CO-SYNTHESIS OF PHYLLOMINERALS WITH METALLIC PARTICLES AND PRODUCTS OBTAINED THERE-FROM

Abstract

The present invention relates to methods for producing mixtures comprising noble metal and phyllomineral, and compositions obtained from said methods.

Claims

1. A method comprising the steps of (a) provision of a phyllomineral source; (b) provision of a noble metal source; (c) combination of the phyllomineral source of step (a) with the noble metal source of step (b); and (d) optionally hydrothermal treatment of the mixture obtained at the end of step (c).

2. A method according to claim 1, wherein the phyllomineral is a non-swelling phyllomineral.

3. A method according to claim 1, wherein the said phyllomineral source is selected from the group consisting of a phyllomineral precursor, a phyllomineral and mixtures thereof, and wherein the said noble metal source is selected from the group consisting of a noble metal compound, a noble metal in its metallic state and mixtures thereof.

4. A method according to claim 1, wherein the phyllomineral of the said phyllomineral source is a single phyllomineral or a mixture of phyllominerals, and wherein the noble metal of the said noble metal source is a single noble metal or a mixture of noble metals.

5. A method according to claim 1, wherein the phyllomineral of the said phyllomineral source is selected from the group consisting of talc, mica, chlorite, kaolinite and mixtures thereof, and wherein the noble metal of the said noble metal source is selected from the group consisting of gold, palladium, platinum, iridium, ruthenium, rhodium, or mixtures thereof.

6. A method according to claim 1, wherein the said phyllomineral source is a combination of (i) an aqueous solution comprising a soluble metasilicate and/or metagermanate, optionally in combination with a carboxylate, and (ii) an aqueous solution comprising a metal salt.

7. A method according to claim 1, wherein the said noble metal source is an aqueous solution comprising a soluble noble metal salt.

8. A method according to claim 6, wherein the said soluble metasilicate and/or the said soluble metagermanate in step (a) are selected from the respective sodium or potassium salts, or mixtures thereof, and/or wherein the said optional carboxylate in step (a) is a metal carboxylate, the metal being selected from sodium or potassium, or mixtures thereof.

9. A method according to claim 6, wherein the said optional carboxylate in step (a) is selected from formate, acetate, propionate, butyrate, isobutyrate, valerate, isovalerate or a mixture thereof, and/or wherein the metal in the said soluble metal salt in step (a) is a divalent metal selected from magnesium, cobalt, zinc, copper, manganese, iron, nickel, chromium or mixtures thereof, for example wherein the said soluble metal salt is magnesium acetate.

10. A method according to claim 7, wherein the noble metal in the said soluble noble metal salt in step (b) is selected from gold, palladium, platinum, iridium, ruthenium, rhodium, or mixtures thereof.

11. A method according to claim 6, wherein the said combination step (c) is carried out by mixing the said noble metal source of step (b) with the said component (i) of the phyllomineral source of step (a) and the said component (ii) of the phyllomineral source of step (a) in any order.

12. A method according to claim 1, wherein the said hydrothermal treatment of step (d) is carried out by heating at a temperature between 100° C. and 600° C. for a duration of 10 minutes to 30 days, and wherein the heating is achieved by microwave heating, by convection heating, or combinations thereof.

13. A method according to claim 1, wherein the product obtained after the combination step (c) or after hydrothermal treatment step (d) is dried, washed and/or centrifiged.

14. A method according to claim 1, wherein the optional hydrothermal treatment is carried out as a batch process in an autoclave under autogeneous pressure.

15. A method according to claim 1, wherein the optional hydrothermal treatment is carried out as a continuous process under a pressure of 1 MPa or higher.

16. A particulate composition comprising a combination of phyllomineral with noble metal obtained according to claim 1.

17. A particulate composition according to claim 16, wherein the phyllomineral is a natural or synthetic phyllomineral selected from talc, mica, chlorite, kaolinite, or mixtures thereof, and/or wherein the said noble metal is selected from the group consisting of gold, palladium, platinum, iridium, ruthenium, rhodium, or mixtures thereof.

18. A particulate composition according to claim 16, wherein the said noble metal is in the form of nanoparticles intimately linked to the phyllomineral surface.

