WO2007147237A1 - New process and reactor for the esterification of free fatty acids in oil or fat and for the production of biodiesel - Google Patents

Abstract

A process for the esterification of free fatty acids comprised in an oil or a fat, the process comprising: mixing the oil or fat with an alcohol, a liquid acid catalyst and a reticulated hydrophilic solid, thereby forming a mixture; and heating the mixture at a temperature between about 200C and about 15O0C is described. Also, a process for producing biodiesel comprising the above-mentioned steps and further comprising either transesterifying the triglycerides of the oil after the above-mentioned steps or hydrolyzing the triglycerides of the oil or fat prior to the above-mentioned steps is also described. Finally, a reactor for esterifying free fatty acids comprised in an oil or a fat comprising a chamber containing a hydrophilic reticulated hydrophilic solid, the chamber having an inlet for introducing reactants into the chamber, the reactants comprising the oil or fat, an alcohol and a liquid acid catalyst, and having an outlet for recovering the reactants; means for conveying the reactants from the inlet to the outlet through reticulated hydrophilic solid; and means for maintaining the chamber at one or more predetermined temperatures is described.

Description

TITLE OF THE INVENTION

[0001] NEW PROCESS AND REACTOR FOR THE ESTERIFICATION OF FREE

FATTY ACIDS IN OIL OR FAT AND FOR THE PRODUCTION OF BIODIESEL

CROSS REFERENCE TO RELATED APPLICATIONS

[0002] This application claims priority on U.S. provisional application no.

60/805,534, filed on June 22, 2006. All documents above are herein incorporated by reference.

FIELD OF THE INVENTION

[0003] The present invention relates to a new process and a new reactor for the esterification of free fatty acids in oil and fat and for the production of biodiesel.

BACKGROUND OF THE INVENTION

[0004] "Biofuels" and in particular "biodiesel" are now produced in many countries of the world as alternatives to petroleum products. Biodiesel is usually produced from a variety of oils, such as vegetable oils or recycled fryer oils, and waste animal fat. Biodiesel may be used alone or in mixture with petroleum diesel to fuel all types of vehicles equipped with diesel engines including trucks, locomotives, industrial equipments, private cars and boats. Biodiesel use reduces green house gas emission and consequently many governments have promoted it through tax exemption and other various incentives. Therefore, several biodiesel production plants have been built throughout the world and more are planned to enter into production in the next few years.

[0005] Biodiesel is usually produced by direct transesterification of triglycerides from an oil or a fat with an alcohol, often methanol, in presence of a basic (alkaline) catalyst, usually NaOH or KOH, by the reaction:

(R,-COO)₃(CH,,-CH-CH₂) + R₂OH ^Alkdt> > R₁-COOR₂ + CH₂OH-CHOH-CH_:OH triglyceride alcohol fatty acid alkyl ester glycerin

(biodiesel)

[0006] The glycerin produced is heavier than the newly formed fatty acid alkyl ester

(biodiesel) and is not very soluble in it. It therefore accumulates at the bottom of the reaction vessel together with the catalyst and some alcohol. The completeness of the transesterification reaction is usually monitored by measuring bound and free glycerin content in the final biodiesel product which, according to current standards, must be below 0.24 % by mass. To allow the reaction to continue toward completion for a while, the glycerin phase can be removed by decantation and some more alcohol and alkali can be added to the reaction vessel [US 6,015,440]. Thus, in order to meet the stringent ASTM D 6751-03 specifications concerning bound glycerin in biodiesel, the transesterification reaction is pushed toward completion at the cost of more reactants, but also considerable time, which is not desirable.

[0007] Continuous-flow processes for the production of biodiesel, which often use centrifuges for rapid removal of glycerin, have also been proposed [US 6,489,496].

[0008] The high cost of raw material (crude or partially refined vegetable oils) has led more and more biodiesel producers to exploit less expensive fat sources such as waste fats and oils of animal, fish and vegetable origins. However, this waste material contains higher levels of free fatty acids, i.e. up to 80 weight % in some cases. The presence of higher than 1 weight % of free fatty acid in raw oil and fat (i.e. an acid value higher than 2 mg KOH/g of oil or fat) has been associated with difficulties in the transesterification reaction itself and later on in the water wash process. In fact, the free fatty acids react with the alkali catalyst used in the transesterification reaction and form soap and micelles. The formation of these micelles interferes with the fatty acid alkyl ester and glycerin phase separation during the transesterification reaction itself and later on during water washing of the fatty acid alkyl ester phase.

[0009] Therefore, a two-step process for the production of biodiesel has been developed. In this process, the free fatty-acids are esterified prior to the transesterification of the glycerides as described above. The esterification of the free fatty-acids is usually carried out in acidic conditions (using an acid catalyst) in the presence of an alcohol, usually methanol or ethanol. The esterification reaction can be schematized, using H₂SO₄ as the acid catalyst, as :

LJ Qf")

R₃-COOH + R₄OH - ⁴ ► R₃-COCR₄ + H₂O

fatty acid alcohol fatty acid alkyl ester water

(biodiesel)

[0010] As shown by the above equation, the esterification of each mole of fatty acid will produce one mole of water. Therefore, the water content of the reaction mixture will increase during this process. In certain case, it may increase, for example, by as much as 6 % by mass. This relatively high water content may induce a phase separation which consequently reduces the reaction rate, since both the catalyst and the alcohol tend to accumulate in the water phase. Separation of reactants and catalyst will result in low reaction rates and considerably increased reaction times, which are undesirable for an industrial process.

[0011] The usual way to circumvent this problem is to increase the quantity of dry alcohol to dilute the water produced by the reaction [US 4,698,186] However, this method increases the cost of production because it requires more alcohol and decreases the quantity of biodiesel that can be effectively produced from fixed reaction-vessel volumes.

[0012] A three-step esterification process with removal of water by decantation in between the steps has also been proposed [US 6,965,044]. This method uses less alcohol, but has the disadvantage of the long process time required for reaction and decantation.

[0013] US 6,642,399 provides an ether solvent like tetrahydrofuran to dissolve both the lipid and water phases and increase the esterification rate of free fatty-acids with alcohol and an inorganic acid catalyst. However, the use of large quantities of ether solvents in an industrial environment may be dangerous and is therefore undesirable.

[0014] Also, the prior art describes processes for the esterification of free fatty acids in fats and oils, which use solid acidic catalysts instead of liquid acidic catalysts [see for example, US 4,698,186; US 2005/0107624 and WO 2004/096962].

