Cost and energy efficient production of biodiesel from natural or industrial waste oil at low CO2 footprint

Abstract

The invention relates to a method for producing fatty acid alkyl esters from an organic oil source containing at least one free fatty acid, in which vegetable and / or animal waste oil has an acid number of at least 30 mg KOH / g, and in which the method comprises the following steps: a) reacting the oil source with glycerol at a temperature in the presence of a catalyst comprising at least methanesulfonic acid or a high anhydride thereof, the temperature during the reaction is at least 110 DEG C and no more than 180 DEG C; and b) subjecting the reaction product from step a) to acidic transesterification with an alkanol at a temperature during the reaction of at least 110 DEG C and no more than 160 DEG C wherein the reaction product from step a) comprises the at least one free fatty acid reacting with glycerol, glycerol and the catalyst; and c) separating the fatty acid alkyl ester from the reaction product from step b), wherein the reaction product from step b) comprises the fatty acid alkyl ester, glycerol, the catalyst and the alkanol; and d) separating a mixture of glycerol and catalyst from the reaction product after step c); and e) repeating steps a) to c), with the proviso that at least a portion of the glycerol and the catalyst used in step a) are produced from the mixture of step d).

Description

[0001] The present invention relates to a method for producing fatty acid alkyl esters from an organic oil source.

[0002] Biodiesel produced from waste oil is becoming increasingly attractive because there is no food - fuel issue, and waste oil has a significantly lower price compared to vegetable oil, which is the main raw material for biodiesel.

[0003] WO 2020 / 074 435 A1 describes the reaction of methanesulfonic acid (MMA) with an oil source and glycerol, followed by a transesterification step in a preferred basic medium. More specifically, a method for producing fatty acid alkyl esters from an organic oil source containing at least one free fatty acid is described, wherein the oil source has an acid value of at least 30 mg KOH / g of the oil source. The method includes step a): reacting the oil source with glycerol at a certain temperature in the presence of a catalyst comprising at least one alkyl or aryl sulfonic acid or its higher anhydride, during which the temperature does not exceed 180 °C. Step b) represents the transesterification of the reaction product from step a) with an alkanol, followed by the separation of the fatty acid alkyl ester from the reaction product of step b).

[0004] WO 2021 / 204610 A1 describes a method for producing fatty acid alkyl esters from an organic oil source containing at least one free fatty acid, wherein the plant and / or animal waste oil has an acid value of at least 30 mg KOH / g. The method includes step a): reacting the oil source with glycerol at a certain temperature in the presence of a catalyst comprising at least methanesulfonic acid or its higher anhydride, during which the temperature is at least 110 °C and does not exceed 180 °C. In step b), the reaction product from step a) is subjected to acidic transesterification with an alkanol at a certain temperature, during which the temperature is at least 110 °C and does not exceed 160 °C. Finally, the fatty acid alkyl ester is separated from the reaction product of step b).

[0005] However, there is a need to combine the steps of glycerol esterification and transesterification to provide an even more energy - efficient method for cost - effective and energy - efficient biodiesel production from natural or industrial waste oil with a low CO2 footprint. In this regard, the present invention improves the acidic glycerolysis followed by acidic pressure transesterification method as disclosed in WO 2021 / 204610 A1, especially being more time - and cost - effective.

[0006] Accordingly, an object of the present invention is to provide such a method that is a cost - effective and energy - efficient method for producing biodiesel from waste oil by at least partially reusing the MSA - containing catalyst.

[0007] This object is achieved by a process for producing fatty acid alkyl esters (FAAE) from an organic oil source containing at least one free fatty acid (FFA), wherein the plant and / or animal waste oil has an acid value of at least 30 mg KOH / g, and wherein the process comprises the following steps:

[0008] a) reacting the oil source with glycerol at a temperature in the presence of a catalyst comprising at least methanesulfonic acid or its higher anhydride, during which reaction the temperature is at least 110 °C and not more than 180 °C; and

[0009] b) subjecting the reaction product from step a) to acid transesterification with an alkanol at a temperature, during which reaction the temperature is at least 110 °C and not more than 160 °C, wherein the reaction product from step a) contains the at least one free fatty acid reacted with glycerol, glycerol and the catalyst; and

[0010] c) separating the fatty acid alkyl ester from the reaction product from step b), wherein the reaction product from step b) contains the fatty acid alkyl ester, glycerol, catalyst and alkanol;

[0011] d) separating the mixture of glycerol and catalyst from the reaction product after step c);

[0012] e) repeating steps a) to c), provided that at least a part of the glycerol and catalyst used in step a) is produced from the mixture of step d).

[0013] Surprisingly, it has been found that the acidic catalyst comprising at least methanesulfonic acid or its higher anhydride together with glycerol can be reused at least once without having a negative impact on the yield and quality of the glycerolysis process, especially on the crucial phase separation in step d). The process can be repeated not only once but also several times, depending on the quality of the feed oil.

[0014] Due to partial reuse, it is suitable to increase the percentage of the catalyst methanesulfonic acid MSA (or anhydride) to obtain a high yield of >90% FAME. Since methanesulfonic acid (or anhydride) also contributes to the greenhouse gases of the process, partial reuse will reduce the CO2 footprint and improve greenhouse gas savings.

[0015] Since MSA is partially soluble in the fatty acid alkyl ester phase, it is recommended to neutralize the ester before distillation to avoid any corrosion and sulfur content problems.

