WO2014122049A1 - Isolation of metal- or metalloid compounds from the gas phase by complexing - Google Patents

Abstract

The invention relates to a method for removing metal- or metalloid compounds M present in the gas phase from a gas G containing said compounds. According to the invention, the gas G containing the volatile metal- or metalloid compound M is brought into contact with a solid donor D and the resultant reaction product is isolated.

Description

 Separation of Metal or Metalloid Compounds from the Gas Phase by Complexation The present invention relates to a process for the removal of gas phase metal or metalloid compounds M.

Furthermore, the present invention relates to a device suitable for carrying out this method.

In the chemical production of metal or metalloid compounds, for example, from the elements, the desired reaction products, especially in the case of volatile compounds but also by-products in the gas phase, often as a mixture together with starting materials in the gas phase, also herein Called educts.

Usually then reaction products, by-products and reactants must then be separated from each other, inter alia, to avoid deposits of the metal or metalloid at colder sites of the reaction system or aufzur- agree on the gaseous reactants.

Examples of the preparation of metal or metalloid compounds are the preparation of halides, for example chlorides or bromides, of the metals or metalloids of groups 12, 13 and 14 of the Periodic Table of the Elements, such as zinc, boron, aluminum, silicon, tin or the like of the iron from the corresponding metals or metalloids and elemental halogens such as chlorine, bromine or iodine.

Metal or metalloid compounds are usually "electronically unsaturated" and thus able to bind an electron donor as a lingand.These electronically unsaturated compounds are also referred to in the art as "Lewis acids", and the electron donors as " Lewis bases. "The reaction products of Lewis acids and Lewis bases are also referred to as" Lewis acid / Lewis base adducts "or metal complexes or metalloid complexes. The Lewis bases are part of the ligands in such metal or metalloid complexes.

WO 00 / 56659A1, for example, describes the formation of a metal complex, namely sodium tetrachloroaluminate (NaAlCU) by reaction of sodium chloride (NaCl) with aluminum trichloride (AICI ₃ ) at a temperature between 156 ° C and 180 ° C. The object of the invention was to provide a method for separating off the gas phase metal or metalloid compounds from a gas containing them. Accordingly, the method defined herein and in the claims as well as the apparatus suitable for carrying it out have been found.

Metals within the meaning of the present application are all metals of the Periodic Table of the Elements, preferably those which form chemical compounds, preferably halides, for example chlorides, which are Lewis acids.

The metals are particularly preferably selected from groups 4, 8, 12, 13 and 14 of the Periodic Table of the Elements, for example titanium, iron, zinc, cadmium, mercury, aluminum, gallium, indium and tin.

Metalloids in the sense of the present application are selected from the group boron, silicon, germanium, arsenic, selenium, antimony and tellurium. These are also referred to in science as "semi-metals".

Preferably, the metalloids which form chemical compounds are preferably halides, for example chlorides, which are Lewis acids.

The metalloids are particularly preferably boron, silicon and germanium.

Metal or metalloid compounds M are chemical compounds, preferably binary chemical compounds, of the metals or metalloids as described herein and a chemical element or ligand group.

 In a preferred embodiment, the metal or metalloid M compounds are volatile, which usually means that they have a vapor pressure of more than 30 mbar in the temperature range of 100 to 500 ° C.

Highly suitable metal or metalloid compounds M are the corresponding halides, preferably binary halides, preferably fluorides, chlorides, bromides, particularly preferably chlorides, all of which are generally present under the reaction conditions according to the invention virtually without water of crystallization or similar adduct-forming compounds.

