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 (Ni-MH) battery was investigated by using the CH 4 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 NH 3 aq. solutions followed by calcinations. The resulting NiO exhibited excellent CH 4 conversion in the CH 4 dry reforming, i.e., the CH 4 conversion higher than 96% continued for 50 h when the flow rates of injection gases were controlled at CH 4 /CO 2 /Ar = 10:10:80 ml·min -1 . Although the XRD pattern revealed the reduction of NiO to Ni 0 and the deposition of carbon after the CH 4 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 CH 4 dry reforming over NiO prepared from the spent Ni-MH battery. Keywords: resource recovery, nickel metal hydride secondary battery, nickel metal, CH 4 dry reforming, nickel-based catalyst.