WO2008140432A1

WO2008140432A1 - A process for removal of free fatty acids from vegetable oils

Info

Publication number: WO2008140432A1
Application number: PCT/TR2008/000026
Authority: WO
Inventors: Bulent Keskinler; Aziz Tanriseven; Nadir Dizge; Ekrem Pakdemirli
Original assignee: Bulent Keskinler; Aziz Tanriseven; Nadir Dizge; Ekrem Pakdemirli
Priority date: 2007-05-15
Filing date: 2008-03-26
Publication date: 2008-11-20
Also published as: TR200703297A2

Abstract

This invention concerns about removal of free fatty acids (FFA) content of industrial and/or edible vegetable oils by using a chemical method and a new reactor configuration.

Description

A PROCESS FOR REMOVAL OF FREE FATTY ACIDS FROM

VEGETABLE OILS

Raw oil extracted from oily seeds is consisted of components such as triacylglyceride, partial acylglyceride (mono acylglyceride, diacylglyceride), free fatty acids (FFA), phospholipids, pigment, sterol and tacopherol. In order to obtain an oil of usable quality, the extracted raw oil is kept subject to a number of operations such as FFA removal, degumming, bleaching and deodorizing. Among these purification steps, removal of free fat acids constitutes the most difficult as well as the most important one in terms of quality of the final product. This process has maximum economic significance for production cost of oil of desirable quality. Removal of free fatty acids from oil is performed by means of physical, chemical and miscella methods at industrial scale. Especially, application of chemical process for removal of free fatty acids from oils having especially high content of FFA causes significant amount of oil lossing due to saponification and emulsification. Although physical methods are considered more applicable for removal of free fatty acids from the oils containing high fatty acid, their power consumption is quite high. Both for vegetable oils used in industry and edible vegetable oils, free fatty acids should be removed in a way to cause minimum loss of oil and in the most economic way.

New methods and techniques developed as alternative to classical methods are recommended in the literature for removal of free fatty acids from vegetable oils such as removal of FFA biologically, chemical esterification, supercritical extraction, membrane processes, liquid-liquid extraction, stripping by method of at high temperature and low pressure. These methods present certain advantages and disadvantages against each other.

In the classical methods of removal of free fatty acids from oils, oil is put into reaction accompanied by an alkali (NaOH, KOH vb.) and thus FFA is transformed into soap and removed. There are a number of methods and techniques today which are still used for removal of free fatty acids in classical way. In the patents obtained by Melin C. (U.S. Pat. No. 5,962,056) and Ganguli KL (U.S. Pat. No. 6,251,460), it is reported that free fatty acids culd be removed by sodium carbonate or sodium hydroxide treatment. In this treatment, oleic acid in the oil was treated with concentrated sodium carbonate solution and then liquid phase was separated and oil was washed by water until neutralizated.

Miscella refining is preferred in the industry especially for refining of cotton oil because of more cost-effective color bleaching and less loss in the refining. Despite of these advantages, miscella refining has disadvantages such as high investment cost as well as requirement of exproof, restricting applicability of removal method of FFA.

Chemical esterification is another process for removal of FFA. In this method, FFA is esterified again at high temperature, inert medium, with free hidroxyl groups remained in the oil with or without catalyst (or hidroxyl groups added from glycerin). In a study performed by BiJay Krishna De et al. (Eur. J. Lipid Sci. Technol. 2002, 104, 167-173), free fatty acids in the palm kernel oil was removed by esterification by glycerin at stoichiometric amount at 160-165 °C (at 10 mmHg pressure (1.33 kPa). After 6 hours, FFA content was reduced from 25% (w/w) to 1.6% (w/w). Although high rate of FFA is removed in the method of chemical esterification method, use of high temperature (up to 270 °C) increases cost of the method.

In another study performed by Simeos P.C. (J. Supercritical Fluids, 1998, 13, 337- 341) and Brunetti L. (J. Am. Oil Chem. Soc, 1989, 66, 209-217), free fatty acids were removed from oil containing high FFA by means of supercritical carbon dioxide extraction (SCFE). This method is a costly alternative FFA removal method.

