Catalysts fatty-ester synthesis

Further improvement in the technology of methyl fatty ester synthesis can be achieved by dual esterification [4], This takes advantage of the fact that the sulfated zirconia catalyst has similar activity for normal alcohols, over the series C1-C8. However, methanol manifests about twice the activity [20], The removal of water produced by the esterification with methanol is solved simply, by employing a heavy alcohol immiscible with water, such as 2-ethyl-hexanol, which acts simultaneously as a reactant and an entrainer. As a result, the two fatty esters are obtained in the bottom product in the desired ratio by adjusting the feeds. For example, in a preferable operation mode the ratio of fresh feed reactants is acid methanol 2-ethyl-hexanol 1 0.8 0.2. 

Among the aldonolactone-based surfactants are aldonolactone-linked fatty esters which have been prepared by selective acylation of unprotected aldono-1,4-lac-tones or aldono-1,5-lactones, One of the first reported examples of this type of surfactant was applied to the enzymatic synthesis of 6-0-aUcanoylgluconolactones [35], Thus, 6-0-decanoyl- and 6-0-dodecanoyl- derivatives (21a and 21b, respectively, Scheme 8) were obtained in 26-27% yield by esterification of glucono-1,5-lactone (1) at C-6 with the corresponding 2,2,2-trichloroethyl carboxylate in the presence of porcine pancreatic lipase (PPL) as catalyst. Compounds 21a,b are soluble in water at 90-96°C but precipitate when cooled to 30-37°C, NMR and GC-MS analysis after dissolution and precipitation indicated the presence in the mixture of compound 21b, the glucono-1,4-lactone-derived ester 22, and the... 

Chemical esterification methods use an alcohol and a carboxylic acid in the presence of a mineral acid as catalyst. Sulfuric acid, which is commonly used, leads to the formation of undesirable byproducts, requiring a difficult separation step (3). Moreover, in this case, the starting material is a high-value component (fatty acid). Consequently, researchers are interested in the alcoholysis reaction using a vegetable oil with low cost and largely produced in Brazil as a raw material for ester synthesis. 

The temperature optimum for interesterification is 85°C or higher, and the half-life in continuous acidolysis of spy bean oil with lauric acid at 60°C is above 2500 h. The non-specificity makes the catalyst useful in random interesterification of different fats. The catalyst has some saturated fatty acid specificity. Two lipase components (A and B) were purified. Lipase A is important for interesterification, and Lipase B is important in ester synthesis. 

When, however, the hydrogen concentration is sufficiently high during amination, the amine or the alcohol reactant can be substituted by the corresponding nitriles, or acids and esters, respectively. The useful intermediate fatty amines were synthesized starting from fatty acids (or esters) and ammonia, and long-chain nitriles instead of amines were used with Cu- and Ni-containing catalysts for the synthesis of N-alkylated amines [15]. 

Mazzocchia, C. G. Modica A. Kaddouri R. Nannicini. Fatty acid methyl esters synthesis from triglycerides over heterogeneous catalysts in the presence of microwaves. C.R Chimie 2004, 7, 601-605. 

Marquez-Alvarez C., Sastre E., Perez-Pariente J., Solid catalysts for the synthesis of fatty esters of glycerol, polyglycerols and sorbitol from renewable resources, Top. Catal., 27(1 ), 2004, 105-117. 

Up to early 1990s, it was assumed that oxyethylation can occur only when the hydrophobic reagent had a labile hydrogen [1-3,5]. Thus, fatty acid methyl esters (FAME) were not considered as a raw material for the direct synthesis of nonionic surfactants with a polyoxyethylene chain. However, esters of fatty acids and PEG monomethyl ethers were known and their properties were described [6]. They were synthesized in a two-step process. Methanol was oxyethylated to PEG monomethyl ether that was then converted into the final product by transesterification with FAME or by esterification with fatty acids, carried out in the presence of an alkaline B or an acid catalyst, respectively. Esters of typical nonionics were synthesized in similar ways and their properties were described [7-9]. 

Synthesis was carried out on a laboratory (up to 500g) scale by transesterifying sucrose at 90° - 100°C and 30 mm under nitrogen with three to five molar proportions of methyl fatty esters (acid value preferably less than 1 mg KOH/g) in dimethylsulphoxide (DMSO) (about 30 - 35% of the total reactants) and about 0.5 to preferably not greater than 2% dry weight of anhydrous potassium carbonate on the weight of methyl esters. Low amounts of catalyst and low acid values reduce contamination of the product with potassium soap. 

