Sustainable production of cyclic carbonates – Exploratory study for turning waste gas into polymers

• Autor(a) principal: Borovkov, Yegor
• Data de Publicação: 2022
• Tipo de documento: Dissertação
• Idioma: eng
• Título da fonte: Repositório Científico de Acesso Aberto de Portugal (Repositórios Cientìficos)
• Texto Completo: http://hdl.handle.net/10362/134023
• topic: Cyclic carbonate; Supercritical CO2; Ionic liquids; 1,2-butanediol carbonate; Domínio/Área Científica::Engenharia e Tecnologia::Engenharia Química

Carbon dioxide (CO2) is not only the most abundant greenhouse gas and waste generated by humans but also an infinite source of carbon with great potential. Creating a circular economy for this gas by using it as a feedstock to produce useful compounds, i.e., cyclic carbonates, is a sustainable approach to adding value to it. The cyclic carbonates market is constantly increasing. They are being used on a big scale as intermediates in plasticisers or pharmaceutical industries, thus highlighting the urge to develop an environmental-friendly and efficient approach for their synthesis. With this in mind, the main goal of this study is to investigate the applicability of highly hydrophobic ionic liquid as simultaneously the reaction medium and physical water scavenger, in the synthesis of butylene carbonate from 1,2-butandiol (1,2-BDO) and CO2. Different ionic liquids and catalysts were tested, at various operating conditions (temperature between 373.2 and 423.2K, pressures between 4 and 12MPa and catalyst amount between 0 and 8%mol), and the best yield of 14% was obtained for zinc acetate dihydrate catalyst (8%mol) combined with 1-hexyl-3-methylimidazolium tetracyanoborate ([HMIM][B(CN)4]) ionic liquid as the water repellent, at 423.15K and 6MPa. The samples were analysed using NMR spectroscopy. Vapor-liquid equilibrium studies with another ionic liquid that could potentially be used in the coupling reaction between CO2 and diols were performed. The 1-hexyl-3-methylimidazolium tris(pentafluoroethyl)trifluorophosphate ([HMIM][FAP]) was employed in ternary (BC+CO2+IL) and quaternary (1,2-BDO+CO2+IL+water) and (1,2-BDO+BC+CO2+IL) systems, and its influence on the potential reaction outcome was discussed while comparing with other binary (1,2-BDO+CO2) and (BC+CO2) or ternary (1,2-BDO+CO2+IL) systems. The phase behaviour was determined at 313.15 K and pressures between 6 and 18 MPa. All the samples were analysed using gas chromatography and Karl-Fischer titration. An exploratory study for the recovery of expensive ILs was made by employing an isopropanol/water solution. It was proven possible to separate IL from the rest of the components.