WO2006053675A1 - Method for producing elemental halides - Google Patents

Abstract

The invention relates to a method for producing elemental halides, which is characterized in that during a first step, a mixture consisting of a material containing the corresponding element and of carbon or carbon-containing material is produced, and this mixture is brought into contact with a hydrogen halide, which is gaseous under the reaction conditions, and is then heated.

Description

 Process for the preparation of element halides

A process for the preparation of elemental halides is described, which is characterized in that in a first step, a mixture of a material containing the respective element and carbon or carbonaceous material is prepared and brought this mixture with a gaseous under the selected reaction conditions hydrogen halide in contact and heated.

Elemental halides are compounds of elements with the halogens fluorine, chlorine, bromine, iodine or mixtures of these halogens. The element-halogen bond here ionogenic character, such as a halogen-alkali metal bond, such as NaCl, or predominantly covalent character as for metal-halogen bonds, such as SiCl ₄ , or non-metal halide bonds, such as PCl ₃ , have.

Elemental halides are widely used in the art. Some elements, such as aluminum, titanium, boron or silicon, are derived from element halides. Also, in some elements, a halogenating oxidation and subsequent dehalogenating reduction serve to present these elements in particularly high purity. Optionally, the elemental halogen compounds in this case by sublimation, such as AlCl ₃ , or distillation, such as TiCl4, are additionally purified. The dehalogenation can be carried out, for example, by means of hydrogen, such as, for example, BCI ₃ , or by thermal decomposition, such as, for example, decomposition of BBr ₃ to tungsten wire. As a result, element halides are also important starting materials for CVD or similar processes. Further, elemental halides are fundamental building blocks for, for example, technically and synthetically important catalysts, such as Friedel-Crafts electrophilic aromatic substitution catalysts, alkylation, acylation, or Ziegler-Natta catalysts for polymerizations, to form element-to-member bonds, such as by Wurtz couplings , Grignard reactions, salt metathesis to elemental oxygen, elemental phosphorous, elemental nitrogen, elemental boron, elemental sulfur bonds,

10 and intermediates and adjuvants, such as AICI ₃ in pharmaceuticals, cosmetics, textiles or as flocculants in water treatment. As technically particularly relevant elemental halides to tetrachlorotitanium and silane as intermediates of titanium dioxide production and

15 of the production of fumed silica are highlighted.

In the prior art, different methods for the preparation of elemental halides are known, which can be combined into several groups.

All known element halides can be produced by reacting the elements with the respective halogen, if appropriate with heating. Of some elements is also one

! 5 Reaction with hydrogen halide known to be in the

In general, additional hydrogen is released. In this reductive acting atmosphere, the elemental halides are usually obtained in a relatively low oxidation state. To get to elemental halides in one

> 0 higher oxidation state, it is possible in some cases to implement this with halogen instead of hydrogen halide or subsequently oxidize the lower element halides with halogen, especially chlorine. It is too it is possible to convert element halides of a high oxidation state with hydrogen or similar reductive halogen-withdrawing reagents into a lower oxidation state. 5

Examples of such reactions are:

Fe + 2 HCl → FeCl ₂ + H ₂ 2 Fe + 3 Cl ₂ → 2 FeCl ₃ 10 PCl ₃ + Cl ₂ → PCl ₅

2 BCl ₃ + "Chlorine-withdrawing reagent" → B ₂ Cl ₄

Wherein, in the last-mentioned equation, the chlorine-withdrawing reagent may be copper or mercury.

15

Another known method is carbochlorination. By "carbochlorination" is meant a reaction of preferably elemental oxides with carbon and chlorine with the introduction of thermal energy, and for some elements as well

? 0 a carbochlorination with hydrogen chloride known.

Such reactions are described for example in the patents JP62-143813 A2 and US 4,576,812:

> 5 TiO ₂ + 2 Cl ₂ + 2 C → TiCl ₄ + 2 CO

Al ₂ O ₃ + 3 Cl ₂ + 3 C → 2 AlCl ₃ + 3 CO BaSO ₄ + C + Cl ₂ → BaCl ₂ + CO ₂ + SO ₂

One method, which is based on the carbochlorination, is iθ the chlorinating roast. In chlorinating roasting, element compounds are mixed with chlorine-containing compounds and optionally heated in the presence of carbon or carbon-containing compounds. used Chlorine-containing compounds are, for example, tetrachlorosilane or carbon, sodium chloride or chlorine-containing sulfur compounds, such as thionyl chloride and sufururic chloride.

