生物质制备乙酰丙酸酯类转化路径的研究进展

乙酰丙酸酯类是比较重要的一类平台化合物,具有广泛的应用。本文首先介绍了乙酰丙酸酯类的生物炼制途径,然后综述了目前国内外制备乙酰丙酸酯类的研究现状和最新进展。乙酰丙酸酯类的主要制备方法包括乙酰丙酸合成法、糠醇转化法以及生物质醇解法,并对3种方法的优劣进行说明,指出今后乙酰丙酸酯类的制备方法将以生物质直接醇解法为主。建议着力建立生物质直接醇解法反应过程中的热力学性质等相关数据,并加强与此相关的交叉学科的研究,以构建生物质醇解法制备乙酰丙酸酯类的理论基础。     

In-situ alcoholysis of soybean oil

In-situ alcoholysis of soybean oil with methanol, ethanol,n-propanol, andn-butanol was investigated, as well as the extraction of the oil with these solvents, to explain the progress ofin-situ alcoholysis and to determine the parameters that affect this reaction. Because methanol is a poor solvent for soybean oil, the amount of oil dissolved in methanol and converted to methyl esters was low afterin-situ alcoholysis. Ethyl, propyl, and butyl esters of soybean fatty acids could be obtained in high yields fromin-situ alcoholysis of soybean oil with these alcohols.In-situ alcoholysis proceeded through dissolution and alcoholysis of triglycerides successively, and the overall reaction rate was determined by the extraction and alcoholysis rates. The parameters, affecting yield and purity of the product esters, were mainly those that favor extraction rate.     

Alcoholysis of triacylglycerols by heterogeneous catalysis

Synthesis of fatty acid esters by alcoholysis, especially methanolysis of triacylglycerols was investigated using metal salts of amino acids as catalysts. The methanol to oil molar ratio was 6:1. It could be shown that salts containing a quaternary amino or a highly basic group as e.g. a guanidino group have catalytic activity in alcoholysis. Some of these salts are insoluble in monovalent alcohols, glycerol, and fatty acids esters and are therefore suitable catalysts for heterogeneously catalysed alcoholysis. Zinc salts of arginine, carnitine or histidine are among others suited for industrial use. These catalysts are also suitable for heterogeneously catalysed interesterification.     

Alcoholysis of waste fats with 2‐ethyl‐1‐hexanol using Candida antarctica lipase A in large‐scale tests

Commercial native lipase A from Candida antarctica was used to produce alkyl esters through the alcoholysis of (waste) fats with 2‐ethyl‐1‐hexanol. The process was carried out in batch stirred tank reactors (from 100 mL up to 3000 L). The content of alkyl esters in reaction mixtures was determined by gradient HPLC using an evaporative light scattering detector and the reaction progress was controlled by determining the ratio of the palmitic acid ester peak area to the oleic acid ester peak area in HPLC chromatograms. The results show that alcoholysis is the favoured reaction in presence of excess water and water‐insoluble alcohols in comparison with hydrolysis (fatty acid content <5%). The optimum amount of water for the alcoholysis was found to be 80–100% of the amount of fat. In the presence of low quantities of water both alcoholysis and hydrolysis are slow. Conversion rate increases with increasing temperature to 65–70 °C. Based on these results a large‐scale test to produce 3000 L of alkyl ester (to be used as lubricant coolant) was carried out. The experiments have proved that alcoholysis is completed after about 7–10 h depending on temperature.     

