From Synthesis Gas to a Clean Transportation Fuel Dimethyl Ether: New Nanocomposite Bifunctional Catalyst Pairs

A. Arslan, A. Bayat, G. Celik, T. Dogu
Middle East Technical University, TR

Keywords: dimethyl ether, syngas, bifunctional catalyst, silicotungstic acid, zirconia


Diemethyl ether (DME) is a promising diesel fuel alternative due to its high cetane number and clean burning properties. Direct synthesis of DME from syngas has major thermodynamic advantages over the conventional process. Technological development of direct synthesis requires new bi-functional catalysts involving both methanol synthesis and dehydration sites. In this work, new catalysts were synthesized for both methanol synthesis and dehydration and performances of different pairs of these catalysts were tested in DME synthesis at 50 bar. For methanol synthesis, a Cu-Zn-Zirconia was synthesized and its performance was compared with Cu-Zn-Alumina. For methanol dehydration, a silicotungsticacid incorporated SBA-15 type nano-composit material (STA@SBA-15) was synthesized. Its performance was compared with γ-Alumina. Surface area of STA@SBA-15 (W/Si=0.4) was 187 m2/g, XRD analysis indicated ordered mesoporous structure. Quite high DME yield was obtained with (STA@SBA-15)+(Cu-Zn-Alumina). Highest DME selectivity values were obtained in the temperature range of 220-260oC. CO conversion approaching to 20% were obtained at a space time of 0.24 Catalyst mixture, which was composed of zirconia based methanol synthesis catalyst and γ-Alumina showed high DME selectivity in the temperature range of 200-225oC. Addition of CO2 to the feed mixture was shown to hinder WGSR and increase DME selectivity.