DE2625868A1 - PROCESS FOR THE PROCESSING OF NATURALLY OCCURRING SILICATES - Google Patents

Description

Steirische Magnesit-Industrie Aktiengesellschaft 1130 Vienna, Fleschgasse 34

Procedure for a

The invention relates to a method of manufacture of surface-active materials, in particular for use as filter material, bleaching material, adsorbent as well as filler.

Active siliceous earths and related products take on an ever increasing importance on the most diverse Areas of industry, research, medicine, environmental protection, radiation protection technology, etc. Of the numerous Possible uses of such surface-active materials are:

Absorbent for nitroglycerine, decolorizing, filtering and deodorising aids for organic and aqueous solutions (especially in the chemical, pharmaceutical and food industries, Waste water technology, etc.) Adsorbents for gases, fillers in paints, plastics, soft and hard rubber, piece and matting agent in plastic fibers, absorptive retarding agent or adsorbents of radioactive gases

subsequently changed

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(Filter sand for radioactive aerosols) catalyst and / or catalyst carrier oil binder

Antacids (medical treatment of the intestinal tract) Regenerating aid for used lubricating and motor oils Refractory raw material

So far, naturally occurring siliceous earths have primarily been used for the above-mentioned purposes, but these are not available in unlimited quality in the appropriate quality, or, such as low-grade diatomaceous earth materials, do not meet the chemical and physical requirements, in particular due to increased contamination of Fe ₃ O ₃ , Al ₃ O ₃ and alkalis.

The invention relates to a method for processing natural silicates by treatment with hydrochloric acid, Separation, drying and, if necessary, grinding of the residue for the purpose of producing surface-active materials with high BET numbers, especially for use as filter material, Bleaching material, absorbent as well as filler, the inventive method consists in that as a natural Silicate serpentine of the following composition:

SiO ₂ 30-45% by weight

Loss on ignition 0.1-18% by weight

0-2% by weight

Fe ₃ O ₃ 0-10% by weight

CaO 0-2% by weight

MgO 40 - 55 wt .-%

Ni 0 - 0,5Gew _o -%

used and this mm with a grain size of not more than 5, preferably 1-3 mm, is treated with dilute hydrochloric acid, wherein the treatment is interrupted as soon as the undissolved residue between 70-35 wt _o -% based on the employed has reached serpentine _o Basically there are two different forms of treatment with hydrochloric acid. On one hand, the magnesium silicate may be hot or boiling _o

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dilute hydrochloric acid, preferably with hydrochloric acid of azeotropic composition, on the other hand by acid treatment in the cold Condition, each of which can be treated in one or more stages.

At least 50% by weight, in particular 80% by weight.

the grain size of the serpentine should preferably be between 1-3 mm.

It has been found that it is possible. interrupt the HCl treatment as soon as the undissolved Residue between 70-35 wt .-%, based on the serpentine used, has reached, provided that the treated serpentine has a maximum grain size of 5 mm; In the case of larger grain sizes, the aim according to the invention (high BET numbers) cannot be achieved because black cores appear in the end product with a grain size of more than 5 mm. Preferably should a grain size of 1 to 3mm is present. The upper limit of 3 mm results from the fact that even with grain sizes of over 3 mm in some cases the BET number of the end product is reduced due to the presence of undissolved nuclei. Particularly Surprisingly, the lower limit of 1 mm in the preferred grain size range of 1-3 mm was to be expected would be that the BET surface areas of the end products increase with smaller grain sizes below 1 mm. The fact is, however, that a larger proportion of fines has a detrimental effect on the surface activity of the end product.

_{RM Müller, W 0} Hesse and F. Sinigori (BHM 1950/51) report on the exploitation work carried out on serpentine with acid, although this work is only aimed at the extraction of nickel (as a result of the war-related scarcity of raw materials).

The inventive method makes it possible to use almost unlimited natural raw materials, namely Serpentine, by treatment with dilute hydrochloric acid, makes it a highly valuable silica material

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received, which due to its inner surface as well
its relatively firm and granular structure is very special
Uses permitted. Of course, this includes
If this material is present in granular form, it is not sufficient to use this material in powdery form.

The fraction remaining as a silica skeleton after the process according to the invention, that is active silica, has a micro-cavity structure with a high specificity
Surface, internal functional hydroxyl groups and, in addition, a stable grain structure door.

