Particulate carbon material comprising elemental silver and elemental ruthenium

Abstract

The catalyst has an average particle size (d50) in the range of 0.5 to 500 μm, a pore volume in the range of 0.5 to 10 mL / g, and a pore size in the range of 200 to 2000 m 2 / g range of BET surface area.

Description

[Technical field]

[0001] The present invention relates to a particulate carbon material comprising elemental silver and elemental ruthenium, and an efficient method for its preparation.

[0002] WO 2021 / 084140(A2) discloses a method for preparing a particulate support material comprising elemental silver and elemental ruthenium, which can be used as an additive for the antibacterial treatment of a wide variety of materials and substances.

[0003] The object of the present invention was to provide a highly antibacterial active material based on a carbon material with elemental silver and elemental ruthenium.

[0004] The objective is to provide a polymer having elemental silver and elemental ruthenium, an average particle size (d50) in the range of 0.5 to 500 μm, a pore volume in the range of 0.5 to 10 mL / g, and a pore size of 200 to 2,000 m 2 This can be achieved by providing a particulate carbon material having a BET surface area in the range of 1000 to 1500 nm / g (hereinafter also referred to as "particulate carbon material comprising elemental silver and elemental ruthenium" for short). The weight proportion of silver+ruthenium formed by elemental silver and elemental ruthenium can be in the range of, for example, 0.1 to 50% by weight (% based on weight), with a weight ratio of silver to ruthenium in the range of, for example, 1 to 2,000 parts by weight silver to 1 part by weight ruthenium.

[0005] The particulate carbon material according to the invention comprising elemental silver and elemental ruthenium essentially consists of carbon particles comprising elemental silver and elemental ruthenium, i.e. it comprises, for example, carbon particles comprising elemental silver and elemental ruthenium in a proportion ranging from 95 to 100% by weight, in particular in a proportion of 100% by weight. A proportion that may not exceed 5% by weight may be constituted by carbon particles not comprising precious metals. In other words, the particulate carbon material according to the invention comprising elemental silver and elemental ruthenium may in particular comprise 95 to 100% by weight of carbon particles comprising elemental silver and elemental ruthenium and 0 to 5% by weight of carbon particles not comprising precious metals, the weight percentages adding up to 100% by weight.

[0006] The terms "particulate carbon material" and "carbon particles" are used herein. The particulate carbon material or carbon particles are not carbon nanotubes or carbon nanofibers. Rather, they can be carbon particles, in particular activated carbon particles, i.e., carbon particles with elemental silver and elemental ruthenium can be carbon particles with elemental silver and elemental ruthenium, in particular activated carbon particles with elemental silver and elemental ruthenium, and carbon particles without precious metals can be carbon particles without precious metals, in particular activated carbon particles without precious metals.

[0007] The term "average particle size" as used herein means the volume-average primary particle size (d50) measurable by laser diffraction. In this case, what is known as the equivalent circular area diameter (ECAD) can be advantageously used as a measure of particle size (see RENLIANG XU ET AL: "Comparison of sizing small particles using different technologies," POWDER TECHNOLOGY, ELSEVIER, BASEL (CH), vol. 132, no. 2-3, June 24, 2003 (06-24-2003), pages 145-153). Laser diffraction measurements can be performed according to a wet measurement process using a corresponding particle size measuring device, for example, a Mastersizer 3000 or Mastersizer 2000 from Malvern Instruments. In the wet measurement process, the particulate sample can be dispersed in ethanol by ultrasound as part of the sample preparation.

[0008] The term "pore volume" is used herein.Pore volume can be measured by mercury porosimetry according to DIN ISO 15901-1:2016 (sample mass 30 mg; surface tension of mercury 0.48 N / m; contact angle of mercury 141.3°; instrument: Porotec Pascal 140+440; measurement process: scan; initial filling pressure 0.0128 MPa; dilatometer: powder, small volume; sample preparation: 8 hours at 110°C under vacuum).

[0009] The term "BET surface" as used herein refers to a specific surface area that can be determined by BET measurements according to DIN ISO 9277:2014-01 (according to chapter 6.3.1, static-volumetric measurement process, gas used: nitrogen).

[0010] The present invention also relates to a method for preparing such a particulate carbon material with elemental silver and elemental ruthenium. From another point of view, the process can also be understood as a method for providing a particulate carbon material with elemental silver and elemental ruthenium. In the method according to the invention, the particulate carbon material according to the invention with elemental silver and elemental ruthenium can be obtained by reducing at least one silver precursor and at least one ruthenium precursor in the presence of carbon particles, in particular activated carbon particles, suspended in water, then separating the solid formed in this process from the aqueous phase, optionally washing the separated solid with water, and optionally drying the solid. Thus, the method according to the invention comprises the steps of reducing at least one silver precursor and at least one ruthenium precursor in the presence of carbon particles, in particular activated carbon particles, suspended in water, separating the solid formed in the course of the reduction process from the aqueous phase, optionally washing the separated solid with water, and optionally drying the separated and optionally washed solid. During the reduction process, the silver and ruthenium precursors can be reduced successively or preferably simultaneously.

[0011] The silver and ruthenium precursors referred to herein are silver and ruthenium compounds. Elemental silver or ruthenium can be prepared by reduction from silver and ruthenium compounds, respectively.