Thus, according to H.F. Johnstone et al, in Ind. Engg. Chem. 34 (1942) 280, mixtures of chromium iron with sodium or potassium chloride with a sulfur dioxide / air mixture to convert water-soluble chlorides and sulfates. Rauter (Liebigs Ann. 270, 1892, 236) describes the conversion of cadmium oxide with silicon tetrachloride to cadmium chloride:

2 CdO + SiCl ₄ → 2 CdCl ₂ + SiO ₂ .

Likewise, cadmium chloride may be cadmium oxide according to:

CdO + SOCl ₂ → CdCl ₂ + SO ₂

using the method described by North and Hagemann in J. Am. Chem. Soc. 35 (1913) 2088. For example, US Pat. Nos. 2,895,796 and 3,652,219 disclose a process for producing iron (II) chloride from iron sulfide according to:

FeS ₂ + SCl ₂ → FeCl ₂ + 3 s.

Furthermore, for example, in the patents US 4,209,501 and US 4,576,812 a process for the preparation of iron (II) chloride from iron (III) chloride according to:

ZnS + 2 FeCl ₃ → ZnCl ₂ + 2 FeCl ₂ + S

described. Last mentioned is the direct reaction of elemental compounds with hydrogen halides to form elemental halides and release of

Hydrogen compounds according to the following examples:

SiO ₂ + 4 HF → SiF ₄ + 2H ₂ O, As ₂ O ₃ + HCl → AsCl ₃ + H ₂ O and SnS + 2 HCl → SnCl ₂ + H ₂ S.

In the prior art, different embodiments for the preparation of elemental halides are known. A commonly used in a comparable manner and described for example in the patent US 4,083,923 process under the reaction conditions solid starting compounds under the reaction conditions to gaseous element halides, a disclosed for example in the patent US 4,576,812 process passes from solid starting materials under the reaction conditions solid element halides. Furthermore, processes are known in which the reaction of the starting compounds takes place in the liquid phase or in a suspension, for example in a molten salt bath. A process disclosed, for example, in US Pat. No. 4,039,648 leads to gaseous elemental halides under the reaction conditions, while processes described in the patents US Pat. No. 4,209,501 or US Pat. No. 4,597,840, for example, produce dissolved products in the liquid phase.

The prior art also describes reactions of mixtures of different elemental compounds, such as clays or bauxite, to form mixtures of elemental halides, subsequently by fractional condensation, filtration or distillation can be purified. In addition, for example, processes disclosed in US Pat. Nos. 3,935,297, 4,083,923 or WO2004 / 063096 describe the possibility of removing impurities in the desired target product by selective reaction.

The methods described in the prior art, which do not emanate from the elements, thereby have the partial disadvantage that they convert the contained element only to a small extent in elemental halides. To the

Catalysts are often used to increase yields or to improve the reaction rates, as for example in US Pat. No. 1,565,220 by addition of sulfur in the carbochlorination of alumina for accelerating the reaction and US Pat. No. 4,083,927 by addition of

BCI ₃ in the carbochlorination of kaolin-containing raw materials to accelerate the reaction to AICI ₃ over that to SiCl ₄ described. Furthermore, some of these methods result in occupational-medical and environmentally toxic by-products. For example, the carbochlorination of elemental oxides with chlorine gas can produce dichloroketone (phosgene). In order to minimize the release of phosgene, the chlorine gas used must be reacted as completely as possible in the reactor, as described, for example, in patents JP60-112610 A2 and JP60-118623 A2:

SiO ₂ + 2C + 2Cl ₂ → SiCl ₄ + 2CO CO + Cl ₂ → COCl ₂

The present invention is based on the object

To provide processes for the production of elemental halides, which is characterized with respect to the starting materials used by a particularly great versatility, without addition Catalysts and avoids the formation of harmful by-products.

