Mixed alkoxide catalyst for biodiesel production

Abstract

A process is provided for producing fatty acid C1-C4-alkyl esters useful as biofuels from an organic oil source wherein the oil source contains triglycerides and free fatty acids in an amount of at least 0.1 wt% based on the total weight of the organic oil source, the process comprises a) reacting an organic oil source with a C1-C4-alkanol in the presence of a basic catalyst to form an ester phase and a glycerol phase; and b) separating the fatty acid C1-C4-alkyl ester from the ester phase; wherein the basic catalyst is a mixture of metal alkoxides.

Description

[0001] The present invention relates to a process for producing fatty acid C1-C4-alkyl esters from an organic oil source containing triglycerides and free fatty acids in the presence of a metal alkoxide mixture as catalyst. In addition, the present invention relates to the use of the mixture as a transesterification catalyst for the production of biodiesel and to the use of the fatty acid C1-C4-alkyl esters obtainable by the process as biofuels, preferably as biodiesel. Background Art

[0002] Fatty acid esters of monovalent alkyl alcohols are used in multipurpose applications both as raw materials and as intermediate products in the chemical and pharmaceutical industries, in the food processing industry and in the fuel industry.

[0003] Biodiesel, either pure or as a blending component, serves as

[0004] A renewable alternative to fossil fuels in the transport sector, helping to reduce greenhouse gas emissions. Biodiesel can be made from oils and fats produced by various organisms of plant and animal origin. The most commonly used oils come from rapeseed, canola, soy, oil palm or sunflower, but recycled grease or animal fats can also be used as feedstock.

[0005] Biodiesel is mainly produced from vegetable oils or fats by transesterifying triglycerides in the oils or fats with excess lower alcohols in the presence of a basic catalyst to produce fatty acid alkyl esters (FAAE) (mainly fatty acid methyl esters (FAME)) that can be used as biodiesel and glycerol as a by-product. The fatty acid alkyl esters and glycerol are separated, for example, by phase separation, and the lighter phase containing the crude biodiesel is purified from the alcohol and the catalyst.

[0006] Primarily, two-step process improvements for the transesterification step in biodiesel production are known.

[0007] WO 91 / 05034 A1 discloses a continuous two-step process for preparing methyl esters by reacting fatty acid triglycerides having a fatty acid content of <1 wt. %, in particular from deacidified rapeseed oil, at a temperature of 75° C. and a pressure of 3 bar in the presence of sodium methoxide (NaOMe). The reaction is carried out in a tubular reactor at a flow rate of Reynolds number 2700. After two steps, a conversion of 98% is described.

[0008] US 5,354,878 A discloses a continuous multi-stage process for catalytic transesterification, which comprises, inter alia, a step of introducing a mixture of oil, alcohol and alkaline catalyst at the top of a reactor column at a flow rate lower than the settling rate of glycerol, a step of further reaction in a stirred reactor, a step of washing with a hot extraction solution and a step of drying. This process is also known as the CD process (catalytic distillation).

[0009] WO 2008 / 034485 A1 discloses a continuous multistage process for catalytic transesterification, in which the yield of fatty acid methyl esters can be increased by transferring the crude fatty acid methyl esters after acid water washing to a further separator, in which the fatty acid methyl ester phase is dried and the remaining aqueous phase comprising additional fatty acid methyl esters is mixed with the previously removed heavy phase and subjected to a further separation stage, resulting in a phase containing fatty acid methyl esters and a phase containing glycerol and methanol, which is separated in a rectification column into crude glycerol and methanol, which can be fed into the methanol supply. Yield increases of up to 2% are described.

[0010] The overall yield of biodiesel production from fats and oils should be high. Increased yield is a very important criterion, since the raw material cost is a relevant part of the total production cost. Therefore, waste raw materials (like recycled grease or animal fats) that usually contain different amounts of free fatty acids (FFA) can also be possible raw materials.

[0011] However, the presence of free fatty acids often leads to disadvantages in the interesterification or separation stages. Therefore, FFA-containing oils or fats are often pretreated in an additional step to reduce the FFA content to a minimum.

[0012] For example, EP 1889899 A1 discloses a process for producing biodiesel starting from a high free fatty acid feedstock by converting the feedstock into glycerides, wherein the free fatty acid content can be reduced to 0.5 wt%, and subsequently reacting the glycerides with KOH and methanol to produce fatty acid methyl esters and glycerol.

[0013] In addition, the characteristics of the catalyst (e.g., type, formulation or concentration) usually affect biodiesel yield and oil / fat conversion. The most commonly used basic catalysts are NaOH, KOH, NaOMe or KOMe. However, for example, when free fatty acids are present in oil or fat or when using OH-containing catalysts, utilizing basic catalysts may require higher amounts or may cause undesirable soap formation.

[0014] WO 2008 / 115806 A1 discloses a method for transesterification of glycerides with alcohols in the presence of a base catalyst comprising an alkali metal salt of glycerol. The glycerol salt may be used as a catalyst or may be further reacted with a lower alcohol to provide a basic metal oxide, which may be used as a mixture containing a basic metal alkoxide and glycerol.

[0015] US2012 / 0066965 A1 discloses a method for transesterification of glycerides with alcohols in the presence of a multicomponent catalyst comprising a catalyst and an activator (e.g., a solution comprising NaOMe as a catalyst and KOMe as an activator). It is described that, compared with a NaOMe solution, in the case of a mixture with a NaOMe:KOMe molar ratio of 92:8 and 89:11, the phase separation of algae oil after stirring can be faster.

[0016] A. Singh et al., Applied Engineering in Agriculture, 22(4), 2006, 597-600 describe that methoxide catalysts lead to better biodiesel yields than hydroxide catalysts, and KOMe performs better than NaOMe. Methanolate catalysts not only accelerate the reaction, but also improve the conversion balance. K-based catalysts lead to higher soap formation than corresponding Na-based catalysts, with NaOMe performing better than NaOH. Based on statistically optimized operating conditions, biodiesel derived from canola oil with an acid value of 1.97 mg KOH / g can be obtained using KOMe as a catalyst at 0.2 mol / mol (1.59 wt%), 50°C, 240 rpm for 10 min and at a methanol:oil molar ratio of 4.5:1 with a yield of 95.8% and a soap formation of 0.75 wt%.

[0017] G. Vicente et al., Bioresource Technology 92, 2004, 297-305 describe that biodiesel derived from sunflower oil with an acid value of 0.45 mg KOH / g can be obtained using 1 wt % of NaOMe or KOMe, respectively, at 65° C. and a methanol:oil molar ratio of 6:1 under effective stirring for 4 hours with a yield of about 98%-99%.

[0018] Therefore, an important factor may also be the kinetics of the reaction. K- and Na-based catalysts generally work equally fast with effective stirring for a longer period of time. However, biodiesel production is often carried out on an industrial scale, where the mixing of the reactants generally determines the reaction rate rather than the efficiency of the catalyst.

[0019] While biodiesel offers many benefits, biodiesel production must be economical in order to maintain the supply of advanced biofuels. Producers must adapt to changing market conditions and adopt new methods for converting low-cost feedstocks while meeting strict product quality specifications.

[0020] Therefore, there remains a need for efficient catalytic systems for the transesterification of any kind of organic oils or fats for the production of biodiesel.

[0021] It was therefore an object of the present invention to provide a process for producing biodiesel using an efficient catalytic system, in particular in an economical manner, whereby the transesterification step should be completed as far as possible.