Examples of highly suitable metal or metalloid halides are those of the formula (I) Met X _n (I) where Met metals or metalloids, preferably metals of groups 4, 8, 12, 13 and 14 of the Periodic Table of the Elements, more preferably titanium, iron , Zinc, aluminum, gallium, indium, tin or the metalloids boron and preferably silicon; X is halogen, preferably fluorine, chlorine, bromine, more preferably chlorine, and n has the numerical value of the formal oxidation number of the metal or metalloid in the formula (I), for example 2, 3 or Examples of metal or metalloid halides (I) are:

Titanium IV chloride (TiCU), ferric chloride (FeC), zinc dichloride (ZnC), aluminum trichloride (AlC), boron trichloride (BCI ₃ ), boron trifluoride (BF ₃ ), silicon tetrachloride (SiCU), tin dichloride (SnC) or tin tetrachloride (SnCl).

The gas G is usually practically inert to the metal or metalloid compound M, which means that it generally does not decompose the metal or metalloid compound M under the conditions of the process according to the invention.

In general, it contains or contains essentially that portion of the starting material which was not a metal or metalloid as a reactant and which has not reacted with the metal or metalloid to form the metal or metalloid compound M. Furthermore, the gas G may be formed by the reaction of a reactant gas with the metal or metalloid, for example, the gas G may be elemental hydrogen or contain the hydrogen, for example, by the reaction of hydrogen halide, such as hydrogen chloride, with a metal or metalloid selected from the groups 4, 8, 12, 13 and 14 of the Periodic Table of the Elements, for example aluminum was formed. An exemplary hydrogen generating reaction is the reaction of aluminum with hydrogen chloride gas.

Gas G is also to be understood here as meaning a mixture of gaseous substances, including, inter alia, the reactant in the gaseous state, which serves as a reaction partner of the metal or metalloid to form the metal or metalloid compound.

For example, the gas G may be selected from the group consisting of:

Nitrogen (N ₂ ); Hydrogen (H ₂ ); Oxygen (0 ₂ ); Halogen, such as fluorine (F ₂ ); Chlorine (Cl ₂ ); Bromine (Br2); Noble gases, such as argon (Ar); Carbon halides such as carbon tetrachloride (CCU); Hydrogen halides, such as hydrogen chloride (HCl) and hydrogen fluoride (HF).

Preferably, the gas G is selected from the group consisting of: chlorine (C); Hydrogen (H2); Carbon halides, such as carbon tetrachloride or hydrogen halides, such as hydrogen chloride (HCl) and hydrogen fluoride (HF).

Most preferably, the gas G is chlorine (Cb) or contains chlorine (Cb) as an essential component.

The donor D is a chemical compound which is solid under the conditions of the process according to the invention and as a rule can act as lewis basic complex ligand with respect to the metal or metalloid compound M. The donor D is usually chosen so that its reaction with the metal or metalloid M, a compound - formally a complex compound - is formed with the lowest possible melting point. Preferably, the donor D is selected from the groups consisting of alkali metal compounds and / or alkaline earth metal compounds, preferably alkali metal halides, for example alkali metal chlorides and / or alkaline earth metal halides, for example alkaline earth metal chlorides, wherein in said groups as alkali metals lithium (Li), sodium (Na) or potassium (K are preferred and as alkaline earth metals magnesium (Mg) or calcium (Ca) are preferred wherein the donor D is usually chosen so that by its reaction with the metal or metalloid M a compound - formally a complex compound - is formed with the lowest possible melting point and wherein the compounds from the abovementioned groups are generally present under the reaction conditions according to the invention virtually without water of crystallization or similar adduct-forming compounds.

Particularly preferred as donor D are lithium chloride (LiCl), sodium chloride (NaCl), lithium fluoride (LiF), potassium fluoride (KF) and magnesium chloride (MgC).

The process according to the invention is preferably carried out in such a way that the reaction product of metal or metalloid compound M and donor D is present in molten form, ie in liquid form, and in another embodiment the donor D is additionally selected such that its reaction with the metal or metalloid compound M is a compound - formally a complex compound - is formed with the lowest possible melting point. Preferably, contacting gas G, preferably volatile metal or metalloid compound M, with solid donor D is conducted at a temperature at or above the melting point of the resulting reaction product but below the melting point of donor D, preferably such temperature is chosen to be at or above the sublimation temperature of the metal or metalloid compound M.

