MXPA06010330A - Method for reducing the dioxin content of bleaching earth - Google Patents

Abstract

The invention relates to a method for reducing the dioxin content of a composition comprising crude clay that contains at least one dioxin or a bleaching earththat contains dioxin. Said method is characterised in that the composition is heated to a temperature ranging between 125 and 650°C.

Description

METHOD TO REDUCE THE DIOXINE CONTENT IN CLAY-BLEACHER DESCRIPTION OF THE INVENTION Bleaching clays have been used for many decades for the purification of oils and fats. In the production of bleaching clays, two methods are mainly used, namely the activation with acid of non-naturally activated ectites, in particular of crude clays containing montmorillonite, in a sludge process using large amounts of acid, as well as the use of activated clays. naturally, they are eventually activated even with small amounts of acid in a process that does not generate wastewater. The disadvantage of the first method is that it is associated with large amounts of wastewater. However, very active bleaching clays are obtained. The decolorizing power of the products produced according to the second method is generally somewhat inferior, but the simple production method allows an economical and non-polluting production. Regardless of its production method, bleaching clays are mainly used to process and purify edible oils and fats. Because products manufactured with the help of bleaching clays are integrated into the food chain, it is necessary that they be produced with the minimum amount of contaminants. As bleaching clays find frequent use in the animal feed industry, it is also true for bleaching clays, which in themselves do not introduce substances harmful to edible oils, which must also achieve a minimum exposure with harmful substances. One of the most feared contamination in food is dioxins and dibenzofurans. According to a recommendation of the FEDIOL (Federation of 1 'Industrie de l'Huilerie de l'EU, respectively EU Seed Crushers and Oils Processors' Federation, or Federation of the EU of crushers of seeds and processors of oils, by his abbreviations in French ), bleaching clays must have a dioxin / dibenzofuran content of less than 1 ng / kg I-TEQ (toxicity equivalents). The contamination of the environment with dioxins is a ubiquitous problem. Larger amounts of dioxin are derived from anthropogenic sources, but dioxins are partly also found in deeper layers containing clay that clearly can not be associated with any human activity. According to more recent research, dioxins were produced during the sedimentation of these strata by biocatalytic synthesis from 2, 4, β-trichlorophenol, which in turn may have been generated by the activity of exogenous bacterial chlorine peroxidases. starting from phenol present in organic matters. This thesis is supported by the fact that anthropogenic dioxins are found in the subsoil almost exclusively in the upper strata due to the low mobility of dioxins. The distribution of the congeners (isomers with different position of the chlorine atoms) of the dioxins contained in deeper layers also has an unusual regularity. Also, the absence of dibenzofurans, which usually accompany anthropogenic dioxins, indicates an unusual genealogy. Regardless of the use of bleaching clays and the source of dioxins, there was an objective to produce clay and bleaching clay products with few dioxins respectively, which are largely free of dioxins. The aim was in particular to produce bleaching clays of the so-called naturally active raw clays respectively of bleach clays laden with dioxins. It was also an object of the invention that the elimination step of dioxin does not have to be accepted as a source of disadvantages in terms of the purification power respectively the activity of discoloration in the products obtained. This object is achieved by the method according to claim 1. Preferred embodiments are indicated in the dependent claims. Object of the invention is, therefore, a method for reducing the content of dioxins of a composition containing at least one crude clay containing dioxin or a bleaching clay containing dioxin, characterized in that the composition is heated to a temperature in the area of about 125 to 650 ° C. Preferably, the composition consists of at least 50%, in particular at least 75%, particularly preferably at least 90% crude clay and / or bleaching clay. According to a particularly preferred embodiment, the composition consists essentially or totally of raw clay and / or bleaching clay. Raw clay is understood to mean, in the context of the