Enzymatic production of alkyl esters through alcoholysis: A critical evaluation of lipases and alcohols

This paper focuses on a detailed evaluation of commercially available immobilized lipases and simple monohydric alcohols for the production of alkyl esters from sunflower oil by enzymatic alcoholysis. Six lipases were tested with seven alcohols, including straight and branched-chain primary and secondary alcohols. The reactions were conducted in a batch stirred reaction vessel using stoichiometric amounts of substrates under solvent-free conditions. Dramatic differences in alcoholysis performance were observed among the different lipases. For most of the alcohols, Novozym 435 produced the highest yield of FA alkyl esters, with yields well over 90% for methanol, absolute ethanol, and 1-propanol. Overall, 96% ethanol was the preferred alcohol for all lipases except Novozym 435, and ethanolysis reactions reached the maximal conversion efficiency. Increasing the water content in the system resulted in an increased degree of conversion for all lipases except Novozym 435. The secondary alcohol 2-propanol significantly reduced the alcoholysis reaction with all lipases; however, the branch-chain isobutanol was more advantageous than linear 1-butanol for Novozym 435, Lipozyme RMIM, and Lipase PS-C. Many commercial immobilized lipases are highly efficient and promising for the production of alkyl esters, offering high reaction yields and a simple operation process.     

Alcoholysis of palm oil mid-fraction by lipase from Rhizopus rhizopodiformis

A mycelial lipase from Rhizopus rhizopodiformis was prepared in fragment form. The lipase was examined to catalyze the alcoholysis of palm oil mid-fraction (PMF) in organic solvents. High percentage conversions of PMF to alkyl esters were achieved when methanol or propanol was used as acyl acceptor. Of the two most prevalent fatty acids in PMF, palmitic acid seemed to be preferred over oleic acid in the formation of methyl and propyl esters. The optimal ratio of oil to methanol in the alcoholysis reaction is 1 to 2 moles. The lipase exhibited high alcoholysis activities in nonpolar solvents (log P>2), such as hexane, benzene, toluene, and heptane. The enzyme showed exceptionally high thermostability.     

Model Reactions Involving Ester Functional Groups during Thermo-Oxidative Degradation of Biodiesel

Biodiesel is a renewable fuel used in diesel engines that is typically blended with diesel fuel. However, biodiesel is susceptible to oxidation, which has the potential to produce higher molecular weight materials that may adversely impact vehicle fuel-system performance. To investigate the chemical reactions potentially important in biodiesel oxidation, four different types of chemical reactions involving esters were studied: (1) ester formation (reactions of acids with alcohols), (2) alcoholysis (reactions of alcohols with esters), (3) acidolysis (reaction of acids with esters), and (4) ester exchange (reactions between two esters). Experiments with representative model compounds were used to evaluate these reactions at 90 °C with aeration; conditions previously used to simulate thermo-oxidative degradation during biodiesel aging. Reactions were monitored using gas chromatography, fourier transform infrared (FTIR) spectroscopy, and total acid number (TAN). Evidence is presented suggesting that alcoholysis and ester formation (Reactions 1 and 2), catalyzed by carboxylic acids, are important reactions of esters that could lead to larger molecules. Acidolysis (Reaction 3) proceeded at a comparatively slow rate and ester exchange reaction products (Reaction 4) were not detected under these aging conditions.     

Purification of ethyl docosahexaenoate by selective alcoholysis of fatty acid ethyl esters with immobilized Rhizomucor miehei lipase

Ethyl docosahexaenoate (E-DHA) is efficiently enriched by the selective alcoholysis of ethyl esters originating from tuna oil with lauryl alcohol using immobilized lipase. Alcoholysis of ethyl esters by immobilized Rhizopus delemar lipase raised the E-DHA content in the unreacted ethyl ester fraction from 23 to 49 mol% in 90% yield. However, the content of ethyl eicosapentaenoate (E-EPA) was higher than the initial content. Hence we attempted to screen for a suitable lipase to decrease the E-EPA content, and chose Rhizomucor miehei lipase. Several factors affecting the alcoholysis of ethyl esters were investigated, and the reaction conditions were determined. When alcoholysis was performed at 30°C with shaking in a mixture containing ethyl esters/lauryl alcohol (1:3, mol/mol) and 4 wt% of the immobilized R. miehei lipase, the E-DHA content in the ethyl ester fraction was increased and the E-EPA content was decreased. By alcoholyzing ethyl esters in which the E-DHA content was 45 mol% (E-tuna-45) for 26 h, the E-DHA content was increased to 74 mol% in 71% yield and the E-EPA content was decreased from 12 to 6.2 mol%. To investigate the stability of the immobilized lipase, batch reactions were carried out continually by replacing the reaction mixture with fresh E-tuna-45/lauryl alcohol (1:3, mol/mol) every 24 h. The decrease in the alcoholysis extent was only 17% even after 100 cycles of reaction. It was found that increasing the proportion of lauryl alcohol increased the conversion of E-EPA to lauryl-EPA. When an ethyl ester mixture in which the E-DHA content was 60 mol% (E-tuna-60) was alcoholyzed for 24 h with 7 molar equivalents of lauryl alcohol, the E-DHA content was raised to 93 mol% with 74% yield and the E-EPA content was reduced from 8.6 to 2.9 mol%.     

