid strength of the widely used zeolite H-ZSM-5 was investigated as a function of pore type and distance between acid sites using computational techniques. The straight channel was shown to be the most acidic, with the acid site placement of four Si T-sites apart being the most acidic based on the NH 3 adsorption energy. In addition, the optimal acid site configuration for adsorption was analysed using two sample molecules - ethene and butadiene - that could interact with both acid sites. The distance between acid sites was shown to be significant mostly for butadiene adsorption which was attributed to an interplay between dispersive forces and charge transfer effects. These findings are expected to contribute to a more effective zeolite design and experimental strategies. Graphical Abstract