Effective utilization of waste: development of CH4 dry reforming catalysts from spent nickel metal hydride battery for resource recovery

Abstract

The resource recovery of nickel metal from the spent nickel metal hydride (NiMH) battery was investigated by using the CH4 dry reforming, aiming at reusing it as a raw material of the Ni-MH battery. From the results, a compound identified as a single phase of NiO by XRD was successfully prepared from the spent Ni-MH battery by a series of chemical processes using HCl and NH3 aq. solutions followed by calcinations. The resulting NiO exhibited excellent CH4 conversion in the CH4 dry reforming, i.e., the CH4 conversion higher than 96% continued for 50 h when the flow rates of injection gases were controlled at CH4/CO2/Ar = 10:10:80 ml·min. Although the XRD pattern revealed the reduction of NiO to Ni and the deposition of carbon after the CH4 dry reforming, the deposition of carbon could be suppressed by changing the injection gas ratio. The resource recovery of nickel metal was, therefore, concluded to be possible through the CH4 dry reforming over NiO prepared from the spent Ni-MH battery.