EA043234B1 - METHOD FOR REDUCING SULFUR CONTENT IN ANATASE FORM TITANIUM DIOXIDE AND THE PRODUCT OBTAINED BY SUCH METHOD - Google Patents

Description

This invention relates to the field of heterogeneous catalysis. In more detail, it relates to a process for reducing the sulfur content of stabilized anatase titanium dioxide, to the catalytic base materials thus obtained, and to their use in the manufacture of heterogeneous catalysts.

Titanium dioxide is a well known material for making heterogeneous catalysts. It has found wide application either as a catalytic material (eg Claus catalysis) or as a catalyst support (eg selective catalytic reduction of nitrogen oxides, Fischer-Tropsch process).

The predominant and in most cases preferred polymorph for heterogeneous catalysis is the anatase crystalline phase. The large industrial scale production of anatase-type TiO ₂ is based on the so-called sulfate process, in which titanium-rich raw materials (ilmenite or Ti-slag) are first reacted with concentrated sulfuric acid to form TiOSO ₄ . Directly after hydrolysis, finely dispersed anatase-type TiO ₂ with a high water content (so-called metatitanic acid with the general formula TiO(OH) ₂ ) is obtained. After additional purification steps, which include reduction and washing procedures, pure anatase TiO ₂ can be obtained.

Another large-scale TiO ₂ production process is the so-called chloride process, which uses a very high Ti raw material (natural or synthetic rutile or Ti slag), chlorine and carbon to produce TiCl ₄ in the first step, which can be easily purified by distillation. . Directly after combustion in an oxygen-rich flame, pure TiO ₂ in rutile form is obtained. The pure anatase form TiO ₂ polymorph cannot be obtained by this method.

Another procedure for the production of anatase type TiO2 is flame hydrolysis of TiCl4 resulting in a mixture of rutile and anatase only.

The performance of heterogeneous catalysts is often dependent on purity. Scattered ions can adversely affect the completeness of the conversion in the catalytic process and/or selectivity. Common unwanted impurities are phosphorus, sulfur, heavy metals, alkali and alkaline earth metals.

For example, the Fischer-Tropsch synthesis of hydrocarbons from synthesis gas (a mixture of CO and H2) is very sensitive to sulfur impurities, since sulfur reacts with catalytically active cobalt, forming cobalt sulfides (Co _x S _y ), which subsequently lead to greatly reduced catalytic performance. characteristics. Typically, sulfur levels of FT catalysts are below 150 ppm, preferably below 100 ppm. The main impurity in the sulfate process for producing anatase TiO ₂ is sulfur, which is a consequence of the addition of sulfuric acid from the production process. Impurities of other scattered ions are in the range of tenths or less than hundredths of a ppm. and are usually non-critical.

The performance of heterogeneous catalysts also depends on physical properties. A very good dispersion of the catalytically active substrate material is often a prerequisite for observing high conversions. Typically, high specific surface areas of the substrate are important to ensure maximum dispersion of the catalytically active sites.

In summary, there is a need for large-scale industrial availability of anatase-type TiO ₂ for catalytic applications, which shows:

i) high specific surface area (BET > 40 m ² /g); and ii) low sulfur level (< 150 ppm S).

From an industrial point of view, the only industrial large-scale and thus cost-effective way to produce anatase-type TiO2 is the sulfate process. Significant disadvantages of this process are the high sulfur content in the end product, which is known to be detrimental to many catalytic applications. Thus, a process must be found that enables large-scale production of anatase-type TiO2 with high specific surface area (>40 m ² /g) and low sulfur (< 150 ppm S).

Some technologies have been developed to reduce the sulfur level in anatase type TiO2 from the sulfate process. The most common is washing with water. Typically, TiO2 in anatase form containing sulfates is suspended in water and washed on a filter medium (eg pressfilter). Washing is performed with cold or preferably hot deionized water. The minimum levels of sulfur that can be obtained in this way are in the range of 0.1-0.5 wt.%.

The reaction of the excess sulfuric acid with the appropriate base (NaOH, aqueous ammonia, etc.) and the removal of the salts formed, by excessive washing with deionized water, allows for significantly lower sulfur levels of 0.03-0.2 wt%. There is a certain risk of contamination, especially when using basic metal solutions (eg NaOH or KOH), because by using an excess amount of base in order to obtain the lowest levels of sulfates, metal ions are very difficult to leach out of anatase.