According to the invention, end products which have optimal activities and maximum specific surface areas and can
conventional materials of this type are superior in some respects.

Active silicas obtained according to the invention gave, for example, the following effects:
oil absorption capacity:

Spindle oil was added to every 2 g sample up to the saturation limit. With 2.10 g of oil per 2 g of silica (0-0.06 mm) obtained according to the invention, a good binding effect results.
Decolorization of organic hydrocarbon compounds, e.g. premium gasoline:

An organic dye (red) is molecularly dissolved in premium gasoline. 10 g of active silica obtained according to the invention are mixed with premium gasoline in a column as a column until traces of a pink color appear in the filtrate. 10 g of the decolorize
Sample (0-0.06 mm) 100 ml premium gasoline; as a comparison, common diatomaceous earth with 10 ml / 10 g is a power of ten lower, while diatomaceous earth, for example, remained ineffective at all.
Decolorization of fruit lemonade:

On a column containing 10 g of silica obtained according to the invention
Commercially available fruit lemonade was added in a 20-fold dilution. The amount applied up to the first pink coloration of the filtrate was 25 ml / 10 g decolorizing capacity,

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which of the 2-3 fold effect of kieselguhr (5-10 ml / 10g) is equivalent to.

Decolorization of raw sugar:

Here can with washed silica obtained according to the invention a pH-constant decolorization can be carried out, the ion exchange capacity remaining negligible.

According to the invention, however, the basic analysis fraction (MgO, Fe ^ O and accompanying elements) can also be obtained by cold extraction of the raw product can only be reduced to the extent required by other requirements - with high surface activity at the same time - corresponds, for example, if the end products are used as protective sand with simultaneous binding effectiveness Acids or as a carrier material in the pharmaceutical industry for medicinal substances, where the combination of magnesium silicate with high internal surface area is desired, or for use in reactions in which it is desired to influence the pH value such as reducing reaction-related shifts into the acidic range or achieving desired shifts used in the basic area, e.g. in refining processes should be.

The invention is explained in more detail by means of test examples. The experiments show the influence on the quality properties of the silica skeleton is output as a function of particle size, the concentration of the solvent, the temperature of the uid extraction time.

Example 1 This example concerns extraction at room temperature.

100 g serpentine with the chemical composition: loss on ignition 15.0%, SiO ₂ 32.5%, MgO 43.9%, Fe ₃ O ₃ 6.95% and grain size 1 - 3 mm (and 0-0.5 mm) 400 ml of 20% hydrochloric acid were added and the mixture was left to stand for 48 hours at room temperature, with occasional stirring. After the extraction was complete, it was filtered. The resulting residue was washed acid-free, dried and the percentage of the serpentine used -

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calculates (= 1st extraction stage, see table 1). The residue was subjected a second and third time, each time with fresh acid, to the procedure outlined above (= 2nd and 3rd extraction stage, see Table 1).

The experiment was repeated several times and the result data obtained are averaged accordingly and listed in Table 1.

Table 1

Determinants Dim. step 1 Level 2 level 3 Residue, based
on inserted
Serpentine 1 - 3 mm Wt% 65 56 53 Residue, based
on inserted
Serpentine 0-0.5 mm Wt% 65 55 52

Test conditions:

Concentration of hydrochloric acid: 20%
Extraction temperature: room temperature Duration of an extraction stage: 48 hours Extraction stages: 3

Grain size of the serpentine: 1-3 and 0-0.5 mm Weight ratio: serpentine to HCl = 1: 4

The residue analyzes of the 2nd extraction stage result in the following approximate average values for the most important characteristics:

MgO 20%, Fe ₃ O ₃ 4%, SiO ₂ 65% and loss on ignition 9.5%.

Despite the relatively low dissolution intensity of the cold hydrochloric acid the residue materials have a specific upper

area up to over 200 m / g. This high surface activity, furthermore the great stability of the single grain, the MgO depot effect,

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- * 7 -

the functional hydroxyl groups (not annealed), the absence of toxic compounds and a neutralizing effect give the product an extraordinarily high degree of usability and application possibilities in industry.

Example 2 This example concerns extraction at higher temperatures.