This object is achieved by a method for producing element halide, characterized in that a mixture of a material comprising the element with carbon or carbonaceous material is brought under heating with a gas stream containing under the reaction conditions gaseous hydrogen halide in contact dissolved.

Conventional sources of energy can be used to heat the mixture. Non-limiting examples are heating by means of resistance heating or by solar thermal means. In a further embodiment of the method according to the invention, the mixture is heated by generating an alternating electromagnetic field, in particular microwave energy. Experiments have shown that when using an alternating electromagnetic field, preferably microwave radiation, as an energy source for carrying out the method according to the invention can be used on any element-containing compounds. The carbon or carbonaceous material used must be in a form suitable for converting electromagnetic waves into thermal energy, i. to be thermally excited by alternating electromagnetic fields.

For carrying out the process according to the invention no catalyst is required, whereas this is often the case in the prior art. The process of the present invention makes no claims to the element-containing and carbonaceous material used. However, preference is given to using elemental oxides or elemental sulfides and mixtures of these oxides or sulfides with contaminating compounds, in particular with the highest possible elemental content. Non-limiting examples of useful mixtures include titanium-containing wastes of titanium dioxide production, silicon-containing wastes such as rice ash, and carbonaceous residues of combustion or pyrolysis processes. These materials are currently problematic materials that have to be disposed of in a complicated manner.

Also possible is the recycling of glasses, the digestion of aluminous silicates or mixtures of aluminas with silica and iron oxides, such as bauxite.

Some suitable starting materials are listed in Table 1.

Table 1

Die Elementhalogenide können gegebenenfalls nach der Halogenierung der Mischungen durch bekannte physikalische oder chemische Verfahren getrennt werden, beispielsweise durch Destillation von flüssigen oder gasförmigen Elementhalogeniden, durch Sublimation von festen

The elemental halides may optionally be separated after halogenation of the mixtures by known physical or chemical methods, for example by distillation of liquid or gaseous element halides, by sublimation of solid

Element halides or filtration to separate liquid or gaseous elemental halides from solid elemental halides.

It is also possible to react starting materials or mixtures thereof which contain the elements in specific proportions. As a result, for example, a doping ratio for a subsequent deposition process can be preset.

In the process according to the invention, it is possible to prepare elemental halides which are liquid, gaseous or solid under the reaction conditions. Thus, the process is characterized by particularly great versatility.

The method may be coupled with a deposition of the elemental halides by means of hydrogen. The hydrogen produced during the use of hydrogen halide for halogenation can be used for this purpose.

The released hydrogen may alternatively be used to recover some of the energy needed for the process. In comparison with processes in which halogenation takes place from the elements, energy and production costs can be saved with the one-step process presented here. The production of the Elements omitted. Formally, the process often proceeds without altering the oxidation state of the element.

In a particularly preferred variant of the invention presented here is used as the halogen-containing compound

Hydrogen chloride used. In addition to the avoidance of phosgene hydrogen chloride is also technologically preferable due to its much lower boiling point compared to chlorine, since it is easier to separate from the desired elemental halides. Hydrogen chloride is also advantageous for reactor construction since hydrogen chloride acts less oxidatively on the reactor materials than chlorine. Additionally, hydrogen chloride is technically available at most chemical manufacturing sites.

The use of hydrogen halide for the reaction of in particular elemental oxides has the disadvantage that due to the hydrogen bound to the halogen during the implementation of the reaction, water is formed, which can rehydrolysis a generated hydrolysis-sensitive element halide. In a further development of the process according to the invention, during the preparation of hydrolysis-sensitive elemental halides, such as, for example, tetrachlorotitanium, by choosing a suitable temperature, preferably above 800 ^° C., the water gas equilibrium can be:

H ₂ O + C 1 CO + H ₂

in favor of carbon monoxide and hydrogen. The water is deprived of equilibrium and hydrolysis does not take place. The resulting Carbon monoxide-hydrogen mixture can be used energetically or chemically.

The method according to the invention is not limited to the type of material used containing the element, but also to the specific surface area of this material. Also, there are hardly any restrictions on the type and specific surface area of the carbon or carbonaceous material used.