present invention, a naturally active or non-naturally active clay material, and also clay materials activated by mechanical or chemical processing steps, but which - as a delimitation with respect to bleaching clays. - they have not been activated in an activation stage (separate). Correspondingly, bleaching clay is understood in the sense of the present invention as an activated clay material (in an activation stage), in particular by thermal and / or acid treatment. The term bleaching clay is familiar to the expert and comprises activated clay materials which can be used, thanks to their adsorption activity respectively fading, to purify edible oils and fats in particular. Inventively all the naturally active or naturally non-active clays that are familiar to the skilled person can be used, as well as fresh or used bleaching clays (ie, activated raw clays), in particular di and tri-octahedral layered silicates of the serpentine group, kaolin and talc-prophyllite, smectites, vermiculites, illites and chlorites, as well as the sepiolite-palygorskite group such as, for example, montmorionite, neutronite, saponite and vermiculite or hectorite, beidellite, palygorskite and mixed layer minerals (mixed layer minerals ). Of course, it is also possible to use mixtures of two or more of the preceding minerals. The inventively used composition, comprising at least one dioxin-containing raw clay and / or a dioxin-containing bleaching clay, may likewise contain other components which are not detrimental to the intended use of the composition, in particular its activity as bleaching clay or They may even have usable characteristics. According to an inventively preferred embodiment, the composition used is a bleaching clay containing dioxin or a clay-containing raw clay, wherein it can be produced - with the help of the inventive method - a bleach or a raw clay with low dioxin content or widely free from dioxin By "dioxins" are meant the chlorinated dibenzodioxins, but also the analogous dibenzofurans. In the following, the term "dioxin (s)" is used as representing this class of substances. By reducing the dioxin concentration, any decrease in the dioxin content of the composition is comprehensively understood after carrying out the inventive method in comparison with the raw material. The dioxin content of the composition is reduced for this preferably from more 1 ng I-TEQ / kg to less than 1 ng / kg I-TEQ, in particular to less than about 0.7 ng I-TEQ / kg. It is common knowledge that high temperatures destroy the reticulated structures of an active bleaching clay, which decreases the discoloration activity. In a global sense, raw clays and bleaching clays used inventively are. materials whose utility may be reduced, for example, as a result of unfavorable changes in the cross-linked structure due to high temperatures. It was now possible to show surprisingly that it is possible to decompose the dioxins contained in the raw material used (raw clay or bleaching clay) at temperatures between approximately 125 and 650 ° C, in particular between approximately 300 and 600 ° C, and particularly preferably from approximately 410 to 600 ° C, in particular without detracting from the usefulness of the raw clay respectively whitening clay. The dioxin contents could be reduced in particular in the upper temperature areas, partly up to the test limit. Particularly good results were obtained at temperatures between about 450 and 550 ° C (600 ° C). Furthermore, it has surprisingly been found that the heating step can be carried out in a single step and without the use of an inert gas atmosphere (eg nitrogen or steam, or the like) and that particularly good results are obtained by this simple method According to a particularly preferred inventive method, the heating step is carried out in an atmosphere containing oxygen, in particular in an air atmosphere. According to a particularly preferred embodiment, rehydration is carried out after heating to establish a moisture content of about 3.0 to 14% by weight, in particular of about 5.0 to 11% by weight, with particular preference of about 7.0 to 10% by weight, possibly in association with an activation by acid, thanks to which, surprisingly, the presentation of losses in the whitening activity of the product is avoided. On the contrary, it was unexpectedly detected that, by acid activation of the raw clay respectively also of the bleaching clay, bleaching clays are obtained both with low dioxin content and also particularly active after heating. It was further discovered that in many cases it is preferable to carry out the activation by acid directly after