Sulfur reduction can also be done by successive washing cycles with additional strong base treatment and successive removal of metal ions by acid washing. In this case, it is preferable to use acids (eg acetic acid) which can be easily removed either during washing or a possible subsequent heating step.

During the production of pigmented grade titanium dioxide, sulfur is removed by thermal decomposition of sulfuric acid. At temperatures above 500°C, a significant reduction in sulfate impurities is observed, but during this heat treatment there are also two methods:

i) the TiO ₂ particles undergo particle growth which results in a significant and irreversible decrease in specific surface area, and

II) at these temperatures, a phase transition occurs from the anatase form to the rutile form of the polymorph.

Both methods are required in order to obtain pigmented TiO ₂ which typically has a low BET (< 20m2/g) and rutile type TiO ₂ , but they interfere with the procedure in which, when applied to a large surface area, anatase TiO ₂ comes out with low sulfur sulfate production method.

As a result, there is no available method that makes it possible to produce anatase-type TiO ₂ by large-scale industrial production that exhibits the following properties:

1. Ultra low sulfur content (< 150 ppm).

2. BET surface area > 20 m ² /g, preferably > 30 m ² /g and more preferably > 40 m ² /g

3. TiO ₂ in pure anatase phase.

There is a need for a low sulfur anatase type catalyst base material with a high specific surface area that is readily available for large scale industrial processes.

In this regard, it has surprisingly been found that anatase-type titania doped with an appropriate amount of silica and/or zirconium oxide and or alumina can be treated at temperatures high enough to decompose sulfuric acid while retaining substantially higher specific surface areas. In this regard, the term thermal stabilization should be understood as an anatase-type TiO ₂ stabilized such that i) the rutile transition temperature is shifted towards higher temperatures and ii) the BET decreasing tendency is reduced.

In a typical experiment according to the invention, TiO ₂ anatase type, which has a content of 8 wt.% SiO ₂ heated for one hour to temperatures above 1000°C. The resulting powder exhibits a BET specific surface area of about 50-70 m ² /g and residual sulfur contamination < 50 ppm. The degree of thermal aging resistance of anatase is highly dependent on the amount of silica added. Small amounts only lead to insignificant stability, while large amounts of silica have a strong influence on the aging properties.

In addition to this effect, silica can also affect the catalytic properties of the final catalyst. It can change all performance characteristics by changing the selectivity and/or the conversion rate. Depending on the particular application and one's own particular requirements regarding BET surface area, SiO ₂ and residual S content, the correct material and firing conditions must be individually adjusted to the respective proper application. In general, high calcination temperatures reduce both residual S levels and specific surface area.

Basically, for the purposes of this invention, any element that is able to stabilize an anatase-type polymorph can be used. Among numerous other elements for catalytic applications, typical elements are Si, Al, Zr [J Mater Sci (2011) 46:855-874].

The incorporation of such stabilizing elements can be achieved by a variety of different synthetic approaches. The following different methods are suitable for inventive material:

1. Deposition of SiO ₂ on TiO ₂

2. Co-precipitation or co-hydrolysis of TiO ₂ and SiO ₂

3. Mixing TiO ₂ sols and SiO ₂ sols

4. Treatment of TiO ₂ with SiO ₂ sols

5. Treatment of TiO ₂ with SiO ₂ precursor and consequently formation of SiO ₂ via hydrolysis and/or oxidation

6. Mixing TiO ₂ and SiO ₂ .

Thus, the present invention is directed to anatase form titanium dioxide which has a content of at least one compound selected from oxides of Si, Al, and Zr in an amount of 2-50

- 2 043234 wt.%, preferably 2-30 wt.%, in terms of oxides, based on the total mass of oxides, and which has a sulfur content of less than 150 ppm, preferably less than 100 ppm. and more preferably less than 80 ppm, referring to the total weight of the oxides.

The anatase material of the invention preferably has an alkali content, such as Na+, below 200 ppm, preferably below 100 ppm, to avoid any negative effects of alkali on the stability of the material during use.

