Physicochemical investigation of the copper and silver catalysts of the ethylene glycol oxidation

The copper and silver catalysts of ethylene glycol (EG) oxidation into glyoxal have been investigated by means of X-ray photoelectron spectroscopy (XPS), scanning electron microscopy (SEM) and thermal gravimetric analysis (TGA) methods. The data presented in this work show that two types of the carbon deposits, which accompany glyoxal synthesis, are formed. First type of deposits are the graphite-like structures, which can be formed on Cu surface at lean content of oxygen in the reaction mixture. Second type of deposits is the oxycarbon structure, which grows as filaments. Both morphology and the chemical composition of oxycarbon deposits depend strongly on the reaction mixture. Oxygen in the reaction mixture leads to the predominant formation of the oxycarbon filaments on the oxidized metal surface. (C) 2000 Elsevier Science B.V. All rights reserved.