[0015] The prior art [US 2004/0186307] also describes a method for the production of fuel from acid fats including the esterification of the free fatty acids at a high temperature (150 to 22O⁰C) in a vacuum with one or more bivalent or multivalent alcohols accompanied by solid neutral catalysts and without using any acid catalysts.

[0016] Further, the prior art describes a process for esterifying free fatty acids in an oil using an alcohol, an acidic catalyst and either a water scavenger or a water adsorbent, the water adsorbent being packed in a column or a soxhlet apparatus outside the reaction vessel [US 2006/0094890].

[0017] For fat and oil with relatively high free fatty acid content, it has been proposed [U.S. 6,855,838] to first hydrolyze (saponify) the oil or fat, therefore transforming the triglycerides into free fatty acid. This hydrolysis is then followed by the esterification of all the free fatty-acids (the original one and those formed by the hydrolysis) with an alcohol and an acid catalyst as described above. This esterification step produces the desired biodiesel. - A -

[0018] There is however still a need for new, simple and effective processes and reactors for esterification of free fatty acids in oil and fat and for the production of biodiesel.

[0019] The present description refers to a number of documents, the content of which is herein incorporated by reference in their entirety.

SUMMARY OF THE INVENTION

[0020] In accordance with the present invention, there is provided new processes and a new reactor for the esterification of free fatty acid in oil and fat and for the production of biodiesel.

[0021] The present invention firstly relates to a process for the esterification of free fatty acids comprised in an oil or a fat. This process comprises: (A) mixing the oil or fat with an alcohol, a liquid acid catalyst and a reticulated hydrophilic solid, thereby forming a mixture; and (B) heating the mixture at a temperature between about 20⁰C and about 150⁰C.

[0022] The present invention also relates to a process for the production of biodiesel from an oil or a fat comprising triglycerides and free fatty acids. This process comprises: (A) mixing the oil or fat with an alcohol, a liquid acid catalyst and a reticulated hydrophilic solid, thereby forming a mixture; (B) heating the mixture at a temperature between about 20⁰C and about 150⁰C; thereby esterifying the free fatty acids; and (C) transesterifying the triglycerides, thereby producing biodiesel.

[0023] In embodiments of the two above-mentioned processes, the oil or fat may comprise about 25% by weight or less of free fatty acids. More specifically, the oil or fat may comprise about 15% by weight or less of free fatty acids.

[0024] The present invention also relates to a further process for the production of biodiesel from an oil or a fat comprising triglycerides and free fatty acids, the process comprising: (A) hydrolyzing the triglycerides of the oil or fat; (B) mixing the oil or fat comprising hydrolyzed triglycerides with an alcohol, a liquid acid catalyst and a reticulated hydrophilic solid, thereby forming a mixture; and (C) heating the mixture at a temperature between about 20⁰C and about 150⁰C, thereby producing biodiesel.

[0025] In embodiments of this particular process, the oil or fat may comprise about

25% by weight or more of free fatty acids. More specifically, the oil or fat may comprise about 40% by weight or more of free fatty acids.

[0026] In embodiments of all these processes, the mixture may comprise about 0.1 % by weight, relative to the weight of the oil or fat, or more of the reticulated hydrophilic solid. More specifically, the mixture of the reactants may comprise about 1 % by weight, relative to the weight of the oil or fat, or more of the reticulated hydrophilic solid.

[0027] The present invention also relates to a reactor for esterifying free fatty acids comprised in an oil or a fat, the reactor comprising a chamber containing a reticulated hydrophilic solid, the chamber having an inlet for introducing reactants into the chamber, the reactants comprising the oil or fat, an alcohol and a liquid acid catalyst, and having an outlet for recovering the reactants; means for contacting the reactants with the reticulated hydrophilic solid; and means for maintaining the chamber at one or more predetermined temperatures.

[0028] In embodiments of the reactor, the contacting means may include means for conveying the reactants from the inlet to the outlet through the reticulated hydrophilic solid.

[0029] In embodiments of the reactor, the chamber may be an elongated chamber having a first and a second end and wherein the inlet may be located at the first end and the outlet may be located at the second end. In more specific embodiments, the elongated chamber may be a tube.

[0030] In embodiments of the reactor, the means for conveying the mixture may be a pump.

[0031] In embodiments of the reactor, the means for maintaining the chamber at the predetermined temperature may be a thermostated bath or oven.

[0032] In embodiments of the reactor, the oil or fat, alcohol and liquid acid catalyst may be mixed together prior to being introduced in the chamber.

[0033] In embodiments, the reactor of the invention may be operated in continuous mode. In other embodiments, the reactor of the invention may be operated in batch mode.

[0034] In embodiments of the reactor, the oil or fat may comprise triglycerides that have been hydrolyzed prior to the oil or fat being introduced in the chamber.

[0035] In embodiments of the reactor, the reactor may further comprise means for maintaining the reticulated hydrophilic solid inside the chamber while allowing passage of the reactants through the outlet.

[0036] Turning now to both the reactor and the process of the invention, in embodiments, the reticulated hydrophilic solid may be neutral. Also, the reticulated hydrophilic solid may be a silica gel, a zeolite or mixtures thereof. In specific embodiments, the reticulated hydrophilic solid may be a silica gel. In other specific embodiments, the reticulated hydrophilic solid may be a zeolite. In more specific embodiments, the silica gel or zeolite may comprise non-acidic chemically reactive groups. Also, the zeolite may be modified by an alkylsilane. Similarly, the zeolite may be impregnated by non-acidic organic or inorganic molecules. In embodiments, the reticulated hydrophilic solid is granular or in the form of beads.

[0037] In embodiments, the temperature may be between about room temperature and about a boiling point of the alcohol.

[0038] Also, in embodiments, the ratio of the alcohol to the free fatty acids may be between about 3:1 and about 50:1.

[0039] In embodiments, the oil or fat may be soap stock, beef tallow, coconut oil, corn oil, cottonseed oil, lard, olive oil, palm oil, palm kernel oil, peanut oil, soybean oil, linseed oil, tung oil, sunflower oil, safflower oil, canola oil, rapeseed oil, sesame oil, babassu oil, perilla oil, oiticica oil, fish oils, menhaden oil, castor oil, Chinese tallow tree oil, Physic nut oil, Cuphea seed oil, microalgal oils, bacterial oils, fungal oils, grease trap residues or mixture thereof.

