OP-II-3

PP-III-17the characteristic structure of the heteropolyacid during the synthesis. DRIFTSstudies of pyridine adsorbed materials showed the presence of strong Bronsted acidsites in these catalysts. The synthesized materials were quite stable and theincorporated HPA did not dissolve in water during the washing steps of the material.Nitrogen adsorption analysis indicated Type IV isotherms, indicating mesoporousstructure, and gave BET surface area values in the range of 180-250 m 2 /g. Activitycomparison of TPA and STA incorporated materials (TPA-75(L) and TRC-75(L),respectively) showed higher activity of STA incorporated material (Fig.1) in ethanoldehydration. A decrease of diethyl ether selectivity and a corresponding increase inethylene selectivity was observed with an increase in temperature (Fig.2) Very highconversion and ethylene selectivity values (approaching to 100%) at temnperaturesof 300-400°C were highly promising. Considering that both of these materials weresynthesized with a synthesis solution containing a W/Si ratio of 0.4, higher activity ofSTA incorporated material was considered to be due to higher number of protons ofSTA and its higher stability in keeping its Bronsted acidity during calcination.Conversion, X EtOH1.00.80.60.40.20.0TPA-75(L)TRC-75(L)180 200 220 240 260 280 300 320 340 360 380 400Temp ( o C)Fig. 1. Ethanol conversionSelectivity1.00.80.60.40.20.0200 250 300 350 400Temp (°C)Ethylene, TRC-75(L) DEE, TRC-75(L)Ethylene, TPA-75(L) DEE, TPA-75(L)Fig. 2. Ethylene and DEE selectivities.References[1]. Pereira C.J. “New Avenues in Ethylene Synthesis”, Science, 1999, 285, 670-671.[2]. Dogu T., Varisli D., Alcohols as Alternatives to Petroleum for Environmentally Clean Fuels andPetrochemicals”, Turk. J. Chem., 2007, 31, 551-567.[3]. Varisli D., Dogu G., Dogu T., “Petrochemicals from Ethanol over a W-Si-based NanocompositeBidisperse Solid Acid Catalyst”, Chem. Eng. Sci., “Petrochemicald from Ethanol over a W-SibasedNanocomposite Bidisperse Solid Acid Catalyst”, 2010, Chem. Eng. Sci., 65, 153-159.[4]. Varisli D., Dogu T., Dogu G., “Novel Mesoporous Nanocomposite WO x -Silicate Acidic Catalysts:Ethylene and Diethyl ether from Ethanol”, Ind. Eng. Chem. Res., 48, 9394-9401, 2009.[5]. Kresge C.T., Leonowicz M.E., Roth W.J., Vartuli J.C., Beck J.S., “A New Family of MesoporousMolecular Sieves”, Nature, 1992, 359, 710.[6]. Ciftci A., Varisli D., Dogu, T., “Dimethyl Ether Synthesis over Novel Silicotungstic AcidIncorporated Nanostructured Catalysts”, Int. J. Chem. Reactor Eng., 2010, in press.Acknowledgements TUBITAK Grant, METU and Gazi University Research Funds.471