DE102008058393A1 - Alumina-containing adsorbents for the purification of biodiesel - Google Patents

Abstract

The invention relates to a method for purifying biodiesel, wherein:
- a raw biodiesel is provided;
- The crude biodiesel is reacted with an adsorbent containing at least one alumina-containing component having an aluminum content, calculated as Al ₂ O ₃ , of more than 40 wt .-%; and
- A purified biodiesel is separated from the adsorbent.

Description

The The invention relates to a process for the purification of biodiesel, biodiesel precursors, vegetable or animal fats and mixtures thereof.

biodiesel because of its origin from renewable raw materials in the Burn a neutral carbon footprint on. Carbon dioxide belongs to the greenhouse gases whose emission you are pushing back trying to counter the global warming of the climate. Biodiesel is said to play an important role as a substitute for Play diesel fuels derived from fossil sources. This is also promoted by state measures. Within the European Union, for example, one Proportion of biodiesel in diesel fuels required by law.

biodiesel is prepared by the alcoholysis of triglycerides, wherein one mole Triglyceride with three moles of alcohol to one mole of glycerol and three Mol of the corresponding fatty acid ester reacts. The implementation includes three reversible reactions, the triglyceride gradually into a diglyceride, a monoglyceride and finally is converted to glycerol. At each of the steps In each case one mole of alcohol is consumed and one mole of a fatty acid ester released.

Alcoholysis can be carried out under both acidic and basic catalysis. In the industrial production of biodiesel, the alcoholysis is usually carried out under alkaline catalysis, since the reaction proceeds under mild conditions at a high conversion rate and therefore relatively fast. The alkaline catalysts used usually have a less corrosive effect on the synthesis reactors, so that, for example, a relatively inexpensive carbon-containing steel can be used for plant construction. In most industrial processes, the alcoholysis of the triglycerides is carried out under homogeneous alkaline catalysis. The alkoxide ion acting as a catalyst is produced by, for example, dissolving an alkali metal alcoholate in alcohol or reacting the pure alkali metal with the alcohol. In the methanolysis, a corresponding alkali metal hydroxide can be dissolved in methanol. Since in the alcoholysis of triglycerides phase separation by the resulting glycerol occurs relatively quickly, the major part of the alkaline catalyst is relatively quickly removed from the reaction mixture. The resulting fatty acid esters therefore hardly come into contact with the catalyst, so that the risk of saponification is low. Based on the oil used, the catalyst is usually used in an amount of 0.5 to 1 wt .-%. Details of biodiesel production will be on the Monograph by M. Mittelbach, C. Remschmidt, "Biodiesel; The Comprehensive Handbook ", Graz, 2004; ISBN 3-200-00249-2 directed.

The Triglycerides used as starting materials can be, for example gain from vegetable or animal fat. With the vegetable raw materials In the worldwide production of biodiesel, palm oil is the main ingredient and soy used. Of local importance still rapeseed oil and sunflower oil. Other starting materials, which have a commercial significance are animal fats, such as Beef tallow, as well as used frying fats. For the future are also oils from the Jatrophanuss and algae as Commodities discussed.

In order to ensure a uniform combustion of the biodiesel, the content of mono-, di- and triglycerides, as well as of soaps and glycerol, must be reduced as much as possible. To DIN EN 14214 Biodiesel may contain up to 0.2% by weight of monoglycerides, up to 0.8% by weight of diglycerides and up to 0.02% by weight of triglycerides. The resulting in the production of biodiesel soaps must also be removed from the biodiesel, otherwise ash can form during combustion, which can be deposited and lead to damage to the diesel engine. In order to remove soaps, as well as residual alcohol, glycerol, mono- and diglycerides from the biodiesel, a water wash is therefore usually carried out after transesterification. If the raw biodiesel contains large amounts of soaps, a stable emulsion can form, which makes the separation of the fatty acid esters considerably more difficult.

Currently The majority of biodiesel is produced by alcoholysis the triglycerides produced with methanol. As the proton of the hydroxy group methanol is relatively acidic, methanol is relatively easy by conversion with NaOH into the appropriate methanolate, which then causes the transesterification of the glyceride. Disadvantageous However, this method is the high toxicity of methanol. Furthermore, methanol is produced petrochemically, so that only one Part of the biodiesel is based on renewable raw materials.

As an alternative to methanolysis, methods are developed in which the triglycerides are cleaved using ethanol. This method has the advantage that both the fatty acid compo nents as well as the ethanol can be obtained from renewable raw materials. Biodiesel based on fatty acid ethyl esters is therefore of particular interest for those countries in which large quantities of bioethanol are produced, for example Brazil or the USA.

ethanol has a lower acidity compared to methanol on. The pKa of ethanol is 15.9 during Methanol has a pKa of 15.5. Water has a pKa of 15.7 on. In the ethanolysis of triglycerides is therefore in contrast For methanolysis, the saponification of glycerides by water is the preferred one Reaction. The reaction is not complete so that in the reaction mixture after the ethanolysis in addition to the fatty acid soaps even larger amounts of mono-, di- and triglycerides available. It therefore often occurs with the released glycerol the formation of a very stable microemulsion. This makes it difficult the separation of glycerol considerably. The glycerin can pass through Centrifugation can be separated or the emulsion can be broken by washing the mixture with a strong acid so that the soaps are converted into the corresponding fatty acids become.

But even after such a purification contains the biodiesel still relatively high levels of mono-, di- and triglycerides. In many Cases the biodiesel produced in this way is still contaminated with up to 2 wt .-% monoglycerides. It fulfills hence not the specification for use as a diesel fuel.

