This study evaluates the incorporation of lanthanum into zeolites Y, Beta, and ZSM‐5 to promote the desulfurization of a gasoline stream directly in the riser of a fluid catalytic cracking (FCC) process. The catalysts were prepared using wet impregnation and characterized by X‐ray diffraction (XRD) (crystallinity and phase integrity), XRF (La content and Si/Al ratio), X‐ray photoelectron spectroscopy (XPS), solid state nuclear magnetic resonance (NMR) of ² ⁹Si and ² ⁷Al, N ₂ adsorption, high‐resolution transmission electron microscopy (HRTEM), temperature‐programmed desorption of ammonia (TPD‐NH ₃ ), Fourier‐transform infrared spectroscopy (FTIR), and pyridine chemisorbed FTIR (FTIR‐Py). Catalytic tests were conducted in a tubular reactor, using a mixture of cyclohexane and thiophene (20000 ppm) at 773 K and 1.3 atm. Catalytic activity was assessed in a fixed‐bed reactor using a cyclohexane/thiophene feed, and product selectivities were quantified by gas chromatography with flame ionization and sulfur chemiluminescence detectors. The addition of lanthanum altered the acidity of the catalysts, reducing the total density of acid sites while increasing the strength of Lewis acid sites. The protonated zeolites, particularly HY, facilitated sulfur removal, achieving a 91% selectivity for H ₂ S through secondary hydrogen transfer reactions. In contrast, the lanthanum‐modified zeolites enhanced thiophene alkylation and condensation reactions, as evidenced by the selectivity observed in La/BEA and La/ZSM‐5, which reached 15%. The results indicated that incorporating lanthanum changes the desulfurization profile, making the catalysts more selective for forming higher molecular weight sulfur compounds, thereby shifting the products toward the FCC diesel range. The modulation of acidity and structural accessibility of the zeolites proves crucial in converting sulfur compounds into H ₂ S or heavy sulfur compounds in the FCC riser, leading to a reduction in the sulfur content of the gasoline fraction, which is economically advantageous.

CATALYTIC REMOVAL OF SULFUR COMPOUNDS FROM PETROLEUM STREAMS

Blends of varying ratios of castor and soybean oils were used to produce biodiesel by alkaline transesterification using the methylic route. To increase the yield of esters, an experimental study using a full 24 factorial design was performed to evaluate the influence of methanol:oil molar ratio, KOH concentration, temperature, and reaction time on the biodiesel produced from each blend. Yields exceeding 95% were obtained, and the highest conversion was 99.05% at 25°C with a reaction time of 20 min using 2% KOH as a catalyst and a methanol:oil molar ratio of 12:1. To reduce process costs based on the amount of methanol used without limiting the conversion to esters, a second set of process conditions was identified, in which a 98.59% conversion to esters was obtained using the same temperature, reaction time, and catalyst concentration but a different methanol:oil molar ratio (6:1).

The development of additives for FCC catalysts aiming at a greater sulfur removal in the gasoline fraction has been a priority with tougher environmental legislation demands. In this context, this study has evaluated the effect of magnesium modified beta zeolite on n-hexane cracking, and the catalytic conversion of thiophene added as contaminant. Catalytic tests’ results, performed at low conversion at 400 ºC with a WHSV of 0.83 s-1 indicate that magnesium addition increased n-hexane cracking from 37.7 to 53.6% in mols, but favored the formation of alkylated sulfur compounds over H2S production.