DE10356894A1 - Production of adsorbent, used as bleaching earth, comprises activating raw clay with defined physicochemical properties - Google Patents

Abstract

Production of an adsorbent comprises activating a raw clay having a specific surface of more than 200 m2>/g, a pore volume of more than 0.5 ml/g and an ion exchange capacity of more than 40 meq/100 g. Independent claims are also included for the following: (1) an adsorbent produced as above; and (2) a clay product comprising a raw clay as above.

Description

The Invention relates to a method for producing an adsorbent, an obtained by the method adsorbent and its Use and a clay product.

at industrial production of oils and fats become bleaching earths to remove turbidities, discoloration or also used for the removal of oxidation accelerators. By adsorptive cleaning can Taste, color and storage stability of oils and fats significantly improved become. For purification, various classes of bleaching earths are used uses. A first group is the class of highly active, mostly on montmorillonite based bleaching earths (HPBE = high performance whitening earth). In particular, this group includes acid reactants Montmorillonite, wherein the acid activation in a complex process by dealuminating the raw clays with concentrated acids performed at high temperatures becomes. In this process, a bleaching earth product with very high specific Surface and great Obtained pore volume. Already the use of small amounts of this highly active bleaching earth leads to noticeable cleaning of the crude oils. Low amounts used in the bleaching process are therefore desirable, because the used bleaching earth binds to a residual amount of oil, whereby the yield is reduced, and secondly the used Bleaching earth, according to current regulations, must be disposed of.

adversely At these highly active bleaching earths is the fact that through the Dealuminate with acid while the production big Amounts of acidic, high-salinity wastewater incurred, which are processed or disposed of only in complex processes can be. The high cost of the disposal of the waste as well as the elaborate production process justify the comparatively high Prices of such highly active bleaching earths.

A another group is the class of nature-active clays. These naturally occurring Bleaching earths have been used for cleaning for hundreds of years of fats and oils uses. These nature-active systems (also Fuller's Earth or Fuller earths called) very inexpensive made available become. However, they have only a low bleaching power, so that she for the cleaning of hard-to-bleach oils and fats usually not are suitable. Furthermore, must in comparison to highly active bleaching earths much larger quantities of the adsorbent used to achieve the desired bleaching result. Thereby have to but higher Loss of oil or fat are accepted, since the bleaching earths are not can be separated in pure form and certain amounts of oil or fat remain in the bleaching earth.

A compromise between low production costs and acceptable activity is represented by the third bleaching earth class, the so-called surface-activated bleaching systems (SMBE = surface-modified bleaching earths). Here, a naturally active raw clay with small amounts of acid is applied and thus achieved an "in situ activation". Attapulgite and hormone-containing raw clays have proven particularly suitable for this process. These have a very high specific surface area of natural raw materials of about 100 to 180 m ² / g and a pore volume of about 0.2 to 0.35 ml / g. However, since salts formed in the acid activation or unreacted portions of the acids are not washed out, they remain on the product and are at least partially deposited in the pores. As a result, these acid-activated bleaching earths generally do not achieve the same efficiency as achieved by highly active bleaching earths (HPBE) produced by dealuminating with acid. However, the simple manufacturing method allows a comparatively low-cost production, since no acid wastewater incurred.

From US-A-5,008,226 a method for the production of acid-activated bleaching earth using a naturally occurring acid Attapulgit clay according to the above-described acid activation is known. This clay has a pore volume in the range of 0.25 to 0.50 ml / g and a specific surface area in the range of 100 to 150 m ² / g. Particular preference is given to using a naturally occurring mixture of attapulgite and bentonite. The main components of this mineral consist of 71 to 75 wt .-% SiO ₂ and from 11 to 16 wt .-% Al ₂ O ₃ . The attapulgite / bentonite mineral is acid at a temperature of about 25 to 100 ° C, corresponding to an acid amount of 1 to 10 wt .-%, applied. The acid-activated intermediate is not washed but used directly as bleaching earth after drying and milling.

