DE102009006922A1 - Making fatty acid alkyl ester by transesterifying fats or oils with alkyl alcohol and a catalyst, comprises mixing fats or oils, alkyl alcohol and catalyst and separating fatty acid alkyl esters from a light and ester-rich phase and drying - Google Patents

Abstract

Producing fatty acid alkyl esters by transesterification of fats or oils with alkyl alcohols and a catalyst, comprises: adding fats or oils, alkyl alcohols and the catalyst in a mixing container and mixing; separating the mixture into a light, ester-rich phase and a heavy, glycerin-rich phase; separating the fatty acid alkyl esters from the light and ester-rich phase, washing and drying the fatty acid alkyl esters, where the fatty acid alkyl ester is added to an agent containing organic acid anhydrides. Independent claims are included for: (1) the agent for preventing sterol glycoside containing precipitates in the production of fatty acid alkyl esters; and (2) a device for producing the fatty acid alkyl esters comprising: a reaction zone (1, 4) with a mixing reactor (2, 5) for mixing fats or oils with alkyl alcohols and catalyst, a separator (3, 6) for separating the mixture into light, ester-rich phase and heavy, glycerin-rich phase, and a wash column (21) for separation of fatty acid from the light, ester-rich phase; a drying zone for drying the fatty acid alkyl esters; and at least a supply line (26, 28, 38) for supplying the agent.

Description

The The invention relates to the preparation of fatty acid alkyl esters by transesterification of fats and oils with alkyl alcohols in a production plant with at least one implementation stage consisting of a mixing reactor in which the fats and oils be mixed with the alkyl alcohols and a catalyst, and a separator in which the resulting mixture is transformed into a light, ester-rich phase and a heavy, glycerol-rich phase separated followed by the light, ester-rich one Phase fatty acid alkyl ester separates, washes and dries.

Processes for the conversion of vegetable oils or animal fats to fuels by transesterification of the glycerol-bound fatty acids (triglycerides) with short-chain alcohols, such as, for example, methanol, are known. So will in the FR 996 608 the transesterification of palm oil with methanol or ethanol in the presence of a strong inorganic acid, such as hydrochloric acid or sulfuric acid, described as a catalyst for the purpose of fuel production.

The FR 2 560 210 describes the preparation of a methyl, ethyl, propyl or butyl ester of fatty acids from vegetable oils or animal fats and the use of the product as a diesel fuel. The light, non-polar, fatty acid ester-containing phase is separated from the heavy, polar, glycerol-containing phase. To improve the combustion properties, the product phase is treated with an adsorbent.

In the in the WO 87/07632 A1 described method, the production of biofuel starting from triglycerides in a two-stage process, where first a substance containing crude triglycerides reacts with an alkanol in the presence of a catalyst to convert the fatty acids contained in the crude triglycerides containing substance into their alkyl esters. The product of the first process step is washed with an aqueous detergent to form a two-phase organic system, wherein the catalyst is transferred from the reaction mixture to the aqueous phase.

A modern process for the production of fatty acid methyl ester or fatty acid ethyl ester and glycerol by transesterification of fats or oils is in EP 0 532 767 B1 described. In this process, the reaction of the oil or fat with methanol or ethanol and an alkaline catalyst in the liquid phase to the products fatty acid methyl ester or fatty acid ethyl ester and glycerol, which are obtained separately and are value products of the process. The process works with at least two reaction stages, each reaction stage comprising a single or multistage mixing reactor and a separator for separating a light, ester-rich phase and a heavy, glycerol-rich phase. The heavy phase recovered in the separator of the second to last reaction stage is at least partially recycled to the mixing reactor of the first reaction stage. The ester products of the process after processing and purification as a so-called biodiesel represent a marketable product.

It it is known that the use of certain vegetable oils, in particular from cost-optimized oil work, in Conversion to fatty acid methyl ester or fatty acid ethyl ester (Biodiesel) to Feststoffausfällungen in the manufacturing process or during subsequent storage of the product at cold ambient temperatures can. This behavior is pronounced, for example, during use to observe soybean oil or palm oil. In the Processing of such oils is therefore an increased Maintenance required for the production plant. In addition, the availability and thus the productivity The production facility is restricted as it is for maintenance and elimination of Feststoffausfällungen except Operation must be taken. The precipitates can by mechanical processes, such as filtration or centrifugation, be separated.

