Modified clinoptilolite catalysts for seawater flue gas desulfurization application: Preparation, characterization and kinetic evaluation

• Modified clinoptilolite was prepared as the catalytic packing for seawater flue gas desulfurization application.
• Modified clinoptilolite catalyst improved the desulfurization efficiency in an adsorption tower at 45–85 °C.
• SO2–TPD of catalytic packing was carried on to identify the SO2 desorption activation energy.
• Activity evaluation and kinetic study was employed to elucidate the possible desulfurization mechanism.

Seawater flue gas desulfurization (FGD) process has been adopted by a number of coastal power plants for its lower operation cost. Natural clinoptilolite (clin) was modified by Fe2+ ion exchange, drying, and calcination to prepare a catalytic packing for improving desulfurization efficiency of the adsorption tower. Compared with natural clin, the most active 350-Fe-clin (Fe2+ exchanged clin, calcined at 350 °C) catalyst kept 6–12% higher SO2 removal efficiency at the operation temperature regime 45–85 °C. The acidic effluent of the adsorption tower was below pH 3.0, and S(IV) oxidation efficiency was above 80%. This confirmed that the modified clin catalytic packing played a crucial role on seawater FGD process. Mechanistic and kinetic studies were carried out on the seawater SO2 removal over prepared catalytic packings. XRD, SEM and temperature programmed desorption (TPD) were employed to characterize the catalysts. Kinetic and TPD experiments showed that SO2 desorption energy on 350-Fe-clin was 19.85 kJ/mol, apparent reaction activation energy of seawater FGD on 350-Fe-clin in the scrubber was 20.27 kJ/mol, and liquid phase S(IV) oxidation rate constant in liquid phase was much higher than that of overall reaction. It could be deduced that the reaction rate determining step existed in gas phase reactions.