Production of hydrogen peroxide in CO2

H2O2 production via sequential hydrogenation-oxidation of anthraquinones represents a potentially efficient process application of liquid or supercritical CO2. Both mono- and difunctionalized anthraquinones (FAQs) were synthesized by attaching CO2-philic polymers chains (-CF(CF3)CF2O-) either to mono- or diaminoanthraquinones or to (hydroxymethyl)anthraquinone. All FAQs synthesized were highly soluble in CO2 and presented liquid-liquid phase behavior with minimum miscibility pressure between 170 and 210 bar. Cloud-point pressures were shifted to lower values by using non-hydrogen bonding linkers between AQ block and CO2-philic tails or by increasing the CO2-philic content of FAQs. Pd-catalyzed hydrogenations of fluoroether functionalized anthraquinones (FAQs) were conducted in liquid CO2 (P=235 bar) at room temperature in a high-pressure batch reactor under a ten fold excess of hydrogen, while varying the catalyst loading and catalyst particle size. True kinetic constants, diffusion coefficients and effective diffusivities were determined by simultaneous regression of the kinetic data. The H-1 NMR analysis of the FAQs after a hydrogenation-oxidation cycle showed no indication for "deep" hydrogenation or degradation of the linker. Using FAQs with relatively short fluoroether tails, we could readily achieve conditions where hydrogenation in CO2 was kinetically controlled.