[0012] Examples of suitable silver compounds include silver acetate, silver sulfate, and preferably silver nitrate.

[0013] Examples of suitable ruthenium compounds include ruthenium oxalate, ruthenium acetate and especially ruthenium nitrosyl nitrate.

[0014] It is particularly preferred to use a combination of silver nitrate and ruthenium nitrosyl nitrate as the precursor compound combination in the method according to the invention.

[0015] The activated carbon particles used during the reduction process are in particular activated carbon particles having a mean particle size (d50) in the range of 0.5-400 μm, a pore volume in the range of 0.5-10 mL / g and a BET surface in the range of 300-3,000 m2 / g. The activated carbon particles can be of various types, for example activated carbon produced by pyrolysis or derived from natural sources, such as, in particular, wood, peat, fruit skins, walnut shells, apricot shells, date skins, coconut shells. They can be activated carbons that constitute a combustion behavior characterized by a weight loss of 50% within 25 to 28 minutes, the weight loss being measured by TGA (thermogravimetric analysis) of a small (about 8-16 mg) powder sample of the corresponding activated carbon in an air atmosphere, at a starting temperature of 200 °C and a heating rate of 20 °C / min. A 100% starting weight of about 8-16 mg is measured at a starting temperature of 200 °C. Activated carbon made from wood or peat is an example of activated carbon with such burning behavior. Examples include commercially available types of activated carbon such as Norit® SX Plus manufactured by Cabot Corporation (Alpharetta, Georgia), and Acticarbone® 3S and Acticarbone® CXV manufactured by Calgon Carbon Corporation (Moon Township, Pennsylvania). Other activated carbons have poorer burning behavior that can be characterized by a 50% weight loss after more than 28 minutes, for example, after more than 28 minutes to 35 minutes, measured under the same conditions by the same TGA measurement process as above. If the 50% weight loss continues for more than 35 minutes, the temperature is maintained at 800°C and not increased beyond this level. Activated carbon derived from coconut shell is an example of a type of activated carbon with poor burning behavior. Examples include commercially available activated carbon types such as Desorex® C33 spezial and Carbopal® CCP 90 FF spezial, both manufactured by Donau Carbon GmbH (Frankfurt, Germany).

[0016] The reduction carried out in the method according to the present invention can be carried out either using formic acid at an acidic pH in the range of 1 to 4, preferably 1 to 2, and at a temperature in the range of 70 to 100°C, preferably 70 to 90°C, or using hydrazine at an acidic pH in the range of 1 to 4, preferably 1 to 2, and at a temperature in the range of 10 to 40°C, preferably 15 to 35°C, or using a reducing agent selected from the group consisting of sodium borohydride, hydrazine, hypophosphites and formates at a basic pH in the range of 9 to 14, preferably 9 to 12, and at a temperature in the range of 10 to 40°C, preferably 15 to 35°C.

[0017] Hydrazine can be used as such, but preferably as hydrazine hydrate with a hydrazine content in the range of 30-65% by weight. When operating at basic pH, hydrazine can also be used as a hydrazinium salt, for example hydrazinium sulfate. Preferably, the operation is performed with hydrazine hydrate.

[0018] Hypophosphites and formates are mentioned herein. These include salts, especially alkali metal salts, alkaline earth salts and ammonium salts (NH 4 Salts). Sodium hypophosphite and potassium hypophosphite, or sodium formate and potassium formate are preferred.

[0019] In the method according to the present invention, the reducing agent is used in an amount equal to or more than the stoichiometrically required amount in order to completely reduce the silver precursor and the ruthenium precursor to elemental silver and elemental ruthenium, but preferably in an amount equal to or less than 110% (hydrazine as the reducing agent) or equal to or less than 200% (formic acid, sodium borohydride, hypophosphite or formate as the reducing agent) of the stoichiometrically required amount. Using the example of hydrazine, this means that 1 mole of the reducing agent hydrazine can provide 4 moles of electrons with a reducing effect, and therefore 1 mole of N in the reduction 2 So, for example, 1 mole of Ag + The reduction of requires 0.25 mol of hydrazine and 1 mol of Ru. 3+The reduction of requires 0.75 moles of hydrazine.

[0020] Four embodiments of the method according to the invention for preparing the particulate carbon material according to the invention comprising elemental silver and elemental ruthenium are disclosed below.

[0021] In a first preferred embodiment, the preparation method according to the invention comprises the steps of: (1a) providing an aqueous suspension comprising water, carbon particles, in particular activated carbon particles, at least one silver precursor and at least one ruthenium precursor; (2a) contacting the aqueous suspension with formic acid at a pH in the range of 1 to 4 and at a temperature in the range of 70 to 100° C. or with hydrazine at a pH in the range of 1 to 4 and at a temperature in the range of 10 to 40° C.; (3) separating the formed solids from the aqueous phase; (4) optionally washing the separated solids with water; and (5) Optionally, including the subsequent step of drying the solids.

[0022] The order of steps (1a) to (5) refers to consecutive steps, which can be directly successive steps without intermediate steps.