the heating, that is, before a possibly rehydration. The acid treatment can be carried out with at least one organic or inorganic acid in dissolved form or as a solid substance. To the extent that a composition with a naturally active raw clay or a bleaching clay is employed, the acid treatment is preferably carried out with 1 to 10% by weight of acid. To the extent that a composition with a crude clay not activated is used, in some cases preferably 20 to 70% by weight of acid, in particular of an inorganic acid, is used. An acid treatment (an activation by acid) carried out after the heating step makes it possible to obtain bleaching activities respectively adsorption or discoloration activities until clearly improved. In general, the inventive activation of raw clays can be carried out by an acid treatment. For this, the raw clays are contacted with an inorganic or organic acid. In principle it is possible to use any method familiar to the skilled artisan for acid activation of clays, including the methods described in WO 99/02256, US-5,008,226 and US-5, 869, 415, same as in . this measure is expressly incorporated in the description by reference. According to a preferred inventive method, it is not necessary to remove excess acid and salts generated during activation. Rather, after applying the acid, as is customary in activation by acid, a washing step is not carried out, but the treated raw clay is dried and then crushed to the desired grain size. During grinding a typical degree of grain fineness is generally adjusted. The dry sieving residue is left for this in a sieve with a mesh size of 63 μm in the area of 20 to 40% by weight. The remainder of dry sieving in a sieve with mesh size of 25 μm is located in the area of 50 to 65% by weight. In an optional embodiment of the inventive method, the activation of the raw clay is carried out in the aqueous phase. For this, the make is put in contact with the raw clay in aqueous solution. This can be done in such a way that raw clay is first separated by gravity, preferably prepared in powder form. The acid is then added (for example in concentrated form). But it is also possible to separate the raw clay by gravity directly in an aqueous solution of the acid, or to apply the aqueous solution of the acid in the raw clay. According to an advantageous embodiment, the aqueous acid solution can be sprayed, for example, in a clay (crude) preferably ground or in the form of powder, the amount of water being preferably selected as small as possible and used, for example, a concentrated acid or an acid solution. The amount of the acid can be selected in many cases preferably between 1 and 10% by volume, particularly preferably between 2 and 6% by volume, of a strong acid, in particular a mineral acid such as sulfuric acid, in relation to free raw clay. water (atro). However, larger amounts of acid can also be used and offer an advantage in some cases. To the extent necessary, the excess water can be removed by evaporation and the activated raw clay then ground to the desired fineness. Preferably it is subjected to drying to obtain the desired moisture content. The water content of the bleached clay product obtained is in most cases adjusted to a proportion of less than 20% by weight, preferably less than 10% by weight. For the activation described above by means of an aqueous solution of an acid respectively a concentrated acid, the acid can be selected at will. Both mineral acids and also organic acids or mixtures of the previous acids can be used. Usual mineral acids such as hydrochloric acid, phosphoric acid or sulfuric acid can be used, with sulfuric acid being preferred. Acids which are concentrated or diluted respectively acid solutions can be used. As organic acids, for example, citric or oxalic acid can be used. Citric acid is preferred. Preferably, but not necessarily, the raw clay is not calcined before the acid treatment. The grain size or respectively the average grain size of the inventive adsorption medium should preferably be selected such that a complete and simple separation of the clay from the refined product is permitted in the subsequent use of the activated clay respectively of the bleaching clay. According to an inventive embodiment, the average grain size of the raw clay in powder form is selected in the area of 10 to 63 μm. The fineness is typically selected such that in a sieve with a mesh size of 63 μm approximately 20 to 40% by weight of the mixture remain (sieve residue) and in a sieve with a mesh size of 25 μm remain approximately 50 to 65% by weight of the mixture. The above can be designated as typical