Preferably, starting materials are chosen for the process according to the invention, which can be easily mixed technically. These may be, for example, ground products of the element-containing or carbon-containing materials which are subjected to a milling process separately or already premixed. In a further embodiment, the components of the mixture or the mixture itself may be porous. Particularly preferably, the mixture should have such a large pore space that it can be penetrated by the gaseous halogen or the gaseous halogen compound, thus promoting the reaction taking place. Compact materials having a low specific surface area, for example coarsely comminuted natural minerals such as bauxite, ilmenite, quartz or sand, can also be reacted with the method according to the invention.

The carbon or the corresponding carbonaceous material used in the method according to the invention acts, on the one hand, optionally as a reducing agent for the element-containing material, on the other hand in the embodiment with the action of electromagnetic alternating fields, such as microwave irradiation, as a heating element within the mix. Furthermore, the carbon used traps water by reduction to hydrogen and thus prevents water, which can be introduced, for example, by the starting materials or is liberated in the reaction, adversely affecting the production of hydrolysis-sensitive element halides.

The element halide can be obtained almost quantitatively. In the method according to the invention, any compound containing the element can be used.

In all embodiments of the process according to the invention, catalysts can be added to the reaction mixture in order to increase the reaction rates or

Selectivity to improve the desired elemental halide, especially when contaminated element-containing compounds are used in the process according to the invention. The catalysts can be introduced into the reaction mixture before entry into the reactor, as solids, liquids or gases are fed separately during the reaction or pass as gas in a mixture with the hydrogen halide in the reaction space.

In a first embodiment of the invention

Method, the material containing element is preferably used in the form of particles, such as powder, grains, spheres or granules, in order to allow a good passage of the gaseous halogen or the gaseous halogen compound.

A preferred molar ratio of element to carbon can not be universally defined as the process divided into several subregions, which require different minimum amounts of carbon for the quantitative production of the desired elemental halide:

1. Reactions where carbon is not considered as

Reducing agent acts against the elemental compound; the carbon or carbonaceous material is consumed only by reacting with impurities or by-products of halogenation, and functions mainly as a filler or, in embodiments having alternating electromagnetic fields, also mainly as a heating element. Therefore, to produce a homogeneous reaction mixture, only mixing with the supplemented element-containing starting material must take place again and again. The molar ratio of element to carbon is preferably 100: 1 to 1: 2.

2. Carbon serves as a reducing agent of pure elemental compounds, here enough carbon must be present to ensure the stoichiometric reaction of the element. In particular, in embodiments with the action of alternating electromagnetic fields, an excess of stoichiometry is advantageous so that heat can be generated consistently. The molar ratio of element to carbon is preferably 1: 1 to 1:10 here.

3. Carbon is used to reduce contaminated elemental compounds. In this case not only must sufficient carbon be present to produce the desired element halide, but, if complete conversion of the starting material is desired, the impurities must also be quantitatively reacted; by the choice of suitable reaction parameters is a Of course, selective reaction also possible, especially if, for example, in accordance with the patent US 4,083,927 in the implementation of the method according to the invention catalysts are used. In this third case, the molar ratio of carbon to all the halide compounds produced is preferably 10: 1 to 1: 1.

The reaction temperatures are for the preparation of hydrolysis-sensitive element halides preferably more than 700 ⁰ C, more preferably more than 800 ⁰ C.

The hydrogen halide gas used is preferably hydrogen chloride gas (HCl). Hydrogen fluoride (HF) can also be used. The halogen-containing gas may be used in pure form or together with a carrier gas. When

Carrier gases are CO ₂ or inert gases selected from the group containing helium, nitrogen and argon, and mixtures thereof are preferred.

In a preferred embodiment, the material containing the element consists of SiO _x sources which are selected from the group comprising highly dispersed silicic acid, preferably having a surface area of at least 50 m ² / g, preferably of at least 250 m ² / g, measured using the BET method, quartz flour preferably having micron a mean particle size of at least 0.1, preferably at least 1 micron, and preferably having a theoretical specific surface area of at least 0.1 m ² / g, preferably 0.5 m ² / g, silica sand having an average Particle size of at least 0.005 mm, preferably 0.1 mm and a theoretical specific surface area of at least 10 cm ² / g, preferably 50 cm ² / g, desert sand preferably having a particle size of 0.001 to 1 mm, bottle glass, such as soda-lime glass , preferably pounded or milled, quartz glass, mica and SiO 2 powder preferably having a particle size of 0.01 microns to 0.1 mm.