According to the invention, the anatase form titanium dioxide is preferably obtained by the sulfate process, which is obtained in the form of titanium dioxide and its hydrated forms, including metatitanic acid. Metatitanic acid and hydrated forms of titanium dioxide, which are used synonymously herein, can be represented by the formula TiO( ₂ . _x )(OH) _2x with 0<x<1, also including titanium dioxide. Said metatitanic acid is then further processed to include stabilizing agents selected from Si, Zr and/or Al in the form of oxides and their hydrated forms, and then subjected to an calcination treatment to decompose a sulfur-containing compound such as sulfuric acid as a residue of the sulfate process . During calcination, the hydrated forms are converted to oxides and the hydrate content will be reduced to zero, which should be clear to a person skilled in the art.

The term anatase titanium dioxide or anatase titanium dioxide as used in accordance with the present invention means that at least 95% by weight, preferably 98% by weight and most preferably 100% of the titanium dioxide is present in the anatase form. Typically, the anatase phase has a crystal size of 5-50 nm. Thus, for the material of the invention, due to stabilization, the crystalline phase of the particles is most present in the anatase phase, after drying at 105° C. for at least 120 minutes before calcination, and also after calcination. Those. after removal of the base with linear movement, the ratio of the height of the most intense peak of the anatase structure (reflection (101)) to the height of the most intense peak of the rutile structure (reflection (110)) is at least 5:1, preferably at least 10:1. Most preferably, X-ray diffraction analysis exclusively shows anatase peaks. To determine the phase and size of the crystal according to Scherrer, in particular the crystalline modification (phase identification), X-rays are taken. For this, the intensity of the Bragg condition after diffraction on the planes of the crystal lattice of X-rays was measured relative to the diffraction angle 2θ. X-ray diffraction is characteristic of the phase.

Drying, as used in the context of this invention, means drying at temperatures above 105°C at atmospheric pressure. All large-scale industrial methods such as spin spray drying or spray drying can be applied, but drying is not limited to the methods mentioned.

Calcination, as used in accordance with this invention, means the treatment of stabilized anatase titanium dioxide at an elevated temperature of above 500°C, preferably from 800 to 1200°C, for a period of time sufficient to decompose the remaining sulfur-containing compound such as sulfuric acid and thus reducing the sulfur content to below 150 ppm, preferably less than 100 ppm. and more preferably less than 80 ppm, referring to the total weight of the oxides, preferably over a period of time from 30 to 1200 minutes, keeping the titanium dioxide in anatase form. The calcination may be carried out in a conventional atmospheric pressure calciner so that the sulfur-containing components may evaporate from the material.

Mass ratios, values in ppm or percent, as used in this invention, refer to the mass of the material after calcination.

Due to the high temperature treatment, agglomeration can occur which can be detrimental to downstream processes during catalyst formation. Thus, it may be necessary to deagglomerate the calcined material by grinding. Both wet or dry milling techniques can be applied, and ball milling or jet milling are common techniques.

An optional screening step may follow to ensure removal of coarse particles.

The resulting anatase form TiO ₂ can then serve as a catalytic base material, which can be further treated with at least one catalytically active metal compound selected from Co, Ni, Fe, W, V, Cr, Mo, Ce, Ag, Au, Pt, Pd, Ru, Rh, Cu, or mixtures thereof, resulting in a metal-laden material. A catalytically active metal precursor soluble in polar or non-polar solvents, selected from Co, Ni, Fe, W, V, Cr, Mo, Ce, Ag, Au, Pt, Pd, Ru, Rh, Cu, or mixtures thereof, can be used. The treatment of the base material with one precursor or its mixtures of catalytically active metals can be carried out by various methods. Typical methods include the impregnation by capacity method or the excess solvent method. Precipitation reactions such as hydrolysis can also be used to bring the catalytically active metal or its precursors into contact with the catalytic base material. Catalytic metal compound, which are not particularly limited and may be selected from Co, Ni, Fe, W,

V, Cr, Mo, Ce, Ag, Au, Pt, Pd, Ru, Rh, Cu, or mixtures thereof can be used in an amount to obtain a loading of 1-50 wt.%, preferably 5-30 wt.% or more preferably 8-20 wt.%, in terms of oxides from the total weight of the final material.