[0016] Thus, in a preferred embodiment, the separation in step c) comprises a phase separation step, wherein a first phase containing the fatty acid alkyl ester is obtained, and wherein preferably the first phase is neutralized or washed with water to remove the residual catalyst.

[0017] If methanol is used as the alkanol such that the biodiesel product is fatty acid methyl ester (FAME), the distribution of MSA between the first phase (ester phase) and the second phase (glycerol / alkanol phase) is about 0.04:1.

[0018] Advantageously, the equilibrium regarding the reaction of the FFA-containing oil with glycerol is shifted towards the product side by water removal.

[0019] Before step a), a filtration step can be carried out to remove the solid fraction from the oil source. Moreover, a degumming step can be carried out beforehand.

[0020] Preferably, step a) is carried out under reduced pressure.

[0021] Preferably, step b) is carried out under elevated pressure. Suitable pressures are from 1.1 bar to 15 bar, preferably from 4 bar to 10 bar (absolute).

[0022] Preferably, after step b) and before step c), a step b') is introduced in which the alkanol is at least partly removed by using the reaction temperature, in particular by reducing the pressure, preferably reducing it to atmospheric pressure.

[0023] Preferably, the at least partly removed alkanol can be recycled by feeding it into step b) of the process according to the invention.

[0024] To improve the kinetics of step a) and / or step b), the esterification and transesterification can be carried out as an emulsion, for example by achieving ultrasonic cavitation. Steps a) and b) can be carried out in the same reactor, preferably at similar temperatures, i.e. within the same temperature range, in particular from 110 °C to 160 °C, preferably from 120 °C to 160 °C. Preferably, the temperature difference between step a) and step b) is at most 40 °C, more preferably at most 20 °C, and the temperature in step a) is higher than the temperature in step b).

[0025] Preferably, the separation in step c) includes phase separation. Preferably, in step c), the phase separation is carried out without a prior neutralization step. Preferably, the fatty acid alkyl ester phase is neutralized separately and then purified by distillation.

[0026] Suitable for neutralization are alkali metal or alkaline earth metal compounds in the form of oxides, hydroxides, hydrides, carbonates, acetates or alkoxides of alkanols, preferably sodium hydroxide, potassium hydroxide, or sodium and potassium alkoxides of short-chain monohydric alcohols having 1 to 5 carbon atoms. The alkaline earth metal compounds are preferably sodium or potassium compounds.

[0027] Surprisingly, it has been found that at least partial reuse of the unneutralized glycerol from step c) has no negative impact on the efficiency of the process and is therefore a cost-saving measure and indeed reduces the CO2 footprint and greenhouse gas savings of the process.

[0028] Compared with sulfuric acid, which is a common acidic catalyst, methanesulfonic acid as a catalyst is advantageous because no decomposition tendency of glycerol or glycerol esters is observed or the decomposition tendency is observed to decrease due to oxidation, water removal, addition of any double bond, and sulfation.

[0029] The method can be carried out over a wide range of oil qualities and different organic oil sources having a free fatty acid content of at least 15% by weight, which corresponds to an acid value of about 30 mg KOH / g of oil source.

[0030] The starting material in the process for producing fatty acid alkyl esters (FAAE) is an organic oil source.

[0031] Compared with mineral oils, organic oils are produced by plants, animals, and other organisms through natural metabolic processes and are glyceride-based. The term "organic oil source" should be understood to include organic oils such as vegetable oils and animal oils, especially vegetable oils, and also any other mixtures, by-products, or fractions of organic oils containing at least one FFA and suitable for producing biodiesel according to the process for producing FAAE according to the invention. The term "organic oil source" also includes fats that are solid at room temperature but liquid at the reaction temperature in step a) of the process for producing FAAE according to the invention.

[0032] Organic oil sources typically contain different amounts of different types of free fatty acids as well as fatty acids bound as triglycerides, diglycerides, and monoglycerides. Only very small amounts - if any - of other organic acids may be present, and thus in the industry, acid value measurement is used to quantify the amount of all free fatty acids contained in the organic oil source. The measurement can be carried out analogously to the standard method DIN EN 14104 (2003-10).

[0033] The process of the invention is suitable for organic oil sources having an acid value of at least 30 mg KOH / g of oil source. Preferably, the oil source has an acid value of at least 40 mg KOH / g of oil source, more preferably at least 60 mg KOH / g of oil source, even more preferably at least 80 mg KOH / g of oil source, even more preferably at least 100 mg KOH / g of oil source, even more preferably at least 120 mg KOH / g of oil source, even more preferably at least 140 mg KOH / g of oil source, even more preferably at least 150 mg KOH / g of oil source.

[0034] Organic oil sources include vegetable and animal oils and fats. Vegetable oils are typically obtained by extraction from seeds with the aid of solvents or pressure, while animal fats are obtained by hot extraction in an autoclave or with the aid of solvents. Generally, 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 generally be used in biodiesel production, food, and industry.

[0035] Refined vegetable and animal oils and fats typically exhibit very low FFA content. However, during the use of these refined oils and fats, the FFA content may increase.

[0036] Used oils typically exhibit a large amount of free fatty acids and thus also have a high acid value. Therefore, in a preferred embodiment of the present invention, the organic oil source is derived from used vegetable and / or animal oils and / or fats, such as used cooking oils. Used oils are also referred to as waste oils, and thus waste oils, especially waste vegetable oils, are preferred.