[0022] Furthermore, it was an object to provide an efficient catalytic system suitable for the transesterification step in the production of biodiesel. Summary of the invention

[0023] It has now been found that mixtures of alkali metal alkoxides can improve the conversion of organic oil or fat sources, particularly low cost feedstocks, in a process for the production of biodiesel.

[0024] Thus, in a first aspect, the present invention relates to a process for producing C1-C4-alkyl fatty acid esters from an organic oil source, wherein the oil source contains triglycerides and free fatty acids in an amount of at least 0.1 wt. % based on the total weight of the organic oil source, the process comprising

[0025] a) reacting an organic oil source with a C1-C4-alkanol in the presence of a basic catalyst to form an ester phase and a glycerol phase; and

[0026] b) separating the fatty acid C1-C4-alkyl esters from the ester phase;

[0027] The alkaline catalyst is a mixture of metal alkoxides.

[0028] In a further aspect, the invention relates to the use of a mixture of metal alkoxides as defined in any aspect herein as a transesterification catalyst for increasing the conversion in a process for producing C1-C4-alkyl fatty acid esters, preferably in a process for producing biofuels, especially biodiesel.

[0029] In a further aspect, the present invention relates to the use of a fatty acid C1-C4-alkyl ester obtainable by a process as defined in any aspect herein as a biofuel, preferably as biodiesel. DETAILED DESCRIPTION

[0030] As used herein, the indefinite article "a / kind" includes the singular and also includes the plural, that is, the indefinite article for a component of a composition means that the component is a single compound or a plurality of compounds. If not otherwise stated, the indefinite article "a / kind" and the expression "at least one / kind" are used synonymously.

[0031] In step a), transesterification is carried out with C1-C4-alkanols to produce fatty acid alkyl esters. Transesterification of fatty acid glycerides to produce lower alkyl glycerides is

[0032] Typically, transesterification is carried out in the presence of a basic catalyst.

[0033] The alcohol used in the inventive method generally depends on the type of fatty acid alkyl ester to be prepared. Suitable examples of C1-C4-alkanols include methanol, ethanol, n-propyl alcohol, 2-propyl alcohol, n-butyl alcohol, 2-butyl alcohol and the tert-butyl alcohol. A mixture of two or more alcohols may also be used.

[0034] Preferably, methanol or ethanol or a mixture thereof is used. More preferably, methanol or ethanol is used. In particular, methanol is used.

[0035] Therefore, in a preferred aspect, the present invention relates to a process for producing fatty acid C1-C4-alkyl esters from an organic oil source, wherein the C1-C4-alkanol is methanol, ethanol or a mixture thereof, preferably methanol.

[0036] The C1 -C4 -alkanols are advantageously used in their anhydrous form.

[0037] The basic catalyst used in the method of the present invention is a mixture of alkali metal alkoxides, such as a mixture of NaOMe and KOMe or a mixture of NaOEt and KOEt. Preferably, the mixture of alkali metal alkoxides is a mixture of NaOMe and KOMe.

[0038] Thus, in a preferred aspect, the present invention relates to a process for the production of C1-C4-alkyl fatty acid esters from an organic oil source, wherein the mixture of alkali metal alkoxides is a mixture of NaOMe and KOMe.

[0039] The molar ratio of NaOMe to KOMe can vary within a wide range. The molar amount of NaOMe is at least 1 mol%, preferably at least 5 mol%, more preferably at least 20 mol%, based on 1 mol of the mixture of NaOMe and KOMe.

[0040] Preferably, the molar ratio of NaOMe:KOMe in the mixture of alkali metal alkoxides is from 0.01:0.99 to 0.99:0.01, especially from 0.05:0.95 to 0.95:0.05. A further preferred range is from 0.10:0.90 to 0.90:0.10, especially from 0.20:0.80 to 0.80:0.20.

[0041] Therefore, in a preferred aspect, the present invention relates to a process for producing fatty acid C1-C4-alkyl esters from an organic oil source, wherein the molar ratio of NaOMe:KOMe in the mixture of alkali metal alkoxides is from 0.01:0.99 to 0.99:0.01, preferably from 0.05:0.95 to 0.95:0.05.

[0042] The basic catalyst may be added to the organic oil source as a solid, but preferably as a solution in a suitable solvent, preferably in an anhydrous C1-C4-alkanol, preferably in methanol, ethanol or a mixture thereof. The basic catalyst is preferably obtained by mixing a solution of NaOMe in a C1-C4-alkanol and a solution of KOMe in a C1-C4-alkanol. Each solution typically has a concentration of 1 wt% to 50 wt%, based on the total weight of the solution.

[0043] More preferably, the basic catalyst is applied, in particular as a solution in methanol, preferably anhydrous methanol.

[0044] Therefore, in a preferred aspect, the present invention relates to a process for producing fatty acid C1-C4-alkyl esters from an organic oil source, wherein the basic catalyst is used as a solution in a C1-C4-alkanol, preferably methanol, ethanol or a mixture thereof, in particular methanol.

[0045] The solution of the basic catalyst in C1-C4-alkanol, preferably methanol, may contain the basic catalyst in an amount of 1 wt % to 50 wt %, preferably 2 wt % to 50 wt %, based on the total weight of the solution in C1-C4-alkanol. The amount of alcohol introduced in this way is included in the total amount of C1-C4-alkanol used in step a).

[0046] Depending on the type and amount of alcohol used, the fatty acid C1-C4-alkyl ester produced by the process of the present invention is preferably a fatty acid methyl ester (FAME) or a fatty acid ethyl ester (FAEA) or a mixture thereof. More preferably, a fatty acid methyl ester is produced by the process of the present invention.

[0047] Therefore, in a further preferred aspect, the present invention relates to a process for producing fatty acid C1-C4-alkyl esters from an organic oil source, wherein the alkaline catalyst is used as a solution in a C1-C4-alkanol, preferably as a solution in methanol, more preferably as a solution in anhydrous methanol, with a concentration of 1 wt % to 50 wt %, based on the total weight of the solution.

[0048] Preferably, the alkaline catalyst is used as a solution in a C1-C4-alkanol with a concentration of 1 wt % to 50 wt %, based on the total weight of the solution, preferably as a solution in methanol, preferably anhydrous methanol, with a concentration of 1 wt % to 50 wt %, preferably 2 wt % to 50 wt %, based on the total weight of the solution.

[0049] In particular, the present invention relates to a process for producing fatty acid C1-C4-alkyl esters from an organic oil source, wherein the fatty acid C1-C4-alkyl esters are fatty acid methyl esters (FAME) and the basic catalyst is used as a solution in methanol, preferably anhydrous methanol, with a concentration of 1 wt% to 50 wt%, preferably 2 wt% to 50 wt%.

[0050] Based on the total weight of the triglyceride or organic oil source, preferably based on the total weight of the triglyceride, the amount of the alkaline catalyst may generally be in the range of 0.1 wt% to 8 wt%. More preferably, based on the total weight of the triglyceride, the amount of the alkaline catalyst is in the range of 0.1 wt% to 6 wt%, especially 0.1 wt% to 5 wt%, especially 0.1 wt% to 4 wt%.

[0051] Usually, the amount of free fatty acids is higher, the amount of alkaline catalyst is higher, because alkaline catalyst is partly used for neutralizing free fatty acids.Therefore, based on the gross weight of triglyceride or organic oil source, the amount of active alkaline catalyst can be lower than 8wt%.Term " amount of active alkaline catalyst " as used herein means the required amount of catalysis process of producing fatty acid C1-C4-alkyl ester by organic oil source, does not include the required amount of neutralizing the content of free fatty acids.