bleaching clay fineness. As already explained, it is possible to produce by means of the inventive method in a simple and economic manner adsorption agents and whitening clay products whose bleached adsorption activity is surprisingly high and which is superior in some aspects to the activity of clays highly active whitening agents. The calcined after. activation by acid is not necessary, but it is not excluded. The amount of the acid used for the activation is selected such that, on the one hand, an appropriate activation occurs (particularly in terms of adsorption activity, bleaching and / or discoloration of the material, preferably for the treatment of edible oils and fats). ) of the clay (raw), but on the other an excessive load with acid is avoided. The amount to be used depends on the type of acid used, for example its acid potency. The amount of appropriate acid can be determined by the expert by simple preliminary tests. When mixing clay (raw) and acid, the presence of other components (solids) is not usually required, but it is also not excluded according to the invention. The activation by acid described above of the raw clay or the bleaching clay can also be carried out prior to the step of inventive heating. Suitable inorganic acids are, for example, hydrochloric acid, sulfuric acid and / or phosphoric acid for activation of the raw clay or bleaching earth, particularly in the case of naturally inactive raw clays. The dioxin-containing raw clay, respectively the dioxin-containing bleaching clay, preferably has specific surfaces greater than 50 m2 / g and a pore volume greater than 0.1 ml / g, determined according to the methods mentioned below. According to another aspect of the invention it has been determined that dioxins are optionally fixed with extreme force in the raw clays or dry bleaching clays, so that it is no longer possible to check their presence by the analytical methods currently in use (extraction with solvents). organic at 140 ° C and pressure of 80 bar), so it is wrongly assumed that raw clays do not contain dioxins. But if the identical material is rehydrated to a moisture content of approximately 3.0 to 14% by weight, in particular from 8 to 10% by weight, the dioxins contained therein are again analytically verifiable. By means of the simple inventive method it is possible to obtain bleaching clays with surprisingly little dioxin content which develop an excellent activity, for example, in the bleaching of oils and fats. In addition to the method described above for the production of a product of bleaching clay with low dioxin content, another object of the invention is, therefore, such product itself of bleaching clay having low dioxin content, it obtainable by the method described above. Another object of the invention is the use of this bleaching clay product having low dioxin content for the refining of oils and fats. With particular preference, the whitening clay product having low dioxin content for the refining of (vegetable) oils. The bleaching clay product having low dioxin content is particularly suitable for decolorizing and removing chlorophyll from oils and fats. The following analytical methods were used: Surface: the specific surface was determined according to the BET method with a fully automatic nitrogen porosimeter from the company. Micromeritics, type ASAP 2010, according to DIN 66131. Volume of pores: the volume of pores was determined according to the CC14 method (HA Benesi, RV Bonnar, CF Lee, Anal. Chem. 27 (1955), page 1963. To determine . pore volumes for different ranges of pore diameter a partial vapor pressures of CC14 defined by mixing CC14 with paraffin oil analysis are set: the colored numbers of oils (Lovibond method) were determined according to AOCS Ce 13b-45 The determination of chlorophyll A was carried out according to AOCS Ce 13d-55 Water content: the water content of the products was determined at 105 ° C using the method DIN / ISO-787/2 by drying for 2 hours in the oven . drying dioxin Analysis: determination of dioxins / dibenzofurans was performed by an approved laboratory evaluation was performed according to the method of WHO (Amtsblatt der Europäischen Cf. Gemeinschaften, year 45, 6 August 20. 