Li Y, Zhang X, Sun L, Zhang J, Xu H. Fatty add methyl ester synthesis catalyzed by solid superacid catalyst S0/ /Zr02-Ti02/La. Appl. Energy 2010 87 156. 

Lipase-catalysed interesterification has found many applications in production of edible and specialty lipids due to mild reaction conditions, high catalytic efficiency, the inherent selectivity of natural catalysts and production of much purer products as compared to chemical methods (Sonnet, 1988). Lipases (hydrolases) are used for hydrolysis and ester synthesis. They are classified as non-specific or random, positional specific or 1,3-specific and acyl group- or structure-specific, depending on their activity towards fatty acids... 

Ropuszynski, S. and Sczesna, E. (1985) The effect of catalysts on the synthesis of fatty acid esters of anhydrosorbitols (Spans). Tenside Deterg., 22, 190-192. 

Efficient enzymatic conversion can be achieved even though most of the reactants are present as solids, provided that there is a liquid phase in which the reaction can occur. This approach has been successfully used for carbohydrate ester synthesis with synthesis of glucose esters of fatty acids between C12 and C18 as typical examples [34]. It is important that the substrates dissolve during the reaction, and often the products precipitate as they are formed, which can be an advantage due to a favourable effect on the equilibrium position. Candida antarctica lipase B is an efficient catalyst in this system and solvents used (in moderate amounts) include ethyl methyl ketone, acetone or dioxane. In order to increase the ester yield, water formed in the reaction can be removed by azeotropic distillation and the solvent (e.g. ethyl metyl ketone) can after condensation be dried by pervaporation, giving a practically useful complete process [35]. 

In the lubricant sector, oleochemically-based fatty acid esters have proved to be powerful alternatives to conventional mineral oil products. For home and personal care applications a wide range of products, such as surfactants, emulsifiers, emollients and waxes, based on vegetable oil derivatives have proved to provide extraordinary performance benefits to the end-customer. Selected products, such as the anionic surfactant fatty alcohol sulfate, have been investigated thoroughly with regard to their environmental impact compared with petrochemical based products by life-cycle-analysis. Other product examples include carbohydrate-based surfactants as well as oleochemical based emulsifiers, waxes and emollients. The catalysts used in the synthesis of these molecules need further development. 

Esters are common components in cosmetics and skin-care products. They can be synthesized from fatty acids and alcohols using either chemical or enzymatic reactions. The chemical reactions are normally catalysed by acid catalysts. Enzymatic synthesis is carried out under milder conditions and therefore it provides products of very high purity. A range of esters such as isopropyl palmitate and isopropyl myristate are now produced industrially using enzymatic synthesis. The reactions are carried out in solvent-free systems using an immobilised lipase as catalyst. In order to get high yields in the reactions, water is removed continuously. 

Also, bulky phosphite-modified rhodium catalysts are highly reactive for the hydroformylation of unsaturated fatty acid esters [23]. The catalyst was able to yield turnover numbers (TON) of 400-500 when moderate conditions with 20 bar synthesis gas pressure and 100°C were applied. These phosphites, like tris (2-ferf-butyl-methyl) phosphite, have higher activity than phosphines like triphenylphosphine. 

Fell et al. presented a micellar two-phase system in which fatty acid esters can be hydroformylated [30]. Short fatty acids react in a mixture of water and the substrate without adding any surfactants. The rhodium/NaTPPTS catalyst system was able to conduct the reaction of methyl 10-undecenoate at 100°C with 30-bar synthesis gas pressure with a conversion of 99% without any surfactant. The reaction of linolenic acid ester was hindered by phase transfer problems which could be overcome by employing surfactants. The addition decreased the reaction time, so the same rhodium catalyst could achieve a conversion for linolenic methyl ester of 100%. The authors... 

Supercritical fluid carbon dioxide (SC-CO2) fractionation of fish oil ethyl esters (EE) was employed to prepare EE of two omega-3 fatty acids, all cis-5,8,11,14, 17-eicosapentaenoic acid (EPA) and all cis-4,7,10,13, 16,19-docosahexaenoic acid (DHA) in 90% purity and to separate the synthetic triacylglycerols (TG), trieicosapentaenoylglycerol (tri-EPA), and tridocosahexaenoyl-glycerol (tri-DHA) in > 92% purity from other reaction mixture components. In the synthesis, glycerine reacted with EE and sodium glyceroxide catalyst to form TG. 

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