In a preferred variant of the process according to the invention, the metal or metalloid compound M is a halide, the gas G contains a halogen or contains essentially a halogen or consists for example of halogen and the donor D is an alkali metal halide or alkaline earth metal halide.

Particularly preferably, in this variant, the components M, G and D all contain the same halogen or halide, preferably chlorine or chloride or fluorine or fluoride, very particularly preferably chlorine or chloride, and in a further embodiment, the donor D is additionally chosen so that by its reaction with said metal or metalloid M compounds, a compound - formally a complex compound - is formed with the lowest possible melting point. In a well-suited embodiment of the process according to the invention, the metal compound M is aluminum trichloride (AlC), the gas G contains chlorine (C) or contains essentially chlorine (Cl 2) or consists for example of chlorine (Cb) and the donor D is an alkali metal metal halide for example, alkali metal chloride and / or bromide and / or alkali metal fluoride and / or iodide, such as sodium chloride (NaCl) and / or sodium fluoride (NaF) and / or sodium bromide (NaBr) and / or sodium iodide (Nal), preferably alkali metal chloride, sodium chloride NaCl is particularly preferred, and in another embodiment the donor D is additionally selected such that its reaction with the metal compound M aluminum trichloride (AlCb) forms a compound-formally a complex compound-with the lowest possible melting point.

In another suitable embodiment of the process according to the invention, the metal compound M is iron-III chloride (FeC), the gas G contains chlorine (Cb) or contains essentially chlorine (Cl 2) or consists for example of chlorine (Cb) and the donor D. is an alkali metal halide, for example, alkali metal chloride and / or bromide and / or alkali metal fluoride and / or iodide, such as sodium chloride (NaCl) and / or sodium fluoride (NaF) and / or sodium bromide (NaBr) and / or sodium iodide (Nal ), preferably alkali metal chloride, more preferably sodium chloride NaCl, and in another embodiment, the donor D is additionally selected so that by its reaction with the metal compound M ferric chloride (FeC) a compound - formally a complex compound - with the lowest possible melting point is formed.

In another suitable embodiment of the process according to the invention, the metalloid compound M is boron trichloride (BCI3), the gas G contains chlorine (Cb) or contains essentially chlorine (C) or consists for example of chlorine (Cb) and the donor D is an alkali metal metal halide, for example alkali metal chloride and / or bromide and / or alkali metal fluoride and / or iodide, such as sodium chloride (NaCl) and / or sodium fluoride (NaF) and / or sodium bromide (NaBr) and / or sodium iodide (Nal), and In a further embodiment, the donor D is additionally selected such that its reaction with the metalloid compound M boron trichloride (BCI3) forms a compound-formally a complex compound-with the lowest possible melting point.

In a further well-suited embodiment of the process according to the invention, the metalloid compound M is boron trifluoride (BF3), the gas G contains fluorine (F2) or essentially contains fluorine (F2) or consists for example of fluorine (F2) and the donor D is a Alkali metal halide, for example, alkali metal chloride and / or bromide and / or alkali metal fluoride and / or iodide, such as lithium chloride (LiCl) and / or lithium fluoride (LiF) and / or lithium bromide (LiBr) and / or lithium iodide (Lil), and in In another embodiment, the donor D is additionally selected such that its reaction with the metalloid compound M boron trifluoride (BF 3) forms a compound-formally a complex compound-with the lowest possible melting point. The gas G containing the preferably volatile, metal or metalloid compound M can originate from various sources, for example a chemical process for the preparation of the metal or metalloid compound M, for example a chemical process for the preparation of halide compounds of the groups 4, 8, 12, 13 or 14, preferably groups 8, 13 or 14 of the Periodic Table of the Elements, for example from the corresponding elemental metal or metalloid and the corresponding halogen, such as: aluminum trichloride (AlCl 3) of aluminum metal and elemental chlorine (C); Ferric chloride (FeC) of iron metal, for example scrap iron, and elemental chlorine (C); Boron trichloride (BC) from elemental boron and elemental chlorine (C), wherein the gas G, as it comes from said production processes for the metal or metalloid compound M without prepurification in the context of the invention can be treated but also with pre-cleaning in the sense of Invention can be further treated in such a way that it has already been freed from parts of said metal or metalloid compound M, for example by desublimation. The gas G containing the preferably volatile metal or metalloid compound M can also be derived from an electrochemical process for the preparation of halogens and / or alkali metals, for example lithium, sodium or potassium.

