Metal-free Heterogeneous Catalysis for Epoxide to Cyclic Carbonate Conversion under atomspheric CO₂ pressure

Biswas, Tanmoy (2019) Metal-free Heterogeneous Catalysis for Epoxide to Cyclic Carbonate Conversion under atomspheric CO₂ pressure. PhD thesis, Indian Institute of Science Education and Research Kolkata.

Text (PhD thesis of Tanmoy Biswas (12RS031)) 12RS031.pdf - Submitted Version Restricted to Repository staff only Download (7MB)

Abstract

Global warming is one of the emerging challenges that require our immediate attention to tackle climate change. The major contributor for global warming is the excess CO₂ in the atmosphere. The source of this excess CO₂ is the massive consumption of fossil fuels for fulfilment of our day to day energy requirement at a rapid rate. Additionally, alarming rate of deforestation is another cause for increase in the concentration of CO₂ in our atmosphere. Furthermore, the human population is increasing rapidly which will make the situation even worse. One of the ways to handle this problem is to utilize this excess CO₂ to synthetically develop industrially important chemicals under ambient conditions. To achieve this target, scientists have developed a pilot plant which can separate CO₂ from the atmosphere (chapter 1) and store it inside a cylinder which could be utilized later. This thesis describes (from chapter 2 to 5) the conversion of CO₂ into value-added chemical like cyclic carbonate under balloon condition (1.02 atm). These cyclic carbonates molecules are very important due to their wide variety of application like, highly-polar aprotic solvent, solvent for lithium ion battery and monomer for polycarbonate, polyurethane, etc. For this purpose, we have chosen different nitrogen and metal-free polymers as heterogeneous catalyst. In details, we have used graphitic carbon nitride (g-C₃N₄), cyanuric acid-anisidine (CYA-ANIS), guanidinium hydrazine chloride-terephthaladehyde (G-POP-Cl) and poly-ionic liquid (1,n-IL-TTCA) based polymers. The motivations behind the choice of these catalysts are their excellent capability to adsorb CO₂ gas which is one of the most important factors for a CO₂ conversion catalyst. First three catalysts were used along with quaternary ammonium halide [like, tetrabutylammonium bromide and iodide (TBAB and TBAI)] and for the poly-ionic liquid work, potassium iodide (KI) were used as co-catalysts for the epoxide to cyclic carbonate conversion. All these catalysts were utilized for epoxide to cyclic carbonate conversion under 1.02 atmospheric pressure using CO₂ filled balloons as CO₂ source. Additionally, this catalyst mixture was utilized for the conversion of differently functionalized mono and di-epoxide under the similar reaction conditions. These di-cyclic carbonates prepared from di-epoxide are very important for non-isocyanate polyurethane preparation. Furthermore, the reusability of the catalyst was verified using the recyclability study (5 to 7 cycles). The post recyclability characterization of the obtained catalyst suggested that it was capable to retain its stability with a minor degradation. In future, we are planning to prepare some more reactive catalyst which will bring about the conversion without the use of any co-catalyst.

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