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. Partial substitution of the copper ions with other divalent cations leads to considerable modifications in both thermal stability and catalytic properties. Cadmium ions give rise to dramatic deactivation in the hydrogenation of maleic anhydride (MA), while zinc ions favour the hydrogenation 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 and/or hydrogenolysis. When both Mg2+ and Zn2+ ions are present production of GBL is higher and hydrogenolysis essentially does not occur. Furthermore, the Cu/Zn/Mg/Cr catalyst investigated in reaction conditions of industrial interest did not show any scale-up problems or deactivation phenomena with increasing time-on-stream.