Pyrolysis prepared surface modified magnesium oxide

Abstract

The invention relates to surface-modified magnesium oxide produced by pyrolysis, to a method for producing same, and to the use thereof.

Description

[0001] The invention relates to pyrolytically prepared, surface-modified magnesium oxide, a preparation method thereof and uses thereof.

[0002] Ceramic oxide particles are known, in particular silicon dioxide, aluminum oxide, titanium dioxide and zirconium oxide. For many applications, it is advantageous to use high-surface pyrogenic magnesium oxide, for example for applications in the field of catalysis (for example in: S. Demirci et al., Materials Science in Semiconductor Processing 34 (2015), 154-161).

[0003] For some applications, the surface of a hydrophilic magnesium oxide must be treated to produce a hydrophobic surface instead of a hydrophilic surface. On the one hand, the hydrophobic surface functionalization protects the magnesium oxide from reacting with air moisture, on the other hand, the hydrophobic surface is important for compatibility in organic systems.

[0004] To date, only surface treatment of high surface pyrogenic magnesium oxide using methyl silica sol has been described (eg in: NR Dhineshbabu et al., “Hydrophobicity, flame retardancy and antibacterial properties of cotton fabrics functionalized with MgO / methyl silicatenano composites”, RSC Adv. 2014, 4, 32161).

[0005] The variability of such surface treatments is very limited. It is therefore an object of the present invention to provide a surface-modified magnesium oxide having a broad scope for surface modification without altering the desired properties of the magnesium oxide used. Surprisingly, the present invention makes it possible to achieve the combination of said challenging tasks.

[0006] Therefore, in a first aspect of the present invention, there is provided a pyrolytically prepared, surface-modified magnesium oxide, characterized in that:

[0007] Surface area [m 2 / g](DIN 66 131) 50 to 350

[0008] Tamped density [g / L] (DIN ISO 787 / XI) 20 to 120, preferably 40 to 120,

[0009] Drying loss [%] (DIN ISO 787II) less than 5

[0010] Loss on ignition [%] (DIN 55 921) 0.1 to 20

[0011] Carbon content [%] (elemental analysis using LECO C744 instrument) 0.1 to 15.

[0012] Therefore, a second object of the present invention is a process for preparing a pyrogenically prepared, surface-modified magnesium oxide, characterized in that a pyrogenically prepared hydrophilic magnesium oxide is sprayed with a surface modifier at room temperature and the mixture is subsequently heat treated at a temperature of 50° C. to 300° C., preferably 80° C. to 180° C., for a period of 0.5 to 3 hours.

[0013] An alternative method of surface modification of pyrolytically prepared magnesium oxide may be carried out by treating the pyrolytically hydrophilic magnesium oxide with a surface modifier in vapor form and subsequently heat treating the mixture at a temperature of 50°C to 800°C, preferably 300°C to 600°C, for a period of 0.5 to 6 hours, preferably 0.5 to 2 hours.

[0014] The heat treatment can be carried out under a protective gas, such as nitrogen. The surface treatment can be carried out continuously or batchwise in a heatable mixer and dryer with a spray device. Suitable devices can be, for example, a plowshare mixer or a plate, cyclone or fluidized bed dryer.

[0015] An advantage of the present invention is that commercially available silane-modified magnesium oxide can be used and the properties of the magnesium oxide can thus be individually adjusted according to the desired properties and the intended purpose.

[0016] Preferably, hydrophilic magnesium oxide prepared by pyrolysis is used, characterized in that:

[0017] Surface area [m 2 / g](DIN 66 131) 50 to 350

[0018] Tamped density [g / L] (DIN ISO 787 / XI) 20 to 100

[0019] Drying loss [%] (DIN ISO 787II) less than 5

[0020] Loss on ignition [%] (DIN 55 921) 0.1 to 15.

[0021] As used herein, the term "pyrolytically prepared hydrophilic magnesium oxide" refers to magnesium oxide prepared directly by a pyrolytic process, also known as a "fumed" process, or by further modification of a pyrolytically prepared precursor. The terms "pyrolytically prepared", "pyrolysis" and "fumed" are used equivalently in the context of the present invention. Fumed magnesium oxide can be prepared using flame hydrolysis or flame oxidation. This involves oxidizing or hydrolyzing a hydrolyzable or oxidizable starting material, usually in a hydrogen / oxygen flame. Starting materials typically used in pyrolytic processes include organic or inorganic substances, such as metal chlorides.