Responsible for the formation of the precipitates are so-called sterol glycosides (SG), which are widespread herbal ingredients that result from the combination of a sugar (glucose) with a phytosterol. Phytosterols are plant hormones and are components of plant cell membranes. Known representatives are stigmasterol or campesterol, whose structural forms in 1a respectively. 1b are shown. In addition, on the US 4 112 218 directed.

In the WO 2007/076163 A2 describes the addition of an adsorbent or filtration aid to separate the solid precipitates from biodiesel and its subsequent removal by filtration or centrifugation. However, this treatment is possible in a simple manner only for the finished biodiesel product. The elimination of already occurred in the production precipitates can be done by this measure only at great expense. From the WO 2007/076163 A2 It is also known to bring biodiesel into contact with a component which can remove sterol glycosides from the biodiesel. As components for this are adsorbents, filter media, boric acid, soaps, sucrose, sugar, glucose, sodium chloride, citric acid, magnesium silicate, clay, silica, lecithin, proteins, carbon, cellulose, Lösun proposed with boric acid or silica hydrogel. However, the proposed components are only insufficiently able to eliminate precipitates caused by sterol glycosides. In addition, by treating the end product biodiesel, the problem of post-precipitation of remaining dissolved sterol glycosides can not be eliminated.

Preparative methods are known for converting sterol glycosides into acetylated products by reaction with acetic anhydride, which have good solubility in non-polar organic solvents, such as chloroform and cyclohexane ( US 4,235,992 ).

The Solubility of the acetylated sterol glycosides in fatty acid methyl esters is not known yet.

task The present invention is in the production of biodiesel the occurrence of precipitates based on sterol glycosides to avoid in the final product.

These The object is achieved with the invention essentially by that the biodiesel after drying with an agent (additive) is treated containing organic acid anhydrides. By the addition of such an additive before being precipitated in the biodiesel form on the basis of sterol glycosides, the Avoid formation of precipitates from the outset, so that the SG replenishment problems described above only do not ask.

When particularly suitable organic acid anhydride has become Acetanhydride (acetic anhydride) proved.

The Additive is preferably introduced in liquid form, for easy mixing with the raw materials or products to allow in the production of the fatty acid alkyl esters.

The Additive according to the invention during operation introduced after the first dryer stage in the production plant. The resulting in the reaction acetic acid is in a subtracted second dryer stage.

biodiesel with an SG content of at most 50 ppm can with acetic anhydride also be treated in a storage tank after drying by the biodiesel in the tank is pumped in the circulation. However, you have to then longer reaction times up to 6 hours accepted become. The acetic anhydride concentration must be calculated that the acid number (SZ) in the final biodiesel is not greater is 0.5 mg / g KOH. Preferably, in this Case limits the amounts of acetic anhydride to up to 500 ppm.

An additional option is the removal of the acid released by the acid anhydride reaction with sterol glycosides and / or water by basic ion exchangers as described in US Pat EP 1 018 501 are described. The ion exchanger can be placed in the recirculation line of a biodiesel storage tank or integrated at a suitable point between the drying unit and the filter unit.

A suitable ion exchanger is, for example, Amberjet 4400 OH from Rohm and Haas. The water contained in the biodiesel can be removed by a downstream adsorber or ion exchangers as Lewatit ^® K 2567 Lanxess.

The Regeneration of the ion exchanger or adsorber is carried out according to customary Procedures z. B. with dilute alkalis, water and hotter compressed air

Under These circumstances can according to the invention until to 2000 ppm acetic anhydride or other acid anhydride be applied.

Preferably the additive is in concentrated form or with the final product (Biodiesel) diluted in the process, wherein adjusted the concentration according to the requirements of the system can be.

Becomes according to a preferred embodiment the invention, the additive under pressure, with pulsating current and / or with elevated temperature similar to one High-pressure cleaner introduced into the production plant, so takes place the mixing with particularly high efficiency. By the attitude the temperature of the additive can simultaneously control the temperature of the Total current to be regulated.

The Means can be continuous, periodic or in time variable form are introduced into the production plant.

at The production of biodiesel is the fatty acid alkyl esters after separation in the separator, preferably in a wash column separated from the light, ester-rich phase and then dried. In development of the invention, therefore, the additive directly into the drying stage, the subsequent filtration stage or introduced into interposed pipelines, since these Plant components with regard to the formation of precipitates are particularly sensitive. In addition, the additive can into the storage tanks of the final product or the intermediate ones Pipelines are introduced.