[0023] In step (1a) of a first embodiment of the method according to the invention, an aqueous suspension is provided comprising water, carbon particles, in particular activated carbon particles, at least one silver precursor and at least one ruthenium precursor.

[0024] The aqueous suspension can be prepared by adding carbon particles, in particular activated carbon particles, to an aqueous solution of at least one silver precursor and at least one ruthenium precursor and suspending them therein.

[0025] However, it is preferred to operate in such a way that the silver precursor and the ruthenium precursor, preferably in each case as aqueous solutions, are added simultaneously or in any order (overlapping with a time delay, alternating or successively) to the initially charged aqueous suspension of carbon particles, in particular activated carbon particles. It is particularly preferred that aqueous solutions of both precursors (at least one silver precursor and at least one ruthenium precursor) are added to the initially charged aqueous suspension of carbon particles, in particular activated carbon particles. The addition is preferably carried out slowly, for example over 2 hours or more, for example from 3 to 5 hours.

[0026] Generally, mixing is effected during and also after the addition, for example by stirring. Mixing after the addition may conveniently be effected for a period of, for example, from 8 to 120 hours, in particular from 24 to 120 hours.

[0027] The addition and mixing process can be carried out at elevated temperatures, for example in the range of 60-90° C. It can also be expedient to carry out the mixing at a pH in the aqueous suspension range typical for the following step (2a), and for this purpose suitable chemicals can be added to adjust the pH accordingly.

[0028] The weight proportion of carbon particles, in particular activated carbon particles, of the aqueous suspension provided in step (1a) of the first embodiment of the method according to the invention can be, for example, in the range of 5 to 30% by mass.

[0029] The weight percentage of silver in the aqueous suspension provided in step (1a) of the first embodiment of the method according to the invention can be, for example, in the range of 0.01 to 2.5% by weight, while the weight percentage of ruthenium can be, for example, in the range of 0.01 to 0.13% by weight. The aqueous suspension provided in step (1a) of the first embodiment of the method according to the invention is, for example, characterized by a weight ratio in the range of 1 to 2,000 parts by weight of silver to 1 part by weight of ruthenium, generally with a strong predominance of silver. This weight ratio of silver to ruthenium is also found in the product obtained after completion of step (5).

[0030] Besides the carbon particles, in particular activated carbon particles, and the precious metal precursor, the aqueous suspension provided in step (1a) of the first embodiment of the method according to the invention generally only comprises water and optionally chemicals used to adjust the pH.

[0031] In step (2a) of the first embodiment of the method according to the invention, the aqueous suspension provided in step (1a) is contacted with formic acid at a pH in the range of 1 to 4, preferably 1 to 2, and at a temperature in the range of 70 to 100 ° C, preferably 70 to 90 ° C, or with hydrazine at a pH in the range of 1 to 4, preferably 1 to 2, and at a temperature in the range of 10 to 40 ° C, preferably 15 to 35 ° C. If necessary, in this case, the corresponding pH and the corresponding temperature of the aqueous suspension can be adjusted first. The acidic pH can be adjusted, for example, using acetic acid. As mentioned above, formic acid or hydrazine is used in an amount more than the stoichiometrically required amount in order to completely reduce the silver precursor and the ruthenium precursor to elemental silver and elemental ruthenium, respectively. It is preferred to operate in such a way that formic acid is added to the aqueous suspension in concentrated form or in the form of an aqueous solution, for example of 80% by weight to <100% by weight, or hydrazine is added to the aqueous suspension either on its own or diluted with water, for example with a hydrazine concentration in the range of 65% by weight to <100% by weight. The addition is preferably carried out slowly, for example over 2 hours or more, for example 3 to 5 hours. Generally, mixing is carried out during the addition process and also after the addition process, for example by stirring, for example over a period of 2 to 24 hours, in particular 4 to 8 hours.

[0032] In a second particularly preferred embodiment, the preparation process according to the invention comprises: (1b) providing an aqueous suspension comprising water, carbon particles, in particular activated carbon particles, at least one silver precursor and at least one ruthenium precursor; (2b) contacting the aqueous suspension with a reducing agent selected from the group consisting of sodium borohydride, hydrazine, hypophosphites and formates at a pH in the range of 9 to 14 and a temperature in the range of 10 to 40° C.; (3) separating the formed solids from the aqueous phase; (4) optionally washing the separated solids with water; and (5) Optionally, including the subsequent step of drying the solids.

[0033] The order of steps (1b) to (5) refers to consecutive steps, which can be directly successive steps without intermediate steps.

[0034] Step (1b) of the second embodiment of the process according to the invention does not differ from step (1a) of the first embodiment of the process according to the invention or is carried out analogously to step (1a) and in this respect reference is made to the above explanations regarding step (1a), with reference only to point out that it may also be convenient here to carry out the mixing at a pH of the aqueous suspension which is in the pH range prevalent in the subsequent step (here (2b)), for which purpose suitable chemicals can be added to adjust the pH accordingly.

[0035] It is particularly advantageous in step (1b) to operate with activated carbon having an essentially alkaline pH, for example with Ceca 2SW activated carbon from Chemviron.

