(584cv) Elucidation of Solvent Effects: Comparing Gas and Condensed Phase CO2 Hydrogenation

Integrated carbon capture and conversion (ICCC) has been put forward as a promising technique, among many, for the mitigation of atmospheric CO₂. Heterogeneous catalysis has been proposed as the means of converting captured form CO₂ (typically a carbamate or carbonate) to valorized products such as methanol via reactive separation. A key issue in the development of this technology is the harsh conditions brought on by capture agent mediated reactions, and lack of harmony between capture agent solvent and catalyst. A large white space exists in the literature regarding solvent effects relevant to condensed phase CO₂ hydrogenation. The current paradigm of condensed phase catalyst design is to simply use a successful gas phase catalyst in a solvent, with little regard to the stability of either the solvent or catalyst. To address this, an industrially used methanol catalyst, Cu/ZnO/Al₂O₃, reacted with CO₂ and H₂ in a high pressure packed bed reactor and in a batch reactor to directly compare the gas and condensed phase at identical reaction temperature, reaction pressure, catalyst loading, and reagent ratio. Cyclohexane, Hexane, Acetone, Water, Toluene and Ethanol were used as solvents to encompass a wide array of solvent parameters. Effects of dielectric constant, Kamlett and Taft parameters and molecular diameters on catalyst stability and activity are explored. Further, the impact of solvent choice on reaction mechanism is elucidated via the use of ¹³C enriched CO₂ and in-situ magic angle spinning NMR.