Here, the method has not only in terms of the type of SiO _{x used} , but also in terms of the design of the particles, such as their shape and grain size, of this material hardly limits if the SiO _x material used only with the Carbon or the carbonaceous material mix. Also, with respect to the kind and grain size of the carbon or carbonaceous material used, there are hardly any limitations if the above-mentioned mixing is possible. However, the mixture should preferably have such a large pore space that it can be permeated by the hydrogen halide to thereby promote the reaction taking place.

The molar ratio SiO _x to carbon is preferably 1: 1 to 1:10, particularly preferably 1: 2 to 1: 7.

The silicon tetrahalide can be obtained almost quantitatively. Almost any SiO _x source can be used in the method according to the invention. Expediently, SiO _{2 is} used, but it is also possible to use SiO. Suitable SiO _x sources are, for example, sand, such as desert or quartz sand, glass, rice ash and silicates. It is therefore possible to use all materials which consist of SiO _x or contain SiO _x , and also corresponding silicates.

In a preferred embodiment of the method according to the invention, for example, desert sand is used as a suitable source of SiO _x , since this is available in large quantities stands. Such a desert sand usually has a SiO ₂ content of greater than 80%.

An exemplary percentage composition of desert sand is listed in Table 2.

Table 2

SiO _x or the SiO _x -containing material is preferably used in the form of particles, such as, for example, powders, granules, spheres or granules, in order to allow good mixing and good passage of the gaseous hydrogen halide.

The as a reducing agent and optionally as

Heat transfer agent for the production of element halide acting carbon or the corresponding carbonaceous material is also preferably particulate, for example in the form of powder, grains, spheres or granules, used to allow good mixing and passage of the halogen gas or the halogen compound. The nature of the used material is not critical. A particularly preferred material is crushed activated carbon.

Pelleting or granulation of the mixture of elemental compound and carbonaceous material results in particularly intimate contact between the two components and, at the same time, allows greater gas flow rates due to the porosity of the beds formed from the pellets or granules, so that higher reaction rates than in the case of mixed powders are observed. The

Pelleting or granulation may be accomplished by adding up to 20% binder to the mixture of elemental compound and carbonaceous material. Suitable binders are generally carbon-containing compounds such as polyvinyl alcohol, polyvinyl acetate, cellulose, starch or molasses as well as elemental compounds.

In a further embodiment of the process according to the invention, the element-containing material is added in liquid form or as gas, optionally at elevated temperature, to the solid and heated carbon or carbonaceous material.

In a further embodiment of the method according to the invention, the carbonaceous material is introduced into the reaction space in liquid form or as gas, optionally at elevated temperature.

In a further embodiment of the method according to the invention with an alternating electromagnetic field as an energy source, at least the portion of the carbonaceous material serving as reducing agent is in liquid form or as gas, optionally with increased Temperature, introduced into the reaction space. If carbon or a carbonaceous material which can be heated by an electromagnetic alternating field is already present in the reaction space, then it is not necessary that the liquid or gaseous carbonaceous material used as reducing agent can likewise be heated by electromagnetic alternating fields.

In a further embodiment of the method according to the invention with an alternating electromagnetic field as an energy source, the carbon used or the carbonaceous material used within the reaction space by the action of an electromagnetic alternating field on the contained in the reaction space

Substance mixture transferred into a form that can be heated by the electromagnetic alternating field.

In embodiments of the method according to the invention with an alternating electromagnetic field as an energy source, during the action of the field, ignition and stabilization of a plasma within the reaction space may occur.

In embodiments of the method according to the invention with an alternating electromagnetic field as an energy source, in which the carbon or the carbonaceous material acts not only as a heating element but also as a reducing agent and is thus consumed during the reaction, an over-stoichiometric addition is advantageous.

