Isoamyl alcohol, esterification

A few publications dealing with enzymatic conversion using lipases in a chromatographic reactor appeared in the recently literature. Mensah et al. [178] studied the enzymatic esterification of propionic acid and isoamyl alcohol (dissolved in hexane) to produce isoamyl propionate according to the following scheme ... 

Fig. 12. Outlet concentration profiles from a batch chromatographic bioreactor for enzyme catalyzed esterification. Water, which when in the liquid phase irreversibly inhibits the reaction, is adsorbed. The profiles of water (open circle), propionic acid (filled square), isoamyl alcohol (filled triangle) and isoamyl propionate (open square) at the reactor outlet are presented. (Reprinted with permission from [178])...

Methylbutanoates and methylbutyl esters are essential flavour compounds in fruit flavours they can be produced biotechnologically as mentioned before. Chowdary et al. [33] have described the production of a fruit-like flavour isoamyl isovalerate by direct esterification of isoamyl alcohol and isovaleric acid in hexane with the help of Mucor miehei lipase immobilised on a weak anion-exchange resin. 

Iso-amyl acetate has been obtained in this way from isoamyl alcohol and acetyl chloride. The method does not offer any advantages over the more usual esterification reactions. 

Mensah et al. (1998) Batch Esterification of proionic acid with isoamyl alcohol Lipozyme IM... 

Mensah et al. studied the esterification of propionic acid (P) and isoamyl alcohol (A) to isoamyl propionate and water in the presence of the lipase enzyme [P. Mensah, J. L. Gainer, and G. Carta, Biotechnol. Bioeng., 60 (1998) 434.] The product ester has a pleasant fruity aroma and is used in perfumery and cosmetics. This enzyme-catalyzed reaction is shown below ... 

Initial rate data for esterification of propionic acid and isoamyl alcohol in hexane with Lipozyme-IM (immobilized lipase) at 24°C. 

The esterification was carried out in a glass batch reactor at atmospheric pressure. Isoamyl alcohol (0.058 mol) and acetic acid (0.058 mol) were dissolved in toluene (0.114 mol). Then, the TPA-PVA-PEG catalyst (0.100 g) was added and the resulting mixture was heated to reflux. The reaction was followed by gas chromatography, using a thermal conductivity detector. Also, hydrochloric acid was used as catalyst for comparative purpose. 

The catalytic activity of TPA-PVA-PEG catalyst for the esterification of acetic acid with isoamyl alcohol is presented in Table 1. A high selectivity to the ester was obtained, although traces of 3-methyl-1-butene, 2-methyl-1-butene, and isovaleric aldehyde were... 

A new TPA supported catalyst was obtained, which proved to give a high yield and selectivity in the preparation of isoamyl acetate by means of the liquid-phase catalytic esterification of isoamyl alcohol and acetic acid. 

Different characterization techniques were used to evaluate the immobilization and acidic properties of Keggin structured tungstophosphoric and molybdophosphoric acids impregnated on an amine-functionalized SiMCM-41 support. The characteristics of prepared catalysts were correlated to the activity in the esterification of acetic acid with isoamyl alcohol to obtain isoamyl acetate. 

The MPA and TPA based catalysts supported on a new amine-functionalized SiMCM-41 carrier showed important activity in the esterification reaction of acetic acid with isoamyl alcohol. On the other hand, low TPA (MPA) solubility during the leaching was observed. Then, these catalysts are very attractive for their use in liquid medium reactions. 

The batch synthesis data [Geladi Forsstrom 2002] is concerned with the production of isoamyl acetate by an esterification from isoamyl alcohol and acetic acid in a boiling reaction mixture. An acid catalyst is needed and paratoluenesulphonic acid is used. Water is removed by azeotropic distillation with benzene for moving the equilibrium towards the... 

Mandelic Acid Isoamyl Ester, a-Hydroxybenzene-acetic acid 3-methylbutyl ester mandelic acid isopentyl ester isoamyl mandelate Atractyl Spasmol Mandaverm Vermi-parin Spasmostenyl. C,jH,Oj mol wt 222.27. C 70.24%, H 8.16%, O 21.59%. Prepd by esterification of dl-mandelic acid with an excess of isoamyl alcohol in the presence of coned H]SO( Rona et al, Biochem. Z. 181, 50 (1927). Improved procedure Brock et al, Arzneimittel-Forsch. 2, 166 (1952). 

Castanheiro J E, Ramos A M, Fonseca IM and Vital J (2006), Esterification of acetic add by isoamylic alcohol over catalytic membranes of poly(vinyl alcohol) containing sulfonic add groups , AppZ Catal A-Gen, 311,17-23. 

