FR2772391A1 - Lipase=catalysed alcoholysis of sunflower oil - Google Patents

Abstract

Process for the enzymatic alcoholysis of sunflower oil having an oleic acid content above 80 mole% with a 1-10C monohydric primary alcohol comprises: continuously introducing a solvent-free liquid mixture of the sunflower oil and alcohol into a reactor containing a fixed-bed catalytic system comprising lipases immobilised on a hydrated polar support; allowing the reaction to proceed until steady-state conditions are achieved; and continuously recovering a product comprising sunflower fatty acid monoesters, the starting alcohol, monoglycerides and diglycerides.

Description

PROCESS FOR THE ENZYMATIC ALCOHOLICITY OF AN OIL
OLEIC SUNFLOWER, IN PARTICULAR FOR MANUFACTURING
A SURFACE-ACTIVE LUBRICANT COMPOSITION
The invention relates to the enzymatic alcoholysis of an oleic sunflower oil, especially for the manufacture of a surfactant lubricating composition.

 It is known that the enzymatic alcoholysis of oils or fats of plant or animal origin could theoretically make it possible to valorize in the industry the products of agriculture, and in particular by providing stable and pure fatty acid esters in respectful conditions. of the environment.

 Thus, the publication "Near-quantitative production of Fatty acid alkyl esters by lipase-catalyzed alcoholysis of fats and oils with adsorption of glycerol by silica gel", David E. Stevenson et al, Enzyme Microb.

Technol., 1994, vol 16, June, pp. 478-484, describes the enzymatic alcoholysis of sheep fat by discontinuous butanol with recirculation of the reaction medium, by means of two fixed-bed columns respectively containing the enzyme and gel. of glycerol-adsorbed silica formed insoluble in oil and in organic solvents, and which is supposed to cover the lipases and inhibit the reaction by limiting the diffusion of the substrate and the product.

 In practice, when the enzymatic alcoholysis of oils or fats of natural origin is carried out, there is a rapid decrease and a total loss of the enzymatic activity of the lipases.

 The aforementioned document thus proposes to trap the glycerol formed on a silica gel in order to avoid this loss of presumed enzymatic activity due to glycerol which binds to the catalytic system.

 However, this solution is in practice unsatisfactory insofar as the silica gel gradually traps the water of the reaction medium resulting in a gradual dehydration of the enzyme and a loss of activity. Thus, as indicated in this document, the loss of enzymatic activity is not acceptable in the context of an industrial process. In addition, the process carried out batchwise would not be feasible on an industrial scale.

 Thus, no solution compatible with a profitability on an industrial scale has been found to this problem of the decrease of the enzymatic activity, so that this way nevertheless promising for the alcoholysis of the oils and fats of natural origin n is not yet exploited in practice.

 The invention aims to overcome these disadvantages by proposing an enzymatic alcoholysis process, profitable on an industrial scale, to enhance, especially in the non-food industry, vegetable oils.

 The invention thus aims to find a new industrial application of certain vegetable oils, and therefore corresponding crops, currently reserved for obtaining oils for food use.

 The invention aims in particular to allow the manufacture, by enzymatic alcoholysis of vegetable oil, of a new composition which simultaneously has lubricant and surfactant properties and which, moreover, is stable to aging and heat.

 The invention also aims to allow this manufacture at low cost, and in respect of the environment, especially without production of toxic effluents.

 The invention also aims at providing an enzymatic alcoholysis process and a process for producing such a composition, the production of which remains stable over time, in particular for more than three months, without catalyst change or regeneration, and without require maintenance of the reaction.

 To this end, the invention relates to a process for the enzymatic alcoholysis of a vegetable oil by an alcohol, characterized in that it starts from a sunflower oil, called oleic sunflower oil, having a residue content of oleic acid greater than 80% (molar percentage) and at least one monohydroxyl starting primary alcohol having not more than 10 carbon atoms, in that a liquid starting composition consisting of a liquid mixture of sunflower and primary alcohol solvent free starting in a reactor comprising a fixed bed comprising an enzymatic catalyst system formed of lipases immobilized on a polar support hydrated, in that the reaction is continued until obtaining a steady state, and in that is obtained continuously at the outlet of the reactor an output composition containing monoesters of the fatty acids of sunflower oil and the primary alcohol of starting, monoglycerides and diglycerides.

 It should be noted that the process according to the invention is extremely simple and inexpensive to implement on an industrial scale in a plant essentially consisting of a continuous fixed bed reactor charged with the enzymatic catalyst.