The inventive method can in addition to the described embodiment in a fixed bed reactor in reactors with a moving bed of the reaction mixture are carried out, such as stirring the bed, moving the bed by vibration or using a fluidized bed process. In particular, fluid bed arrangements are appropriate for continuous operation.

The inventive method is preferably used for the preparation of element chlorides using hydrogen chloride as the reaction gas. With the method according to the invention, in particular the naturally occurring materials, such as desert sand or bauxite, can be used without extensive pretreatment, so that the inventive method in addition to its versatility is characterized by easy handling and low costs.

The invention will be described below with reference to technically relevant embodiments. In particular, element-oxygen combinations have been used which have a high element-oxygen-binding enthalpy. These are listed in Table 3.

Table 3

Beispiele

Examples

The apparatus and reaction materials used are made of quartz glass due to their availability and temperature resistance. This is attacked under the reaction conditions of HCl, but the reaction rate is significantly reduced by the low surface area compared to the powdered or granular reaction mixtures, so that destruction of the silica glassware during a single reaction was not observed. According to GC / MS analysis, phosgene could not be detected as a by-product in any of the examples below.

example 1

4 g of quartz powder (mean particle size 3 .mu.m, corresponding to a theoretical specific surface area of 0.75 m ² / g), 4.3 g of powdered activated carbon and 2 g of dextran were pasted with a little water, granulated and dried in a drying oven at 100 ⁰ C. The granules were in a quartz tube

(Inner diameter 22 mm) tightly packed between two plugs of quartz wool and annealed in a tube furnace at 800 ⁰ C to remove residues of water and to pyrolyze the dextran. The temperature was then raised to 1300 ⁰ C and initially passed a HCl gas stream of 4 L / h through the package. In the course of the reaction, the granules disintegrated into powdery material, which after 4 hours of reaction time required a reduction of the amount of HCl gas to 3 L / h. The reaction gases were passed through a cold trap (-7O ⁰ C) to separate formed products from remaining HCl gas, H ₂ , CO and CO ₂ . After 12 hours of reaction time, no residues of quartz could be found in the bed anymore by X-ray powder diffractometry be detected. The isolated yield of SiCl ₄ was 9.23 g (81.6% of the theoretical yield).

Example 2

4 g of quartz sand (average particle size 0.32 mm, corresponding to a theoretical specific surface area of 75 cm ² / g), 4.2 g of powdered activated carbon and 2 g of dextran were treated as in Example 1 and the reaction was carried out similarly. After 12 hours reaction time, the reaction of SiO ₂ was not completed. The isolated yield of SiCl ₄ was 4.52 g (40% of the theoretical total conversion).

Example 3

4 g of desert sand (Sahara, mean particle size <0.5 mm, SiO ₂ content about 80%), 4.2 g of powdered activated carbon and 2 g of dextran were treated as in Example 1 and the reaction was carried out similarly. The reaction was not complete after 12 hours. The isolated yield of SiCl ₄ was 2.42 g.

Example 4

4 g of quartz powder (average particle size 3 μm, corresponds to a theoretical specific surface area of 0.75 m ² / g), 4.2 g of powdered activated carbon and 2 g of dextran were treated as in Example 1 and the reaction with HCl at a temperature of 800 ^c C executed. The reaction was not complete after 12 hours. The isolated yield of SiCl ₄ was 0.72 g (6% of the theoretical total conversion). Example 5

4 g of quartz powder with a mean particle size of 3 μm corresponding to a theoretical specific surface area of 0.75 m ² / g, 4.2 g of graphite powder with a maximum particle size of 50 μm and 2 g of dextran were treated as in the preceding examples and the reaction carried out with HCl at a temperature of 1300 ⁰ C. The reaction was not complete after 12 hours. The isolated yield of SiCl ₄ was 1.92 g, corresponding to 17% of the theoretical total conversion.