Another alternative method for removal of FFA is membrane technology that separate components by difference of molecular weight. Many researchers recommended use of membrane with or without solvent, with or without porosity for removal of FFA from vegetable oils. Membrane processes have advantages such as less energy consumption at room temperature, no need of additional chemical substances, ensuring nutrients and other desired components to remain in the oil, but the most important factor that restricts this method is difficult separation process due to small difference between molecular weights of monoacylglycerides and free fatty acids.

Free fatty acids may also be removed from the oils by using adsorptive chromatography. In the patent obtained by Priegnitz J.W. (U.S. Pat. No. 5,179,219), it was reported that silicagel was used as adsorbent for removal of free fatty acids from the oil. In the patent (U.S. Pat. No. 5,414,100) obtained by Oyorinde F.O. et al., it is stated that alumina can be used to remove FFA.

In a study made by Meirelles J.A.A. et al. (Recent Patents on Engineering, 2007, 1, 95-102), purification process was performed by using short chain alcohols on basis of selective extraction of free fatty acids.

In a patent obtained in 1947 by Liebseher E.S. and North N.S., in order to remove FFA from vegetable oil and animal fats, a mixture prepared by adding glycerin at variable rate to NaOH liquid solution was used. After saponification of FFA by quick mixing, important part of soaps was precipitated by glycerin phase. It is stated in the patent that although loss of fat for conversion of fat to soap was less than the classical system, significant amount of oil transferred to glycerin phase realized. It is also stated that fat remains in the glycerin phase even separator is used. It is recommended that such loss of oil may be eliminated by increasing temperature of glycerin phase. In a sample study in the same patent, it was seen that when 1.1% glycerin and 0.175% NaOH is added to the raw cotton oil containing 1.6% FFA, refining loss was 3.78% and that such loss reached to 5.8% in case of classical refining of the same oil.

It is basic core of the invention to prevent loss of oil by eliminating formation of additional soap and emulsion stemming from water in conventional processes where liquid base is used to remove free fatty acid. This approach utilizes NOBA reactor and operating mentality in order to remove free fatty acids especially from vegetable oils used in the industry and edible vegetable oils. NOBA reactor where homogenous transesterification reactions occur was developed by Keskinler B. et al. (TR 2005 04613 A2). This reactor is related to new transesteriffϊcation reactor types where quickly glycerin separation is made from vegetable oil and/or waste by using homogenous alkali catalysis method for production of biodiesel and to the biodiesel production process where these reactors are used. NOBA process that can be used together with many different types of reactor configurations is essentially consisted of transesterification of vegetable oil and/or waste by use of homogenous alkali catalyst accompanied by methyl alcohol and reaction/seperation steps which was provided separation of glycerine in a short time.