Promising results have been reported on the use of lipase with SC-CO2 in the production of biodiesel from vegetable oils and animal fats. Kumar et al. (2004) esterilied palmitic acid with ethanol at a temperature range of 35°C to 70°C in the presence of three different lipases under SC-CO2 conditions. Their results showed that Novozym 435 was the best catalyst with a yield of 74%. Romero et al. (2005) made similar observations on the esterification of isoamyl alcohol in SC-CO2 and n-hexane, where these showed higher reaction rates in SC-CO2. Higher yields were also reported using SC-CO2, as compared to n-hexane and solvent-free systems (Laudani et al., 2007) using Lipozyme RMIM. 

Another demonstration of a continuous flow operation is the psi-shaped microreactor that was used for lipase-catalyzed synthesis of isoamyl acetate in the 1-butyl-3-methylpyridinium dicyanamide/n-heptane two-phase system [144]. The chosen solvent system with dissolved Candida antarctica lipase B, which was attached to the ionic liquid/n-heptane interfacial area because of its amphiphilic properties, was shown to be highly efficient and enabled simultaneous esterification and product removal. The system allowed for simultaneous esterification and product recovery showed a threefold reaction rate increase when compared to the conventional batch. This was mainly a consequence of efficient reaction-diffusion dynamics in the microchannel system, where the developed flow pattern comprising intense emulsification provided a large interfacial area for the reaction and simultaneous product extraction. Another lipase-catalyzed isoamyl acetate synthesis in a continuously operated pressure-driven microreactor was reported by the same authors [145]. The esterification of isoamyl alcohol and acetic acid occurred at the interface between n-hexane and an aqueous phase with dissolved lipase B from Candida antarctica. Controlling flow rates of both phases reestablished a parallel laminar flow with liquid-liquid boundary in the middle of the microchannel and a separation of phases was achieved at the y-shaped exit of the microreactor (Figure 10.25). The microreactor approach demonstrated 35% conversion at residence time 36.5 s at 45 °C and at 0.5 M acetic acid and isoamyl alcohol inlet concentrations and has proven more effective and outperformed the batch operation, which could be attributed to the favorable mass and heat transfer characteristics. 

The recovery of acetic acid from its dilute aqueous solutions is a major problem in both petrochemical and fine chemical industries. Saha, et al. (2000) developed conventional methods of recovery of 30% acetic acid by reaction with n-butanol and isoamyl alcohol in a reactive distillation column using macroporous ion-exchange resin, Indion 30, as a catalyst bed, confined in stainless steel wire cages. They found that recovery of acetic acid was enhanced by reactive distillation compared to the batch operation. Hanika et al. (1999) studied the esterification butyl alcohol with acetic acid in a pilot plant using a reactive distillation column packed with commercial catalysts (KATPAK and CY). It was found that butyl acetate could be recovered in very high purity. This study had resulted in the development of a new technology for the manufacture of butylacetate. 

About 69% of the total 1988 U.S. consumption of isobutyraldehyde, went into the production of isobutyl alcohol and isobutyraldehyde condensation and esterification products. The other principal isobutyraldehyde derivative markets (as a percentage of total 1988 U.S. isobutyraldehyde consumption) are neopentyl glycol (15%) isobutyl acetate (6%) isobutyric acid (5%) isobutyUdene diurea (2.5%) and methyl isoamyl ketone (1.7%). 

Many acetate esters (such as those of isoamyl, benzyl, citroneUyl, and geranyl alcohols) are components of natural flavors. They can be obtained by Upase-cata-lyzed esteriflcation in organic solvents, but the major problem with enzymatic acetylations is deactivation of lipases by acetic acid [8, 9]. Most of the Upase-catalyzed syntheses of esters have been carried out by transesterification to avoid free acid toxicity and water formation. Claon and Akoh [10] found that immobilized lipases from Candida antarctica promote highly effective direct esterification of geraniol and citronellol with acetic acid. 

The residue of methyl esters (e.g. from esterification according to procedure 2.1.1 above) is treated with 200 pi of methylene chloride, which is evaporated off to entrain any traces of water. Transesterification is with 100 pi of 1.25 M HCl in isobutyl alcohol at 110 °C for 150 minutes [143]. An essentially similar procedure for making isoamyl esters has also been described [144]. The similar method of transbutylation developed by the Missouri group [145] has been replaced by the direct butyl esterification procedure [146, 147]. 

Other esters present in high concentrations in alcohohc beverages include isoamyl acetate and isobutyl acetate (8-79) that arise, as well as ethyl acetate, by alcoholysis of acetyl-CoA through the respective alcohols. Isobutyric and isovaleric adds yield virtually no esters in beer and wine, as the non-enzymatic esterification is too slow and the equiKbrium is shifted to the detriment of esters. In spirits, these esters occur at levels up to units of mg/1. 

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