Tuning the location of Brønsted sites in ZSM-5 zeolite via ion exchange to regulate the catalytic performance in the conversion of methanol to hydrocarbons (MTH)

• Grant number: 25/06505-4
• Support Opportunities: Scholarships in Brazil - Scientific Initiation
• Start date: June 01, 2025
• End date: May 31, 2026
• Field of knowledge: Engineering - Chemical Engineering - Chemical Technology
• Principal Investigator: Leandro Pierroni Martins
• Grantee: Izabela Maria de Souza
• Host Institution: Instituto de Química (IQ). Universidade Estadual Paulista (UNESP). Campus de Araraquara. Araraquara , SP, Brazil

Abstract

The conversion of methanol to hydrocarbons (MTH - methanol to hydrocarbons) using acidic zeolites, especially ZSM-5, is closely related to the pronounced confinement effect of the reaction intermediates in the catalyst pores, composed of straight and sinusoidal channels. These two channels have an intersection point with a diameter slightly larger than that of the channels. The latest studies at MTH have shown that the more prominent decrease in aluminum atoms located at the intersection (and consequently of the Brønsted acid sites) and relative enrichment of atoms distributed in the channels increases the formation of propene and butene. In contrast, increasing the density of aluminum atoms at the intersection promotes the formation of ethene and aromatics. The point is that this distribution is controlled by synthetic procedures, with the addition of structure-directing agents that can be sodium, lithium, or tetramethylammonium cations. This project proposes the study of ion exchange isotherms with alkylammonium and sodium cations, using the cations' ionic concentration and steric hindrance to regulate the density of Brønsted acid sites. This simple procedure is expected to improve the performance of a ZSM-5 catalyst, originally with a high density of acid sites (Si/Al = 11), increasing the catalyst stability and modifying selectivity to hydrocarbons.