Selective Catalytic Hydrogenation of Organic Compounds in Supercritical Fluids as a Continuous Process

Abstract

We report a new method for continuous hydrogenation in supercritical fluids (CO 2 or propane) using heterogeneous noble metal catalysts on Deloxan aminopolysiloxane supports. The method has considerable promise both for laboratory-scale hydrogenation and for the industrial production of fine chemicals. It can be applied to a wide range of organic compounds including alkenes, alkynes, aliphatic and aromatic ketones and aldehydes, epoxides, phenols, oximes, nitrobenzenes, Schiff bases, and nitriles. Conversion of starting materials, product selectivity, and space-time yields of the catalyst are all high, and the reactors themselves are very small (5-and 10-mL volume). Supercritical hydrogenation enables the reaction parameters to be controlled very precisely. Results are presented for a series of different reactions showing product distributions, which are dependent on temperature, pressure, H 2 concentration, and the loading and nature of the catalyst. The hydrogenation of cyclohexene has been studied in some detail, and our results are related to the phase diagrams of the ternary system cyclohexane + CO 2 + H 2 , which we present in a novel way, more suited to continuous reactors. Finally, we report that the supercritical hydrogenation of isophorone has advantages over conventional methods.

A Review of CO2 Capture by Absorption and Adsorption

“…Besides, propane can be completely removed from solid support after pressure releasing. The use of SC-propane as the solvent for various applications is existing in the literation, for example, Hitzler et al (1998) successfully carried out hydrogenation of nitrogencontaining compounds in SC-propane. De Gooijer et al (1999) successfully used near critical propane as the solvent for impregnation of 1,4-diaminobutane into the maleic anhydride grafted polyethylene.…”

Atom efficiency and catalysis in organic synthesis

“…The use of supercritical carbon dioxide as a solvent for catalytic conversions, (e.g., hydrogenation) is also gaining in importance [49]. Interestingly, the use of perfluorinated ligands, developed for fluorous biphasic systems, also promotes the solubility of metal complexes in supercritical carbon dioxide [50].…”

Effects of Ultrasound and Microwaves on Selective Reduction: Catalyst Preparation and Reactions

“…al. [146] reported a method that combines supercritical fluids and continuous flow reactors. They were able to hydrogenate isophorone (at flow rates up to 2.0 mL/min at 120 bar in scCO2 (0.75 L/min) over the 5% Pd APII Deloxan catalyst) achieving quantitative conversion with high selectivity.…”