100 g of serpentine (analysis see Example 1), grain size 0-0.5 mm, were at reflux using a stirrer with 400 ml of 20% hydrochloric acid at 70-80 ° C and 108-110 ⁰ C extracted two hours. After the extraction was complete, it was filtered. The residue was washed acid-free, dried, weighed and the percentage of the serpentine used was converted (see Table 2).

Table 2

Determining variables Dim. Working temperature

70 - 80 ° C 108 - 110 ° C

Residue, based

based on Ser% by weight used 45.4 39.6

pentin 0-0.5 mm

Test conditions:

Concentration of hydrochloric acid: 20%

Extraction temperature: 70 - 80 ^0C and 108 - 11O ⁰ C

Extraction stage: 1

Duration of the extraction stage: 2 hours

Grain size of the serpentine: 0 - 0.5 mm

Weight ratio: serpentine to HCl = 1: 4

By comparing the percentage of residues with that of Example 1, the time-saving factor of the extraction time can be clearly seen by increasing the temperature. The progressive reduction in the residue (from 65% to 39.6%) results in a steady increase in the silicate structure of SiO ₂ and a simultaneous decrease in the other components (in particular MgO, Fe ₃ O ₃ ). The end-

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degree of extraction desired is thus of the type for

the end product depends on the specific application. Example 3 This example concerns the hot extraction (108 110 C) for different periods of time. 100 g serpentine (analysis see example 1), grain size 0 - 0.5 mm, were refluxed using a stirrer with 400 ml of 20% hydrochloric acid at 108 - 110 ° C for 1/4 hour, Extracted for 1/2 hour, 1 hour, 2 hours and 5 hours. After filtration, the respective residue was as in the example 2 described, further treated (for results see table 3)

Table 3

Determinants Dim.
1 Duration of the Acid treatment in 2 5 H Residue, based
on inserted
Serpentine, 0-0.5 mm Wt% / 4 1/2 1 39.6 37 HCl content of the
Filtrates g / 100ml 45 43 40 2.0 1, 4.5 3.0 2.8 5

V ^ers Uchsbedingungen:

Concentration of hydrochloric acid: 20%

Extraction temperature: 108-110 ⁰ C.

Extraction stage: 1

Duration of the extraction stage: 1/4, 1/2, 1, 2, 5h

Grain size of the serpentine: 0-0.5 mm

Weight ratio: serpentine to HCl = 1: 4

The results show that the extraction process is exponential and asymptotically approaches the final state. Example 4 This example relates to a multi-stage hot extraction (108-11O ⁰ C) with fresh acid in each case. The stage duration is 2 hours. The aim of this experiment is to produce a very pure SiO ^ residue and to optimize it

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the extraction time to an acceptable level in practice.

100 g of serpentine were extracted four times in succession. The individual extraction stages were characterized by the duration of 2 hours, a working temperature of 108 - 110 ° C and the use fresh hydrochloric acid (20%). The individual stages were carried out in the manner already described. The results are shown in Table 4.

Table 4

r.

Determinants Dim. Levels of hydrochloric acid treatment

SiO " Wt% 1 2 3 4th former analysis of the MgO Il Residue: Fe ₉ O
CaO ^ό It Glow v. Il 78.8 85.0 86.0 87.0 Test conditions: ti 6.8 2.0 1/0 0.9 0.9 0.7 0.7 0.7 1/9 1/4 0.8 0.6 8.0 7.7 7.7 7.1

Concentration of hydrochloric acid: 20%
Extraction temperature: 108 - 11O ⁰ C
Extraction time for one stage: 2 hours Extraction stages: 4

Grain sizes of the serpentine: 0 - 0.5 mm
Weight ratio: serpentine to HCl = 1: 4

Example 5 This example shows the influence of the serpentine grain size on the specific surface area of the SiO ₂ residue with hot extraction of 108-110 ° C.

The influence of the particle size distribution of the serpentine on the size of the BET surface area of the SiO ₂ framework can be demonstrated particularly impressively with the aid of table 5 in the case of hot leaching. If the serpentine grain size is reduced during hot extraction, the

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BET surfaces of the SiO ₂ framework are larger, but are decreasing more and more. This differentiation is also present in cold extraction, but to a lesser extent.