US-A-3,029,783 describes a method of treating an attapulgite clay with acid ben. The attapulgite contains about 15 wt .-% Al ₂ O ₃ . The acid activated clay is suitable for use as cat litter.

US-A-5,869,415 describes a method for activating layered silicates having an ion exchange capacity of at least 25 meq / 100g by activation with 1 to 10% by weight of acid followed by calcination at temperatures of 200 ° C to 400 ° C. The layered silicates have specific surface area in the range of 132 to 167 m ² / g and a pore volume in the range of 0.27 to 0.35 ml / g and an ion exchange capacity (IUF) of 38 to 68 meq / 100g.

In WO 99/02256 discloses a process for producing a bleaching earth with an elevated acidity described. The activation takes place in an environmentally friendly, because not watery Process instead. Preference is given to 2.5 to 5 wt .-% acid in aqueous solution abandoned on pre-dried and ground raw clay. As examples for suitable acids be hydrochloric and phosphoric acid as well as citric acid described on a raw clay from the Palygorskit smectite class be applied.

In the production of acid-activated bleaching earths described above, layered silicates, in particular smectites and palygorskites or mixtures of these silicates, are therefore usually used. The raw clays used as starting materials have specific surface areas in the range of 100 to 180 m ² / g, a pore volume in the range of 0.25 to 0.50 ml / g and an ion exchange capacity in the range of 38 to 68 meq / 100 g. These layer silicates have an Al ₂ O ₃ content of> 11 wt .-%.

As already stated above, have surface-activated Bleaching earth (SMBE) has the advantage of cost-effective production. you reach however, not the bleaching effect as seen with highly active bleaching earths (HPBE) can be achieved. It is therefore in comparison to the highly active Bleaching earth larger quantities surface-activated Bleaching earth necessary to a desired To achieve bleaching result. This in turn causes that in the Bleaching by adsorption of oils and fats in the bleaching earth higher oil losses have to be tolerated and on the other hand, larger quantities must be recycled or disposed of on used bleaching earth.

Of the The invention is therefore an object of a process for the preparation an adsorbent to provide, which the Disadvantages of the prior art avoids and becoming a product with high adsorption capacity, especially regarding the bleaching effect of oils and fats leads.

These The object is achieved by a method having the features of the patent claim 1 solved. Advantageous developments of the method are the subject of dependent Dependent claims.

It has been surprising shown that when using the Rohtone defined in claim 1 through a comparatively simple activation adsorbent or bleaching earths available are whose activity is that highly active, obtained by intensive dealuminating with strong acids Bleaching earth is comparable and partly superior.

It is essential to the invention that the raw clay used has a pore volume of more than 0.5 ml / g, a specific surface area (BET area) of more than 200 m ² / g and an ion exchange capacity of more than 40 meq / 100 g. Suitable analytical methods for determining specific surface area, pore volume and ion exchange capacity are given below in the Examples.

Particular preference is given to using raw clays whose ion exchange capacity is above 50 meq / 100 g, preferably in the range from 55 to 75 meq / 100 g. Preferably, the raw clay has a specific surface area (BET) in the range from 200 to 280 m ² / g, particularly preferably in the range from 200 to 260 m ² / g. The pore volume of the crude clay used is preferably in the range of 0.7 to 1.0 ml / 100 g, in particular in the range of 0.80 to 1.0 ml / 100 g. In order to obtain an adsorbent or a bleaching earth having the desired properties, the raw clay is subjected to an activation, in particular to an acid activation.

Activation is understood to be a treatment of the raw clay as used in the manufacture of SMBE. Such methods are known per se to the person skilled in the art. They can be in a thermal treatment or in particular in a treatment with acid. Upon activation, the mineral structure of the raw clay preferably remains substantially unchanged. The specific surface and the pores Depending on the type of acid activation, the volume of crude clay may decrease by up to about 20%.

