Joint use of XPS and Auger techniques for the identification of chemical state of copper in spent catalysts

Abstract X‐ray photoelectron and x‐ray‐induced Auger spectroscopic analyses of various copper‐containing catalysts have been used to reveal the chemical state of copper during on‐stream in the dehydrogenation of methanol to methyl formate. Three catalyst systems have been selected for this purpose: (1) supported preparations (Cu/S, where S = ZrO 2 , SiO 2 , ZnO, MgO or graphite); (2) mixed oxides of the type LaMn 1‐ x Cu x O 3 ( x = 0.4–0.6); (3) copper‐containing bentonite and sepiolite. The binding energies of the Cu 2p levels in all catalysts after reaction correspond to reduced Cu species, i.e. Cu o and/or Cu + . However, the precise differentiation between these reduced species is only feasible by measuring the Cu L 3 VV x‐ray‐induced Auger parameter. Acocordingly, the energies of the modified Auger parameter for type (1) and (2) catalysts were close to that of Cu o , while they correspond to Cu + species for type (3) preparations.