DE1941119C3 - Process for the hydrogenation of unsaturated polymeric fatty acids - Google Patents

Description

Polymeric fatty acids are well known, commercially available products. These acids were already previously hydrogenated (US Pat. No. 3,256,304). In commonly used processes, nickel catalysts, like Raney nickel and nickel with inert substances like kieselguhr or clays, which are often used as carriers are being used. While such nickel catalysts provided improved color, such catalysts set the iodine number of the polymeric fatty acids is only slightly reduced, especially below the usual ones Hydrogenation conditions. Attempts to reduce the iodine number with the help of such catalysts using more drastic or violent reaction conditions with regard to pressure and temperature, lead while the iodine number is reduced somewhat, leading to a breakdown of the product. In US-PS 32 71 410 a two-stage hydrogenation process is described in which in the first stage up to an iodine number of around 10 or below and in the second stage is post-hydrogenated to an iodine number below 1. This process relates however, exclusively on the hydrogenation of natural unsaturated monomeric fatty acids.

Palladium and ^D latin catalysts have also been used earlier. In US-PS 32 56 304, a method is described, wherein the polymerized fatty acid means a noble metal catalyst in a hydrogenation step to an iodine value of about 10, and including hydrogenated and then purified by fractional distillation ^ _0. While such catalysts are effective in improving color and producing relatively low iodine numbers, they are expensive to use, especially when used in amounts that produce optimal results. Such catalysts are also contaminated or “poisoned” during the process, which has further economic disadvantages.

The invention is based on the object To avoid disadvantages and to improve the process for the hydrogenation of polymeric fatty acids

This invention relates to an improved process for the hydrogenation of unsaturated fatty acids! by prehydrogenation in the presence of a nickel catalyst and subsequent hydrogenation in the opposite waiting a palladium catalyst, which is characterized ge that it is in is to be hydrogenated) fatty acids to polymeric fatty acids to that first the polymeric fatty acids in Gegenwar of about 0.1 to 5 Percentage by weight, based on di polymeric fatty acids, of the nickel catalyst at temperatures of about 150 to 225 C and hydrogen pressures of over 0.35 atmospheres, the iodine number is only slightly reduced, and then the reaction product of the prehydrogenation in the presence of about 0.05 up to 1 Ge weight percent, based on the prehydrogenated product of the palladium catalyst, is post-hydrogenated at temperatures in the range from 175 to 275 C and a hydrogen pressure of over 7 atmospheres

A particular embodiment of ejfindungsgemäßen method is characterized in that the product of the first hydrogenation before de ^r post-hydrogenation with palladium catalyst with an acid-activated montmorillonite clay and phosphoric acid is treated.

In the first step where a nickel catalyst is used, the color is significantly improved. The application of the nickel catalyst alone leads but not a significant reduction in the iodine number. Another improvement in color and a significant reduction in the iodine number is achieved in the second reaction stage, in which the palladium catalyst is used. It has been found that by using the step with the nickel catalyst prior to hydrogenation with palladium the amount of palladium that is required to produce the color and to achieve the low iodine number is much less than the amount of palladium you can get needed to get the same results without pre-hydrogenation with nickel. It was further found that the contamination or poisoning of the palladium catalyst, wt.in not completely eliminated, so it does is minimized when the pretreatment is carried out with a nickel catalyst will. For this reason, the palladium catalyst can be reused, which is further significant brings economic benefits. Furthermore, smaller amounts of catalyst allow a light one Filter. It was also found that the inventive method to an essential Improvement of the desired or improved result of low color and iodine number leads using milder reaction conditions, so that the degradation of the product caused by the hard Hydrogenation conditions was brought about, is reduced to a minimum.

As mentioned above, the process of the invention relates to the hydrogenation of polymers Fatty acids. Polymeric fatty acids are well known and are commercially available. The term »polymer Fatty acid, as used here, refers to a polymerized fatty acid either in dimeric form or trimeric form or in higher polymeric forms. Commonly available products usually contain as the main ingredient dimeric acids, eerinee

Amounts of trimeric form and of high polymer Forms and some remaining monomers. The term, "trimer," as it is used here, is intended also include the higher polymer forms. The term "fatty acid" as used here relates to to the naturally occurring and synthetic monobasic aliphatic acids with hydrocarbons ofl chains that contain 8 to 14 carbon atoms.

