III International Conference

PP-II-118THE ROLE OF I-CONTAINING PROMOTER IN THE ACTIVE SILVER SURFACEFORMATION FOR PROCESS OF GLYOXAL SYNTHESISMalkov V.S., Knyazev A.S., Titkov A.I. 1 , Salanov A.N. 1 , Vodyankina O.V., Kurina L.N.Tomsk StateUniversity, Tomsk, Russia1 Boreskov Institute of Catalysis SB RAS, Novosibirsk, RussiaE-mail: vics@sibmail.comThe catalytic properties of polycrystalline silver, morphology and interaction of oxygenwith silver surface were investigated by catalytic tests, SEM and TPD methods. An adding ofethyl iodide into reaction mixture increases both activity and selectivity owing to destructionof active centers which form oxide-like structures on the silver surface.Pure halogens and halogen compounds are widely used as promoters in the processes ofpartial oxidation of organic compounds. It is known the using of halogens as promoters formetallic catalysts (in the processes of methanol oxidation and ethylene epoxidation oversilver) and oxides (for example, in the process of aromatic compounds oxidation over V 2 O 5 ).In consequence of similar conditions of methanol and ethylene glycol partial oxidationprocesses it was proposed that iodine-containing promoters will be favorable in glyoxalsynthesis.In the present work catalytic properties of polycristalline silver promoted by iodoethanewere investigated. It is shown, that adding of C 2 H 5 I into reaction mixture increases selectivityof the process about 10 – 12%, and simultaneously, decreases the yield of deep oxidationproducts, such as CO and CO 2 . So, it contributes to the temperature regime stabilization.Besides, the extreme dependence of glyoxal selectivity vs. C 2 H 5 I quantity in reaction mixturehas been observed. A long-time treatment of catalyst with C 2 H 5 I-containing reaction mixtureleads to decreasing of selectivity because of poisoning of silver surface. The active centers onthe surface were reactivated by means of thermal annealing of silver in oxygen atmospherewith subsequent treatment with reaction mixture.To detail the mechanism of promoting effect the interaction of reaction mixtureconsisting of oxygen and C 2 H 5 I with silver surface by means of thermal programmeddesorption method (TPD) and silver morphology by secondary electron microscopy (SEM)have been investigated. According to TPD results, no ethyl iodide adsorption on the puresurface of polycristalline silver was observed, and C 2 H 5 I chemisorbs competitively withoxygen and prevents forming of oxide-like oxygen stateAg s 2O ( T max = d543K), which is381