Biodiesel is made from natural resources. After alcoholysis, biodiesel therefore contains, in addition to soaps, mono-, di- and triglycerides, further impurities which vary in their proportions as well as in their composition within wide limits. These contaminants can also lead to difficulties in the production or use of biodiesel. For example, when biodiesel is cooled to room temperature after production, or even when stored for an extended period of time, small amounts of a fine, sparingly soluble precipitate often fall out. This fine precipitate can then cause, for example, the clogging of filters. Often the fine precipitate consists of glycosides. In biodiesel, which is made from vegetable material, the precipitate often consists of steryl glycosides. Sterols are cholesterol-derived glycosides that only have a hydroxy group at C ₃ , but no other functional groups. Most of them have a double bond in 5/6 position, more rarely in 7/8 or 8/9 position. They are formally alcohols and are therefore often referred to as sterols. Naturally occurring steryl glycosides often include, in addition to the glycosidically linked steryl radical, a fatty acid with which the primary hydroxyl group of the sugar is acylated. They are therefore very well soluble in vegetable or animal fats. It is also believed that during the alcoholysis of the triglycerides, the acyl group on the primary hydroxy group of the steryl glycosides is cleaved to give an unacylated steryl glycoside. These non-acylated steryl glycosides are almost insoluble in biodiesel. They are therefore present as very fine suspended particles, which can act, for example, as nuclei for the crystallization of other compounds. Non-acylated steryl glycosides can cause the precipitation of solid aggregates of biodiesel even in very low concentrations. Even concentrations in the double-digit ppm range can lead to the formation of turbidity in biodiesel at room temperature. Non-acylated steryl glycosides have a very high melting point of about 240 ° C. Turbidity or precipitation caused by non-acylated steryl glycosides can therefore not be resolved by heating the biodiesel to a higher temperature. Thus, if deposits already exist on a filter, it clogs relatively quickly in the presence of non-acylated steryl glycosides in the biodiesel.

To In the production process the biodiesel becomes a final one Examined. It is found that the test to block filters is not passed, because that in itself finished biodiesel still very small amounts of non-acylated steryl glycosides contains, this biodiesel can not be released.

One Known from the prior art method for the separation of Ingredients, such as of steryl glycosides, from biodiesel Based on the fact that the raw biodiesel cooled to low temperatures and then filtered. This procedure is however extremely complex in its execution.

The WO 2007/076163 A describes a method of treating biodiesel with adsorbents and the like to remove sterol glycosides. Various adsorbents are described, with glucose, diatomaceous earth, clays and in particular magnesium silicate being used as the adsorbent in the examples.

In the WO 2008/055676 A describes a method for purifying a crude biodiesel, wherein as adsorbent, a clay material having a specific surface area of more than 120 m ² / g, a cumulative Pore volume of 0.35 ml / g and a SiO ₂ content of more than 60 wt .-% is used.

In the US 2005/0188607 A1 describes a process for the purification of crude biodiesel, wherein in particular methanol is removed. The plant for the production of biodiesel comprises a first section in which a crude biodiesel is prepared by reacting the oil used as starting material with methanol in the presence of a catalyst. In a second section, excess methanol is recovered from the crude biodiesel. For this purpose, a portion of the methanol is first distilled off from the crude biodiesel. In order to remove any remaining portions of methanol in the biodiesel, the prepurified biodiesel is then mixed with an adsorbent, for example magnesium silicate. The adsorbent is left in the biodiesel for about 10 to 15 minutes and then the purified biodiesel is separated from the adsorbent by filtration.

In the WO 2007/143803 A1 a process for the transesterification of vegetable or animal fats under base catalysis is described. The catalysts used are strong bases which contain no metal ions. As a result, no soaps are to be formed in the transesterification, whereby the formation of emulsions can be avoided when washing the crude biodiesel with water. Guanidine hydroxides having a pKa in the range of 13.6 to 13.9 and quaternary ammonium hydroxides or alkoxides of guanidine are used as the base for the transesterification. The catalyst can be used both in homogeneous phase and in heterogeneous phase. The catalysts are useful for the alcoholysis of triglycerides using both methanol and ethanol.

In the WO 2005/037969 A2 describes a process for the purification of biodiesel, wherein the crude biodiesel is reacted with magnesium silicate as the adsorbent.

As already stated above, offers the use of ethanol in the alcoholysis of triglycerides the possibility of one Produce biodiesel whose starting materials from renewable Raw materials can be obtained. A disadvantage of the method is, however, that the obtained biodiesel is still relatively large Contains amounts of impurities, in particular mono-, Di- and triglycerides, soaps and glycosides, so one such Ethyl biodiesel often does not meet the specifications, for example, for use in internal combustion engines are predetermined.

Of the The invention was therefore based on the object, a method for cleaning of biodiesel providing efficient removal of impurities from raw biodiesel allows and which in particular for the purification of crude Ethylbiodiesel suitable is.

These The object is achieved by a method having the features of the patent claim 1 solved. Preferred embodiments of the invention Method are the subject of the dependent claims.

According to the invention was found that by using an adsorbent, which is a high proportion Contains alumina, very efficient impurities can be removed from raw biodiesel. The procedure can be used to clean raw biodiesel, as it is obtained immediately after the alcoholysis, in particular after separation of the glycerol phase. The procedure leaves But also for the subsequent purification of biodiesel use, which still contains small amounts of impurities and, for example a certain specification is not met. The invention Procedure can also be routinely considered final Cleaning stage for further refining an already pre-cleaned Biodiesels are used.

• – ein rohes Biodiesel bereitgestellt wird;
• – das rohe Biodiesel mit einem Adsorbens umgesetzt wird, welches zumindest eine aluminiumoxidhaltige Komponente enthält, welche einen Aluminiumanteil, berechnet als Al₂O₃, von mehr als 40 Gew.-% aufweist; und
• – ein gereinigtes Biodiesel von dem Adsorbens abgetrennt wird.

According to the invention, therefore, a method for purifying biodiesel is provided, wherein

• - a raw biodiesel is provided;
• - The crude biodiesel is reacted with an adsorbent containing at least one alumina-containing component having an aluminum content, calculated as Al ₂ O ₃ , of more than 40 wt .-%; and
• - A purified biodiesel is separated from the adsorbent.

At the inventive method is first provided a raw biodiesel.

By "biodiesel" is meant a mixture of fatty acid alkyl esters commonly obtained in the alcoholysis of natural fats and oils. Alcoholysis may have been carried out under both acidic and alkaline catalysis. Alcohols customary for the production of biodiesel alcohols can be used as alcohols, for example methanol, ethanol or propanol. As natural fats and Oils can be used for those fats and oils commonly used in the production of biodiesel. If reference is made to "fats" below, oils should also be included. Likewise, fats should also be recorded when referring to oils.