[0022] Therefore, hydrophilic magnesium oxide can be prepared by flame spray pyrolysis, wherein

[0023] flame spray pyrolysis of at least one solution of a metal precursor, the at least one solution comprising

[0024] - magnesium salts,

[0025] -Solvents such as ethanol, methanol or water.

[0026] During the flame spray pyrolysis process, a solution of a metal compound (metal precursor) in the form of fine droplets is typically introduced into a flame formed by igniting a fuel gas and an oxygen-containing gas, wherein the metal precursor used is oxidized and / or hydrolyzed to give the corresponding magnesium oxide.

[0027] The reaction initially forms highly dispersed, approximately spherical primary particles, which coalesce in the further course of the reaction to form aggregates. The aggregates can subsequently accumulate into agglomerates. In contrast to agglomerates, which can usually be separated into aggregates relatively easily by introducing energy, the aggregates can only be broken down further, if at all, by intensive introduction of energy.

[0028] The resulting aggregate compound may be referred to as "gas phase" or "pyrolytically prepared" magnesium oxide.

[0029] Flame spray pyrolysis processes are generally described in WO 2015173114 A1 and elsewhere.

[0030] The flame spray pyrolysis process preferably comprises the following steps:

[0031] a) atomizing a solution of a metal precursor using an atomizer gas to obtain an aerosol,

[0032] b) reacting the aerosol in the reaction space of a reactor with a flame obtained by igniting a mixture of a fuel gas and an oxygen-containing gas to obtain a reaction stream,

[0033] c) cooling the reaction stream, and

[0034] d) subsequently removing solid magnesium oxide from the reaction stream.

[0035] The metal precursor used in the method includes a magnesium salt, such as magnesium chloride, magnesium nitrate or magnesium acetate.

[0036] The solvent of the solution may be all typical solvents such as water, ethanol, methanol and others.

[0037] The amount of the metal precursor in the solution may range from 5 wt % to 80 wt %, preferably from 20 wt % to 70 wt %, based on the total weight of the solution.

[0038] Examples of fuel gases are hydrogen, methane, ethane, natural gas and / or carbon monoxide. Particular preference is given to using hydrogen.

[0039] The oxygen-containing gas is generally air or oxygen-enriched air. Oxygen-containing gases are particularly useful in embodiments where it is desired to prepare magnesium oxide having a high BET surface area. The total amount of oxygen is generally selected so as to be sufficient to at least completely convert the fuel gas and the metal precursor.

[0040] In order to obtain an aerosol, the vaporized solution containing the metal precursor can be mixed with an atomizer gas, such as nitrogen, air and / or other gases. The fine droplets of the resulting aerosol preferably have an average droplet size of 1-120 μm, particularly preferably 30-100 μm. Typically, a single material or multi-material nozzle is used to generate the droplets. In order to increase the solubility of the metal precursor and to obtain a viscosity suitable for solution atomization, the solution can be heated.

[0041] The particle size of the magnesium oxide can be varied by means of reaction conditions such as flame temperature, hydrogen or oxygen ratio, amount of magnesium salt, residence time in the flame or length of the condensation zone.

[0042] The method described above provides high surface area, pyrolytically prepared hydrophilic magnesium oxide with a specific BET surface area of ​​50-350 m 2 / g, preferably 150-300m 2 / g.

[0043] This material itself is advantageous in terms of balanced properties, which allows this material to have a wide range of applications. In addition, this material provides an advantageous basis for providing the surface-modified magnesium oxide of the present invention.

[0044] As surface modifiers, the following compounds and mixtures of the following compounds can be used:

[0045] a)(RO)3Si(C n H 2n+1 ) and (RO)3Si(C n H 2n-1 ) type organosilane, wherein

[0046] R = alkyl, such as methyl, ethyl, n-propyl, isopropyl, butyl, and

[0047] n=1-20.

[0048] b) R' x (RO) y Si(C n H 2n+1 ) and R' x (RO) y Si(C n H2n-1 ) type organosilane, wherein

[0049] R = alkyl, such as methyl, ethyl, n-propyl, isopropyl, butyl

[0050] R' = alkyl, such as methyl, ethyl, n-propyl, isopropyl, butyl

[0051] R'=cycloalkyl

[0052] n=1-20

[0053] x+y=3

[0054] x=1,2, and

[0055] y=1,2.

[0056] c)X3Si(C n H 2n+1 ) and X3Si(C n H 2n-1 ) type halogenated organosilane, wherein

[0057] X=Cl、Br

[0058] n=1-20.

[0059] d)X2(R')Si(C n H 2n+1 ) and X2(R')Si(C n H 2n-1 ) type halogenated organosilane, wherein

[0060] X=Cl、Br

[0061] R' = alkyl, such as methyl, ethyl, n-propyl, isopropyl, butyl

[0062] R'=cycloalkyl

[0063] n=1-20.

[0064] e)X(R')2Si(C n H 2n+1 ) and X(R')2Si(C n H 2n-1 ) type halogenated organosilane, wherein

[0065] X=Cl、Br

[0066] R' = alkyl, such as methyl, ethyl, n-propyl, isopropyl, butyl

[0067] R'=cycloalkyl

[0068] n=1-20.

[0069] f)(RO)3Si(CH2) m -R' type organosilane

[0070] R = alkyl, such as methyl, ethyl, propyl

[0071] m=0.1-20

[0072] R' = methyl-, aryl (e.g. -C6H5, substituted phenyl residue), C4F9, OCF2-CHF-CF3, -C6F 13 , -O-CF2-CHF2, -NH2, -N3, -SCN, -CH=CH2, -NH-CH2-CH2-NH2, -N-(CH2-CH2-NH2)2, -OOC(CH3)C=CH2, -OCH2-CH(O)CH2,

[0073] -NH-CO-N-CO-(CH2)5, -NH-COO-CH3, -NH-COO-CH2-CH3,

[0074] -NH-(CH2)3Si(OR)3, -S x -(CH2)3Si(OR)3, -SH, -NR'R"R"'

[0075] R'=alkyl, aryl;

[0076] R"=H, alkyl, aryl;

[0077] R"'=H, alkyl, aryl, benzyl, C2H4NR""R""', where R""=H, alkyl, and

[0078] R""'=H, alkyl.

[0079] g)(R") x (RO) y Si(CH2) m -R' type organosilane

[0080] R"=alkyl

[0081] x+y=2

[0082] = Cycloalkyl x = 1.2

[0083] y=1.2

[0084] m=0.1 to 20

[0085] R' = methyl-, aryl (e.g. -C6H5, substituted phenyl residue), C4F9, OCF2-CHF-CF3, -C6F 13, -O-CF2-CHF2, -NH2, -N3, -SCN, -CH=CH2, -NH-CH2-CH2-NH2, -N-(CH2-CH2-NH2)2, -OOC(CH3)C=CH2 , -OCH2-CH(O)CH2, -NH-CO-N-CO-(CH2)5, -NH-COO-CH3, -NH-COO-CH2-CH3, -NH-(CH2)3Si(OR)3, -S x -(CH2)3Si(OR)3, -SH, -NR'R"R"

[0086] R'=alkyl, aryl;

[0087] R"=H, alkyl, aryl;

[0088] R"'=H, alkyl, aryl, benzyl, C2H4NR""R""', where R""=H, alkyl, and

[0089] R""'=H, alkyl.

[0090] h)X3Si(CH2) m -R' type halogenated organosilane

[0091] X=Cl、Br

[0092] m=0.1-20

[0093] R' = methyl-, aryl (e.g. -C6H5, substituted phenyl residue), C4F9, OCF2-CHF-CF3, -C6F 13 , -O-CF2-CHF2, -NH2, -N3, -SCN, -CH=CH2, -NH-CH2-CH2-NH2, -N-(CH2-CH2-NH2)2, -OOC(CH3)C=CH2 , -OCH2-CH(O)CH2, -NH-CO-N-CO-(CH2)5, -NH-COO-CH3, -NH-COO-CH2-CH3, -NH-(CH2)3Si(OR)3, -S x -(CH2)3Si(OR)3, -SH.

[0094] i)(R)X2Si(CH2) m -R' type halogenated organosilane

[0095] X=Cl、Br

[0096] R = alkyl, such as methyl, ethyl, propyl

[0097] m=0.1-20

[0098] R' = methyl-, aryl (e.g. -C6H5, substituted phenyl residue), C4F9, OCF2-CHF-CF3, -C6F 13 , -O-CF2-CHF2, -NH2, -N3, -SCN, -CH=CH2, -NH-CH2-CH2-NH2, -N-(CH2-CH2-NH2)2, -OOC(CH3)C=CH2 , -OCH2-CH(O)CH2, -NH-CO-N-CO-(CH2)5, -NH-COO-CH3, -NH-COO-CH2-CH3, -NH-(CH2)3Si(OR)3, -S x -(CH2)3Si(OR)3, -SH,

[0099] j) (R) 2X Si(CH2) m-R' type halogenated organosilane

[0100] X=Cl、Br

[0101] R=alkyl

[0102] m=0.1-20

[0103] R' = methyl-, aryl (e.g. -C6H5, substituted phenyl residue), C4F9, OCF2-CHF-CF3, -C6F 13 , -O-CF2-CHF2, -NH2, -N3, -SCN, -CH=CH2, -NH-CH2-CH2-NH2, -N-(CH2-CH2-NH2)2, -OOC(CH3)C=CH2 , -OCH2-CH(O)CH2, -NH-CO-N-CO-(CH2)5, -NH-COO-CH3, -NH-COO-CH2-CH3, -NH-(CH2)3Si(OR)3, -S x -(CH2)3Si(OR)3, -SH.

[0104] Preferably, the following silanes are used as surface modifiers, alone or in a mixture: dimethyldichlorosilane, octyltrimethoxysilane, octyltriethoxysilane, hexamethyldisilazane, 3-methylmethacryloxypropyltrimethoxysilane, 3-methacryloxypropyltriethoxysilane, hexadecyltrimethoxysilane, hexadecyltriethoxysilane, dimethylpolysiloxane, glycidyloxypropyltrimethoxysilane, glycidyloxypropyltriethoxysilane, nonafluorohexyltrimethoxysilane Acryloyloxypropyl trimethoxysilane, 3-methacryloxypropyl triethoxysilane, hexadecyl trimethoxysilane, hexadecyl triethoxysilane, dimethyl polysiloxane, glycidyloxypropyl trimethoxysilane, glycidyloxypropyl triethoxysilane, nonafluorohexyl trimethoxysilane (nanofluorohexyltrimethoxysilane), tridecafluorooctyl trimethoxysilane, tridecafluorooctyl triethoxysilane, aminopropyl triethoxysilane. Particularly preferably, octyl trimethoxysilane and octyl triethoxysilane can be used.

[0105] The surface modified magnesium oxide showed 50m 2 / g to 350m 2 / g, preferably 150m 2 / g to 300m 2 High BET surface area values ​​between 1.17 and 1.1 g.

[0106] The pyrolytically prepared, surface-modified magnesium oxide according to the invention can be used in a wide variety of applications, for example in industrial applications such as electronics, catalysis, paints and oils, or in the production of cathode and / or anode active material coatings for cathodes and anodes in lithium-ion and sodium-ion batteries.

[0107] Even without other explanations, it is believed that one skilled in the art can fully utilize the above description.The preferred embodiments and examples are therefore to be construed as merely descriptive and not limiting in any way.

[0108] Hereinafter, the present invention is explained in more detail using examples. Alternative embodiments of the present invention can be obtained in a similar manner. BRIEF DESCRIPTION OF THE DRAWINGS

[0109] Figure 1 TEM image showing hydrophilic magnesium oxide. The measurement was performed using a Hitachi H-7500 with an accelerating voltage of 100 KV and a resolution of 0.34 nm.

[0110] Figure 2 Shown is the XRD spectrum of the hydrophilic magnesium oxide obtained in Example 1. The sample was analyzed with an X-ray diffractometer from Malvern Pananlytical (X'Pert Pro). Example

[0111] Determination of physicochemical property data

[0112] In the context of the present invention, the following measurement methods for evaluating the characteristics of different materials are used:

[0113] A) BET surface area:

[0114] The BET surface area is determined in accordance with DIN 66 131 using nitrogen.

[0115] B) Compacted density:

[0116] Determination of the compacted density according to DIN ISO 787 / XI,

[0117] Principle of compacted density determination:

[0118] The tamped density (formerly tamped volume) is equal to the quotient of the mass and volume of a powder after tamping in a tamping volumeter under predetermined conditions. According to DIN ISO 787 / XI, the tamped density is expressed in g / cm 3 However, due to the very low tamped density of the oxides, we give the value in g / L. Furthermore, drying and sieving as well as repeated tamping operations are omitted.

[0119] Equipment for tamped density determination:

[0120] Compaction volume meter

[0121] Graduated Cylinder

[0122] Laboratory scale (read to 0.01g)

[0123] To perform a tamped density determination:

[0124] Fill the measuring cylinder of the tamping volume meter with 200 ± 10 mL of oxide, leaving no pores and with the surface level. Determine the mass of the filled sample accurately to 0.01 g. Place the measuring cylinder with the sample in the measuring cylinder holder of the tamping volume meter and tamp 1250 times. Read the volume of the tamped oxide accurately once.

[0125] Evaluation of tamped density determination

[0126]

[0127] C) pH value:

[0128] The pH values ​​were determined in a 4% aqueous dispersion of the hydrophobic oxide in water:methanol (1:1).

[0129] Reagents for pH determination:

[0130] Distilled water or completely deionized water, pH>5.5

[0131] Methanol, pa

[0132] Buffer solution pH 7.00 pH 4.66

[0133] Equipment for pH determination:

[0134] Laboratory scale, (read to 0.1g)

[0135] Glass beaker, 250mL

[0136] Magnetic stirrer

[0137] Magnetic bar, 4cm long

[0138] Combination pH Electrode

[0139] pH Measurement Equipment

[0140] Dispenser, 100mL

[0141] Working procedure for determining pH value:

[0142] Determination according to DIN / ISO 787 / IX:

[0143] Calibration: Prior to pH determination, the measuring device is calibrated with a buffer solution. If multiple measurements are performed in succession, a single calibration is sufficient.

[0144] 4 g of the hydrophilic oxide was stirred into a paste in a 250 mL glass beaker containing 96 g (96 mL) of water using a dispenser and stirred with a magnetic stirrer for five minutes (rpm about 1000 min) with the pH electrode submerged. -1 ).

[0145] 4 g of the hydrophobic oxide was stirred into a paste in a 250 mL glass beaker containing 48 g (61 mL) of methanol. The suspension was diluted with 48 g (48 mL) of water and stirred with a magnetic stirrer for five minutes (rpm about 1000 min) with the pH electrode immersed. -1 ).

[0146] After turning off the stirrer, let the mixture stand for one minute and then read the pH value. The result should be accurate to one decimal place.

[0147] D) Loss on drying

[0148] For the loss on drying determination, a 1 g weighing weight was used, compared to the 10 g weighing weight mentioned in DIN ISO 787 II.

[0149] Keep cover in place before cooling. No secondary drying is performed.

[0150] Weigh about 1 g of sample to the nearest 0.1 mg, place in a weighing pan with a ground cover that has been dried at 105° C. to avoid dust formation, and dry for two hours in a drying oven at 105° C. After cooling in the desiccator with the cover still on, reweigh the sample under the blue gel.

[0151]

[0152] The result is accurate to one decimal place.

[0153] E) Loss on ignition

[0154] Equipment for determining loss on ignition:

[0155] Porcelain crucible with crucible cover

[0156] Muffle furnace

[0157] Analytical scale (read to 0.1 mg)

[0158] Dryer

[0159] Loss on ignition:

[0160] In contrast to DIN 55 921, 0.3-1 g of undried material is weighed to the nearest 0.1 mg, placed in a porcelain crucible with a crucible cover which has been preheated to red heat, and heated to red heat in a muffle furnace at 1000° C. for 2 hours.

[0161] Care is taken to avoid dust formation. It has proven to be advantageous to place the weighed sample in the muffle furnace while the muffle furnace is still cold. Slow heating of the furnace prevents strong air turbulence from occurring in the porcelain crucible. After 1000° C. has been reached, red-hot heating is continued for a further 2 hours. Subsequently, the crucible cover is put in place and the weight loss of the crucible is determined on a blue gel in a desiccator.

[0162] Evaluation of loss on ignition

[0163] Since the loss on ignition was measured relative to a sample dried at 105°C for 2 hours, the following calculation formula was obtained:

[0164]

[0165] m0=weighing weight (g)

[0166] TV = Loss on drying (%)

[0167] m1 = weight of the sample after heating to red heat (g)

[0168] The result is accurate to one decimal place.

[0169] F) Carbon content

[0170] The carbon content is determined by elemental analysis using a LECO C744 instrument. The measuring principle is based on the oxidation of carbon in the sample to CO2, which is subsequently quantified by an infrared detector.

[0171] Preparation of magnesium oxide:

[0172] Example 1: Preparation of magnesium oxide prepared by pyrolysis

[0173] 1.89 kg of an aqueous solution containing 1000 g of Mg(CH3COO)2*4H2O was prepared.

[0174] 2.5 kg / h of this dispersion and 15 Nm 3 / h air aerosol and sprayed into a tubular reaction with a combustion flame. The combustion gas of the flame is 8Nm 3 / h hydrogen and 30Nm 3 / h air composition. In addition, use 25Nm 3 After the reactor, the reaction gas is cooled and filtered.

[0175] The particle characteristics are shown in Table 1 and the TEM images of the particles are shown in Figure 1 And XRD analysis ( Figure 2 ) showed that the main phase of the product was cubic magnesium oxide.

[0176] The resulting high surface area, pyrolytically prepared hydrophilic magnesium oxide has the physicochemical property data shown in Table 1.

[0177] Example 2: Preparation of surface-modified magnesium oxide

[0178] 300 g of pyrolytically prepared magnesium oxide (Example 1) were placed in a mixer and sprayed with 72 g of octyltrimethoxysilane. After the spraying of the silane onto the powder was complete, mixing was continued for a further 5 minutes. The wetted powder was subsequently tempered in an oven at 130° C. for 3 hours.

[0179] The surface-modified magnesium oxide thus formed had the physicochemical property data shown in Table 1.

[0180] Example 3: Preparation of surface modified magnesium oxide

[0181] 300 g of pyrolytically prepared magnesium oxide (Example 1) were placed in a mixer and sprayed with 36 g of octyltrimethoxysilane. After the spraying of the silane onto the powder was complete, mixing was continued for a further 5 minutes. The wetted powder was subsequently tempered in an oven at 130° C. for 3 hours.

[0182] The hydrophilic and surface-modified magnesium oxide has the physicochemical property data shown in Table 1.

[0183] Table 1: Characteristics

[0184] characteristic Example 1 Example 2 Example 3 <![CDATA[BET[m 2 / g]]]> 240 225 234 Compacted density [g / L] 56 78 63 pH 10.5 10.2 10.3 Loss on drying [%] 0.5 0.6 0.2 Loss on ignition [%] 12.2 17.6 14.0 Carbon content [%] 0.0 9.7 5.9

Claims

1. Pyrolytically prepared, surface-modified magnesium oxide having the following physicochemical properties:

2. A method for preparing a pyrolytically prepared, surface-modified magnesium oxide according to claim 1, comprising spraying a pyrolytically prepared hydrophilic magnesium oxide with a surface modifier at room temperature and subsequently heat treating the mixture at a temperature of 50°C to 300°C for a period of 0.5 to 3 hours.

3. A process for preparing a pyrolytically prepared, surface-modified magnesium oxide according to claim 1, comprising spraying the pyrolytically prepared hydrophilic magnesium oxide with a surface modifier in vapor form and subsequently heat treating the mixture at a temperature of 50°C to 800°C for a period of 0.5 to 6 hours.

4. The method according to claim 2 or 3, wherein the hydrophilic magnesium oxide is prepared by the following method, wherein flame spray pyrolysis of at least one solution of a metal precursor, the at least one solution comprising - magnesium salts, -Solvent.

5. The method according to claim 4, wherein the flame spray pyrolysis comprises the following steps: a) atomizing a solution of a metal precursor using an atomizer gas to obtain an aerosol, b) reacting the aerosol in the reaction space of a reactor with a flame obtained by igniting a mixture of a fuel gas and an oxygen-containing gas to obtain a reaction stream, c) cooling the reaction stream, and d) subsequently removing solid magnesium oxide from the reaction stream.

6. The method according to any one of claims 2 to 5, wherein the hydrophilic magnesium oxide prepared by pyrolysis has the following physicochemical properties: Surface area [m 2 / g](DIN 66 131)50 to 350 Tamped density [g / L] (DIN ISO 787 / XI) 20 to 100 Drying loss [%] (DIN ISO 787II) less than 5 Loss on ignition [%] (DIN 55 921) 0.1 to 15.

7. The method according to any one of claims 2 to 6, wherein the surface modifier is selected from dimethyldichlorosilane, octyltrimethoxysilane, octyltriethoxysilane, hexamethyldisilazane, 3-methacryloxypropyltrimethoxysilane, 3-methacryloxypropyltriethoxysilane, hexadecyltrimethoxysilane, hexadecyltriethoxysilane, dimethylpolysiloxane, glycidyloxypropyltrimethoxysilane, glycidyloxypropyltriethoxysilane, nonafluorohexyltrimethoxysilane, tridecafluorooctyltrimethoxysilane, tridecafluorooctyltriethoxysilane, aminopropyltriethoxysilane, alone or in a mixture.

8. Use of the pyrolytically prepared, surface-modified magnesium oxide according to claim 1 in electronics, catalysis, paints and oils, or in the production of cathode and / or anode active material coatings for cathodes and anodes in lithium-ion and sodium-ion batteries.

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