Compressed carbon dioxide as a medium in catalytic hydrogenations: Engineering and chemistry

Abstract

In the frame of designing eco-friendly chemical processes, solvents represent a crucial economic and environmental concern. Compressed carbon dioxide (CO2) is an alternative green solvent for many industrial applications. Herein, we present the most relevant aspects of using compressed CO2 in metal-catalyzed hydrogenation reactions. In the first part, we discuss engineering fundamentals for the description of processes in supercritical fluids, gas-expanded liquids, continuous-flow applications and process design, including safety aspects and examples of heterogeneous catalysis. In the second part, we focus on catalytic systems based on both metal complexes and nano-systems, emphasizing how the catalysts have been adapted to the specificity of CO2. For this purpose, significant aspects such as the catalyst design, the reaction conditions and the use of co-solvents are considered. The main goal of this review is to show the advantages of using this green solvent in catalytic hydrogenations, including a critical analysis concerning its limitations.

Keywords

• Compressed carbon dioxide
• Carbon dioxide expanded liquids
• Homogeneous catalysis
• Nanocatalysis
• Solvent engineering
• Hydrogenation