AU626014B2 - Production of alkyl esters from oils and fats - Google Patents

Description

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COMMONWEALTH OF AUSTRALIA PATENTS ACT 1952 COMPLETE SPECIFICATION (Original) FOR OFFICE USE Class Application Number: Lodged: Complete Specification Lodged: Accepted: Published: Int. Class ,0 p -fl S. S S. S Priority: Related Art: Name of Applicant: Address of Applicant: PALM OIL RESEARCH AND DEVELOPMENT BOARD and PETROLIAM NASIONAL Bhd No. 6, Persiaran Institusi, Bandar Baru Bangi, 43000 Kajang, Selangor, West Malaysia and Menara Dayabumi, Jalan Sultan Hishamuddin, 50050 Kuala Lumpur, West Malaysia *see.

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0 Actual Inventor(s) Prof. Ong Soon Hock Dr. Choo Yuen May Mr. Cheah Kien Yoo Mr. Abu Bakar Sheik Nasir Address for Service: DAVIES COLLISON, Patent Attorneys, 1 Little Collins Street, Melbourne, 3000.

Complete Specification for the invention entitled: "PRODUCTION OF ALKYL ESTERS FROM OILS AND FATS The following statement is a full description of this invention, including the best method of performing it known to us: -1- \'~uSBA ,of 2 PRODUCTION OF ALKYL ESTERS FROM OILS AND FATS The present invention relates to a novel process for the production of alkyl esters from oils and fats containing varying amount of free fatty acids (FFA). It further relates to a novel process of producing alkyl esters as a diesel fuel substitute. In another aspect it relates to the production of alkyl esters as oleochemical feedstock.

Oils and fats from natural sources, such as palm oil, contain varying amounts of free fatty acids (FFA). The presence of FFA in oils and fats inhibits the catalytic action of the alkaline catalyst in the transesterification process during the production of alkyl esters. Therefore the yield of alkyl esters is generally low resulting in IT uneconomic commercial production. Various methods are known for the preparation or manufacture of esters. But generally the yield of alkyl esters from these known methods is low and the methods are therefore economically not attractive.

It is therefore an object of the present invention to provide a novel and efficient method for the production of I alkyl esters from oils and fats, which can be carried out in an economical manner. A further object is to provide diesel iV fuel substitutes produced from natural oils and fats. Still i another object is to provide a novel process producing oleochemical feedstock from natural oils and fats. A further object of the invention is to provide a novel process capable of producing alkyl esters from natural oils and fats containing up to 100% free fatty acids (FFA). s According to one aspect of this invention, there is provided a process for the production of alkyl esters from natural oils and fats containing varying amounts of FFA i; I j iI 1 s 3 which comprises the steps of converting the FFA in the oils and fats into esters; transesterifying the oil fraction of the resulting product; separating the glycerol and the esters in the transesterification product; removing the alcohol from the esters and the glycerol by evaporation and; purifying the esters.

To obtain all the benefits of the invention it is desirable to use all the novel steps hereinafter described.

However, some of the benefits are obtainable by using only some of the steps so described. Accordingly, the process of the invention mayicomprise one or more of the following steps: 0 a) mixing the natural oils and fats with an alcohol and subjecting the mixture to an elevated temperature in o o the presence of a catalyst to effect conversion of the FFA into esters; b) separating the resulting reaction mixture into two fractions; the first fraction consisting substantially of alcohol and the second fraction consisting substantially of oil; o c) distilling part of the alcohol fraction from and recyling the remaining part of the fraction; d) heating the oil fraction from to remove the alcohol and any traces of water present; e) treating the oil fraction from with an alcohol and an alkaline catalyst at elevated temperature and pressure, to bring about transesterification; 4 f) continuously removing the glycerol formed in g) adding further amounts of the catalyst and/or the alcohol to push the transesterification reaction towards completion.

h) removing glycerol and alcohol from the product of i) purifying the esters contained in the product from By optimising the operating conditions in the various steps described above and by recycling solvents wherever possible, it is possible to produce a very high yield of the product with low losses of material.

SPreferred conditions for optimization are described hereinafter.

a) It is preferred that the natural oil or fat is mixed with alcohol in a molar ratio between 1:4 to 1:10 depending on the FFA content in the oil in the conversion of the FFA present in the oils and fats into esters. The resultant mixture is passed through a heat one.** exchanger. The temperature of the heat exchanger is preferably maintained between 60 C and 80 C with an i optimum of 70 C.

