III International Conference

PP-II-23FTIR STUDY OF THE REACTION MIXTURE (SO 2 +H 2 O+ AIR) EFFECT ON THESTATE OF Pd CATALYSTS SUPPORTED ON Al 2 O 3 AND ZrO 2Danilova I.G., Chesnokov V.V., Zaikovskii V.I., Paukshtis E.A.Boreskov Institute of Catalysis SB RAS, Novosibirsk, RussiaЕ-mail: danig@catalysis.nsk.su.Surface properties of Pd catalysts supported on ZrO 2 , Al 2 O 3 before and after reactionmixture (SO 2 +H 2 O+air) treatment was studied by FTIR spectroscopy of adsorbed CO. Bulkand surface sulfates were found on the supported metal catalysts after sulfation, whereas onlysurface sulfates were formed on the supports. The variation of the numbers and strength ofacidic site of supports, modification of the morphology and the state of metallic nanoparticles,and appearance some electron–deficient metal entities (Pd δ+ , Pd 1+ , Pd 2+ ) were observed aftersulfation.Supported Pd catalysts are used for a variety of technologically important processes, forexample for purification of diesel exhaust gases. One of the key problem for the thesecatalysts is their stability with regard to SO x poisoning. The details of the mechanism ofinteraction of SO 2 -containing gaseous mixture with both oxide and supported metal catalystsare still under discussion. In the present work, the surface state of pure and modified Al 2 O 3and ZrO 2 , and supported Pd catalysts before and after interaction with reaction mixture(SO 2 +H 2 O+air) was studied by FTIR spectroscopy of adsorbed CO and H 2 O.The supported Pd catalysts were prepared by impregnation of δ-Al 2 O 3 , ZrO 2 /Al 2 O 3 ,TiO 2 /Al 2 O 3 and ZrO 2 with water solution of Pd(NO 3 ) 2 . Samples were treated by reactionmixture (50 ppm SO 2 +10 % H 2 O+air) during 18 h at 300 o C. The acidic properties of freshand sulfated samples were studied by FTIRS technique using CO adsorption at 77 K. Themorphology of metallic nanoparticles was characterized by TEM.The formation of several surface sulfates (a.b. at ν S-O 900-1100 cm -1 and ν S=O 1300-1400 cm -1 ) was observed after interaction of the reaction mixture (SO 2 +H 2 O+air) with bothsupports and supported metal catalysts. It was very interesting that the formation of bulksulfates (a.b. at 1110-1260 cm -1 ) was detected only on the supported metal catalysts. Themechanism of bulk sulfates formation and effect of metallic nanoparticles are discussed.It was shown that the metallic particles increase several times in size and spread overthe surface after SO 2 -steam-air treatment. The state of metallic nanoparticles of fresh andsulfated samples was studied by CO absorption at 77 and 293 K within pressure range of0.1-10 torr. The decrease of the intensity of absorbance bands of bridge-bonded CO and thechange of the intensity of a. b. of on-top CO on metallic Pd nanoparticles after SO 2 -steam-airtreatment was found. The appearance of some electron–deficient metal entities (Pd δ+ , Pd 1+ ,Pd 2+ ) was observed after sulfation of supported Pd catalyst as well.205