[0037] Other organic oil sources include chemical and physical refining by-products of vegetable and / or animal oils and / or fats, by-products from the refining of biodiesel glycerol, fatty acids from distillation and non-distillation, hydrolytically cracked fatty substances, trap greases, and distilled and non-distilled fatty acids produced by the cracking of soaps.

[0038] In addition, mixtures of the above organic oil sources are covered.

[0039] Preferably, the organic oil source is derived from used vegetable oils or chemical and physical refining by-products of vegetable oils. The vegetable oil is preferably an oil or oil mixture 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, and sunflower oil, preferably the vegetable oil includes rapeseed oil, and even more preferably the vegetable oil is palm oil.

[0040] More preferably, the organic oil source is palm fatty acid distillate (PFAD) or palm sludge oil (PSO). PAFD is a low-value by-product generated during the refining of palm oil in the fatty acid stripping and deodorization stages. PFAD is typically sold as a source of industrial fatty acids for non-food applications.

[0041] Even more preferably, the organic oil source is palm sludge oil (PSO). It is the undistilled residue of palm oil production and has a lower quality compared to PFAD.

[0042] The organic oil source can be purified before being used in step a) of the method for producing FAAE. Optional purification steps are the removal of metal ions, for example using complexing agents (chelate formation). A washing step can also be used before step a). Suitable washing steps include water and acid washing. This can be used to remove inorganic acids, etc.

[0043] Preferably, the at least one free fatty acid is a fatty acid or a fatty acid mixture selected from the group of fatty acids consisting of: caprylic acid, capric acid, lauric acid, myristic acid, palmitic acid, stearic acid, arachidic acid, behenic acid, lignoceric acid, cerotic acid, myristoleic acid, palmitoleic acid, sapienic acid, oleic acid, elaidic acid, vaccenic acid, linoleic acid, elaidic linoleic acid, α-linolenic acid, arachidonic acid, eicosapentaenoic acid, erucic acid, and docosahexaenoic acid. Preferably, the at least one free fatty acid comprises and / or consists of oleic oil and / or palm oil. Thus, the term "at least one fatty acid" should be understood to mean that the at least one fatty acid is a specific fatty acid or a mixture of two, three or more fatty acids (a mixture of fatty acids).

[0044] These fatty acids are converted into alkyl esters to produce FAAE as biodiesel. However, the most preferred alkyl ester is methyl ester, and thus fatty acid methyl ester (FAME) is preferred. Preferably, the biodiesel obtained by the method for producing FAME according to the present invention meets the requirements of DIN EN 14214 (2014-06).

[0045] The free fatty acids are converted into alkyl esters to produce FAAE as biodiesel. However, the most preferred alkyl ester is methyl ester, and thus fatty acid methyl ester (FAME) is preferred. Therefore, the preferred alkanol is methanol.

[0046] Preferably, the reaction time in step a) can be shortened by preparing an emulsion, so that the reaction surface of the two-phase system is greatly increased.

[0047] Since water is also a reaction product in step a), appropriate measures should be taken to reduce the water formed by the reaction. Preferably, the reaction in step a) is carried out under reduced pressure (relative to atmospheric pressure). More preferably, the pressure is below 1000 hPa, more preferably 900 hPa or lower, even more preferably 800 hPa or lower, even more preferably 700 hPa or lower, even more preferably 600 hPa or lower, even more preferably 500 hPa or lower, even more preferably 400 hPa or lower, even more preferably 300 hPa or lower, even more preferably 200 hPa or lower, even more preferably 100 hPa or lower.

[0048] Preferably, during the reaction in step a), the temperature does not exceed 170 °C, more preferably does not exceed 160 °C, and even more preferably the temperature does not exceed 150 °C. Preferably, in step a), the temperature is at least 110 °C, more preferably at least 120 °C, and even more preferably at least 130 °C. Accordingly, the preferred temperature range is from 110 °C to 180 °C, more preferably the temperature is from 110 °C to 170 °C, even more preferably from 120 °C to 160 °C and even more preferably from 130 °C to 150 °C. The preferred temperature is 140 °C.

[0049] Preferably, during the reaction in step b), the temperature does not exceed 160 °C, more preferably does not exceed 150 °C. Preferably, in step b), the temperature is at least 110 °C, more preferably at least 120 °C.

[0050] Preferably, in step a), the initial molar ratio of glycerol to free fatty acids calculated based on the acid value of the oil is from 1:3 to 1:1.5, more preferably from 1:2.7 to 1:8.

[0051] Preferably, in step a), step b), or both step a) and step b), based on the total amount of the oil source, the amount of methanesulfonic acid or its anhydride is from 0.5 wt-% to 2 wt-%, even more preferably from 1 wt-% to 1.5 wt-%.

[0052] In step b), the transesterification is carried out with an alkanol, preferably methanol, to produce FAME. Since the acid catalyst is already present, no further catalyst addition is required.

[0053] The excess methanol can be separated and recycled for use in step b) of the process for producing FAAE according to the present invention.

[0054] In step c), the reaction product (biodiesel) is preferably separated by phase separation. The advantage of this method is that excellent phase separation can be achieved at all waste oil sources and FFA contents, because with the addition of glycerol, there is always a significant density difference between the two phases and no phase inversion occurs. The progress of the phase separation can be monitored by viscosity and / or conductivity measurements.

[0055] Preferably, the biodiesel (FAAE) phase is neutralized and purified by distillation under reduced pressure.

