Speciation of Raney Copper Oxide during High-Temperature Desulfurization

Speciation of copper in the Raney copper oxides (R-CuO) during high-temperature desulfurization has been studied by X-ray absorption spectroscopy. The preedge XANES spectra (8975-8979 eV) of R-CuO exhibit a very weak 1s-to-3d transition forbidden by the selection rule in the case of the perfect octahedral symmetry. A shoulder at 8985-8988 eV and an intense band at 8994-9002 eV can be attributed to the 1s-to-4p transition that indicates the existence of the Cu(II) species. The preedge band at 8981-8984 eV can be attributed to the dipole-allowed 1s-to-4p transition of Cu(I), suggesting an existence of Cu2S during sulfurization. An enhanced absorbance at 9003 eV shows that Cu(0) species may be formed in the sulfurized R-CuO. The main copper species in regenerated R-CuO are CuO (96%) and Cu2S (4%)