Sulphonated ion exchange catalyst is preferred as catalyst in the esterification of the FFA.

CI-C

8 alcohols for example, methanol, ethanol, etc., are the preferred alcohols for the esterification of FFA. It is also preferred to pass the mixture of alcohol and oil continuously through the reactor U containing the catalyst.

l_ b) After the esterification stage, it is preferred that the resultant effluent is separated into two layers.

Approximately 90% of the upper layer containing substantial concentration (approx 97%) of the alcohol used is recycled. The remaining 10% of the upper layer is distilled. The lower layer of the resultant effluent, which is substantially oil with a greatly reduced concentration of FFA, is further separated.

Removal of any water and alcohol present in the oil after separation is preferably carried out by heat treatment to temperatures considerably above 100 C.

Under such temperature conditions all traces of alcohol Sand water are evaporated away from the oil.

I 1 Sc) It is preferable that pretreated oil from the esterification stage is mixed with alcohol in a molar ratio of about 1:6 and 0.2 to 0.5% of sodium hydroxide, based on weight of oil, with a preferred optimum of 0.35% It is also preferred to maintain the reaction mixture above at temperatures between 50°C and 70 0 C, with a preferred optimum of 60 C.

d) The reaction mixture at the transesterification stage is preferably separated into two fractions; the first fraction consisting substantially of esters and the second fraction consisting substantially of glycerol, both fractions being continuously removed from the transesterification reaction mixture.

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6 e) The recovered ester fraction in is preferably further mixed with an alcohol, selected from CI-C 8 alcohols, and sodium hydroxide. The amounts of alcohol and sodium hydroxide required for this second stage transesterification reaction are equivalent respectively to about 5% and 30% of those used in f) The reaction mixture from the second transesterification stage is preferably separated into two fractions; first fraction consisting substantially of esters and the second fraction consisting substantially of glycerol, both fractions being continuously removed from the transesterification reaction mixture.

g) Removal of alcohol from the ester is preferably carried out by heating the mixture resulting from the transesterification stage to approximately 100 0

C.

h) Purification of the alcohol-free esters is preferably carried out by repeated water washing, preferably 2 to 3 times, and subsequent drying under vacuum.

A preferred embodiment of the process of production according to the invention is described with reference to Figures 1 and 2, which show a flow diagram of the production process. The example described and illustrated refers to the production of methyl esters from crude palm oil.

500 kg/hr of crude palm oil consisting of approximately 3% FFA flowing from line 1 is mixed with 85 kg/hr of pure methanol (99.85% pure) flowing from line 2 and part of recycled methanol (recovered in a downstream separation process) flowing from line 3. The mixture is heated to C by passing through the heat exchanger 5 and is then

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7 fed into esterification reactor 6. The mixture is contacted with a sulphonated ion exchange catalyst in the esterification reactor 6. The reaction mixture is then introduced into a separator 7 via a pipe system. The reaction mixture is separated into two layers in separator 7. 90% of the upper layer (containing approximately 97% r methanol) is separated and is subsequently recycled to the feed line 4 by line 3. The remaining 10% of the upper layer in the separator 7 is removed by line 8. The lower layer containing substantially palm oil with approximately 0.2% FFA is removed via line 9. The contents in line 8 and line o 9 are mixed and the resultant mixture is heated to a temperature of 100oC or slightly more by passing it through a heat exchanger 10 into a flash evaporator vessel

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11. In vessel 11 most of the methanol and any water present in the mixture is removed by evaporation through line 11A.

The resulting oil flowing out from vessel 11 is practically free of methanol and water and consists approximately 0.22% FFA. The said oil is mixed with 110 kg/hr of methanol and 1.2 kg/hr of sodium hydroxide (dissolved in methanol). The resultant mixture is passed through heat exchanger 13 via line 12 to bring the temperature of the mixture to The mixture from the heat exchanger 13 is passed to the first transesterification reactor 14.

