AMn2O4 (A=Cu, Ni and Zn) sorbents coupling high adsorption and regeneration performance for elemental mercury removal from syngas

Abstract AMn2O4 (A= Cu, Ni and Zn) spinel sorbents synthesized by a low-temperature sol-gel auto-combustion method were for the first time used to eliminate elemental mercury (Hg0) from syngas. CuMn2O4 sorbent exhibits the highest Hg0 adsorption performance under simulated syngas, higher than 95 % Hg0 capture efficiency is obtained at 200 °C. Adsorption-regeneration experiments demonstrate that the regenerability of CuMn2O4 is excellent. The influences of syngas compositions on Hg0 elimination over CuMn2O4 were examined. H2S plays the most important role in Hg0 removal from syngas, which can be adsorbed on CuMn2O4 surface and transformed into active sulfur species to react with Hg0 to form surface-bonded HgS. X-ray photoelectron spectroscopy (XPS) and temperature-programmed desorption (TPD) experiments prove that HgS is formed on the spent sorbent. The surface Cu2+ cations and chemisorbed/lattice oxygens participate in Hg0 adsorption and transformation. HCl promotes Hg0 removal by forming surface active chlorine species. H2, CO, and H2O inhibit Hg0 removal under N2 atmosphere. However, they exhibit no obvious effect on Hg0 removal with the assistance of H2S. The excellent Hg0 capture performance, good regenerability and H2O resistance of CuMn2O4 make it to be a very promising sorbent for Hg0 removal from syngas at higher temperature.