The Removal of Benzothiophene from Model Diesel on NaY and NiY Zeolites: Equilibrium and Kinetic Studies

Abstract

Abstract This work investigates the adsorption of sulfur compounds in model fuel (benzothiophene dissolved in n-octane) on NaY and NiY zeolites from the points of adsorption equilibrium and kinetics. The crystal structures, textural properties and chemical compositions of zeolites were characterized by XRD, N2 physisorption and ICP-AES, respectively. The adsorption of sulfur from model diesel was processed in a batch experiment on NaY and NiY zeolites, and the effects of adsorption temperature and adsorption time on adsorption capacity were investigated. The experimental isotherm data were fitted using Langmuir, Freundlich and Toth models. The pseudo-first order, pseudo-second order, pseudo-n order and intra-particle diffusion models were applied to fit the kinetic data and determine the adsorption mechanism. It is observed from the correlation coefficient (R2) that Toth model is more appropriate to depict the isotherm equilibrium adsorption process and the sulfur uptake process follows the pseudo-n order rate expression on NaY and NiY zeolites. The diffusion study indicated that the adsorption of benzothiophene is controlled by two steps. Moreover, the results of the relative error (RE) analysis further confirm the conclusion of the kinetic study. Thermodynamic studies demonstrated that the adsorption process is exothermal and spontaneous. The equilibrium adsorption sulfur capacities are 20.66 and 28.21 mgS˙g−1 on NaY and NiY zeolites at 50 °C, respectively.