La0.8Sr0.2Ga0.8Fe0.2O3-δ: influence of the preparation procedure on reactivity toward methanol and ethanol

In this paper a strontium- and iron-doped lanthanum gallate (La0.8Sr0.2Ga0.8Fe0.2O3—LSGF) is prepared by Pechini process and polyacrylamide gel method. The powders are characterized by means of X-ray Diffraction (XRD), X-ray Photoelectron Spectroscopy (XPS), Diffuse Reflectance Infrared Fourier Transform spectroscopy (DRIFT), Thermal Programmed Desorption (TPD), Thermal Programmed Reduction (TPR), BET specific surface area, UV–Vis and Mössbauer Spectroscopy (MS). The activity toward methanol and ethanol is investigated by Infrared (IR) spectroscopy and Quadrupolar Mass Spectrometry (QMS) under several conditions. XRD outcomes reveal the formation of the desired perovskite phase at 900 ◦C, however, small amounts of secondary phases are also present. LSGF synthesized by Pechini process is characterized by a lower amount of secondary phases. On the other hand, LSGF from polyacrylamide gel method has a higher specific surface area. XPS data show that the two samples differ for surface cations segregation, hydroxylation degree and carbonate contamination. These results are also confirmed by DRIFT and TPD measurements. MS and TPR analyses reveal the presence of a small amount of Fe(IV), which is reduced to Fe(III) with H2 (5% in Ar) at about 450 ◦C and with CH3OH vapours at 200 ◦C. Catalytic tests prove that methanol is mainly decomposed into H2 and CO at 400 ◦C, but small amounts of CO2 are also detected. Ethanol undergoes essentially dehydrogenation thus forming acetaldehyde and H2. In oxidizing conditions, both alcohols are oxidized to CO2 and H2O at 400 ◦C, nevertheless, partially oxidized products are also observed. Acetaldehyde is an important product in ethanol oxidation. Under steam reforming conditions, methanol and ethanol give H2, CO and CO2, but acetaldehyde is also observed in ethanol steam reforming. The presence of acetaldehyde, when dealing with ethanol, suggests a difficult C–C bond break. Both the LSGF samples undergo poisoning during the reactions.