02, L209 / 14) The analysis with respect to dioxins is carried out as follows: The samples are adjusted to a moisture content of 8.5% by weight. To the extent that it is not possible to adjust such a high moisture content, then the maximum possible moisture content is set in the heated chamber. A sample of approximately 30 to 50 g is then extracted, after adding the internal standard mixtureiFI , by means of ASE (Accelerated Soxhlet Extraction, for its acronym in English) with toluene, as a solvent at 140 ° C and 80 bars during a treatment period of 25 min. The extract is purd on a column of mixed silica gel (22% NaOH-silica, neutral silica, 44% H2SO4-silica), followed by chromatographic separation on aluminum oxide. After adding the reunion standard mentioned below, the eluate of the aluminum oxide column is concentrated in the nitrogen stream to an appropriate final volume and then measured in relation to 17 types of dioxin (PCDD / PCDF) by chromatography of high resolution gas (injection by cold evaporation, column: DB-dioxin) and high resolution mass spectroscopy (electron impact ionization, 2 ions per degree of chlorination (native and internal standard). the isotope dilution method The following internal 13C12 standards were used: 2378-TCDD 12378-PeCDD 123678-HxCDD 1234678-HpCDD OCDD 2378-TCDF 23478-PeCDF 123678-HxCDF 123789-HxCDF 1234678-HpCDF OCDF The following standard was used of reunion: 37C14-2378-TCDD 13C12-1234789-HpCDF In the following examples and comparative examples given for illustrative purposes only, the following grades of clay were used: Clay 1: Mixture of natural clays of attapulgite and montmorillonite from the Georgia region / EE. US: Pore volume: 0.24 ml / g Specific surface area: 154 m2 / g dioxin content: 6.6 'ng I TEQ / kg Clay 2: Mexican hormite: pore volume: 0.26 ml / g surface area 176 m2 / g dioxin content: 5.4 ng I-TEQ / kg Clay 3: montmorillonite activated with HCl (bleaching clay): pore volume: 0.35 ml / g specific surface area: 244 m2 / h dioxin content: 9.4 ng I-TEQ / kg Clay 4: Turkish montmorillonite: pore volume: 0.15 ml / g specific surface area: 115 m2 / g dioxin content: 6.5 ng I-TEQ / kg. Comparative Examples Production of a bleaching clay from clay 1 Raw, wet mine clay 1 was pre-dried to adjust a moisture content of 15 -10% by weight, ground in a mill, rotary percussion and then a final moisture content of 8% by weight was adjusted. 100 g of the powder obtained were intimately mixed in a glass cup with 309 g of water and 2.88 g of H2SO4 (96%). The obtained mixture was dried at 110 ° C at a water content of 9% by weight and then crushed to a typical bleaching clay fineness (dry sieve residue (TSR)> 63μ = 29%). The dioxin content of the bleaching clay thus obtained was determined in 6.4 ng I-TEQ / kg. Example 1 Elimination of dioxin from attapulgite / montirtorilonite (clay 1) The wet clay from the mine was pre-dried to contain 15-20% by weight of water and then crushed by a rotary percussion mill. The powder generated in this way was distributed in equal parts which were treated in each case for one hour at temperatures of 150, 300, 400, 450, 500 and 600 ° C. The materials that were free of water after the heat treatment were rehydrated in a heated oven at 30 ° C and 80% atmospheric humidity to have water contents of 8 to 9%. The sample that had been heated to 600 ° C achieved a water content of only 7.7% by weight in the rehydration.

The following table indicates the measured dioxin contents of the samples treated according to the WHO method. Table I Elimination of clay dioxide 1 Table I shows that from a temperature of 200 ° C there is a small reduction of dioxins and from a temperature of 300 ° C a clear reduction of dioxins, being that at 450 ° C the limit value discussed by the FEDIOL of 1 ng I-TEQ / kg.

It must, however, be noted here once again that these values become measurable only after rehydration (right column of Table I). In the dry matter (calcined), not rehydrated (left column), on the contrary, clearly excessively low values are always found, in an analytical sense. EXAMPLE 2 Removal of Hormite Dioxin (Clay 2) The raw material (Mexican hormite) was processed analogously to Example 1. The data obtained associated with this are summarized in Table II. . '' Table II Elimination of dioxin from clay 2 Table 'II shows that from a temperature' of 300 ° C there is a clear reduction of dioxins and furans, being that at 400 ° C it passes below 1 ng I-TEQ / kg. EXAMPLE 3 Removal of dioxin from a bleaching clay (clay 3) The raw material, a montmorillonite activated with hydrochloric acid by mud processing, was treated and analyzed analogously to example 1 at temperatures of 125 ° C and 500 ° C. The associated data obtained are summarized in Table III.

Table III Removal of dioxin from clay 3 Example 4 Removal of dioxin from montmorillonite (clay 4) The raw material (montmorillonite) was processed analogously to example 1 at temperatures of 125 ° C and 500 ° C. The data obtained associated with this are summarized in table IV.