Sources for the naturally occurring fatty acids are e.g. B. Fats and oils, such as the drying ones or semi-drying oils. The polymeric fatty acids result from the polymerisation of drying or semi-drying oils or their free fatty acids or the esters of such acids with simple aliphatic alcohols like ζ. Β the methyl or other alkyl esters in which the Alkyl group has 1 to 8 carbon atoms. Include suitable drying or semi-drying oils a: soybean oil linseed oil, tung oil. Pcrilla oil, Oiticica-61, cottonseed oil, corn oil, sunflower oil, safflower oil, dehydrated castor oil and the like. Suitable fatty acids can also be obtained from tall oil, soap raw material and other similar products. In the polymerization process they combine Fatty acids with each other to form a mixture of dimeric and higher polymeric forms, which in the generally referred to as dimer, trimer, etc. A method of polymerizing the unsaturated Fatty acids with the aid of a clay catalyst "is given in US Pat. No. 3,157,681.

When examining the colors obtained by the method according to the invention, colors become with a color number according to G a r d η e r of less than 1, which is the lowest or lowest color number according to the Gardner standard. Since it is possible according to the method according to the invention, colors with Gardner color numbers of less than 1, another method of determination must be used of color can be applied to represent the relative color numbers below that point. Photometric methods of measuring color are one route that can be taken.

One such method is to use a Coleman Jr. Model 6 A spectrometer, which is opposed to a standard nickel sulfate solution is calibrated and gives the following readings:

25 and 30 C fills up. The nickel content of the solution should be between 4.40 and 4.46 g nickel per 100 m be. After calibration, the permeability of a 25 ml sample in a cuvette is measured at 10 to 20 ( read at 5 wavelengths between 400 and 500 mu, using a 25 ml cuvette with distillation Temp water is used to set the transmittance to 100% at each wavelength. The middle man out of these five values is the photometric color

Photometric paint

D ₄₀₀ + D ₄₂₅ + D ₄₅₀ + Z) ₄₇₅ • ς

where D is the percent permeability.

Unless otherwise stated, the photometric color was determined in accordance with the Me method determined. For the purpose of comparison and al; Guideline below is a comparison of color Gardner numbers with the photometric colors described above are given for some samples

Color number according to Photometric Faroe Gardner (%) 7 to 8 18.6 6 to 7 24.2 5 to 6 32.8 4- 47.4 1 to 2 63.4 1 to 2 65.8 1 + 68.5 1 + 69.8 1 + 71.3 78.3 80.5

Millimicron (πΐμ) Permeability 400 below 4.0 460 26.2 ± 2.0 510 73.9 ± 1.0 550 54.8 ± 1.0 620 5.2 ± 0.5 670 1.1 ± 0.5 700 below 2.0

The instrument is calibrated with a standard nickel sulfate solution, which is commercially available in a 25 ml cuvette. This standard solution can also be prepared by dissolving 200 g NiSO ₄ -OH ₂ O pa and exactly 1000 ml in a volumetric flask at a temperature between

When considering the given relationship it is) to remember that the color number according to G a r d η e ι is a visual comparison of the color sample with a standard and is therefore not an accurate reading This is particularly true when the Gardner color number is in the range of 1. So corresponds a color number according to G a r d η e r of 1 approximately a photometric color of about 74 to 79%.

When discussing the polymeric fatty acids, reference is made to the content of mono mers (M), dimers (D) and trimers (T). The. Amounts thereof are measured in percent by weight Gas-liquid chromatography determined the corresponding methyl ester. With such a fractionation method an intermediate fraction is found between the monomers and the dimers, which is is designated accordingly as intermediate (Z).

The iodine number is given in multiples of 10 " ² ^ iodine which are absorbed by 1 g of the sample. Si" is determined according to the rapid method of Wi js, which consists in using chloroform and carbon tetrachloride as the solvent for the sample instead of carbon tetrachloride Sample quantities of 0.250 g or less used. In each of the hydrogenation steps, the reaction conditions vary with respect to time and temperature

