Ni/ZSM-5@Ni/ZnO catalysts for fluid catalytic cracking gasoline desulfurization-aromatization tandem reactions

Abstract

The production of cleaner gasoline requires reducing sulfur and olefin content in fluid catalytic cracking (FCC) gasoline. Herein, Ni/ZSM-5@Ni/ZnO catalysts were synthesized by uniformly coating Ni/ZnO on the surface of Ni/ZSM-5 by electrostatic induced crystallization strategy for FCC gasoline desulfurization-aromatization tandem reactions. The desulfurization activity of Ni/ZSM-5@Ni/ZnO has superior desulfurization activity due to the smaller size of ZnO, higher O vacancy content, and more uniform dispersion of Ni and ZnO relative to the physically mixed Ni/ZSM-5-Ni/ZnO. In addition, coating Ni/ZnO on the surface of Ni/ZSM-5 can reduce the Brønsted acid content of Ni/ZSM-5, increase the Lewis/Brønsted acid value of the catalyst, which inhibits the excessive cracking of FCC gasoline, and improves the liquid yield and aromatics selectivity. After 8 h of reaction, the desulfurization rate, aromatics generation rate and olefin conversion rate of Ni/ZSM-5@Ni/ZnO were 85.58 %, 25.22 % and 49.08 % respectively, which were higher than those of physically mixed Ni/ZSM-5-Ni/ZnO catalysts by 25.34 %, 15.95, and 12.98 %, respectively. Meanwhile, the unique structure of Ni/ZSM-5@Ni/ZnO reduces carbon deposition and delays catalyst deactivation. Density functional theory calculations show that Ni/ZSM-5@Ni/ZnO was more favorable for thiophene desulfurization and has a better ability to adsorb and activate H₂. This study provides a new idea for the development of catalysts for clean gasoline production.