Fatty acid esterification

The pore size of the catalyst plays an important role as the reactants and the products must be able to lit inside the catalyst to take full advantage of the total surface area available. The pore size of metal oxides are sufficiently large (>2 nm) to facihtate the mass transfer into and from the catalyst pores. This compensates for their lower acidity compared to other sohd acids. Table 33.1 gives an overview of the tested catalysts, showing their pros/cons with respect to the fatty acid esterification reaction. 

Calu-3 cells have shown the ability to perform fatty acid esterification of budes-onide [132], In pre-clinical studies, this esterification results in a prolonged local tissue binding and efficacy, which is not found when the esterification is inhibited [133]. The precise mechanism remains undefined in that the identity of specific enzyme(s) responsible for this metabolic reaction is unclear [134], Assessment of the potential toxicity and metabolism of pharmaceuticals and other xenobiotics using in vitro respiratory models is still at its infancy. The development of robust in vitro human models (i.e., cell lines from human pulmonary origin) has the potential to contribute significantly to better understanding the role of biotransformation enzymes in the bioactivation/detoxication processes in the lung. 

Figure 16.3 Effects of insulin on the glucose/fatty acid cycle. Insulin enhances glucose metabolism by stimulating glucose uptake by muscle and adipose tissue and by inhibiting lipolysis in adipose tissue (see Chapter 12 for the mechanism of these effects). The effect of glucose metabolism on lipolysis is via stimulation of fatty acid esterification via glycerol 3-phosphate.

The benefits of using biodiesel as renewable fuel and the difficulties associated with its manufacturing are outlined. The synthesis via fatty acid esterification using solid acid catalysts is investigated. The major challenge is finding a suitable catalyst that is active, selective, water-tolerant and stable under the process conditions. The most promising candidates are sulfated metal oxides that can be used to develop a sustainable esterification process based on continuous catalytic reactive distillation. 

Marty, A. Combes, D. Condoret, J. S. Fatty Acid Esterification in Supercritical Carbon Dioxide. In Biocatalysis in Non-Con vent ional Media Tramper, J. Vermiie, M. H. Beeftink, H. H., Eds. Elsevier Science Amsterdam, 1992a pp. 425-432. 

Figure 4.34 In fatty acid esterification, the catalyst surface hydrophobicity is a key factor. Too few acid sites result in low activity, but too many lead to water adsorption and deactivation.

Omota, F., Dimian, A.C. and Bliek, A. (2003) Fatty acid esterification by reactive... 

Figure 8.16 Conceptual residue curve map forentrainer selection in fatty acid esterification.

Omota, F., Dimian, A. C., Bliek, A., Fatty-acid esterification by reactive distillation, Part 2 kinetic-based design for sulfated zirconia catalyst, Chem. Eng. Science, 58, 3175-3185, 2003... 

Santacesaria, E., Tesser, R., Di Serio, M., Guida, M., Gaetano, D., Garcia Agreda, A. 2007. Kinetics and mass transfer of free fatty acids esterification with methanol in a tubular packed bed reactor a key pretreatment in biodiesel production. Ind. Eng. Chem. Res., 46, 5113-5121. 

Figure 6 shows the Henkel continuous process of fatty acid esterification. The reaction is carried out at a pressure of approximately 1000 kPa and a temperature of 240°C. One advantage of this process is the excess methanol can be kept significantly lower at 1.5 1 molar ratio of methanohfatty acid versus the batch process at 3—. 1 molar ratio. The methyl ester, having undergone distillation, does not require further refining. The excess methanol is rectified and reused (15). 

Zhang, X. and Hayes, D. G., Improvement of the rate and extent of hpase-catalyzed saccharide-fatty acid esterification by control of reaction medium, J. Am. Oil Chem. Soc., 76, 1495-1500, 1999. 

There is no doubt that in the absence of luminal bile salts there is diminished transport of long-chain fatty acids in intestinal lymph and there is evidence that a greater proportion of absorbed long-chain fatty acid is transported in portal venous blood [81,82]. Such observations have been interpreted to show diminished fatty acid esterification by the enterocyte. A similar re-routing of absorbed vitamin A in the bile-diverted animal from the lymphatic to the portal venous route has also been ascribed to defective esterification [83]. 

Laudani CG, Habulin M, Knez Z et al. (2007) Immobilized lipase-mediated long-chain fatty acid esterification in dense carbon dioxide bench scale packed-bed reactor study. J Supercrit Eluids 41 74-81... 

FAME and other fatty acid methyl esters (FAMEs) are endogenous compounds [2, 56], formed via fatty acid ethyl ester synthase (FAEES) [2]. The fatty acid esterification catalyzes an ojg gen atom from the carboxyl group, then condenses the carboxyl group of an acid and the hydroxyl group of an alcohol. FAME synthesis can also be modulated by exogenous methanol and inhibitors of FAEES [2, 57, 58]. 

High-molecular-weight esters, such as wax esters, steryl esters, triterpenoid esters and triacylglycerols, are often hydrolysed, after which the liberated moieties are GC analysed however, this procedure provides only limited compositional information. The very convenient one-pot small-scale hydrolysis-silylation procedure, applicable to ester-emulsifiers, oils, fats, wax esters and other hydrolysable lipids, has been proposed by the lUPAC (Briischweiler and Hautfeune, 1990). The procedure involves the saponification of esters (ca. 10 mg) in 0.5 N ethanolic KOH solution (0.25 mL) at 80 °C for 3 h, evaporation to dryness in a stream of nitrogen and then silylation of the hydrolysis products. This enables the components of very small samples to be determined (< 0.1 mg). This procedure was used for the hydrolysis of wax esters and triterpenoid esters in potato and eggplant cuticular waxes (Szafranek Synak, 2006 Halinski et al., 2009). A solution of 1-2% (v/v) concentrated sulphuric acid in methanol can be easily used for the transesterification of acyl lipids and the esterification of free fatty acids (Christie, 1994). More procedures for ester hydrolysis and transesterification and for fatty acid esterification are described in detail by Christie (1994). 

Omota F., Dimian A. and Bliek A. (2001). Design of reactive distillation process for fatty acid esterification. Computer-Aided Chemical Engineering 9, 463-M68. 1.2.1... 

Fatty Acid Esterification The most cited fatty acid esterification protocol for GC separation was developed by Sasser, published in a technical note in 1990, and revised in 2001 [44]. Four reagents are used for this procedure ... 

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