Heterogeneous Catalysis for Fine Chemicals in Dense Phase Carbon Dioxide

Abstract

An increasing number of fine chemicals is\ud being produced using heterogeneously catalysed reactions\ud in supercritical carbon dioxide with significant\ud improvements in terms of process selectivity\ud and purity of the products thereby obtained. A selection\ud of examples and of recent findings shows the\ud large potential of this technology for the synthetic\ud chemistry of the future

High Activity in Catalytic Oxidation of Benzyl Alcohol with Molecular Oxygen over Carboxylic-Functionalized Carbon Nanofiber-Supported Ruthenium Catalysts

“…Notably, CNF-supported ruthenium catalysts have high catalytic activities. Particlularly, Ru/CNF200 catalyst gave very high activity at 70.9% (Run 4), which is comparative with that of TPAP/c-Al 2 O 3 (72.1%, Run 12) and TPAP/SiO 2 (68.6%, Run 13) [46,47]. Interestingly, the sample activities remarkably decreased with increasing temperatures for the treatment of Ru/ CNF200 catalyst.…”

Oxidation of Alcohols with Molecular Oxygen

“…The organically modified silica, prepared by copolymerization of tetramethoxysilane and methyltrimethoxysilane, contained pores of less than 1.5 nm diameter that prevented leaching of the active species. A high fraction of surface alkyl groups provided the necessary hydrophobic character and good activity in the oxidation of benzyl alcohol (TOF up to 63 h −1 ) [196]. Interestingly, the TPAP-doped organically modified silica was more active and stable than TPAP dissolved in organic solvents.…”

Aerobic oxidations in flow: opportunities for the fine chemicals and pharmaceuticals industries

“…3. Ionic liquids (ILE's) 105,106 and CO 2 , [107][108][109] have been employed in aerobic oxidation reactions, in order to circumvent the need for flammable solvents. However, the use of such unconventional reaction media may require specialised equipment to contain sc-CO 2 and to recycle ILE, which may be too energy-intensive.…”