An example of an electrochemical process for producing alkali metals is the electrolysis of a mixture, preferably in the form of a melt, containing one or more alkali metal halides, for example, sodium chloride and a Group 13 metal halide of the Periodic Table of Elements, for example, aluminum chloride (AlC) as described in US Pat

4,203,819. In a suitably suitable embodiment of the process according to the invention, this flows through the, preferably volatile, metal or metalloid compound M, preferably halides of groups 8 or 13 of the Periodic Table of the Elements such as aluminum chloride (AlC); Boron trichloride (BC); Ferric chloride (FeC); containing gas G, the present in solid form, for example as a fixed bed, donor D at a temperature at or above the melting point of the resulting reaction product of metal or metalloid compound M and donor D but below the melting point of the donor D, preferably this temperature is chosen to be at or above the sublimation temperature of the metal or metalloid compound M. In this embodiment, the gas G contains a halogen or contains substantially a halogen or consists for example of halogen, for example elemental fluorine (F2) or in particular elemental chlorine (C). Furthermore, in this embodiment, the donor D is selected from the groups consisting of alkali metal compounds and / or alkaline earth metal compounds, preferably alkali metal halides, for example, alkali metal chlorides, such as sodium chloride (NaCl) and / or alkaline earth metal halides, for example, alkaline earth metal chlorides, such as magnesium chloride (MgC), in those groups As alkali metals lithium (Li), sodium (Na) or potassium (K) are preferred and as alkaline earth metals magnesium (Mg) or calcium (Ca) are preferred and wherein the compounds of these groups usually under the reaction conditions of the invention practically without water of crystallization or similar adduct-forming compounds. Particularly preferred as donor D in this embodiment are lithium chloride (LiCl), sodium chloride (NaCl), lithium fluoride (LiF), potassium fluoride (KF) and magnesium chloride (MgC).

Examples of the preferred embodiment described here include the following combinations of substances: a) metal compound M aluminum chloride (AlC) and gas G chlorine (C) and / or hydrogen chloride (HCl) and / or hydrogen (H2) and donor D sodium chloride (NaCl) ; b) metalloid compound M boron trichloride (BCI3) and gas G chlorine (Cb) and donor D sodium chloride (NaCl); c) metalloid compound M boron trifluoride (BF3) and gas G fluorine (F2) and / or hydrogen fluoride (HF) and / or hydrogen (H2) and donor D lithium fluoride (LiF); d) metal compound M ferric chloride (FeCl ₃ ) and gas G chlorine (Cl ₂ ) and / or hydrogen chloride (HCl) and / or hydrogen (H 2) and donor D sodium chloride (NaCl).

 The embodiment described here is usually carried out in the apparatus described below, for example that according to FIG. The following also stands for the description of the features M, G and D also the above, especially as regards the various embodiments.

In a preferred embodiment, the solid donor D, preferably the donor D formed as a fixed bed, is accommodated in a tubular housing. The tubular housing is in this case preferably aligned at an arbitrary angle of 0 ° to 90 ° to the horizontal, particularly preferably substantially perpendicular.

More preferably, the influx of the gas G containing the metal or metalloid compound M and the outflow of the, preferably liquid, reaction product of metal or metalloid compound M and donor D takes place at different locations of the tubular housing.

