Catalytic Systems For The Synthesis Of Styrene Carbonate Via The Coupling Of Carbon Dioxide With Styrene Oxide

Carbon dioxide?CO₂?is not only the main greenhouse gas but also the most abundant and cheapest carborn resource on earth.In recent years,the development of green and efficient way on the chemical conversion of CO₂ has attracted much attention.The synthesis of styrene carbonate?SC?via the coupling reaction of CO₂ with styrene oxide?SO?is one of the most effective means.This work aims to explore effective and recyclable supported catalyst for the coupling synthesis of SC from CO₂ and SO.Composite oxides support of Fe₃O₄@MCM-41 was obtained by integrating mesoporous MCM-41 dervied from tetraethyl orthosilicate and magnetic nanoparticle Fe₃O₄.ZnBr2/Fe₃O₄@MCM-41 was then prepared by supported ZnBr2 on Fe₃O₄@MCM-41 and characterized by infrared spectroscopy?IR?,X-ray powder diffraction?XRD?as well as nitrogen adsorption-desorption isotherms.In addition,the loading of Zn was determined by atomic absorption spectrometry?AAS?.The results of XRD indicated that no obvious change occurred in the crystal structure of Fe₃O₄ and hexagonal mesoporous structure but with decreased order after the introduction of ZnBr2.The catalytic performance of ZnBr2/Fe₃O₄@MCM-41 for the coupling synthesis of SC from CO₂ and SO was investigated.Parameters such as the kind and the amount of catalyst,reaction pressure,reaction temperature and reaction time were optimized.After the reaction,the supported catalyst was recovered by an external magnet and its recyclable catalytic performance was also investigated.The quantitative and qualitative analysis of the liquid mixture was conducted by gas chromatography?GC?and gas chromatography mass spectrometry?GC-MS?,respectively.The results showed that the yield of SC at 81.5% was obtained with 2 molar ratio of tetrabutylammonium iodide?n-Bu4NI?to ZnBr2 and 14.9 wt% Zn loading under 8 MPa at 90 oC for 3 h.The catalytic activity of the supported catalyst almost kept constant during five cycles.The GC-MS results confirmed that the synthesis of SC was accompanied by the formation of by-products including phenylacetaldehyde,acetophenone and phenyl-1,2-ethanediol,in which phenylacetaldehyde and acetophenone was believed to be the main byproducts.Cu?acac?₂/Fe₃O₄@MCM-41 was also prepared by supporting copper?II?acetylacetonate [Cu?acac?₂] on Fe₃O₄@MCM-41.The supported catalyst was further characterized by IR and XRD,and the results indicated that nearly no change in the structure of the composite support after supporting Cu?acac?₂.The catalytic performance of Cu?acac?₂/Fe₃O₄@MCM-41 for the coupling synthesis of SC from CO₂ and SO was tested,and the influence of the loading of Cu and the reaction conditions were investigated.The yield of SC at 91.7% was obtained with 100:1:2 molar ratio of SO:Cu?acac?₂:tetrabutylammonium bromide?n-Bu4NBr?and 2.5 wt% Cu loading under 8 MPa at 100 oC for 3 h.The supported catalyst could be reused up to five times without noticeable deactivation.A binary supported catalyst Cu?acac?₂/n-Bu4NBr/Fe₃O₄@MCM-41 was developed by supporting Cu?acac?₂ as well as n-Bu4 NBr on Fe₃O₄@MCM-41.The binary supported catalyst was characterized by IR,XRD,nitrogen adsorption-desorption isotherms and X-ray photoelectron spectroscopy?XPS?.The binary supported catalyst was employed for the synthesis of SC via the coupling reaction of SO with CO₂,and the reaction conditions were optimized.The binary supported catalyst was simply recovered after the reaction and reused without further treatment.The SC yield at 87.5% was obtained with 2.4 wt% Cu and 6.1 Br wt% loading under 8 MPa at 100 oC for 1 h.No significant loss in the activity was observed at the initial 3 cycles.The leach of the active specie of Br led to obvious decrease in SC yield during the fourth cycle.However,the catalytic activity of the recovered catalyst could be enhanced by adding a certain amount of n-Bu4 NBr to the reaction system.