 The inventors have thus found completely unexpectedly and contrary to the other enzymatic alcoholysis processes previously described, that in the process according to the invention, the enzymatic activity of the catalytic system initially decreases but stabilizes rapidly and remains at a corresponding high value. at a conversion rate of triglycerides of significant value, greater than 90% (molar percentage), with more than 50% (molar percentage) of the fatty acid residues in the composition of the starting oil which are converted into esters .

 Thus, while the conversion rate of triglycerides in a conventional alcoholysis in the presence of a solvent increases from 95% to less than 10% in a few hours, typically in less than 16 hours, this rate remains above 90% and very stable. over several months with a method according to the invention, and without any change or regeneration of the catalytic system.

 Just as surprisingly, the inventors have found that a certain amount of glycerol is formed and is fixed at the beginning of the reaction on the catalytic system (approximately 20% (weight of glycerol / weight of the support of the catalytic system)) but that the reaction mechanism changes rapidly and glycerol is no longer formed. Indeed, glycerol no longer binds to the catalytic system and the composition obtained is itself free of glycerol. In addition, even if a quantity of excess starting alcohol is used in order to extract the glycerol formed, it is found that the conversion rates obtained remain the same, the increase in the proportion of alcohol of starting in the medium having no effect on either the conversion or the composition of the products at the reactor outlet. Similarly, the addition of silica gel to the reaction medium for the purpose of trapping glycerol only delays one or two hours to obtain the stabilized regime and has no influence on the productivity of the process.

 Thus, it is clear that after an initial phase of normal alcoholysis, the reaction changes in nature and no longer produces glycerol, but only esters, monoglycerides and diglycerides. No clear explanation of this phenomenon can be given.

 The composition obtained also has particularly advantageous properties: it is both lubricant, thanks to its high proportion of esters, and surfactant, thanks to the presence of diglycerides and, especially, monoglycerides with emulsifying properties.

It is also stable to aging and heat treatments. Naturally produced and produced enzymatically, it is also biocompatible, biodegradable, non-toxic, very low cost, and can find many applications, especially in the formulation of cosmetic products (creams, shaving, hair removal ...), as adjuvant of phytosanitary products or fertilizers ...

 The invention thus extends to a method of manufacturing a surfactant lubricating composition, characterized in that the enzymatic alcoholysis of a sunflower oil, called oleic sunflower oil, having a residue content is carried out continuously. of oleic acid greater than 80% (molar percentage) with at least one monohydroxylated primary alcohol having not more than 10 carbon atoms, according to the following method: a liquid starting composition consisting of a liquid mixture of sunflower and primary alcohol solvent free starting continuously in a reactor comprising a fixed bed comprising an enzymatic catalyst system formed of lipases immobilized on a polar support hydrate, the reaction is continued until a stabilized regime, and a surfactant lubricating composition containing monoesters of the fatty acids of sunflower oil and alcohol is continuously recovered at the outlet of the reactor. starting material, monoglycerides and diglycerides.

 The invention thus relates to the application of an alcoholysis process according to the invention to the manufacture of a surfactant lubricating composition, that is to say a process for manufacturing a surfactant lubricating composition characterized in that an alcoholysis method according to the invention is used.

Advantageously and according to the invention, a saturated aliphatic alcohol, in particular an alcohol, is used.
R-OH where R is a linear or branched alkyl, as primary alcohol of departure. The starting alcohol (s) is chosen according to the nature of the esters desired in the composition obtained. The starting alcohol (es) must nevertheless be adapted to form the liquid starting composition, in particular be liquid (s) or solid (s) and soluble in the lubricating oil. departure.

 Advantageously and according to the invention, use is made of a starting composition comprising a molar ratio of triglycerides of oleic sunflower oil to the starting alcohol (s) at most equal to 2/3.

 Preferably, use is made of a starting composition comprising a proportion of starting alcohol (s) in excess of the stoichiometric theoretical value making it possible to obtain the composition according to the invention corresponding to a molar ratio of triglycerides / alcohol (s). of the order of 2/3. The remaining alcohol (s) of the composition can then be easily separated, for example by evaporation, in particular by distillation or evaporation under vacuum.

 Advantageously, starting from an unrefined oleic sunflower oil. In fact, the same results are obtained with unrefined oleic sunflower oil (in the raw state) as with refined oleic sunflower oil.

 Advantageously and according to the invention, an enzymatic catalytic system is used, the polar support of which is a macroporous hydrophilic resin.

