Maja Gabrič

In this study, a comprehensive investigation of PET glycolysis has been performed. The research included the development of analytical techniques, experiments with different reactor systems, and the development of mathematical models to understand the kinetics of the process. Quantitative HPLC analysis was adopted and optimized for the detection of BHET, while the size-exclusion chromatography method was developed to determine the molecular weight distribution of solid PET residues. Over 33 experiments were performed with magnetically coupled shaft-stirred Amar reactors, resulting in more than 300 experimentally determined BHET concentration points at various reaction times, temperatures, catalyst concentrations, and ethylene glycol-to-PET ratios. Afterwards, a kinetic model was developed to describe the observed phenomena with a validation step.

A novel catalytic route from bio-based glyceric acid to acrylic acid and its esters, key polymer precursors, has been developed. This sustainable process involves rhenium-catalyzed deoxydehydration (DODH) in an alcoholic medium, avoiding gaseous hydrogen or other hazardous reagents. Using a supported Re/C catalyst and methanol as solvent, a combined yield of acrylic acid and methyl acrylate of up to 65% was obtained at 150 °C after 72 h under an inert N₂ atmosphere. Moreover, conducting the same reaction under 5 bar of H₂ at an increased temperature of 180 °C boosts the DODH rate constant from 0.21 ± 0.03 to 4.08 ± 0.22 h⁻¹ g_cat ⁻¹, thus yielding more than 90% of DODH products in just 10 h. This sustainable process is easily transferable to other alcohols that yield alkyl acrylates, further expanding the applicability of the presented invention to other monomers and products.

Bio-based glyceric acid, an oxidation product of glycerol, was converted into acrylic acid and its esters, crucial polymer precursors, using a new catalytic approach in a sustainable manner. Avoiding gaseous H2 or dangerous chemicals, the crucial step is Re-catalyzed deoxydehydration (DODH) in an alcoholic medium. In addition to being a solvent and hydrogen donor, alcohol also forms protective ester groups with acrylic and glyceric acids. This study examined several catalysts, alcohols, the presence of H2, and temperatures. Acrylic acid and methyl acrylate were produced in 72 hours with a 65% combined yield using a Re/C catalyst and methanol at 150 °C under N2. This versatile process can also be transferred to other alcohols enabling the production of various alkyl acrylates and monomers.