III International Conference

PP-II-63EFFECT OF PARTICLE SIZE ON CATALYTIC PROPERTIES OF SULFATEDZIRCONIALavrenov A.V., Kazakov M.O., Finevich V.P., Duplyakin V.K.Institute of Hydrocarbons Processing SB RAS, Omsk, RussiaE-mail: lavr@incat.okno.ruDetection and examination of particle size effect of sulfated zirconia in Pt/SO 4 2- /ZrO 2 asisomerization catalyst are carried out. It is shown, that sulfated zirconia with the smallestparticle size (70-90 Å) has a maximum catalytic activity in n-hexane isomerization.Catalysts based on sulfated zirconia (SZ) are very effective for different acid-catalizedreactions of hydrocarbons including such industrial processes as oligomerization of alkenes,alkylation of isobutane, isomerization of alkanes. Therefore studying of preparation methodsand structure of these systems has a certain scientific and practical interest. The general aimof this work is to determine correlation between the particle size of sulfated zirconia and itscatalytic activity.Regulation of SZ particle size was provided by varying the synthesis conditions:concentration of ZrO(NO 3 ) 2 solution (50-320 g ZrO 2 per litre); pH of precipitation (8-11) andaging time (0-7 days) of ZrO 2·xH 2 O; sulfate loading (0-13 wt% SO 2- 4 ); calcinationtemperature (500-650 о С).Sulfate loading has the strongest impact on the dispersion and catalytic properties of SZ.Calcining of ZrO 2·xH 2 O without sulfur produces low dispersion ZrO 2 with crystallite sizeabout 200 Å, consisting mainly of monoclinic phase and having no catalytic activity.Increasing the sulfate level to 3-4 wt% leads to the formation of SZ with 80-90 wt%tetragonal phase and particle size less then 100 Å. This structure remains the same from 3 to9 wt% of SO 2- 4 content. Maximum catalytic activity in isomerization of n-hexane is achievedin this interval. Further increasing of sulfate content leads to amorphization of the system anddecreases its dispersion and catalytic activity.While calcining SZ in the temperature range between 500 and 650 ºС crystallite sizediffers only in 20 Å. At the same time catalytic activity grows continuously from zero level toalmost equilibrium conversion of n-hexane. Thus, influence of calcination temperature of SZis related not to the regulation of its dispersion but to the thermal decomposition of the surfacesulfate species, leading to the formation of active sites of the catalyst.278