19. A particulate composition according to claim 18, wherein the said noble metal nanoparticles have an average particle diameter in the range of 1 nm to 100 nm, and wherein the said phyllomineral particles are platelets having a large diameter in the range of 10 nm to 1 mm.

20. A product comprising a composition of claim 16, where the product is a catalyst, a cosmetic, a pharmaceutical, or filler.

Description

SHORT DESCRIPTION OF THE FIGURES

[0024] The invention will be further illustrated by reference to the following figures:

[0025] FIG. 1 represents a field emission gun scanning electron microscopy (FEG-SEM) image of a synthetic talc (dark gray) comprising 10,000 ppm Au (white spots);

[0026] FIG. 2a represents a transmission electron microscopy (TEM) image of the surface of a synthetic talc (bright) comprising 10,000 ppm Au (black);

[0027] FIG. 2b represents the same TEM image as FIG. 2a with a larger scale.

[0028] It is understood that the following description and references to the figures concern exemplary embodiments of the present invention and shall not be limiting the scope of the claims.

DETAILED DESCRIPTION OF THE INVENTION

[0029] The present invention according to the appended claims provides for methods to produce novel particulate compositions comprising a particulate phyllomineral having noble metal nanoparticles intimately connected to the surfaces of the phyllomineral platelet particles. The exact nature of the connection between the noble metal and the phyllomineral is not known, but the relative arrangement of phyllominerals and noble metals may merely be observed by electron microscopy, as illustrated in FIG. 1 (FEG-SEM), and FIGS. 2a and 2b (TEM).

[0030] As used herein, FEG-SEM and TEM have been used to determine the sizes and dimensions according to methods known to the skilled person in the art, and as shown, for example in WO 2015/159006 A1 WO 2013/093376 A1.

[0031] Although not wishing to be bound by theory, it is believed that the noble metal nanoparticles preferably connect to the —(Si)OH-ends and —(Mg)OH-ends of the platelets.

[0032] In accordance with the present invention, the compositions comprise a larger proportion of phyllomineral and a lower proportion of noble metal. For example, the weight ratio of phyllomineral to noble metal may be in the range of 1:1 to 10.sup.6:1. As used herein, the amount of noble metal in the compositions in accordance with the invention is expressed as parts per million (ppm), wherein the ppm indicates the weight ratio of noble metal to phyllomineral.

[0033] The versatility of the methods of the present invention lies in that, on the one hand, the phyllomineral source may either be a phyllomineral or a phyllomineral precursor, such as e.g. an aqueous solution comprising a soluble metasilicate and/or metagermanate, optionally in combination with a carboxylate, and the noble metal source may either be a noble metal or a noble metal salt.

[0034] For example, the method may be carried out by combining a phyllomineral such as a particulate talc with a noble metal, such as gold nanoparticles.

[0035] For example, the method may be carried out by combining a phyllomineral precursor, such as an aqueous solution comprising a soluble metasilicate and/or metagermanate, optionally in combination with a carboxylate with a noble metal, such as gold nanoparticles.

[0036] For example, the method may be carried out by combining a phyllomineral such as a particulate talc with a noble metal precursor, such as a soluble gold salt.

[0037] For example, the method may be carried out by combining a phyllomineral precursor, such as an aqueous solution comprising a soluble metasilicate and/or metagermanate, optionally in combination with a carboxylate with a noble metal precursor, such as a soluble gold salt.

[0038] Furthermore, the versatility is further determined by the fact that the order of addition of the various components does not considerably affect the reaction and reaction products. Why the exact nature of the final product obtained may incur slight changes on the basis of the order of addition of components during the formation, all combinations lead to the products of the invention being formed.

[0039] It should be noted that the present invention may comprise any combination of the features and/or limitations referred to herein, except for combinations of such features which are mutually exclusive. The foregoing description is directed to particular embodiments of the present invention for the purpose of illustrating it. It will be apparent, however, to one skilled in the art, that many modifications and variations to the embodiments described herein are possible. All such modifications and variations are intended to be within the scope of the present invention, as defined in the appended claims.

EXAMPLES

Example 1

[0040] This Example uses an aqueous synthetic talc dispersion as a phyllomineral source and gold nanoparticles as a noble metal source.

