VAPOR-PHASE HYDROGENATION OF MALEIC-ANHYDRIDE TO GAMMA-BUTYROLACTONE .1. ROLE OF CATALYST COMPOSITION

Cubic spinel-type phases containing excess copper ions may be obtained by controlled oxidation of homogeneous copper-rich coprecipitates. Pa rtial substitution of the copper ions with other divalent cations lead s to considerable modifications in both thermal stability and catalyti c properties. Cadmium ions give rise to dramatic deactivation in the h ydrogenation of maleic anhydride (MA), while zinc ions favour the hydr ogenation of succinic anhydride (SA) to gamma-butyrolactone (GBL). On the other hand, the partial substitution with Mg2+ ions increases the productivity in GBL, inhibiting the reactions of over-hydrogenation an d/or hydrogenolysis. When both Mg2+ and Zn2+ ions are present producti on of GBL is higher and hydrogenolysis essentially does not occur. Fur thermore, the Cu/Zn/Mg/Cr catalyst investigated in reaction conditions of industrial interest did not show any scale-up problems or deactiva tion phenomena with increasing time-on-stream.