Adsorption of mercury from heavy naphtha using zeolites

Abstract

Mercury and its compounds are hazardous contaminant which is usually present in crude oil, natural gas or gas condensate. The existence of mercury in feedstock contributes to bad effects to the processing including corrosion of cryogenic equipments or catalyst deactivation. The adsorption performance of Beta zeolites with Si/Al ratios of 10, 30, 100, X zeolite, Y zeolite and ZSM-5 zeolite for removing mercury in heavy naphtha was studied. The heavy naphtha containing 300 ppb of total mercury was used to study kinetic of adsorption and adsorption isotherm in a batch system at temperature of 50C From the speciation of mercury, the heavy naphtha contained both mercury (Hg0) and ionic mercury. For kinetic study, the mercury removal capacity of 30%, 20% and 15% was found for Beta zeolite with Si/Al ratios of 10, 30 and 100, respectively. This is due to the different quantity of their active sites. X zeolite, Y zeolite and ZSM-5 zeolite can remove mercury only 25%, 20% and 7%, respectively. Besides, kinetic experimental data fit well with the pseudo second order equation. In addition, adsorption isotherms of all zeolites were described by Langmuir model. It was found that Beta zeolite with Si/Al ratio of 10 gave the highest maximum adsorption capacity (qmax). Moreover, X zeolite and Beta zeolite with Si/Al ratio of 10 were selected to study their mercury adsorption in a continuous system in order to provide the predictive model for breakthrough curve. It was found that Beta zeolite with Si/Al ratio of 10 and X zeolite reached breakthrough time at 1 h both cases and the maximum of mercury adsorption capacity at 20 and 15 h, respectively.