Under Fats and oils generally become longer chain triglycerides Understood fatty acids. The fatty acids include preferably more than 10 carbon atoms and preferably comprise 15 to 40 carbon atoms. The alkyl chain of fatty acids is preferably straight-chain. It can be completely hydrogenated or include one or more double bonds. suitable Starting materials are vegetable fats, such as rapeseed oil, Sunflower oil, soy or palm oil. But it can also be used other vegetable fats, like jatropha oil or oils derived from algae become. These oils are not suitable for consumption the people. In addition, for the Production of these plants agricultural land be used for the production of food are not suitable. For example, the jatrophan nut may also be on very barren soils are cultivated for a Cereal production are not suitable. Next can also animal fats are used, such as beef tallow. It is also possible, Used fats, such as frying fats to use. It can Both oils and fats are used on just one Go back source. But it is also possible Mixtures of fats or oils to use. The fats or oils are preferably purified prior to alcoholysis in a known manner and, for example, degummed and / or deodorized. After a preferred embodiments are for the alcoholysis Fats or oils with a lecithin content of less than 10% by weight, in particular less than 5% by weight, more preferably less than 10 ppm, especially less than 5 ppm used.

These Fats and oils are usually made by alcoholysis split into glycerol and fatty acid ester. Alcoholysis is preferably carried out under alkaline catalysis. As alcohols can used in the production of biodiesel conventional alcohols be such as methanol, ethanol or propanol. The use of others Alcohols is also possible.

in the In the context of the present invention, the term "biodiesel" may be used in particular also designate any mixture of fatty acid alkyl esters. The alkyl group of the fatty acid alkyl ester may, for example straight chain or branched and comprising 1 to 28 carbon atoms. In particular, the fatty acid alkyl ester may, for example a methyl, ethyl, propyl, butyl, pentyl or hexyl ester of a Be fatty acid. Preferably, the mixture comprises fatty acid alkyl esters a content of at least 70% by weight, preferably at least 85 wt .-%, preferably of at least 95 wt .-%, particularly preferred of at least 98% by weight of fatty acid alkyl esters, respectively based on the total weight of the organic components of the mixture.

Biodiesel mixtures may contain any amount of mono-, di- and / or triglycerides. Preferably, the biodiesel has a low content of mono-, di- and / or triglycerides. For example, the biodiesel can have a maximum content of 2% by weight, preferably of at most 0.8% by weight, of monoglycerides, a maximum content of 2% by weight, preferably not more than 0.2% by weight, of diglycerides, and / or a maximum content of 2% by weight, preferably of at most 0.2% by weight for triglycerides, determined in accordance with the standard DIN EN 14214 ,

The mixture obtained in the alcoholysis of fats and oils is worked up in the usual way. So, for example the glycerol phase are separated from the crude biodiesel or the raw biodiesel can also be washed once or several times with water. But it is also possible that obtained in the alcoholysis raw biodiesel first with the help of an adsorbent to clean.

Under a raw biodiesel is understood to mean every biodiesel, the has a higher content of impurities than a biodiesel, which with the method according to the invention was cleaned. Accordingly, under a "purified Biodiesel "understood a biodiesel that has a lower Contains impurities as the raw biodiesel. exemplary Impurities that may be contained in a crude biodiesel are mono-, di- or triglycerides, soaps or glycosides, such as Sterylglykoside.

One Raw biodiesel can therefore be a biodiesel, as it is directly after alcoholysis of fats and / or oils is obtained, for example, immediately after separation of the glycerol phase. One But raw biodiesel can also be a biodiesel, which after the Alcoholysis has already gone through purification stages, but for example still has too high glycoside content, in particular one too high content of sterylglycosides, mono-, di- or triglycerides or soaps, so it does not have a specific specification must be fulfilled and cleaned.

The Raw biodiesel is inventively with a special adsorbent added.

In the process according to the invention, an adsorbent is used which contains an aluminum oxide-containing component which has an aluminum content, calculated as Al ₂ O ₃ , of more than 40% by weight. The aluminum may be contained in the alumina-containing component in the form of alumina. But it is also possible that the alumina-containing component contains the aluminum in the form of, for example, a mixed oxide. In addition to aluminum, other metals may be included in the alumina-containing component, such as silicon. The alumina-containing component can be degraded from a natural source, so be a natural mineral. Preferably, however, synthetic compounds are used. These can be produced under controlled conditions and therefore lead to reproducible properties and results in the process according to the invention. The adsorbent is preferably predominantly of the alumina-containing component. It is possible that the adsorbent in addition to the alumina-containing component, for example, contains a binder. Preferably, the proportion of the alumina-containing component in the adsorbent is more than 60 wt .-%, preferably more than 80 wt .-%, more preferably more than 90 wt .-%. The difference to 100% could for example be formed in each case by a proportion of a binder, with which the alumina-containing component is bound to an adsorbent particle. According to a particularly preferred embodiment, the adsorbent consists only of the alumina-containing component.

According to one embodiment of the method according to the invention, the aluminum oxide-containing component comprises an aluminum content, calculated as Al ₂ O ₃ , of more than 50% by weight, according to a further embodiment, an aluminum content of more than 70% by weight. According to a further embodiment of the method according to the invention, the alumina-containing component consists of Al ₂ O ₃ .

Surprised was found that by the inventive Use of an adsorbent which contains a high proportion of aluminum oxide has, even when using small amounts of the adsorbent impurities can be efficiently removed from raw biodiesel. So allows the use of the adsorbent with a high Alumina content removal of mono-, di- and triglycerides from raw biodiesel and with appropriate reaction For example, it is possible after the alcoholysis of Triglycerides and the separation of the glycerol phase in one step in which the raw biodiesel is washed with water. The raw biodiesel can be reacted directly with the adsorbent, wherein impurities of the biodiesel from the adsorbent from the raw Biodiesel be removed. This is particularly advantageous when the raw biodiesel contains a high proportion of fatty acid soaps which is used in a water wash to form a stable emulsion can lead.

The Adsorbent can in itself in any form in the raw to be cleaned Biodiesel be introduced. For example, it is possible stir the adsorbent in ground form into the biodiesel.

Becomes the adsorbent in the form of a powder or granules in the crude biodiesel introduced and suspended in this, so in this embodiment the process of the invention, the raw biodiesel preferably moved during cleaning, for example with the help of a stirrer, so that the adsorbent intimately the biodiesel is mixed and does not settle.

The Amount of the adsorbent added to the biodiesel is from the amount of impurities contained in the raw biodiesel. If a raw biodiesel is used, as it is immediately after Alcoholysis of triglycerides is obtained, it makes sense to larger Use quantities of the adsorbent. If, however, the inventive Process for the post-purification of an already prepurified crude biodiesel used that only small amounts of impurities contains, according to the amount of added adsorbent be kept low.