Lipase-catalyzed synthesis of lesquerolic acid wax and diol esters and their properties

Lesquerolic acid was and α,Ω-diol esters were synthesized via immobilizedRhizomucor miehei lipase-(Lipozyme) catalyzed esterification of lesquerolic acid and alcoholysis of lesquerella oil. For each wax ester synthesis, when alcohol substrate was present at a slight (ca. 20%) stoichiometric excess and water content was kept low, over 94% of the hydroxy acyl groups were esterified. The extent of reaction and the ratio of monoester to diester produced for α,Ω-diol reactions was controlled by the solubility of diol in the medium. This latter quantity increased as alcoholysis proceeded due to the formation of partial glycerides and monoesters, which increased the polarity of the medium. Alcoholysis reactions were significantly slower when the medium diol content was above saturation. As the diol chainlength increased, diol solubilization decreased, the ratio of monoester to diester decreased, and the extent of hydrolysis increased. Alcoholysis reactions involving either fatty alcohols or diols suffered from acyl migration, which lowered the purity of lesquerolic acid esters. Several lesquerolic acid esters, synthesized on a preparative scale and purified via column chromatography, were evaluated for their properties: density, viscosity, and melting point. Potential applications for lesquerolic acid esters are discussed.     

Study on the alcoholysis of aromatic polyesters and related esters using a high-pressure calorimeter

Summary The heat of base-catalyzed alcoholysis of poly(ethylene terephthalate) (PET) and poly(ethylene 2,6-naphthalenedicarboxylate) (PEN) as well as several related aromatic and aliphatic esters has been measured using a high-pressure calorimeter. The process is essentially thermoneutral, and heats of CH₃ONa-catalyzed methanolysis of PET and PEN are +1.8±0.6 and +9.3±0.2 kJ/mol-carboxyl group, respectively. Furthermore, the heats of Zn(OCOCH₃)₂-catalyzed alcoholysis of PET with ethylene glycol and benzyl alcohol are also calculated as +5.8±0.2 and +6.6±0.8 kJ/mol-carboxyl group, respectively. These values are comparable to those for ethyl esters of p-substituted benzoic acids and propionic acid. Received: 15 December 1998/Revised version: 22 January 1999/Accepted: 29 January 1999     

Utilization of acid oils in making valuable fatty products by microbial lipase technology

Microbial lipase-catalyzed hydrolysis, esterification, and alcoholysis reactions were carried out on acid oils of commerce such as coconut, soybean, mustard, sunflower, and rice bran for the purpose of making fatty acids and various monohydric alcohol esters of fatty acids of the acid oils. Neutral glycerides of the acid oils were hydrolyzed byCanadida cylindracea lipase almost completely within 48 h. Acid oils were converted into fatty acid esters of short- and long-chain alcohols like C₄, C₈, C₁₀, C₁₂, C₁₆, and C₁₈ in high yields by simultaneous esterification and alcoholysis reactions withMucor miehei lipase as catalyst. Acid oils of commerce can be utilized as raw materials in making fatty acids and fatty acid esters using lipase-catalyzed methodologies.     

