Metathesis of ethene and 2-butene to propene on W/Al2O3-HY catalysts with different HY contents

Catalysts containing 10wt.% W were prepared using Al2O3-HY mixed supports with various HY contents. The catalytic performance of these catalysts for the metathesis of ethene and 2-butene to propene was determined in a fixed-bed flow reactor at 180degreesC under 0.1 MPa. The 2-butene conversion of these catalysts increases remarkably with the HY content in the range of 0-30 Between 30 and 70wt.% of HY content, the conversion reaches a plateau of 60-63%, which is very close to the thermodynamic equilibrium value of similar to64%. After that, the 2-butene conversion decreases substantially. The propene, selectivity shows the similar trends. The maximum propene selectivity goes up to 88%. By the studies of NH3-TPD, H-2-TPR and UV-vis, the role of HY zeolite in the 10W/Al2O3-xHY is explained in two following aspects: (i) changing the Bronsted acidity of catalysts, which may affect the formation of initial carbene species; (ii) modifying the interaction between W species and support for the formation of active centers with intermediate oxidation number (W4+, W5+, W((6-y))(+) (0 < y < 1)). Based on this information, the optimal HY content for 10W/Al2O3-xHY catalysts is about 50-70%. (C) 2004 Elsevier B.V. All rights reserved.