According to a preferred embodiment of Invention, the additive is introduced in particular at points in the production plant, where only low local concentrations of at most 500 ppm of water and / or monohydric or polyhydric alcohols are present, especially after the ester drying.

To In another embodiment of the invention, the acid anhydride, in particular acetic anhydride, in the 60 to 120 ° C hot Fatty acid alkyl ester immediately after drying in a Pipeline fed and the low boilers contained removed by another vacuum drying step.

The The invention also includes an agent for preventing sterol glycosides containing precipitates in fatty acid alkyl esters, wherein the agent comprises organic acid anhydrides, such as acetic anhydride, contains.

According to one preferred embodiment of the invention can be dissolved in biodiesel Acetic anhydride as an additive, especially in the dryer and filter stage be used.

A Inventive plant for the production of fatty acid alkyl esters by transesterification of fats and oils with alkyl alcohols, those for carrying out the method described above is suitable, has at least one reaction stage with a mixing reactor for mixing the fats and oils with the alkyl alcohols and a catalyst and a separator in which the mixture in a light, ester-rich phase and a heavy, glycerol-rich phase is separated, a wash column for the separation of fatty acid alkyl esters from the light, ester-rich phase, a drying stage for drying the fatty acid alkyl ester and at least one supply line for the supply of the agent described above to the process stages Drying filtration, intermediate storage and / or in between or thereafter provided pipelines.

Further developments, Advantages and applications of the invention result also from the following description of exemplary embodiments and the drawing. All are described and / or illustrated illustrated features alone or in any combination the subject of the invention, regardless of its summary in the claims or their dependency.

It demonstrate:

1a the structural formula of stigmasterol as an example of a sterol glycoside,

1b the structural formula of campesterol as an example of a sterol glycoside and

2 schematically a plant for carrying out the method according to the invention.

In the 2 schematically illustrated plant for the production of fatty acid alkyl esters by transesterification of fats and oils with alkyl alcohols has two reaction steps. In the illustrated embodiment, methanol is used as the alcohol, but the process can be carried out in the same way with ethanol to produce ethyl ester.

The first implementation stage 1 has a mixing reactor 2 and a subsequent gravitational separator 3 on. Accordingly, also the second implementation stage 4 a mixed reactor 5 and a gravity separator 6 on. The starting oil or fat flows through a pipe 7 in the mixing reactor 2 , The reactor 2 one leads further by a line 8th largely anhydrous methanol and a catalyst and through the line 9 heavy, glycerol-containing phase from the second reaction stage 4 to. The catalyst is passed through the line 10 introduced and mixed with the methanol. In the reactor 2 Intensive mixing takes place with the aid of at least one stirring device 11 , The mixing reactor 2 may comprise a plurality of cascaded mixing chambers in a known manner.

The temperatures in the mixing reactor 2 are usually in the range of 40 ° C to the boiling point of the mixture. When working at atmospheric pressure, temperatures up to 68 ° C. have proven to be expedient. At higher pressures, temperatures up to 90 ° C are reasonable. Between the mixing reactor 2 and the separator 3 a cooling not shown here may be provided to the separation in the separator 3 to facilitate. As a gravity separator is preferably used fiber bed, known per se and, for example. In "Filtration and Separation", September / October 1990, pages 360 to 363 are described.

In the separator 3 Draw a light, methyl ester-rich phase, which is passed through the line 12 to the mixing reactor 5 the second implementation stage 4 leads. The in the line 13 withdrawn heavy, glycerol-rich phase is combined with the wash water from a wash column 21 after pH adjustment to 1.5-2.0 in a collecting line 23 for rectification of a column 14 given up. In the known rectification column 14 you win over head largely anhydrous methanol, which is in the line 15 withdraws and the methanol of the line 8th admits. From the bottom of the column 14 you go through a pipe 16 a glycerol / water mixture, which is used to separate the fatty acid and methyl ester constituents dispersed in the glycerine water into a gravity separator Temperatures of 50 ° C to 90 ° C supplies. As a light phase, the fatty substance forms ("Fatty Matter") and is withdrawn continuously. The heavy water-glycerol phase becomes an evaporator 17 fed and the water separated. The crude glycerol with a water content of 2 to max. 10% is over a line 18 fed to a cleaning, not shown.