and pressure over a wide range, although it is preferable, under milder reaction conditions to work. The hydrogenation is usually carried out at pressures above 7 atii, it has been so high pressures such as 211 atm or higher were applied. However, since in the process according to the invention the substantial reduction in the iodine number in the hydrogenation stage is carried out with the palladium catalyst, the previous treatment with the: Nickel catalyst even at very low pressures. z. B. of over 0.35 atmospheres, preferably over 0.70 atmospheres. respectively. In the hydrogenation stage with the palladium catalyst, however, pressures of over 7.0 to 84 atmospheres are preferred, while pressures of 7.0 to 35 atmospheres are preferred in the case of hydrogenation with nickel be used when carrying out the process in batches. The hydrogenation will normally carried out over a wide temperature range. In the present invention, the temperature is when the process is carried out batchwise about 150 to 225 C for hydrogenation with nickel and about 175 to 275 C for hydrogenation with Palladium, with temperatures of about 180 or 225 ° C being most preferred. For a discontinuous Procedures take about 1 to 10 hours, and the implementation normally takes time 3 to 5 hours. The exact temperature. Pressure and especially time conditions are not critical, however, they must all together be sufficient for hydrogenation. In a continuous process are z. B. takes as little time as 5 to 30 minutes. Furthermore, in a continuous If desired, higher temperatures and pressures can be used with regard to the process shorter duration of the reaction, which would otherwise lead to significant decomposition of the product. The shorter The reaction time leads to a shorter one, despite the stricter pressure and temperature conditions Decomposition.

A typical process for hydrogenation in two steps can be seen from the following, in which the examples used to explain the Invention follow, methods used is described

The polymeric fatty acids and catalyst are placed in a 19-1 stirred stainless steel vessel filled. The vessel is closed, evacuated and hydrogen filled under pressure. The content of the The reaction vessel is then heated under hydrogen pressure. The excess pressure is then released and the vessel is cooled to 150.degree. The catalyst is then filtered off under nitrogen pressure removed.

At the first step in which a nickel catalyst is used, any unsaturated bond reducing nickel catalyst can be used including commercially available catalysts such as Raney nickel or nickel or in combination with inert carriers such as kieselguhr. Alumina or clays. Any inert carrier can be used for the nickel catalyst. The one preferably used according to this invention The catalyst is nickel on kieselguhr and contains about 50 to 55% nickel. The amount of catalyst used varies depending on the specific catalyst and the reaction conditions used. The preferred catalysts are amounts of 0.1 to 1.0, in particular 0.25 to 0.75%. used. Normally at higher pressures and temperatures, i.e. 70atü and 2Ü0 C, an :: amount from O.25 ° o e suitable. while at conditions of 28 atü and 180 C an amount of about 0.5% and more is desirable.

For the second hydrogenation step, a palladium catalyst is used, which is normally on an inert carrier such as charcoal or the like is applied. Any inert carrier can can be used: the use of charcoal as a carrier material is preferred, however. For the execution of the process according to the invention, a catalyst is used, for example, which consists of 5% (Weight percent) consists of palladium on carbon. There are other catalysts that use carbon as a carrier. containing 1 or 2% palladium. As with the hydrogenation with nickel, the amount of used depends Catalyst on the type of catalyst and the reaction conditions used. A preferred one The amount of catalyst is 0.1 to 0.5%. In discontinuous processes with the preferred Catalyst. 5% palladium on carbon, is used at higher temperatures and pressures, i. H. 70 atm and 250 C. approximately 0.1% (calculated on a dry basis) preferred, while at 28 atm and 180 ° C. about 0.25% "is preferred.

If desired, an additional reaction step can be inserted. This step is optional inserted after hydrogenation with nickel and before hydrogenation with palladium. The step consists in an acid treatment of the product hydrogenated with the aid of the nickel catalyst. It was found this treatment to be a further improvement the color and color stability as well as any nickel salts that result from the hydrogenation originate with the help of nickel, eliminated or removed. Although this treatment is desirable is. they can be dispensed with in order to obtain optimal results. When nickel salts are present and not during the subsequent reaction step or in the final product for reasons of color. Color stability or the iodine number are tolerable is this treatment is extremely desirable. If necessary, other methods of removal can also be used of nickel salts or to prevent their formation.

In this optional measure, the product hydrogenated with the help of nickel is activated with an acid Montmorillonite clay and phosphoric acid treated.

