Catalytic Reduction of Hexaminecobalt(lll) by Pitch- based Spherical Activated Carbon (PBSAC)

摘要

The wet ammonia (NH_3) desulfurization process can be retrofitted to remove nitric oxide (NO) and sulfur dioxide (SO_2) simultaneously by adding soluble cobalt(II) salt into the aqueous ammonia solution. Activated carbon is used as a catalyst to regenerate hexaminecobalt(II), Co(NH_3)_6~((2+), so that NO removal efficiency can be maintained at a high level for a long time. In this study, the catalytic performance of pitch-based spherical activated carbon (PBSAC) in the simultaneous removal of NO and SO_2 with this wet ammonia scrubbing process has been studied systematically. Experiments have been performed in a batch stirred cell to test the catalytic characteristics of PBSAC in the catalytic reduction of hexaminecobalt(III), Co(NH_3)_6~(3+). The experimental results show that PBSAC is a much better catalyst in the catalytic reduction of Co(NH_3)_6~(3+) than palm shell activated carbon (PSAC). The Co(NH_3)_6~(3+) reduction reaction rate increases with PBSAC when the PBSAC dose is below 7.5 g/L. The Co(NH_3)_6~(3+) reduction rate increases with its initial concentration. Best Co(NH_3)_6~(3+) conversion is gained at a pH range of 2.0-6.0. A high temperature is favorable to such reaction. The intrinsic activation energy of 51.00 kJ/mol for the Co(NH_3)_6~(3+) reduction catalyzed by PBSAC has been obtained. The experiments manifest that the simultaneous elimination of NO and SO_2 by the hexaminecobalt solution coupled with catalytic regeneration of hexaminecobalt(II) can maintain a NO removal efficiency of 90% for a long time.