Thus, the present invention encompasses anatase form titanium dioxide which has a content of at least one compound selected from oxides of Si, Al, and Zr in an amount of 2-50 wt.%, preferably 2-30 wt.%, in terms of oxides , based on the total weight of the oxides, and which has a sulfur content of less than 150 ppm, preferably less than 100 ppm. and more preferably less than 80 ppm, referring to the total weight of the oxides;

anatase form titanium dioxide which has a content of at least one compound selected from oxides of Si, Al and Zr in an amount of 3-20 wt.%, more preferably 4-12 wt.% in terms of oxides based on the total mass of oxides and which has sulfur content less than 150 ppm, preferably less than 100 ppm. and more preferably less than 80 ppm, referring to the total weight of the oxides; anatase titanium dioxide which has a SiO ₂ content of 2-30 wt.%, preferably 3-20 wt.%, more preferably 4-12 wt.%, in terms of oxide, based on the total mass of oxides, and which has a content sulfur less than 100 ppm, preferably less than 80 ppm, referring to the total weight of the oxides and the process for producing anatase form titanium dioxide of the invention, which has a content of at least one compound selected from oxides of Si, Al, and Zr in an amount of 2-50 wt.%, preferably 2-30 wt.%, more preferably 3-20 wt.%, most preferably 4-12 wt.%, in terms of oxides, based on the total mass of oxides, and which has a sulfur content less than 150 ppm, preferably less than 100 ppm. and more preferably less than 80 ppm, referring to the total weight of oxides, where the titanium compound selected from metatitanic acid or titanyl sulfate is mixed with at least one compound selected from oxides and/or hydroxides of Si, Al and Zr or their precursors in an aqueous medium, precipitate at least one compound selected from the oxides and/or hydroxides of Si, Al and Zr, treat the resulting product to reduce its alkali content, if the alkali content is higher than 200 ppm, to a level of at most 200 ppm, referring to the total weight of the oxides, the product is optionally filtered, optionally washed with water and optionally dried, the product is then subjected to a calcination treatment at a temperature of more than 500°C, preferably in the range of 800-1200°C for a period of time sufficient, to decompose the remaining sulfur-containing compound, such as sulfuric acid, to a level below 150 ppm, preferably less than 100 ppm. and more preferably less than 80 ppm, referring to the total mass of oxides, preferably over a period of time from 0.5 to 12 hours, a method for producing an embodiment of the anatase form of titanium dioxide of the invention, in which metatitanic acid is mixed with a SiO ₂ precursor, at least one Si oxide and/or hydroxide is precipitated, the resulting product is treated to reduce its alkali content, if the alkali content is above 200 ppm, to a level of at most 200 ppm, referring to the total mass of the oxides, optionally filtering, optionally washing the resulting product and optionally drying the resulting product, subjecting the product to a calcination treatment at a temperature of more than 500°C, preferably in the range of 800-1200°C, for a period of time sufficient to decompose the remaining sulfur-containing compound, such as sulfuric acid to a level below 100 ppm, preferably less than 80 ppm, referring to the total weight of the oxides, preferably over a period of time from 0.5 to 12 hours,

A method for producing anatase titanium dioxide, in which a titanium compound selected from a TiO ₂ sol is mixed with a SiO ₂ sol by adjusting the pH to obtain a precipitate, the resulting precipitate is treated to reduce the alkali content, if the alkali content is higher than 200 ppm, referring to on the total weight of the oxides, up to a level of at most 200 ppm, referring to the total weight of the oxides, the resulting product is optionally filtered, optionally washed, optionally dried, and the resulting product is subjected to a calcination treatment at a temperature of more than 500° C., preferably in the range of 800 -1200° C. for a period of time sufficient to decompose the remaining sulfur-containing compound, such as sulfuric acid, to a level below 150 ppm, preferably less than 100 ppm. and more preferably less than 80 ppm, referring to the total weight of the oxides, preferably in the range of 800-1200°C, preferably over a period of time from 0.5 to 12 hours.

