Catalytic synthesis of salicylic acid via the Kolbe-Schmitt reaction using a polymeric ionic liquid Catalyst

Salicylic acid is widely applied in medicine, agriculture, industry, and personal care. In this study, a polymeric ionic liquid catalyst, P[Chol][PeA], was developed for the synthesis of salicylic acid via the Kolbe-Schmitt reaction between CO 2 and phenol. P[Chol][PeA] was characterized by scanning electron microscopy (SEM), energy dispersive spectroscopy (EDS), Fourier transform infrared spectroscopy (FT-IR), Brunauer–Emmett–Teller (BET) surface area analysis, proton nuclear magnetic resonance spectroscopy ( 1 H NMR), X-ray photoelectron spectroscopy (XPS),Thermogravimetric analysis (TGA) and Gel permeation chromatography analysis (GPC). The optimal reaction parameters were determined as follows: the heterogeneous catalyst designation P[Chol][PeA], CO 2 pressure 1.00 MPa, reaction temperature 140 °C, catalyst loading 5.00 wt%, and reaction time 2.00 h. Under these optimal conditions, the yield and selectivity of salicylic acid were 51.10% and 95.01%, respectively. The heterogeneous catalyst retained its activity without significant loss after ten recycling runs. Furthermore, the response surface fitting results are consistent with the experimental results.