DD220586A1 - PROCESS FOR THE PREPARATION OF KENYAITE - Google Patents

Abstract

The invention relates to a process for the preparation of kenyaite, a water-insoluble sodium silicate with a layered structure. The preparation is carried out from magadiite or its precursors containing aqueous alkaline mixtures by aging reactions at 350 to 500 K. Kenyait can be used as an ion exchanger, adsorbent, fuel, pigment, Traeger for active ingredient and other molecules, catalyst and catalyst carrier.

Description

- i

Title of the invention . Process for the preparation of kenyaite

Field of application of the invention :

The invention relates to a process for the preparation of kenyaite, a water-insoluble sodium polysilicate with. Layer structure. Kenyaite can be used as an ion exchanger, adsorbent, filler, pigment, carrier for drugs and other molecules, catalyst and catalyst carrier.

Characteristic of the known technical solutions

Kenyaite comes as an aluminum-free sodium silicate hydrate with a layered structure and composition

Na ₂ O 22 SiO ₂ . 7H ₂ O

in front. Kenyaite has the X-ray _T - listed in Table 1 . ' diffraction data on.

According to SCHTi / ISGBE (Dissertation IuILU Halle 1979) the kenyaite crystallizes from the ternary system Na ₂ O - SiO ₂ H ₂ O. As a Si0 ₂ raw material he used commercial silica sols (about 30 % SiO ₂ , -NaOH stabilized) on. Batch gels having a composition of 4 moles of SiO 2/1 mole of Na ₂ O / 30 moles of H ₂ O from which Kenyaite is obtained are prepared by drilling by adding NaOH solutions to the silica sol at room temperature. After a crystallization time of 4 to 10 days, kenyaite is obtained from these gels at 400 to 423 K. ,

Table 1 compares the typical values of the X-ray diffraction lines of synthetic (SCHWIGSR) and natural kenyaite (BüGSTER).

, '-9.Jiiii188M142O1 (O

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Disadvantages of the production of kenyaite according to the process described by SCHWISGEH are the low space-time yields. Furthermore, in the given raw material choice, the production of the kenyaite is no longer possible with even slight changes in the reaction conditions (compositions of the batch gel, crystallization temperature, crystallization time). Thus, at crystallization temperatures of 373 °, a product with a different structure results, as does the increase in SiO 2 / Na 2 O mole ratios. When the crystallization time is extended to more than 10 d, quartz is obtained. According to the possibility given by SCHWIlGEE of producing kenyaite, there is a great uncertainty regarding the product purity of: kenya-ts.

Object of the invention ..

The object of the invention is to provide a method for synthetic

- - * '

Preparation of the naturally occurring layered silicate

Kenyait to find. , ':',. , V-.

Explanation of the essence of the invention

The invention is based on the technical object of enabling Kenyaite formation by targeted process design. ,

According to the invention, the object of producing kenyaite from magadiite or its precursors containing aqueous alkaline mixtures is achieved in that these mixtures are aged at temperatures of from 380 to 4-50 K until kenyaite formation.

The molar composition of such mixtures should be in the ranges. 3 bis.-15 Mpl SiO _2/2 mol of NaOH, 30 to 200 moles of H ₂ O, preferably 4 to 6 mol of SiO _2/2 mol of NaOH / 30 to 75 mole Η ^, Ο vary. In order to prepare such mixtures, the magadiite is stirred into aqueous alkaline solutions, taking into account its composition.

It is essential that also reaction-nsmi loops are suitable for this process, which do not yet contain crystalline Magadiitanteile, but these are formed intermediately in the course of the reaction and degraded again. Thus, it is possible to carry out the kenyaite formation in a reaction stage without intermittently carrying out a separation of the solid phase. ,

A particularly preferred temperature range in which kenyaite forms comprises 390 to 420K.

Advantageously, but not necessarily, the kenyaite formation can be carried out in the agitated reaction mixtures according to the process of the invention The agitation can be achieved by stirring in a stationary vessel or also by movement of the reaction vessels themselves.

An acceleration of the reaction is achieved by addition of 0.5 to 10% by mass of zirconium to the magadiite or. whose precursors containing aqueous alkaline mixture achieved. The target product, by subjecting it to self-dissolving and rearrangement reactions, acts as a basic building block supplier for the magadiite formation process. The addition of target product to the reaction mixture is therefore not comparable to the effect of a germ which triggers crystallization or condensation in a saturated or supersaturated solution or vapor phase.

The products obtained by the process according to the invention are identifiable by the characteristic X-ray diffraction lines and IR absorption bands given in Tables 2 and 3.

