Liquid-phase hydrogenation of maleic acid over Pd/Al 2 O 3 catalysts prepared via deposition–precipitation method

Abstract

Succinic acid (SA) is a valuable raw material obtained by hydrogenation of maleic acid (MA). The product selectivity of this reaction is highly dependent on the reaction conditions. This study therefore investigated the effect of the reaction temperature, hydrogen pressure, and reaction time on the liquid-phase hydrogenation of MA by a Pd/Al 2 O 3 catalyst. Complete conversion of MA and 100% selectivity for SA were achieved at a temperature of 90 ◦ C, H 2 pressure of 5 bar, and reaction time of 90 min. Fumaric acid (FA) was formed as an intermediate material by hydrogenation of MA under nonoptimal conditions. The impact of the percentage of Pd dispersion and phase of the Al 2 O 3 support (γ, θ + α, and α) was also examined. The Pd/Al 2 O 3 catalyst with 29.8% dispersion of Pd and γ phase of Al 2 O 3 exhibited the best catalytic performance. Thus, catalytic activity depends not only on the amount of Pd dispersion but also on the physicochemical properties of Al 2 O 3 .