Investigation of the reaction kinetics for the direct hydrogenation of maleic anhydride to 1,4-butanediol over Cu-ZnO catalyst

1,4-butanediol serves as a crucial monomeric building block for the production of biodegradable plastics such as PBS and PBAT, and it can also be utilized for the synthesis of derivatives like γ-butyrolactone and tetrahydrofuran. The technology of direct hydrogenation of maleic anhydride to 1,4-butanediol over Cu-ZnO has emerged as a promising production method due to its advantages of a short process flow, mild reaction conditions, cost-effective catalysts, and the capability to co-produce various products. However, at the current stage, the reaction kinetic equations and optimal conditions for 1,4-butanediol formation via direct hydrogenation of maleic anhydride over Cu-ZnO remain unclear, which hinders the development of this production process.

In this study, based on the findings of density functional theory, this study investigated the reaction kinetics of direct hydrogenation of maleic anhydride on Cu211 surfaces and at Cu211-ZnO interfaces using activity evaluation experiments and kinetic Monte Carlo simulations. Through activity evaluation experiments of direct hydrogenation of maleic anhydride, this study examined the effects of temperature, pressure, and hydrogen-to-anhydride ratio on product formation over Cu-ZnO catalysts and identified the optimal reaction conditions for 1,4-butanediol production as 200 °C, 2 MPa, and a hydrogen-to-anhydride ratio of 150. Utilizing the kinetic Monte Carlo method, this study calculated the reaction processes for the direct hydrogenation of maleic anhydride to γ-butyrolactone on Cu211 surfaces and to γ-butyrolactone, 1,4-butanediol, and tetrahydrofuran at Cu211-ZnO interfaces. The optimal reaction conditions for the formation of maleic anhydride to γ-butyrolactone, 1,4-butanediol, and tetrahydrofuran were obtained, respectively. Finally, intrinsic reaction kinetic equations for the direct hydrogenation of maleic anhydride to different products were fitted and derived.

The obtained intrinsic reaction kinetic equations can be applied in the design of actual reactors or process development after considering the influence of diffusion or directly used in studies where diffusion effects are insignificant. This provides a design foundation for the construction of production processes for direct hydrogenation of maleic anhydride to 1,4-butanediol over Cu-ZnO. It is hoped that this study can offer insights and guidance for the understanding of the direct hydrogenation process of maleic anhydride and the development of the biodegradable plastics industry.