Waste Eggshell with naturally-functionalized sulfonic groups as excellent support for loading Pd and Ag nanoparticles towards enhanced 1,3-butadiene hydrogenation

Abstract In recent years, high value utilization of waste biomass has been a hot topic in scientific research. Herein, waste eggshell (ES) rich in sulfonic groups was utilized as a natural modified support to load Pd and Ag nanoparticles (NPs), leading to efficient Pd-Ag/ES catalysts for the catalytic hydrogenation of 1,3-butadiene. Through series of characterizations such as SEM, TEM, BET, XPS, and FTIR, it was found that the porous ES not only has hierarchical structures to facilitate the metal dispersion, but also interacts strongly with Pd and Ag NPs via the inherent surface sulfonic groups, which are responsible for the enhanced catalytic performance. The optimized Pd-Ag/ES catalyst exhibited butenes selectivity of 95.8% and 1,3-butadiene conversion of 95% at 45 °C with excellent stability for at least 30 h on-stream. Furthermore, the first-principles density functional theory (DFT) calculation and in situ DRIFTS were performed to explore the plausible mechanism underlying the enhanced catalytic performance due to sulfonic groups. It is suggested that the sulfonic groups can effectively reduce the adsorption energy of butenes and 1,3-butadiene on the surface of Pd NPs which are beneficial to the selectivity of butenes. This work exemplifies that the waste ES with inherent sulfonic groups can be used as excellent support materials for loading active metal nanoparticles for selective hydrogenation reactions. Collectively, we verified that biological waste like eggshell has a great potential in serving as catalyst carrier due to its unique advantages.