The reaction mixture from reactor 14 is passed to a separator 15 where'it is again separated into an upper ester layer and a lower glycerol layer. The glycerol layer is

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drained off continuously via line 16 to the crude glycerol recovery system. The ester layer is continuously drained off via line 17, in which it is mixed with 5.75 kg/hr of methanol and 0.5 kg/hr of sodium hydroxide and the resultant mixture is transferred into the second transesterification reactor 18. The transesterification proceeds between 600 C '-i and 80C and at pressures between 1.1 x 105 N/m 2 and x 10 5 N/m 2 (5 bars). At the end of the reaction in the second transesterification reactor 18, about 98% of the oil is converted into methyl esters. The reactant mixture from reactor 18 is passed into separator 19.

The reactant mixture in separator 19 is again separated into an upper ester layer and a lower glycerol layer. The glycerol layer is drained off via line 20 to the crude glycerol recovery system. The ester layer comprising substantially methyl esters, with unreacted methanol and traces of glycerol is removed via line 21 to the ester purification system. The contents of line 21 are heated to 100 C by passage through a heat exchanger 22 and introduced into vessel 23. At the elevated temperature of about 100 C most of the methanol is vapourised and the methanol vapour is removed at atmosphere pressure via line 23A. The remaining portion of the ester layer with traces of methanol is transferred into vessel 24. Any last traces of methanol in vessel 24 is removed via line 24A under slight vacuum.

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The resultant liquid phase in vessel 24 is washed with about 100 Kg/hr hot water at about 70°C and the resultant mixture is transferred into separator 25. The waste water from the separator 25 is drained off via line 26. The S• overflow'from separator 25 is further washed with 50 kg/hr of hot water and transferred to separator 27, from which the waste water is drained off via pipe 28. The overflow from separator 27 is heated to about 100°C by passing the said overflow through the heat exchanger 29 and is discharged into vessel 30 under vacuum. The water vapour is removed by line 31. The resultant dry ester amounting to 475 kg/hr is transferred to the cooler 32 where it is cooled to about I I j 'M ft- l, .j 9 room temperature. The already cooled quantity of ester is transferred to the storage container.

As an auxiliary process to the transesterification process, it is a preferred embodiment of the invention to incorporate a glycerol recovery process. The glycerol recovery process will now be further described. The glycerol effluent from separators 15 and 19 flowing via piping means 16 and 20 respectively is mixed and the resultant mixture is heated to about 100 0 C by passing the same through a heat exchanger 33, from which the mixture is transferred to vessel 35 which is at an elevated temperature of about 100 C. The methanol present in the mixture is vapourised and the methanol vapour is removed from vessel 35 via line 34. About 65 kg/hr of crude glycerol of about concentration is transferred from vessel 35 to a storage tank (not shown).

As a further auxiliary process to the transesterification process it is preferred that the methanol recovered at various stages in the process be recovered and reused. The methanol vapour from lines 11A and l 24A is combined, and recovered and purified in a methanol 6 purification column 36. The resultant pure methanol from g from line 34 and 23A is recovered by condensor 37. The condensed methanol from condensor 37 can be used in the system without further purification as the methanol vapour at line 11A and 24A is relatively dry.

In the preferred embodiment described above, 500 Kg/hr of crude palm oil containing about 3% FFA required 57.5 Kg/hr of methanol to produce 475 Kg/hr of methyl esters and Kg/hr of crude glycerol of about 80% concentration.

c nrrt Specifications of crude palm oil used and methyl esters produced in this invention are as follows: TABLE 1 Specification of Crude Palm Oil 500@ *5

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Moisture and impurities Specification of Methyl Esters %wt %wt 3.000 0.250 Fuel apect

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Flash point0 Sulphur content %wt Kinematic Viscosity cst 40 0

C

Conradson Carbon Residue on Distillation Residue %wt Distillation temperature 90% point

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Cetane number Gross heat of combustion NJ/Kg 155.000 0.130 4 .658 0.220 336.000 64.000 39.800 ii) Oleochemical Aspect Colour (Lovibond 5 1/4" cell) Acidity (as palmitic acid) %wt Saponification number mgKOH/g 76R lB 0.160 196.000

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11 iii) Fatty Acid Composition %wt C 12:0 C 14:0 C 16:0 C 18:0 C 18:1 C 18:2 C 18:3 C 20:0 0.2 44.3 4.3 40.5 9.2 0.3 0.2

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0 Example taken from the patent specifications as described hereinbefore indicates some of the applications of the process. Laboratory trials using 200 gms of palm oil 150 ml of methanol and a base catalyst comprising preferably of sodium hydroxide or sodium metal were conducted. The palm oil used was varied from RBD palm oil to crude palm oil with 1.7% and 3.9% free fatty acid respectively. The said oil was first neutralised with an appropriate quantity of sodium hydroxide. The yield of esters was determined quantitatively as follows: the esters layer was separated from the glycerol layer, and washed with distilled water till the washing was neutral. The first portion of ester was obtained. The now separated glycerol layer was extracted 3 times with petroleum ether b.p. at 60 C C. The petroleum ether extract was washed with water and petroleum ether was removed under rotary evaporation.