[0036] In step (2b) of the second embodiment of the method according to the invention, the aqueous suspension provided in step (1b) is contacted with a reducing agent selected from the group consisting of sodium borohydride, hydrazine, hypophosphites and formates at a pH in the range of 9 to 14, preferably 9 to 12, and at a temperature in the range of 10 to 40°C, preferably 15 to 35°C. If necessary, in this case the corresponding pH and the corresponding temperature of the aqueous suspension can be adjusted first. The alkaline pH can be adjusted using a strong base, in particular an alkali hydroxide, in particular sodium hydroxide or potassium hydroxide. As mentioned above, the reducing agent is used in an amount greater than or equal to the stoichiometrically necessary to completely reduce the silver and ruthenium precursors to elemental silver and elemental ruthenium, respectively. It is preferred to operate in such a way that the reducing agent is added to the aqueous suspension in the form of an aqueous solution. The addition is preferably carried out slowly, for example over 2 hours or more, for example over 3 to 5 hours. Generally, mixing is carried out during and also after the addition, for example by stirring, for example over a period of 2 to 24 hours, in particular 4 to 8 hours.

[0037] In a third embodiment, the preparation method according to the invention comprises: (1c) providing an aqueous suspension having a pH in the range of 9 to 14, comprising water, carbon particles, in particular activated carbon particles, and a reducing agent selected from the group consisting of sodium borohydride, hydrazine, hypophosphites and formates; (2c) contacting the aqueous suspension at a pH in the range of 9 to 14 and at a temperature in the range of 10 to 40° C. with (i) an aqueous solution comprising at least one silver precursor and at least one ruthenium precursor, or (ii) an aqueous solution comprising at least one silver precursor and then an aqueous solution comprising at least one ruthenium precursor, or (iii) an aqueous solution comprising at least one ruthenium precursor and then an aqueous solution comprising at least one silver precursor; (3) separating the formed solids from the aqueous phase; (4) optionally washing the separated solids with water; and (5) Optionally, including the subsequent step of drying the solids.

[0038] The order of steps (1c) to (5) refers to consecutive steps, which can be directly successive steps without intermediate steps.

[0039] In step (1c) of the third embodiment of the process according to the invention, an aqueous suspension is provided, having a pH in the range of 9 to 14, preferably 9 to 12, and comprising water, carbon particles, in particular activated carbon particles, and a reducing agent selected from the group consisting of sodium borohydride, hydrazine, hypophosphites and formates. The aqueous suspension can be prepared by adding the carbon particles, in particular activated carbon particles, to an aqueous solution of the reducing agent and suspending them therein. However, it is preferred to operate in such a way that the reducing agent is added, preferably as an aqueous solution, to the initially charged aqueous suspension of the carbon particles, in particular activated carbon particles. The alkaline pH can be adjusted using a strong base, in particular an alkali hydroxide, in particular sodium hydroxide or potassium hydroxide. Generally, mixing is carried out during and also after the addition, for example by stirring, for example for 1 to 2 hours.

[0040] The weight proportion of carbon particles, in particular activated carbon particles, of the aqueous suspension provided in step (1c) of the third embodiment of the process according to the invention can be, for example, in the range of 5 to 30 mass %.

[0041] The weight proportion of reducing agent in the aqueous suspension provided in step (1c) of the third embodiment of the process according to the invention may, for example, be in the range of 0.5 to 10% by weight.

[0042] Besides the carbon particles, in particular activated carbon particles, and the reducing agent, the aqueous suspension provided in step (1c) of the third embodiment of the process according to the invention generally only comprises water and optionally a base used to adjust the pH.

[0043] It is particularly advantageous in step (1c) to operate with activated carbon having an essentially alkaline pH, for example with Ceca 2SW activated carbon from Chemviron.

[0044] In step (2c) of the third embodiment of the method according to the invention, the aqueous suspension provided in step (1c) is contacted at a pH ranging from 9 to 14, preferably from 9 to 12, and at a temperature ranging from 10 to 40° C., preferably from 15 to 35° C. with (i) an aqueous solution comprising at least one silver precursor and at least one ruthenium precursor, or (ii) an aqueous solution comprising at least one silver precursor and then with an aqueous solution comprising at least one ruthenium precursor, or (iii) an aqueous solution comprising at least one ruthenium precursor and then with an aqueous solution comprising at least one ruthenium precursor. As described above, a single reducing agent is used in an amount greater than or equal to the stoichiometrically necessary to completely reduce the silver and ruthenium precursors to elemental silver and elemental ruthenium, respectively. It is preferable to operate according to variant (i).

[0045] The weight proportion of precious metals, consisting of silver and / or ruthenium, of the aqueous precious metal precursor solution used according to variants (i), (ii) or (iii) in step (1c) of the third embodiment of the method according to the invention can be, for example, in the range of 1 to 40% by weight. For example, a weight ratio in the range of 1 to 2,000 parts by weight of silver to 1 part by weight of ruthenium is used, with a significant predominance of silver as a rule. This weight ratio of silver to ruthenium is also found in the product obtained after completion of step (5).

[0046] Typically, mixing is carried out during and also after the addition, for example by stirring, for example for a period of from 2 to 24 hours, in particular from 4 to 8 hours.