[0041] In a beaker, 6.3 mL of a gold nanoparticles solution (0.05 mg/mL) was added to 32.6 g aqueous synthetic talc dispersion (corresponding to 1.5 g of dry talc). The obtained mixture was diluted with 150 mL of distilled water, mixed and sonicated for several minutes. Once well dispersed, the suspension was centrifuged at 9000 rpm during 1 h 30. At the end, the supernatant was perfectly clear and colourless and the residue of synthetic talc was reddish, indicating the presence of gold nanoparticles.

[0042] The theoretical loading comes to 0.315 mg gold for 1.5 g talc, corresponding to a loading of 210 ppm. Attempts to run the experiment at a theoretical loading of 3000 ppm or higher led to a red coloration of the supernatant after centrifugation, indicating that not all gold nanoparticles integrated into the talc.

Example 2

[0043] This Example uses hydrated sodium metasilicate and magnesium acetate as a phyllomineral source forming talc in situ, and chlorauric acid as a noble metal source, forming gold in situ.

[0044] 42.4 g (0.2 mol) sodium metasilicate pentahydrate was dissolved in 300 mL distilled water in a first beaker (A) under magnetic stirring and ultrasound. 103.5 g anhydrous sodium acetate was added. In a second beaker (B), 32.17 g (0.15 mol) magnesium acetate tetrahydrate was dissolved in 100 mL acetic acid 1M under magnetic stirring and ultrasound. 0.8 mL of a 10 mg/mL HAuCl.sub.4 trihydrate-solution was added to beaker (B). The content of beaker (B) was rapidly added to the content of beaker (A) with manual stirring to obtain a white suspension. The obtained aqueous suspension was treated in a hydrothermal reactor for 6 h at 300° C. under autogeneous pressure (85 bar). At the end of the hydrothermal treatment, a red gel was obtained, which was washed with distilled water several times. A red paste was obtained which may be dried in a desiccator, an oven (120° C.) or a centrifuge to obtain a violet particulate solid.

[0045] The theoretical loading comes to 4 mg gold for 18.96 g talc, corresponding to a loading of about 210 ppm. The experiment was repeated for theoretical loadings of 100 ppm, 500 ppm and 10000 ppm, each time giving a clear and colourless supernatant after centrifugation, indicating that all gold nanoparticles formed in situ had linked to the talc formed in situ.

Example 3

[0046] This Example uses hydrated sodium metasilicate and magnesium acetate as a phyllomineral source forming talc in situ, and a mixture of chlorauric acid and chloroplatinic acid as a noble metal source, forming gold and platinum in situ.

[0047] 42.4 g (0.2 mol) sodium metasilicate pentahydrate was dissolved in 300 mL distilled water in a first beaker (A) under magnetic stirring and ultrasound. 103.5 g anhydrous sodium acetate was added. In a second beaker (B), 32.17 g (0.15 mol) magnesium acetate tetrahydrate was dissolved in 100 mL acetic acid 1M under magnetic stirring and ultrasound. 1.90 mL of a 10 mg/mL HAuCl.sub.4 trihydrate-solution and 2.45 mL of a 10.25 mg/mL H.sub.2PtCl.sub.6 hexahydrate solution were added to beaker (B). The content of beaker (B) was rapidly added to the content of beaker (A) with manual stirring to obtain a white suspension. The obtained aqueous suspension was treated in a hydrothermal reactor for 6 h at 300° C. under autogeneous pressure (85 bar). At the end of the hydrothermal treatment, a grey gel was obtained, which was washed with distilled water several times.

[0048] The theoretical loading comes to 9.48 mg gold and 9.48 mg platinum for 18.96 g talc, corresponding to a loading of about 500 ppm for each of gold and platinum.

Example 4

[0049] This Example uses hydrated sodium metasilicate and magnesium acetate as a phyllomineral source forming talc in situ, and a mixture of chloroplatinic acid, sodium tetrachloropalladate(II) and ammonium hexachlororhodate(III) as a noble metal source, forming platinum, palladium and rhodium in situ.