A method for reducing the sulfur content of stabilized anatase titanium dioxide, wherein the anatase titanium dioxide, which contains the stabilizing agent, is treated at a temperature of more than 500°C, preferably in the range of 800-1200°C, for a period of time sufficient to decompose the remaining compound containing sulfur, such as sulfuric acid to

- 4 043234 levels below 150 ppm, preferably less than 100 ppm. and more preferably less than 80 ppm, referring to the total weight of the oxides, preferably over a period of time from at least 30 minutes, in which the stabilizing agent is selected from the oxides of Si, Al and Zr and in which the content of the stabilizing agent is in in the range of 2-50 wt.%, preferably 2-30 wt.%, in terms of oxides, based on the total mass of oxides.

The use of an annealing treatment at a temperature of more than 500°C to reduce the sulfur content of stabilized anatase titanium dioxide, which has a content of at least one compound selected from oxides of Si, Al and Zr in an amount of 2-50 wt.%, preferably 230 wt. %, in terms of oxides, based on the total mass of oxides, to a level below 150 ppm, preferably less than 100 ppm. and more preferably less than 80 ppm, referring to the total weight of the oxides.

The use of the anatase form titanium dioxide of the invention, obtained according to the methods of the invention, as a catalyst or catalyst base in catalytic reactions, gas-liquid reactions such as, in particular, Fischer-Tropsch catalysis, selective catalytic reduction (SCR), catalytic oxidation, photocatalysis, hydrotreating catalysis, catalysis Claus, phthalic acid catalysis.

A catalyst, or catalyst base, comprising the anatase form of titanium dioxide of the invention, obtainable according to the methods of the invention.

The invention is further illustrated by the following examples and Comparative examples.

experimental part

Analytical Methods

TiO ₂ polymorph definition:

X-ray diffraction analysis is used to determine the TiO ₂ polymorph. It is done in a conventional x-ray diffraction scheme, where the intensities of the diffraction x-rays are measured relative to the diffraction angle 2θ. An evaluation of the X-ray diffraction image is made using the JCPDS database (JCPDS-data base - Joint Committee for Powder Diffraction Standards). Typical analysis conditions are: 2θ = 10-70°, steps 2θ = 0.02°, measurement time per step: 1.2 s.

Determination of SiO ₂ content:

The material is leached into H ₂ SO ₄ /(NH ₄ ) ₂ SO ₄ followed by dilution with deionized water. The residue is washed with sulfuric acid and the SiO ₂ content is obtained by weighing the filter cake after combustion.

Determination of TiO ₂ content:

The leaching of the material is done with H ₂ SO ₄ /(NH ₄ ) ₂ SO ₄ or KHSO4. Then Ti ⁴⁺ is reduced from Al to Ti ³⁺ and, finally, the content of TiO ₂ is obtained by titration with iron(III) ammonium sulfate. (NH4SCN as indicator)

S-content definition:

The S-content is obtained with a Euro EA elemental analyzer (Hekatech). The sample is burned in an oxygen atmosphere and the gases are analyzed by gas chromatography. S-contents are calculated from the areas of the chromatograms.

Determination of specific surface area

The specific surface area was determined by the nitrogen adsorption method according to DIN ISO 9277 (BET method). 5 points were evaluated between 0.1 and 0.3 p/r ₀ . An Autosorb 6 or 6B instrument (Quantachrome GmbH) was used.

Example 1

SiO ₂ (13.1 wt.%) was introduced by coprecipitation of TiO ₂ and SiO ₂ from solutions of TiOSO ₄ - and Na ₂ SiO ₃ -. 352 L of Na ₂ SiO ₃ solution (94 g/L SiO ₂ ) and 2220 L of TiOSO ₄ solution (103 g/L TiO ₂ ) were pumped simultaneously over a period of 270 minutes into a stirred chemical reactor containing 960 L of water. During the reaction, the pH was kept at 5 with an ammonia solution. After the addition was complete, the reaction was heated for 1 h to 75°C to complete the reaction. Subsequently, hydrothermal aging was carried out for 4 hours at 9.5-10 bar and 170-180°C. Finally, the resulting reaction mixtures are filtered and washed with deionized water. The product was obtained after spray drying at 350°C. BET is 100 m ² /g and the S content is 4000 ppm.