[0040] In specific embodiments, the alcohol may be methanol, ethanol, propanol, butanol or mixtures thereof. More specifically, the alcohol may be methanol.

[0041] In embodiments, the liquid acid catalyst may be sulfuric acid, hydrochloric acid, phosphoric acid or mixtures thereof.

[0042] The present invention also relates to biodiesel produced by the processes of the invention and to oil or fat comprising esterified free fatty acids produced by the processes of the invention.

[0043] Turning now to the present invention in more details, there is provided processes for the esterification of free fatty acid in oil and fat and for the production of biodiesel. The present invention also relates to a reaction for esterifying free fatty acids in an oil or a fat.

Esterification of the free fatty acids

[0044] Firstly, the invention relates to a process for the esterification of free fatty acids in an oil or a fat, wherein the oil or fat is mixed with an alcohol, a reticulated hydrophilic solid and a liquid acid catalyst.

[0045] As used herein, esterification is the chemical reaction in which an alcohol and an acid form an ester as the reaction product. Such chemical reaction can be illustrated as follow:

R₁-C- OH + R₂-OH *- _RI __C__O_R_{2 +} H₂Q

[0046] During the process of the invention, the reticulated hydrophilic solid is in contact with the oil or fat, the alcohol and the liquid acid catalyst. The present inventor has found that reticulated hydrophilic solids unexpectedly act as catalysts during the esterification reaction of fatty acids. The inventor observed that the addition of a reticulated hydrophilic solid to the esterification reaction medium (comprising the oil or fat, the alcohol and the acid) unexpectedly increases the rate of esterification thereby decreasing the volume of alcohol and the time needed for the reaction and/or increasing the yield of the reaction. Without being bound by theory, it is believed that the reticulated hydrophilic solid act like a phase-boundary catalyst, allowing better physical interactions between the aqueous and oily phases. Furthermore, it has been found that the esterification process thus catalyzed is so efficient that it can be applied directly to the production of biodiesel on completely hydrolyzed water oil or fat as further described below.

[0047] The reticulated hydrophilic solid, also referred herein as the hydrophilic solid catalyst or the solid catalyst, is a reticulated hydrophilic solid having a relatively large surface area. As used herein, a "reticulated solid" refers to any porous solid, such as for example, net-like solids having holes. Without being bound by theory, it is believed that the reticulated hydrophilic solid provides a support for the binding and/or the concentrating of the free fatty acids, alcohol and liquid acid catalyst (which are all at least partly hydrophilic) in the hydrophobic environment (reaction medium), and thereby facilitates the esterification reaction. Any reticulated hydrophilic solid which may provide such a support for the binding or concentration of the reactant may be used in the process of the invention. The role of the reticulated hydrophilic solid is not to provide the reaction mixture with a significant amount of acidic groups. In other words, the reticulated hydrophilic solid is not a replacement for the acid catalyst needed for the esterification reaction. Therefore, in embodiments the reticulated hydrophilic solid may more specifically be neutral.

[0048] In embodiments, the reticulated hydrophilic solid may a silica gel or a zeolite and other suitable reticulated hydrophilic solids with similar properties.

[0049] As used herein, "silica gel" has its conventional meaning in the art and thus refers to a granular porous solid form of silica. More specifically, the silica gel may comprise chemically reactive groups. As used herein a "chemically reactive group", also called functional group, is a chemical group (i.e. a specific group of atoms within a molecule) that is able to react with other chemical groups in other molecules during a chemical reaction and is thus responsible for the characteristic chemical reactions of the molecule. Non-limiting examples of such chemically reactive groups include non acidic chemically reactive groups such as hydroxy, amine, amide, ether or ester.

[0050] As used herein, "zeolite" has its conventional meaning in the art and thus refers to porous alumino-silicate materials. More specifically, in embodiments, the zeolite may also be a molecular sieve. As used herein, "molecular sieve" refers to a particular property of these materials, i.e. the ability to selectively sort molecules based primarily on a size exclusion process. However, even in the embodiments where the zeolites are molecular sieves, the zeolites are not used as molecular sieves, but only as catalysts for the esterification reaction.

[0051] The zeolite may optionally be modified by an alkylsilane. As used herein

"alkysilane" is a silicon atom having attached thereto at least one alkyl group. In embodiments, the alkyl group may comprise up to 12 carbon atoms. The zeolite may also comprise chemically reactive groups. Non-limiting examples of such chemically reactive groups include non acidic chemically reactive groups such as hydroxy, amine, amide, ether or ester. Also, the zeolite may be impregnated with non-acidic organic or inorganic molecules of different nature.

[0052] In the process of the invention, the mixture thereby formed may comprise about 0.1%, 1%, 2%, 5% or 10% by weight or more of the reticulated hydrophilic solid. This percentage is expressed in weight % with respect to the mass of the oil or fat.

[0053] The process of the invention may take place at a temperature between about

20⁰C and about 150⁰C. More specifically, the temperature may be equal to or lower than the boiling point of the alcohol used as reactant. The temperature may be about 20⁰C, 40⁰C, 60°C, 80⁰C₁ 100⁰C, 120°C, 140°C or more. The temperature may be about 30⁰C, 5O⁰C, 70°C, 90⁰C, 11O⁰C, 130⁰C, 150⁰C or less. The temperature may be between about 30⁰C and about 60⁰C.

[0054] The process of the invention may advantageously take place at atmospheric pressure, but may also take place at any other pressure lower or higher than atmospheric pressure. More specifically, if the process is carried out at a temperature higher than the boiling point of the alcohol, the pressure may optimally be higher than the atmospheric pressure in order to avoid the evaporation of the alcohol. The determination of the temperatures and pressures adequate for use in any given circumstances is well within the skill of the person of ordinary skill in the art.

[0055] In the invention, the ratio of alcohol to free fatty acids may advantageously be between about 3:1 and about 50:1. However, any other ratios may also be used. More specifically, this ratio may be higher than (or equal to) about 5:1 , 10:1 , 15:1 , 20:1 , 25:1 , 30 :1 , 35 :1 , 40 :1 and 45:1. Also, this ratio may be lower than about 10:1 , 15:1 , 20:1 , 25:1 , 30:1 , 35:1 , 40:1 and 50:1.

