Method of producing biodiesel

Abstract

The present invention relates to a method of producing fatty acid alkyl ester from an organic oil source containing at least one free fatty acid, wherein the oil source has an acid number of at least 30 mg KOH/g oil source and wherein the method comprises the steps of a) reacting the oil source with glycerol at a temperature, which does not exceed 180° C. during the reaction, in the presence of a catalyst comprising at least one alkyl or aryl sulfonic acid or an homoanhydride thereof; and b) transesterification of the reaction product from step a) with an alkanol; and c) isolating the fatty acid alkyl ester from the reaction product of step b).

Claims

1. A method of producing fatty acid alkyl ester from an organic oil source comprising at least one free fatty acid, wherein the oil source has an acid number of at least 30 mg KOH/g oil source and wherein the method comprises the steps of a) reacting the oil source with glycerol at a temperature, which is at least 110° C. and does not exceed 180° C. during the reaction, in the presence of a catalyst comprising at least methanesulfonic acid or the homoanhydride thereof, wherein in step a) the initial molar ratio of glycerol to free fatty acid calculated on the basis of the acid number of the oil is from 1:2 to 1.2:1 b) transesterification of the reaction product from step a) with an alkanol; and c) isolating the fatty acid alkyl ester from the reaction product of step b).

2. The method of claim 1, wherein the fatty acid alkyl ester is fatty acid methyl ester.

3. The method of claim 1, wherein the oil source is from used vegetable and/or animal oil and/or fat, by-products of the chemical and physical refining of vegetable and/or animal oil and/or fat, by-products of the refining of glycerine from biodiesel, fatty acids from distillation and non-distillation, trap grease, hydrolytically cleaved fatty substances, distilled and non-distilled fatty acids resulting from the cleaving of soap, or mixtures thereof.

4. The method of claim 3, wherein oil source is from used vegetable oil or by-products of the chemical and physical refining of vegetable oil.

5. The method of claim 1, wherein the oil source has an acid number of at least 40 mg KOH/g oil source.

6. The method of claim 1, wherein the at least one free fatty acid is a fatty acid or a mixture of fatty acids selected from 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, linolelaidic acid, alpha-linoleic acid, arachidonic acid, eicosapentaenoic acid, erucic acid and/or docosahexaenoic acid.

7. The method of claim 1, wherein in step a) the temperature does not exceed 170° C.

8. The method of claim 1, wherein in step a) the temperature is at least 120° C.

9. The method of claim 1, wherein the catalyst comprises at least methanesulfonic acid.

10. The method of claim 1, wherein the reaction in step a) has a reaction time of more than one hour and less than 12 hours.

11. The method of claim 1, wherein the reaction in step a) is carried out under reduced pressure.

12. The method of claim 1, wherein in step a) the initial molar ratio of glycerol to free fatty acid calculated on the basis of the acid number of the oil is from 1:2 to 1:1.

13. The method of claim 1, wherein in step a) the amount of the methanesulfonic acid or the homoanhydride thereof is from 0.2 to 0.6 weight-% based on the total amount of the oil.

14. The method of claim 1, wherein in step c) the isolation further comprises a distillation step.

15. The method of claim 1, wherein between step a) and step b) no phase separation is carried out.

16. The method of claim 1, wherein after step a) and before step b) the methanesulfonic acid or the homoanhydride thereof and optionally residual free fatty acid is neutralized.

17. The method of claim 1, wherein step a) is carried out in the presence of at least one anionic surfactant S.

18. The method of claim 4, wherein oil source is coconut oil, corn oil, cottonseed oil, olive oil, palm oil, peanut oil, rapeseed oil, safflower oil, sesame oil, soybean oil, sunflower oil, palm fatty acid distillate or palm sludge oil.

19. The method of claim 4, wherein the oil source has an acid number of at least 60 mg KOH/g oil source.

20. The method of claim 1, wherein the at least one free fatty acid comprises oleic oil and/or palmitic acid.

Description

EXAMPLES

Example 1: Standard Conditions Reaction Step a) According to the Method of the Invention

(1) Model biological oil source prepared from oleic acid/refined rape seed oil: 80/20 (free fatty acid content (FFA) of the oil phase: 80 wt %, Acid number (calculated) 159 mg KOH/g biological oil source=“oil phase”)

(2) temperature: 140° C.

(3) catalyst: methanesulfonic acid (MSA)

(4) methanesulfonic acid: 0.5 wt % related to the oil phase

(5) glycerol/oleic acid: 0.84 molar ratio

(6) pressure: 10 kPa

(7) 188.8 g oleic acid (=0.67 mol), 47.2 g rape seed oil (refined, acid number 0.19 mgKOH/g) (=236 g oil phase) and 59 g glycerol 87% active (=0.56 mol) were mixed in a reaction vessel and heated up to 140° C. under vacuum (10 kPa) and stirring. 1.69 g methanesulfonic acid (MSA) 70% active (=1.183 g MSA=12.3 mmol=0.5 wt % related to the oil phase) were added to the reaction mixtures. The reaction time starts at 140° C. and temperature and vacuum is kept constant at 10 kPa.