The Treatment time during which the raw biodiesel with The adsorbent is in itself of the relative Quantities of raw biodiesel and adsorbent, as well as of the raw Biodiesel contained amount of impurities dependent. However, it was found that in the inventive Adsorbent used has a relatively fast kinetics. Preference is given to the contact time between crude biodiesel and adsorbent longer than 5 minutes, preferably longer than 10 and according to another embodiment chosen for more than 15 minutes. According to one Embodiment, the treatment time becomes shorter as 120 minutes, according to another embodiment shorter than 60 minutes and according to one Another embodiment shorter than 30 minutes selected.

The process according to the invention is preferably added at room temperature or particularly preferably at Temperatures above room temperature. The crude biodiesel therefore preferably has a temperature in the range of more than 15 ° C. during the treatment with the adsorbent, more than 30 ° C. according to a further embodiment and more than 40 ° C. according to a further embodiment. In most cases, it is not necessary to heat the biodiesel to a high temperature. According to one embodiment, the temperature is less than 100 ° C, according to another embodiment, less than 90 ° C and, according to one embodiment, less than 80 ° C on.

Prefers is the cleaning, in particular a fine cleaning of the biodiesel, at a temperature above room temperature. Under a fine cleaning is a post-cleaning of an already pre-cleaned Understood biodiesel, the crude biodiesel only small Contains amounts of impurities. Such a fine cleaning can be done, for example, if the raw Biodiesel already less than 2.0 wt .-%, preferably less than 1.0 wt .-% monoglycerides or less than 2 wt .-%, preferably less 1% by weight of diglycerides or less than 1% by weight, preferably less as 0.5 wt .-% triglycerides, but a given Specification not met and, for example, more than 0.2 wt .-% monoglycerides, or more than 0.8 wt .-% diglycerides or contains more than 0.02% by weight of triglycerides. After the fine cleaning met with the inventive method the purified biodiesel then the specification, d. H. it contains less than 0.2% by weight of monoglycerides, less than 0.8% by weight of diglycerides and less than 0.02 wt.% triglycerides.

Becomes the purification of the raw biodiesel at elevated temperature In particular, the solubility is carried out of contaminants present in solid form in biodiesel, according to experience better. By heating of crude biodiesel, such can be present in solid form Impurities, for example, after cooling of the biodiesel have failed, bring it back into solution. Working at elevated temperature also ensures that these solid impurities after redissolving be depleted by adsorption on the adsorbent and not only a filtration takes place. This is especially significant when for purifying the biodiesel, the adsorbent is provided in the form of a column packing. The formation of rainfall would become the pillar clog and make a regeneration of a column difficult.

To the treatment, the biodiesel is separated again from the adsorbent. For this purpose, usual methods can be used. For example, let the adsorbent sediment and the supernatant cleaned biodiesel be decanted. But it is also possible the adsorbent, for example, by filtration from the purified biodiesel separate.

The aluminum oxide-containing component used as adsorbent in the process according to the invention preferably has a very high specific surface area of more than 100 m ² / g. According to a preferred embodiment, the alumina-containing component has a specific surface area in the range from 100 to 750 m ² / g, particularly preferably from 120 to 700 m ² / g, particularly preferably from 140 to 650 m ² / g. The specific surface area is determined by the BET method.

According to a further preferred embodiment, the aluminum oxide-containing component of the adsorbent used in the process according to the invention preferably has a high pore volume. The alumina-containing component preferably has a pore volume of more than 0.3 ml / g, more preferably a pore volume of more than 0.45 ml / g, particularly preferably more than 0.50 ml / g. The pore volume is calculated as the cumulative pore volume according to BJH ( IP Barret, LG Joiner, PP Haienda, J. Am. Chem. Soc. 73, 1991, 373 ) for pores with a diameter of 1.7 to 300 nm. In one embodiment, an alumina-containing component has a pore volume of less than 1.4 ml / g. According to a further embodiment of the method, the pore volume of the alumina-containing component is less than 1.3 ml / g and in another embodiment less than 1.2 ml / g.

The high specific surface and the high pore volume allow on the one hand a high adsorption capacity for the impurities contained in the raw biodiesel as well as a fast Kinetics of adsorption, so that the process in particular suitable for industrial use.

As the alumina-containing component, preferred aluminas, aluminum hydroxides, boehmite or aluminosilicates are used. These compounds can be used in pure form or else in the form of mixtures of the compounds mentioned. As alumina, both α-, γ- and ε-Al ₂ O ₃ can be used. In a preferred embodiment, aluminum oxides are used, with γ-Al ₂ O _{3 being} more preferred. The aluminas can be used in pure form or as a mixture of two or three of said phases. It can aluminum hydroxides of different composition tion, which may also have a different degree of dehydration or polymerization. Boehmite is AlOOH.

aluminas and their hydrates can be prepared, for example, by adding basic aluminate solutions by adding acid be neutralized. The precipitation of aluminum hydroxides or their hydrates can by the addition of kristallisationskeimen get supported. It is also possible hydrated aluminum hydroxides from acidic solutions of aluminum salts by adding Bases or by combination of basic solutions of Aluminates with acidic solutions of aluminum salts precipitate. The hydrated from the aqueous phase separated Aluminum oxides can then be removed by annealing in aluminas being transformed.

A suitable method for producing hydrated aluminas, for example, in WO 01/02297 described.

The Aluminum oxides and their hydrates can also over be prepared a sol-gel process. This can, for example Aluminum alkoxides are hydrolyzed. The hydrolysis can be general performed in a temperature range of 30 to 150 ° C. become. The solid alumina hydrate is separated from the aqueous Alcohol phase separated. The resulting crystals can for example, be aged under hydrothermal conditions.

A suitable method is for example in WO 00/09445 described.

According to one Another preferred embodiment is the alumina-containing Component a synthetic aluminosilicate.

The aluminosilicates preferably have a silicon content, calculated as SiO ₂ , of less than 60% by weight, preferably less than 55% by weight, more preferably less than 50% by weight. According to one embodiment, the silicon content of the aluminosilicate, calculated as SiO ₂ , is more than 0.5% by weight, in accordance with a further embodiment more than 0.75% by weight.

Aluminosilicates can be prepared, for example, by hydrolyzing organic aluminum compounds under acidic conditions and then aged together with silicic acid or silicic acid compounds under hydrothermal conditions. Suitable aluminum compounds are, for example, aluminum alcoholates, aluminum hydroxyalcoholates, aluminum acetylacetonates, aluminum alkyl chlorides or else aluminum carboxylates. A suitable method is for example in US 6,245,310 B1 described.

