Production of Hydrogen Peroxide in Liquid CO₂. 2. Catalytic Hydrogenation of CO₂-philic Anthraquinones

Abstract

Pd-catalyzed hydrogenations of fluoroether-functionalized anthraquinones (FAQs) were conducted in liquid CO 2 (P ) 235 bar) at room temperature. The kinetics of the hydrogenation of the FAQs in liquid CO 2 was investigated in a high-pressure batch reactor under a 10-fold excess of hydrogen, while varying the catalyst loading and catalyst particle size. The pressures employed were such that H 2 , CO 2 , and FAQ formed a single phase. The 1 H NMR analysis of the FAQs after a hydrogenation-oxidation cycle showed no indication for "deep" hydrogenation or degradation of the linker. True kinetic constants, diffusion coefficients, and effective diffusivities were determined by simultaneous regression of the kinetic data. The diffusion coefficients of the FAQs decreased as the length of the fluoroether tail increased. Small catalyst particles and high stirring rates totally eliminated the external transport limitations. The nature of the linking group and the spacer (between the tail and the anthraquinone block) affected the reactivity of FAQs in the hydrogenation process. Using FAQs with relatively short fluoroether tails, we could readily achieve conditions where hydrogenation in CO 2 was kinetically controlled.

Production of Hydrogen Peroxide in Liquid CO2. 3. Oxidation of CO2-Philic Anthrahydroquinones

“…Production of Hydrogen Peroxide in CO 2. Production of hydrogen peroxide based on the anthraquinone−anthrahydroquinone process is an ideal target for CO 2 technology . First, the replacement of the organic solvent with CO 2 will eliminate the organic contamination of the aqueous product during the extraction stage.…”

“…Functionalized anthraquinones (FAQs) exhibit liquid−liquid phase behavior with a minimum miscibility pressure that varies significantly with the structural parameters of the FAQ. We concluded that generation of FAQs with several short CO 2 -philic tails linked to anthraquinone by ether, C−C, or N−C links would provide the best phase behavior results 9a 1 Functionalized anthraquinones (Kr, poly(perfluoropropylene oxide) polymer). …”

“…Kinetic analysis indicated that the ester-functional FAQs were 2 times as reactive as the amide variants. As the diffusion coefficients of FAQs in bulk CO 2 vary inversely to the molecular weight of the CO 2 -philic tail, we could achieve kinetically controlled hydrogenations for small particle size catalysts and low-molecular-weight CO 2 -philic tails 9b…”

“Single” Pd(0) Atom Encapsulated in Multiporphyrin Arrays as a Highly Efficient Heterogeneous Catalyst

“…Palladium-catalyzed reactions such as hydrogen production, hydrogenation, and the Heck reaction have attracted much attention because of their importance to clear energy development and organic synthesis applications. , Although many Pd(0)-based catalysts are well established, catalyst separation and enhancement of catalytic activity are still large challenges and continue to be the focus of intense research. Over the last three decades, several elegant approaches have been explored to overcome the limitation of catalyst separation, for example, aqueous and fluorous biphase catalysis, reactions in supercritical media, and catalyst immobilization onto solid supports …”

Functionalization of poly(4‐chloromethylstyrene) with anthraquinone pendants for organic anode‐active materials

“…In search of the n‐type redox sites to bind to the non‐conjugated main chain, we focus on anthraquinone (AQ) derivatives based on the following characteristics: (i) the 2e − reaction for the ultimate charging (AQ + 2e − = AQ 2− ) that allows the charge storage with the closed‐shell system and leads to the inherently large storage density,27–29 (ii) the robustness that withstand high levels of labile atmospheres during the well‐known anthraquinone process for the production of H 2 O 2 ,30–34 and (iii) the suitable redox potentials in the range of −0.5 to −1 V versus Ag/AgCl35, 36 which is more negative than those of the p‐type organic cathode‐active materials such as poly(1‐oxy‐2,2,6,6‐tetramethylpiperidin‐4‐yl methacrylate) (PTMA) and poly(1‐oxy‐2,2,6,6‐tetramethylpiperidin‐4‐yl vinyl ether) (PTVE) near +0.8 V37–58 and yet sufficiently more positive than that of the Li anode 59–61. A number of anthraquinone polymers have been examined as the electode‐active materials,62–65 but most of them are π‐conjugated and/or main chain‐type polymers66–70 rather than those containing anthraquinone pendants, resulting in the lower capacities than their theoretical densities and low rate performances due to the limited mass transfer process through the slab of the rigid and crystalline conjugated polymer layers.…”