Organic Carbonates from CO2: Strategies for enhanced sustainable synthesis

André, Paulo José Lourenço

http://hdl.handle.net/10362/91215

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Autores

André, Paulo José Lourenço

Orientador(es)

Zakrzewska, Małgorzata

Nunes, Ana

Resumo(s)

Carbon dioxide is among the largest anthropologically produced waste, and its usage as a carbon source has long been suggested as a way to add value to carbon used. Therefore, the use of CO2 has become an attractive strategy for energy production, providing another source of carbon. Within this project, several strategies were employed to optimise the synthesis of cyclic carbonates using CO2, from both epoxides and diols. Arylhydrazone metal complexes, together with tetrabutylammonium bromide, TBABr, as the co-catalyst, were used to catalyse the reaction of CO2 with epoxides and conversion of 88% was achieved, at 333K and 4MPa. The alcohol conversion was performed in a biphasic system composed of supercritical CO2 and ionic liquids, with the latter being used as a physical water trap. The ionic liquids studied were 1 hexyl-3-methylimidazolium tetracyanoborate, [hmim][TCB] and 1-hexyl-3-methylimidazolium tris(pentafluoroethyl)trifluorophosphate [hmim][eFAP]. The highest yield achieved for 1,2-propanediol, under 398K and 11 MPa, oscillated around 8% for [hmim][TCB]. In order to understand phase behaviour for the systems developed, several phase equilibrium studies were performed. The optimised condition of pressure that allowed for the sufficient water removal was under 12 MPa. All the samples were analysed through NMR spectroscopy, infrared spectroscopy (FT-IR), gas chromatography and supported by Karl-Fischer coulorimetric titration. The innovative strategy of using ionic liquids as a physical water trap in the conversion of diols investigated in this project serves a proof of concept, and the yield obtained is competitive when compared to data presented in the literature, for the same reaction conditions.