from first principles PP-I-1

PP-III-50Peculiarities of Partial Oxidation of Glycol over P-Modified Ag CatalystsKnyazev A.S. 1 , Mamontov G.V. 1 , Paukshtis E.A. 2 , Vodyankina O.V. 11 National Research Tomsk State University, Tomsk, Russia2 Boreskov Institute of Catalysis SB RAS, Novosibirsk, Russiakas854@mail.ruPartial oxidation of ethylene glycol using air allows obtaining a number of valuablechemicals, such as glyoxal, glycolaldehyde, glycolic and glyoxylic acid, etc. The most activecatalysts for this process are silver systems. It is known that the effectiveness of Ag in theprocess of partial oxidation of ethylene glycol can be increased by addition of phosphoruscontainingcompounds into reaction mixture or directly into the catalyst composition. Theaddition of alkylphosphates, phosphoric acid, etc., increases the selectivity with respect toglyoxal by 10-15%, and also enhance the ethylene glycol conversion to up to 100%. In thepresent work using in situ IRS we have carried out the investigation of the catalysts forethylene glycol oxidation representing silicagel-supported silver modified by phosphoric acid.It was stated that the following species are formed when glycol interacts with the surface ofthe investigated samples:Ethylene glycol formshydrogen-bonded complexeswith SiOH groups (I) whichare stable up to 125 o C. ThePOH groups form covalentlybound complexes with ethylene glycol (II) which are stable up to 400 o C. Similar structureswith silver are also formed (III), and selective oxidation of ethylene glycol into glyoxalproceeds only in case of two-site adsorption of the diol.Formation of ethers of ethylene glycol and polyphosphate provides high selectivity of theprocess due to the opportunity of consecutive oxidation of diol into glyoxal via formation ofglycolaldehyde. This allows varying the process conditions to produce both glyoxal andglycolaldehyde selectively.Thus, it was shown that when ethylene glycol interacts with polyphosphate-promotedsupported silver catalyst the process may proceed through formation of ether of ethyleneglycol with polyphosphate. This provides high effectiveness of the samples in comparisonwith unpromoted systems.The work was supported by the grant of the Russian Federation Ministry for education andscience (state contract No. 13.G36.31.0001 from 07.09.2010).203