[0056] The acidic glycerol recovered after distilling the alkanol is at least partially used in the next production cycle.

[0057] Thus, the method of the present invention comprises separating a mixture of glycerol and catalyst from the reaction product after step c) (i.e., after separating FAAE) as step d). Preferably, in step d), the mixture of glycerol and catalyst is separated from the reaction product after step c) by distillation. Unexpectedly, the obtained mixture can be reused in the method without further purification.

[0058] Typically, the distillation is carried out as fractional distillation, where the alkanol is the earlier fraction, followed by the mixture of glycerol and catalyst (MSA).

[0059] Preferably, in step d), the alkanol is at least partially recycled by distillation.

[0060] To recycle the mixture, step e) is followed by step a), where steps a) to c) are repeated, provided that at least a portion of the mixture is reused in step a).

[0061] The mixture containing MSA and glycerol can be recycled as described, but can also be reused two or three times.

[0062] Thus, in a preferred embodiment, step e) is followed by a further step of separating the mixture of glycerol and catalyst from the reaction product after step c) in order to repeat step e) again.

[0063] In a preferred embodiment, no phase separation is carried out between step a) and step b). It is also preferred that steps a) and b) are carried out in the same reactor vessel.

[0064] Examples

[0065] Analysis details:

[0066] Waste oil characterization:

[0067] Dark brown / black low-viscosity liquid with a small amount of sludge deposits at room temperature

[0068] · Acid value (mg KOH / g): 116

[0069] · Calculated free fatty acid (FFA) content (%): 58

[0070] · Iodine value (mg KOH / g): 46

[0071] · Filtered water content (%): 1

[0072] · S content (ppm): 193

[0073] · P content (ppm): 309

[0074] · Soap content (ppm): 106

[0075] Pre-step a):

[0076] 1. Step: Filtration

[0077] Filter the waste oil twice at room temperature through a paper filter (1.6 - 2 μm). Residue: Approximately <1 wt%

[0078] Water content after filtration: 0.5%

[0079] Experiment 1:

[0080] Molar ratio glycerol: FFA = 1:1.8

[0081] Approximately 1.5% MSA (as active substance, based on waste oil)

[0082] 1a. Step: (Pre-step a and Step a))

[0083] (First) Acidic degumming and esterification

[0084] Mix 504.68 g of filtered waste oil, 5.1 g of water, and 10.8 g of Lutropur MSA (methanesulfonic acid, 70% active substance content) in a reaction vessel, heat to 100 °C and stir for 2 h. Then add 53.9 g of glycerol and heat the mixture to 140 °C. When the temperature is constant under vacuum, the reaction starts, and this vacuum is maintained constant at 10 kPa. The reaction time is 4 h.

[0085] Analysis results:

[0086] Table 1: Time dependence of acid value (mg KOH / g)

[0087] Control the esterification of free fatty acids with glycerol by taking samples (approx. 4 g). Wash the samples with approx. 4 g of glycerol to eliminate MSA from the mixture. Separate the glycerol phase and the oil phase. Measure the acid value from the oil phase according to DIN EN 14104.

[0088] 0h 0.5h 1.0h 2.0h 3.0h 4.0h mg KOH / g 40.8 14.4 12.1 13.5 12.7 12.6

[0089] After the reaction, 518.84 g of reaction product is obtained from Step 1a. Another 12.0 g of distillate and 7.84 g of material (mainly water) in the cold trap are obtained.

[0090] 2a. Step: (Step b))

[0091] (First) Acidic transesterification

[0092] 490.7 g of the reaction product from a) and 147.21 g of methanol (30 wt%, relative to the oil) were charged into a pressure reactor and heated to 127 °C and stirred. The reaction pressure was 5.5 * 100 kPa. The reaction time was 4 h. After 4 h, the reactor was cooled to <40 °C.

[0093] 3a. Step (Step c)

[0094] Phase separation

[0095] 585.78 g of the reaction product was charged into a separating funnel. Phase separation in the separating funnel was difficult because the phases had no visual difference (both were black). The completion of separation was judged by the change in viscosity and the measurement of conductivity.

[0096] Analysis results:

[0097] The lower phase (glycerol / methanol / MSA phase) was 108.0 g.

[0098] The conductivity of the lower phase was 5.03 mS / cm.

[0099] The upper phase (fatty acid methyl ester) was 472.23 g.

[0100] Analysis:

[0101] FAME: 90%

[0102] Mono-, di- and triglycerides: 5%

[0103] The conductivity of the oil phase was 114.2 μS / cm.

[0104] 4a. Step (Step e)

[0105] Distillation

[0106] 106.8 g of the lower phase (product temperature MeOH 65 °C) was distilled at a temperature of approximately 3 hPa and approximately 130 °C.

[0107] 3.4 g of primary low-boiling product (MeOH) was separated.

[0108] 77.4 g of higher-boiling product (glycerol / MSA) was separated.

[0109] Reuse of MSA / glycerol (Step f)

[0110] 1b. Step

[0111] (Second) Acid degumming and esterification

[0112] Mix 600.9 g of filtered waste oil and 6.1 g of water in a reaction vessel, heat to 100 °C and stir for 2 h. Then add 64.0 g of glycerol / MSA from step 4a and heat the mixture to 140 °C. When the temperature is constant under vacuum, which is maintained at 10 kPa, the reaction starts. The reaction time is 4 h.