 Advantageously and according to the invention, use is made of an enzymatic catalytic system formed of lipases derived from Rhizomucor mihei.

Advantageously and according to the invention, LIPOZYMEIM 60 marketed by the company is used.
NOVO NORDISK INDUSTRI A / S (Denmark) as lipases.

This enzyme is immobilized on DuoliteA568, which is a macroporous anion exchange resin of polar nature (hydrophilic). The average particle diameter is between 200 μm and 600 μm; the pore radius is between 50 and 300.10-10 m; the specific surface is of the order of 200 m2 / g; its water content is 4 to 10% (by weight); its density is 350 to 450 kg / m3; its tortuosity is of the order of 3; its internal porosity is of the order of 0.15.

 Furthermore, advantageously and according to the invention, use is made of a reactor adapted to have a piston-like behavior. The dimensions of the reactor, the amount of catalyst, and the flow rate of the starting composition are thus determined so that the passage of the single-phase liquid reaction medium in the reactor is as close as possible to a piston-like flow.

 The invention also extends to the surfactant lubricant composition obtained by a process according to the invention.

 Throughout the text, the term "molar proportion expressed as equivalent fatty acid residues" of a compound containing n fatty acid residues in its structure (n>, 1), incorporated in a composition, n times the concentration. molar C of this compound in the composition divided by the total number N of fatty acid residues of all the compounds forming the composition, that is (n / N) C.

 The invention thus relates to a surfactant lubricating composition characterized in that it comprises molar proportions, expressed as equivalent fatty acid residues, X of monoesters of fatty acids derived from an oleic sunflower oil having a content of oleic acid greater than 80% (molar percentage), M monoglycerides, D diglycerides and T triglycerides such that X> M, X> D, X> T, T <M and T <D.

 Advantageously and according to the invention, X is of the order of or greater than M + D + T.

 Advantageously and according to the invention, X is greater than 10%, especially between 52% and 57%.

Advantageously and according to the invention, T is of the order of or less than 10%
Advantageously and according to the invention, M is greater than D, and in particular is of the order of 2D.

 Advantageously and according to the invention, M is between 20% and 25% and D is between 10% and 12%.

 Advantageously and according to the invention, the monoesters, monoglycerides, diglycerides and triglycerides are mostly -more than 80% (molar percentage) - oleic acid compounds.

Advantageously and according to the invention, the fatty acid monoesters are monoesters of formula

where R is a linear or branched alkyl group derived from the primary alcohol R - OH, that is to say having at most 10 carbon atoms.

 The invention also relates to an alcoholysis process, a method of manufacture, and a composition, characterized in combination by all or some of the characteristics mentioned below or above.

 The examples below illustrate the invention. Figures 1 to 4 are diagrams illustrating the results obtained in the examples of the invention given below.

In the examples, an oleic sunflower oil is used which is supplied by
Cereals (TOULOUSE, FRANCS). This oil contains four main types of triglycerides composed mainly of oleic (O) and linoleic (L) acids: trilinolein (LLL), dilinoleoyl oleoyl glycerol (LLO), dioleoyl monolinoleoyl glycerol (LOO) and triolein (000) (80 mol%). Oleic acid represents about 85% of the total fatty acid residues, the other acids being linoleic acid (10%), stearic acid (3%), palmitic acid (2%) and traces of linolenic acid. The oil was used in the raw, unrefined state.

COMPARATIVE EXAMPLE 1
In a 9 mm diameter glass reactor thermostated at 40 C by a double jacket, 250 mg of Lipozyme IM 60 marketed by the
NOVO NORDISK INDUSTRI A / S (Denmark). This reactor is fed at a rate of 0.35 ml / min with a liquid composition containing 20 mmol / l (18 g / l) of oleic sunflower oil and 100 mmol / l (7.4 g / l) of butanol. solubilized in hexane.

 At the outlet of the reactor, the conversion rate of triglycerides is initially greater than 90% (molar percentage) and the composition formed consists of a mixture of esters substantially corresponding to the mixture of fatty acid residues constituting oleic sunflower oil. starting material (85% butyl oleate, 10% butyl linoleate, 3% butyl stearate and 2% butyl palmitate).

 The conversion rate of triglycerides initially greater than 90% drops rapidly to a value of less than 10% in less than 14 hours.

 Thus, it is seen that alcoholysis performed in the presence of a solvent provides the traditional result of a rapid and complete loss of enzymatic activity.

