Non-hydrocracking of diesel over hierarchical hzsm-5 zeolite to produce gasoline

A series of ZSM-5 zeolites (SiO2/Al2O3 = 50) were desilicated by sodium hydroxide with different concentrations (0.1 mol/L, 0.3 mol/L, 0.5 mol/L and 0.7 mol/L). The crystal morphology, textural property and acidic property of the catalysts were characterized by XRD, TEM, N-2 adsorption-desorption isotherm, NH3-TPD, Al-27 MAS NMR and IR spectroscopy. Meanwhile, the influence of sodium hydroxide concentration in the gasoline yield, products distribution, coke deposition in the non-hydrocracking of diesel were studied. Results showed that mesopores were successfully induced to ZSM-5 zeolites after desilication; more weak acid sites and Lewis acid sites (LAS) were generated; in contrast, the strong acid sites and Bronsted acid sites (BAS) were weakened, leading to an increased ratio of LAS to BAS (LAS/BAS). After alkali treatment, HZ-0.5A exhibited the maximal conversion, yield and selectivity of gasoline; while the HZ-0.5A-1 AC exhibited a lower yield and selectivity. It was also observed that the amount of coke and P/O performed a positive relationship with the LAS/BAS.