Transforming glycerol and CO2 into glycerol carbonate over La2O2CO3–ZnO catalyst — a case study of the photo-thermal synergism

Abstract

The direct synthesis of glycerol carbonate via glycerol carbonylation by CO₂ suffers from thermodynamic limitation. In this study, light was introduced into the thermal-driven reaction system to synergistically break the equilibrium of the reaction. A series of xLa₂O₂CO₃–ZnO catalysts were prepared using a hydrothermal method and used for the photo-thermal transformation of glycerol and CO₂ into glycerol carbonate. Inductively coupled plasma-atomic emission spectrometry (ICP-AES), X-ray diffraction (XRD), Brunauer–Emmett–Teller (BET), CO₂ temperature-programmed desorption (CO₂-TPD), X-ray photoelectron spectroscopy (XPS), UV-visible (UV-vis) spectroscopy, photoluminescence (PL) spectroscopy and Fourier transform infrared (FT-IR) spectrometry were employed to characterize the crystalline structure, the number of basic sites, textural properties and optical properties of the catalysts. The photo-thermal synergism as well as the cooperation between ZnO and La₂O₂CO₃ contributed to its catalytic performance, thus achieving a glycerol conversion of 6.9% under the reaction conditions of 150 °C, 5.5 MPa CO_2, and 20 mmol_GL g_Cat⁻¹ with a reaction time of 6 h when 20% La₂O₂CO₃–ZnO was used as the catalyst.