[0047] In a fourth embodiment, the preparation method according to the invention comprises: (1d) providing an aqueous suspension having a pH in the range of 1 to 4, comprising water, carbon particles, in particular activated carbon particles, and formic acid or hydrazine; (2d) contacting the aqueous suspension at a pH in the range of 1 to 4 and at a temperature in the range of 70 to 100° C. (in the case of formic acid as the reducing agent) or at a temperature in the range of 10 to 40° C. (in the case of hydrazine as the reducing agent), with (i) an aqueous solution comprising at least one silver precursor and at least one ruthenium precursor, or (ii) an aqueous solution comprising at least one silver precursor and then an aqueous solution comprising at least one ruthenium precursor, or (iii) an aqueous solution comprising at least one ruthenium precursor and then an aqueous solution comprising at least one silver precursor; (3) separating the formed solids from the aqueous phase; (4) optionally washing the separated solids with water; and (5) Optionally, including the subsequent step of drying the solids.

[0048] The sequence of steps (1d) to (5) refers to a continuous process, which can be directly successive steps without intermediate steps.

[0049] In step (1d) of the fourth embodiment of the process according to the invention, an aqueous suspension is provided comprising water, carbon particles, in particular activated carbon particles, and formic acid or hydrazine, having a pH in the range of 1 to 4, preferably 1 to 2.

[0050] The aqueous suspension can be prepared by adding the carbon particles, in particular activated carbon particles, to an aqueous solution of formic acid or hydrazine and suspending them therein. However, it is preferred to operate in such a way that the formic acid or hydrazine, preferably as an aqueous solution, is added to the initially charged aqueous suspension of the carbon particles, in particular activated carbon particles. The acidic pH can be adjusted, for example, using acetic acid. Generally, mixing is performed during and also after the addition, for example by stirring, for example for 1 to 2 hours.

[0051] The weight proportion of carbon particles, in particular activated carbon particles, of the aqueous suspension provided in step (1d) of the fourth embodiment of the process according to the invention can be, for example, in the range from 5 to 30% by mass.

[0052] The weight proportion of formic acid or hydrazine in the aqueous suspension provided in step (1d) of the fourth embodiment of the process according to the invention can be, for example, in the range of 0.5 to 10% by weight.

[0053] In addition to the carbon particles, in particular activated carbon particles, and formic acid or hydrazine, the aqueous suspension provided in step (1d) of the fourth embodiment of the process according to the invention generally only comprises water and optionally an acid used to adjust the pH.

[0054] In step (2d) of the fourth embodiment of the method according to the invention, the aqueous suspension provided in step (1d) is contacted with (i) an aqueous solution comprising at least one silver precursor and at least one ruthenium precursor, or (ii) an aqueous solution comprising at least one silver precursor and then an aqueous solution comprising at least one ruthenium precursor, or (iii) an aqueous solution comprising at least one ruthenium precursor and then an aqueous solution comprising at least one silver precursor, at a pH in the range of 1 to 4, preferably 1 to 2, and a temperature in the range of 70 to 100 ° C, preferably 70 to 90 ° C, in the case of formic acid as reducing agent, or at a pH in the range of 1 to 4, preferably 1 to 2, and a temperature in the range of 10 to 40 ° C, preferably 15 to 35 ° C, in the case of hydrazine as reducing agent. In this case, as described above, formic acid or hydrazine is used in an amount more than stoichiometrically necessary to completely reduce the silver precursor and the ruthenium precursor to elemental silver and elemental ruthenium, respectively. It is preferable to operate according to variant (i).

[0055] The weight proportion of precious metals, consisting of silver and / or ruthenium, of the aqueous precious metal precursor solution used according to variants (i), (ii) or (iii) in step (1d) of the fourth embodiment of the method according to the invention can be, for example, in the range of 1 to 36% by weight. For example, a weight ratio in the range of 1 to 2,000 parts by weight of silver to 1 part by weight of ruthenium is used, with a significant predominance of silver as a rule. This weight ratio of silver to ruthenium is also found in the product obtained after completion of step (5).

[0056] Typically, mixing is carried out during and also after the addition, for example by stirring, for example for a period of from 2 to 24 hours, in particular from 4 to 8 hours.

[0057] Steps (3) to (5) are the same in all four embodiments of the method according to the invention.

[0058] In step (3), the solids formed in each of steps (2a), (2b), (2c) and (2d) are separated from the aqueous phase. Examples of solid-liquid separation methods suitable for this purpose include methods known to those skilled in the art, such as decantation, squeezing, filtration, suction filtration, centrifugation, or combinations thereof.

[0059] Step (4) of the process according to the invention is an optional but generally convenient step in which the solid separated in step (3) can be washed with water to remove water-soluble components. Washing can be carried out, for example, on a Nutsche filter.

[0060] Step (5) of the process according to the invention is an optional but generally advantageous step in which the solid separated in step (3) and optionally washed in step (4) can be dried. In this case, water and any other volatile components present are removed from the solid obtained after completion of step (3) or step (4). Water can be removed in the sense of substantially complete water removal or in the sense of water removal until a desired residual water content is reached. For this purpose, the majority of the water can be removed by conventional methods such as squeezing, press filtration, suction filtration, centrifugation or similar methods, after which drying, optionally assisted by reduced pressure, is carried out, for example at a temperature in the range of 20 to 150°C.