[0056] In the process of the invention, any oil or fat comprising triglycerides and free fatty acids may be used. More specifically, the oil or fat may have a free fatty acid content of about 1%, 2%, 5%, 10%, 15%, 20%, 25%, 30%, 40%, 50%, 60%, 70%, 80% or 90% by weight or more. The oil or fat may also have a free fatty acid content lower than about 100%, 90%, 80%, 70%, 60%, 50%, 40%, 30%, 25%, 20%, 15%, 10% or 5%. Without being so limited, the oil or fat may be soap stock, beef tallow, coconut oil, corn oil, cottonseed oil, lard, olive oil, palm oil, palm kernel oil, peanut oil, soybean oil, linseed oil, tung oil, sunflower oil, safflower oil, canola oil, rapeseed oil, sesame oil, babassu oil, perilla oil, oiticica oil, fish oils, menhaden oil, castor oil, Chinese tallow tree oil, Physic nut oil, Cuphea seed oil, microalgal oils, bacterial oils or fungal oils, grease trap residues or mixture thereof.

[0057] Any monovalent alcohol known by the person of skill in the art to be suitable for use in the esterification of free fatty acid in oil or fat may be used in the process of the present invention. More specifically, the alcohol may be a branched, linear or cyclic alkyl alcohol or an aryl alcohol. The alcohol may be methanol, ethanol, propanol, and butanol, or mixtures thereof. More specifically, the alcohol may be methanol. In embodiments, the alkyl alcohol may comprise up to 12 carbon atoms. Also, the aryl alcohol may comprise between 5 and 12 carbon atoms.

[0058] The a liquid acid catalyst may be any acid catalyst that is liquid at the temperature at which the esterification reaction is carried out and known by the person of skill in the art to be efficacious for the esterification of free fatty acid in oil or fat. The liquid acid catalyst provides acid groups which allows for the esterification reaction. In embodiments, the liquid acid catalyst may be sulfuric acid, phosphoric acid or hydrochloric acid.

Esterification of the free fatty acids followed by transesterification of the triglycerides

[0059] The present invention also relates to process for producing biodiesel from oil and fat. In this process, the free fatty acids of the oil or fat are esterified using the process described above and the triglycerides in the oil or fat are then transesterified using any process for doing so known in the art.

[0060] As used herein, "transesterification" refers a process to transform one ester into a different ester in which the alkoxy group of the ester is exchanged by that of an alcohol. Such process can be illustrated as follow:

[0061] In this process for producing biodiesel, the esterification of the free fatty acid is the same as described above. The conditions of the esterification reaction, the alcohol, liquid acid catalyst and reticulated hydrophilic solid are also the same as above.

[0062] In this process, the oil or fat comprises triglycerides and free fatty acid. Any oil or fat known in the art to be suitable for producing biodiesel may be used. More specifically, the oil or fat may have a free fatty acid content of about 5%, 10%, 15%, 20%, 25% or less. Without being so limited, the oil or fat may be soap stock, beef tallow, coconut oil, corn oil, cottonseed oil, lard, olive oil, palm oil, palm kernel oil, peanut oil, soybean oil, linseed oil, tung oil, sunflower oil, safflower oil, canola oil, rapeseed oil, sesame oil, babassu oil, perilla oil, oiticica oil, fish oils, menhaden oil, castor oil, Chinese tallow tree oil, Physic nut oil, Cuphea seed oil, microalgal oils, bacterial oils or fungal oils.

[0063] The transesterification of the triglycerides following the esterification of the free fatty acids may be effected by any of the methods to do so known in the art. For example, without being so limited, the methods described in US patents 2,271 ,619, 2,360,844, 2,383,580 or 2,383,581 may be used.

[0064] More specifically, the triglycerides may be transesterified using a basic catalyst and an alcohol, with a ratio of alcohol to triglycerides in the range of about 2:1 to about 35:1 and at a temperature equal to or lower than the boiling point of the alcohol used. The alcohol may be the same as or different from that used for the esterification of the free fatty acids. The alcohol may be any alcohol known by the person of skill in the art to be suitable for such use. The alcohol may be methanol, ethanol, propanol, butanol, or mixtures thereof. The basic catalyst may be any catalyst known by the person of skill in the art to be suitable for such use. The basic catalyst may be sodium hydroxide, potassium hydroxide, sodium carbonate, or mixtures thereof.

Esterification of the free fatty acids following hydrolysis of the triglycerides

[0065] The present invention also relates to a further process for producing biodiesel from oil and fat. In this process, the triglycerides in the oil or fat are hydrolyzed using any of the process for doing so known in the art, which results in the production of more free fatty acids. Then, the free fatty are esterified using the process described above. Such a method is particularly suited with recycled oils or fats containing large amounts of free fatty acids of more than 50 % of total, such as for example, grease trap residues. That is, in these conditions, it could be less expensive to complete the hydrolysis of residual triglycerides first and then conclude the production process with the esterification reaction.

[0066] The hydrolysis of the triglycerides prior to the esterification of the free fatty acids may be effected by any of the methods to do so known in the art. For example, without being so limited, the method described in US patents 6,855,838 may be used. More specifically, the oil and fat may be hydrolyzed by acid or basic treatment.

[0067] The esterification of the free fatty acid is the same as described above. The conditions of the esterification reaction, the alcohol, liquid acid catalyst and reticulated hydrophilic solid are also the same as above.

[0068] In this process for producing biodiesel, the oil or fat comprises triglycerides and free fatty acids. Any oil or fat known in the art to be suitable for producing biodiesel may be used. More specifically, the oil or fat may have a free fatty acid content of about 5%, 10%, 15%, 25%, 30%, 40%, 50%, 60%, 70%, 80%, 90% or more. Also, the oil or fat may have a free fatty acid content lower than about 10%, 20%, 25%, 40%, 50%, 60%, 70%, 80%, 90% or 100%. The oil or fat may be soap stock, beef tallow, coconut oil, corn oil, cottonseed oil, lard, olive oil, palm oil, palm kernel oil, peanut oil, soybean oil, linseed oil, tung oil, sunflower oil, safflower oil, canola oil, rapeseed oil, sesame oil, babassu oil, perilla oil, oiticica oil, fish oils, menhaden oil, castor oil, Chinese tallow tree oil, Physic nut oil, Cuphea seed oil, microalgal oils, bacterial oils, grease trap residues or fungal oils.

Reactor

[0069] This invention also relates to a reactor of esterifying the free fatty acid in an oil of a fat. [0070] This reactor comprises a chamber having an inlet and an outlet. This chamber may be of any size and any shape. In embodiments, this chamber may advantageously be elongated. More specifically, this chamber may be a tube with the inlet at one end and the outlet at the other end. This chamber comprises the reticulated hydrophilic solid described above.