[0052] Therefore, in a further preferred aspect, the present invention relates to a process for producing fatty acid C1-C4-alkyl esters from an organic oil source, wherein the alkaline catalyst is used in an amount of 0.1 wt% to 8 wt%, preferably 0.1 wt% to 6 wt%, in particular 0.1 wt% to 5 wt%, based on the total weight of the triglycerides.

[0053] Especially preferred is a process for producing fatty acid C1-C4-alkyl esters from an organic oil source, wherein the active basic catalyst is used in an amount of 0.1 wt% to 5 wt%, preferably 0.1 wt% to 3 wt%, based on the total weight of the triglycerides.

[0054] The C1-C4-alkanol present in step a) can be used in an equimolar amount required for the transesterification of the triglycerides contained in the organic oil source, but can preferably be used in excess relative to the triglycerides contained in the organic oil source. The amount of C1-C4-alkanol can be at least 3 mol and up to about 20 mol based on 1 mol of triglycerides in the organic oil source. Preferably, the amount of C1-C4-alkanol can be at least 4 mol to 15 mol based on 1 mol of triglycerides in the organic oil source.

[0055] Therefore, in a further preferred aspect, the present invention relates to a process for producing C1-C4-alkyl fatty acid esters from an organic oil source, wherein the molar ratio of C1-C4-alkanol to triglycerides of the organic oil source is 3:1 to 20:1, preferably 4:1 to 15:1.

[0056] The total amount of C1-C4-alkanol used in step a) generally includes the amount of C1-C4-alkanol used as solvent for the basic catalyst.

[0057] In particular, the molar ratio of methanol to triglycerides of organic oil origin is 3:1 to 20:1, preferably 4:1 to 15:1.

[0058] The starting material in the method for producing fatty acid alkyl esters can be any triglyceride-containing raw material from any source, typically an organic oil source. Compared with mineral oil, organic oil is produced by plants, animals and other organisms through natural metabolic processes, and is based on triglycerides. The term "organic oil source" should be understood to include organic oils, like vegetable oils and animal oils, especially vegetable oils, but also includes any other mixtures, by-products or fractions of organic oils containing at least one free fatty acid (FFA) and suitable for producing biofuels, preferably biodiesel. The term "organic oil source" also includes fats that are solid at room temperature but are liquid at the reaction temperature in step a) of the method of the present invention.

[0059] Organic oil sources typically contain varying amounts of different types of free fatty acids as well as fatty acids bound as triglycerides.

[0060] Organic oil sources include vegetable and animal oils and fats. Vegetable oils are usually obtained by extraction from seeds with the aid of solvents or pressure, while animal fats are obtained by thermal extraction in autoclaves or with the aid of solvents. Typically, these fatty substances contain free fatty acids, sterols, phospholipids, water, odorous substances and other impurities. The refining of fatty substances involves the complete removal of almost all impurities (including free fatty acids) so that they can be used in the production of biodiesel, in food, and in industry.

[0061] Refined vegetable and animal oils and fats typically show very low FFA content, usually less than 0.5wt% or less than 0.1wt% based on the total weight of the refined vegetable and animal oils and fats. However, during the use of these refined oils and fats, the FFA content usually increases. Used or recycled oils typically contain different amounts of free fatty acids.

[0062] The method of the present invention can be applied to any organic oil source, the amount of free fatty acids in the organic oil source is at least 0.1wt%, preferably at least 0.2wt% or at least 0.3wt%, more preferably at least 0.4wt%, most preferably at least 0.5wt%, especially at least 0.6wt%, 0.7wt% or 0.8wt% based on the total weight of the organic oil source. The method of the present invention can be applied to any organic oil source, the amount of free fatty acids in the organic oil source is at most 12wt%, preferably at most 10wt%, more preferably at most 9wt%, especially at most 8wt% based on the total weight of the organic oil source.

[0063] Therefore, in a further preferred aspect, the present invention relates to a process for producing C1-C4-alkyl fatty acid esters from an organic oil source, wherein the amount of free fatty acids is at least 0.2 wt%, preferably at least 0.3 wt%, more preferably 0.3 wt% to 10 wt% or 0.5 wt% to 10 wt%, in particular 0.3 wt% to 9 wt% or 0.5 wt% to 8 wt% or 0.5 wt% to 7 wt%, based on the total weight of the organic oil source.

[0064] A further preferred range of the amount of free fatty acids is 0.7 wt% to 10 wt%, preferably 0.7 wt% to 9 wt%, more preferably 0.7 wt% to 8 wt%, based on the total weight of the organic oil source.

[0065] The organic oil source may be a natural or synthetic oil and / or fat, preferably derived from a vegetable oil.

[0066] The term "synthetic oil and / or fat" as used herein includes any oil or fat derived from an organic oil source, wherein triglycerides are obtained by subjecting free fatty acids present in the organic oil source, preferably in substantial amounts, to a reaction with glycerol, or by subjecting mono- or diglycerides present in the organic oil source, preferably in substantial amounts, to a reaction with fatty acids present in the organic oil source.

[0067] Thus, synthetic oils and fats may contain used vegetable and / or animal oils and / or fats or refined vegetable and / or animal oils and / or fats.

[0068] Therefore, in a further preferred aspect, the present invention relates to a process for producing fatty acid C1-C4-alkyl esters from an organic oil source, wherein the organic oil source is derived from natural or synthetic oils and / or fats, preferably derived from vegetable oils.

[0069] The organic oil source may be any refined vegetable and / or animal oil and / or fat or any used vegetable and / or animal oil and / or fat.

[0070] As used herein, the term "used vegetable and / or animal oils and / or fats" means used cooking oil (UCO), also known as recycled oil, waste oil or yellow grease. Used cooking oil is recovered from businesses and industries that use the oil for cooking.

[0071] Preferably, the organic oil source contains used vegetable and / or animal oils and / or fats.

[0072] Other organic oil sources include plant

[0073] By-products of the chemical and physical refining of animal oils and / or fats, by-products of the refining of glycerol from biodiesel, fatty acids from distilled and non-distilled, fatty substances from hydrolytic cracking, trap grease and distilled and non-distilled fatty acids resulting from the cracking of soaps.

[0074] Mixtures of the above organic oil sources are also contemplated and may be used in the methods of the present invention.

[0075] Therefore, in a preferred aspect, the present invention relates to a process for producing C1-C4-alkyl fatty acid esters from an organic oil source, wherein the organic oil source is derived from used vegetable and / or animal oils and / or fats, by-products of the chemical and physical refining of vegetable and / or animal oils and / or fats, by-products of the refining of glycerol from biodiesel, from distilled and non-distilled fatty acids, trapped grease, hydrolytically cracked fatty substances and distilled and non-distilled fatty acids resulting from the cracking of soaps, or mixtures thereof.

[0076] Preferably, the organic oil source is derived from a plant organic oil source.

[0077] Therefore, in a preferred aspect, the present invention relates to a process for producing fatty acid C1-C4-alkyl esters from an organic oil source, wherein the organic oil source is derived from spent vegetable oils or by-products of the chemical and physical refining of vegetable oils.

[0078] In a more preferred aspect, the present invention relates to a method for producing C1-C4-alkyl fatty acid esters from an organic oil source, wherein the vegetable oil is an oil selected from the group consisting of coconut oil, corn oil, cottonseed oil, olive oil, palm oil, peanut oil, rapeseed oil, safflower oil, sesame oil, soybean oil, sunflower oil, and any combination thereof.