In order to obtain particularly pure aluminosilicates, it is also possible to use hydrolyzable organosilicon compounds instead of silica, the hydrolysis of the organosilicon compounds and of the hydrolyzable aluminum compounds being carried out together. Such a method is for example in the EP 0 931 017 B1 described.

Particular preference is given to using aluminosilicates which contain only SiO ₂ and Al ₂ O ₃ as constituents. The proportion of other metals, calculated as the most stable oxide, is preferably chosen to be less than 1% by weight.

The Adsorbent may be provided, for example, in the form of a powder become. An adsorbent in the form of a powder is suitable, for example, when the adsorbent is stirred into the crude biodiesel, ie in the form of a suspension.

The Particle size of the powder is generally adjusted that the adsorbent without difficulty with a suitable Methods, such as filtration, within a suitable Time period from the purified biodiesel can be separated. Becomes uses a powder which is suspended in the crude biodiesel, is the dry sieve residue of the adsorbent on a sieve with a mesh width of 63 microns preferably more than 25% by weight, and is preferably in a range of 30 up to 50% by weight of the dry sieve residue on a sieve with a mesh size of 25 microns is preferably more than 80 wt .-%, and is preferably in a range of 85 to 88 wt .-% Furthermore, the dry sieve residue on a sieve with a mesh size of 45 microns preferred more than 35% by weight, more preferably more than 45% by weight.

However, in particular for an application of the adsorbent in the form of a column packing also hö here grain sizes suitable. For this purpose, the adsorbent is preferably used in the form of granules. In particular, for the production of column packings, a granulate is preferably used which has a particle size of more than 0.1 mm. Preferably, the granules have a particle size in the range of 0.2 to 5 mm, particularly preferably 0.3 to 2 mm. The grain size can be adjusted, for example, by sieving.

The Granules can be prepared by conventional methods, for example, by mixing the finely ground adsorbent with a granulating agent, For example, water, and then applied in a conventional granulating is granulated in a mechanically generated fluidized bed. It However, other methods may be used, to make the granules. So can the powdery Adsorbent formed, for example, by compaction to a granulate become.

The Adsorbent can also be provided as a shaped body, obtained for example by extrusion of a plastic mass can be. For this purpose, from the alumina-containing Component and optionally other components, such as a Binder, by adding a liquid, preferably water, made a paste. This paste is then extruded and the Extrudate crushed, for example by the extruded strand is cut into short cylindrical pieces, and then drying the obtained shaped bodies. In addition to massive Cylinders can in this way z. B. also hollow cylinder getting produced.

To The shaping can be the granules or the shaped bodies are still heat treated and, for example, by heating be sintered. This can increase the stability of the granules or the molding can be increased. For the heat treatment, the moldings or the granules preferably at a temperature of more than 300 ° C, according to a further embodiment to a temperature of more than 400 ° C, and according to still a further embodiment to a temperature of heated more than 500 ° C. According to one embodiment the temperature is lower than 1200 ° C, according to a further temperature less than 1000 ° C chosen.

Around To obtain stable shaped bodies, is the heat treatment preferably for a period of at least 30 minutes, according to a another embodiment for a period of at least 60 minutes. According to one embodiment the duration of treatment is chosen to be less than 5 hours.

As already explained, the adsorbent can go straight to raw Biodiesel be given, the biodiesel preferably stirred becomes. The amount of the adsorbent is preferably in a range of 0.05 to 5 wt .-% particularly preferably 0.1 to 2 wt .-% selected. The percentages of adsorbent are by weight of raw biodiesel.

According to one In another embodiment, the adsorbent is in the form of a Column packing provided. The raw biodiesel can then be passed through the column packing. The column packing can be provided for example in the form of a cartridge. In practical implementation, the raw biodiesel then pass through the cartridge until the adsorption capacity of the adsorbent contained in the cartridge is exhausted. The cartridge can then easily replaced with a new cartridge become. The cartridge can then be discarded, or, as far as the separated contaminants fed to another use to be or the cartridge is to be used again the compounds bound on the adsorbent also with a suitable Eluents are eluted.

Becomes the adsorbent is provided in the form of a column packing the adsorbent in the form of larger grains provided an excessive Prevent pressure drop across the column packing.

at In this embodiment, therefore, the adsorbent is preferred used in the form of granules, which ser a particle diameter of more than 0.1 mm, particularly preferably a particle diameter in Range of 0.2 to 5 mm.

Around To avoid clogging the column becomes the raw biodiesel preferably heated to a temperature above room temperature, before it is put on the column.

The use of the adsorbent in the form of a column also allows regeneration of the column, for. As with solvents, whereby the column packing can be used several times. Suitable regenerants are, for example, alcohols, mixtures of alcohols and alkanes or chlorinated hydrocarbon substances or aqueous surfactant-containing solutions. Optionally, the regeneration may also be carried out in a gradient wherein the biodiesel is first washed with a relatively nonpolar solvent from the column and then transferred to a more polar solvent, for example an alcohol such as methanol or ethanol, around the impurities bound to the adsorbent , in particular sterylglycosides, to elute from the column.

The adsorbents used in the process according to the invention preferably react neutral to slightly alkaline. A suspension of 10% by weight of the adsorbent in water preferably has a pH in the range from 5 to 9, more preferably 6 to 8.5, and most preferably in the range from 6.5 to 8. The pH is determined by means of a pH electrode according to DIN ISO 7879 certainly.

A further increase the activity of the adsorbent leaves reach according to an embodiment, when the adsorbent is pre-dried. According to one Embodiment of the invention, the adsorbent a Water content of less than 5 wt .-%, according to a Another embodiment, a water content of less as 3 wt .-% and according to another embodiment a water content of less than 2 wt .-% on.

It may also be advantageous, the adsorbent to a higher To heat temperature to remove physically bound water. For this purpose, according to one embodiment the adsorbent heated to a temperature of more than 600 ° C. become. According to one embodiment the temperature is chosen lower than 1000 ° C. By Such a treatment can be used, for example, in boehmite first the superficially bound water will be removed and the hydrate are converted into an oxide phase.

The inventive method is also particularly suitable for the removal of glycosides from biodiesel. As already explained, the method is particularly suitable for the post-purification of pre-cleaned biodiesel. With the Processes according to the invention can be glycosides remove it from the biodiesel if these are in very small quantities contained in biodiesel. In this embodiment becomes a very pure Biodiesel after cleaning subjected. According to a preferred embodiment Therefore, the crude biodiesel has a glycoside content of less as 5,000 ppmw, more preferably less than 2,000 ppmw, in particular preferably less than 500 ppmw. The invention Method is very suitable especially for the removal small amounts of glycosides, especially Sterylglykosiden. According to one preferred embodiment, therefore, the crude biodiesel a glycoside content of less than 100 ppmw, more preferred less than 80 ppmw, more preferably less than 50 ppmw. According to one embodiment, the raw biodiesel has a glycoside content greater than 10 ppmw, according to a further embodiment of more than 20 ppmw.