The second implementation stage 4 one leads next to the light, methyl ester-rich phase from the separator 3 over a line 19 a mixture of methanol and catalyst. Before entering the mixing reactor 5 can the tempera ture of the methyl ester-rich phase of the line 12 lowered or raised in a heat exchanger, not shown. In the mixed reactor 5 , in which again intensive mixing takes place, the temperature is about the same as in the mixing reactor 2 , In front of the separator 6 In turn, a cooling, not shown, may be provided.

The heavy, glycerol-rich phase, in the separator 6 accumulates, is through the line 9 to the mixing reactor 2 recycled. The light, methyl ester-rich phase (crude ester) passes through the line 20 to an intensive mixer 32 in which the alkaline raw ester for neutralization with over a line 31 mixed dilute hydrochloric acid is mixed, so that in the subsequent separator 33 the separation into a light, methyl ester-rich phase and a heavy, sodium chloride-containing acidic methanol-water phase takes place. The heavy, acidic methanol-water phase is piped over 34 the manifold 23 fed. The light, methyl ester-rich phase is passed through the pipeline 20 a wash column 21 fed, which one over the line 22 that in the evaporator 17 supplied water feeds. The water absorbs the water-soluble substances, especially methanol, glycerol, salts and the excess salts of the upstream catalyst neutralization. The aqueous phase, which contains methanol and glycerol and is virtually free of methyl ester, is passed over the line 23 the glycerol-rich phase of the line 13 which are admixed after separation of the fatty substance of the rectification column 14 gives up.

On the other hand, from the wash column 21 over the line 24 Deducted fatty acid methyl ester, which can be used as biodiesel. Since the water content for this is still too high, it is by heating in a heat exchanger, not shown, and subsequent drying, eg. Vacuum drying, in a drying step 25 reduced, so that a largely dried product with a biodiesel specification corresponding to the maximum water content of 0.05% results. Finally, the biodiesel end product is in a filter unit 29 freed from contamination and stored in a product tank.

Around in the production of fatty acid alkyl esters described above the formation of precipitates based on sterol glycosides To avoid the production plant is fed a means that contains organic acid anhydrides. It has become the use of acetic anhydride has been found to be particularly effective and is compared to other organic acid anhydrides, such as phthalic anhydride, propionic anhydride, Succinic anhydride, significantly cheaper.

The additive is introduced in liquid form during operation in the production plant, wherein it via a supply line 26 . 28 in the drying stage 25 or in subsequently planned pipelines 27 is introduced. Preferably, the addition is effected by a supply line 28 in front of the filter unit 29 , The additive can be introduced under pressure, with pulsating current and / or at elevated temperature via corresponding flushing nozzles in the production plant to achieve a particularly high effect similar to a high-pressure cleaner. Following the addition of the additive is another drying step 30 For example, in the form of a spray-drying, provided to remove the low boilers formed, acetic acid and water.

Alternatively or additionally, an ion exchanger / adsorber unit 37 for removing acetic acid and water from the biodiesel after the dryer (heat exchanger) 25 . 38 be provided. The biodiesel here has a temperature of about 30 ° C.

After filtration and introduction into the collection or storage tank 35 The biodiesel can be pumped via a pumping line 36 be pumped. In this case, the metering 38 the organic acid anhydrides and the ion exchanger / adsorber unit 37 advantageously in the recirculation line 36 be provided.

By the addition of the additive will cause the formation of solid precipitates reliably prevented in the biodiesel end product.

1

first conversion stage

2

mixing reactor

3

separators

4

second conversion stage

5

mixing reactor

6

separators

7

management

8th

management

9

management

10

management

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agitator

12

management

13

management

14

column

15

management

16

management

17

Evaporator

18

management

19

management

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management

21

washing column

22

management

23

management

24

management

25

drying stage

26

supply line

27

pipeline

28

supply line

29

filter unit

30

drying stage

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hydrochloric acid line

32

mixing device

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separator

34

management

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tank

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management

37

Ion exchanger / adsorber

38

supply line

QUOTES INCLUDE IN THE DESCRIPTION

This list The documents listed by the applicant have been automated generated and is solely for better information recorded by the reader. The list is not part of the German Patent or utility model application. The DPMA takes over no liability for any errors or omissions.