EXAMPLE 2
400 g of Lipozyme IM 60 are placed in the reactor thermostated at 400 ° C. in Example 1. The reactor is fed at 0.1 ml / min with a liquid starting composition consisting of oleic sunflower oil and butanol only. , without solvent, in 1/4 molar proportions (the volume ratio being 70/30).

 On leaving the reactor, the conversion rate of oleic sunflower oil is greater than 90%. In a first transitional step, the products formed are exclusively butyl esters, then the composition of the product mixture varies to finally reach equilibrium after 6 hours of operation. The output composition is then composed of esters, monoglycerides, diglycerides and residual triglycerides. It should be noted that the composition obtained is free of free fatty acids in appreciable proportions. 50% (molar percentage) of the fatty acid residues initially present in the starting oleic sunflower oil are in the form of esters, 20% as monoglycerides, 20% as diglycerides and 10% are not converted and remain as triglycerides.

 The stability of the process is tested over several months: the half-life time can not be determined because of the excellent operational stability of the process. After 3 months of continuous operation, no decrease in activity is detected.

 The productivity of the esters is 2 kg / h / kg of immobilized catalyst with a yield of 0.7 g of ester / g of oil.

The reactor outlet composition is regularly sampled and analyzed by chromatography.
HPLC.

 Figure 1 illustrates by white squares the evolution of the conversion rate of triglycerides over time, as well as that of the molar percentage of fatty acid residues converted to esters (black circles), or in the form of monoglycerides (black triangles). ) and diglycerides (white circles).

 It is thus observed that, contrary to Example 1, the conversion rate of triglycerides remains stable and of the order of 90%, its initial value.

 The analysis of the output composition also shows that after a transitional period, a steady state is reached for which the proportions of each of the constituents no longer change.

 Figure 2 illustrates, over a period of three months, the evolution of the conversion rate of triglycerides (white circles) and that of the proportion of esters formed (black circles). As can be seen, these values remain stable while the catalytic system has remained unchanged.

EXAMPLE 3
This example is identical to Example 2, but the starting butanol is replaced by 2-ethyl hexanol (branched C 8 primary alcohol) in molar proportions of 1/4.

 FIG. 3 illustrates the evolution of the conversion rate of the triglycerides of the starting oil (white circles) and that of the proportion of esters (ethyl hexyl oleates) formed (black circles).

EXAMPLE 4
This example is identical to Example 3, but octanol is used as the starting alcohol. FIG. 4 illustrates, in a similar manner to FIG. 3, the results obtained.

 As can be seen, the same results as in Example 2 are obtained with alcohols other than butanol in Examples 3 and 4.

EXAMPLE 5
Under the same conditions as those of Example 2, the molar ratio of the starting composition (triglycerides / butanol) is varied. The molar percentages of the fatty acid residues of the triglycerides of the starting oil converted to esters (X), monoglycerides (M), diglycerides (D) or non-converted (T) obtained in steady state are as follows
molar ratio of 1/3: X = 54%
M = 20%; D = 12%; T = 10%
molar ratio of 1/4: X = 52%
M = 21%; D = 12%; T = 10%
molar ratio of 1/5: X = 57% M = 25%; D = 10%; T = 8%
molar ratio of 1/10: X = 54%
M = 26%; D = 11%; T = 9%
In all these examples, the alcohol is in excess given the chemical equilibrium obtained, and is therefore found in the output composition. To separate it, just evaporate it. In all the examples, substantially the same proportions of the constituents of the exit composition are obtained, and the proportion of starting alcohol does not alter the equilibrium.

 It is therefore possible to use any quantity of alcohol in excess of the theoretical stoichiometric value of 2/3, providing 50% of esters.

EXAMPLE 6
In this example, a pilot reactor 3 cm in diameter and 18 cm in length containing 50 g of Lipozyme IM 60 is used.

 The mixture of oleic sunflower oil / butanol in 1/4 molar proportions is fed into the reactor with a flow rate of 5 ml / min.

 FIG. 5 represents the evolution over time of the concentrations (in mmol) obtained at the outlet of the reactor in butyl oleate (black circles), monoglycerides (black triangles), diglycerides (white circles) and triglycerides (white squares).

 The results are identical to those obtained in Example 2 with the reactor containing 1 g of catalyst. The concentration of butyl oleate in the outlet solution is initially high and decreases gradually to stabilize after 10 hours of operation.