[0079] In particular, the vegetable oil is an oil selected from the group consisting of coconut oil, palm oil, rapeseed oil, soybean oil and any combination thereof.

[0080] In addition, the preferred organic oil source is palm fatty acid distillate (PFAD) or palm sludge oil (PSO). PAFD is a fatty acid distillate obtained during the refining of palm oil.

[0081] A lower value by-product from the acid removal and deodorization stages. PFAD is often used as an industrial fat for non-food applications.

[0082] The source of the acid is sold. Palm sludge oil (PSO) is the undistilled residue of palm oil production and is of inferior quality compared to PFAD.

[0083] Free fatty acids can be any fatty acids bound in triglycerides of an organic oil source, for example in naturally occurring form or as structural isomers obtained through the use of refined oils or fats, such as trans fatty acids.

[0084] Preferably, the fatty acid is at least one free fatty acid selected from the group consisting of caprylic acid, capric acid, lauric acid, myristic acid, palmitic acid, stearic acid, arachidic acid, behenic acid, lignoceric acid, cerotic acid, myristic acid, palmitoleic acid, oleic acid, elaidic acid, vaccenic acid, linoleic acid, trans-linoleic acid, linolenic acid, arachidonic acid, eicosapentaenoic acid, erucic acid and docosahexaenoic acid, preferably, the free fatty acid is selected from the group consisting of oleic acid, palmitic acid, linoleic acid, lauric acid and any combination thereof.

[0085] Therefore, in a preferred aspect, the present invention relates to a method for producing C1-C4-alkyl esters of fatty acids from an organic oil source, wherein the free fatty acid is at least one fatty acid selected from the group consisting of caprylic acid, capric acid, lauric acid, myristic acid, palmitic acid, stearic acid, arachidic acid, behenic acid, lignoceric acid, cerotic acid, myristic acid, palmitoleic acid, oleic acid, elaidic acid, vaccenic acid, linoleic acid, trans-linoleic acid, linolenic acid, arachidonic acid, eicosapentaenoic acid, erucic acid and docosahexaenoic acid, preferably, the free fatty acid is selected from the group consisting of oleic acid, palmitic acid, linoleic acid, lauric acid and any combination thereof.

[0086] Pre-treating the organic oil source may be appropriate in cases where the organic oil source is contaminated with gums, odorous or intractable materials, or is dark in color.

[0087] Before the organic oil source is used in step a) of the method for producing fatty acid C1-C4-alkyl esters, the organic oil source may be pretreated to remove impurities, for example in one or more steps. The pretreatment step may be carried out by methods known in the art for producing biodiesel. The pretreatment step may include at least one step of degumming, bleaching, removing insoluble impurities or drying. The steps applied generally depend on the type of the organic oil source. These steps may be carried out in any order.

[0088] The organic oil source may be subjected to a degumming step, typically to remove phospholipids, for example using phosphoric acid and steam, preferably followed by separation of the aqueous phase by centrifugation.

[0089] The organic oil source may also be subjected to a bleaching step, for example using thermal bleaching or clay bleaching.

[0090] The organic oil source may also be subjected to a drying step, for example using heat and / or vacuum.The moisture content of the organic oil source may generally be reduced to an amount of 0.05 wt% or less based on the total weight of the organic oil source.

[0091] Additionally, the organic oil source may be purified from insoluble impurities, for example by filtration (eg, using a polishing filter).

[0092] Therefore, in a preferred aspect, the present invention relates to a process for producing C1-C4-alkyl fatty acid esters from an organic oil source, wherein the organic oil source is subjected to at least one step selected from degumming, bleaching, drying, filtering and any combination thereof before step a).

[0093] Optionally, the method may comprise the step of partially removing free fatty acids, preferably to an amount of up to 12 wt%, more preferably to an amount of up to 10 wt%, especially to an amount of up to 8 wt% or 7 wt%, based on the total weight of the organic oil source.

[0094] Methods for removing free fatty acids are known in the art. For example, this can be achieved by stripping with glycerol or esterification to the desired free fatty acid content.

[0095] Preferably, the organic oil source used in the process of the present invention already has free fatty acids in an amount of 0.1 wt% to 12 wt%, preferably 0.2 wt% to 12 wt%, more preferably 0.3 wt% to 10 wt%, especially 0.3 wt% to 8 wt%, in particular 0.5 wt% to 8 wt% or 0.5 wt% to 7 wt%, based on the total weight of the organic oil source.

[0096] Step a) defines a step of reacting an organic oil source with a C1-C4-alkanol in the presence of a basic catalyst to form an ester phase and a glycerol phase.

[0097] Reaction step a) generally begins when all three components are exposed to one another.

[0098] Step a) can be carried out in any container suitable for transesterification reaction and phase separation, for example in a reactor or tank. The addition of the three components (C1-C4-alkanol, alkaline catalyst and organic oil source) can be carried out in any known manner suitable for transesterification reaction.

[0099] Step a) preferably comprises the following steps:

[0100] a1) adding an organic oil source, a C1-C4-alkanol and a basic catalyst into a container,

[0101] a2) mixing an organic oil source, a C1-C4-alkanol and a basic catalyst, and

[0102] a3) allowing the mixture obtained in step a1) and step a2) to react.

[0103] Therefore, in a preferred aspect, the present invention relates to a process for producing fatty acid C1-C4-alkyl esters from an organic oil source, wherein step a) comprises the following steps:

[0104] a1) adding an organic oil source, a C1-C4-alkanol and a basic catalyst into a container,

[0105] a2) mixing an organic oil source, a C1-C4-alkanol and a basic catalyst, and

[0106] a3) allowing the mixture obtained in step a1) and step a2) to react.

[0107] Steps a1) and a2) can be performed simultaneously, partially simultaneously or in any order. Step a1) can be performed before step a2), or step a2) can be performed before step a1).

[0108] The term "mixing" as used herein for step a2) means contacting the three components to start the transesterification reaction. Mixing can be performed by using any suitable device or by using gravity or thermal convection, for example by simply filling the components to the upper part of the container, or by stirring.

[0109] Examples of mixing devices include pumps, static mixers and stirrers, with pumps being preferred.

[0110] As used herein, the term "partially simultaneously" means that two components are premixed and added to a third component already in a container, preferably a mixture M2a as defined below.

[0111] The C1-C4-alkanol, alkaline catalyst and organic oil source may be added to the vessel in any order or in parallel as separate components or as a mixture of any combination of the three components.

[0112] The mixture of two or all components of the C1-C4-alkanol, the basic catalyst and the organic oil source can be obtained by any kind of contacting of the components, preferably by mixing.

[0113] The mixture M1 may comprise all three components, which are brought into contact, preferably premixed by any conventional mixing means (eg in a pump, static mixer or stirrer), and added to the container.

[0114] The mixture M2 may comprise a C1-C4-alkanol and a basic catalyst, wherein at least 10 wt.-%, preferably at least 50 wt.-%, more preferably at least 90 wt.-%, in particular at least 95 wt.-%, in particular the entire amount (= mixture M2a) of the C1-C4-alkanol, based on the total weight of the C1-C4-alkanol used in step a), is present in the mixture M2.

[0115] The mixture M3 may comprise C1-C4-alkanol and an organic oil source, wherein ≤90 wt.-%, preferably ≤50 wt.-%, in particular ≤10 wt.-%, and in particular ≤5 wt.-% of C1-C4-alkanol, based on the total weight of the C1-C4-alkanol used in step a), is present in the mixture M3.

[0116] It is possible to use a mixture M2a and an organic oil source, wherein the mixture M2a contains the total amount of C1-C4-alkanol.