Example 6

On a quartz glass slide (halved quartz glass tube,

Diameter 13 mm, length approx. 100 mm, feet made of quartz glass 5 mm), 1 - 1.5 g of a SiC ^ / C mixture consisting of desert sand with a maximum particle size of 0.5 mm and activated carbon with a particle size of 2 - 2.5 mm in the ratio 1: 4 given. The quartz glass carrier was introduced into a reaction tube (glass tube, diameter 30 mm with two chimneys, drop tube plus riser, average distance 100 mm), which was placed in the hotspot of a microwave reactor (Panasonic domestic appliance). Into the reaction tube was introduced a mixture of reaction (hydrogen chloride, 60 l / h) and inert gas (nitrogen, 40 l / h). After heating, the reaction product (SiCl ₄ ) was condensed out in a cold trap in which pentane was initially charged with an ethanol cold bath at below -30 ° C. The analysis was quantitative and qualitative.

In a reaction time of 15 - 20 minutes 50-60% of the desert sand could be reacted, the calculation by weight difference of the sample after the reaction SiO ₂ + 2 C + 4 HCl → SiCl ₄ + 2 CO + 2 H ₂ . Taking into account the SiO ₂ content in sand of about 80% and the influence of the Boudouard equilibrium with the formation of CO ₂ and C from CO, the actual SiO 2 conversion increases accordingly. This results in a largely quantitative yield with respect to the SiO 2 source.

Example 7

5 g of Fe ₂ O ₃ powder (particle size <5 μm) was mixed with 10 g of activated carbon and the mixture was tightly packed in a quartz tube (inner diameter 22 mm) between two quartz wool plugs. In two experiments at temperatures of 1300 ° C and 800 ⁰ C, an HCl gas stream of 4 L / h was passed through this package in each case for 6 hours. Outside the reaction zone, colorless platelets and a white to yellowish powder condensed in both cases, which were identified as FeCl ₂ by X-ray powder diffraction. In the reaction residue could be detected by X-ray powder diffractometry neither iron oxides nor iron chlorides.

Example 8

5 g Al ₂ θ ₃ powder (particle size <150 microns) was mixed with activated carbon, the mixture densely packed (22 mm inside diameter) between two plugs of quartz wool in a quartz tube and dried at 800 ⁰ C in vacuo. In two experiments at temperatures of 1300 ⁰ C and 1000 ⁰ C was passed through this package for 6 hours each an HCl gas stream of 4 L / h-. Outside the reaction zone, a white powder condensed, which was identified by X-ray powder diffractometry and comparison with a sample of freshly sublimed aluminum trichloride as AlCl ₃ . In the reaction residue could by X-ray powder diffractometry no aluminum oxides or aluminum chlorides can be detected.

Example 9

Successful experiments on the conversion of elemental materials under microwave irradiation were performed on all materials tested. To protect the glass apparatus from reaction and thermal stress, the reactants were placed in the reactor on quartz glass slides consisting of a center cut quartz tube which was provided with feet. The reaction rate of the outer wall of the reactor is therefore significantly reduced by the low surface area and substantially lower temperature compared to the powdered or granular reaction mixtures, so that destruction of the reactor outer wall during a single reaction was not observed.

On a quartz glass support (halved quartz glass tube, diameter 13 mm, length about 100 mm, feet of quartz glass 5 mm) were added 1 - 1.5 g of a mixture of one of the listed element-containing materials with one of the carbon-containing materials also listed. The quartz glass carrier was introduced into a reaction tube (quartz glass tube, diameter 30 mm, length 550 mm), which was introduced into the hotspot of a microwave reactor (MX 4000, MUEGGE Electronic GmbH). An HCl gas stream (1-5 L / min) was passed through the reaction tube with heating (550-1300 ⁰ C) by activation of the microwave reactor. Under normal conditions, liquid or gaseous reaction products were condensed out in a cold trap in which pentane was initially charged with an ethanol cooling bath at less than -30.degree. The reaction time was about 10 minutes each. In this experimental setup, the following element-containing compounds with carbon-containing compounds were selected from the group consisting of activated carbon (pure, ~ 2.5 mm), activated carbon (pure, powder), graphite (pure), hard coal (German hard coal), lignite (RWE Powers) and Petrokoks (OMV) implemented:

Element-containing compounds: aluminum (III) oxide; <150μm, 99%

Boron (IΙI) oxide; extremely pure,> 99.98%

Iron (III) oxide; <5μm,> 99%

Hafnium (IV) oxide; 98%

Mica flakes silicon carbide; 37 μm

Highly dispersed silicic acid (380 m ² / g)