Under Glycosides are commonly compounds of carbohydrates and Aglykone understood. As carbohydrates, both mono- as well as oligosaccharides may be contained in the glycosides. As Aglykone can In itself, all compounds act to form a glycosidic Binding can react with the carbohydrate. The aglycone can bind both α- and β-glycosidic be. As carbohydrates can be both aldoses and Ketoses may be present as both 5 and 6 rings, so as furanosides or pyranosides.

Especially the method according to the invention is suitable for Separation of sterol glycosides from crude biodiesel. Sterylglykoside are glycosides which include sterols as aglycone. Sterols are nitrogen-free, polycyclic, hydroaromatic compounds, in particular Derivatives of guanan or perhydro-1H-cyclopenta [α] phenanthrene. Examples of sterol glycosides are stiosteryl, stigmasterol or campesterol-β-glycoside. Preferably, the Sterylglykoside in the form of a glycoside.

The Glycosides, in particular steryl glycosides, are preferably not in acylated form. By the polar hydroxy groups of the saccharide have the glycosides, especially Sterylglykoside, a very bad Solubility in biodiesel. They therefore form very easily a poorly soluble precipitate in biodiesel. As already explained, the invention is suitable Method especially for the purification of biodiesel, which still low levels of contamination by glycosides, in particular Sterylglykoside, has. These are a very fine precipitate in front.

According to one embodiment of the method, the crude biodiesel therefore comprises the at least one glycoside, in particular steryl glycoside, in the form of a finely divided precipitate, wherein the mean particle size of the precipitate (D ₅₀ ) according to an embodiment is less than 200 μm, preferably less than 100 μm. Preferably, the particle size of the precipitate is in the range of 10 to 100 microns, especially before given in the range of 10 to 20 microns. The mean particle size is determined at room temperature (20 ° C), for example by laser diffraction.

The Glycoside, especially Sterylglykosid, falls in the form of Crystal agglomerates, the agglomerates when viewed Under the microscope, an amorphous structure of gel-like loose together connected crystallites show. These agglomerates usually exist not of pure glycoside, especially steryl glycoside, but still contain fatty acid ester, which adsorbs on the precipitate are.

The Adsorbents of the invention are also for administration of glycosides of animal origin that are still in biodiesel are included. Contaminants by glycosides of animal origin occur in biodiesel when used as a raw material animal fats become. These animal fats contain cholesterylglycerides, which in biodiesel can cause similar problems as described for the sterylglycosides of plant origin.

The Adsorbent used in the process according to the invention has a high adsorption capacity, especially for Mono-, di- and triglycerides, as well as fatty acid soaps and Glycosides. If the process for a post-cleaning a Biodiesels uses only small amounts of impurities contains, it is sufficient if only small amount of Adsorbent be given to the raw biodiesel. The adsorbent leaves after treatment quite simple, for example by filtration, remove again from the cleaned biodiesel. According to one Embodiment, the adsorbent in a proportion of less than 5% by weight, based on the crude biodiesel. According to another embodiment For example, the adsorbent is present in a proportion of less than 3% by weight according to a another embodiment in a proportion of less than 2 wt .-% added. In order to achieve a sufficient cleaning effect, The adsorbent according to one embodiment in a proportion of more than 0.2 wt .-% according to a another embodiment in a proportion of more than 0.5 Wt .-% added to the raw biodiesel.

As already explained above, contains the crude biodiesel after alcoholysis still relatively large amounts of impurities, when the transesterification is carried out using ethanol becomes. Because of the high binding capacity of the inventive This method is therefore particularly suitable for the adsorbent used for a biodiesel consisting essentially of fatty acid ethyl esters is constructed.

The The invention will be further described by way of example and with reference to the accompanying drawings. Showing:

1 Figure 3 is a graphic representation of the monoglyceride content of a biodiesel purified with various adsorbents; and

2 : A graphic representation of the monoglyceride content of a biodiesel, which was purified with different pre-dried adsorbents.

The Physical properties of the adsorbent were with the following Method determines:

BET surface area / pore volume after BJH and BET:

The Surface and pore volume were combined with a fully automatic Nitrogen porosimeter Micromeritics type ASAP 2010 determined.

The Sample is heated to the temperature of liquid under high vacuum Nitrogen cooled. Subsequently, it becomes continuous Stick dosed substance in the sample chambers. By capturing the adsorbed amount of gas as a function of pressure becomes more constant Temperature determined an adsorption isotherm. In a pressure equalization the analysis gas is gradually removed and a desorption isotherm added.

To determine the specific surface area and the porosity according to the BET theory, the data according to DIN 66131 evaluated.

The pore volume is also determined from the measurement data using the BJH method ( IP Barret, LG Joiner, PP Haienda, J. Am. Chem. Soc. 73, 1991, 373 ). This procedure also takes into account effects of capillary condensation. Pore volumes of certain volume size ranges are determined by summing up incremental pore volumes obtained from the evaluation of the BJH adsorption isotherm. The total pore volume according to BJH method refers to pores with egg diameter of 1.7 to 300 nm.

Water content:

The water content of the products at 105 ° C is determined using the method DIN / ISO 787/2 determined.

Loss on ignition:

In a annealed weighed porcelain crucible with lid will Approximately 1 g of dried sample weighed to the nearest 0.1 mg and for 2 h annealed at 1000 ° C in a muffle furnace. After that will the crucible in the desiccator cooled and balanced.

Determination of dry residue

Approximately 50 g of the examined air-dry clay material on weighing a sieve of the appropriate mesh size. The sieve is connected to a vacuum cleaner, which has an under the sieve bottom circular suction slot all shares, the finer than the strainer are sucked out through the strainer. The sieve comes with a Covered plastic lid and turned on the vacuum cleaner. To 5 minutes, the vacuum cleaner is turned off and the amount of up the coarser portions remaining by sieving by differential weighing determined.