[0113] Analysis results:

[0114] Table 1: Time dependence of acid value (mg KOH / g)

[0115] Control the esterification of free fatty acids with glycerol by taking out a sample (about 4 g). Wash the sample with about 4 g of glycerol to eliminate MSA from the mixture. Separate the glycerol phase and the oil phase. Measure the acid value from the oil phase according to DIN EN 14104.

[0116] 0h 0.5h 1.0h 2.0h 3.0h 4.0h mg KOH / g 51.0 28.3 23.1 20.1 18.2 16.9

[0117] After the reaction, 612.2 g of reaction product is obtained from step 6. Another 11.24 g of distillate and 7.15 g of material (mainly water) in the cold trap are obtained.

[0118] 2b. Steps:

[0119] (Second) Acidic transesterification

[0120] Charge 564.3 g of the reaction product from step 6 and 169.3 g of methanol (30 wt%, relative to the oil) into a pressure reactor and heat to 125 °C and stir. The reaction pressure is 4.9 * 100 kPa. The reaction time is 4 h. After 4 h, cool the reactor to <40 °C.

[0121] 3b. Steps

[0122] Phase separation

[0123] Charge 681.5 g of the reaction product into a separating funnel. Phase separation in the separating funnel is difficult because the phases have no visual difference (both are black). Judge the completion of separation by the change in viscosity and the measurement of conductivity.

[0124] Analysis results:

[0125] The lower phase (glycerol / methanol / MSA phase) is 113.6 g.

[0126] The conductivity of the lower phase is 3.93 mS / cm.

[0127] The upper phase (fatty acid methyl ester) is 561.0 g.

[0128] Analysis:

[0129] FAME: 88%

[0130] Mono-, di- and triglycerides: 3%

[0131] The conductivity of the oil phase is 114.5 μS / cm.

[0132] MSA distribution (measured by neutralization with 0.1 N KOH solution):

[0133] 4% of the MSA is in the crude biodiesel phase

[0134] (extracted from 30 g of crude biodiesel with water – 1.76 ml of 0.1 N KOH solution is required)

[0135] 96% of the MSA is in the glycerol phase

[0136] Experiment 2:

[0137] Molar ratio glycerol: FFA = 1:2.6

[0138] Approximately 1.5% MSA (as active substance, based on waste oil)

[0139] 1a. Steps:

[0140] (First) Acid degumming and esterification

[0141] Mix 507.9 g of filtered waste oil, 5.1 g of water and 10.9 g of Lutropur MSA (methanesulfonic acid, 70% active substance content) in a reaction vessel, heat to 100 °C and stir for 2 h. Then add 36.2 g of glycerol and heat the mixture to 140 °C. When the temperature is constant under vacuum, the reaction starts, which is maintained at a constant 10 kPa. The reaction time is 4 h.

[0142] Analysis results:

[0143] Table 1: Time dependence of the acid value (mg KOH / g)

[0144] Control the esterification of free fatty acids with glycerol by taking samples (approx. 4 g). Wash the samples with approx. 4 g of glycerol to eliminate MSA from the mixture. Separate the glycerol phase and the oil phase. Measure the acid value from the oil phase according to DIN EN 14104.

[0145] 0h 0.5h 1.0h 2.0h 3.0h 4.0h mg KOH / g 93.4 38.9 30.9 19.3 16.5 15.9

[0146] After the reaction, 504.64 g of reaction product are obtained from step 2. Another 9.03 g of distillate and 5.38 g of material (mainly water) in the cold trap are obtained.

[0147] 2a. Steps:

[0148] (First) Acidic transesterification

[0149] 456.39 g of the reaction product from a) and 136.9 g of methanol (30 wt%, based on the oil) were charged into a pressure reactor and heated to 127 °C and stirred. The reaction pressure was 5 * 100 kPa. The reaction time was 4 h. After 4 h, the reactor was cooled to <40 °C.

[0150] 3a. Step

[0151] Phase separation

[0152] 511.37 g of the reaction product was charged into a separating funnel. Phase separation in the separating funnel was difficult because the phases had no visual difference (both were black). The completion of separation was judged by the change in viscosity and the measurement of conductivity.

[0153] Analysis results:

[0154] The lower phase (glycerol / methanol / MSA phase) was 64.7 g.

[0155] Analysis:

[0156] FAME: 92%

[0157] Monoacylglycerol, diacylglycerol and triacylglycerol: 3%

[0158] The conductivity of the lower phase was 5.57 mS / cm.

[0159] The upper phase (fatty acid methyl ester) was 440.7 g.

[0160] The conductivity of the oil phase was 141.2 μS / cm.

[0161] 4a. Step

[0162] Distillation

[0163] 40.83 g of the lower phase (product temperature MeOH 65 °C) was distilled at a temperature of approximately 3 hPa and approximately 130 °C.

[0164] 6.42 g of the primary low-boiling product (MeOH) was separated.

[0165] 32.9 g of the higher-boiling product (glycerol / MSA) was separated.

[0166] Reuse of MSA / glycerol

[0167] 1b. Step

[0168] (Second) Acidic degumming and esterification

[0169] Mix 421.04 g of filtered waste oil and 4.22 g of water in a reaction vessel, heat to 100 °C and stir for 2 h. Then add 31.05 g of glycerol / MSA from step 4a and heat the mixture to 140 °C. When the temperature is constant under vacuum, which is maintained at 10 kPa, the reaction starts. The reaction time is 4 h.