The second portion of ester was obtained. Both esters and were combined and dried over sodium sulphate (Na 2

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4 overnight and filtered. The residue after filtration was rinsed with petroleum ether to obtain the residual ester.

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3 1 12 Using the method as described above crude palm oil (CPO) and crude palm stearin (CPS) were transesterified into methyl, ethyl and isopropyl esters. Yield results are as shown in Table 2.

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4 a se a 00 0 00* s 00 :0 .0 TABLE 2 Preparation of Methyl, Ethyl and Isopropyl Esters of Crude Palm Oil and Crude Palm Stearin for Fuel Evaluation via Transesterification Esters Catalyst Amount of Reaction Alcohol Wt of oil Yield Catalyst Temp/ 0 C /litre used/kg Methyl (CPS) NaOH .0.2 wt 60+3 1.1 1.5 94% Ethyl (CPS) Na 1 wt 75+1 0.75 1 73% Isopropyl(CPS) Na 0.8 wt 80+1 1 1.2 77% Methyl (CPO) NaOH 0.2 wt 60+3 0.75 1.5 Ethyl (CPO) Na 1 wt 75+1 0.75 1 Isopropyl(CPO) Na 1 wt %80+1 0.75 1 14 An important feature of the invention is that the fuel characteristics of the alkyl esters produced according to the specification are highly comparable to diesel oil produced from petroleum. The main characteristic of the alkyl esters is the very low sulphur content. Table 3 shows some important fuel characteristics of the alkyl esters produced according to the invention.

4 5e4* u 15 TABLE 3 FUEL CHARACTERISTIC OF ALKYL ESTERS OF CRUDE PALM OIL AND CRUDE PALM STEARIN PRODUCT ETHYL ESTER ISO-PROPYL ETHYL ESTER ISO-PROPYL OF CRUDE ESTER OF OF CRUDE ESTER OF TEST PALM OIL CRUDE PALM PALM STEARIN CRUDE PALM CONDUCTED (DISTILLED) OIL (DISTILLED) STEARIN (DISTILLED) (DISTILLED)

SPECIFIC

GRAVITY 0.8620 77.0 0.8535 76.0 0.8635 73.0 0.8555 72.0 ASTM D 1298 o

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COLOUR

(VISUAL) COLOURLESS COLOURLESS COLOURLESS CASTROL CASTROL SMELL SMELL

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CONTENT

IP 242 WT

CASTROL

SMELL

0.03

CASTROL

SMELL

0.06 0.025 0.02 VISCOSITY 0 C 4.67 ASTM D 445 cSt 5.17 4.0

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o FOUR POINT ASTM D 97 0

C

10.0 4.71 13.0 16.0 5.24 13.0 16.0 CLOUD POINT 16.0 ASTM D 2500°C 7.0

DISTILLATION

I.B.P. °C 10% 20% °C 50%

°C

°C

F.B.R. °C

FINAL

RECOVERY ml.

CETANE INDEX ASTM D 976 n 86 328.0 336.0 338.0 340.0 350.0 365.0 99.0 296.0 318.0 322.0 330.0

-CRACKED

MAX TEMP.

355 0

C

330.0 335.0 337.0 340.0 350.0 362.0 275.0 314.0 318.0 330.0

-CRACKED

MAX TEMP.

348 0

C

87.0 98.0 83.0 53 54 51 53 0S S. 4

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CONBUSTION 39,694 40,376 39,904 39,211 ASTM D 2362

KJ/KG

REID VAPOUR

PRESSURE

ASTM D 323 Psi FLASH POINT PM cc ASTM D 93 0

C

CONRADSON CARBON RESIDUE ASTM WT 55@550 S S

Claims (13)

1. A process for the production of alkyl esters from natural oils and fats containing varying amounts of FFA which comprises the steps of converting the FFA in the oils and fats into esters; transesterifying the oil fraction of the resulting product; separating the glycerol and the esters in the transesterification product; removing the alcohol from the esters and the glycerol by evaporation and purifying the esters.