Example 2

A SiO ₂ /TiO ₂ powder having a SiO ₂ content of 8.5 wt.% was prepared based on metatitanic acid and Na ₂ SiO ₃ followed by a sequence of pH adjustment steps and a final filtration and washing of the thus obtained material with deionized water. The SiO ₂ /TiO ₂ powder obtained after drying had a BET of 334 m ² /g and a sulfur content of 1100 mg/kg.

Example 3

943 g of metatitanic acid (29.2 wt.% TiO ₂ ) was diluted with deionized water to 150 g/l. Added 78.5 g of ZrOCl ₂ -8H ₂ O and raised the temperature to 50°C. Next, 68 ml of sodium silicate was added

- 5 043234 (Na ₂ SiO ₃ , 358 g/l SiO ₂ ). After completion of the addition, aqueous NaOH (50 wt.% NaOH) was added until a pH of 5.25 was reached at 50°C. The white precipitate was filtered and washed with deionized water until the conductivity of the filtrate was below 100 μS/cm. The remaining filter cake was dried at 105°C. The BET surface area of the product was 329 m ² /g and S>1000 ppm. The contents of SiO ₂ and ZrO ₂ were 7.7% and 10.8% by weight, respectively.

Example 4

Example 4 was prepared in the same way as example 3, except that the addition sequence of ZrOCl ₂ -8H ₂ O and sodium silicate was changed. For example 4, Na ₂ SiO ₃ solution was added first, followed by ZrOCl ₂ -8H ₂ O. The contents of SiO ₂ and ZrO ₂ were 6.8 and 10.4 wt.%, respectively. The BET surface area was 302 m ² /g and the S content was 3300 ppm.

Comparative example 1.

Hombikat 8602 (commercial product). The BET surface area was 321 m ² /g and the S content was 4700 ppm.

Comparative example 2.

Commercially available Hombikat 8602 was purified by NaOH neutralization and washed with deionized water. The resulting sulfur content before calcination was 0.2 wt% (2000 ppm) and a BET surface area of 351 m ² /g.

Comparative example 3.

Rutile suspension was prepared according to example 1a in DE10333029A1. NaOH was added thereto to pH 6.0-6.2 at 60° C., the solid was filtered and washed with deionized water until the filtrate conductivity was below 100 μS/cm. The resulting filter cake was resuspended and spray dried. The BET surface area was 105 m ² /g and the S content was 70 ppm.

Comparative example 4.

Commercially available Aerosil P25 from Evonik was used as received. The BET surface area was 55 m ² /g and S<30 ppm.

Comparative example 5.

300 ml of oxytitanium chloride solution (145 g/l TiO ₂ ) was diluted with deionized water to 3 liters. As a result, 4 g of oxalic acid dihydrate was added and a white solid precipitated by treating the reaction mixture with an aqueous solution of 15% NaOH while keeping the temperature below 20°C. The final pH was 6.2. After filtration, the white solid was washed with deionized water until the filtrate had a conductivity < 100 µS/cm. Resuspension and spray drying gave the final product with BET: 359 m ² /g and S < 30 ppm.

Calcination

All calcinations were performed in a muffle furnace. The materials were placed in ceramic boxes for calcination (corundum) and heated for 1 h at 1000°C. The resulting powders were carefully ground and homogenized before X-ray diffraction, BET and SO4 analyses. The BET specific surface area and sulfur content of various SiO ₂ -treated anatase TiO ₂ bases before and after aging for 1 h at 1000° C. are shown in Table 1. 1.

Fischer-Tropsch Synthesis (FTS):

The FTS test was carried out using a 32-fold parallel reactor. The powders were compacted and consequently crushed. Samples were loaded with Co(NO ₃ ) ₂ by impregnation in order to obtain a Co loading of 10 wt.%, based on the total weight of the dried and reduced catalyst. For catalytic testing, a 125-160 µm cut was used and each catalyst block was filled with an amount of catalyst to provide 40 mg Co-metal loading. Before the catalytic test, the catalyst was activated in dilute H ₂ (25% in Ar) at 350° C. (heating rate 1K/min). The catalytic test was then carried out at 20 bar with a feed rate of 1.56 l/h per reactor. The H ₂ /CO ratio was 2 (10% Ar in feed) and the catalytic test temperature was 220°C.

