Facile Synthesis of Silicon-Based Materials Modified Using Zinc(Ⅱ) 2-Bromoacetic as Heterogeneous Catalyst for the Fixation of CO2 into Cyclic Carbonates

Abstract

Much effort has been devoted to the development of efficient heterogeneous catalysts for the conversion of carbon dioxide (CO2) into high-value chemicals. Generally, the cycloaddition of CO2 to epoxides is considered a green and atom-economic reaction for the production of cyclic carbonates. Based on this, three kinds of silicon-based catalysts modified using zinc(Ⅱ) 2-bromoacetic (Si-ZnBA-n, n = 1, 2, 3) were facilely synthesized and employed for the chemical fixation of CO2 to epoxides with the use of potassium iodide (KI). A series of characterization techniques were used to characterize the textual structures and physicochemical properties of Si-ZnBA-n. The synergistic effects of Zn, –NH2, –OH and the nucleophilic group guaranteed the catalytic activity of Si-ZnBA-n. Si-ZnBA-1 exhibited the best catalytic activity among Si-ZnBA-n because Si-ZnBA-1 possessed the highest Zn content. Additionally, the effects of the reaction conditions (temperature, pressure, time and catalyst loadings) were also discussed. The propylene carbonate (PC) yield could reach 97% under 130 °C, 2 MPa, for 5 h without the employment of organic solvent, and its selectivity was 99%. In addition, the recycling property of Si-ZnBA-1/KI was also investigated, and the catalytic system exhibited good cycle performance. Meanwhile, the catalyst showed outstanding versatility for CO2 application to various epoxides, and a possibly synergistic reaction mechanism was proposed. Finally, a dynamic model was developed to discuss the activation energy of the CO2 cycloaddition reaction over the Si-ZnBA-1 catalyst.