Cited patent literature

• FR 996608 [0002]
• - FR 2560210 [0003]
• WO 87/07632 A1 [0004]
• - EP 0532767 B1 [0005]
• - US 4112218 [0007]
• - WO 2007/076163 A2 [0008, 0008]
• - US 4235992 [0009]
• - EP 1018501 [0017]

Cited non-patent literature

• - "Filtration and Separation", September / October 1990, pages 360 to 363 [0037]

Claims (20)

A process for the preparation of fatty acid alkyl esters by transesterification of fats or oils with alkyl alcohols and a catalyst, wherein the fats or oils and the alkyl alcohols and the catalyst introduced into at least one mixing vessel, mixed and then in at least one separator in a light, ester-rich phase and a heavy , Glycerinreiche phase are separated and wherein one separates from the light, ester-rich phase fatty acid alkyl ester, washed and dried, characterized in that the fatty acid alkyl ester is added to an agent containing organic acid anhydrides. Method according to claim 1, characterized in that that the agent contains a component selected from the group consisting of acetic anhydride, phthalic anhydride, propionic anhydride, Succinic anhydride or mixtures thereof becomes. Method according to claim 1 or 2, characterized that the agent is introduced in liquid form. Method according to one of the preceding claims, characterized in that the means during operation in the production plant is introduced. Method according to one of the preceding claims, characterized in that the means by separate supply lines is introduced into the production plant. Method according to one of the preceding claims, characterized in that the agent is concentrated or diluted Form is introduced into the production plant. Method according to one of the preceding claims, characterized in that the means under pressure, with pulsating Electricity and / or elevated temperature in the production plant is introduced. Method according to one of the preceding claims, characterized in that the means is continuous, periodic or introduced into the production plant in time-variable form becomes. Method according to one of the preceding claims, characterized in that the agent enters the drying stage, a subsequent filtration step to collect the final product or storage tank and / or introduced in between pipelines becomes. Method according to one of the preceding claims, characterized in that the means at points in the production plant introduced at which only low local concentrations, in particular not more than 500 ppm, of water and / or mono- or polyhydric alcohols are present. Method according to claim 10, characterized in that that the fatty acid alkyl ester after introduction of the agent is dried again. Method according to one of the preceding claims, characterized in that formed after introduction of the agent Acid and / or water is removed from the product. Method according to claim 12, characterized in that that the acid and / or water by ion exchange and / or Adsorption is removed from the product. Agent for preventing sterol glycosides containing Precipitates in the production of fatty acid alkyl esters by transesterification of fats or oils with alkyl alcohols and a catalyst, in particular in a method according to one of the preceding claims, characterized in that the agent contains organic acid anhydrides. Agent according to claim 14, characterized that the agent contains a component selected from the group consisting of acetic anhydride, phthalic anhydride, propionic anhydride, Succinic anhydride or mixtures thereof becomes. Plant for the preparation of fatty acid alkyl esters by transesterification of fats or oils with alkyl alcohols, with at least one reaction stage ( 1 . 4 ), which is a mixed reactor ( 2 . 5 ) for mixing the fats or oils with the alkyl alcohols and a catalyst and a separator ( 3 . 6 ), in which the mixture is separated into a light, ester-rich phase and a heavy, glycerol-rich phase, a wash column ( 21 ) for the separation of fatty acid alkyl esters from the light, ester-rich phase and a drying step ( 25 ) for drying the fatty acid alkyl esters, characterized by at least one feed line ( 26 . 28 . 38 ) for the supply of an agent according to any one of claims 14 or 15 in or after the drying step ( 25 ). Plant according to claim 16, characterized in that after the supply line ( 28 ) for introducing the agent, a further drying stage ( 30 ) is provided. Plant according to claim 16 or 17, characterized characterized in that after the supply line ( 26 . 28 . 38 ) for introducing the agent one or more ion exchange or adsorber ( 37 ) are provided Installation according to one of claims 16 to 18, characterized in that a collecting or storage tank ( 35 ) for the end product a pumping line ( 36 ), in which the product is pumped around, and that the at least one ion exchange or adsorber stage ( 37 ) in the pumping line ( 36 ) is provided. Use of an agent according to claim 14 or 15 to prevent precipitates containing sterol glycosides in fatty acid alkyl esters.