[0061] After completion of step (5), a particulate carbon material according to the invention is obtained, comprising elemental silver and elemental ruthenium, with an average particle size (d50) in the range of 0.5 to 500 μm, a pore volume in the range of 0.5 to 10 mL / g, and a BET surface in the range of 200 to 2,000 m2 / g. Its silver+ruthenium weight proportion, constituted by elemental silver and elemental ruthenium, can vary within wide limits, for example in the range of 0.1 to 50% by weight, preferably 1 to 40% by weight, while the weight ratio of silver to ruthenium can be in the range of, for example, 1 to 2,000 parts by weight of silver to 1 part by weight of ruthenium. Scanning electron micrographs can show that silver and ruthenium are present on the inner surface (in the pores and / or cavities) and / or on the outer surface of the originally silver-free and ruthenium-free carbon particles, thereby forming, for example, discontinuous layers and / or small silver or ruthenium particles (silver or ruthenium islands). The silver and ruthenium are not alloyed, but randomly distributed, and both precious metals are at least partially in contact with each other. It will be clear to those skilled in the art that the silver and ruthenium may contain silver species other than elemental metallic silver and ruthenium species other than elemental metallic ruthenium on their surface, for example the corresponding oxides, halides and / or sulfides. Such species may be formed during the process according to the invention or thereafter, for example during storage, use or further processing of the particulate carbon material according to the invention with elemental silver and elemental ruthenium.

[0062] The particulate carbon material according to the invention, which comprises elemental silver and elemental ruthenium, has a correspondingly low lightness L, for example in the range of 35 to 45. * and is characterized by a dark or black color, which may be a hindrance in some applications. * is the CIEL measured spectrophotometrically with a measurement geometry of d / 8° * a * b * Specific in color space (DIN EN ISO / CIE 11664-4:2020-03) * L *and the spectrophotometric measurement of the particulate carbon material according to the invention with elemental silver and elemental ruthenium can be carried out on a sample poured into a colourless glass vessel up to a filling height of 1 cm from the flat glass bottom of the glass vessel placed on the measuring head of the spectrophotometer used.

[0063] If desired, the particulate carbon material according to the invention comprising elemental silver and elemental ruthenium can be further treated to obtain a color, for example, in the range of 50 to 85, L * For brightening, the particulate carbon material according to the invention comprising elemental silver and elemental ruthenium can be contacted with at least one C1-C4 alkoxide of aluminum, magnesium, calcium, silicon, zinc, zirconium and / or titanium in the presence of at least a sufficient amount of water for complete hydrolysis of the at least one C1-C4 alkoxide. As stated, the brightened particulate material, i.e., having a brightness L in the range of, for example, 50 to 85, can be formed. * A particulate material having a colour, for example grey, can be formed. The brightened particulate material comprises a particulate carbon material according to the invention comprising elemental silver and elemental ruthenium with a solid at least partially located on the surface. Depending on the selection of the at least one C1-C4 alkoxide, the solid is a solid selected from the group consisting of aluminium oxide, aluminium hydroxide, aluminium oxyhydroxide, magnesium oxide, magnesium hydroxide, magnesium oxyhydroxide, calcium oxide, calcium hydroxide, calcium oxyhydroxide, silicon dioxide, silica, zinc oxide, zinc hydroxide, zinc oxyhydroxide, zirconium dioxide, zirconium(IV) oxyhydrate, titanium dioxide, titanium(IV) oxyhydrate and combinations thereof.

[0064] The particulate carbon material according to the invention, comprising elemental silver and elemental ruthenium, and optionally brightened as described above, is characterized by a particularly high antimicrobial effect, as can be determined in a conventional zone of inhibition test or by determining the minimum inhibitory concentration from a growth curve of a microorganism. In this respect, the invention also relates to the use of the particulate carbon material according to the invention, comprising elemental silver and elemental ruthenium, and optionally brightened, as an additive for the antimicrobial treatment of metal surfaces, coatings, plasters, moulding compounds, plastic materials in the form of plastic films, plastic parts or plastic fibres, synthetic resin products, ion exchange resins, silicone products, cellulosic products, foams, cosmetics and many others.

[0065] The use of the optionally whitened particulate carbon material according to the invention with elemental silver and elemental ruthenium as additives is particularly advantageous for antibacterial treatment of filter fleeces; of textiles or in textile applications; in health and hygiene applications, for example in face masks, respirators and insoles; of products with or based on activated carbon, such as plastic materials with activated carbon as additive; of activated carbon filters that can be used for air or water purification; or of products containing activated carbon filters.