Quartz fine meal (mean particle size 3 μm, theoretical specific surface 0.75 m ² / g)

Quartz sand (average particle size 0.32 mm, theoretical specific surface 75 cm ² / g)

Desert Sand (Sahara, coordinates N23 ° 27.419, E 009 ° 01.489,

Particle size <0.5 mm) crushed brown reusable beverage bottle (amber glass) crushed pasteur pipettes (lime soda glass) Japanese rice ash

Catalyst based on zeolite

silicon nitride; Si ₃ N ₄ , 44 μm

silicon monoxide; <44 μm

titanium dioxide; > 99.8% tricalcium phosphate; 35-40% Ca

Silicon tetrachloride was detected by GCMS and ²⁹ Si NMR compared to purchased standard compounds. Boron trichloride as the diethyl ether adduct and phosphorus trichloride were detected by ¹¹ B NMR and ³¹ P NMR against purchased standard compounds. Iron dichloride, aluminum trichloride and hafnium tetrachloride were detected by EDX and X-ray powder diffractometry.

Titanium tetrachloride could not be detected directly with the available laboratory equipment. The strongly fumed pentane solution was transferred to GC vials. After settling the resulting precipitate, the supernatant clear solution was lifted through the septum and transferred to a new vial through the septum. This clear solution was mixed with water through the septum. There was immediately a white voluminous precipitate. This was dried and identified by means of EDX as titanium oxide.

Claims

claims A process for the preparation of elemental halide, characterized in that a mixture of a material containing the element with carbon or carbonaceous material is brought under heating with a gas stream containing under the reaction conditions gaseous hydrogen halide in contact. 2. The method according to claim 1, characterized in that powdery materials containing the corresponding element are used. 3. The method according to claim 1 or 2, characterized in that the carbon or the carbonaceous material is used in granular form or powder form. 4. The method according to any one of claims 1 or 3, characterized in that the element-containing material is introduced in liquid form or as a gas in the reaction space. 5. The method according to any one of claims 1, 2 or 4, characterized in that the carbon-containing material is introduced in liquid form or as a gas in the reaction space. 6. The method according to any one of claims 1 to 5, characterized in that the carbon or the carbonaceous material used is heated by an alternating electromagnetic field. 7. The method according to any one of claims 1 to 6, characterized in that the alternating electromagnetic field used is generated by microwave radiation. 8. The method according to any one of claims 1 to 7, characterized in that the carbon or the carbonaceous material used during the production of the element halide at least partially reacted to not excitable by an electromagnetic alternating field carbon compounds. 9. The method according to any one of claims 1 to 8, characterized in that the carbon or the carbonaceous material is transferred by the action of an alternating electromagnetic field on the substance mixture in the reaction space in a heatable by the electromagnetic alternating field shape. 10. The method according to any one of claims 1 to 5, characterized in that the reaction mixture is heated by a resistance heater, a radiant heater or solar thermal. 11. The method according to any one of claims 1 to 10, characterized in that the gaseous hydrogen halide under reaction conditions is used together with a carrier gas. 12. The method according to any one of claims 1 to 11, characterized in that are used as the hydrogen halide hydrogen fluoride or hydrogen chloride. 13. The method according to any one of claims 1 to 12, characterized in that the element contained in the element compound used is a metal or a non-metal. 14. The method according to any one of claims 1 to 13, characterized in that the element-containing compound is present in a mixture with other materials. 15. The method according to any one of claims 1 to 14, characterized in that during the preparation of hydrolysis-sensitive element halide, the mixture is heated to more than 700 ° C. 16. The method according to any one of claims 1 to 15, characterized in that a naturally occurring raw material is used as the element-containing material. 17. The method according to any one of claims 1 to 16, characterized in that as a material containing the element, a by-product or a waste product of a technical production process is used. 18. The method according to any one of claims 1 to 17, characterized in that the element-containing material Purification steps or steps for concentration of the element is subjected before it is used in the process according to the invention. 19. The method according to any one of claims 1 to 18, characterized in that as element-containing material materials containing SiO _x , where x may be a number from 1 to 2, is used. 20. The method according to claim 19, characterized in that is used as the material containing SiO _x desert sand.