Study of alginate-based catalysts: an lca-informed optimization of catalyst preparation

This thesis builds upon the group's research interest in utilizing alginate gel beads, a biopolymer derived from renewable sources, as a heterogeneous and sustainable catalyst in asymmetric catalysis. The gel beads with high surface areas and a dense array of carboxylate functional groups provides multiple interaction sites for metal or organic catalysts. These features, made it possible to use this material as a chiral catalyst. The main goal of this project was to conduct a life cycle assessment and sensitivity analysis to identify the steps with the highest environmental impact in order to minimize them. LCA is a systematic methodology aimed at the assessment of the environmental impact of a product in its entire life cycle. The study is conducted following four main steps which ensure consistent results. The results underlined the ethanol used in the process as the most impactful parameter. Based on these efforts were made in eliminating ethanol while maintaining the same results achieved from the previous work. Attempts were made to replace the ethanol solvogel preparation with a direct transition from the hydrogel catalyst to the reaction solvent. Catalytic tests highlighted that at least three washes of the beads with dry THF are necessary to remove the residual water, which affects the reactivity of the system. Similar stereoselectivities were observed between the standard and modified process, yielding 88% and 74% ee, respectively. With these results an integrated LCA study into the process reduced its environmental impact while maintaining comparable outcomes. I worked on optimizing a novel reaction to evaluate the catalytic versatility of alginates, focusing on the asymmetric addition of β-ketoesters to nitrostyrenes. However, reproducibility issues and low stereoselectivities hindered improvements over prior results, necessitating further investigation to enhance reproducibility and expand the materials' potential in organic synthesis.