Production of hydrogen peroxide in liquid CO2. I. Design, synthesis, and phase behavior of CO2-miscible anthraquinones

H2O2 production via sequential hydrogenation-oxidation of anthraquinones (A Qs) represents a potentially efficient process application of liquid or sup ercritical CO2 (ScCO2). First, the use of CO2 as the organic solvent in the process will. eliminate the mass-transfer limitation during the hydrogenat ion and oxidation and also the contamination of the aqueous phase during is olation of hydrogen peroxide. Further, the hydrogen peroxide can be recover ed from CO2 solution without depressurization by liquid-liquid extraction, helping to minimize the energy cost. The primary obstacle to use CO2 as a w orking fluid in the process is the poor solubility of conventional AQs in C O2. Therefore, we designed and generated CO2-philic AQs suitable to be used in the production of hydrogen peroxide. Both mono- and difunctionalized an thraquinones (FAQs) were synthesized by attaching CO2-philic polymers chain s (-CF(CF3)CF2O-) either to mono- or diaminoanthraquinones or to (hydroxyme thyl)anthraquinone. All. FAQs synthesized are highly soluble in CO2 and pre sent liquid-liquid phase behavior with minimum miscibility pressure between 170 and 210 bar. Cloud-point pressures were shifted to lower values by usi ng nonhydrogen bonding linkers between AQ block and CO2-philic tails or by increasing the CO2-philic content of FAQs.