The direct alcoholysis of suprarenal phosphatides

Previous attempts to directly prepare methyl esters from phosphatides failed apparently because not enough HCl was present as catalyst. In the present work suprarenal phosphatides were directly converted into esters by alcoholysis with methyl, ethyl, propyl, butyl and amyl alcohols using 5.0% HCl and 7.5 and 12.0% H₂SO₄ as catalysts. The process of esterification is greatly simplified by this procedure.     

Synthesis of geranyl and citronellyl esters of coconut oil fatty acids through alcoholysis by Rhizomucor miehei lipase catalysis

Synthesis of geranyl and citronellyl esters of mixed fatty acids has been investigated by alcoholysis of coconut oil (CNO) using Rhizomucor miehei lipase. CNO fatty acid esters of geraniol and citronellol have unique mild flavors that can be used in food materials. Both geraniolysis and citronellolysis of CNO produce flavor esters in good yield. Depending on substrate concentration the molar yield is more than 50%. The optimized reaction conditions were: pressure, atmospheric; temperature, 50°C; incubation period, 5 h; and Lipozyme, 10% (w/w).     

Enzymatic synthesis of medium‐chain triacylglycerols by alcoholysis and interesterification of copra oil using a crude papain lipase preparation

We have examined the possibility of producing analogs of medium‐chain triglycerides (MCT) from copra oil, i.e. a triacylglycerol mixture with a high content of medium‐chain fatty acid moieties (C₆–C₁₀). A two‐step enzymatic process was used in which copra triacylglycerols were first split with papain lipase by alcoholysis with an alkyl alcohol and then subjected to interesterification with the alkyl esters recovered using papain lipase. Effects of temperature, water activity content, substrate ratio, biocatalyst amount, and alcohol chain length were also investigated. On the one hand, the sn‐3 stereoselectivity of the lipase in the alcoholysis of copra oil with butanol has permitted a direct enrichment of caproic, caprylic and capric moieties in the synthesized butyl esters. Thus, in the batch reactor, the reaction led to about 31% conversion of the oil after 24 h, and the content of C₆–C₁₀ acids in the synthesized esters increased from about 16% in the starting oil to almost 42%. A similar enzymatic alcoholysis in a packed‐bed column bioreactor gave 31% conversion of the oil after 120 min of reactor residence time. The reaction was also very selective because the C₆–C₁₀ fatty acyl groups represented about half of the newly formed butyl esters, whereas they accounted for only 16% of total fatty acids in the starting oil. On the other hand, the transesterification of the alkyl esters recovered (highly enriched in C₆–C₁₀ fatty acyl groups) with native copra oil directly led to an increase in the content of MCT in the oil, from 18 mol‐% at the beginning of the reaction to 61 mol‐% of MCT after a time period of 72 h in the batch reactor.     

Equilibria in the alcoholysis reactions of terephthalic esters and chemical valorization of polyethyleneterephthalate waste. I. Equilibrium constants determination

The depolymerization of polyethyleneterephthalate (PET) by alcoholysis is an easy operation and gives interesting prospects for the valorization of wastes. The reactive species being composed of esters and alcohols, all possible alcoholysis reactions happen, whether wanted or not. Finally, a complex blend of many molecules follows. Practically, two great types of reactions occur: a reaction called “interchange,” and a reaction called “polycondensation.” We have determined the values of global equilibrium constants of those two types of reaction. The values of polycondensation equilibrium constants are close to those estimated from the “equireactivity” principle. We did not observe any particular behavior of monomer species. When reactants are the di‐ or mono‐propylene glycols, the molar proportion of these glycolic radicals is higher in the free glycols than in the polyester chains. Both proportions are similar, when diethylene glycol or 2‐ethylhexanol are used. © 1999 John Wiley & Sons, Inc. J Appl Polym Sci 72: 329–340, 1999     

Fatty acid esters of methylglucoside prepared by the alcoholysis reaction

1. Alcoholysis of triglycerides by methylglucoside gave an impure reaction mixture containing from 60–70% of glucoside-monoesters.
2. The mono-, di-, and trioleoyl methylglucosides were prepared by alcoholysis of methyloleate with α-methylglucoside.
3. Hydrolysis of the glucoside esters of fatty acids to dextrose esters could not be achieved. The ester linkage hydrolyzed in preference to the acetal linkage.

