Ethenolysis of methyl oleate over supported Re-based catalysts

Abstract

In the ethenolysis of methyl oleate a 18 wt.% Re 2O 7/Al 2O 3 catalyst promoted with tetrabutyltin appeared to be more active per unit weight of catalyst than a promoted 3 wt.% Re 2O 7/SiO 2·Al 2O 3 catalyst. The conversion over 18 wt.% Re 2O 7/Al 2O 3 increased with increasing ethene pressure, while over 3 wt.% Re 2O 7/SiO 2·Al 2O 3 it possessed an optimum value. This difference is due to the fact that the silica-alumina-supported catalyst deactivates in the presence of ethene (2–50 bar), while the alumina-supported catalyst remains stable. For both catalysts at high ethene pressures enhanced self-metathesis of ethene suppresses the self-metathesis of methyl oleate. The turnover number of the 18 wt.% Re 2O 7/Al 2O 3 catalyst increased with increasing molar ratio of methyl oleate to Re 2O 7 to a certain value and then remained almost constant. The turnover number of the 3 wt.% Re 2O 7/SiO 2·Al 2O 3 catalyst, however, decreased with increasing molar ratio, as the deactivation of this catalyst was enhanced by the increase in the amount of methyl oleate. The promoted 3 wt.% Re 2O 7/SiO 2·Al 2O 3 is more active per Re atom at methyl oleate/Re 2O 7 molar ratios of up to 400, while at higher molar ratios the Al 2O 3-supported catalyst is more active per Re atom. The turnover number of Re 2O 7/Al 2O 3 catalysts increased with increasing Re 2O 7 loading, whereas the turnover number of Re 2O 7/SiO 2·Al 2O 3 catalysts decreased with increasing Re 2O 7 loading.