[0066] The particulate carbon material according to the invention, comprising elemental silver and elemental ruthenium, and optionally brightened as described above, can also be used as a heterogeneous catalyst, for example in the catalysis of the formation of hydroxyl radicals in aqueous media enabling bacterial growth. EXAMPLES

[0067] Reference Example 1 (Preparation of cellulose powder having 18.9% by weight of elemental silver and 1.0% by weight of elemental ruthenium): 75.6 g (445 mmol) of solid silver nitrate and 13.94 g of ruthenium nitrosyl nitrate solution (ruthenium content 19.0 wt. %, 26.2 mmol of Ru) were dissolved in 416.8 g of deionized water, and the thus obtained aqueous precursor solution was mixed uniformly with 211.2 g of cellulose powder (Vitacel® L-600 from Rettenmaier und Sohne GmbH & Co KG) to form an orange free-flowing impregnated particulate material. 705 mL of an aqueous hydrazine solution at pH 13.9 [4.19 g (131 mmol) of hydrazine and 81.81 g of 32 wt. % sodium hydroxide solution (654.51 mmol of NaOH), the remainder being water] were metered into the free-flowing impregnated particulate material at room temperature with stirring at a metering rate of 30 mL / min. A homogeneous pulp was formed which became easier to stir over time. After the metering was finished, stirring was continued for 30 min until nitrogen evolution was no longer observed. The material was then filtered off by suction, washed with a total of 1,000 mL of water and dried in a drying cabinet at 105° C. / 300 mbar to a residual moisture content of 15 wt.%. A silver content of 18.9 wt.% and a ruthenium content of 1.0 wt.% (for a residual moisture of 0 wt.%) of the final product was determined by ICP-OES.

[0068] Example 2 according to the invention (preparation of a particulate carbon material with 18.7% by weight of elemental silver and 0.9% by weight of elemental ruthenium): An aqueous solution prepared from 157.2 g of aqueous silver nitrate (silver content 36.2 wt.%, 528 mmol Ag) and 14.9 g of aqueous ruthenium nitrosyl nitrate (ruthenium content 18.7 wt.%, 30 mmol Ru) and 1,000 mL of water was added over 3 hours (7 mL / min) to a suspension of 240 g of activated carbon (Ceca 2SW) in 3,000 mL of deionized water. The pH of the suspension was adjusted to 9 using 32 wt.% aqueous sodium hydroxide. The suspension was stirred at 80° C. for 2 days. The suspension was then cooled to 35° C. and a solution of 7.7 g of hydrazine hydrate (hydrazine content 64 wt.%), 96.5 g of sodium hydroxide and 400 mL of water was metered in (3 mL / min) over 3 hours and stirred for a further 4 hours. The material was then filtered off with suction and washed with a total of 20 L of water. In the product thus obtained, a residual water content of 50.8% by weight was determined. By ICP-OES, the product was determined to have a silver content of 18.7% by weight and a ruthenium content of 0.9% by weight (relative to a residual water content of 0% by weight).

[0069] Example 3 (Test to compare the products from Reference Example 1 and Example 2 according to the invention with their antimicrobial effect): In separate Erlenmeyer flasks, 30 mL of a culture of methicillin-resistant Staphylococcus aureus (MRSA) in trypic soy broth (TSB) was adjusted to an optical density of 0.05. Different amounts of the product from Reference Example 1, ranging from 1 to 20 mg, were then weighed out. The samples were incubated at 37° C. and 150 rpm in a shaking incubator. Over a period of 6 hours, the optical density at a wavelength of 600 nm (OD600) was measured at hourly intervals. Inhibition of bacterial growth was indicated by a reduced increase in optical density compared to the control sample. An MRSA culture without the addition of an active antibacterial substance served as the control sample. In the case of complete inhibition of bacterial growth, no increase in optical density became observable. The corresponding sample amounts of the product from Reference Example 1 or Example 2 according to the invention were used to calculate the minimum inhibitory concentration. This resulted in a minimum inhibitory concentration of the product from Reference Example 1 of 0.55 mg / mL, and in comparison a lower minimum inhibitory concentration of the product from Example 2 according to the invention of 0.35 mg / mL.

Claims

1. The catalyst comprises elemental silver and elemental ruthenium, and has an average particle size (d50) in the range of 0.5 to 500 μm, a pore volume in the range of 0.5 to 10 mL / g, and a pore volume in the range of 200 to 2000 m ２ / g range of BET surface area.

2. 2. The material of claim 1, having a silver+ruthenium weight percentage formed by said elemental silver and said elemental ruthenium in the range of 0.1 to 50% by weight, and having a silver to ruthenium weight ratio in the range of 1 to 2,000 parts by weight silver to 1 part by weight ruthenium.

3. 3. The material of claim 1 or 2, comprising 95-100% by weight of carbon particles with elemental silver and elemental ruthenium and 0-5% by weight of carbon particles without precious metals, said weight percentages adding up to 100% by weight.

4. A method for preparing a material according to any one of claims 1 to 3, comprising the steps of reducing at least one silver precursor and at least one ruthenium precursor in the presence of carbon particles, in particular activated carbon particles, suspended in water, separating the solids formed during the reduction process from the aqueous phase, optionally washing the separated solids with water, and optionally drying the separated and optionally washed solids.

5. 5. The method of claim 4, wherein the silver precursor and the ruthenium precursor are reduced sequentially or simultaneously.

6. 6. The method of claim 4 or 5, wherein the at least one silver precursor is selected from the group consisting of silver acetate, silver sulfate, and silver nitrate, and the at least one ruthenium precursor is selected from the group consisting of ruthenium oxalate, ruthenium acetate, and ruthenium nitrosyl nitrate.