[0050] 42.4 g (0.2 mol) sodium metasilicate pentahydrate was dissolved in 300 mL distilled water in a first beaker (A) under magnetic stirring and ultrasound. 103.5 g anhydrous sodium acetate was added. In a second beaker (B), 32.17 g (0.15 mol) magnesium acetate tetrahydrate was dissolved in 100 mL acetic acid 1M under magnetic stirring and ultrasound. 4.90 mL of a 10.25 mg/mL H.sub.2PtCl.sub.6 hexahydrate solution, 5.23 mL of a 10 mg/mL Cl.sub.4Na.sub.2Pd solution and 6.55 mL of a 10.39 mg/mL RhCl.sub.6(NH.sub.4).sub.3 solution were added to beaker (B). The content of beaker (B) was rapidly added to the content of beaker (A) with manual stirring to obtain a white suspension. The obtained aqueous suspension was treated in a hydrothermal reactor for 6 h at 300° C. under autogeneous pressure (85 bar). At the end of the hydrothermal treatment, a dark gel was obtained, which was washed with distilled water several times.

[0051] The theoretical loading comes to 18.96 mg platinum, 18.96 mg palladium and 18.96 mg rhodium for 18.96 g talc, corresponding to a loading of about 1000 ppm for each of platinum, palladium and rhodium.

Example 5

[0052] This Example uses hydrated sodium metasilicate and magnesium acetate as a phyllomineral source forming talc in situ, and gold nanoparticles as a noble metal source.

[0053] 42.4 g (0.2 mol) sodium metasilicate pentahydrate was dissolved in 300 mL distilled water in a first beaker (A) under magnetic stirring and ultrasound. 103.5 g anhydrous sodium acetate was added. In a second beaker (B), 32.17 g (0.15 mol) magnesium acetate tetrahydrate was dissolved in 100 mL acetic acid 1M under magnetic stirring and ultrasound. 80 mL of a gold nanoparticles solution (0.05 mg/mL) was added to beaker (B). During the mixture, the red solution of gold nanoparticles turns instantaneously to a deep blue/dark solution. The content of beaker (B) was rapidly added to the content of beaker (A) with manual stirring to obtain a white suspension. The obtained aqueous suspension was treated in a hydrothermal reactor for 6 h at 300° C. under autogenous pressure. At the end of the hydrothermal treatment, a red gel was obtained, which was washed with distilled water several times and then centrifuged to obtain a blue-violet product and a clear and colourless supernatant.

[0054] The theoretical loading comes to 4 mg gold for 18.96 g talc, corresponding to a loading of about 210 ppm.

Example 6

[0055] This Example uses an aqueous synthetic talc dispersion as a phyllomineral source and chlorauric acid as a noble metal source, forming gold in situ.

[0056] In a beaker, 43.48 g aqueous synthetic talc dispersion (corresponding to 2 g dry talc) was added to 84 μL of a HAuCl.sub.4 trihydrate solution (10 mg/mL). Distilled water was added up to 150 mL. The suspension was then mixed under magnetic stirring and sonication. Once well dispersed, the mixture was placed in an autoclave at 300° C. and 86 bars during 1 hour. At the end of the hydrothermal treatment, a red paste was obtained and centrifuged to recover the product.

[0057] The theoretical loading comes to 4 mg gold for 18.96 g talc, corresponding to a loading of about 210 ppm.

Example 7

[0058] This example uses natural talc as a phyllomineral source and chlorauric acid as a noble metal source, forming gold in situ.

[0059] In a beaker, 2 g dry natural talc (white powder) was added to 4 mL of a HAuCl.sub.4 trihydrate solution (10 mg/mL). Distilled water was added up to 20 mL. The suspension was mixed under magnetic stirring and sonication. The mixture was then placed in an autoclave at 300° C. and 86 bars during 6 hours. At the end of the hydrothermal treatment, a red suspension was obtained and placed in an oven at 120° C. to dry the product.

[0060] The theoretical loading comes to 20 mg gold for 2 g talc, corresponding to a loading of about 10000 ppm.

Example 8

[0061] This example uses natural talc as a phyllomineral source and chlorauric acid as a noble metal source, forming gold in situ.

[0062] The preparation is the same that the example 2. The aqueous suspension obtained after mixing the phyllomineral and gold sources is not hydrothermally treated, but kept at room temperature. The suspension becomes reddish as soon as the day after and becomes more and more reddish with time, indicating that there is reduction of gold and synthetization of gold particles.