Water lauric acid esterification

This section deals with the conceptual design of a catalytic distillation process for the esterification of lauric acid (LA) with 2-ethyl-hexanol (2EtH). Laboratory experiments showed that a superacid sulfated zirconia catalyst exhibits good activity over a large interval, from 130 to 180 °C with no ether formation. On the contrary, the catalyst is sensitive to the presence of free liquid water. Raw materials are lauric acid and 2-ethylhexyl alcohol of high purity. The conversion should be over 99.9%, because the product is aimed at cosmetic applications. 

In the following, the strategy presented before will this time be applied for developing a process for the esterification of lauric acid with methanol. All the thermodynamic data for pure components and binary mixtures are available in Aspen Plus. A residue curve map of the reactive mixture at equilibrium can be computed as described in Appendix A. A useful representation can be done in reduced coordinates defined by Xx = water + add and X2 = add + ester. The diagram displayed... 

Figure 13.3 shows the profiles of the DBSA-catalysed reaction of lauric acid with 3-phenyl-1-propanol (1 1) at 40°C in water (closed circle). The reaction reached its maximum yield of 84% in 170 hours. We also conducted hydrolysis of the corresponding ester (open square). Both esterification and hydrolysis finally led to the same composition of the reaction mixture, indicating that the reaction reached its equilibrium position. 

FIGURE 13.3. Reaction profiles for DBSA-catalysed reactions in water. Closed circle esterification of lauric acid with 3-phenyl-l-propanol (1 1). Open square hydrolysis of 3-phenyl-1-propyl lauratc. 

We next carried out selective esterification of two substrates in this reaction system. When a 1 1 mixture of lauric acid and acetic acid was esterified with dodecanol in the presence of DBSA under neat conditions at 40°C for 48 h, the laurate ester and the acetate ester were obtained in 63% and 35% yields, respectively (Table 13.7, entry 1). On the other hand, when the same reaction was conducted in water, the laurate ester was predominantly obtained in 81% yield, and the yield of the acetate was only 4% (entry 2). Similar selective esterification of lauric acid over acetic acid was also observed in the reaction of another alcohol (entry 4), Furthermore, even cyclohex-anecarboxylic acid, which is an a-disubstituted acid, was preferentially esterified in the presence of acetic acid (entries 5 and 6). These selectivities are attributed to the hydrophobic nature of lauric acid and cyclohexanecarboxylic acid as well as to the high hydrophilicity of acetic acid. These unique selectivities became possible by using water as a solvent. Selective esterification based on the difference in hydrophobicity was also attained in the reaction of two alcohols, one of which is hydrophobic and the other water-soluble. 

Lipase-catalyzed esterification of fatty acids with alcohols [oleic acid + ethanol (141, 152, 163, 169, 178, 195-197), oleic acid + oleyl alcohol (144, 179, 198-200), lauric acid + butanol (142), myristic acid + ethanol (138, 139, 143, 201), stearic acid + ethanol (202), anhydrous milkfat fatty acids + ethanol (197)] in SCCO2 has been widely studied to understand the kinetics/mechanism of the reaction and to determine the effect of operating conditions, substrate concentration, and water content on enzyme activity. Alternative catalysts such as p-toluenesulfonic... 

Kulkarni, M. G. S. B. Sawant (2003) Kinetics of the catalytic esterification of castor oil with lauric acid using n-butyl benzene as a water entrainer. Journal of the American Oil Chemists Society, 80,1033-1038, ISSN 0003-021X. 

Table 3.6 and Scheme 3.31, in the model reaction of lauric acid with 3-phenyl-1-propanol, commercially available DOWEX 500W-X2 (H+-form, 9) did not promote esterification. The result indicates that a highly hydrophobic nature of the polymer-supported catalysts is important for activity in the dehydration reaction in water. It was found that resin 9 swelled significantly in water due to its high sulfonic acid content. On the other hand, both 11 and 12 scarcely swelled in water but worked as efficient catalysts. Resin 11 was easily recovered by simple filtration after the esterification was complete, and the catalyst could be continuously reused at least four times without loss of catalytic activity (Scheme 3.32). 

In another recent paper (Sawae et al., 2005), polyethylene glycol microspheres were prepared using an oil-in-water-in-oil double-emulsification method to encapsulate lipase complexes. The PEG microspheres exhibited heat-resistant properties that are advantageous when compared with the lipase complex itself dissolved in organic solvent. It was found that PEG microspheres retained high enantioselectivity in the esterification of phenyl ethyl alcohol and lauric acid in isooctane. The immobilized lipase complexes in the PEG microspheres can be easily recovered, and their activity remained preserved up to 10 reuses. 

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