[0071] The reactor also comprises means for contacting said reactants with said reticulated hydrophilic solid. In embodiment, this means for contacting may means for conveying the reactants from the inlet to the outlet of the chamber through the reticulated hydrophilic solid. Such means may be any suitable means for conveying a liquid known in the art. For example, it may be a suitable pump, such as a peristaltic pump or a metering pump, or if the design of the chamber is appropriate, it may be gravity.

[0072] The speed at which the reactants will be conveyed through the reticulated hydrophilic solid will depend on the degree of esterification of the free fatty acid desired and the shape and size of the chamber of the reactor. Indeed, the longer the reactants will be in contact with the reticulated hydrophilic solid, the higher the degree of esterification. To obtain a relatively high degree of esterification, the shape or size of the chamber must allow for a relatively long path of reticulated hydrophilic solid for the reactants to go through and/or the mixture must be conveyed relatively slowly from the inlet to the outlet of the chamber. Without being so limited, for a same degree esterification, the mixture can be conveyed rather rapidly through a long tubular chamber or rather slowly through a smaller rather round chamber.

[0073] The reactor also comprises means for maintaining the chamber at one or more predetermined temperatures. More specifically, the whole chamber may be maintained at one temperature, different parts of the chamber may be maintained at different temperatures, the temperature of the whole chamber or of different parts of the chamber may be varied with time. Such means for maintaining the chamber at one or more predetermined temperatures may be any suitable means known in the art for maintaining a temperature. More specifically, it may be a thermostated bath or oven, or a jacket circulating a medium, such as water or steam, at the appropriate temperature around the chamber.

[0074] The amount of reticulated hydrophilic solid and its location inside the chamber will depend on the size and shape of the chamber and the degree of esterification desired. The reticulated hydrophilic solid must be in the path of the reactants being conveyed from the inlet to the outlet of the chamber. In embodiments, the chamber may advantageously be filled with the reticulated hydrophilic solid.

[0075] Particulate or granular reticulated hydrophilic solid, or such solid in the form of beads, are advantageous as they may help in mixing the reactants together by turbulence of flow around the reticulated hydrophilic solid particles while the reactants are moving along their path from the inlet to the outlet of the chamber. Alternatively, the reactants may be mixed together prior to being inserted in the reactor.

[0076] If needed, the reticulated hydrophilic solid may be retained in the reactor using suitable means to do so known by the person of skill in the art. Such means should allow the reactants to get out of the reactor while retaining the reticulated hydrophilic solid in it. Non limiting examples of such means include glass wool and fine wire mesh.

[0077] The reticulated hydrophilic solid may be used repeatedly and for very long periods of time without loosing much efficacy. However, if needed, it may be recycled by simple washing with an appropriate solvent followed by drying.

[0078] The reactor may be operated in batch or in continuous mode.

[0079] Other objects, advantages and features of the present invention will become more apparent upon reading of the following non-restrictive description of specific embodiments thereof, given by way of example only with reference to the accompanying drawings.

BRIEF DESCRIPTION OF THE DRAWINGS [0080] In the appended drawings:

[0081] Figure 1 shows the kinetic of esterification of free fatty acids in recycled corn oil at 31⁰C;

[0082] Figure 2 compares the kinetics of esterification of free fatty acids in recycled corn oil at 31⁰C in presence of Molecular Sieve type 4A in quantities of 0, 1 and 2 mass % with respect to the mass of the oil in the reaction medium; and

[0083] Figure 3 shows a plot of apparent kinetic constants k' of esterification reaction as a function of methanol concentration [The slope of the least-square lines give directly the kinetic constant k of the second order reaction v = k[FFA][methanol] in presence and absence of Molecular Sieve since the methanol concentration is in considerable excess over the FFA concentration (variation of methanol concentration is negligible during reaction)]. DESCRIPTION OF SPECIFIC EMBODIMENTS

[0084] The present invention is illustrated in further details by the following non- limiting examples.

COMPARATIVE EXAMPLE 1

Production of biodiesel (esterification of free fatty acids followed by transesterification of triglycerides) from a vegetable oil with a low acid value according to the prior art

[0085] This example illustrates the transesterification of vegetable oils such as canola and soybean oil, using a 7,4:1 ratio of methanol to trioleic acid as an illustration of prior art.

[0086] The soybean oil was a food-grade product obtained as 100 % pure soybean oil of Selection Merite, Montreal, Quebec, Canada. The acid value was determined as 0.11 mg KOH/g of oil according to American Standard and Testing of Materials method D 664. An acid value of less than 2 mg KOH/g oil or fat means that the oil or fat comprises less than 1% of free fatty acids. An oil or fat with less than 2 mg KOH/g oil or fat is generally considered to have a low acid value.

[0087] The solvent was anhydrous methanol ACS grade, NaOH was also ACS grade at least 99 % pure, and concentrated HCI were all purchased from Fisher Scientific (Montreal, Quebec, Canada).

[0088] For transesterification of soybean oil, 900 g of oil was heated to 60⁰C and

225 ml of a 1.2 % mass/volume NaOH solution in methanol was added and reacted under constant stirring for 60 min. The glycerin formed during the reaction was removed by decantation and a further 175 ml of 1.2 % mass NaOH in methanol was added to the upper methyl ester phase. The transesterification reaction was carried out for another 60 min at 60⁰C. The glycerin phase was removed by decantation and the upper methyl ester phase was collected and gently washed with 1 liter of hot water (48°C) in a separatory funnel. The water phase was removed by decantation. The pH of the wash water was 11. The methyl ester phase was washed again with 1 liter of hot 2 mM HCI. The pH of the water phase was about 5. A final wash with hot water was done and the pH of the water phase was 6. The methyl ester (biodiesel) was dried by heating at 100°C under vacuum for 65 min.

[0089] Free and bound glycerin was assayed in biodiesel by Magellan Midstream

Partners, LP. (Kansas City, Kansas) using the ASTM method D 6584. The results indicated 0.000 mass % of free glycerin, 0.574 mass % of monoglyceride, 0.091 mass % of diglyceride and 0.162 mass % of total glycerin. Both free and bound glycerin where within current ASTM D 6751-3 specifications for biodiesel.