Determination of bulk density

One at the 1000 ml mark truncated graduated cylinder is weighed. Then the sample to be examined is determined by means of a powder funnel so filled in the measuring cylinder in a train that above the completion of the measuring cylinder a cone of material formed. The pour cone is made with the help of a ruler, that passed over the opening of the measuring cylinder is stripped off and the filled measuring cylinder again weighed. The difference corresponds to the bulk density.

Determination of glycerol and Glycerides in biodiesel

The determination of the content of glycerol and glycerides in biodiesel was after DIN EN 14105 carried out.

Determination of Sterylglycosides with GC-MS:

For The determination of the steryl glycosides was carried out by the company ASG Analytik-Service Gesellschaft mbH, Trentiner Ring 30, 86356 Neusäß developed GC-MS method used. The procedure was as follows:

1. Enrichment of Sterylglucoside

to Enrichment of the steryl glycosides was according to the IP 387/97 Filter Blocking Tendency (FBT test) a defined amount of to examining raw biodiesel through a 1.6 μm glass fiber filter filtered. For a complete test will be about 300 mL biodiesel needed.

Of the Filter was then first with 4 mL of hexane extracted and then the Sterylglycoside with 1 ml of pyridine from the Filter washed. Sample 100 μL of MSTFA (N-methyl-N- (trimethylsilyl) trifluoroacetamide) as silylation reagent and 50 μL tricaprin solution (71.3 mg tricaprin to 10 mL pyridine). The mixture was Allowed to stand for 20 min at 60 ° C and then added 7 mL of hexane. The mixture is passed through a 0.45 μm syringe filter filtered. For the measurements in each case 1 μL the solution injected into the GC / MS system.

2. Calibration standards

The Quantification of the sterylglucosides was carried out by comparison with a calibration curve.

For this purpose, a stock solution of a pure Sterylglucosidmischung was prepared in pyridine, the concentration was set in the range of about 50 mg / 10 mL. There were defined volumes of stock solution measured and mixed with 100 μL MSTFA and 50 μL tricaprin solution. The mixture was allowed to stand for 20 minutes at 60 ° C and filtered after addition of 8 mL of hexane through a 0.45 micron syringe filter. For the measurements, 1 μL each of the solution was injected into the GC / MS system. From the intensities of the MS signals, a calibration curve was created as a function of the injected sample quantity.

3. Measurement on GC / MS

3.1 Conditions GC Guard column: Zebron Guard Column; 10 m; 0.32 mm ID Pillar: Zebron-5HT Inferno; 15 m; 0.32 mm ID; 0.25 μm Injection: on column Carrier gas: helium River: 1.5 mL / min Oven: 60 ° C for 1 min, at 15 ° C / min to 375 ° C, hold for 3 min temperature 3.2 Conditions MS Segment 1: 0-2 min hexane, cut off Segment 2: 2-25 min EI (auto), 40-650 m / z Scan Time: 0.50 scans / sec Multiplier Offset: 0V Emission Current: 40 μA Count Threshold: 1 counts Target TIC: 10000 counts Prescan Ionization Time: 100 μsec Max. Ionization Time: 5000 μsec Background Mass: 50 m / z RF Dump Value: 650 m / z

4. Evaluation

The The amount of sterylglucosides contained in the samples was determined by comparison the intensity of the MS signals with the calibration curve determined.

Adsorbents used:

For the purification of crude biodiesel, various commercially available aluminosilicates were used. These are available under the designations ^® Siral 5, Siral 30 ^{®, ®} Siral 40th Furthermore, a boehmite was tested, which is sold under the name Pural ^® SCC 150. As a further adsorbent aluminas were used, which are offered under the name Puralox ^® . These adsorbents were purchased from Sasol Germany GmbH, Ankelmannsplatz 1, 20537 Hamburg, DE. As a comparison, a commercially available calcium bentonite was (calcigel ^®, Süd-Chemie AG, Munich, DE), as well as a commercially available synthetic magnesium silicate (Magnesol ^®, The Dallas Corp., Dallas, USA).

For the investigated adsorbents, the following designations are chosen below: Adsorbent 1: Siral ^® 5 Adsorbent 2: Siral ^® 30 Adsorbent 3: Siral ^® 40 Adsorbent 4: Puralox® ^® KR-160 Adsorbent 5: Pural ^® SCC 150 Adsorbent 6: Puralox® ^® SCCa-150/230

The properties of the adsorbents are summarized in Table 1

Example 1: Removal of Steryl Glycosides from soyabiodiesel

For the research was a biodiesel made from soybean oil (Methyl ester) used. The raw biodiesel had a content non-acylated steryl glycosides of 49 ppm.

To About 500 to 800 g each of the crude biodiesel was stirred 1 wt .-% adsorbent added. The sample was for Stirred for 20 minutes at room temperature and then the adsorbent separated by filtration through a paper filter. The filtrate was directly for the quantification of sterylglycosides used.

The content of steryl glycosides determined after purification is summarized in Table 2 for the experiments carried out. Table 2: Steryl glycoside content in biodiesel (soybean oil) after purification with various adsorbents (1% by weight, based on the biodiesel) Steryl glycoside content (ppm) raw biodiesel, measurement 1 48 raw biodiesel measurement 2 51 Calcium bentonite (calcigel ^®) 42 Magnesium silicate (Magnesol ^®) <10 Adsorbent 1 <10 Adsorbent 3 <10 Adsorbent 4 <10 Adsorbent 5 <11 Adsorbent 6 <10

With the adsorbents 1-6 used according to the invention, the steryl glycoside content could be lowered below the detection limit. With boehmite a significant depletion of the crude biodiesel of steryl glycosides succeeds. Thus, the method according to the invention shows the same performance as the magnesium silicate used already in the art as an adsorbent (Magnesol ^®). By contrast, the calcium bentonite used as a comparison shows only a low performance.

To further characterize the effectiveness of the adsorbents for the removal of steryl glycosides, their concentration was gradually lowered. As a comparison, a sample of the crude biodiesel was cleaned with Magnesol ^®. The adsorbent was added in an amount of 0.5% by weight, 0.2% by weight and 0.04% by weight, respectively. The purification was carried out as described above. The results are summarized in Table 3. Table 3: Steryl glycoside content in biodiesel (soybean oil) after purification with various adsorbents at various concentrations adsorbent 0.5% by weight 0.2% by weight 0.04% by weight Magnesol ^® <5 <5 46 3 <5 <5 26 4 <5 8th nd 5 10 24 nd 6 14 25 nd

With an amount of 0.5 wt .-% adsorbent is achieved with all adsorbents a significant reduction in Sterylglycosidkonzentration. If the added amount is reduced to 0.04 wt .-%, with the adsorbent 3 is still a significant reduction in Sterylglycosidkonzentration achieved, while Magnesol ^® no significant reduction is observed.

