Synthesis Of Cyclic Carbonate From CO₂ Catalyzed By Acid/Base Modified SBA-15

Fossil fuel is the most important part of the energy structure in China, which is the lifeblood of the economy. However, fossil fuel combustion led to the excessive emissions of carbon dioxide. As a kind of greenhouse gas, carbon dioxide is responsible for the global warming to some degree. So it is meaningful to study the utilization of carbon dioxide.It is an alternative and green approach to make use of carbon dioxide by cycloaddition reaction to produce cyclic carbonate. However, homogeneous catalysts are undesirable in that because it is necessary to separate the catalyst from the products through a rigorous purification process, which limits its industrial applications. In this paper, we design a kind of heterogeneous catalyst to synthesize cyclic carbonate with carbon dioxide through cycloaddition reaction.SBA-15, a kind of mesoporous molecular sieve, including a little ZnO in its pore, is used as the support to synthesize the acid/base bi-functional catalyst:NH2-SBA-15-ZnO-CuBTC. Base sites come from silane coupling agent grafted by condensation reaction while acid sites come from a kind of metal-organic frameworks—CuBTC, which is synthesized with the help of ZnO. Otherwise, we also analyze the mechanism of ZnO in the synthesis of CuBTC by FT-IR、XRD、SEM.Compared with catalyst with only acid or base sites, NH2-SBA-15-ZnO-CuBTC bi-functional catalyst shows better catalytic performance. The epichlorohydrin conversion reaches 36.4% and cyclic carbonate selectivity reaches 80.8% after the cycloaddition reaction in the following conditions:reaction temperature 120 ℃, carbon dioxide initial pressure 1MPa, reaction time 24 h. The appropriate grafting time of the base sites or the increasing amount of acid sites lead to better catalytic performance. The catalyst shows good stability after the third run, and then the catalytic performance decreases with the loss of acid sites confirmed by XRD.