(8) The esterification of oleic acid with glycerol was controlled by taking out samples (ca. 4 g). The sample is washed with ca. 4 g glycerol to eliminate MSA from the mixture. Glycerol and oil phase are separated. From the oil phase the acid number is measured according to DIN EN 14104.

(9) The 0 h value is determined before the addition of MSA or in later procedure the corresponding other acids.

Example 2

(10) The time dependency of acid number was controlled as summarized in Table 1.

(11) TABLE-US-00001 TABLE 1 Time dependency of Acid number in mgKOH/g 0 h 0.5 h 1.0 h 2.0 h 4.0 h 6.0 h 8.0 h Example 1 153 92 13.2 3.1 2.1 1.9 1.7

(12) Table 1 shows that from a reaction time of 4.0 hours an onwards the acid number is in the range of about 2 or below.

(13) The reproducibility was controlled by repeating the 4 h-result for 4 times:

(14) TABLE-US-00002 Acid number (mgKOH/g) 140° C. 4 h Example 1 2.1 Repeat 1 1.7 Repeat 2 2.1 Repeat 3 2.3 Repeat 4 1.9

Example 2: Variation of Acid

(15) According to the procedure of Example 1 different acids and quantities were used and summarized in Table 2.

(16) TABLE-US-00003 TABLE 2 acid (g, wt % Acid number Acid calculated related to mmol (mgKOH/g) Acid (g) 100% active) the oil phase acid 4 h Without 0 0 0 0 104.7 MSA (70%) (Example 1) 1.69 1.18 0.5 12.3 2.1 para-TSA.sup.+) 2.36 2.36 1.0 13.7 2.60 H.sub.2SO.sub.4 (conc.)**) 1.75 1.68 0.71 17.1 5.9 H.sub.2SO.sub.4 (conc.)**) 1.25 1.2 0.51 12.2 5.1 H.sub.2SO.sub.4 (conc.)*) 0.93 0.89 0.38 9.1 7.4 H.sub.2SO.sub.4 (conc.) 0.47 0.45 0.19 4.6 11.4 2-Ethylhexyl titanate 1.05 1.0 0.43 1.8 82.1 2-Ethylhexyl titanate 7.26 6.9 2.92 12.3 74.0 Tin (II) chloride dihydrate 2.8 2.8 1.19 12.4 66.0 .sup.+)para TSA = para toluenesulfonic acid *)some precipitate formed **)tar like by-products are formed during the reaction

(17) Table 2 shows that only MSA and p-TSA show good results, especially MSA.

Example 3: Para-Toluene Sulfonic Acid (p-TSA) at 140° C., 8 h

(18) According to the procedure of Example 1 para-toluene sulfonic acid (13.7 mmol) was used at 140° C. for up to 8 h and in Table 3 compared with MSA.

(19) TABLE-US-00004 TABLE 3 Acid number (mgKOH/g) 0 h 0.5 h 1.0 h 2.0 h 4.0 h 6.0 h 8.0 h Example 1 (140° C.) 153 92 13.2 3.1 2.1 1.9 1.7 p-TSA (140° C.) 153 27 4.8 2.9 2.6 2.4 1.8 Example 2

(20) Reproducibility of o-TSA Results:

(21) TABLE-US-00005 Acid number (mgKOH/g) 140° C. 4 h Example 2 2.6 Repeat 1 2.7 Repeat 2 2.6

Example 4: Variation of Glycerol to Oleic Acid Ratio

(22) According to the procedure of Example 1 different addition levels of Glycerol were used and summarized in Table 4.

(23) TABLE-US-00006 TABLE 4 Glycerol/Oleic acid Acid number (free fatty acid) Glycerol Glycerol mmol (mgKOH/g) molar ratio (g, 87%) (g, 100%) Glycerol 4 h 0.30 21.2 18.4 200 24.9 0.50 35.4 30.8 334 2.8 0.6 42.5 37.0 401 2.2 0.67 47.2 41.1 446 2.1 0.84 (Example 1) 59 51.3 560 2.1 1.0 70.8 61.6 669 3.7 1.2 84.9 73.9 802 3.8

(24) Table 4 shows that very good results were observed with molar ratios of below 1 to about 0.5.

Example 5: Variation of Free Fatty Acid (FFA) Content in the Oil Phase (Glycerol/FFA: Molar Ratio 0.8-0.84)

(25) According to the procedure of Example 1 different addition levels of Oleic acid, rape oil & Glycerol were tested.

