Synthesis and characterization of supported spinel ferrite catalysts

Activated carbons from peach stones were prepared and tested as a host matrix of nanodispersed copper, manganese and zinc ferrites. The ferrite active phase was deposited by impregnation using solutions containing respective nitrates salts in an ultrasound bath. X-ray diffraction, Mössbauer spectroscopy, nitrogen physisorption and catalytic tests in WGS and CO-PROX reactions were applied to investigate their characteristics. The XRD and Mössbauer results revealed that a ferrite phase with spinel structure was present in the materials obtained. The presence of superparamagnetic ferrite particles of a size under 10 nm was evident from Mössbauer spectra. The BET surface area of activated carbon support was 945 m²/g. It decreased slightly after the active spinel phase deposition. The measured WGS catalytic activity of the samples followed the line: CuFe₂O₄ /ACP > MnFe₂O₄ /ACP = ZnFe₂O₄ /ACP. This result could be explained with the well-known properties of copper-based catalysts referring to a very high activity at low temperature values. The activity in PROX reaction was very low for all samples studied. The copper ferrite showed a higher catalytic activity than that of manganese and zinc ferrites in PROX reaction.Keywords: ferrites, activated carbon, Mössbauer spectroscopy, WGSR, CO-PROX.