Example 2: Removal of monoglycerides from ethyl biodiesel

For the investigation, a soybean oil-derived ethylbiodiesel was used, which had a monoglyceride content of 1.92 wt .-%, determined by DIN EN 14105 , This was treated because of the high monoglyceride content with 7 wt .-% adsorbent. For comparison, the purification was also under Ver application of magnesium silicate (Magnesol ^®) and calcium bentonite performed.

100 ml of biodiesel were heated to 55 ° C, each added with 7 wt .-% of the adsorbent and stirred for 45 minutes at this temperature with a magnetic stirrer. The sample was then filtered through a syringe prefilter. The content of monoglycerides in the filtrate was after DIN EN 14105 certainly.

In a first series of experiments, the adsorbents were used without predrying. The results are in Table 3 as well 1 played. Table 3: Content of monoglycerides in ethylbiodiesel samples after treatment with 7% by weight of adsorbent sample name Content of monoglycerides after DIN EN 14105 in % Biodiesel, untreated 1.92 Magnesol ^® 1.34 calcium bentonite 1.60 Adsorbent 1 0.95 Adsorbent 2 1.05 Adsorbent 3 1.03 Adsorbent 4 1.11 Adsorbent 5 1.58 Adsorbent 6 0.99

When using alumina adsorbents a significant reduction in monoglyceride content is achieved. This exceeds the performance of Magnesol ^® and Calciumbentonite.

Example 3: Removal of monoglycerides from ethylbiodiesel with pre-dried adsorbents

Example 2 was repeated, but the adsorbents were previously dried for 45 minutes at 55 ° C in a drying oven. The water content after drying was less than 2% by weight for all adsorbents. Subsequently, the ethyl-biodiesel sample was treated with the dried adsorbents in the manner described above. The content of monoglycerides determined in the filtrate is summarized in Table 4 and described in 2 graphically rendered. Table 4: Content of monoglycerides in ethylbiodiesel after treatment with 7% by weight pre-dried adsorbent sample name Monogylcerides in wt .-% after DIN EN 14105 Biodiesel, untreated 1.92 Magnesol ^® 1.20 Adsorbent 1 0.82 Adsorbent 2 0.76 Adsorbent 3 0.78 Adsorbent 4 1.07 Adsorbent 5 1.31 Adsorbent 6 1.05

By predrying the adsorbents, a further improvement of the adsorption performance can be achieved. The SiO ₂ -containing aluminum oxides from Siraltyp (adsorbent 1, 2 and 3) show the highest efficiency thereby. If the bound amount of monoglyceride is converted into a binding capacity, the result is 16.7% by weight of monoglyceride for adsorbent 3. The adsorbents can thus be used very well for removing monoglycerides from biodiesel.

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

• WO 2007/076163 A [0014]
• WO 2008/055676 A [0015]
• US 2005/0188607 A1 [0016]
• WO 2007/143803 A1 [0017]
• WO 2005/037969 A2 [0018]
• WO 01/02297 [0050]
• WO 00/09445 [0052]
• - US 6245310 B1 [0055]
• - EP 0931017 B1 [0056]

Cited non-patent literature

• - Monograph by M. Mittelbach, C. Remschmidt, "Biodiesel; The Comprehensive Handbook ", Graz, 2004; ISBN 3-200-00249-2 [0004]
• - DIN EN 14214 [0006]
• - DIN EN 14214 [0029]
• - IP Barret, LG Joiner, PP Haienda, J. Am. Chem. Soc. 73, 1991, 373 [0046]
• - DIN ISO 7879 [0071]
• - DIN 66131 [0089]
• - IP Barret, LG Joiner, PP Haienda, J. Am. Chem. Soc. 73, 1991, 373 [0090]
• - DIN / ISO-787/2 [0091]
• - DIN EN 14105 [0095]
• - DIN EN 14105 [0112]
• - DIN EN 14105 [0113]
• - DIN EN 14105 [0114]
• - DIN EN 14105 [0116]

Claims (18)

A process for purifying biodiesel, wherein - a crude biodiesel is provided; - The crude biodiesel is reacted with an adsorbent containing at least one alumina-containing component having an aluminum content, calculated as Al ₂ O ₃ , of more than 40 wt .-%; and - a purified biodiesel is separated from the adsorbent. A method according to claim 1, characterized in that the synthetic alumina-containing component has a specific surface area of more than 100 m ² / g. Method according to claim 1 or 2, characterized that the synthetic alumina-containing component has a pore volume of more than 0.3 ml / g, determined as the cumulative pore volume BJH for pores with a diameter of 1.7 to 300 nm. Method according to one of the preceding claims, characterized in that the alumina-containing component a synthetic aluminosilicate. The method of claim 4, wherein the aluminosilicate has a silicon content, calculated as SiO ₂ , of less than 60% by weight. A method according to claim 4 or 5, wherein the aluminosilicate is composed essentially of Si and Al oxides and the part to other metals, calculated as the most stable oxide, less than 1 Wt .-% is. Method according to one of claims 1 to 3, characterized in that the alumina-containing component an alumina is. Method according to claim 7, characterized in that the alumina is selected from γ-, δ-, θ- and α-alumina. Method according to one of claims 1 to 3, characterized in that the alumina-containing component a boehmite is. Method according to one of the preceding claims, characterized in that the crude biodiesel comprises at least one glycoside in a proportion of more than 10 ppm. Method according to claim 10, characterized in that that the at least one glycoside is a steryl glycoside or a cholesteryl glycoside is. Method according to one of claims 10 or 11, characterized in that the glycoside forms a fine precipitate in the crude biodiesel, which has a mean particle size D ₅₀ of less than 200 microns. Method according to one of the preceding claims, characterized in that the conversion of the crude biodiesel with the adsorbent at a temperature of more than 50 ° C. is carried out. Method according to one of the preceding claims, wherein the adsorbent, based on the crude biodiesel, in a proportion of less than 5 wt .-% is added. Method according to one of the preceding claims, characterized in that the biodiesel consists essentially of fatty acid ethyl esters is constructed. Method according to one of the preceding claims, characterized in that the adsorbent has a water content of less than 5 wt .-% has. Method according to one of the preceding claims, characterized in that the adsorbent in the form of a column packing provided. A method according to claim 17, characterized in that the column packing regenerates several times and used several times.