Fixação química de CO2 em epóxidos para a produção de carbonatos cíclicos utilizando-se catalisadores metaloporfirínicos

Abstract

Growing concern over significant increases in anthropogenic carbon dioxide (CO2) levels in the atmosphere, along with the dependence on finite fossil carbon resources for the production of high-value-added molecules, has driven research into the catalytic conversion of CO2. CO2 data from the Mauna Loa Observatory, an atmospheric reference station located in Hawaii, show rising monthly concentrations, reaching about 421 ppm in 2023, with projections of 450 ppm by 2030 and 540-970 ppm in the next century. Although CO2 is used in various sectors of the chemical industry, its application in fine chemistry is limited, indicating the need to explore technologies for its sustainable utilization. CO2 is considered a promising carbon source due to its abundance, renewability, and economic accessibility. Recent research has focused on its conversion into high-value-added products such as alcohols, amines, carboxylic acids, and carbonates. Replacing phosgene with CO2 in the synthesis of organic carbonates represents a significant advance, not only economically but also environmentally. The cycloaddition reaction between CO2 and epoxides to form cyclic carbonates is a process of interest, with various industrial applications. Metal catalysts with porphyrinic ligands have demonstrated efficiency in this process, standing out due to their high activity and selectivity. Macrocyclic ligands, such as porphyrins, have been widely investigated due to their versatility and robustness, proving promising for this application. In this study, the synthesis of six metalloporphyrin complexes and the selective production of cyclic carbonates through cycloaddition reactions between CO2 and epoxides are presented. A theoretical kinetic study was conducted, enabling the determination of an activation energy of 39.76 KJ mol-1 and the thermodynamic parameters in the intermediate states of the cycloaddition reaction of CO2 and styrene oxide. High-resolution mass spectrometry allowed the determination of the activation intermediate of the CO2 cycloaddition, where two styrene oxide molecules are simultaneously activated by one catalyst molecule. Catalysts based on porphyrins, coordinated with metals such as zinc, manganese, and copper, showed efficacy in this process. The continuous development of efficient catalysts and IV the understanding of the mechanisms involved are essential to advance the catalytic conversion of CO2 into high-value-added products