In a well-suited embodiment, the gas G containing the metal or metalloid compounds M is fed at a position deviating from 0 ° to the horizontal, preferably at a substantially vertical orientation, of the tubular housing at the lower end thereof, so that the gas G and move the reaction product in countercurrent to each other.

The present invention furthermore relates to an apparatus for carrying out the method according to the invention, comprising a tubular housing with a fixed bed accommodated therein, the tubular housing having an inlet for the G containing the metal or metalloid compound M, a drain for the treated gas and a drain for the, preferably liquid, reaction product of metal or metalloid compound M and donor D. In a preferred such device, the fixed bed of the donor D is segmented, for example, by trays which are generally gas and / or liquid permeable. In a further preferred embodiment of such a device, the outlet for the liquid reaction product is designed as a siphon.

FIG. 1 shows by way of example a device according to the invention.

In Fig. 1, reference numerals denote:

1 . column

 2. Pneumatic conveying

 3. sieve bottom, several times

 4. screw conveyor, drivable with the motor M

 5. Last sieve bottom with final fill

 6. Siphon

 7. Gas G (admission)

 8. Gas G (exit)

 9. solids supply line

 10. reaction product outlet

 1 1. Donor D (Feed) The device according to the invention is usually made of a material which is chemically resistant to the components M, G and D and which usually has a temperature range of 200 to 500 ° C. and a pressure range of 30 mbar (abs.). up to 10 bar (abs.) is pressure and dimensionally stable, such as nickel, Hastelloy, inconel, steel (enamelled), steel lined with PTFE, glass, titanium, tantalum.

Claims

claims 1 . A process for the removal of gas phase metal or metalloid compounds M from a gas G containing them by contacting the gas G containing the volatile metal or metalloid compound M with a solid donor D and separating the resulting reaction product. 2. The method of claim 1, wherein the metal or metalloid compounds M are halides. 3. The method of claim 1 to 2, wherein the metals or metalloids of the metal or metalloidloids M are selected from the groups 4, 8, 12, 13 and 14 of the Periodic Table of the Elements. 4. The method of claim 1 to 3, wherein the gas G is selected from the group consisting of nitrogen (N2); Hydrogen (H2); Oxygen (O2); halogens; Noble gases; Carbon halides and hydrogen halides. 5. The method of claim 1 to 4, wherein the donor D is selected from the group consisting of alkali metal compounds and alkaline earth metal compounds. 6. The method of claim 1 to 5, wherein the donor D is selected from the group consisting of alkali metal halides and alkaline earth metal halides. A process according to claims 1 to 5, wherein the reaction product is in molten form. A process according to claims 1 to 7, wherein the contacting of the volatile metal or metalloid compound M containing gas G with a solid donor D occurs at a temperature at or above the melting point of the resulting reaction product but below the melting point of the donor D. 9. The method of claims 1 to 8, wherein the metal or metalloid compound M is a halide, the gas G contains a halogen, and the donor D is an alkali metal halide or alkaline earth metal halide. 10. The method of claim 1 to 9, wherein the metal compound M is selected from aluminum chloride, ferric chloride, boron trichloride or boron trifluoride, the gas G contains chlorine (C) and the donor D is an alkali metal halide. 1 1. A method according to claims 1 to 10, wherein the gas G containing the volatile metal or metalloid compound M is from a chemical process. 12. The process according to claims 1 to 10, wherein the gas G containing the volatile metal or metalloid compound M originates from an electrochemical process. 13. A process according to claim 12, wherein the gas G containing the volatile metal or metalloid compound M is from an electrochemical process for the production of halogens and / or alkali metals. 14. A device for carrying out the method according to any one of claims 1 to 13, comprising a rohrformiges housing with a received therein, the donor D-containing fixed bed, wherein the tubular housing an inlet for the metal or metalloid M containing gas G, a drain for the purified gas G and a drain for the liquid reaction product. 15. The apparatus of claim 14, wherein the outlet for the liquid reaction product is designed as a siphon.