[0117] The mixture M2a is preferably a solution of a basic catalyst in ethanol, methanol or a mixture thereof, more preferably a solution of a basic catalyst in methanol (mixture M2a').

[0118] Alternatively, mixtures M2 and M3 can be used, each of which contains a portion of the amount of C1-C4-alkanol (mixtures M2b and M3b). Preferably, the weight ratio of C1-C4-alkanol in mixture M2b to C1-C4-alkanol in mixture M3b is from 0.01:0.99 to 0.99:0.01, preferably from 0.1:0.9 to 0.9:0.1.

[0119] Preferably, the mixture M2a (which contains the total amount of C1-C4-alkanol) and the organic oil source can be used, for example, in the following way:

[0120] i) adding the mixture M2a and the organic oil source separately to a container and mixing, preferably by initially charging the oil source into the container, adding the mixture M2a and mixing;

[0121] ii) adding the mixture M2a and the organic oil source in a premixed form into a container;

[0122] iii) adding the mixture M2a and the organic oil source separately and simultaneously; or

[0123] iv) Add and mix mixture M2a and the organic oil source simultaneously.

[0124] Further preferably, mixtures M2b and mixtures M3b, wherein each of mixtures M2b and M3b contains a portion of the amount of C1-C4-alkanol, can be used in this way, for example:

[0125] i) adding mixtures M2b and M3b separately to a container and mixing, preferably by initially charging mixture M3b to the container, adding mixture M2b and mixing;

[0126] ii) adding the mixtures M2b and M3b in premixed form to a container;

[0127] iii) adding mixtures M2b and M3b separately and simultaneously; or

[0128] iv) Add and mix mixtures M2b and M3b simultaneously.

[0129] Step a3) can be performed under mechanical agitation (like stirring) or under low or no agitation.

[0130] In a preferred embodiment, the majority of the reaction time of step a) of the process of the invention is preferably carried out under low or no agitation, preferably under substantially static reaction conditions. It is generally preferred to add the organic oil source, the C1-C4-alkanol and the alkaline catalyst, preferably the mixture M2a or M2a' and the organic oil source or the mixtures M2b and M3b in parallel at such flow rates that all components, preferably the mixture M2a and the organic oil source or the mixtures M2b and M3b, are completely added within the same period of time.

[0131] The addition of the components can be carried out by any suitable metering unit. In particular, the mixtures M2a, M2b, M3b and the organic oil source are usually supplied by using a suitable metering unit, preferably a pump.

[0132] The time period for supplying the organic oil source, C1-C4-alkanol and basic catalyst, preferably mixture M2a and organic oil source or mixtures M2b and M3b, to the vessel is generally much shorter than that normally carried out under substantially static reaction conditions.

[0133] Therefore, the reaction time of step a) includes the time period for adding the organic oil source, the C1-C4-alkanol and the basic catalyst, preferably the mixture M2a and the organic oil source or the mixture M2b and M3b, and the time period for reacting until the reaction is complete and two separate phases appear.

[0134] The term "substantially static reaction conditions" as used herein means that the mixture during step a) is allowed to react without mechanical energy input, preferably at a predetermined reaction temperature and reaction pressure.

[0135] When the mixing of the three components is carried out in a pump, the mixing time of the components can be very short, for example ≤30 sec, preferably ≤20 sec, more preferably ≤10 sec.

[0136] Substantially static reaction conditions correspond to mass transfer limited conditions.Mass transfer limited conditions occur when the diffusion rate of the reactants is lower than the reaction rate.

[0137] If step a3) is carried out under essentially static reaction conditions, the conversion rate of the transesterification reaction in step a) during the period of addition and mixing of the organic oil source, the C1-C4-alkanol and the basic catalyst, preferably the mixture M2a and the organic oil source or the mixture M2b and M3b, is generally at most 40%, preferably at most 35%, more preferably at most 30%, and in particular at most 25%, based on 100% conversion rate of the transesterification reaction.

[0138] Therefore, in a preferred aspect, the present invention relates to a process for producing fatty acid C1-C4-alkyl esters from an organic oil source, wherein in step a) a conversion of at least 60% based on 100% conversion is achieved under essentially static reaction conditions.

[0139] The term "conversion rate" as used herein means the percentage of the starting material (triglyceride) converted to the desired product (fatty acid C1-C4-alkyl ester) based on 100% conversion of the starting material.

[0140] As used herein, the term "100% conversion" means the theoretical conversion of the starting material.

[0141] Preferably, a conversion of at least 65%, more preferably at least 70%, in particular at least 75% is achieved in step a) under essentially static reaction conditions.

[0142] Therefore, in a preferred aspect, the present invention relates to a process for producing fatty acid C1-C4-alkyl esters from an organic oil source, wherein step a3) comprises allowing the mixture obtained in step a1) and step a2) to react under essentially static reaction conditions to form an ester phase and a glycerol phase.

[0143] Steps a1) and a2) can be performed simultaneously, partially simultaneously or in any order. Preferably, steps a1) and a2) are performed partially simultaneously, wherein in particular the mixture M2a and the organic oil source are added to the container simultaneously.

[0144] In another preferred embodiment, steps a2) and a3) are carried out under mechanical agitation, followed by the formation of an ester phase and a glycerol phase. Mechanical agitation can be carried out, for example, by stirring, wherein a conversion of at least 60%, preferably at least 80%, more preferably at least 90%, and in particular at least 95% based on 100% conversion can be achieved, as well as step a3). Mechanical agitation can be carried out by stirring, using, for example, a stirring speed of at least 300 rpm or more, for example in the range of 300 to 800 rpm, preferably 300 to 600 rpm. Phase separation into an ester phase and a glycerol phase typically occurs by allowing the mixture to stand, for example under static reaction conditions.

[0145] The time period for mechanical agitation can be up to 50%, preferably up to 40%, of the time period for phase separation. Compared to the time period for phase separation, the time period for mechanical agitation generally depends on the processing capacity, allowing sufficient phase separation, and can also be less than 40% or lower.

[0146] Thus, in a preferred aspect, the present invention relates to a process for producing fatty acid C1-C4-alkyl esters from an organic oil source, wherein steps a2) and a3) are carried out under mechanical agitation, with subsequent formation of an ester phase and a glycerol phase.

[0147] Typically, step a) of the inventive method can be carried out under different temperature and pressure conditions. Usually, the inventive method is carried out under mild temperature and pressure conditions. Usually, the inventive method can be carried out under air or inert conditions like nitrogen.

[0148] As used herein, pressure in bars means absolute pressure in bars.

[0149] Step a) may be carried out at a temperature of 20 to 100° C., preferably at a temperature of 30 to 80° C. Preferably, the reactor is preheated to the desired temperature.

[0150] Step a) may be carried out at a pressure of 1 to 10 bar, preferably 1 to 5 bar, more preferably 1 to 3 bar.

[0151] Therefore, in a preferred aspect, the present invention relates to a process for producing fatty acid C1-C4-alkyl esters from an organic oil source, wherein step a) is carried out at a temperature of 20 to 100°C, preferably 30 to 80°C.

[0152] Therefore, in a preferred aspect, the present invention relates to a process for producing fatty acid C1-C4-alkyl esters from an organic oil source, wherein step a) is carried out at a pressure of 1 to 10 bar, preferably 1 to 3 bar.

[0153] During the reaction in step a), a phase comprising fatty acid C1 -C4 -alkyl esters and a phase comprising glycerol are formed.

