Plastic-Derived Solid Acid Catalysts for the Production of Methyl 2-Hydroxyisobutyrate via Esterification

In this study, we successfully prepare solid acid catalysts using plastic as the starting material for the production of methyl 2-hydroxyisobutyrate (HBM) through the esterification of 2-hydroxyisobutyric acid (HBA) and methanol. Polyethylene (PE) and polyvinyl chloride (PVC) are sulfonated at different temperatures (X) to obtain sulfonated polymer catalysts (SPE_X and SPVC_X). Various characterizations clearly confirm the introduction of sulfonic acid groups (–SO3H groups), which serve as active sites in this reaction, on the PE and PVC surfaces via sulfonation. For the SPVC_X catalysts, an excessively high sulfonation temperature facilitate the loss of chlorine groups (–Cl groups) via dehydrochlorination, resulting in a decrease in catalytic activity. In particular, the –Cl groups improve the acidic properties and accessibility of reactants to the –SO3H groups of the SPVC_X catalysts, leading to a high HBM yield. Therefore, the SPVC_120 catalyst show the highest HBM yield (ca. 75