Selective production of BTX aromatics from LPG using moderate-range external magnetic field-assisted Pt-Ga/ZSM-5 molecular sieves catalysts

Abstract

This study evaluated the catalytic performance of 5Ga/ZSM-5 and 0.1Pt-5Ga/ZSM-5 for LPG conversion at 500 °C and atmospheric pressure, focusing on the promotional effects of ZSM-5 zeolite in the presence of an external magnetic field. The addition of Pt to 5Ga/ZSM-5 increased LPG conversion and BTX aromatic yield by 1.14 (from 71.1 %) and 1.10 (from 37.7 %) times, respectively. These enhancements could contribute to a Pt-Ga synergy that enhances dehydrogenation and aromatization activity. The application of a moderate-range magnetic field at 26.1 mT further increased LPG conversion by 1.16 times and shifted selectivity by reducing ethylene yield (by 1.25 times) while increasing BTX aromatics (by 1.18 times). Computational analysis with a finite electric field using GAUSSIAN16 was conducted to explain effects of the magnetic field. The results revealed that a negative Z-axis field enhances reactant adsorption on Brønsted acid sites, lowering activation energies for ethylene conversion to ethoxide (from 28.3 to 24.9 kcal/mol) and for subsequent C—C bond formation during oligomerization (from 25.3 to 21.6 kcal/mol). These effects further promote charge redistribution, reactant-catalyst interactions, and the formation of BTX aromatics and hydrocarbons. This study highlights the potential of combining bimetallic catalysts on ZSM-5 zeolite molecular sieve with magnetic field-assisted processes for efficient LPG conversion and aromatic production, offering valuable insights for advanced catalyst design.