Effect of acidic functional groups in a carbon-supported Pd catalyst on efficient acetylene dicarbonylation, followed by hydrogenation to dimethyl succinate†

Abstract

Dimethyl succinate (DMS) is a key raw material for polybutylene succinate (PBS) production, and developing sustainable, low-cost processes and efficient heterogeneous catalysts holds significant economic value. Herein, we demonstrated an efficient one-pot, two-step method using acetylene, CO, and H₂ to produce DMS, in which the Pd/HAC-5 catalyst exhibited optimal activity, achieving an 85.2% acetylene conversion and >99% hydrogenation conversion in the second step. The Pd/HAC catalysts were prepared by loading [Pd₂(μ-CO)₂Cl₄]₂⁻ onto nitric acid-washed activated carbon using a low-temperature impregnation method. Additionally, the ratios of dimethyl maleate (DMM) and dimethyl fumarate (DMF) in the reaction solution had no impact on the hydrogenation conversion. The introduction of surface acidic oxygen-containing functional groups facilitated the uniform anchoring of Pd nanosheets on the activated carbon surface and provided more medium-acid sites. Boehm titration method was used to quantitatively analyze the concentration of acidic groups, and further combined with density functional theory (DFT) calculations, the carboxyl group was confirmed as the main adsorption site for acetylene. Based on the above research, a possible mechanism for the dicarbonylation and hydrogenation reactions was proposed.