Study On Preparation Of TiO₂and Ag Loaded On Nay Zeolite And Its Adsorptive Desulfurization Performance

This article presents the preparation of TiO₂and Ag loaded on NaY zeolite, theperformance of the Ag/TiO₂-NaY adsorbent were evaluated using a lab-scale continuous flowfixed-bed reactor for the adsorption desulfurization of benzothiophene. Selective adsorptionof thiophene (TP) and benzothiophene (BT) from model gasolines containing differentaromatics and nitrogen compounds, such as toluene and pyridine, on Ag/TiO₂-NaY zeolitewas studied, and researched the mechanism of adsorption of sulfocompound. The isothermsand kinetic of BT adsorption from petroleumether onto Ag/TiO₂-NaY were studied, and thethermodynamic parameters (ΔG, ΔH, ΔS) for the adsorption of BT were calculated.Composite TiO₂-NaY supports were prepared by sol-gel methods, and a series of massfraction of silver loading on TiO₂-NaY supports were prepared by impregnation of nitratesolution. The effect of TiO₂content on the supported system for desulfurization performanceand adsorbent structure was studied. The adsorbent were characterized by XRD, FT-IR,TG-DTA, BET, SEM and XPS. Results showed that anatase TiO₂is the main phase overAg/TiO₂-NaY adsorbent and the Y-zeolite framework of TiO₂-NaY zeolite was retainedunchanged compared with NaY. Under optimal synthesis conditions: the Ag/TiO₂-NaYadsorbent with CTAB as structural template, m(TiO₂)/m(NaY) ratio of1, m(Ag)/m(TiO₂-NaY)ratio of0.06, and calcination temperature of500℃for3h exhibited the highest adsorptiondesulfurization activity. Static adsorption desulfurization method results showed thatadsorption temperature of50℃, adsorption time of180min, an adsorbent/oil ratio0.01g/ml,the equilibrium adsorption capacity was13.60mg/g. The adsorption capacity was furtherevaluated in a fixed-bed adsorption column. The results showed that at the adsorptiontemperature of80℃, flow rate of0.36mL/min, the breakthrough of sulfur compoundoccurred at67.8ml/g effluent volume, and sulfur capacities for BT were1.34%. The effect ofpyridine on the adsorption TP capacity of the Ag/TiO₂-NaY was more conspicuous than thatof toluene, while the influence of toluene was more conspicuous on the adsorption BTcapacity compared with pyridine. FT-IR of BT on Ag/TiO₂-NaY were carried out in order toinvestigate the adsorption mechanism. The result of infrared spectroscopy indicates that thestrong interactions between the Ag/TiO₂-NaY zeolite and BT compounds was primarilycomplies with both the π-complexation adsorption mechanism and the S-M coordinationmechanism. The inactivated Ag/TiO₂-NaY adsorbent regenerated by heat method at thetemperature500℃, its regeneration sulfur capability is0.991%, regenerated ratio is74.0%.The equilibrium data were modeled by Langmuir and Freundlich equation, whilecompared with Freundlich equation, the Langmuir model can well describe the adsorptionisotherms of BT onto Ag/TiO₂-NaY, and the kinetics for the adsorption process can bedescribed by pseudo-second-order model. And analysis of thermodynamic parameters indicates that BT adsorption is an exothermic, entropy-reducing, and spontaneous process.