For this treatment, the clay is used in an amount of about 1 to 10%, preferably about 1 to 3% (based on the weight of polymeric fatty acid). The phosphoric acid is preferably used in a concentration of 60 to 85% and in an amount of about 0.25 to 3% (based on the weight of polymeric fatty acids). An amount of about 0.5 to 1.0% phosphoric acid is preferred (70 to 75%).

Preferably, the product of the hydrogenation with the aid of the nickel catalyst to 100 C or less cooled before the clay and acid are added. Treatment is preferred in an atmosphere of nitrogen, carbon dioxide or hydrogen, or in any atmosphere carried out in the absence of oxygen. The mixture is then used for about 15 to 60, preferably Heated to about 120 to 130 ° C. for 30 minutes under a pressure of over 0.35 atm. The pressures will

20th

adjusted either with nitrogen or with hydrogen, hydrogen being preferred. Press up to about 14 atii can be used, but pressures of 7 ati are normally used not exceeded. After the treatment, the pressure in the reaction vessel is equalized and Vacuum applied to completely remove water. The mixture is then at about 100 to 150 C, preferably about 125 C, filtered.

Commercially available polymeric fatty acids were used to exemplify the invention used. Such polymeric fatty acids are tall oil fatty acids polymerized by means of clay. Typical tall oil fatty acids, that are polymerized today are those that are commercially available and the following typical analysis values show:

Acid number (S.Z.) 192.0

Saponification Number (V.Z.) 196.7

% Unsaponifiable 1.5

Iodine number (J.Z.) 133.4

Gardner color 4 to 5

The polymeric fatty acids obtainable therefrom show the following typical analytical values:

S 2 about 193

V. Z ^about I ⁹⁸

} 'z' about 115

The different grades available differ in color and dimer fatty acid content. A typical level of dimeric fatty acid is about 70%, and a typical color number according to G a r d η e r is about 5 to 8. Other qualities contain more than 90% and have dimeric fatty acids Color numbers according to G a r d η e r from about 3 to 6.

The invention is illustrated by the following examples.

example 1

step 1

In this example, the starting material was a clay polymerized tall oil fatty acid with the following Analysis values:

See Z 192.3

V. Z 197-3

J.Z 114.8

Gardner color ⁵⁺ _ ₄

% Iron 1 · 1 ° ₄

% Phosphorus ⁱ⁶¹⁰

% Ash 9 ¹

% M

% Z
% D
% T

⁵ x ⁵ 71.0

¹⁵ - ⁵

After the above process of this invention were hydrogenated 158.9 kg of polymeric fatty acids m the presence of 795 g (wet weight) of Raney emes NIDCD-KatalysatOTS. The "5 ^ 5 ™ ^ will iö 2 Standen at 18ÖC rad eaeia pressure of 28 atä dorchgeföhi-t The product obtained (A> featteiiaeiidein filtering at 70 Ceinephoteinetnscne ifc of 52.6% ma eifie Jodzafcl of 95A

The experiment was carried out with the same reactants in the same amounts and under the same Conditions repeated. The obtained product (B) had a photometric color of 56.3% and a Iodine number of 91.2.

Level 2A

This example shows the subsequent hydrogenation with the aid of falladium. It became that Hydrogenation process according to the invention applied. The starting mail consisted of 52.2 kg of product A and 20.4 kg of product B of stage 1. The palladium catalyst was 5% palladium on carbon, which is about 50% Contained moisture. Of these, 363 were used.

The hydrogenation was carried out at 56 atmospheres and 200 ^° C. in 4 hours. The product obtained showed the following analysis values:

See Z 191

V. Z 199.7; 200.7

J. Z 20.0

Photometric color 78.5%

Level 2 B

In this example 90.7 kg of Stage 1 product A were used as the starting material. The catalyst was 454 grams of 5% palladium on carbon with a moisture content of 50% (0.25% catalyst based on dry weight). The hydrogenation was carried out in 4 hours at 200 ° C. and 28 atm. Samples were taken at periodic line intervals, the iodine numbers of the various samples and the properties of the end product can be seen from the following data:

Sample J. Z.