New approach with respect to use of NOBA reactor for removal of FFA from oils is given below. NOBA reactor is consisted of two major parts as indicated in Figure 1. Part (A) indicates main reactor block where FFA neutralization is performed, and part (B) which is filled with neutral oil before starting of process indicates the section where displacement of neutral oil by glycerin added to part (A) during or after neutralization. Both main parts are connected to each other by one or more connection pipes (10) with inner diameter of 1/5-1/10 with flange and one valve (11) attached to it. In the part (A) of the reactor configuration, there is a pedal mixer (6) to provide turbulance required for reaction and no mixer is used in the part (B). In order to ensure a good mixture in the part (A), 4 deflection plates (7) are used. Optionally, gas inlet (3) for neutralization with ammonia gas, a manual or digital pressure indicator (5) and, in connection with it, an on-off valve (4) are attached. Manual valves may also be used instead of on-off valve (4). For supply of necessary reagents and vegetable oil with high content of free fatty acids to the part (A) of the reactor for FFA neutralization, valves (1) and (2) are used. Heating elements were laid in the part (A) of the reactor (8), and in the part (B) heating is performed by using a jacket (16). Hot oil or steam is used for heating by help of valve (15). Valves (12), (13) and (14) are used for taking free-FFA oil and glycerin removed outside the reactor. Glycerin level is monitored by means of watching window located in the part (B) and oil level by watching window (9) in the part (A). Volume of the part (B) is 1/11-1/12 of the reaction volume in the part (A). This volume is selected by more than 15-20% than maximum volume of glycerin to be used in the process. The reactor shown in Figure 1 is operated in the following manner. First when the valve (11) is on, valve (2) is used for filling up to neck part (10) of the part (B) is filled with neutral oil (or with biodiesel in order to produce biodiesel in case of being made oil refining) refined beforehand and then valve (11) is off. After this operation, raw oil or used oil is supplied to reactor from valve (2) and brought to a temperature about 50-60 ⁰C. At this time, temperature of the part (B) should also be at a temperature between 50-60 ⁰C. Removal of FFA from vegetable oils containing high free fatty acids which are used in the industry for production of biodiesel is achieved by addition to the oil of an alkali catalyst (NaOH, KOH or NH₃) dissolved in methyl alcohol or ethyl alcohol. Removal of FFA from edible vegetable oils is achieved by adding an alkali catalyst (NaOH, KOH or NH₃) dissolved in hot glycerin (90-95 ⁰C) in order to prevent ester formation. When all valves are off, mixer is operated for 15 minutes under turbulance conditions and, at the end of this period, if alkali catalyst has been used, technical glycerin is added to the reactor to remove the resulting soap from the reaction medium and then mixed for further 15 minutes. At the end of 30 minutes, mixing speed is set to a lower speed, valve (11) is opened and soap, water and glycerin retaining other impurities start to collect in the part (B). As a result of these operations, oil removed from its FFA is separated in the part (A) and glycerin and undesired impurities separated in the part (B). Level of glycerin can be controlled from the watching window (9). At the end of 50 minutes, valve (11) is closed and valves (12) are opened to take glycerin from the reactor for further treatment. Later on, in order to take the oil removed from its FFA remained in the part (A), valve (11) is opened. Valve (12) is closed and taken outside the reactor by helping of valves (13)— (14). Soap and other impurities that cannot be taken with glycerin are taken with tonsil in the further treatment. One of the most important points of the invention is that while separation and reaction are performed in the body of same reactor configuration, neutral oil or biodiesel is put into the part (B) at the start of each operation. In this way, neutral oil exchanged place with glycerin in the reaction passes to the reactor (A) and thus it takes back from the part (B) to the part (A) the oil that glycerin retained in the reaction and, as a result, does not adversely affect composition and performance of the reactor (A). Glycerin having hydrophilic character retains oil having hydrophilic structure, drawing it to the part (B). While neutral oil in the part (B) exchanges place with glycerin towards the part (A), it draws back the oil retained by glycerin into the part (A) due to hydrophobe- hydrophobe interaction into the part (A) (Figure 3). It was observed that this oil transfer (B) increased further when temperature was increased to 60-65 ⁰C. The biggest advantage of this invention compared to other conventional processes is minimum loss of oil due to hydrophobic interaction. It was seen that glycerin bears significant amount of oil in the reactors outside this reactor configuration. NOBA rector is a very efficient reactor for minimizing oil loss in this sense.

Objectives of this invention is to reduce time in the oil refining and minimize loss of refining (oil transforming to soap, oil borne by glycerin and loss of oil in washing) and removal of FFA in NOBA reactor, a new reactor configuration, without need of washing process.

Reactor configuration realized in order to achieve purpose of the invention is given in the attached Figures, namely:

Figure 1- Appearance of NOBA reactor configuration used for removal of free fatty acids from oils with high fatty acids.

Figure 2- Appearance of block diagram indicating removal of free fatty acids from the oils by means of the subject NOBA process of the invention.

Figure 3- Appearance of mechanism of precipitation of glycerin particle in NOBA reactor.