At the inventive method will be first a dried raw clay provided. Under raw clay is in the frame of the present invention is a naturally active or non-naturally active Understood clay material, whereby also by conventional, mechanical or chemical Processing steps further processed, but in demarcation to the bleaching earth, not in a (separate) activation step Activated clay materials should be recorded. Under Activation of the raw clay is to be understood as a treatment leading to a Improving the bleaching effect, especially in the bleaching of oils and fats, as shown by the color numbers in oils (Lovibond color numbers) according to AOCS Cc 13b-45 and / or the chlorophyll A determination according to AOCS Cc 13d-55 is determined.

Corresponding is included among bleaching earths for the purposes of the present invention (in an activation step) activated, in particular by thermal and / or acid treatment activated clay material understood. The term bleaching earth is the Specialist familiar and comprises activated clay materials which, due to their adsorption or bleaching activity especially for cleaning edible oils and fats can.

Especially In the present case, naturally occurring naturally occurring under raw clays are used or not nature-active clay materials that are not yet understood subjected to chemical modification, e.g. not yet strong acids occupied or dealuminated. Before activation, the Rohtones may be dried and ground.

Raw clays whose aluminum content, based on the anhydrous raw clay and calculated as Al ₂ O ₃ , is less than 11% by weight, are particularly preferably used.

Especially Preferably, raw clays are used which have only a low crystallinity, ie is not assigned to the class of layer silicates per se. The low crystallinity let yourself for example, by X-ray diffractometry determine. The most preferred raw clays are largely X-ray amorphous, you belong therefore not the class of Attapulgite or Smektite.

Of the in the process according to the invention used raw clay has a compared to conventional highly active Bleaching earth different pore distribution. At highly active Bleaching earths is the pore volume substantially of pores with small diameter formed. The pores essentially have one Diameter in the range of 2 to 14 nm. In contrast, will when in the process according to the invention used raw clay, the essential part of the pore volume of Pores formed, which have a much larger diameter.

Characteristic for the used according to the invention Rohtone is that at least 40% of the total pore volume (determined according to the BJH method, see. below) are formed by pores having a pore diameter greater than 14 nm. Preference is given to more than 50%, and more preferably more than 60% of the total pore volume of Formed pores having a diameter of more than 14 nm. The total pore volume of these raw clays is, as already explained, more than 0.5 ml / g. The pore radius distribution or the total pore volume is determined by nitrogen porosimetry (DIN 66131) and evaluation of Adsorption isotherm determined by the BJH method (see below).

It Rohtone was found to have the properties described above even by activation with small amounts of acid, e.g. in the aforementioned "in situ activation" in bleaching earth products can be converted the surprising have good bleaching properties. The bleaching effect of these bleaching earth products achieves the results of highly active bleaching earths or exceeds them these even. Under a "in situ activation " understood an activation treatment of the raw clay, as with the acid activated as described above Bleaching earths (SMBE) common is.

Generally can the activation according to the invention The raw clays are to be carried out by a treatment with acid. These are the raw clays with an inorganic or organic Acid in Brought in contact. In principle, any method familiar to the person skilled in the art can be used for acid activation of clays, including those in WO 99/02256, US 5,008,226, and US 5,869,415, the expressly so far be incorporated by reference into the description.

According to a preferred embodiment of the invention, it is not necessary that the over acid and the salts formed during activation are washed out. Rather, after the task of acid, as usual in the acid activation, no washing step is carried out, but the treated raw clay dried and then ground to the desired particle size. When grinding, a typical bleaching earth fineness is usually set. In this case, the dry residue on a sieve with a mesh size of 63 microns in the range of 20 to 40 wt.%.

