The influence of oxygen on the surface chemistry of 1,2-propanediol on Pd(111)

The surface chemistry of 1,2-propanediol (PDO) has been studied on oxygen precovered Pd(111) using temperature programmed desorption (TPD) and high-resolution electron energy loss spectroscopy (HREELS). Adsorbed 1,2-propanedioxy (-OCH(CH3)CH2O-) forms from the activation of the O-H bonds. When the concentration of O-(a) is large compared to 1,2-propanedioxy, no H-2 is produced and the dialkoxide reacts to form H2O, CO through decarbonylation, and CO2 through decarboxylation. Unreacted oxygen also desorbs as O-2 at high temperature. Conversely, when the concentration of O-(a) is small relative to 1,2-propanedioxy, the dialkoxide reacts to form decomposition products (H-2, CO), oxidation products (H2O, glyoxal, methylglyoxal, formaldehyde) and deoxygenation products (ethylene, propylene). Co-adsorbed oxygen increases the overall coverage of PDO that can undergo decomposition, which in turn strongly influences decomposition activation barriers and products. (C) 2013 Elsevier B.V. All rights reserved.