Selective hydrogenolysis of methyl and ethyl acetate in the gas phase on copper and supported Group VIII metal catalysts

Abstract

The selective hydrogenolysis of methyl and ethyl acetate to ethanol over different copper-based and supported Group VIII metal (Pd, Rh, Pt, Co, Ni) catalysts has been studied in the gas phase at 448–623 K and 0.1–6.0 MPa. Measurements of activity and selectivity show that the copper-based catalysts CuO/MgO-SiO 2, CuO/ZnO/MnO/Al 2O 3, and CuO/ZnO/Fe 2O 3 in particular exhibit very high selectivities for ethanol at nearly complete acetate conversions under moderate reaction conditions. In the case of copper-catalyzed methyl acetate hydrogenolysis kinetic measurements indicated a complex reaction network consisting of consecutive-competitive reactions due to transesterification of methyl acetate to give ethyl acetate, followed by its subsequent hydrogenolysis to ethanol. Therefore, the kinetics of selective hydrogenolysis of ethyl acetate have been studied separately. Kinetic parameters of a power rate law were determined by fitting to conversion versus space time data and made it also possible to describe satisfactorily the complex reaction network. In contrast, supported monometallic catalysts containing Pd, Rh or Ni were found to be ineffective in the hydrogenation of the acyl group due to multiple splitting of C-O and C-C bonds forming light hydrocarbons, acetic acid and carbon oxides. Addition of Zn to Pd/Al 2O 3 provides a major change towards higher ethanol selectivity. Furthermore, the catalytic properties of mono- and multimetallic Co/TiO 2 catalysts have been investigated. The use of an electropositive metal, such as Fe, for the preparation of a Co-Rh-Fe/TiO 2 catalyst promotes the formation of ethanol from ethyl acetate with substantially higher conversions.