Of the dry screening residue on a sieve with a mesh size of 25 microns is in the range of 50 to 65% by weight.

at an embodiment the method according to the invention the activation of the crude clay is carried out in the aqueous phase. To becomes the acid as watery solution brought into contact with the raw clay. It can be done this way be that first the raw clay, which is preferably provided in the form of a powder is slurried in water becomes. Subsequently becomes the acid added in concentrated form. However, the raw tone can also be direct in an aqueous solution the acid slurried be, or the watery solution the acid be abandoned on the raw clay. According to an advantageous embodiment can the watery Acid solution, for example be sprayed onto a preferably cracked or powdered raw clay, wherein the amount of water is preferably chosen as low as possible and e.g. a concentrated acid or acid solution used becomes. The amount of acid may preferably be between 1 and 10% by weight, more preferably between 2 and 6 wt .-% of a strong acid, in particular a mineral acid such as Sulfuric acid, based on the anhydrous raw clay (atro) can be selected. If necessary, can excess water be evaporated and the activated raw clay then to the desired Fineness to be ground. As already explained above, is also in this embodiment the method according to the invention no washing step required. After abandonment of the aqueous solution the acid becomes only, as far as necessary, until reaching the desired Moisture content dried. Mostly the water content of the obtained bleaching earth product to a level of less than 20 % By weight, preferably less than 10% by weight.

For the above described activation with an aqueous solution of an acid or a concentrated acid can the acid chosen arbitrarily become. It can both mineral acids, as well as organic acids or mixtures of the above acids be used. It can be used conventional mineral acids be like hydrochloric acid, phosphoric acid or sulfuric acid, being sulfuric acid is preferred. It can concentrated or diluted acids or acid solutions used become. As organic acids can solutions from e.g. citric acid or oxalic acid be used. Citric acid is preferred.

The Grain size or the mean grain size of the adsorbent according to the invention should preferably be chosen be that at a later Use of activated raw clay or bleaching earth a complete and simple separation of the clay from the refined product is made possible. Preferably, the mean grain size of the powdered raw clay in a range of 10 to 63 μm selected. Typically, the fineness is chosen so that on a sieve with a mesh size of 63 microns about 20 to 40% by weight of the mixture remain (sieve residue) and on a sieve with a mesh size of 25 μm about 50 to 65 wt .-% of the mixture remain. This can be referred to as typical bleaching earth fineness.

As already explained, can with the method according to the invention in a simple and inexpensive way Adsorbents and bleaching earth products provided whose adsorption or bleaching activity is surprisingly high and in in some respects about the activity conventional highly active bleaching earth.

object The invention is therefore also an adsorbent, in particular a bleaching earth product obtained by the method described above available is. The adsorbents of the invention can economical produced, for example because no waste products are produced, which must be disposed of consuming. Due to their high bleaching activity enable it is the adsorbents of the invention the quantities, which for the refining of, for example, oils and fats required are to be reduced substantially. As a result, too the losses of starting product, such as oils and fats, which occur during separation of the adsorbent remain in this, substantially reduced become.

The invention therefore also relates to the use of the above-described adsorbent as bleaching earth. Particularly preferably, the adsorbent described above is used for the refining of oils and fats, in particular for the refining of vegetable oils. Next, the invention can proper adsorbents are also used as a desiccant or for the adsorption of gases.

• – einer spezifischen Oberfläche von mehr als 200 m²/g;
• – einem spezifischen Porenvolumen von mehr als 0,5 ml/g; und
• – einer Ionenumtauschfähigkeit von mehr als 40 meq/100g.

The crude clay used for the preparation of the adsorbent according to the invention already has advantageous properties on its own, such as its easy and high activatability with acid. The invention therefore also a clay product containing a raw clay with

• A specific surface area of more than 200 m ² / g;
• A specific pore volume of more than 0.5 ml / g; and
• - an ion exchange capacity of more than 40 meq / 100g.

The specific surface area (BET area) and the specific pore volume are determined by means of nitrogen porosimetry according to DIN 66131. The specific surface area is preferably in the range of 200 to 270 m ² / g, particularly preferably in the range of 200 to 260 m ² / g. The specific pore volume is preferably 0.5 to 1.0 ml / g, particularly preferably 0.7 to 1.0 ml / g. The ion exchange capacity is determined by the method described below in the Examples. It is preferably more than 50 meq / 100 g and is more preferably in the range of 55 to 75 meq / 100g. A slurry of 10% by weight of the raw clay in water preferably has a pH in the range of 6.0 to 8.5. The pH is determined with a pH electrode.