[0154] The reaction of step a) is generally complete when complete phase separation is achieved, generally when a liquid / liquid phase boundary of two substantially clear phases is formed. The upper phase is rich in fatty acid C1-C4-alkyl esters and the lower phase is rich in glycerol.

[0155] The reaction time of step a) generally varies with the production capacity.

[0156] The process of step a) may preferably be a batch process.

[0157] The reaction of step a) can be carried out in a container of any design suitable for transesterification reactions involving phase separation. For example, the container can be designed so that the two phases can be extracted through two outlets installed at different positions. The removal of the ester phase can be close to the filling level.

[0158] Typically, step b) of the process of the invention comprises a separation step of the resulting phase formed in step a) and a separation step of the fatty acid C1-C4-alkyl esters from the separated ester phase.

[0159] Therefore, in a preferred aspect, the present invention relates to a process for producing fatty acid C1-C4-alkyl esters from an organic oil source, wherein step b) comprises the following steps:

[0160] b1) separating the ester phase from the glycerol phase, and

[0161] b2) Separating the fatty acid C1-C4-alkyl esters from the ester phase.

[0162] Step b) can be carried out at the same temperature as applied in step a) or can be carried out at a lower temperature. The temperature can be suitably chosen so as to prevent any precipitation of the soap that may be formed, preferably the temperature is above room temperature (20-25°C), more preferably ≥30°C.

[0163] Step b) may comprise one or more separation steps b1).

[0164] The phase rich in fatty acid C1-C4-alkyl esters can be separated from the phase rich in glycerol by customary means, for example by extracting said phase from the reactor, by decanting, by centrifuging or by removing the glycerol-rich phase at a lower level, usually near the bottom of the reactor, preferably at the bottom of the reactor.

[0165] The separated phase enriched in fatty acid C1-C4-alkyl esters can be processed in a conventional manner to isolate fatty acid C1-C4-alkyl esters, preferably in purified form, for use as biodiesel that meets commercial product specifications, in particular meeting the requirements of DIN EN 14214 (2019) and ASTM D 6751.

[0166] The separated phase rich in fatty acid C1-C4-alkyl esters usually contains impurities, like residual alcohol, glycerol, small amounts of catalysts, salts and soaps, and is usually purified in one or more steps. The order and number of these steps can vary depending on the characteristics of the organic oil source, the pretreatment process, the transesterification step and economic feasibility.

[0167] For example, the separated phase containing fatty acid C1-C4-alkyl esters can be subjected to at least one step selected from washing with water, preferably deionized water, and / or treating with an acid (e.g. sulfuric acid), distillation, fractionation, drying under vacuum, filtering and any combination thereof.

[0168] The basic catalysts of the invention can be effectively used as transesterification catalysts, in particular for improving the conversion in processes for producing fatty acid C1-C4-alkyl esters, preferably in processes for producing biofuels, in particular biodiesel.

[0169] Therefore, in a further aspect, the present invention relates to the use of a mixture of metal alkoxides as defined in any aspect herein as a transesterification catalyst for increasing the conversion in a process for producing fatty acid C1-C4-alkyl esters, preferably in a process for producing biofuels, especially biodiesel.

[0170] A further aspect of the invention relates to a method for increasing the conversion in a process for producing C1-C4-alkyl fatty acid esters, preferably in a process for producing biofuels, especially biodiesel, wherein a mixture of metal alkoxides as defined in any aspect herein is used as transesterification catalyst.

[0171] Preferably, the term "increase conversion" means that the conversion is higher if compared to the theoretical value based on the linear relationship of the basic catalyst (mixture of NaOMe and KOMe) to the pure catalyst (NaOMe or KOMe).

[0172] Fatty acid alkyl esters can be used in many industrial applications, for example in the fuel industry.

[0173] Therefore, in a further aspect, the present invention relates to the use of a fatty acid C1-C4-alkyl ester obtainable by a process as defined in any aspect herein as a biofuel, preferably as biodiesel.

[0174] As used herein, the term "biofuel" refers to a fuel derived from a biological source. Non-limiting examples include biodiesel, jet fuel, diesel, jet fuel blendstocks, and diesel blendstocks.

[0175] As used herein, the term "biodiesel" means a biofuel that can be a diesel substitute derived from petroleum. Biodiesel can be used in combustion diesel engines in pure form (referred to as "neat" biodiesel) or as a blendstock with petroleum-based diesel at any concentration.

[0176] Because the basic catalyst of the present invention can function effectively, the process of the present invention enables the use of a wide range of oily or fat-containing feedstocks for the preparation of fatty acid alkyl esters, including low-quality, inexpensive feedstocks containing relatively low amounts of free fatty acids, such as used cooking oils.

[0177] The process of the invention can be carried out in a more economical manner, since the basic catalyst provides a lower cost compared to pure KOMe, but the effect is similar to and better than expected when the linear relationship of the basic catalyst to the pure catalyst is taken as the basis. Each percentage relates to a higher yield, which is important for an industrial-scale process.

[0178] Furthermore, the basic catalyst of the present invention can be used at a lower temperature than sodium methoxide.

[0179] Basic catalysts are easy to handle as liquid catalysts.

[0180] The catalyst of the invention allows easier separation of the salts formed than using pure sodium-containing catalysts, since potassium salts are more soluble than sodium salts.

[0181] After the transesterification in step a), phase separation can be easily performed since there is a sufficient density difference between the fatty acid alkyl ester phase and the glycerol / alkanol phase.

[0182] Preferably, the biodiesel obtained by the method of the present invention meets the requirements of DIN EN 14214 (2019) and ASTM D6751.

[0183] The preferences given for the process for producing C1-C4-alkyl fatty acid esters from an organic oil source also apply to the other objects of the present invention.

[0184] Unless otherwise indicated, all percentages, ppm or similar values ​​refer to weight relative to the total weight of the corresponding composition. The terms "% by weight" and "wt%" are used synonymously herein. All cited documents are incorporated herein by reference.

[0185] The following examples shall further illustrate the present invention without limiting the scope of the present invention.

[0186] Examples

[0187] Examples 1 to 4 and Comparative Examples 1 to 6

[0188] Used cooking oils: vegetable origin

[0189] Acid value <0.03mg KOH / g

[0190] Water content <200ppm

[0191] Triglyceride content>98wt%

[0192] Analysis of conversion: The upper phase obtained in the transesterification step was separated and analyzed by IR and NMR. The analysis by IR was carried out according to the method described in C. Baroi et al., Int. J. Chem. React. Eng. [International Journal of Chemical Reactor Engineering] 2009, 7, A72.

[0193] IR Perkin-Elmer Spectrum Two,MIRacle ATR

[0194] NMR Bruker Avance DRX 500

[0195] Example 1

[0196] A mixture of used cooking oil (170 g), oleic acid (1.7 g) and MeOH (20.4 g) was stirred (500 rpm) for 60 min and kept at 50° C. A premixed solution of NaOMe and KOMe (2.21 g NaOMe, 30 wt % solution in MeOH and 2.68 g KOMe, 32 wt % solution in MeOH; 50:50 molar ratio) was added in one portion and stirring was immediately stopped. The reaction mixture was kept at 50° C. for the indicated times.

[0197] Example 2

[0198] A mixture of used cooking oil (170 g), oleic acid (1.7 g) and MeOH (20.4 g) was stirred (500 rpm) for 60 min and kept at 50° C. A premixed solution of NaOMe and KOMe (4 g NaOMe, 30 wt % solution in MeOH and 0.54 g KOMe, 32 wt % solution in MeOH; 90:10 molar ratio) was added in one portion and stirring was immediately stopped. The reaction mixture was kept at 50° C. for the indicated time.