[0170] Analysis results:

[0171] Table 1: Time dependence of acid value (mg KOH / g)

[0172] Control the esterification of free fatty acids with glycerol by taking out a sample (about 4 g). Wash the sample with about 4 g of glycerol to eliminate MSA from the mixture. Separate the glycerol phase and the oil phase. Measure the acid value from the oil phase according to DIN EN 14104.

[0173] 0h 0.5h 1.0h 2.0h 3.0h 4.0h mg KOH / g 80.8 36.6 25.3 18 14.6 11.3

[0174] After the reaction, 414.53 g of reaction product is obtained from step 6. Another 3.82 g of distillate and 6.1 g of material (mainly water) in the cold trap are obtained.

[0175] 2b. Steps:

[0176] (Second) Acidic transesterification

[0177] Charge 393.14 g of the reaction product from step 6 and 117.94 g of methanol (30 wt%, based on the oil) into a pressure reactor, heat to 125 °C and stir. The reaction pressure is 4.4 * 100 kPa. The reaction time is 4 h. After 4 h, cool the reactor to <40 °C.

[0178] 3b. Steps

[0179] Phase separation

[0180] Charge 450.1 g of the reaction product into a separating funnel. Phase separation in the separating funnel is difficult because the phases have no visual difference (both are black). Judge the completion of separation by the change in viscosity and the measurement of conductivity.

[0181] Analysis results:

[0182] The lower phase (glycerol / methanol / MSA phase) is 71.9 g.

[0183] The conductivity of the lower phase is 3.25 mS / cm.

[0184] The upper phase (fatty acid methyl ester) is 371.92 g.

[0185] Analysis:

[0186] FAME: 91%

[0187] Mono-, di- and triglycerides: 2%

[0188] The conductivity of the oil phase is 100.7 μS / cm.

[0189] The upper phase fatty acid methyl esters are distilled at 250 °C at 8 kPa without neutralization:

[0190] S content: 56 ppm

[0191] P content: <1 ppm

[0192] The upper phase fatty acid methyl esters are distilled at 250 °C at 8 kPa and neutralized with 0.24 ml of 10% NaOH / 100 g of ester:

[0193] S content: 10 ppm

[0194] P content: <1 ppm

[0195] This shows that neutralization is required before distillation.

[0196] MSA distribution (measured by neutralization with 0.1 N KOH solution):

[0197] 4% of the MSA is in the crude biodiesel phase

[0198] (extracted with water from 30 g of crude biodiesel – 1.74 ml of 0.1 N KOH solution is required)

[0199] 96% of the MSA is in the glycerol phase

[0200] 4.b. Distillation

[0201] 69.03 g of the lower phase (product temperature MeOH 65 °C) are distilled at a temperature of approximately 3 hPa and approximately 130 °C.

[0202] 29.85 g of the primary low-boiling product (MeOH) are separated.

[0203] 36.5 g of the higher-boiling product (glycerol / MSA) are separated.

[0204] Second reuse of MSA / glycerol

[0205] 1c. Step

[0206] (Third) Acid degumming and esterification

[0207] Mix 406.8 g of filtered waste oil and 4.07 g of water in a reaction vessel, heat to 100 °C and stir for 2 h. Then add 30.33 g of glycerol / MSA from step 4b and 0.71 g of Lutropur MSA (methanesulfonic acid, 70% active substance content) to balance the losses from the previous two esterification / transesterification steps. Heat the mixture to 140 °C. When the temperature is constant under vacuum, the reaction starts, and this vacuum is maintained constant at 10 kPa. The reaction time is 4 h.

[0208] Analysis results:

[0209] Table 1: Time dependence of acid value (mg KOH / g)

[0210] Control the esterification of free fatty acids with glycerol by taking out samples (about 4 g). Wash the samples with about 4 g of glycerol to eliminate MSA from the mixture. Separate the glycerol phase and the oil phase. Measure the acid value from the oil phase according to DIN EN 14104.

[0211] 0h 0.5h 1.0h 2.0h 3.0h 4.0h mg KOH / g 92.9 60.1 46.6 45.2 27.1 22.0

[0212] After the reaction, 395.64 g of reaction product is obtained from step 1c. Another 10 g of distillate and 1.8 g of material (mainly water) in the cold trap are obtained.

[0213] 2c. Step:

[0214] (Second) Acidic transesterification

[0215] Fill 378.8 g of the reaction product from step 2a and 113.65 g of methanol (30 wt%, relative to the oil) into a pressure reactor, heat to 120 °C and stir. The reaction pressure is 4.1 * 100 kPa. The reaction time is 4 h. After 4 h, cool the reactor to <40 °C.

[0216] 3c. Step

[0217] Phase separation

[0218] Fill 428.7 g of the reaction product into a separating funnel. Phase separation in the separating funnel is difficult because the phases have no visual difference (all black). Judge the completion of separation by the change in viscosity, which clearly indicates very good phase separation.

[0219] Analysis results:

[0220] The lower phase (glycerol / methanol / MSA phase) is 53.6 g.

[0221] The upper phase (fatty acid methyl ester) is 372.92 g.

[0222] 4.c. Distillation

[0223] Distill 52.7 g of the lower phase (product temperature MeOH 65 °C) at a temperature of approximately 3 hPa and approximately 130 °C.

[0224] Isolate 25.5 g of the primary low-boiling product (MeOH).