COMPARATIVE EXAMPLE 2

Production of biodiesel (esterification of free fatty acids followed by transesterification of triglycerides) from a fat with a relatively high acid value according to the prior art

[0090] This example illustrates treatment of fat with higher than 2 mg KOH/g acid value according to prior art.

[0091] Pork lard purchased at a local food market (340 g) was ground in a meat grinder and heated at 130⁰C for 60 min. The solid residue was removed by passing the grinded lard through a cheesecloth yielding 200 g of fat. After cooling down to room temperature, the acid value was measured at 3 mg KOH/g of fat according to ASTM method D 664. Since the acid value of the pork fat was higher than 2 mg KOH/g of fat, 100 g of fat was reacted at 60⁰C for 60 min with 20 ml of methanol ACS grade and 0.125 ml of 97 % pure H₂SO₄ (Fisher Scientific) to esterify free fatty-acids prior to transesterification of triglycerides with methanol and NaOH as a catalyst.

[0092] For the transesterification of triglycerides, 0.38 g of NaOH was dissolved in

22 ml of methanol and added to the reaction medium immediately after the first reaction with H₂SO₄ was finished. The reaction in alkali was carried out for 60 min at 6O⁰C. The lower glycerin phase was removed by decantation in a separatory funnel and the methyl ester phase was gently washed with 100 ml of 0.01 M H₂SO₄ at 50°C and then with deionized water. The methyl ester phase (biodiesel) was then heated at 120°C in an oven for 70 min to decant residual water.

[0093] The biodiesel (74 g) was analyzed for free and bound glycerin by Magellan

Midstream Partners L. P. according to ASTM method D 6584. The results indicated a free glycerin content of 0.001 mass %, 0.832 mass % of monoglyceride, 1.596 mass % of diglyceride, 2.290 mass % of triglyceride and 0.693 mass % of total glycerin.

[0094] Direct transesterification by the above procedure of the same pork lard fat preparation without pretreatment with H₂SO₄ yielded a methyl ester preparation which was very difficult to wash. The soap formed large amounts of micelles at the water/ester interface during decantation and a total of nine hot water washes were necessary to obtain a relatively clear ester phase.

[0095] The dried ester was analyzed for free and bound glycerin by Magellan Midstream Partners LP. according to ASTM method D 6584. The results indicated a free glycerin content of 0.001 mass %, 0.833 mass % of monoglyceride, 1.623 mass % of diglyceride, 2.336 % of triglyceride and 0.702 mass % of total glycerin.

EXAMPLE 1

Esterification of free fatty acids in an oil with a relatively high acid value according to the present invention and the prior art

[0096] This example describes kinetic studies of the esterification reaction in recycled oil with higher than acceptable acid value (higher than 2 mg KOH/g of oil) for direct transesterification. Kinetic of esterification of free fatty acids was studied in recycled corn oil obtained locally with an acid value of 11.08 mg of KOH/g of oil.

[0097] The reaction medium containing 100 g of recycled corn oil, 20 ml of methanol

(molar ratio of methanol to free fatty-acids of 24.7: 1) was thermostated in a water bath at 31 °C or 60⁰C, and the medium was kept under constant stirring during the course of the kinetic experiment. Many experiments were conducted at 31 °C to slow down the reaction in order to obtain reliable comparative kinetic data. The reaction was started (zero time) by rapid addition of 0.54 ml of 97 mass % H₂SO₄. Aliquots (8 ml) of the reaction medium were taken with a pipette after 4, 15, 30, 60, 90 and 120 min. Shorter reaction times of 2, 5, 10, 20 and 30 min were used when the kinetic experiment was performed at 60°C. The aliquots were immediately quenched in 100 ml of 2-propanol containing 2 ml of 1 % phenolphthalein in 60 % 2-propanol (Fisher Scientific) and the solution was titrated with 0.1 N KOH. The acid value of residual non-esterified fatty-acids was obtained after subtraction of the acid value of H₂SO₄. The natural logarithm of the net acid value due to free fatty-acids was then plotted as a function of time and is shown in Figure 1. The kinetic constant ki of the rapid phase of esterification cannot be determined with precision and is estimated. Kinetic constant k₂ of the slower-rate phase of esterification and intercept at the y-axis were obtained from the graph and used according to a first-order kinetic model to estimate the reaction time needed to reduce the acid value of recycled oil to lower than 2 mg KOH/g of oil (Table 2).

[0098] Figure 1 shows kinetic of the esterification reaction of free fatty acids in recycled corn oil at 31⁰C according to the prior art. The recycled corn oil had an acid value: 11 ,08 mg KOH/g of oil. The esterification reaction progresses in a biphasic mode described by two exponential functions. For the purpose of biodiesel production, it is the lower-rate kinetic constant k₂ that determines the time necessary to reduce acid value to lower than 2 mg KOH/g. The molar ratio of methanol to free fatty acid was 24.7:1. [0099] Kinetic analysis of the acid-catalyzed esterification of waste corn oil free fatty-acids showed that the reaction kinetic has two-phases as shown by the biphasic decay curve of Figure 1. The rapid phase of the esterification reaction, with a first-order kinetic constant ki of about 83 x 10^'3 min^'1, occurs in the first 10 min of reaction at 31 °C and is followed by an about 15-fold lower rate phase with a constant k₂ of 5,63 x 10^"3 min^"1. The lower rate phase is relevant to the industrial production of biodiesel since it determines the time necessary to reduce free fatty-acid concentration in the oil or fat to less than about 1 % by mass. After this condition is met, the triglycerides are ready to be transformed into methyl ester of fatty acid (biodiesel) by transesterification, without interference from free fatty-acids.

[00100] Molecular Sieve type 4A, grade 514, 8-12 mesh beads, Alumina-Silicate base, was obtained from Fisher Scientific (Montreal, Quebec, Canada) and Silica Gel Ultra- Pure 230-400 mesh, 60 A pore size, was purchased from SiliCycle (Quebec City, Quebec, Canada). These reticulated hydrophilic solids were added to the reaction medium as catalysts to increase the rate of the esterification reaction at 1 and 2 % by weight concentration by respect to oil in the reaction medium (Figure 2 and 3).