As already explained, the raw clay has a characteristic distribution of pore radii on. At least 40% of the pore volume is through pores with a Diameter of more than 14 nm provided. Preferably, at least 50% of the pore volume, more preferably at least 60% of the Pore volume of pores having a diameter of at least 14 nm provided. The pore size or the pore size distribution let yourself by nitrogen porosimetry according to DIN 66131 and evaluation using the BJH method. The total pore volume refers to pores with a diameter of 2 to 130 nm. The Clay product is preferably 100% raw clay.

The The invention will be explained in more detail by means of examples.

It the following analytical methods were used:

Surface area / pore volume

The surface was on a fully automatic nitrogen porosimeter of the company Micromeritics, type ASAP 2010, carried out according to DIN 66131. The Pore volume was determined using the BJH method (E.P. Barrett, L.G. Joyner, P.P. Haienda, J. Am. Chem. Soc. 73 (1951) 373). Pore volumes of certain pore size ranges are summed up Incremental pore volumes determined from the evaluation of the Adsorption isotherms are obtained according to BJH. The total pore volume according to the BJH method refers to pores with a diameter of 2 to 130 nm.

Oil Analysis:

The Color numbers in oils (Lovibond color numbers) were determined according to AOCS Cc 13b-45 determined. The chlorophyll A determination was carried out according to AOCS Cc 13d-55.

Water content:

Of the Water content of the products at 105 ° C was determined using the method DIN / ISO-787/2.

Silicate:

These Analysis is based on the total digestion of the raw clay or the corresponding Product. After dissolving The solids are the individual components with conventional specific analytical methods, e.g. ICP, analyzed and quantified.

Ion exchange capacity:

To determine the ion exchange capacity (IUF), the raw clay to be investigated was dried at 105 ° C. over a period of two hours. Thereafter, the dried material was reacted with an excess of aqueous 2N NH ₄ Cl solution for one hour under reflux. After a booth time of 16 hours at room temperature was filtered, whereupon the filter cake was washed, dried and ground and the NH ₄ content in crude clay was determined by nitrogen determination (CHN analyzer from. Leco) according to the manufacturer's instructions. The proportion and type of exchanged metal ions was determined in the filtrate by ICP spectroscopy.

X-ray:

The radiographs be at a high resolution Phillips powder diffractometer (X'-Pert-MPD (PW 3040)) created with equipped with a Cu anode was.

example 1

Characterization of the raw clay

A crude clay suitable for the process according to the invention (Süd-Chemie AG, Moosburg DE, crude clay storage Ref. No .: 03051) was investigated with regard to its physicochemical properties. The results obtained are summarized in Table I. Table I Physical-chemical analysis of raw clay

Example 2

Activation of the raw clay with sulfuric acid

The crude clay characterized in Example 1 was mixed with water and then activated with 3% by weight of H ₂ SO ₄ . For this purpose, 100 g of powder dried to 9.3% H ₂ O were intimately mixed with 208 g of water and 2.83 g of H ₂ SO ₄ (96% strength) in a beaker. The resulting mixture was dried at 110 ° C. to a water content of 9.4% and then ground to a typical bleaching earth fineness (dry sieve residue to 63 μm sieve: 20 to 40% by weight, dry sieve residue to 25 μm sieve: 50 to 65% by weight. -%).

