VAPOR-PHASE HYDROGENATION OF MALEIC-ANHYDRIDE TO GAMMA-BUTYROLACTONE. 3. REACTION PATHWAY AND NEW CATALYST COMPOSITIONS

The reactivities of the main products observed in the vapour phase hydrogenation of maleic anhydride (MA) were investigated separately, using a multicomponent catalyst (Cu/Zn/ Mg/Cr = 40:5:5:50, atomic ratio %), obtained by reduction of a non-stoichiometric spinel-type precursor. Tetrahydrofuran (THF) reacted only at high temperature forming small amounts of ethanol (EtOH), while γ-butyrolactone (GBL) gave rise, with high conversion, to overhydrogenation (to butyric acid (BuA) or n-butanol (BuOH) and/or hydrogenolysis (mainly to EtOH. Furthermore, the formation in the catalytic tests with BuA and BuOH of n-butanal (notwithstanding the high H 2 /organic ratio), suggested it as the main intermediate in the hydrogenolysis reaction. Therefore, a new reaction scheme is proposed, evidencing the key role of GBL as the «intersection» of two possible reaction pathways, giving rise to THF or unwanted and low-cost by-products.