III International Conference

PP-II-20THE IN SITU FTIR STUDY OF THE FORMALDEHYDE OXIDATION OVERSUPPORTED VANADIA CATALYSTSChesalov Yu.A., Popova G.Ya., Semionova E.V., Andrushkevich T.V., Parmon V.N.Boreskov Institute of Catalysis SB RAS, Novosibirsk, RussiaE-mail: chesalov@ngs.ruThe kinetics of the formation and decomposition of surface intermediates informaldehyde oxidation and formic acid decomposition over V 2 O 5 /TiO 2 , V 2 O 5 /Al 2 O 3 ,V 2 O 5 /SiO 2 catalysts was investigated in situ by FTIR spectroscopy. The effect of the supporton structure of surface intermediates and their reactivity was displayed.IntroductionSupported vanadia catalysts are extensively employed as catalysts for many hydrocarbonoxidation reactions. Testing a large number of oxide catalysts in formaldehyde oxidationshowed that an enhanced yield of formic acid is obtained with V 2 O 5 -based catalysts [1].Formaldehyde is found to be oxidized with a high selectivity to formic acid over the vanadiatitaniacatalysts at the temperature range of 100 to 140 °C [2].The objective of the present work is to investigate the mechanism of formaldehydeoxidation over supported vanadia catalysts.ExperimentalThe samples 20% V 2 O 5 /TiO 2 , 30% V 2 O 5 /Al 2 O 3 , 20% V 2 O 5 /SiO 2 were prepared by theincipient wetness impregnation. The samples were dried at 110 o C and calcined at 400 o C for4 h in a stream of air.The in situ IR experiments were performed with a BOMEM MB-102 FTIR spectrometer.A flow-through quartz high-temperature IR cell-reactor with the CaF 2 windows wasemployed.Results and discussionAccording to XRD and FTIR data, V 2 O 5 /Al 2 O 3 and V 2 O 5 /SiO 2 catalysts are the mixturesof crystalline V 2 O 5 and support (γ-Al 2 O 3 or SiO 2 ), whereas V 2 O 5 /TiO 2 catalyst representsvanadium-doped anatase phase, only traces of crystalline V 2 O 5 was determined in this sample.The in situ FTIR spectra of surface species collecting at passing the reaction mixture of2% CH 2 O in air and 1% HCOOH in air through the IR cell-reactor are presented in Fig. 1.Only poly- and dioximethylene species were detected during formaldehyde adsorption onV 2 O 5 /SiO 2 catalyst at 60-80 o C. These complexes desorb completely at 100 o C. We do notobserve any oxidized formaldehyde complexes at 60-200 o C in the case of V 2 O 5 /SiO 2 catalyst.Bidentate (ν as (COO) = 1590, ν s (COO) = 1390 cm -1 ) and asymmetrical formates(ν as (COO) = 1640 cm -1 ) forming during formaldehyde adsorption on V 2 O 5 /Al 2 O 3 catalyst.199