Table 5

Dim. Grain size of used Serpentine Parameters m ² / g 0 - 0.06 mm 0 - 0.5 mm 1-3 mm specific
surface 60-80 100-150 200-300

Test conditions;

Concentration of hydrochloric acid: 20%
Working temperature: 108 - 110 ° C
Extraction stages: 2

Extraction time of one stage: 2 hours Weight ratio: serpentine to HCl = 1: 4

The influence of the fine fraction of the starting product used in the extraction on the specific surface of the end product can be seen from the following experiment: Equal parts of raw serpentine with a grain size of 0 to 0.06 mm and raw serpentine with a grain size of 1 to 3 mm were extracted together in two stages (20% HCl, 108 ° C, 1/2 hour, each Step). For the first stage, 450 ml of HCl were added to 100 g of raw serpentine. For the residue of 5O g thus obtained 225 ml of fresh HCl used for the second stage. The residue after the second stage was 42 g and was then divided into the fractions 0 - 0.06 and 1-3 mm separated. For comparison purposes, the same raw serpentine with a grain size of 1 to 3 mm in extracted in the same way as such in two stages.

The following BET values were obtained:

Serpentine 1-3 mm 240 m / g

Separated fraction 1-3 mm 100 m / g

0 - oi / β ram 61 m ² / g.

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Due to the fine fraction (grain size O - 0/06 mm) the surface of the coarse fraction (grain size 1-3 mm) is greatly reduced. A raw serpentine treated in the same way with a grain size of 0.2-3 mm gave an end product

2
with a BET value of 206 m / g.

The method according to the invention integrates these findings and, using preferred embodiments, shows the way which leads to the achievement of a maximum surface area of the SiO ₂ framework. This goal can be achieved if serpentine with a grain size of preferably 1 - 3 mm is extracted with acid and the further comminution of the SiO ^ residue is carried out after the extraction has taken place. An additional separation into fine fractions, for example by air sifting, is a further measure to achieve optimal surfaces. Thus, a preferred embodiment of the present invention consists in that the dried material of the residue is ground to a grain size of 0-0.1 mm and then broken into two by air sifting Fractions, namely one with a separation limit of 0 to 0.03 mm and a second with a separation limit of 0.03 to 0.1 mm.

For certain fields of application it can be advantageous if the residue obtained according to the invention is inherent known way, e.g. by treatment with fatty acid esters, Siloxanes, silicones, ketenes, naphthens, wax, bitumen or petroleum is hydrophobized.

Patent claims:

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Claims (5)

»Β. TTiO. Tf. DB. ν ,, τ. : ■ · :: -! - μ.λχ 1A-46 119 Patent claims: A process for the work-up of natural silicates by treatment with hydrochloric acid, separation, drying and any _r grinding of the residue for the manufacture of surface-active materials having high BET Zshlsn, particularly for use as filter material Eleichmaterial, absorbent and as a filler, characterized indicates overall that as a natural silicate serpentine with the following composition: SiO
2 30 - 45 wt Loss on ignition 0.1- 18% by weight Al ₂ O ₃₊ TiO ₂ 0 - 2% by weight ^Fe 2 ° 3 0 - -Z 10 wt. CaO 0 - 2 wt MgO 40 - 55 wt Ki 0 - 0.5 weight group used and this with a grain size of maximum 5 mm, preferably from 1 to 3 mm, is treated with dilute hydrochloric acid, the treatment being interrupted as soon as the undissolved residue has reached between 70-35% by weight based on the serpentine used. 2. The method according to claim I _1, characterized in that a serpentine is used as the starting material »of which at least 50 parts by weight, preferably 80 parts by weight, have a grain size between 1-3 mm. 609852/0749 3. The method according to claim 1 or 2, characterized in that »the treatment in boiling hydrochloric acid in
single or multi-stage extraction process is carried out over a period of Ϊ / 4 hour up to a total of 6 hours »preferably 1 hour. 4. The method according to any one of claims 1 to 3, characterized in that the residue obtained, e.g. Treatment ax fatty acid esters, siloxanes, silicones, ketenes » Naphthen, wax, bitumen or petroleum made hydrophobic will* 5. The method according to any one of claims 1 to 4, characterized marked »that the dried Matecia 1 of the residue ground to a grain size of 0-0.1 mm and divided into two fractions by air separation, namely one with a separation limit from 0 to 0.03 mm and a second with a separation limit of 0.03 to 0.1 mm. 609852/0749