Parts in the figure are numbered and they are described below:

1. Supply valve for reagents necessary for FFA neutralization,

2. Supply valve for vegetable oil with having high content of free fatty acids, 3. Inlet valve for ammonium gas,

4. On-off check valve,

5. Pressure indicator,

6. Pedal mixer, 7. Deflection plate,

8. Reaction heating elements,

9. Watching window,

10. Connection pipe between divisions, 11. Gate valve,

12. Auxiliary valves used for transferring glycerin to further treatment,

13. Auxiliary valves used for sending oil removed from its free fatty acids and glycerin for further treatment,

14. Auxiliary valve used for taking oil removed from its free fatty acids from the reactor

15. Hot oil or steam jacket,

16. Heating jacket,

17. Alcohol tank,

18. Alcohol pump, 19. Line transferring alcohol to methoxide or glycerate tank,

20. Inlet for caustic or glycerin,

21. Methoxide or glycerate preparation tank,

22. Methoxide or glycerate pump,

23. Line transferring methoxide or glycerate to NOBA reactor, 24. Vegetable raw oil storage tank,

25. Oil pump,

26. Line transferring oil to NOBA reactor,

27. NOBA reactor configuration,

28. Raw glycerin pump, 29. Line transferring raw glycerin to storage tank,

30. Raw glycerin storage tank,

31. Line transferring raw glycerin to purification unit,

32. Glycerin purification unit,

33. Pure glycerin output line, 34. Pump for oil removed from its free fatty acids,

35. Line transferring oil removed from its free fatty acids to the alcohol recovery unit,

36. Alcohol recovery unit, 37. Condensated alcohol line,

38. Condensated alcohol storage tank,

39. Condensated alcohol output,

40. Pump for oil removed from its free fatty acids and alcohol, 41. Line transferring to the tonsiling line the oil removed from its free fatty acids,

42. Tonsiling unit,

43. Tonsilled oil pump,

44. Line transferring tonsilled oil to the filter press, 45. Filter press unit,

46. Filtered oil pump,

47. Line transferring filtered oil to storage tank,

48. Storage tank for oil filtered and removed from its free fatty acids,

49. Output line for oil filtered and removed from its free fatty acids.

Without restricting the protection claimed, the process shall be described in further detailed by examples given below.

EXAMPLE 1

After the part (B) of NOBA reactor was filled with neutral oil, 10 kg canola oil having 1% free fatty acids (FFA) content in the part (A) and heated at constant temperature of 60 ⁰C. Potassium hydroxide of 0.221% (90% purity) (w/w oil) was dissolved in methanol of 50 mL (CH₃OH) and added to the oil and reaction was realized in 75 rev./min. After reaction time of 15 minutes, glycerin of 275 g (5% w/w oil) (95% purity) was added to the reaction medium and glycerin was allowed for 20 minutes to precipitate in the part (B). Soap and acid test analyses were conducted in the reaction. After these analyses, it was observed that FFA content of neutralized oil reduced from 1% to 0.24% and FFA removal efficiency was 76%.

It was also observed in the soap test conducted 15 minutes after start of the reaction,

4832 mgKOH soap/g sample soap was in the reaction medium and after precipitation of glycerin added for purpose of removal of soap thus formed from the reaction medium, sample soap was detected to be present in the medium in amount of 362 mgKOH soap/g sample. At the end of the reaction, oil taken as 10 kg at the beginning remained 9.85 kg, with 1.5% loss of efficiency. When another reactor used other than NOBA by use of same reagents, loss of efficiency was 3% and it was 4.7% for classical refining operations.