[00101] Figure 2 shows that Molecular Sieve type 4A added at 1 and 2 weight % concentrations to the reaction medium increases significantly the first-order rate constant, k₂, of the esterification reaction and Figure 3 shows that this effect of the Molecular Sieve type 4A is observed at all methanol to free fatty acid molar ratios between 3.9 :1 and 24.7:1. The rate constant k₂ is a linear function of methanol concentrations both with and without Molecular Sieve type 4A in agreement with the pseudo first-order kinetic model of chemical reactions since the methanol reactant is in considerable excess over the FFA. The Molecular Sieve acts as a catalyst by increasing esterification rate, k, from 1 ,15 x 10^~3 min^'1 to 1 ,53x 10^"3 min^"1 from the slopes of lines in Figure 3.

[00102] Table 1 shows that the first-order kinetic constant, k₂, increases with temperature from 31 to 60⁰C, and that Silica Gel, another reticulated hydrophilic solid, also has a catalytic effect on rate constant of esterification k₂ as the Molecular Sieve type 4A.

[00103] Table 1 : Kinetic Constant (k₂) of Esterification of Free Fatty-acids.

Methanol/ k₂ x 10^"3 (min^"1)

Free Fatty Acid Ratio 31⁰C 60⁰C 0% MS 1 % MS 2% MS 0% MS 1 % MS 1 % SG

24.7 5.63 7.67 12.95 71.8 106.4 137.0

MS: Molecular Sieve type 4A, SG: Silica Gel ultra-pure

[00104] The reaction times necessary to reduce acid value of recycled corn oil from

11.08 mg KOH/g to lower than 2 mg KOH/g with different esterification conditions is presented in Table 2. Reaction time is significantly reduced by the presence of reticulated hydrophilic solids, such as Molecular Sieve and Silica Gel, or the same reaction time can be obtained in presence of the reticulated hydrophilic solids but at significantly lower concentrations of methanol. The use of lower quantities of reactants like methanol is desirable in the context of large scale production to reduce the cost of methanol recycling. Indeed, methanol must be removed by distillation both in the separated methyl ester and glycerin phases. However, a "wet" methanol is obtained and it must be further purified by plate distillation to remove traces of water before recycling in the esterification and transesterification reactions.

[00105] Table 2: Extrapolated time to reduce acid value of corn oil to less than 2 mg KOH/g

Methanol/ Time (min)

Free Fatty Acid Ratio 31 °C 60 ⁰C

0% MS 1 % MS 2% MS 0% MS 1 % MS 1 % SG

24.7 198 149 73 13.3 9 1 6 .9

15 235 200

8.75 320 220

4.9 944 341

MS: Molecular Sieve type 4A, SG: Silica Gel ultra-pure

EXAMPLE 2 Production of biodiesel (hydrolysis of the triglycerides followed by the esterification of the free fatty acids) from an oil with a relatively high acid value according to the present invention

[00106] This example describes esterification of hydrolyzed triglycerides after saponification as a process for the production of biodiesel.

[00107] The saponification of 500 g pure canola oil (Selection Merite) was carried out for 150 min at 100⁰C with 147 g of 50 mass % NaOH under constant agitation. The NaOH was neutralized by addition of 162 g of 50 mass % H₂SO₄ and the mixture was kept at 100⁰C under strong agitation for another 30 min to melt all solids. The mixture was transferred to a separatory funnel for decantation. After 30 min at room temperature, the lower aqueous phase was discarded and the top oily phase was dried at 110⁰C overnight. The acid value of the saponified and dried oily phase (free fatty acids) was 171.7 mg KOH/g.

[00108] This preparation of free fatty acids was esterified at 31 °C with methanol in presence of H₂SO₄ and silica gel. The molar ratio of H₂SO₄/methanol/free fatty acids was 1 :88,4:15,3 and the reaction medium contained 30 mass % of silica gel by respect to the mass of fatty acids. After 12 hours, the quantity of free fatty acids was reduced to 41 % of the original quantity. More methanol was then added to raise the methanol/free fatty acid molar ratio to 11.6 :1. After a total of 25 hours, the residual free fatty acids content was less than 6.7 % of initial value. The silica gel was allowed to sediment and the two upper phases (oil and methanol) were recovered and transferred to a 1 liter separatory funnel. Water (300 ml) at room temperature was then added to the separatory funnel to wash the oily phase under gentle agitation. The water wash was repeated twice until the lower water phase was clear and the pH was between 5 and 6. The oily phase (biodiesel) was collected and dried in an oven at 110⁰C for 120 min.

[00109] The yield of biodiesel was 89 % by respect to the weight of original free fatty acids. The acid value of the finished biodiesel was 3.99 mg KOH/g.

EXAMPLE 3 Reactor for the esterification of free fatty acids

[00110] Figure 2 shows that the rate constant, k₂, of the esterification reaction increases significantly when more Molecular Sieve is added to the reaction medium. Although this property of Molecular Sieve can be exploited in a batch procedure, as demonstrated in the examples provided herein, to exploit it to a maximum, a continuous flow process is optimal.

[00111] To illustrate such a process, a static reactor made of a long flexible tube filled with a hydrophilic reticulated solid was built. The reactants: free fatty acids in oil and methanol containing an inorganic acid were mixed by pumping at different rates corresponding to their concentration ratio directly into one end of the static reactor tube. The temperature of the reactor was maintained at about 50⁰C using a water bath. The reaction product was collected at the outlet of the reactor tube and the rest of the production process of biodiesel was continued directly on the output intermediate product either with a continuous flow process or with a batch process.

[00112] More specifically, the reactor was built from flexible polyethylene tubing (6.35 mm interior diameter by 308 cm length) filled with 61 g of Molecular Sieve type 4A beads. The total volume inside the tube was 96.5 ml and the void volume between the reticulated hydrophilic solid particles was about 40 ml. One end of the tube was fed with a variable speed peristaltic pump (Fisher Scientific) at a flow rate of 1.25 ml/min from two tanks: one containing 220 ml of used corn oil (acid value of 11.08 mg KOH/g of oil) and the other 40 ml of 5 % H₂SO₄ in methanol. The two tanks delivered precisely 1 volume of oil for 0.18 volume of the H₂Sθ₄/methanol solution to the pump inlet. The pump flow rate and void volume inside the tube allowed the reactants a residence time of 32 min. The temperature of the tube/reactor was kept at 50⁰C by immersion in a thermostated water bath. The product was collected at the outlet of the reactor during a period of 145 min for a total volume of 181 ml. The transesterification was then carried out on the collected solution according to the method described in Example I.