7. The activated carbon particles have an average particle size (d50) in the range of 0.5 to 400 μm, a pore volume in the range of 0.5 to 10 mL / g, and a pore size of 300 to 3,000 m ２ The method according to any one of claims 4 to 6, wherein the activated carbon particles have a BET surface area in the range of 0.1 to 0.2 mm / g.

8. 8. The method according to any one of claims 4 to 7, wherein the reduction process is carried out either with formic acid at an acidic pH ranging from 1 to 4 and at a temperature ranging from 70 to 100°C, or with hydrazine at an acidic pH ranging from 1 to 4 and at a temperature ranging from 10 to 40°C, or with a reducing agent selected from the group consisting of sodium borohydride, hydrazine, hypophosphites, and formates at a basic pH ranging from 9 to 14 and at a temperature ranging from 10 to 40°C.

9. (1a) providing an aqueous suspension comprising water, carbon particles, in particular activated carbon particles, at least one silver precursor and at least one ruthenium precursor; (2a) contacting the aqueous suspension with formic acid at a pH in the range of 1 to 4 and a temperature in the range of 70 to 100° C. or with hydrazine at a pH in the range of 1 to 4 and a temperature in the range of 10 to 40° C.; (3) separating the formed solids from the aqueous phase; (4) optionally washing the separated solids; and 9. The method of claim 8 in one aspect, further comprising the optional subsequent step of drying the solid.

10. (1b) providing an aqueous suspension comprising water, carbon particles, in particular activated carbon particles, at least one silver precursor and at least one ruthenium precursor; (2b) contacting the aqueous suspension with a reducing agent selected from the group consisting of sodium borohydride, hydrazine, hypophosphites and formates at a pH in the range of 9 to 14 and a temperature in the range of 10 to 40° C.; (3) separating the formed solids from the aqueous phase; (4) optionally washing the separated solids; and 9. The method of claim 8 in one aspect, further comprising the optional subsequent step of drying the solid.

11. (1c) providing an aqueous suspension having a pH in the range of 9 to 14 comprising water, carbon particles, in particular activated carbon particles, and a reducing agent selected from the group consisting of sodium borohydride, hydrazine, hypophosphites and formates; (2c) contacting said aqueous suspension at a pH in the range of 9 to 14 and at a temperature in the range of 10 to 40° C. with (i) an aqueous solution comprising at least one silver precursor and at least one ruthenium precursor, or (ii) an aqueous solution comprising at least one silver precursor and then an aqueous solution comprising at least one ruthenium precursor, or (iii) an aqueous solution comprising at least one ruthenium precursor and then an aqueous solution comprising at least one silver precursor; (3) separating the formed solids from the aqueous phase; (4) optionally washing the separated solids; and 9. The method of claim 8 in one aspect, further comprising the optional subsequent step of drying the solid.

12. (1d) providing an aqueous suspension having a pH in the range of 1 to 4 comprising water, carbon particles, in particular activated carbon particles, and formic acid or hydrazine; (2d) contacting said aqueous suspension with (i) an aqueous solution comprising at least one silver precursor and at least one ruthenium precursor, or (ii) an aqueous solution comprising at least one silver precursor and then an aqueous solution comprising at least one ruthenium precursor, or (iii) an aqueous solution comprising at least one ruthenium precursor and then an aqueous solution comprising at least one silver precursor, at a pH in the range of 1 to 4 and a temperature in the range of 70 to 100° C. (in the case of formic acid as the reducing agent) or at a temperature in the range of 10 to 40° C. (in the case of hydrazine as the reducing agent); (3) separating the formed solids from the aqueous phase; (4) optionally washing the separated solids; and 9. The method of claim 8 in one aspect, further comprising the optional subsequent step of drying the solid.

13. The particulate carbon material provided with elemental silver and elemental ruthenium is further treated to produce a lightness L in the range of 50 to 85 by contacting the particulate carbon material provided with elemental silver and elemental ruthenium with at least one C1-C4 alkoxide of aluminum, magnesium, calcium, silicon, zinc, zirconium, and / or titanium in the presence of at least a sufficient amount of water for complete hydrolysis of the at least one C1-C4 alkoxide. ＊ A method according to any one of claims 4 to 12, forming a whitened particulate material having

14. Use of the particulate carbon material comprising elemental silver and elemental ruthenium as claimed in claims 1 to 3, or of the particulate carbon material prepared according to the method of any one of claims 4 to 12, or of the particulate carbon material of the product prepared according to the method of claim 13, as an additive for the antibacterial treatment of products comprising activated carbon filters; metal surfaces; coatings, plasters, moulding compounds; plastic materials in the form of plastic films, plastic parts or plastic fibres or with activated carbon as an additive; synthetic resin products; ion exchange resins; silicone products; cellulosic products; foams; cosmetics; filter fleeces; textiles; applications in textiles; applications in health and hygiene; face masks; respirators; insoles; products comprising or based on activated carbon; activated carbon filters used for air or water purification;

15. 14. Use of a particulate carbon material comprising elemental silver and elemental ruthenium according to claims 1 to 3, or of a particulate carbon material prepared by the method according to any one of claims 4 to 12, or of a product prepared according to the method of claim 13, as a heterogeneous catalyst in the catalysis of the formation of hydroxyl radicals in an aqueous medium enabling bacterial growth.

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