[0199] Example 3

[0200] A mixture of used cooking oil (170 g), oleic acid (1.7 g) and MeOH (20.4 g) was stirred (500 rpm) for 60 min and kept at 50° C. A premixed solution of NaOMe and KOMe (3.54 g NaOMe, 30 wt % solution in MeOH and 1.07 g KOMe, 32 wt % solution in MeOH; 80:20 molar ratio) was added in one portion and stirring was immediately stopped. The reaction mixture was kept at 50° C. for the indicated times.

[0201] Example 4

[0202] A mixture of used cooking oil (170 g), oleic acid (3.4 g) and MeOH (20.4 g) was stirred (500 rpm) for 60 min and kept at 50° C. A premixed solution of NaOMe and KOMe (2.21 g NaOMe, 30 wt % solution in MeOH and 2.68 g KOMe, 32 wt % solution in MeOH; 50:50 molar ratio) was added in one portion and stirring was immediately stopped. The reaction mixture was kept at 50° C. for the indicated times.

[0203] Comparative Example 1

[0204] A mixture of used cooking oil (170 g), oleic acid (1.7 g) and MeOH (20.4 g) was stirred (500 rpm) for 60 min and kept at 50° C. KOMe (5.36 g, 32 wt % solution in MeOH) was added in one portion and stirring was stopped immediately. The reaction mixture was kept at 50° C. for the indicated time.

[0205] Comparative Example 2

[0206] A mixture of used cooking oil (170 g), oleic acid (1.7 g) and MeOH (20.4 g) was stirred (500 rpm) and maintained at 50° C. NaOMe (4.42 g, 30 wt % solution in MeOH) was added in one portion and stirring was stopped immediately. The reaction mixture was maintained at 50° C. for the indicated time.

[0207] Comparative Example 3

[0208] A mixture of used cooking oil (170 g), oleic acid (3.4 g) and MeOH (20.4 g) was stirred (500 rpm) for 60 min and kept at 50° C. KOMe (5.36 g, 32 wt % solution in MeOH) was added in one portion and stirring was stopped immediately. The reaction mixture was kept at 50° C. for the indicated time.

[0209] Comparative Example 4

[0210] A mixture of used cooking oil (170 g), oleic acid (1.7 g) and MeOH (24 g) was stirred (500 rpm) for 60 min and kept at 50° C. NaOMe (4.4 g, 30 wt % solution in MeOH) was added in one portion and stirring was stopped immediately. The reaction mixture was kept at 50° C. for the indicated time. A precipitate of soap was formed.

[0211] Comparative Example 5

[0212] A mixture of used cooking oil (170 g) and MeOH (20.4 g) was stirred (500 rpm) for 60 min and kept at 50° C. KOMe (5.36 g, 32 wt % solution in MeOH) was added in one portion and stirring was stopped immediately. The reaction mixture was kept at 50° C. for the indicated time.

[0213] Comparative Example 6

[0214] A mixture of used cooking oil (170 g) and MeOH (20.4 g) was stirred (500 rpm) and maintained at 50° C. NaOMe (4.42 g, 30 wt % solution in MeOH) was added in one portion and stirring was immediately stopped. The reaction mixture was maintained at 50° C. for the indicated time.

[0215] The conversion rates of Examples 1 to 4 and Comparative Examples 1 to 6 after a predetermined period of time are listed in Table 1. Each conversion rate value has a variance of about ±0.5%.

[0216] Table 1

[0217]

[0218] The conversion of the base catalyst (mixture of NaOMe and KOMe) was better than expected at every ratio when the linear relationship of the base catalyst to the pure catalyst was taken as the basis. For example, the expected value for Example 1 was 94%.

[0219] Examples 5 to 8 and Comparative Examples 7 to 10

[0220] Vegetable oil: refined rapeseed oil

[0221] Acid value: 0.23mg KOH / g

[0222] Water content: 830ppm

[0223] Triglyceride content: 97wt%

[0224] Analysis of conversion rate: After 60 min of reaction (stirring time), a sample of the reaction mixture was taken and quenched by adding an aqueous solution of citric acid (10 wt %). After centrifugation (3500 rpm), the upper layer was separated and analyzed by GC. The analysis by GC was performed according to DIN EN 14105 (2020).

[0225] The soap content in FAME was determined via titration according to the method described in J. Van Gerpen et al., Biodiesel Analytical Methods August 2002-January 2004, NREL / SR-510-36240, 2004.

[0226] Gas chromatography (GC): Agilent GC6890N or GC7890A equipped with Agilent PTV SPTM Gang FTG (15m, 0.32 mm ID, 0.1 μm) or MXT Biodiesel TG Kap 15 (15m, 0.32 mm ID, 0.1 μm) columns.

[0227] Example 5

[0228] A mixture of vegetable oil (303.8 g) containing 5 wt% oleic acid and MeOH (43.3 g) was stirred (800 rpm) and heated to 60°C. A solution of a basic catalyst (KOMe:NaOMe 1:1 molar ratio, 16.6 g of a 31 wt% solution in MeOH) was added in one portion and stirring was continued for 60 min. The reaction mixture was transferred to a separatory funnel and kept at 40°C for 120 min. A sample of the upper layer was taken after the time for soap analysis.

[0229] Example 6

[0230] A mixture of vegetable oil (310.3 g) containing 5 wt% oleic acid and MeOH (43.7 g) was stirred (800 rpm) and heated to 60°C. A solution of a basic catalyst (KOMe:NaOMe 3:1 molar ratio, 17.7 g of a 31.5 wt% solution in MeOH) was added in one portion and stirring was continued for 60 min. The reaction mixture was transferred to a separatory funnel and kept at 40°C for 120 min. A sample of the upper layer was taken after the time for soap analysis.

[0231] Example 7

[0232] A mixture of vegetable oil (306.6 g) containing 5 wt% oleic acid and MeOH (43.8 g) was stirred (800 rpm) and heated to 50°C. A solution of a basic catalyst (KOMe:NaOMe 1:1 molar ratio, 16.8 g of a 31 wt% solution in MeOH) was added in one portion and stirring was continued for 60 min. The reaction mixture was transferred to a separatory funnel and kept at 40°C for 120 min. A sample of the upper layer was taken after the time for soap analysis.

[0233] Example 8

[0234] A mixture of vegetable oil (302.6 g) containing 5 wt% oleic acid and MeOH (42.6 g) was stirred (800 rpm) and heated to 50°C. A solution of a basic catalyst (KOMe:NaOMe 3:1 molar ratio, 17.3 g of a 31.5 wt% solution in MeOH) was added in one portion and stirring was continued for 60 min. The reaction mixture was transferred to a separatory funnel and kept at 40°C for 120 min. A sample of the upper layer was taken after the time for soap analysis.

[0235] Comparative Example 7

[0236] A mixture of vegetable oil (303.9 g) containing 5 wt% oleic acid and MeOH (42.3 g) was stirred (800 rpm) and heated to 60°C. A solution of KOMe (18.2 g of a 32 wt% solution in MeOH) was added in one portion and stirring was continued for 60 min. The reaction mixture was transferred to a separatory funnel and kept at 40°C for 120 min. A sample of the upper layer was taken after that time for soap analysis.

[0237] Comparative Example 8

[0238] A mixture of vegetable oil (309.6 g) containing 5 wt% oleic acid and MeOH (45.1 g) was stirred (800 rpm) and heated to 60° C. A solution of NaOMe (15.2 g of a 30 wt% solution in MeOH) was added in one portion and stirring was continued for 60 min. The reaction mixture was transferred to a separatory funnel and kept at 40° C. for 120 min. A sample of the upper layer was taken after the time for soap analysis.