2. A process as claimed in Claim 1, which comprises one or more of the following steps: a) mixing the natural oils and fats with an alcohol and subjecting the mixture to an elevated temperature in the presence of a catalyst to effect conversion of the FFA into esters; b) separating the resulting reaction mixture into two fractions; the first fraction consisting substantially of alcohol and the second fraction consisting substantially of oil; c) distilling part of the alcohol fraction from and recyling the remaining part of the fraction; Sd) heating the oil fraction from to remove the alcohol and any traces of water present; e) treating the oil fraction from with an alcohol and an alkaline catalyst at elevated temperature and pressure, to bring about transesterification; L 17 f) continuously removing the glycerol formed in g) adding further amounts of the catalyst and/or the alcohol to push the transesterification reaction towards completion. h) removing glycerol and alcohol from the product of i) purifying the esters contained in the product from

3. A process as claimed in Claim 2, wherein in step (a) the natural oil or fat is mixed with the alcohol in a molar S ratio between 1:4 to 1:10, depending on the FFA content in the oil.

4. A process as claimed in Claim 2 or Claim 3, wherein the temperature in step is between 600 and 80 0 C. A process as claimed in any one of Claims 2 to 4, wherein the catalyst in step is a sulphonated o ion-exchange catalyst.

6. A process as claimed in any one of Claims 2 to wherein the alcohol in step is a C 1 -C 8 alcohol.

7. A process as claimed in any one of Claims 2 to 6, wherein in step the mixture of alcohol and oil is passed continuously through a reactor containing the catalyst.

8. A process as claimed in any one of Claims 2 to 7, wherein in step reaction mixture is separated into two Slayers, appro iatlyl90%a of the upper layer, which contains a substantial proportion of the alcohol used, is recycled, the remaining 10% of the upper layer is distilled and the A" ii Aprcs a limdi ayoe fCais2to5 18 lower layer of the reaction mixture, which is substantially oil with a greatly reduced concentration of FFA, is further separated.

9. A process as claimed in Claim 8, wherein removal of any water and alcohol present in the oil after separation is carried out by heat treatment at temperatures above 100°C. A process as claimed in any one of Claims 2 to 9, wherein in step pretreated oil from the esterification stage is mixed with alcohol in a molar ratio of about 1:6 and 0.2 to 0.5% of sodium hydroxide, based on the weight of oil, at a temperature between 50°C and

11. A process as claimed in any one of Claims 2 to "se: wherein the reaction mixture from the transesterification step is separated into two fractions; the first fraction consisting substantially of esters and the second fraction consisting substantially of glycerol, both fractions being continuously removed from the transesterification reaction o* mixture.

12. A process as claimed in any one of Claims 2 to 11, wherein in step the recovered ester fraction from step is mixed with a C 1 -C 8 alcohol and sodium hydroxide, the amounts of alcohol and sodium hydroxide used for this second stage transesterification reaction being equivalent respectively to about 5% and 30% of those used in step

13. A process as claimed in any one of Claims 2 to 12, wherein the reaction mixture from the second transesterification step is separated into two fractions; first fraction consisting substantially of esters and the second fraction consisting substantially of A r 19 glycerol, both fractions being continuously removed from the transesterification reaction mixture.

14. A process as claimed in any one of Claims 2 to 13, wherein removal of alcohol from the ester product in step is carried out by heating the mixture resulting from the transesterification step to appre imae-y 100 C. A process as claimed in any one of Claims 2 to 14, wherein in step purification of the alcohol-free esters is carried out by repeated water washing and subsequent drying under vacuum. 0

16. A process for the production of alkyl esters from natural oils and fats, substantially as hereinbefore described with reference to the Examples and/or the accompanying drawings. 1-7- The steps, felrar, nt on and ca ompound referred to or indicated in t fication and/or claims of this applicatio vidually or collectively, and any and all inations of any two or more of-.a-id-stopsor--Q-bues-,-- Dated this 18th day of October,1989 DAVIES COLLISON Patent Attorneys for PALM OIL RESEARCH AND DEVELOPMENT BOARD and PETROLIAM NASIONAL Bhd i \t iJ