Effects of Supports on Pd–Fe Bimetallic Sorbents for Hg⁰ Removal Activity and Regeneration Performance from Coal-Derived Fuel Gas

Abstract

Pd–Fe bimetallic sorbents were shown to be a great potential sorbent for Hg0 removal from coal-derived fuel gas. In this work, activated carbon (AC), Al2O3, and Beta molecular sieve were chosen as supports to disperse Pd–Fe bimetallic components. The effects of the supports on Hg0 removal of Pd–Fe bimetallic sorbents were evaluated using a fixed-bed reactor at 200 °C. The regeneration performance of sorbents was also investigated. The results showed that Hg0 removal activity and regeneration performance over Pd–Fe/AC was the best, followed by Pd–Fe/Beta, and Pd–Fe/Al2O3. The Hg0 removal efficiency of Pd–Fe/AC bimetallic sorbents remained above 80% within 400 min after regeneration 4 times. The Pd–Fe bimetallic sorbents were characterized by N2 adsorption–desorption, Fourier transform infrared spectroscopy, X-ray diffraction, CO pulse adsorption, Hg temperature-programmed thermal desorption, and X-ray photoelectron spectroscopy. The analysis results revealed that three sorbents had a similar Hg0 removal mechanism. Hg0 transformed to Pd–Hg amalgam and HgS after reacting with the sorbents. Pd0 and Fe2O3 were the active species for the removal of Hg0. The removal performance of Hg0 by Pd–Fe/Al2O3 sorbents was the lowest. It is because Pd–Fe/Al2O3 sorbents have the lowest specific surface area, surface content, and dispersion degree of the Pd component. Furthermore, Pd0 over Pd–Fe/Al2O3 sorbents was severely poisoned and transformed to PdS during the regeneration process.