[0239] Comparative Example 9

[0240] A mixture of vegetable oil (301.0 g) containing 5 wt% oleic acid and MeOH (52.0 g) was stirred (800 rpm) and heated to 50° C. A solution of KOMe (18.1 g of a 32 wt% solution in MeOH) was added in one portion and stirring was continued for 60 min. The reaction mixture was transferred to a separatory funnel and kept at 40° C. for 120 min. A sample of the upper layer was taken after that time for soap analysis.

[0241] Comparative Example 10

[0242] A mixture of vegetable oil (303.2 g) containing 5 wt% oleic acid and MeOH (44.1 g) was stirred (800 rpm) and heated to 50° C. A solution of NaOMe (14.8 g of a 30 wt% solution in MeOH) was added in one portion and stirring was continued for 60 min. The reaction mixture was transferred to a separatory funnel and kept at 40° C. for 120 min. A sample of the upper layer was taken after the time for soap analysis.

[0243] The conversions after stirring for 60 min and the soap contents in FAME after settling for 120 min of Examples 5 to 8 and Comparative Examples 7 to 10 are listed in Table 2.

[0244] Table 2

[0245]

[0246]

[0247] a The glycerol layer solidified at 40°C during sedimentation.

[0248] Assuming a linear relationship between the basic catalyst and the pure catalyst, the conversion of the basic catalyst (mixture of NaOMe and KOMe) was better than expected at every ratio. For example, the expected conversions for Examples 5 and 6 would be 98.3% and 98.4%, respectively.

[0249] For the transesterification reaction at an FFA content of 5 wt %, a reduction in the soap content in the FAME was achieved after sedimentation in the case of alkaline catalysts compared to the pure catalyst.

[0250] In Examples 5 to 8 where the FFA content was 5 wt%, the alkaline catalyst was partially used for neutralization. Therefore, an increased concentration of catalyst was added in consideration of the neutralized alkoxide. The active catalyst concentration after neutralization was less than 5 wt%.

Claims

1. A method for producing fatty acid C1-C4-alkyl esters from an organic oil source, wherein the oil source contains triglycerides and free fatty acids in an amount of at least 0.1 wt % based on the total weight of the organic oil source, the method comprising a) reacting the organic oil source with a C1-C4-alkanol in the presence of a basic catalyst to form an ester phase and a glycerol phase; and b) separating the fatty acid C1-C4-alkyl esters from the ester phase; The alkaline catalyst is a mixture of metal alkoxides.

2. The method according to claim 1, wherein: The C1-C4-alkanol is methanol, ethanol or a mixture thereof, preferably methanol.

3. The method according to claim 1 or claim 2, wherein: The mixture of metal alkoxides is a mixture of alkali metal oxides, preferably NaOMe and KOMe.

4. The method according to claim 3, wherein: The molar ratio of NaOMe:KOMe in the mixture of alkali metal alkoxides is from 0.01:0.99 to 0.99:0.01, preferably from 0.05:0.95 to 0.95:0.

05.

5. A method according to any one of the preceding claims, wherein: The basic catalyst is used as a solution in a C1-C4-alkanol, preferably methanol, ethanol or a mixture thereof.

6. A method according to any one of the preceding claims, wherein: The basic catalyst is used as a solution in a C1-C4-alkanol, preferably as a solution in methanol, more preferably as a solution in anhydrous methanol, with a concentration of 1% to 50% by weight, based on the total weight of the solution.

7. A method according to any one of the preceding claims, wherein: The alkaline solution is used in an amount of 0.1 wt % to 8 wt % based on the total weight of the triglyceride.

8. A method according to any one of the preceding claims, wherein: The molar ratio of the C1-C4-alkanol to the triglycerides of the organic oil source is from 3:1 to 20:1, preferably from 4:1 to 15:

1.

9. A method according to any one of the preceding claims, wherein: The amount of free fatty acids is at least 0.2 wt%, preferably at least 0.3 wt%, more preferably 0.5 to 10 wt%, especially 0.5 to 8 wt%, especially 0.5 to 5 wt%, based on the total weight of the organic oil source.

10. A method according to any one of the preceding claims, wherein: The organic oil source is derived from natural or synthetic oils and / or fats, preferably derived from vegetable oils.

11. A method according to any one of the preceding claims, wherein: The organic oil source comes from used vegetable and / or animal oils and / or fats, by-products of chemical and physical refining of vegetable and / or animal oils and / or fats, by-products of refining glycerol from biodiesel, from distilled and non-distilled fatty acids, captured grease, hydrolytically cracked fatty substances and distilled and non-distilled fatty acids produced by the cracking of soaps or mixtures thereof.

12. A method according to any one of the preceding claims, wherein: The source of organic oils is derived from used vegetable oils or by-products of the chemical and physical refining of vegetable oils.

13. The method according to claim 10 or 12, wherein: The vegetable oil is selected from the group consisting of coconut oil, corn oil, cottonseed oil, jatropha oil, olive oil, palm oil, peanut oil, rapeseed oil, safflower oil, sesame oil, soybean oil, sunflower oil, and any combination thereof.

14. A method according to any one of the preceding claims, wherein: The free fatty acid is at least one fatty acid selected from the following: caprylic acid, capric acid, lauric acid, myristic acid, palmitic acid, stearic acid, arachidic acid, behenic acid, lignoceric acid, cerotic acid, myristic oleic acid, palmitoleic acid, oleic acid, elaidic acid, vaccenic acid, linoleic acid, trans-linoleic acid, linolenic acid, arachidonic acid, eicosapentaenoic acid, erucic acid and docosahexaenoic acid, preferably, the free fatty acid is selected from oleic acid, palmitic acid, linoleic acid, lauric acid or any combination thereof.

15. A method according to any one of the preceding claims, wherein: Prior to step a) the organic oil source is subjected to at least one step selected from degumming, bleaching, drying and filtering.

16. A method according to any one of the preceding claims, wherein: Step a) comprises the following steps: a1) adding the organic oil source, the C1-C4-alkanol and the alkaline catalyst into a container, a2) mixing the organic oil source, the C1-C4-alkanol and the alkaline catalyst, and a3) allowing the mixture obtained in step a1) and step a2) to react.

17. The method according to claim 16, wherein: Step a3) comprises allowing the mixture obtained in step a1) and step a2) to react under substantially static reaction conditions.

18. The method according to claim 16, wherein: Steps a2) and a3) are carried out under mechanical agitation, with subsequent formation of the ester phase and the glycerol phase.

19. A method according to any one of the preceding claims, wherein: Step a) is carried out at a temperature of 20 to 100°C, preferably 30 to 80°C and at a pressure of 1 to 10 bar, preferably 1 to 3 bar.

20. A method according to any one of the preceding claims, wherein: Step b) comprises the following steps: b1) separating the ester phase from the glycerol phase, and b2) separating the fatty acid C1 -C4 -alkyl esters from the ester phase.

21. Use of a mixture of metal alkoxides as defined in any one of claims 1, 3, 4, 5, and 6 as a transesterification catalyst for increasing the conversion in a process for producing C1-C4-alkyl fatty acid esters, preferably in a process for producing biofuels, especially biodiesel.

22. Use of fatty acid C1-C4-alkyl esters obtainable by a process as defined in any one of claims 1 to 20 as biofuel, preferably as biodiesel.

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