- '.' "• 'Table IV.' -" • "- Elimination of dioxin dß clay 4 ° Example 5 Production of a bleaching clay by activation of a mixture of attapulgite / montmorillonite with sulfuric acid The product of example 1 calcined at 500 ° C was mixed with water and then activated with 4% of H2SO4. For this, 100 g of the calcined powder were mixed with 250 g of water and 4.17 g of H2SO4 (96% intensively in a glass cup) The mixture obtained was dried at 110 ° C to have a water content of 9% by weight. weight and then crushed to whiteness of bleaching clay (dry sieve residue to sieve of 63 μm 20 to 40% by weight, dry sieve residue in sieve of 25 μm 50 to 65% by weight) Example 6 Production of a bleaching clay by activation of montmorillonite (clay 4) The product of example 4 was mixed with water and hydrochloric acid, for which 100 g of the calcined powder was transferred to 500 ° C with 300 g of water and 112.5 g HCl (32%). A round-bottom matrix was activated for 6 hours at reflux, the suspension was filtered, the filtered sediment was washed to <0.1% chlorine content, dried to 9.5% water content and then ground to a fineness of bleaching clay Application example Bleached rapeseed oil Rapeseed oil released from slime was bleached and neutralized with 0.73% by weight at 110 ° C for 30 min at a pressure of 30 mbar. The bleaching clay was then removed by filtration and the color numbers of the oil were determined with the aid of the Lovibond method in a 5"cuvette Table V reproduces the bleaching results: Table V Bleached rapeseed oil As shown in Table V clearly, with the inventive products according to Examples 5 and 6 a better discoloration (red number and chlorophyll A) is achieved than with the product according to the comparative example. In the product class of the acid-activated smectites (examples 3, 6 and Tonsil Optimum® 210 FF, a highly active bleaching clay, commercial product of Süd-Chemie AG) bleaching results can be achieved by the inventive method which, at least, they match those of the state of the art.

Claims (12)

1. Method for reducing the content of dioxin of a composition containing at least one raw clay containing dioxin or a bleaching clay containing dioxin, characterized in that the composition is heated to a temperature in the area of about 125 to 650 ° C. Method according to claim 1, characterized in that the composition is a bleaching clay containing dioxin or a crude clay containing dioxin. Method according to one of the preceding claims, characterized in that the composition is heated to a temperature in the area of about 300 to 600 ° C, in particular of more than 400 to 600 ° C. Method according to one of the preceding claims for the production of a composition with a low content of dioxin containing at least one raw clay containing dioxin or a bleaching clay containing dioxin. Method according to one of the preceding claims, characterized in that after heating to a moisture content of about 3.0 to 14% by weight, in particular of about 5.0 to 11% by weight, with particular preference "of about 7.0 to 10% by weight, it is rehydrated 6. Method according to one of the preceding claims, characterized in that the composition is subjected to an acid treatment after heating and preferably before rehydration, which is carried out optionally. previous claims, characterized in that the acid treatment is carried out with at least one inorganic or organic acid 8. Method according to one of the preceding claims, characterized in that the acid treatment is carried out, in the case of a naturally active raw clay or a bleaching clay, with 1 to 10% by weight of acid and, in the case of a raw clay not naturally active, with 20 to 70% by weight of acid, in particular of an inorganic acid. Method according to one of the preceding claims, characterized in that the dioxin-containing raw clay or the dioxin-containing bleaching clay used has a specific surface area greater than 50 m2 / g and a pore volume greater than 0.1 ml / g. Method according to one of the preceding claims, characterized in that the inorganic acid used for the acid treatment is selected from hydrochloric acid, sulfuric acid and / or phosphoric acid, and the organic acid used for the acid treatment is selected from citric acid and / or oxalic acid. Method according to one of the preceding claims, characterized in that the composition is contacted directly with the acid during the acid treatment after heating it, in particular immediately after heating. Method according to one of the preceding claims, characterized in that the composition is brought into contact in the form of a suspension (slurry) with the acid during the acid treatment after heating it, in particular immediately after heating.