CO2 is a major by-product from petrochemical processes and biomass conversion as well as from shale gas production. It is also one of the most important greenhouse gases. Although extensive research efforts have been made on developing novel adsorbent materials for CO2 capture and amine absorption processes, catalytic upgrading to value-added chemicals will undoubtedly provide strong environmental and economic impetus. In this context, catalytic conversion of CO2 and propylene oxide (PO) to propylene carbonate (PC) is of significant importance, as propylene carbonate is the major building block for battery electrolytes, cosmetics and adhesives, which are essential products for our everyday life.
Up to date, several types of heterogeneous catalysts consisting of supported metal complexes and mixed metal oxides have been investigated for PC synthesis by carboxylation at relatively high temperatures (T ~ 180 oC) and pressures (P > 5 MPa). However, there is a lack of fundamental understanding of intrinsic kinetics of this complex gas-liquid-solid multiphase catalytic reaction system. Therefore, in this paper, a detailed microkinetic modeling on carboxylation of PO to PC is reported based on experimental rate data obtained in a semi-batch reactor. Particularly, basic ion exchange resin (IER) catalysts were evaluated for carboxylation at very mild reaction conditions (55 - 95 oC, 0.5 - 2 MPa). The effects of surface functional groups, PO concentration, temperature, CO2 pressure and catalyst loading on rate of reaction, overall activity of catalysts and selectivity were specifically investigated. These experimental data were interpreted for microkinetic description of Langmuir-Hinshelwood and Eley-Rideal types of mechanism. Details of model discrimination and parameters estimation will be discussed in this presentation.