EXAMPLE 2

After the part (B) of NOBA reactor was filled with neutral oil, 10 kg canola oil having 1% free fat acid (FFA) content in the part (A) and heated at constant temperature of 60 ⁰C. Sodium hydroxide (NaOH) of 0.142% (w/w oil) was dissolved in methanol of 50 mL (CH₃OH) and added to the oil and reaction was realized in 75 rev./min. After reaction time of 15 minutes, glycerin of 275 g (5% w/w oil) was added to the reaction medium and glycerin was allowed for 20 minutes to precipitate in the part (B). Soap and acid test analyses were conducted in the reaction. After these analyses, it was observed that FFA content of neutralized oil reduced from 1% to 0.33% and FFA removal efficiency was 67%. It was also observed in the soap test conducted 15 minutes after start of the reaction, 4982 mgKOH soap/g sample soap was in the reaction medium and after precipitation of glycerin added for purpose of removal of soap thus formed from the reaction medium, sample soap was detected to be present in the medium in amount of 371 mgKOH soap/g sample. At the end of the reaction, oil taken as 10 kg at the beginning remained 9.75 kg, with 2.5% loss of efficiency. When another reactor used other than NOBA by use of same reagents, loss of efficiency was 5.5%.

EXAMPLE 3

After the part (B) of NOBA reactor was filled with neutral oil, 10 kg canola oil having 1% free fat acid (FFA) content in the part (A) and heated at constant temperature of 60 ⁰C. Potassium hydroxide of 0.221% (w/w oil) was dissolved in glycerin of 275 g (5% w/w oil) heated at temperature of 90-95 ⁰C and added to the oil and reaction was realized in 75 rev/min. After reaction time of 15 minutes, glycerin was allowed for 20 minutes to precipitate in the part (B). Soap and acid test analyses were conducted in the reaction. After these analyses, it was observed that FFA content of neutralized oil reduced from 1% to 0.11% and FFA removal efficiency was 89%. It was also observed in the soap test conducted 15 minutes after start of the reaction, 7820 mgKOH soap/g sample soap was in the reaction medium and after precipitation of glycerin added for purpose of removal of soap thus formed from the reaction medium, sample soap was detected to be present in the medium in amount of 849 mgKOH soap/g sample. At the end of the reaction, it was calculated that oil taken as 10 kg at the beginning remained 9.90 kg, with 1% loss of efficiency.

EXAMPLE 4

After the part (B) of NOBA reactor was filled with neutral oil, 10 kg canola oil having 1% free fat acid (FFA) content in the part (A) and heated at constant temperature of 60 ⁰C. Sodium hydroxide of 0.142% (w/w oil) was dissolved in glycerin of 275 g (5% w/w oil) heated at temperature of 90-95 ⁰C and added to the oil and reaction was realized in 75 rev./min. After reaction time of 15 minutes, glycerin was allowed for 20 minutes to precipitate in the part (B). Soap and acid test analyses were conducted in the reaction. After these analyses, it was observed that FFA content of neutralized oil reduced from 1% to 0.15% and FFA removal efficiency was 85%. It was also observed in the soap test conducted 15 minutes after start of the reaction, 8254 mgKOH soap/g sample soap was in the reaction medium and after precipitation of glycerin added for purpose of removal of soap thus formed from the reaction medium, sample soap was detected to be present in the medium in amount of 1905 mg KOH soap/g sample. At the end of the reaction, it was calculated that oil taken as 10 kg at the beginning remained 9.87 kg, with 1.3% loss of efficiency.

EXAMPLE 5

After the part (B) of NOBA reactor was filled with neutral oil, 10 kg canola oil having 5% free fat acid (FFA) content in the part (A) and heated at constant temperature of 60 ⁰C. Potassium hydroxide of 1.105% (w/w oil) was dissolved in methanol of 50 mL (CH₃OH) and added to the oil and reaction was realized in 75 rev./min. After reaction time of 15 minutes, glycerin of 275g (5% w/w oil) was added to the reaction medium and glycerin was allowed for 20 minutes to precipitate in the part (B). Soap and acid test analyses were conducted in the reaction. After these analyses, it was observed that FFA content of neutralized oil reduced from 5% to 1.7% and FFA removal efficiency was 66%. It was also observed in the soap test conducted 15 minutes after start of the reaction, 38354 mgKOH soap/g sample soap was in the reaction medium and after precipitation of glycerin added for purpose of removal of soap thus formed from the reaction medium, sample soap was detected to be present in the medium in amount of 7306 mgKOH soap/g sample. At the end of the reaction, it was calculated that oil taken as 10 kg at the beginning remained 9.40 kg, with 6% loss of efficiency. When another reactor used other than NOBA by use of same reagents, loss of efficiency was 9.5%.

