Mechanism and Kinetics of Polystyrene Hydrogenation Catalyzed by a Monolithic Pd-NCNTs@FN Catalyst

This work investigated the loading of active metals on monolithic carrier NCNTs@FN through simulation and characterization and found that the active metal (Pd) had a stronger binding with NCNTs and a more uniform dispersion. Meanwhile, the π–π stacking effect between NCNTs and polystyrene (PS) molecules is more significant than that between PS and CNTs, making PS more easily adsorbed. Therefore, the highly active catalyst Pd-NCNTs@FN was prepared. The hydrogenation degree of Pd-NCNTs@FN catalyzed PS reached 92.7%, significantly higher than that of Pd-CNTs@FN (78.1%) under the same conditions. Uniform experiments on PS hydrogenation kinetics were designed. Power law and hyperbolic kinetic models were established, and the corresponding parameters were calculated. From the models, it was found that whether H2 concentration reaches a critical value determines whether H2 pressure affects the hydrogenation rate. In addition, the adsorption of PS is the rate control step in the reaction. The activation energy of Pd-NCNTs@FN catalyzed PS hydrogenation is 47.326 kJ/mol, which is lower than those of other traditional powder heterogeneous catalysts (50–55 kJ/mol), demonstrating the excellent activity of the catalyst.