In the Fischer-Tropsch synthesis, CO and H ₂ are contacted at elevated pressure and temperature in order for the hydrocarbons to react. Evonik P25 is a known TiO ₂ based catalyst base for this application. In order to have a fully economical SFT process, the catalysts must satisfy the following properties:

1. High conversion rate ^from '% ¹ - ^{to %} )

2. High productivity ^ ^{5+ in} 2c ₅₊ /(£cob))

3. Low selectivity for methane ⁱⁿ °°1 _l and „ „ ____ _{_} _ CO ₂ (Srn in %)

4. Low ^LUe selectivity

The purpose of SFT is to obtain long-chain hydrocarbons. Of particular interest are hydrocarbons with more than 5 carbon atoms, because they serve as a starting material, for example, for high-quality diesel fuel, kerosene or long-chain waxes. Syngas (H2/CO mixture) is often produced from methane by reacting it with H2O to yield CO and _H2 (steam reforming). The reverse reaction should reduce the amount of CO and H2 available for the SFT reaction. high

- 6 043234 selectivity for CH4 in FTS indicates a high degree of conversion of CO and H ₂ to CH4 and vice versa. Therefore, CH4 selectivity should be kept as low as possible. Additionally, under the reaction conditions, CO can react with H2O to form CO2 and H2 (steam shift reaction). This will reduce the concentration of carbon atoms available for SFT. High CO2 selectivity indicates high CO to CO2 conversion and vice versa. Thus, CO2 selectivity should be low for FTS catalysts.

In addition, the CO conversion rate (the amount of CO converted) should be high, and furthermore, the amount of hydrocarbons with more than 5 carbon atoms should also be high. The last parameter is indicated by the amount of hydrocarbons with more than 5 carbon atoms produced within one hour per gram of cobalt metal.

Regarding all these four parameters, Table. 3 clearly shows that inventive products exhibit excellent properties when used as catalyst bases in FTS.

Table 1

Sample Before calcination After calcination at 1000°C 1h BET m ² /g S mg/kg ΤΪΟ2- Polymorph BET m ² /g S mg/kg TiO2 Polymorph Example 1 100 4000 Anataz 60 40 Anataz Example 2 334 1100 Anataz 70 < 30 Anataz Example 3 329 > 1000 Anataz 77 < 30 Anataz Example 4 302 3300 Anataz 52 < 30 Anataz Comparative Example 1 321 4700 Anataz 3 < 30 Rutile Comparative Example 2 351 2000 Anataz 3 < 30 Rutile

Table 2. Overview of the analysis of the fundamentals of materials used for SFT

BET m ² /g S mg/kg T1O2 Polymorph Example 2 (after 1h 1000°C) 70 < 30 Anataz Example 3 (after 1h 1000°C) 77 < 30 Anataz Example 4 (after 1h 1000°C) 52 <30 Anataz Comparative Example 3 105 70 Rutile Comparative Example 4 55 < 30 Anatase/Rutile Comparative Example 5 359 < 30 Anataz

Table 3. Fischer-Tropsch Synthesis Data of the Inventive and Comparative Examples

^co % % Ys.LysoCh %o ₃ % Example 2 54 7.2 3.46 0.6 Example 3 55.2 7.8 3.35 0.7 Example 4 52.9 7.7 3.3 0.6 Comparative Example 3 12.6 9.4 0.74 But. Comparative Example 4 20.6 9.5 1.18 But. Comparative Example 5 0.5 31.3 0.02 But.

n.d.=not determined because CO conversion was very low.

The above results of the Inventive Examples and Comparative Examples as well as the catalyst tests show that the combination of properties of the materials of the invention, i. high specific surface area, anatase content and low sulfur content results in their excellent catalysis properties.

