Synergetic effect of ZnCo2O4/inorganic salt as a sustainable catalyst system for CO2 utilization

Abstract

Currently, it is essential to consider the rapidly increasing emission of CO2 into the atmosphere, causing major environmental issues such as climate change and global warming. In this work, we have developed the binary catalyst system (ZnCo2O4/inorganic salt) for chemical fixation of CO2 with epoxides into cyclic carbonates without solvent, and all reactions were performed on a large scale using a 100 ml batch reactor. Two mesoporous catalysts of ZnCo2O4 with different architecture, such as flakes (ZnCo–F) and spheres (ZnCo–S) were synthesized and utilized as a heterogeneous catalyst for cycloaddition reaction. The bifunctional property of catalysts is mainly attributed to strong acidic and basic properties confirmed by TPD (NH3 & CO2) analysis. The ZnCo–F catalyst exhibited excellent conversion of propylene oxide (99.9%) with good corresponding selectivity of propylene carbonate (≥99%) in the presence of inorganic salt (KI) at 120 °C, 2 MPa, 3 h. In addition, ZnCo–F catalyst demonstrated good catalytic applicability towards the various substrates scope of the epoxide. Furthermore, the catalytic properties were examined by evaluating the reaction parameter such as catalyst loading, pressure, temperature and time. The proposed catalyst exhibited good reusability for cycloaddition reaction without significant change in its catalytic activity and proposed a possible reaction mechanism for chemical fixation of CO2 with epoxide into cyclic carbonate over ZnCo–F/KI.