Direct Reaction of Carbon dioxide to Polycarbonate

Abstract

At present, the main source of energy generation around the world is fossil fuel combustion (coal, oil and natural gas); it is also predicted to remain the dominant for the next few decades. A major drawback of combusting fossil fuels is the huge amounts of carbon dioxide (CO2) emissions into the atmosphere, especially with the evolving of the industrial revolution. Due to the fact that CO2 high levels in the atmosphere is linked to trapping sun light, hence global warming; much interest have been invested in the development of carbon capture and storage (CCS) approach. An efficient, valuable and profitable method of storing CO2 is to utilise it as a raw material in industries. This paper is conducted based on experimental work regarding the conversion of CO2 from a challenging waste into a polymer; a high impact and temperature resistance, transparent, easily deformed without breaking, light material. The main features that are investigated in this paper are the synthesis of various types of Zn-based salen complexes (three catalysts, mostly novels), and their utilisation in copolymerisation reactions of CO2 with four different types of epoxides (Styrene oxide, n-hexane oxide, cyclohexene oxide, and propylene oxide. Zn-based salen catalysts have been chosen as no previous work has been carried out in the department regarding such complexes, as well as it is the main outcome from the technical review (preciously submitted as a part of this paper) as that the zinc catalyst can be recommended as the most beneficial among the other metal-centres based salen complexes in terms of CO2/epoxide copolymerisation. More than 30 copolymerisation runs have been accomplished under the effect of different epoxides, catalysts, solvents and different reaction conditions. Overall, the results show that no specific relation can be drawn regarding whether a single catalyst demonstrates the optimum polymer yield through the different epoxide/CO2 copolymerisation; as for a certain epoxide, each catalyst exhibits different solubility drifts under the effect of the same solvent. For instance, complex 3 resulted in the highest yields for both styrene oxide and propylene oxide polymerisation, whereas complex 1 is more favorable for the n-hexane one. A wide range of low and high polymer yields has been observed from 12.2% (utilising styrene epoxide and complex 3) to 96.9% (utilising cyclohexene epoxide and complex 6). No/traceable amounts of cyclic carbonate have been detected in the final product after micro filtration; the case that supports Zn-based catalysts selectivity trend towards the production of polycarbonates over cyclic carbonates.