Liquid/supercritical carbon

Natural Products. Various methods have been and continue to be employed to obtain useful materials from various parts of plants. Essences from plants are obtained by distillation (often with steam), direct expression (pressing), collection of exudates, enfleurage (extraction with fats or oils), and solvent extraction. Solvents used include typical chemical solvents such as alcohols and hydrocarbons. Liquid (supercritical) carbon dioxide has come into commercial use in the 1990s as an extractant to produce perfume materials. The principal forms of natural perfume ingredients are defined as follows the methods used to prepare them are described in somewhat general terms because they vary for each product and suppHer. This is a part of the industry that is governed as much by art as by science. 

J. A. Laszlo, D. L. Compton, Chymotrypsin-catalyzed transestrification in ionic liquids and ionic liquid/ supercritical carbon dioxide. In Ionic Liquids, R. D. Rogers, K. R. Seddon, Eds., ACS Symposium Series Vol. 

Reetz, M.T., W. Wiesenhofer, G. Francio and W. Leitner, Continuous Flow Enzymatic Kinetic Resolution and Enantiomer Separation Using Ionic Liquid/Supercritical Carbon Dioxide Media, Advanced Synthesis Catalysis, 345, 1221-1228 (2003). 

In biphasic reactors or two-phase partitioning bioreactors (TPPB), the substrate is located mostly in the immiscible phase and diffuses to the aqueous phase. The enzyme catalyzes conversion of the substrate at the interface and/or in the aqueous phase. The product/s of the reaction then may partition to the organic phase. The system is self-regulated, as the substrate delivery to the aqueous phase is only directed by the partitioning ratio between the two phases and the enzymatic reaction rate [53]. The use of ionic liquid/supercritical carbon dioxide for enzyme-catalyzed transformation is gaining attention [69]. 

Hernandez FJ, de los Rios AP, Gomez D, Rubio M, ViUora G. A new recirculating enzymatic membrane reactor for ester synthesis in ionic liquid/supercritical carbon dioxide biphasic systems. Appl Catal B 2006 67 121-126. 

Ionic Liquids/Supercritical Carbon Dioxide as Advantageous Biphasic Systems in Enzymatic Synthesis... 

Ionic liquids/supercritical carbon dioxide (ILs/scCOj) biphasic systems have recently been considered as interesting clean alternatives to classical organic... 

In order to optimize and/or improve the behaviour of bioprocesses in ionic liquids/supercritical carbon dioxide biphasic systems, a better understanding of the chemical reaction and mass-transfer phenomena in these biphasic systans is required. In this context, de los Rfos et al. [38] analysed the chemical reaction and the mass-transfer phenomena in the synthesis of bntyl propionate from vinyl propionate and 1-butanol catalysed by CaLB immobilized on dynamic monbranes at... 

Fig. 8.4 Initial reaction rate (bars) and selectivity (points) exhibited by free Candida antarctica lipase B for butyl propionate synthesis in supercritical carbon dioxide and in four different ionic liquids/supercritical carbon dioxide systems. The reaction conditions were r=50°C, vinyl propionate 150 mM and 1-butanol 100 Mm [38]...

Lozano P, De Diego T, Gmouh S et al (2004) Criteria to design green enzymatic processes in ionic liquid/supercritical carbon dioxide systems. Biotechnol Prog 20 661-669... 

Chapter 8 focuses on the properties of ionic liquids/supercritical carbon dioxide biphasic systems for enzymatic applications. 

Other biphasic C—C bonding reactions were carried out with fluorous solvents, for instance Suzuki- and Sonogashira-couplings [124] or ethene or propene oligomerizations [125, 126], Further new solvent systems use ionic liquids for the linear dimerisation of 1-butene to octenes [127] or the hydrovinylation of styrene with a combination ionic liquid/supercritical carbon dioxide [128] (cf. Section 7.4). 

Forbes and Yashiro studied the addition of the initiating radials to methyl methacrylate in liquid supercritical carbon dioxide [58]. They demonstrated that the rate of addition of the initiating radicals to the monomers, kadd values, can be measured in liquid CO2. 

Fan, Y., and J. Qian. 2010. Lipase Catalysis in Ionic Liquids/Supercritical Carbon Dioxide and Its Applications. Journal of Molecular Catalysis B Enzymatic 66 (1—2) 1—7. 

Hernandez, F. J., A. P. de los Rfos, D. Gomez, M. Rubio, and G. Vfllora. 2006. A New Recirculating Enzymatic Membrane Reactor for Ester Synthesis in Ionic Liquid/ Supercritical Carbon Dioxide Biphasic Systems. Applied Catalysis B Environmental Cl (1-2) 121-126. 

Acid zeolites have also been tested for the racemisation of alcohols under biphasic conditions.Their scope was found, however, to be limited to benzylic alcohols, since electron-rich benzylic alcohols were not suitable substrates because of the formation of dimers. Under optimised conditions, based on the use of H-Beta zeolite, CALB lipase, and an excess of vinyl octanoate at 60 °C, enantiopure (R)-l-phenylethyl octanoate (>99% ee) was obtained in 90% yield from 1-phenylethanol. In addition, Lozano et al. have recently performed the DKR of this alcohol in the presence of acidic zeolite catalysts (CBV400) in an ionic liquid-supercritical carbon dioxide system with a continuous reaction system. Therefore, when Novozym 435 was employed at 50 °C and 100 bars in the presence of vinylpropanoate as the acyl donor, the expected (R)-phenylethylpropionate was produced in excellent yield of 98% with enantioselectivity of 97% ee and without any activity loss during 14 days of operation. 

P. Lozano,. M. Bernal, M. Vaultier, Towards continuous sustainable processes for enzymatic synthesis of biodiesel in hydrophobic ionic liquids/supercritical carbon dioxide biphasic systems, Fuel 90 (2011) 3461-3467. 

Ballivet-Tkatchenko D, Picquet M, Solinas M, Frando G, Wasserscheid P, Leitner W (2003) Acrylate dimerisation under ionic liquid-supercritical carbon dioxide conditions. Green Chem, 5,232-235. 

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