Selective hydrogenation of maleic anhydride by modified copper chromite catalysts

Cubic spinel-type phases containing an excess of copper ions may be obtained mainly by controlled oxidation of homogeneous copper-rich precipitates, via intermediate chromates. Part of the copper ions may be replaced by other bivalent cations, with corresponding changes in both thermal stability and catalytic properties. In particular the partial substitution of cadmium ions for copper ions gives rise to considerable deactivation in the hydrogenation of both y-butyrolactone (GBL) and maleic anhydride (MA), while substitution of zinc ions causes a slight decrease in the activity with GBL, but favours the hydrogenation of succinic anhydride (SA) to GBL. On the other hand, the partial substitution of magnesium ions for the copper ions gives rise to an increase in the productivity of GBL from MA, inhibiting the reactions of further hydrogenation and/or hydrogenolysis.