Tsunetake Seki

Catalytic oxidations in dense carbon dioxide.

3.3. Other Heterogeneous Catalysts 2428 3.3.1. Chromium-Containing Molecular Sieves 2428 3.3.2. Supported Gold 2428 3.3.3. Supported Multi-Metals 2429 3.3.4. Supported Iron Oxide 2429 3.3.5. Polyoxometalate 2429 3.4. Enzyme Catalysis 2431 3.5. Photocatalytic Oxidations 2431 4. Aerobic Oxidation of Phenols 2432 4.1. Cobalt Complex Catalysts 2432 4.2. Enzyme Catalysis 2434 5. Oxidation of Alkenes 2434 5.1. Metal Complex Catalysts 2434 5.1.1. Molybdenum-Based Catalysts 2434 5.1.2. Vanadiumand Titanium-Based Catalysts 2436 5.1.3. Palladium(II) Chloride 2436 5.1.4. Iron-Based Catalysts 2438 5.1.5. Manganese-Based Catalysts 2440 5.2. Supported Metal Catalysts 2440 5.2.1. Catalytically Active Wall of a Stainless-Steel Reactor 2440

Continuous catalytic “one-pot” multi-step synthesis of 2-ethylhexanal from crotonaldehyde

2-ethylhexanal is synthesized directly from crotonaldehyde over a bifunctional acidic resin-supported palladium catalyst via hydrogenation and aldol condensation in supercritical CO2.

Amorphous nano-structured silicas for high-performance carbon dioxide confinement

The amorphous silica prepared using a precipitation method served as a highly efficient CO2 adsorbent, combined with the favorable mass-transfer properties of supercritical CO2. The CO2-capture occurred by the unique pore structure of the silica.

Tracing the acetalization of cyclohexanone in CO2-expanded alcohols by attenuated total reflection infrared spectroscopy.

The CO2-catalyzed acetalization is regarded as a promising alternative to the conventional acid-catalyzed method from a viewpoint of green chemistry (C. A. Eckert et al., Ind. Eng. Chem. Res. 43, 2605 (2004)). We have applied in situ attenuated total reflection infrared (ATR-IR) spectroscopy for elucidating and monitoring the acetalization of cyclohexanone in CO2-expanded ethylene glycol and methanol at 50 °C and 3 MPa. The ATR-IR spectra of the reaction mixtures periodically recorded with a ZnSe crystal demonstrate that ATR-IR spectroscopy is a practical tool for tracing the kinetics of acetalizations in situ. In addition, the rate of CO2 dissolution as well as CO2 solubility into the cyclohexanone–alcohol mixtures could be evaluated from the CO2-v3-antisymmetric stretching band. The ZnSe ATR crystal, however, was corroded during longer use under the acidic conditions realized by the dissolution of CO2 in the alcohols. In contrast, the corrosion did not occur when a Ge crystal was used instead of a ZnSe crystal, and therefore the application of a Ge ATR crystal is recommended for continuous long-term experiments with these media.