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

AMn(2)O(4) (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 (Hg-0) from syngas. CuMn2O4 sorbent exhibits the highest Hg-0 adsorption performance under simulated syngas, higher than 95 % Hg-0 capture efficiency is obtained at 200 degrees C. Adsorption-regeneration experiments demonstrate that the regenerability of CuMn2O4 is excellent. The influences of syngas compositions on Hg-0 elimination over CuMn2O4 were examined. H2S plays the most important role in Hg-0 removal from syngas, which can be adsorbed on CuMn2O4 surface and transformed into active sulfur species to react with Hg-0 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 Hg-0 adsorption and transformation. HCl promotes Hg-0 removal by forming surface active chlorine species. H-2, CO, and H2O inhibit Hg-0 removal under N-2 atmosphere. However, they exhibit no obvious effect on Hg-0 removal with the assistance of H2S. The excellent Hg-0 capture performance, good regenerability and H2O resistance of CuMn2O4 make it to be a very promising sorbent for Hg-0 removal from syngas at higher temperature.