Acetaldehyde behavior over platinum based catalyst in hydrogen stream generated by ethanol reforming

Due to the greenhouse effect, hydrogen production from bioethanol reforming is a very important subject in heterogeneous catalysis research. Pt based catalysts are employed in H-2 purification processes and also as electrocatalysts of PEM ("Proton Exchange Membrane") fuel cells. Hydrogen obtained from ethanol reforming may contain, as contaminants, acetaldehyde and small amounts of CO. This aldehyde can be decarbonylated on Pt based catalysts generating carbon monoxide and methane, rendering the hydrogen purification more challenging. Moreover, acetaldehyde might also change the electrocatalyst behavior. Therefore, this contribution aims at studying the acetaldehyde behavior in the presence of platinum based catalysts in hydrogen atmosphere. The Pt/SiO2, Pt/USY catalysts and an electrocatalyst were characterized by n-butylamine, H-2 and CO2 adsorption, ATG/DTG measurements and cyclohexane dehydrogenation reaction. It was observed that the acid basic properties of the supports promote condensation reactions. When in contact with Pt based catalysts, acetaldehyde undergoes C-C and C=0 bond scissions. The former occurs at a wide range of temperatures, whereas the latter only at low temperatures (<200 degrees C). The C-C bond scission (decarbonylation) produces methane and CO. The C=0 bond scission generates carbon residues on the catalyst as well as oxygen species, which in turn is able to eliminate CO from the catalytic surface. The data also show that decarbonylation is not a structure-sensitive reaction. (C) 2010 Professor T. Nejat Veziroglu. Published by Elsevier Ltd. All rights reserved.