Influence of Mo doping on mercury capture and SO2 tolerance of MoxFe6Mn1-xOy magnetic sorbent

Molybdenum (Mo) was doped to Fe-Mn magnetic sorbent (named MoxFe6Mn1-xOy) through co-precipitation method to enhance the SO2 tolerance for mercury capture. The influence of Mo doping on mercury capture and SO2 tolerance of MoxFe6Mn1-xOy sorbent was studied in a fixed-bed experimental device. Temperature programmed mercury desorption (Hg-TPD) test was also conducted to analyze the mercury capture product on the used sorbent. Combing with sorbent characterization, the mechanism of mercury capture and resistance to SO2 poisoning of MoxFe6Mn1-xOy sorbent was explored. The results show that the magnetic Mo0.2Fe6Mn0.8Oy sorbent is an excellent mercury capture sorbent with high SO2 tolerance. O-2 co-existence with SO2 weakens the inhibition from SO2 on mercury capture, but H2O intensifies SO2 poisoning. Mo existing in Mo0.2Fe6Mn0.8Oy sorbent is not active sites for mercury capture, but Mo doping modifies the pore channel and uniformly disperses the Mn-4(+) active sites. Mo doping can also promote the oxidation of SO2 to SO3, which is beneficial to mercury capture. More importantly, after Mo doping, the SO2 tolerance of Mo0.2Fe6Mn0.8Oy sorbent is significantly improved because of a lager affinity of sulfur to Mo. The Hg-TPD test indicates that HgO is the main mercury capture product. Therefore, it can be determined that most of Hg-0 is adsorbed on MnO2 in Mo0.2Fe6Mn0.8Oy via Mars-Maessen mechanism. The existence of SO2 promotes part of Hg2SO4 formation and the co-existence of H2O leads to more Hg2SO4 formation.

Automated summary

Doping molybdenum into Fe-Mn magnetic sorbent enhances mercury capture and SO2 tolerance, with O2 weakening SO2 inhibition on mercury capture and H2O intensifying SO2 poisoning. Mo doping modifies pore structure and disperses Mn-4(+) active sites, promoting SO2 oxidation to benefit mercury capture.