     

The preparation of alkyl esters from highly unsaturated triglycerides

The alcoholysis reaction has been applied to the preparation of highly unsaturated alkyl esters from menhaden oil. This reaction proceeded very rapidly, and nearly quantitative yields were obtained with virtually, no loss in double-bond structure. The formation of esters was studied, using straight- and branched-chain alcohols having 1–6 carbon atoms. The reactions were monitored by the technique of thin-layer chromatography (TLC). Maximum conversion of straight-chain esters was found to be a linear function with respect to the number of carbon atoms in the alcohol. Reaction time varied from 2 min for methanol to 60 min for n-hexanol. Branched-chain alcohols reacted more slowly than did the corresponding straight-chain compounds. This reaction was found to be applicable to laboratory and large scale preparations of highly unsaturated alkyl esters. Presented at the AOCS meeting, St. Louis, Mo., 1961.     

Lipase catalyzed alcoholysis of sunflower oil

Lipase-catalyzed alcoholysis of sunflower oil under anhydrous conditions was examined. Lipases fromPseudomonas fluorescens and 2 immobilized enzymes fromMucor miehei and aCandida sp. gave sufficient conversion with petroleum ether as the solvent, even when methanol and ethanol were used. The overall content of tri-, di- and monoglycerides, as well as the corresponding alkyl esters, was measured. BecausePseudomonas lipase led to almost quantitative esterification, further studies were carried out with that enzyme varying the amounts of enzyme or the alcohols. Acceptable conversions were achieved even without solvent. Reaction rates of alcoholysis with 5 homologous alcohols, with or without the addition of water, were measured, and in all cases the reaction rates increased with higher chain length of the alcohol. In the case of methanol the highest rate was obtained without any addition of water, but a significantly higher rate was observed with 96% ethanol as opposed to absolute ethanol. The main advantages of lipasecatalyzed, nonaqueous alcoholysis as compared to classical procedures are the mild reaction conditions, the isolation of glycerin without further purification and without the formation of chemical waste, and the ability of lipases to catalyze the esterification of free fatty acids.     

Alkali-catalyzed alcoholysis of crambe oil and camelina oil for the preparation of long-chain esters

The alcoholysis of crambe and camelina oils was carried out with oleyl alcohol, alcohols derived from crambe and camelina oils, and n-octanol using potassium hydroxide as catalyst to prepare alkyl esters. Conversions to alkyl esters were about 0% with oleyl alcohol, 20–45% with crambe and camelina alcohols, and 60% with n-octanol. The conversion to esters for crambe and camelina oil with oleyl alcohol and n-octanol increased with increasing molar excess of alcohol. Composition of the alkyl esters formed was as expected from the composition of the reaction partners. Presented as part of the doctoral thesis of Georg Steinke to the University of Münster, Münster, Germany.     

Fatty acid esters of furfuryl alcohol

Summary Furfuryl esters were prepared from linseed oil and methyl palmitate by alcoholysis using metallic sodium as the catalyst. They were also prepared from linseed oil and from methyl oleate by partial saponification in furfuryl alcohol. These esters, although containing conjugated double bonds, did not possess any increased drying power. Iodine numbers were determined by several methods, and, except with the Woburn reagent, the furfuryl group was found to exhibit a higher iodine number when combined as an ester than when present as the free alcohol. Furfuryl esters were found to polymerize to products of greatly decreased iodine number and increased acidity, showing that polymerization involved both deacylation and reaction at the double bonds of the furan ring. Paper No. 53, Journal Series, Chemical Research Department, General Mills, Inc.