Claims

1. It is a process for neutralization of free fatty acids (FFA) content of industrial and/or edible vegetable oils using an alkali catalyst (NaOH, KOH or NH₃) dissolution in an alcohol (methanol or ethanol) or in hot glycerin, characterized in that the process; wherein neutral oil or biodiesel is used in the glycerin collecting part of the reactor in two-part NOBA reactor configuration at the beginning of the operation.

2. According to Claim 1, wherein neutralization of free fatty acids (FFA) content of industrial and/or edible vegetable oils using an alkali catalyst (NaOH, KOH or NH₃) dissolution in an alcohol (methanol or ethanol) or in hot glycerin, characterized in that the process contains alcohol tank (17), methoxide preparation tank (21), storage tank for raw oil or waste oil with high content of FFA (24), NOBA reactor where neutralization and separation operations occur at same reactor (27), raw glycerin storage tank (30), tonsiling unit (42), alcohol recovery unit (38), filter press unit (45) and storage tank for filtered oil and removed from its free fat acid (48).

3. According to Claims 1 and 2, wherein neutralization of free fatty acids (FFA) content of industrial and/or edible vegetable oils using an alkali catalyst (NaOH, KOH or NH₃) dissolution in an alcohol (methanol or ethanol) or in hot glycerin, characterized in that the process; glycerin separation is performed in two-part reactor configuration.

4. According to the Claims 2 and 3, wherein neutralization of free fatty acids (FFA) content of industrial and/or edible vegetable oils using an alkali catalyst (NaOH, KOH or NH₃) dissolution in an alcohol (methanol or ethanol) or in hot glycerin, characterized in that the process; glycerin is taken from after neutralization reaction and reactor.

5. According to Claims 2 and 3, wherein neutralization of free fatty acids (FFA) content of industrial and/or edible vegetable oils using an alkali catalyst (NaOH, KOH or NH₃) dissolution in an alcohol (methanol or ethanol) or in hot glycerin, characterized in that the process; catalyst dissolves in hot glycerin.

6. According to Claims 2 and 3, wherein neutralization of free fatty acids (FFA) content of industrial and/or edible vegetable oils using an alkali catalyst (NaOH, KOH or NH₃) dissolution in an alcohol (methanol or ethanol) or in hot glycerin, characterized in that the process; the resulting soap is removed from reaction medium by use of glycerin.

7. According to Claims 2 and 3, wherein neutralization of free fatty acids (FFA) content of industrial and/or edible vegetable oils using an alkali catalyst (NaOH, KOH or NH₃) dissolution in an alcohol (methanol or ethanol) or in hot glycerin, characterized in that the process; stagnant zone is formed for separation of glycerin.

8. According to Claims 2 and 3, wherein neutralization of free fatty acids (FFA) content of industrial and/or edible vegetable oils using an alkali catalyst (NaOH, KOH or NH₃) dissolution in an alcohol (methanol or ethanol) or in hot glycerin, characterized in that the process; heating of the division where glycerin is collected.

9. According to Claims 2 and 3, wherein neutralization of free fatty acids (FFA) content of industrial and/or edible vegetable oils using an alkali catalyst (NaOH, KOH or NH₃) dissolution in an alcohol (methanol or ethanol) or in hot glycerin, characterized in that the process; glycerin is removed from the reaction medium by several steps.

10. According to Claims 2 and 3, wherein neutralization of free fatty acids (FFA) content of industrial and/or edible vegetable oils using an alkali catalyst (NaOH, KOH or NH₃) dissolution in an alcohol (methanol or ethanol) or in hot glycerin, characterized in that the process; variable mixing speeds are used in NOBA reactor in these Claims.