Mössbauer spectroscopic characterization of ferrites as adsorbents for reactive adsorption desulfurization

Abstract

Sulfur in transportation fuels is a major source of air pollution. New strategies for the desulfurization of fuels have been explored to meet the urgent need to produce cleaner gasoline. Adsorptive desulfurization (ADS) is one of the most promising complementary and alternative methods. Herein, nanocrystalline ferrite adsorbents were synthesized from metal nitrates and urea using a microwave assisted combustion method. A series of ADS experiments were performed using a fixed-bed reactor to evaluate the ADS reactivity over the ferrites, which was found to have the order MgFe2O4 > NiFe2O4 > CuZnFe2O4 > ZnFe2O4 > CoFe2O4. This effect is explained by the fact that the low degree of alloying of Mg-Fe and the doped Mg increased the interaction between Fe and S compounds, leading to a significant improvement in the desulfurization capability of the adsorbent. Additionally, Mg can dramatically promote the decomposition of thiophene. X-ray diffraction and Mössbauer spectroscopy were used to characterize the fresh, regenerated, and sulfided adsorbents. Although the ferrite adsorbents were partially sulfided to bimetallic sulfides during the adsorption process, they were successfully regenerated after calcining at 500 °C in air.