Claims (10)

1. Anatase titanium dioxide, which has a BET surface area > 40 m ² /g, the content of at least one compound selected from the oxides of Si, Al and Zr in the amount of 2-50 wt.%, in terms of oxides, of the total mass of oxides and which has a sulfur content of less than 150 ppm. relative to the total weight of the oxides, wherein the titanium dioxide is obtained by the sulfate method and wherein at least 98 wt.% of the titanium dioxide is present in the anatase form. 2. Anatase titanium dioxide according to claim 1, which has a content of at least one compound selected from oxides of Si, Al and Zr in an amount of 3-20 wt.%, in terms of oxides, based on the total mass of oxides and which has a content sulfur less than 150 ppm relative to the total mass of oxides. 3. The anatase titanium dioxide according to claim 1, which has a SiO ₂ content of 2-30 wt.%, in terms of oxide, based on the total weight of oxides, and which has a sulfur content of less than 100 ppm. relative to the total mass of oxides. 4. A method for producing anatase titanium dioxide, which has a BET surface area > 40 m ² /g, the content of at least one compound selected from the oxides of Si, Al and Zr in the amount of 2-50 wt.%, in terms of oxides, of the total mass of oxides and which has a sulfur content of less than 150 ppm. relative to the total mass of oxides, according to claim 1, in which - 7 043234 a titanium compound selected from metatitanic acid or titanyl sulfate obtained by the sulfate method is mixed with at least one compound selected from oxides and/or hydroxides of Si, Al and Zr or their precursors in an aqueous medium, at least one is precipitated a compound selected from oxides and/or hydroxides of Si, Al and Zr is filtered and the resulting product is washed with water to reduce the alkali content to a level of at most 200 ppm, relative to the total weight of the oxides, the product is dried, the product is then subjected to an calcination treatment at a temperature of more than 500°C, for a period of time sufficient to decompose the remaining compound containing sulfur, to a level below 150 ppm. relative to the total mass of oxides. 5. The method for producing anatase titanium dioxide according to claim 4, wherein the metatitanic acid obtained by the sulfate method is mixed with the SiO ₂ precursor, at least one oxide and/or Si hydroxide is precipitated, and the resulting product is treated to reduce the alkali content to the level at most 200 mln. relative to the total mass of oxides, filtered, washed the obtained product and dried the obtained product, then subjected the product to an calcination treatment at a temperature of more than 500° C. for a period of time sufficient to decompose the remaining sulfur-containing compound to a level below 100 ppm. relative to the total mass of oxides. 6. The method for producing anatase titanium dioxide according to claim 4, wherein the titanium compound selected from the TiO ₂ sol is mixed with the SiO ₂ sol by adjusting the pH to obtain a precipitate, the resulting precipitate is treated to reduce the alkali content relative to the total mass of oxides to a level of at most more than 200 mln. relative to the total weight of the oxides, the resulting product is filtered, washed, dried, and the resulting product is subjected to an calcination treatment at a temperature of more than 500°C for a period of time sufficient to decompose the remaining sulfur-containing compound to a level below 150 ppm. relative to the total mass of oxides. 7. A process for reducing the sulfur content of stabilized anatase form titanium dioxide, wherein the stabilized anatase form titanium dioxide is treated at a temperature of more than 500° C. for a period of time sufficient to decompose the remaining sulfur compound to a level below 150 ppm. relative to the total weight of the oxides, for a period of time from at least 30 min, in which, after treatment, the stabilized anatase form titanium dioxide has a BET surface area > 40 m ² /g, in which the stabilizing agent is selected from oxides of Si, Al and Zr, in in which the content of the stabilizing agent is in the range of 2-50 wt.%, in terms of oxides, based on the total mass of oxides and in which at least 98 wt.% titanium dioxide is present in anatase form. 8. Application of an annealing treatment at a temperature of more than 500° C. to reduce the sulfur content of the stabilized anatase form titanium dioxide to below 150 ppm. relative to the total weight of the oxides, in which, after the calcination treatment, said stabilized anatase form titanium dioxide has a BET surface area > 40 m ² /g, and in which at least 98 wt.% of the titanium dioxide is present in the anatase form. 9. The use of anatase titanium dioxide according to any one of claims 1 to 3 as a catalyst or catalyst base in catalytic reactions, gas-liquid reactions selected from the group of Fischer-Tropsch catalysis, selective catalytic reduction (SCR), catalytic oxidation, photocatalysis, hydrotreating catalysis , Claus catalysis, phthalic acid catalysis. 10. A catalyst or catalyst base comprising anatase titanium dioxide according to any one of claims 1-3.