40

45

55

1 hour 51

2 hours 33.7

3 hours 28.2

End product

J.Z 21.6

Photometric color 80.1%

S. Z 189.6

V. Z 195.4; 194.4

Ash 0.02; 0.04

% Nickel 7x10 " ⁴

Example 2
Stage 1

In this example the starting material was a Tall oil fatty acid, polynierized by means of clay, which had the following analytical values:

60

65

SZ 191.7: 191.5

V. Z. 196.0; 1963

J.Z. 95.1: 94.1

Gardner color

% M

% Z

8 +

6.1

8.8

% D % T

ms

15.1

609634/103

136.1 kg of this were obtained by the process according to the invention using 1.36 of a nickel catalyst hydrogenated, which consisted of 50 to 55% nickel on kieselguhr. The reaction lasted 4 hours at about 180 ° C and 28 atm. The product obtained had a color number after filtering at 150 "C. according to G a r d η e r from 4.

The product obtained was then an acid treatment, as described above, with the addition of subjected to 3.2 kg of an acid-activated montmorillonite clay and 0.6 kg of 70% phosphoric acid. The treatment was carried out at 125 ° C. for 30 minutes. The product obtained had after Filtration has a G a r d η e r color number of 3 and an iodine number of 84.

Level 2

50.3 kg of the product obtained in step 1 after the acid treatment were then mixed with 125 g of des Palladium catalyst according to Example 1, Stage 2 B (0.25% based on wet) according to the invention Process and hydrogenated under reaction conditions of about 200 ° C. and 28 atmospheres for 4 hours. The The product obtained had a photometric color of 75% and an iodine number of 26.4.

B e i s ρ i e 1 3

step 1

In this example, 136.1 kg of a tall oil fatty acid polymerized by means of clay were used, which the the following analyzes showed:

S. V 194.5: 194.4

V. Z 198.5; 198.9

J. Z 120.1

Gardner color 5 -

% Iron 7 x 10 ~ ⁴

% Phosphorus 9 · ΙΟ " ⁴

% Ash 0.00

% M 1.1

% Z 3.8

% D 93.3

% T 1.8

Level 2

For the hydrogenation by the process according to the invention, 68O g of the nickel catalyst on kieselguhr according to Example 2, stage 1, were used and reaction conditions of about 180 ^° C. and 28 atmospheres were applied for 4 hours. The product was then treated with acid and clay in the same way as in Example 2, level 1, with 5% of the same acid-activated montmorillonite clay and 1% phosphoric acid (70 to 75%) being used. After removing excess water and after filtering at 10OC, the product showed the following analyzes;

SZ 194.6

V. Z. 200.4

SZ 100.4

% M 1.2

% Z 3.7

% D 93.8

% T 1.3

60

63.5 kg of the product from stage 1 were then hydrogenated by the process according to the invention with the aid of 318 g of the catalyst from example 1, stage 2A. The hydrogenation conditions were about 200 ^° C. and 28 atm. For 4 hours. The product obtained had a photometric color of 92%. After another filtration, the product had a photometric color of 94.5% and an iodine number of 15.6.

Example 4
step 1

In this example, the starting material was a clay polymerized tall oil fatty acid with the following Analysis values:

S. Z 194.3; 193.9

V. Z 196.2: 196.0

J. Z 109.1; 108.9

Gardner color A-

% M 0.6; 0.4

% Z 4.3; 4.4

% D 92.5; 92.5

% T 2.6-2.7

88.9 kg of these polymeric fatty acids were hydrogenated with the aid of 454 g of the nickel catalyst on kieselguhr (cf. Example 2, step 1) by the process according to the invention at about 180 ° C. and 28 atmospheres for 4 hours. The product obtained had an iodine number of 90.6 and 90.2, respectively, and a photometric color of 84.6 before the acid treatment. The acid treatment was carried out with 4.54 kg of an acid-activated montmorillonite clay, 907 g of phosphoric acid (85%) and 907 g of water at 70 to 75 ^° C. for 1 hour.

The above experiment was repeated under the following reaction conditions: 4 hours, approx 170 "C, 66.5 atmospheres. The product had an iodine number of 81.1. The photometric color before the acid treatment was 84.9%, afterwards 88.7%.

Level 2

The two products per 45.4 kg according to Step 1 were mixed, and the mixture was subsequently (50% 5% palladium on charcoal, moisture content) is hydrogenated with 181g of the catalyst at about 200 ⁰ C and 66.5 atm for 4 hours. The product obtained had a photometric color of about 95% and an iodine number of 18.3 and 18.9, respectively.