(26) TABLE-US-00007 TABLE 5 rape FFA content in oleic oleic seed oil Glycerol Acid number the oil phase acid acid oil phase (g, cal. Glycerol Glycerol/FFA (mgKOH/g) (wt. %) (g) (mmol) (g) (g) 100%) (mmol) molar ratio 4 h 80 (Exam. 1) 188.8 670 47.2 236 51.3 560 0.84 2.1 50 118.0 418 118.0 236 30.8 334 0.80 2.2 30 70.8 251 165.2 236 19.3 210 0.83 2.0 20 47.2 167 188.8 236 12.9 140 0.84 2.2 10.sup.+) 23.6 84 212.4 236 6.4 69 0.82 11.1 10.sup.+) 23.6 84 212.4 236 12.8 138 1.64 2.3 .sup.+)Acid number of 20 mg KOH/g organic oil source

Example 6: Variation of Temperature

(27) Procedure Analogous to Example 1 but Different Temperatures.

(28) The temperature dependency was tested for different temperatures. The results are summarized in Table 6.

(29) TABLE-US-00008 TABLE 6 Temperature dependency of Acid number in mg KOH/g Temperature Acid number (mgKOH/g) (° C.) 4.0 h 110 77.8 120 3.0 140 (Example 1) 2.1 160 2.3 180 2.5

Example 7: Variation of MSA (Ca. 100%) Concentration (% of Oil Phase)

(30) According to the procedure of Example 1 different MSA concentrations were tested.

(31) TABLE-US-00009 TABLE 7 MSA dependency of Acid number in mgKOH/g MSA Acid number MSA wt.-% (cal. 100%) (mgKOH/g) of oil phase (g) 4.0 h 0.1 0.24 6.6 0.2 0.47 2.8  0.25 0.59 2.3 0.3 0.71 2.1 0.4 0.94 2.1 0.5 (Example 1) 1.18 2.1 0.6 1.41 3.8

Example 8: MSA Dependency of Acid Number

(32) The acid number of different samples with increasing content of MSA was tested and summarized in Table 8.

(33) TABLE-US-00010 TABLE 8 50 wt % FFA - MSA dependency of Acid number in mgKOH/g MSA % MSA Acid number of oil phase (cal. 100%) (mgKOH/g) (w/w) (g) 4.0 h 0.1 0.24 8.3 0.2 0.47 1.9 0.3 0.71 1.8 0.5 1.18 1.6

Example 9: Impact of the Addition of Sulfonate-Based Anionic Surfactant on the Esterification Kinetics (at 140° C.)

(34) According to the procedure Example 1 addition of 0.5% w/w of Disponil® LDBS 55 (55% concentration in water) was tested and summarized in Table 9. Disponil® LDBS 55:

(35) ##STR00003##

(36) TABLE-US-00011 TABLE 9 Impact of the addition of sulfonate-based anionic surfactant esterification Acid number in mgKOH/g 0 h 0.5 h 1.0 h 2.0 h 4.0 h Example 1 153 92 13.2 3.1 2.1 Example 1 + 0.5% 153 17 5.6 2.5 1.7 w/w Disponil LDBS 55

Example 10: Reaction Step b) According to the Method of the Invention

(37) Transesterification of resulting oil by reaction with glycerol without prior phase separation from the above process with Methanol:

(38) Procedure:

(39) 1. Step Transesterification

(40) To 250 g product from Example 1 3.76 g KOH (dissolved in 40.9 g Methanol) were added at 60° C. 1 h reaction time at 60° C. under stirring. Product was put at 60° C. in a separatory funnel. After 30 min. the phase separation was completed (oil phase at top/glycerol Methanol phase at bottom). Oil phase (229.2 g) were separated from the glycerol/methanol phase (65.4 g) and refilled into the reactor for step 2.

(41) 2. Step Transesterification

(42) 229 g oil phase were heated to 60° C. and 1.03 g KOH (dissolved in 16.0 g Methanol) were added. 1 h reaction time at 60° C. under stirring. Product was put at 60° C. in a separatory funnel. After 30 min. the phase separation was completed (oil phase at top/glycerol Methanol phase at bottom). Oil phase (223.8 g) were separated from the glycerol/methanol phase (7.4 g). Oil phase is acidified at 90° C. with 5 ml of 0.2 m MSA resulting in a pH of 1.9).

(43) The resulting fatty acid methylester (FAME) was washed two times with water and dried by distillation of the residual water.

(44) In both steps there is no precipitation of salt (K-mesylate). The phase separation is complete and fast also no purification step in the starting product (Example 1) was made (no phase separation in Example 1). The sulfur content in the FAME was analyzed to 17 ppm.

(45) Transesterification with p-TSA (Example 2) was analogue to MSA (Example 1). The sulfur content in the FAME was analyzed to 32 ppm for p-TSA as catalyst.

(46) Sulfur Content:

(47) Oleic acid: 4 ppm,

(48) Rape oil: <2 ppm,

(49) Glycerol: <2 ppm.

(50) Trace analysis of by-products:

(51) Hydroxyacetone <50 mg/kg

(52) Acrolein <10 mg/kg.