Comparative Example 1

Sulfuric acid activation of acid attapulgite / bentonite for producing a bleaching earth according to US-A-5,008,226

A naturally occurring acid mixture of attapulgite and bentonite from the Georgia / USA region was predried to 15 to 20% by weight of H ₂ O, ground via a rotor impact mill and then dried to a water content of 8% by weight. 100 g of the resulting powder was mixed with 309 g Water and 2.88 g of H ₂ SO ₄ (96% strength) intimately mixed in a beaker. The resulting mixture was dried at 110 ° C to a water content of 9% by weight and then ground to a typical bleaching earth yield. (Dry residue on 63 μm sieve: 20 to 40% by weight, dry sieve residue on 25 μm sieve: 50 to 65% by weight).

Comparative Example 2

Reference bleaching earths after the state of the art

When Reference for by dealuminating with acid accessible most active Bleaching earths (HPBE) were the commercially available bleaching earths Tonsil Optimum 210 FF and Tonsil Supreme 110 FF (Süd-Chemie AG). Both Products are made by dealuminating montmorillonite ions with hydrochloric acid produced.

When examples for conventional surface activated Bleaching earth (SMBE) became a commercial product of the company Oil-Dri Supreme Pro Active used. Also the product Tonsil Standard 3141 FF from Süd-Chemie AG corresponds to this substance class.

Example 3

Bleaching of rapeseed and soybean oil

Tabelle III Bleichung von Sojaöl

A degummed and deacidified rapeseed oil or soybean oil was bleached with 0.30 and 0.73 wt .-% of bleaching earth at 110 ° C and 100 ° C for 30 minutes under a pressure of 30 mbar. Subsequently, the bleaching earth was filtered off and the color numbers of the oil were determined using the Lovibond method in a 5¼ "cuvette. A portion of this oil was additionally deodorized by steam treatment (30 minutes, 240 ° C, <1 mbar). The resulting oil was also analyzed by the Lovibond method. Tables II and III give the results of bleaching. Table II Bleaching of rapeseed oil

Table III Bleaching of soybean oil

As Tables II and III clearly show, with the bleaching earth according to the invention after Example 2 an extraordinary good discoloration of the oil (Color red and chlorophyll A) achieved. The values after deodorization are of particular relevance, since in practice almost all oils are after be deodorized in bleaching. The cleaning performance of the bleaching earths according to the invention is in the range or better than the highly active bleaching earths and clearly over the results of surface-activated Bleaching earths according to the prior art.

Claims (14)

A process for producing an adsorbent, in particular a bleaching earth product, wherein a raw clay - having a specific surface area of more than 200 m ² / g, - a pore volume of more than 0.5 ml / g, and - an ion exchange capacity of more than 40 meq / 100g of activation is subjected. The method of claim 1, wherein the ion exchange capability of raw clay larger than 50 meq / 100g is. The method of claim 1 or 2, wherein the raw clay, based on the raw water-free clay, has an Al ₂ O ₃ content of less than 11 wt .-%. Method according to one of the preceding claims, wherein the raw clay has a SiO ₂ content, based on the anhydrous raw clay of more than 65 wt .-%. Method according to one of the preceding claims, wherein the raw clay has a pore volume of more than 0.5 ml / g, wherein at least 40% of the pore volume is provided by pores, which have a pore diameter of at least 14 nm. Method according to one of the preceding claims, wherein the raw clay for surface activation with an acid is brought into contact. A method according to claim 6, wherein the acid is as aqueous solution is brought into contact with the raw clay. A method according to claim 6 or 7, wherein the acid is a mineral acid is. The method of claim 8, wherein the mineral acid is sulfuric acid. Adsorbent obtainable by a process according to one the claims 1 to 9. Use of an adsorbent according to claim 10 as bleaching earth. Use of an adsorbent according to claim 11 for the refining of oils and fats. A clay product comprising a raw clay with a specific surface area greater than 200 m ² / g; A pore volume of more than 0.5 ml / g; and - an ion exchange capacity of more than 40 meq / 100g. A clay product according to claim 13, wherein the raw clay is a pore volume determined by nitrogen porosimetry of more than 0.5 ml / g, wherein at least 40-% of the pore volume of pores be provided having a pore diameter of at least 14 nm.