Example 5

The fatty acids polymerized in medium-sized clay used as the starting material showed the following B properties:

^J - z- nm

Gardner color 5

% Iron .. ff @

% Phosphorus ik · H

% Ash "* (fl

ft 1 11 »

% M 8.1

% Z 5.5

% D 71.0

% T 15.5

136.1 kg of these acids were then hydrogenated by the process of this invention by means of 680 g of catalyst (nickel on kieselguhr as in Example 2) at about 180 ^c C and 28atü 4 hours. After the acid treatment with 2.2% of the clay used in the previous examples and 0.5% phosphoric acid (75%) at 115 ° C. for 30 minutes, the product had a photometric color of 65.0%. The product had an iodine number of 92.1 and 91.1, respectively.

This process was repeated, leaving a product with a photometric color of 66.7% and an iodine number 88.9 and 89.7 emerged.

The two batches of nickel hydrogenated products were then combined, and 72.6 kg of them were re-hydrogenated according to the general procedure, the catalyst being 363 g of 5% palladium on carbon (Moisture content 50%, 0.25% on a dry basis) were used. The reaction conditions were 4 hours at 200 ° C and 66.5 atm. After cooling and after pressure equalization, the product possessed an iodine number of 9.5 and a photometric color of 93.5%. After filtration the product had a photometric color of 86.6% and after a second filtration 90%.

The foregoing examples provide some specific illustrations of the present invention. On the basis of these examples and numerous other similar experiments, the preferred embodiment with regard to the reaction conditions and the typical results when using Starting materials of the type of Examples 1 and 3 are summarized as follows, the above described hydrogenation process was used:

I. Pre-hydrogenation with nickel
A. Hydrogenation Conditions

Catalyst nickel on kieselguhr

Catalyst amount 0.5%

Pressure 28 atm

Temperature 180 ^r C

Time 4 hours

B. Acid treatment of the dimer hydrogenated by means of nickel

The nickel hydrogenated alloy and the catalyst are cooled to below 100.degree. The pressure in the reaction vessel is equalized and a nitrogen atmosphere is created. Then 2% of the clay mentioned and 0.5% of 75% phosphoric acid are added. A hydrogen pressure is generated and heated to 125 ° C; the temperature of 125 ° C. and a hydrogen pressure of 7 atmospheres are maintained for ¹ liter for ₁ hour. The hydrogen is then removed and a vacuum is applied to remove water.

It is then filtered under nitrogen pressure.

C. Typical product analyzes

Example 3 Example I.

Iodine number 85 to 110 85 to 110

Photometric color 75 to 90% 50 to 70% (% transmittance)

% M, Z, D and T deviate only slightly

from the source material

II. Post-hydrogenation with palladium A. Hydrogenation conditions

Example 3 example 1

Starting material with nickel as a catalyst

pre-hydrogenated dimer

Catalyst 5% palladium on carbon

Pressure 70 atm. 28 atm

Amount of catalyst 0.1% 0.25%

(based on dry basis)

Temperature 200 ⁰ C 180 ° C

time

4 hours

4 hours

B. Typical results

70atu Example 3 Iodine number 10 to 15 Photometric color 97+ (% Permeability) S.Z. 194 V. Z. 197 % M, Z, D and T deviates

example 1

until 20
to 90

28 atü
Example 3

example 1

10 to 20
95 +

194

197

differs slightly from the original material.

20 to 30 SG to 85

192 196

3689

Claims (2)

Patent claims: 1. Process for the hydrogenation of unsaturated fatty acids by prehydrogenation in the presence of an s Nickel catalyst and subsequent hydrogenation in the presence of a palladium catalyst, thereby characterized in that the fatty acids to be hydrogenated are polymeric fatty acids and that the polymeric ίο first Fatty acids in the presence of about 0.1 to 5 percent by weight, based on the polymeric fatty acids, of the nickel catalyst at temperatures of about 150 to 225 C and hydrogen pressures above 035 atmospheres, the iodine number is only slightly reduced, and then the reaction product of the pre-hydrogenation in the presence of about 0.05 to 1 percent by weight, based on the prehydrogenated product, the palladium catalyst at temperatures in the range from 175 to 275 C and a hydrogen pressure is rehydrated from over 7 atmospheres. 2. The method according to claim 1, characterized in that the product of the first hydrogenation before re-hydrogenation with the palladium catalyst with an acid-activated montmorillonite clay and phosphoric acid is treated.