_ Zj. -

Embodiments - -

Example 1 ."." :. '-. ,

10 g of a Na magadiite; of the composition 13 »5 SiCU. 1 Na ₂ O HPO 10.5 are suspended in an aqueous NaOH solution so that a total composition of 9 moles of SiO ₂ / Na ₂ O 1 mol / 130 mol of H ₂ O results. , This mixture is subjected to the aging temperature of 414 K under autogenous pressure.

After an aging period of 7 days, kenyaite is detectable with the typical X-ray diffraction lines listed in Table 2.

Example 2. '

A mixture containing precursors suitable for magadiide production is prepared by adding 80 ml of a Na-stabilized crescent sol (about 30% by weight of SiO ₂ ). and 9 »A'g NaOH, dissolved in 11.5 S water. The result is a molar composition of the mixture of 4 mol.: ... SiO ₂ ZI mol Na ₂ O / 35.4 mol H ₂ O. As aging vessels G-las or steel ampoules are used. Magadiite is formed intermediately after 3 to 4 days under the conditions of aging under 403 ° C and the kayaite is completely aged after 5 to 7 days under the conditions indicated The chemical composition of the resulting air-dry product is 19 mol SiO _2, 1 mol Na ₂ O, 10.0 mol H ₂ O..

Example 3 · - \ '

A 320 g magadiite (14.2 SiO ₂ .1 Na ₂ O. 8.5 E ₂ O) containing mixture of. Composition 5 mol of SiO _2/2 mol of ITaOHyf50 mol H ₂ O is aged in a 5 1 laboratory autoclave with stirring at 428 K under autogenous pressure for 72 h. The filtered, washed and dried product "has the typical X-ray diffraction lines listed in Table 2, which characterize it as Eenyaite.

Table 1.

Characteristic X-ray diffraction lines of the Kenyaits (literature values).

si. ugster S w h 1 he g Kenyait / / G7 / / - / / Q / .A O? J- r% j .19,68 100 ¹ 19.23 62 9,925   50 9,81. 23 6,620 .5 6,52. .7 5,637 7 , 5.61 5 5,142 12  5.06 10: 4,965. 35 4.93 17 4,689 28 4.67 19 4,471   5 , 4,46 ' ,: 5 ' ^: · 3,945 10 3.93 .11 3.86 7 3,638 20 3.63 18 3,525 22 3.51 19 3.428 , 3.42 , 100. 3,320 45 3.30 58 3,198 55 - 3.18 ' ⁶ 5 2.98 5 2,943 14 2.92 13th  2,827 12 2,814. 8th 2, §16 5 2,343 7 2.338. 5   2,243 5

1,880 3

1,824 15

Table 2; , , ·.

Cfc Characteristic values of the X-ray diffractogram of the produced kenyaite product

Lattice spacing , intensity rij 19.21 60 9.80 - '25 ^: . '. 5.62 6 5.05. 11 4.93 17   4:43. ' ' 21 3.93 10 3.87 "; ''. '5 3.62 .18 3.51 22 <' 3.42 100 3.28 62 ^; 3.18 70th , 2.98 5 -2.928 , 13 2,819 8th 2,340 5 '..   2,241 5 1,825 17

Table 3:

Location of the typical IR absorption bands of the obtained kenyaite. ,

assignment

kenyaite '

SiO deformation vibration

¹ SiO-Si

405 415

450 49O

548 580

SiO-valence oscillation

620

660 79.0 805 820

Si-OH

960

SiO-7al oscillation

1090 1180 1205 1240

as 1635 , t) H ₂ O , 2940 3450 , H ₂ O 3670

The assignment of the vibration bands is carried out according to 5 ¹ HIEIAT-, J, J .; L30NABD, A., BARAK, N: Bull. Soc. Chim. France 1 (1963)

Claims (5)

Invention san s prüciie 1. A process for the preparation of eenyaite from magadiite or its precursors containing aqueous alkaline mixtures, , .ge ke η η ζ eic h η etdadurch, that _: these mixtures b.ei temperatures of 350 to 500 K are aged until Kenyaitbildung. 2. Procedure according to point -1 ,,. ' ^: ge 'k. e η η ζ calibration η e _t ^thereby; that mixtures of the composition of 3 to 15 mol.Si0 _2/2 moles of NaOH / 30-200 moles of H ₂ O are used, 3. Method nachi; Point 1. and 2. .., characterized in that the Eenyaitbildungsprozeß is performed in a reaction stage. 4 ·, procedures according to point 1. to 3.,. ', characterized in that the reaction mixture is agitated. , ". 5. Method according to items 1 to 4, / ge ke, η ζ eich η etdadurc ' h,. that der.Reaktionsmischung 0.5 to 10 Ma # -% target product, based on. the Ifeststoffgehalt is added. '^; · \ . , ^: