METHOD FOR REFINING IRON OXIDE, IRON OXIDE OBTAINED THEREFROM, AND USE THEREOF

Abstract

The present invention relates to a method for refining a material comprising iron oxide and at least one contaminant selected from the group consisting of halogens and sulfur, by reducing the content of said at least one contaminant, characterized in that said material is calcined in the presence of a gas containing water vapor. The present invention also relates to a refined material obtainable from such a method and its use for the manufacture of catalysts.

Description

[Technical field]

[0001] The present invention relates to a method for refining a material comprising iron oxide and at least one contaminant selected from the group consisting of halogens and sulfur, by reducing the content of said at least one contaminant, characterized in that said material is calcined in the presence of a gas containing water vapor. The present invention also relates to a refined material obtainable from such a method and its use in the manufacture of catalysts. [Background technology]

[0002] Iron oxides are used in many industrial applications, some of which have very strict purity requirements, such as in the manufacture of catalysts, batteries and electrical components. For example, the presence of halogens or sulfur can cause material degradation or corrosion of the casing and downstream parts of catalytic reactors.

[0003] The industrially used routes for the production of iron oxide are optimized for low cost and high efficiency, but the nature of the process induces the presence of impurities such as halogens or sulfur. The reduction of the chloride content in regenerated iron oxide from the acid waste of steel pickling, for example by the Ruthner process, is one of the key challenges for the development of regenerated iron oxide as a useful raw material source. According to this route, the iron chloride solution resulting from the washing of steel plates with hydrochloric acid is spray roasted in the presence of air. The obtained iron oxide contains chlorine as an impurity.

[0004] The Penniman process produces iron oxide from an iron sulfate solution. The resulting iron oxide is contaminated with sulfur.

[0005] The patent literature reflects many efforts in the past by various catalyst manufacturers to remove such contaminants from iron oxide feedstocks.

[0006] For example, in WO95 / 25069A1, chlorine-containing iron oxide from the regeneration of steel pickling liquor is treated with a sulfuric acid solution, then filtered, dried and optionally calcined to reduce the chlorine content. The disadvantages of this method are obviously the consumption of chemicals (H2SO4) and the generation of waste liquor.

[0007] In EP1178012B1, chlorine-containing iron oxide is treated with a dilute solution of nitric acid (HNO3), then filtered, dried and calcined to obtain an oxide with reduced chlorine content. As in the previous literature citation, here too the chemical consumption and resulting waste acid solution are disadvantageous to process costs and environmental footprint.

[0008] In EP1379470B1, iron oxide is treated in dry air at high temperatures without any added chemicals to reduce the chlorine content. Considering the absence of chemicals and wastewater, this method is more economically and environmentally advantageous than the previously cited ones. However, to obtain a low residual chlorine content, the iron oxide must be calcined at very high temperatures in the range of up to 1150°C. This results in a very low specific surface area of ​​the treated material, which reduces the reactivity of the iron oxide and is a drawback when used as a catalyst precursor. Furthermore, the calcination furnace tube must be equipped with a tapper or hammer to prevent adhesion of the iron oxide powder to the tube walls.

[0009] GB1203967A teaches calcining iron oxide in the presence of gas containing a hydrogen halide component, such as hydrogen chloride, and water vapor, with the aim of converting non-ferrous metal impurities into volatile non-ferrous metal chlorides and removing them from the iron oxide. The role of water in this reaction system is to prevent the iron oxide from volatilizing as chlorides. Since this document focuses on metal impurities, there is no information about the possibility that the produced iron oxide may be contaminated by halogens. On the contrary, halogens are intentionally introduced into the reaction system to achieve the goal of reducing the content of metal impurities. [Prior art documents] [Patent documents]

[0010] [Patent Document 1] WO95 / 25069A1 [Patent Document 2] EP1178012B1 [Patent Document 3] EP1379470B1 [Patent Document 4] GB1203967A Summary of the Invention [Problem to be solved by the invention]

[0011] Thus, there remains a need for an optimized method for smelting iron oxide in order to reduce the amount of contaminants in the form of halogens or sulfur, and to lower the required calcination temperature and / or the loss of specific surface area.

[0012] It is therefore an object of the present invention to provide such a method and the iron oxide resulting from said method. [Means for solving the problem]

[0013] This object is achieved by a method for refining a material comprising iron oxide and at least one contaminant selected from the group consisting of halogens and sulfur, by reducing the content of said at least one contaminant, characterized in that said material is calcined in the presence of a gas containing water vapor.

[0014] Surprisingly, it has been found that calcining iron oxide in the presence of a gas containing water vapor, such as moist air, can more dramatically reduce the content of halogen and sulfur contaminants and reduces the loss of specific surface area, as compared to calcining in a dry gas, such as dry air.

[0015] Furthermore, it has been found that by firing the iron oxide material in kiln tubes lined with a ceramic material, the deposition of iron oxide on the kiln tubes can be avoided and therefore the use of tapping equipment required when firing in bare metal kiln tubes is not required. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0016] The invention can be used for the purification of any kind of iron oxide material containing halogens or sulfur, whether of mineral or synthetic origin. For example, the iron oxide is of Russner or regenerated type, Penniman, precipitated from sulfates, etc. Preferably, the material used in the method for smelting is produced by spray roasting hydrochloric acid waste liquor originating from the pickling of steel or by the Penniman process. Preferably, the iron oxide subjected to purification and the purified product consist essentially of the hematite (Fe2O3) phase. The term "consists essentially of" preferably refers to a content of the hematite phase of at least 90%, more preferably at least 95%, even more preferably at least 99%, even more preferably at least 99.9%. The material used in the method of the invention is subjected to calcination in the form of a powder.

[0017] The content of halogen or sulfur impurities in the initial material can be up to several percent by weight (understood as tens of thousands of ppm, parts by million). Thus, the material used in the method of the present invention preferably contains iron oxide in an amount of at least 90 percent by weight (wt-%) relative to the total amount of the material. Typically, however, the material used in the refining method of the present invention contains at least 95% by weight, even more preferably at least 97% by weight, even more preferably at least 99% by weight. Thus, in a preferred embodiment, the material used in the refining method of the present invention is iron oxide with impurities of 10% by weight or less, more preferably 5% by weight or less, more preferably 3% by weight or less, more preferably 1% by weight (=10,000 ppm) or less.

[0018] The material used in the smelting process of the present invention comprises iron oxide and at least one contaminant selected from the group consisting of halogens and sulfur.

[0019] Thus, at least one impurity contained in the iron oxide is a halogen, preferably choline, or sulfur. Thus, in a preferred embodiment of the present invention, the material contains chlorine as a halogen contaminant, preferably in an amount of at least 800 ppm (parts per million by mass calculated as Cl, if the halogen is chlorine). Typically, the amount ranges from 800 ppm to 5000 ppm. Thus, the halogen is typically present in the material as a halide, chloride (if halogen = chlorine). Thus, in another preferred embodiment of the present invention, the material contains sulfur as a contaminant, preferably in an amount of at least 800 ppm (parts per million by mass calculated as S). Typically, the amount ranges from 800 ppm to 5000 ppm. Sulfur is typically present in the material as sulfate, sulfite or sulfide. In a further embodiment of the present invention, the iron oxide contains at least both essential impurities, i.e. halogen and sulfur.

[0020] After treatment, the residual content of halogens or sulfur is up to several thousand ppm, preferably up to several hundred ppm, most preferably up to several tens of ppm, or even less than 10 ppm. Thus, the residual content is preferably less than 100 ppm. Preferably, the content of at least one contaminant is reduced by at least 85%, more preferably by at least 90%.

[0021] In a preferred embodiment, the material containing iron oxides and impurities is calcined in a calcination equipment such as a stationary kiln, a roller hearth kiln, a pusher slab kiln, a rotary oven, a fluidized bed or a flash calcination furnace. The calcination equipment device is designed to allow the material to be calcined in the presence of a gas containing water vapor. For example, the device includes a fan to provide a steady flow of gas. The gas is preferably air, nitrogen, combustion gas or a mixture thereof, preferably an air-containing mixture, in particular air. Air containing water vapor is also referred to herein as moist air. Various methods are devised to introduce water vapor into the air stream. For example, low pressure steam can be introduced directly into the inlet air pipe of the calcination furnace. Alternatively, water can be metered by a dosing pump and injected into the gas stream at the inlet of the calcination furnace, preferably as a spray or in the form of droplets through a nozzle. Alternatively, the air can be passed through a saturated column filled with contact material to increase the surface area, in which case the water is introduced by a corresponding pump. The column may be heated to promote evaporation. The above mentioned means of introducing water vapor into the gas stream can also be applied by introducing a steam or spray directly into the oven chamber.

[0022] The term "air" means a mixture of nitrogen and oxygen as main components in any ratio, in particular having a content of at least 95% by volume, typically at least 99% by volume, relative to the total amount of gas under standard conditions, the preferred content being 78% by volume N2 and 21% by volume O2 (the "natural" content).

[0023] Preferably, the gas containing water vapor, such as moist air, contains at least 0.5% by volume of water vapor relative to the total volume of the gas. The content can be 100% by volume or less, i.e. the gas phase consists only of water vapor. Typically, the content is in the range of 1% to 50% by volume of water vapor, preferably 1.5% to 40% by volume, more preferably 2.0% to 30% by volume, even more preferably 2.5% to 20% by volume, even more preferably 2.5% to 15% by volume of water vapor. Gases with a given water vapor content can be prepared by mixing a dry gas with a calculated amount of pure water vapor.

[0024] The gas is typically free of halogens, especially choline.

[0025] The gas to material ratio used in the refining process of the present invention is preferably 0.01 Nm3 of gas per kg of material. 3 (Nm 3 / kg)~100Nm 3 / kg, more preferably 0.1 to 10 Nm 3 / kg, and even more preferably in the range of 0.1 Nm 3 / kg~5Nm 3 / kg range. The gas can be supplied in co-current or counter-current mode relative to the displacement of the solid material.

[0026] The firing temperature used is preferably 700°C to 1200°C, more preferably 800°C to 1150°C, even more preferably 850°C to 1120°C, even more preferably 850°C to 1000°C. The firing time can vary and is between 0.1 seconds and 24 hours. A typical firing time is between 5 minutes and 120 minutes, for example 30 minutes to 60 minutes. This time is used to process the material at a certain temperature. To reach this temperature, a heating stage from room temperature is necessary. The heating rate can vary in the range of 1K / min to 5000K / s. A typical heating gradient is between 1K / min to 50K / min, preferably between 5K / min to 40K / min, more preferably between 10K / min to 30K / min, for example 20K / min.

[0027] The calcination appliance may be heated electrically through its walls, or by microwave heating, or by indirect combustion of fuel gases (without direct contact of the gas with the solid iron oxide), or by direct contact of hot combustion gases with the iron oxide. In the latter case, some or all of the moisture required to carry out the process according to the invention is provided by the combustion process. For example, when methane is used as fuel, an exemplary reaction is as follows: CH4+2O2=CO2+2H2O

[0028] Besides the above example of methane, other materials can also be used as fuel for combustion, such as gaseous or liquid hydrocarbons or hydrogen.

[0029] Thus, the water vapor containing gas may be a mixture of air and fuel, the mixture preferably having an air / fuel equivalence ratio greater than 1.0, more preferably in the range of 1.1 to 30, more preferably in the range of 1.2 to 5.0.

[0030] The calcination equipment may be in the form of a rotary kiln made of high temperature steel and coated or lined with a ceramic material. Surprisingly, it has been found that by using a ceramic coating, the rotary kiln can be used for calcining iron oxide without any equipment for stripping the iron oxide powder from the calcination furnace tube. The ceramic coats consist of a variety of refractory materials, such as alumina, alumino-silica, zirconia, magnesium aluminate, silicon carbide, etc. The tubes can be used without such a lining. In this case, it was observed that the iron oxide powder adhered to the tubes, and a tapping device had to be used to periodically strip the iron oxide cake from the tube walls.

[0031] Thus, in a preferred embodiment, the method of the present invention is carried out in a rotary kiln, preferably having an internal ceramic coating.

[0032] The rotary kiln is operated at an inclination of 0.3 to 5°, preferably 0.4 to 3°, relative to the horizontal. The rotation speed of the kiln tube is 0.4 to 8 rpm (revolutions per minute), preferably 0.5 to 5 rpm.

[0033] Calcination may be carried out at atmospheric pressure, or slightly below atmospheric pressure (with the off-gassing ventilator), or slightly above atmospheric pressure using a compressor to force moist air through or over the solid materials.

[0034] The process of the invention is preferably carried out without prior treatment with acid or base, in particular acid treatment as described in WO 95 / 25069 A1 and EP 1 178 012 B1.

[0035] The specific surface area according to the BET method (DIN ISO 9277:2014-01) of the materials used in the refining process according to the invention is typically less than 1 m 2 / g~10m 2 / g, preferably 3 to 5 m 2 The resulting material after calcination (refined material) with reduced contaminant content preferably has a solubility of at least 1 m 2 / g specific surface area BET.

[0036] Thus, another aspect of the present invention is the refined material obtainable by the refining method of the present invention.

[0037] The iron oxide with reduced contaminant content according to the invention generally has a residual chloride content of less than 400 ppm, preferably less than 300 ppm, and particularly preferably less than 250 ppm, in particular less than 200 ppm. The average particle size, determined by laser diffraction, is generally greater than 0.5 μm, i.e. between 1 μm and 200 μm, preferably between 1.5 μm and 100 μm, particularly preferably between 2 μm and 80 μm, and very particularly preferably between 2 μm and 30 μm, and the fine fraction having a particle size of less than 1 μm is generally less than 15% by weight, preferably less than 10% by weight, particularly preferably less than 5% by weight. The BET specific surface area of ​​the iron oxide treated according to the invention is generally between 0.4 and 5 m2 / g, preferably 0.4 to 3.5 m 2 / g, particularly preferably 0.5 to 3m 2 / g range, and especially 0.6 to 2.5 m 2 / g, very particularly preferably in the range of 0.7 to 2m 2 / g. Preferably, the BET specific surface area is at least 1 m 2 The iron oxides treated according to the invention generally have a hematite structure. They are useful in a range of industrial applications, such as pharmaceuticals, cosmetics, magnetic tape coatings, battery materials, chemical reactions, catalysis, or the preparation of catalysts, in particular for the dehydrogenation of ethylbenzene to styrene.

[0038] Thus, the refined material obtainable by the process of the present invention is useful as part of a catalyst. Another aspect of the present invention is therefore a catalyst containing said material. Such a catalyst can be used in a process for the production of styrene.

[0039] The industrial production of styrene by dehydrogenation of ethylbenzene can be carried out by isothermal or adiabatic processes. Isothermal processes are generally operated at temperatures between 450°C and 700°C, preferably between 520°C and 650°C, in the gas phase, with the addition of steam, at pressures between 0.1 and 5 bar, preferably between 0.2 and 2 bar, particularly preferably between 0.25 and 1 bar, in particular between 0.3 and 0.9 bar. Adiabatic processes are generally operated at temperatures between 450°C and 700°C, preferably between 520°C and 650°C, in the gas phase, with the addition of steam, at pressures between 0.1 and 2 bar, preferably between 0.2 and 1 bar, particularly preferably between 0.25 and 0.9 bar, in particular between 0.3 and 0.8 bar. The catalyst for the dehydrogenation of ethylbenzene to styrene can be regenerated by steam.

[0040] Catalysts for the dehydrogenation of ethylbenzene to styrene generally contain iron oxide and alkali metal compounds, such as potassium oxide. Such catalysts generally further contain a number of promoters. The promoters mentioned include, for example, compounds of calcium, magnesium, cerium, molybdenum, tungsten, chromium and titanium. The catalysts may be prepared using promoter compounds that may be present in the ready-made catalyst or compounds that are converted during production to compounds present in the ready-made catalyst. The catalysts used may also contain auxiliaries to improve processability, mechanical strength or pore structure. Examples of such auxiliaries include potato starch, cellulose, stearic acid, graphite or Portland cement. The materials used can be mixed directly in a mixer, kneader or, preferably, a muller. They can also be slurried to a sprayable mixture and spray-dried to a powder form. EXAMPLES

[0041] The following exemplary embodiment illustrates the difference that using moist air makes compared to processing with a dry air atmosphere.

[0042] Example 1 (Comparative Example) The starting material contained 935 ppm chlorine and 4.15 m 2 A raw iron oxide with a surface area of ​​0.1 μm / g was used. An amount of 500 g of the oxide powder was placed in a rotary quartz glass calciner. Dry air was fed into the calciner at a rate of 470 Nl / h. The calciner was heated from room temperature to the target calcination temperature at a rate of 20 K / min. After the heating stage, the target temperature was kept constant for a residence time of 30 min. The reactor was then cooled to room temperature. The initial cooling rate immediately after the end of the residence time was about 15 K / min. After cooling, a sample of the treated oxide was taken and analyzed, giving the properties shown in Table 1.

[0043] Example 2 (Example of the present invention) The same raw iron oxide as in Comparative Example 1 was used as starting material, the same settings and heating temperatures were used, with the only difference being that the air supplied contained water vapor in an amount of 1.5% by volume. The water vapor concentration was adjusted by sending a dry air stream to the evaporation unit, which was supplied with water at a defined flow rate by a high-precision pump. In order to avoid condensation effects and the associated changes in the water content in the gas stream, the pipe system between the evaporation unit and the calciner was externally heated at a temperature of 180°C. The analytical data of the treated oxide are shown in Table 1.

[0044] Example 3 (Example of the present invention) The same raw iron oxide as in Comparative Example 1 was used as the starting material, and the same settings and heating temperatures were used, with the only difference being that the supplied air contained water vapor in an amount of 2.5% by volume. The analytical data of the treated oxide are shown in Table 1.

[0045] Example 4 (Example of the present invention) The same raw iron oxide as in Comparative Example 1 was used as the starting material, and the same settings and heating temperatures were used, with the only difference being that the supplied air contained water vapor in an amount of 5% by volume. The analytical data of the treated oxide are shown in Table 1.

[0046] Example 5 (Example of the present invention) The same raw iron oxide as in Comparative Example 1 was used as the starting material, and the same settings and heating temperatures were used, with the only difference being that the supplied air contained water vapor in an amount of 10% by volume. The analytical data of the treated oxide are shown in Table 1.

[0047] Example 6 (Example of the present invention) The same raw iron oxide as in Comparative Example 1 was used as the starting material, and the same settings and heating temperatures were used, with the only difference being that the air supplied contained water vapor in an amount of 15% by volume. The analytical data of the treated oxide are shown in Table 1.

[0048] Example 7 (Example of the present invention) The same raw iron oxide as in Comparative Example 1 was used as the starting material, and the same settings and heating temperatures were used, with the only difference being that the supplied air contained water vapor in an amount of 30% by volume. The analytical data of the treated oxide are shown in Table 1.

[0049] Example 8 (Comparative Example) The same raw iron oxide, settings and drying air were used as in Comparative Example 1, except that the heating temperature was 850° C. Analytical data for the treated oxide are shown in Table 1.

[0050] Example 9 (Example of the present invention) The same raw iron oxide, settings and heating temperature were used as in Comparative Example 8, except that the supplied air contained water vapor in an amount of 2.5% by volume. The analytical data of the treated oxide are shown in Table 1.

[0051] Example 10 (Comparative Example) The same raw iron oxide, settings and drying air were used as in Comparative Example 1, except that the heating temperature was 975° C. Analytical data for the treated oxide are shown in Table 1.

[0052] Example 11 (Example of the present invention) The same raw iron oxide, settings and heating temperatures were used as in Comparative Example 10, except that the supplied air contained water vapor in an amount of 2.5% by volume. The analytical data of the treated oxide are shown in Table 1.

[0053] Example 12 (Comparative Example) The starting material contained 2200 ppm sulfur and was 7.4 m 2 The raw iron oxide used had a surface area of ​​0.01 g / g. The calcination conditions were the same as those in Comparative Example 1, and dry air was used. The analytical results are shown in Table 2.

[0054] Example 13 (Example of the present invention) The same raw iron oxide, settings and heating temperatures were used as in Comparative Example 12, except that the air supplied contained water vapor in an amount of 10% by volume. The analytical data of the treated oxide are shown in Table 2.

[0055] Example 14 (embodiment of the present invention) Contains 1000±200ppm of chlorine and 4.0±0.5m 2 The iron oxide used had a surface area of ​​1000 μg / g. The calcination was carried out in a direct-fired rotary calciner. The powder feed rate was 45.5 kg / h and the air feed rate was 86 Nm 3 / h, and the methane fuel gas supply rate is 7.1 Nm 3 / h, resulting in an air-fuel equivalence ratio at the burner of 1.3 and a theoretical moisture content in the burner off-gas of 15% by volume. The burner off-gas was in direct contact with the iron oxide powder. The kiln rotation speed was 4 rpm. The temperature of the material in the kiln was 1085°C (pyrometer reading). Under these conditions, a 1.1m3 powder containing 10 ppm chlorine was produced. 2 A treated iron oxide was obtained having a BET specific surface area of ​​1.0 μm / g.

[0056] Example 15 (Example of the present invention) The same iron oxide, calcination furnace and calcination conditions as in Example 14 were used, but the air supply rate was 100 Nm 3 / h, and methane fuel gas supply rate of 7.6 Nm 3 / h, with an air-fuel equivalence ratio at the burner of 1.4, a firing temperature (pyrometer reading) of 1120°C, and a theoretical moisture content in the burner off-gas of 14% by volume. 2 A treated iron oxide having a surface area of ​​1 / g was obtained.

[0057] [Table 1]

[0058] [Table 2]

[0059] Examples and Comparative Examples 1-15 show the fact that the treatment of iron oxide by calcination in the presence of air containing water vapor results in a significantly lower content of residual halogens or sulfur than the original material or the material treated at the same temperature in dry air. At the same time, the sintering of iron oxide in the presence of moist air is reduced compared to calcination in dry air, and the resulting product has a high surface area and is therefore more suitable for the manufacture of catalysts where the surface area favors higher activity. Furthermore, calcination in moist air can reduce the calcination temperature, which leads to a saving of electrical energy or fuel gas. For example, calcination of chlorine-containing iron oxide in moist air results in a significantly lower content of residual halogens or sulfur than the material calcined at 930 °C in dry air (chlorine 147 ppm, and surface area 1.19 m). 2 At 850°C, the residual chlorine was lower (128 ppm) and the surface area was higher (2.04 m / g) compared to 850°C. 2 / g).

[0060] Thus, the method according to the invention allows for a more economical and efficient processing of halogen or sulfur contaminated iron oxide material, resulting in high purity material suitable for a variety of applications such as catalysts, batteries, electrotechnical components, etc.

Claims

1. 1. A method for refining a material comprising iron oxide and at least one contaminant selected from the group consisting of halogens and sulfur by reducing the content of said at least one contaminant, comprising calcining said material in the presence of a gas containing water vapor.

2. The method of claim 1 , wherein the material comprises iron oxide in an amount of at least 90% by weight.

3. 3. The method according to claim 1 or 2, wherein the material contains chlorine as a halogen contaminant, preferably in an amount of at least 800 ppm.

4. 3. The method of claim 1 or 2, wherein the material contains sulfur contaminants, preferably in an amount of at least 800 ppm.

5. The method according to claim 1 or 2, wherein the calcination is carried out at a temperature in the range of from 700°C to 1200°C.

6. The method according to claim 1 or 2, wherein the calcination is carried out at a temperature in the range of from 850°C to 1000°C.

7. 3. The method according to claim 1 or 2, wherein the gas is air, nitrogen, combustion gas or a mixture thereof, preferably a mixture containing air, in particular air.

8. 8. The method of claim 7, wherein the gas is a mixture of air and fuel, the mixture preferably having an air / fuel equivalence ratio greater than 1.

0.

9. 3. The method according to claim 1 or 2, wherein the water vapor is contained in the gas in an amount of at least 0.5% by volume.

10. 3. The method according to claim 1 or 2, wherein the water vapor is contained in the gas in an amount of 1 vol.% to 50 vol.%, preferably 1.5 vol.% to 40 vol.%, more preferably 2.0 vol.% to 30 vol.%, even more preferably 2.5 vol.% to 20 vol.%, even more preferably 2.5 vol.% to 15 vol.%.

11. 3. The method of claim 1 or 2, wherein the content of the at least one contaminant is reduced by at least 85%.

12. The specific surface area of ​​the material measured by the BET method is 1 m ２ / g to 10m ２ The method according to claim 1 or 2, wherein the molecular weight is 1 / g.

13. The ratio of gas to material is 0.01 Nm ３ / kg to 100Nm ３ The method according to claim 1 or 2, wherein the amount of the active ingredient is in the range of 1 / kg.

14. 3. The method according to claim 1 or 2, wherein the material is produced by spray roasting hydrochloric acid waste liquor arising from the pickling of steel or by the Penniman process.

15. 3. The process according to claim 1 or 2, carried out without prior treatment with acid or base.

16. 3. The method according to claim 1 or 2, preferably carried out in a rotary kiln having an internal ceramic coating.

17. 17. The method according to claim 16, wherein the kiln has an inclination to the horizontal of 0.3° to 5°, preferably 0.4° to 3° and / or a rotation speed of 0.4 rpm to 8 rpm, preferably 0.4 rpm to 5 rpm.

18. 3. The method of claim 1 or 2, wherein the iron oxide contained in the material consists essentially of hematite.

19. A refined material obtainable by the method according to claim 1 or 2.

20. 20. Use of the refined material according to claim 19 for the production of a catalyst, preferably for the production of a styrene production catalyst.

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