The evolution curves for the triglyceride conversion ratio and the proportion of oleic acid are perfectly similar, as shown in FIG. 6, in which the squares represent the evolution of the conversion rate of the triglycerides (the white squares represent the values with the reactor of Example 1 with 1 g of catalyst, the black squares represent the values with the reactor of Example 5 with 50 g of catalyst), and the rounds represent the evolution of the molar proportion of the residues of oleic acid converted to butyl oleate (white circles for the 1 g reactor of Example 1, black circles for the 50 g reactor of Example 5).

 The increase in volume of the fixed bed by a factor of 50 had no effect on the performance of the reactor and no diffusional limitation was demonstrated.

 This example therefore confirms the good design of the reactor and shows that the change of scale can be operated without difficulty. The invention can therefore be implemented on an industrial scale.

 The value of the productivity obtained per gram of catalyst in the case of the implementation of an enzyme reactor containing 1 g of Lipozymee is similar to that calculated in the case where it is used 50 g of Lipozy Le Le Reactor of Example 5 makes it possible to produce a daily mixture consisting of 2.4 kg of butyl oleate, 1.1 kg of monoglycerides and 0.45 kg of diglycerides.

Claims (17)

 1 / - Process for the enzymatic alcoholysis of a vegetable oil with an alcohol, characterized in that one starts from a sunflower oil, called oleic sunflower oil, having an oleic acid residue content greater than 80 % (molar percentage) and of at least one monohydroxyl starting primary alcohol having not more than 10 carbon atoms, in that a liquid starting composition consisting of a liquid mixture of sunflower oil and alcohol is introduced starting solvent without solvent in a continuous reactor comprising a fixed bed comprising an enzymatic catalyst system formed of lipases immobilized on a polar support hydrate, in that the reaction is continued until a stabilized regime is obtained, and in that an output composition containing monoesters of the sunflower oil fatty acids and the starting primary alcohol, monoglycerides and diglycerides is recovered continuously from the reactor.  2 / - Method according to claim 1, characterized in that a saturated aliphatic alcohol is used as primary alcohol of departure.  3 / - Method according to one of claims 1 and 2, characterized in that an alcohol is used R-OH where R is a linear or branched alkyl as primary alcohol of departure.  4 / - Method according to one of claims i to 3, characterized in that a starting composition comprising a rappor. molar triglycerides of the hlirne of toesol on '' (the) alcohol (s) starting at most equal to 2/3.  5 / - Method according to one of claims 1 to 4, characterized in that one starts from an unrefined oleic sunflower oil.  6 / - Method according to one of claims 1 to 5, characterized in that an enzymatic catalyst system is used whose polar support is a macroporous hydrophilic resin.  7 / - Method according to one of claims 1 to 6, characterized in that an enzymatic catalyst system formed of lipases from Rhizomucor mihei.  8 / - Method according to one of claims 1 to 7, characterized in that a reactor adapted to have a piston type behavior.  9 / - A method of manufacturing a surfactant lubricating composition, characterized in that it continuously performs the enzymatic alcoholysis of a sunflower oil, called oleic sunflower oil, having an oleic acid residue content greater than 80% (molar percentage) with at least one monohydroxylated primary alcohol having not more than 10 carbon atoms according to the following process: a liquid starting composition consisting of a liquid mixture of sunflower oil and primary alcohol is introduced starting without a solvent continuously in a reactor comprising a fixed bed comprising an enzymatic catalytic system formed of lipases immobilized on a polar support hydrate, the reaction is continued until a stabilized regime is obtained, and is recovered continuously in reactor outlet a surfactant lubricating composition containing monoesters of the sunflower oil fatty acids and the primary alcohol of departure, noglycerides and diglycerides.  10 / - Process according to claim 9, characterized in that a saturated aliphatic alcohol is used as the primary alcohol of departure.  11 / - Method according to one of claims 9 and 10, characterized in that an alcohol is used R-OH where R is a linear or branched alkyl as primary alcohol of departure.  12 / - Method according to one of claims 9 to 11, characterized in that a starting composition comprising a molar ratio of triglycerides of sunflower oil on the (the) alcohol (s) starting at more equal to 2/3.  13 / - Method according to one of claims 9 to 12, characterized in that one starts from an unrefined oleic sunflower oil.  14 / - Method according to one of claims 9 to 13, characterized in that uses an enzymatic catalyst system whose polar support is a macroporous hydrophilic resin.  15 / - Method according to one of claims 9 to 14, characterized in that an enzymatic catalyst system formed of lipases from Rhizomucor mihei.  16 / - Method according to one of claims 9 to 15, characterized in that a reactor adapted to have a piston type behavior.  17 / - surfactant lubricating composition obtained by a process according to one of claims 9 to 16.