[0225] Isolate 24.1 g of the higher-boiling product (glycerol / MSA).

[0226] Third reuse of MSA / glycerol

[0227] 1d. Step

[0228] (IV) Acid degumming and esterification

[0229] Mix 286.8 g of filtered waste oil and 2.9 g of water in a reaction vessel, heat to 100 °C and stir for 2 h. Then add 21.32 g of glycerol / MSA from step 4c and 0.2 g of Lutropur MSA (methanesulfonic acid, 70% active substance content) to balance the losses from the previous esterification / transesterification steps. Heat the mixture to 140 °C. When the temperature is constant under vacuum, the reaction starts, which is maintained at a constant 10 kPa. The reaction time is 4 h.

[0230] Analysis results:

[0231] Table 1: Time dependence of the acid value (mg KOH / g)

[0232] Control the esterification of free fatty acids with glycerol by taking samples (approx. 4 g). Wash the samples with approx. 4 g of glycerol to eliminate MSA from the mixture. Separate the glycerol phase and the oil phase. Measure the acid value from the oil phase according to DIN EN 14104.

[0233] 0h 1.0h 2.0h 3.0h mg KOH / g 90.8 85.0 77.1 61.7

[0234] The upper phase (fatty acid methyl ester) is 259.3 g.

[0235] Experiment 3:

[0236] Molar ratio glycerol:FFA = 1:2.7

[0237] Approximately 1.0% MSA (as active substance, based on waste oil)

[0238] 1a. Step:

[0239] (I) Acid degumming and esterification

[0240] 521.06 g of filtered waste oil, 5.21 g of water and 7.82 g of Lutropur MSA (methanesulfonic acid, 70% active substance content) were mixed in a reaction vessel, heated to 100 °C and stirred for 2 h. Then 37.14 g of glycerol was added and the mixture was heated to 140 °C. When the temperature was constant under vacuum, the reaction started, and the vacuum was kept constant at 10 kPa. The reaction time was 4 h.

[0241] Analysis results:

[0242] Table 1: Time dependence of acid value (mg KOH / g)

[0243] The esterification of free fatty acids with glycerol was controlled by taking out samples (about 4 g). The samples were washed with about 4 g of glycerol to eliminate MSA from the mixture. The glycerol phase and the oil phase were separated. The acid value was measured from the oil phase according to DIN EN 14104.

[0244] 0h 0.5h 1.0h 2.0h 3.0h 4.0h mg KOH / g 89.9 32.6 26.8 26.9 17.6 14.6

[0245] After the reaction, 517.98 g of reaction product was obtained from step 2. Another 9.61 g of distillate and 4.09 g of material (mainly water) in the cold trap were obtained.

[0246] 2a. Steps:

[0247] (First) Acidic transesterification

[0248] 477.2 g of the reaction product from a) and 143.22 g of methanol (30 wt%, relative to the oil) were filled into a pressure reactor, heated to 127 °C and stirred. The reaction pressure was 5 * 100 kPa. The reaction time was 4 h. After 4 h, the reactor was cooled to <40 °C.

[0249] 3a. Steps

[0250] Phase separation

[0251] 551.43 g of the reaction product was filled into a separating funnel. Phase separation in the separating funnel was difficult because the phases had no visual difference (all black). The completion of separation was judged by the change in viscosity and the measurement of conductivity.

[0252] Analysis results:

[0253] The lower phase (glycerol / methanol / MSA phase) was 90.08 g.

[0254] The conductivity of the lower phase was 4.56 mS / cm.

[0255] The upper phase (fatty acid methyl ester) was 457.93 g.

[0256] Analysis:

[0257] FAME: 91%

[0258] Mono-, di- and triglycerides: 3%

[0259] The conductivity of the oil phase is 75.3 μS / cm.

[0260] 4a. Step

[0261] Distillation

[0262] 87.26 g of the lower phase (product temperature MeOH 65 °C) was distilled at a temperature of approximately 3 hPa and approximately 130 °C.

[0263] 28.21 g of the primary low-boiling product (MeOH) was separated off.

[0264] 56.01 g of the higher-boiling product (glycerol / MSA) was separated off.

[0265] Reuse of MSA / glycerol

[0266] 1b. Step

[0267] (Second) Acid degumming and esterification

[0268] 523.22 g of filtered waste oil and 5.24 g of water were mixed in a reaction vessel, heated to 100 °C and stirred for 2 h. Then 39.52 g of the glycerol / MSA from step 5 was added and the mixture was heated to 140 °C. When the temperature was constant under vacuum, the reaction started, which vacuum was kept constant at 10 kPa. The reaction time was 4 h.

[0269] Analysis results:

[0270] Table 1: Time dependence of the acid value (mg KOH / g)

[0271] The esterification of free fatty acids with glycerol was controlled by taking samples (approx. 4 g). The samples were washed with approx. 4 g of glycerol to eliminate MSA from the mixture. The glycerol phase and the oil phase were separated. The acid value was measured from the oil phase according to DIN EN 14104.

[0272] 0h 0.5h 1.0h 2.0h 3.0h 4.0h mg KOH / g 79.3 59.7 39 27.3 24.2 19.5

[0273] After the reaction, 546 g of reaction product was obtained from step 6. Another 2.5 g of distillate and 5.1 g of material (mainly water) in the cold trap were obtained.

