Novel strategies for extraction and synthesis via combination of supercritical carbon dioxide and ionic liquids

Abstract

The growing apprehension surrounding conventional solvents in recent years has greatly influenced the field of sustainable chemistry. The need to replace toxic, flammable, or environmentally damaging solvents is one of the major challenges that we are currently facing. Consequently, considerable research effort has been invested in the search for an alternative technology that can circumvent the use of environmentally undesirable solvents. In this regard, alternative solvents such as supercritical carbon dioxide (scCO2) have gained attention.This thesis is based on the employment of alternative solvents for the extraction of bioactivecompounds from biomass and for catalysis. In total, three different topics were addressed during the course of this work.(1) The first topic is centered on the application of supercritical carbon dioxide for the extraction of three different bioactive compounds from haskap berries (Lonicera caerulea L.). The parameters optimization of the dynamic streamlined process with different volumetric percentages of ethanol led to the initial removal of lipids, partial separation of iridoids and simultaneous extraction of iridoids and anthocyanins. Furthermore, the dynamic streamlinedprocess developed is a promising approach with broad applicability.(2) The second topic focuses on the employment of ionic liquid technologies in combination with supercritical carbon dioxide, with the aim of extracting cannabinoids from hemp (Cannabis sativa L.). The optimization of this novel alternative process resulted in high extraction efficiencies of cannabinoids comparable to conventional extraction approaches. Additionally, the developed process has the potential to be applied on an industrial level for the extraction of secondary metabolites from different natural resources.(3) The last topic concentrates on cycloaddition reaction of propylene oxide with the aid of supercritical carbon dioxide and supported ionic liquid materials, aiming for the continuous production of propylene carbonate. Significant differences in catalytic activity were observedwhen using ionic liquids in batch mode (homogeneous fashion) and supported ionic liquid materials in continuous flow (heterogeneous fashion). By combining silica support material with ionic liquids, a synergistic effect was noticed. On the one hand, supported ionic liquid phases prepared via physisorption, exhibited higher catalytic activity, however, they were notconvenient in the longer run as a significantly fast decrease in their yield was observed. On the other hand, supported ionic liquid catalysts obtained via chemisorption, displayed lower yields, but a greater long-term stability: a balance between activity and stability is paramount here.