[00113] The resulting biodiesel was analyzed for free and bound glycerin by

Magellan Midstream Partners LP. according to ASTM method D 6584. The results indicated a free glycerin content of 0.003 mass %, 0.912 mass % of monoglyceride, 1.564 mass % of diglyceride, 2.121 % of triglyceride and 0.608 mass % of total glycerin. Both free and bound glycerin where within ASTM D 6751-3 specifications for biodiesel.

[00114] Such a reactor may also be applied to produce biodiesel directly from oil and fat after complete hydrolysis of triglycerides in acidic or basic conditions (saponification).

[00115] Although the present invention has been described hereinabove by way of specific embodiments thereof, it can be modified, without departing from the spirit and nature of the subject invention as defined in the appended claims.

Claims

WHAT IS CLAIMED IS:

1. A process for the esterification of free fatty acids comprised in an oil or a fat, the process comprising:

(a) mixing the oil or fat with an alcohol, a liquid acid catalyst and a reticulated hydrophilic solid, thereby forming a mixture; and

(b) heating said mixture at a temperature between about 20⁰C and about 150⁰C.

2. A process for the production of biodiesel from an oil or a fat comprising triglycerides and free fatty acids, the process comprising:

(a) mixing the oil or fat with an alcohol, a liquid acid catalyst and a reticulated hydrophilic solid, thereby forming a mixture;

(b) heating said mixture at a temperature between about 20⁰C and about 150⁰C, thereby esterifying said free fatty acids; and

(c) transesterifying the triglycerides, thereby producing biodiesel.

3. The process of claim 1 or 2 wherein said oil or fat comprises about 25% by weight or less of free fatty acids.

4. The process of claim 3 wherein said oil or fat comprises about 15% by weight or less of free fatty acids.

5. A process for the production of biodiesel from an oil or a fat comprising triglycerides and free fatty acids, the process comprising the step of:

(a) hydrolyzing said triglycerides of said oil or fat ;

(b) mixing said oil or fat comprising hydrolyzed triglycerides with an alcohol, a liquid acid catalyst and a reticulated hydrophilic solid, thereby forming a mixture; and

(c) heating said mixture at a temperature between about 20⁰C and about 150⁰C, thereby producing biodiesel.

6. The process of claim 4 wherein said oil or fat comprises about 25% by weight or more of free fatty acids.

7. The process of claim 6 wherein said oil or fat comprises about 40% by weight or more of free fatty acids.

8. The process any one of claims 1 to 7 wherein said reticulated hydrophilic solid is neutral.

9. The process any one of claims 1 to 8 wherein said reticulated hydrophilic solid is a silica gel, a zeolite, or mixtures thereof.

10. The process of any one of claims 1 to 9 wherein said reticulated hydrophilic solid is a silica gel.

11. The process of any one of claims 1 to 9 wherein said reticulated hydrophiiic solid is a zeolite.

12. The process of any one of claims 9 to 11 wherein said silica gel or said zeolite comprise non-acidic chemically reactive groups.

13. The process of claim 9 or 11 wherein said zeolite is modified by an alkylsilane.

14. The process of claim 9 or 11 wherein said zeolite is impregnated by non-acidic organic or inorganic molecules.

15. The process of any one of claims 1 to 14 wherein said reticulated hydrophilic solid is granular or in form of beads.

16. The process any one of claim 1 to 15 wherein said mixture comprises about 0.1 % by weight, relative to the weight of said oil or fat, or more of said reticulated hydrophilic solid.

17. The process of claim 16 wherein said mixture comprises about 1 % by weight, relative to the weight of said oil or fat, or more of said reticulated hydrophilic solid.

18. The process of any one of claims 1 to 17 wherein said temperature is between about room temperature and about a boiling point of said alcohol.

19. The process of any one of claims 1 to 18 wherein a ratio of said alcohol to said free fatty acids in said mixture is between about 3:1 and about 50:1.

20. The process of any one of claims 1 to 19 wherein said alcohol is methanol, ethanol, propanol, butanol or mixtures thereof.

21. The process of claim 20 wherein said alcohol is methanol.

22. The process of any one of claims 1 to 21 wherein said liquid acid catalyst is sulfuric acid, hydrochloric acid, phosphoric acid or mixtures thereof.

23. The process of any one of claims 1 to 22 wherein said oil or fat is soap stock, beef tallow, coconut oil, corn oil, cottonseed oil, lard, olive oil, palm oil, palm kernel oil, peanut oil, soybean oil, linseed oil, tung oil, sunflower oil, safflower oil, canola oil, rapeseed oil, sesame oil, babassu oil, perilla oil, oiticica oil, fish oils, menhaden oil, castor oil, Chinese tallow tree oil, Physic nut oil, Cuphea seed oil, microalgal oils, bacterial oils, fungal oils, grease trap residues or mixture thereof.

24. An oil or fat comprising esterified free fatty acids produced by the process of claim 1.

25. A reactor for esterifying free fatty acids comprised in an oil or a fat, the reactor comprising:

(a) a chamber containing a reticulated hydrophilic solid, said chamber having an inlet for introducing reactants into said chamber, said reactants comprising the oil or fat, an alcohol and a liquid acid catalyst, and having an outlet for recovering said reactants;

(b) means for contacting said reactants with said reticulated hydrophilic solid; and

(c) means for maintaining said chamber at one or more predetermined temperatures.

26. The reactor of claim 25 wherein said contacting means include means for conveying said reactants from said inlet to said outlet through said reticulated hydrophilic solid.

27. The reactor of claim 25 or 26 wherein said chamber is an elongated chamber having a first and a second end and wherein said inlet is located at said first end and said outlet is located at said second end.

28. The reactor of 27 wherein said elongated chamber is a tube.

29. The reactor of any one of claims 26 to 28 wherein said means for conveying the mixture is a pump.

30. The reactor of any one of claims 25 to 29 wherein said means for maintaining said chamber at said predetermined temperature is a thermostated bath or a thermostated oven.

31. The reactor of any one of claims 25 to 30 wherein said oil or fat, alcohol and liquid acid catalyst are mixed together prior to being introduced in the chamber.

32. The reactor of any one of claims 25 to 31 , wherein said reactor is operated in continuous mode.

33. The reactor of any one of claims 25 to 31 , wherein said reactor is operated in batch mode.

34. The reactor of any one of claims 25 to 33, wherein the oil or fat comprises triglycerides that have been hydrolysed prior to said oil or fat being introduced in the chamber.

35. The reactor of any one of claims 25 to 34 further comprising means for maintaining the reticulated hydrophilic solid inside the chamber while allowing passage of the reactants through the outlet.