[0274] 2b. Step:

[0275] (Second) Acid transesterification

[0276] 479.53 g of the reaction product from Step 6 and 143.86 g of methanol (30 wt%, relative to the oil) were filled into a pressure reactor and heated to 125 °C and stirred. The reaction pressure was 4.3 * 100 kPa. The reaction time was 4 h. After 4 h, the reactor was cooled to <40 °C.

[0277] 3b. Step

[0278] Phase separation

[0279] 558.20 g of the reaction product was filled into a separating funnel. Phase separation in the separating funnel was difficult because the phases had no visual difference (both were black). The completion of separation was judged by the change in viscosity and the measurement of conductivity.

[0280] Analysis results:

[0281] The lower phase (glycerol / methanol / MSA phase) was 86.07 g.

[0282] The conductivity of the lower phase was 3.99 mS / cm.

[0283] The upper phase (fatty acid methyl ester) was 469.89 g.

[0284] Analysis:

[0285] FAME: 84%

[0286] Monoacylglycerol, diacylglycerol and triacylglycerol: 9%

[0287] The conductivity of the oil phase was 67.2 μS / cm.

[0288] MSA distribution (measured by neutralization with 0.1 N KOH solution):

[0289] 4% of MSA was in the crude biodiesel phase

[0290] (extracted from 30 g of crude biodiesel with water – 1.2 ml of 0.1 N KOH solution was required)

[0291] 96% of MSA was in the glycerol phase.

Claims

1. A method for producing fatty acid alkyl esters from an organic oil source containing at least one free fatty acid, wherein the plant and / or animal waste oil has an acid value of at least 30 mg KOH / g, and wherein the method comprises the following steps: a) Reacting the oil source with glycerol at a certain temperature in the presence of a catalyst comprising at least methanesulfonic acid or its higher anhydride, during which the temperature is at least 110 °C and not more than 180 °C; and b) Subjecting the reaction product from step a) to acid transesterification with an alkanol at a certain temperature, during which the temperature is at least 110 °C and not more than 160 °C, wherein the reaction product from step a) contains the at least one free fatty acid reacted with glycerol, glycerol and the catalyst; and c) Separating the fatty acid alkyl ester from the reaction product from step b), wherein the reaction product from step b) contains the fatty acid alkyl ester, glycerol, the catalyst and the alkanol; d) Separating the mixture of glycerol and catalyst from the reaction product after step c); e) Repeating steps a) to c), provided that at least a part of the glycerol and the catalyst used in step a) is produced from the mixture of step d).

2. The method according to claim 1, wherein, The fatty acid alkyl ester is fatty acid methyl ester.

3. The method according to claim 1 or 2, wherein The organic oil source is from used plant and / or animal oils and / or fats, chemical and physical refining by-products of plant and / or animal oils and / or fats, by-products from biodiesel refined glycerol, distilled and non-distilled fatty acids, trap grease, hydrolytically cracked fat substances and distilled and non-distilled fatty acids produced by the cracking of soaps or mixtures thereof.

4. The method according to any one of claims 1 to 3, wherein The organic oil source has an acid value of at least 40 mg KOH / g oil source, preferably at least 60 mg KOH / g oil source, more preferably at least 80 mg KOH / g oil source, even more preferably at least 100 mg KOH / g oil source, even more preferably at least 120 mg KOH / g oil source, even more preferably at least 140 mg KOH / g oil source, even more preferably at least 150 mg KOH / g oil source.

5. The method according to any one of claims 1 to 4, wherein, In step a), the temperature is at least 120 °C, more preferably at least 130 °C, and / or the temperature does not exceed 170 °C, preferably does not exceed 160 °C, more preferably does not exceed 150 °C.

6. The method according to any one of claims 1 to 5, wherein, In step b), the temperature is at least 110 °C, more preferably at least 115 °C, and / or the temperature does not exceed 160 °C, preferably does not exceed 150 °C, more preferably does not exceed 140 °C.

7. The method according to any one of claims 1 to 6, wherein, In step a), the initial molar ratio of glycerol to free fatty acid calculated based on the acid value of the oil is 1:3 to 1:1.5, more preferably 1:2.7 to 1:

8.

8. The method according to any one of claims 1 to 7, wherein In step a), step b) or steps a) and b), based on the total amount of the oil source, the amount of methanesulfonic acid or its anhydride is 0.5 wt-% to 2 wt-%.

9. The method according to any one of claims 1 to 8, wherein, In step c), the separation includes a phase separation step, wherein a first phase containing the fatty acid alkyl ester and a second phase containing glycerol, the catalyst and the alkanol are obtained, and preferably the first phase is neutralized or washed with water to remove the residual catalyst.

10. The method according to any one of claims 1 to 9, wherein, In step d), the mixture of glycerol and catalyst is separated from the reaction product after step c) by distillation.

11. The method according to any one of claims 1 to 10, wherein, In step d), the alkanol is at least partially recycled by distillation.

12. The method according to any one of claims 1 to 11, wherein, After step e), there is a further step of separating the mixture of glycerol and catalyst from the reaction product after step c) in order to repeat step e) again.

13. The method according to any one of claims 1 to 12, wherein, No phase separation is carried out between step a) and step b).

14. The method according to any one of claims 1 to 13, wherein, Steps a) and b) are carried out in the same reactor vessel.

15. The method according to any one of claims 1 to 14, wherein, After step b) and before step c), step b') of at least partially removing the alkanol by using the reaction temperature, in particular by reducing the pressure, preferably to atmospheric pressure, is introduced.