One-step synthesis of 1,4-butanediol from maleic anhydride by gas-phase selective hydrogenation over xRe/CuZnZr catalysts

Producing 1,4-butanediol with selective hydrogenation of maleic anhydride has significant financial benefits. This work reported a "green" one-step method for preparing 1,4-butanediol from maleic anhydride in a gas-phase fixed bed continuous flow reactor over an efficient 2Re/CuZnZr catalyst for the first time. In this paper, CuZnZr composite metal oxides were synthesized using the co-precipitation technique, followed by impregnation of Re to produce xRe/CuZnZr catalysts. The study aimed to investigate the effects of including Re on the catalyst's structure and performance. The results obtained from the characterization indicate that the presence of Re in the system restricts the growth of Cu0 grains. In addition, the inclusion of Re facilitated the utilization of ZnO as an effective spacer, reducing the size and quantity of Cu species agglomerates and enhancing active metal dispersion. This phenomenon may be attributed to being the primary factor responsible for the observed enhancement in the activity of the maleic anhydride hydrogenation reaction. Meanwhile, Re facilitated the transformation of γ-butyrolactone, an intermediate resulting from the hydrogenation of maleic anhydride into 1,4-butanediol. The 2Re/CuZnZr catalyst exhibited favorable catalytic activity under the conditions of 190 °C and 6 MPa, resulting in the complete conversion of maleic anhydride and a selectivity of 85 % towards 1,4-butanediol. The catalyst showed consistent catalytic performance throughout the 200 h. The finding about the impact of Re promoter on Cu-based catalysts has the potential to yield a highly efficient catalytic system for alcohol generation.