DE19626421A1 - Removing environmentally harmful gaseous hydride(s) and halide(s) of silicon and arsenic - Google Patents

Abstract

Environmentally harmful gaseous hydrides and halides of elements in gps III, IV, V, VI and VIa are removed by absorption and oxidation by a macroporous carrier having an internal micro-porous structure of pores of width 0.3 to 3 nm coated with an oxidising agent. Also claimed is the use of such an absorption/oxidising agent to remove the hydrides and halides.

Description

The invention relates to an absorption / oxidizing agent for Removal of polluting gaseous hydrides and / or Halogen compounds of elements from the group III, IV, V and / or VI and subgroup VI of the Periodic Table.

These compounds are in larger quantities z. B. in the Her semiconductors, where they are mainly used as raw material Ria or doping gases are used; they arise to Part also in the chemical treatment of semiconductors or are used as solvents. To include the hydrides For example, B₂H₆, SiH₄, GeH₄, PH₃, AsH₃ and SeH₂, not in contrast, the halogen-free hydrocarbons. To the halo genverbindungen include, for example, B₂F₆, SiCl₄, SiH₂Cl₂, SiF₄, NF₃, SeF₆ and WF₆. The compounds mentioned are in the Usually as mixtures. They are partly toxic, partly cause heavy (especially the halogen compounds)  weighing environmental problems, in particular a significant ozone depletion potential exists.

In a known method of the company thin-film plants Dresden will use these polluting gaseous Thermally decomposed substances and then a wet scrubbing subjected. In some cases (eg in the case of the Halogen compounds) aggressive or toxic condensates (eg Hydrogen halides). These can be too serious Lead to corrosion damage to the upstream process equipment. Particularly problematic from the perspective of the plant operator are: (a) corrosion damage and (b) contamination by decomposition products that can hit back into the plant. Farther is disadvantageous in this method that the disposal of Condensates must usually be carried out as hazardous waste. closing It consumes large amounts of water and energy.

From the reference W. Simmler, "Ullmanns Encyclopedia of Industrial Chemistry "(1993), A 24,4 is a" dry Ver driving "known, in which the polluting gases, enthal silanes and Si halides, by columns with an oxide be passed to the silicon compounds to remove. The oxidizer consists of one with sodium carbonate treated mixture of copper and zinc nitrate. However, this oxidizer has a low absorption capacity and is expensive to manufacture.

From EP-A-0 309 099 a process for the oxidative Removal of toxic gases from a gas stream known wherein the oxidizing agent is manganese dioxide and copper oxide contains, on which a silver compound is deposited. However, this oxidizer is unsatisfactory lende absorption / oxidation capacity and is expensive in the production.

Accordingly, it is the object of the present invention, a  Absorption / oxidation agent for environmental removal stenden gaseous hydrides and / or halogen compounds to provide that the disadvantages of the prior art avoids and a particularly efficient removal of this Compounds from the gas stream allows.

This task is accomplished by an absorption / oxidation agent solved, which is characterized by a macroporous carrier with a one-, two- or three-dimensional intrinsic (inner) microporous structure with micropore widths of about 0.3 to 3 nm, which is coated with an oxidizing agent.

The absorption / oxidation agent according to the invention has a Dual function. As an oxidizing agent it oxidizes the gasför hydrides as well as the halogen compounds that still have water contain substance; as an absorbent it is able to Hydrides and their oxidation products and at the same time the non-oxidizable halogen compounds or their Zerset absorptive binding. Especially for this the latter function is the one-, two- or three-dimensional intrinsic micropore structure of the microporous support Th between about 0.3 to 3 nm responsible. In addition to an absorp tive binding of gaseous reactants and reaction products probably also find in the micropores of the vehicle chemical reactions, for example, polymerizations take place, whereby the reaction products are immobilized on the carrier. This effect can be achieved with carriers containing these micropores do not have structure, can not be achieved.

The micropores can be considered one-dimensional channels with a "Tube bundle structure" present. In a two-dimensional Structure, two "tube bundles" intersect in a plane, wah In a three-dimensional structure, three "tube bundles del "in a spatial arrangement, wherein in the the latter two cases at the crossing points cavities or "Cages" are formed. The micropores can also as  two-dimensional intermediate layers or "slots" are present, in which case the micropore width is considered to be the intermediate layer distance (slot width) is defined. The "slots" can also be crossed by channel-shaped micropores, so that in this case again a three-dimensional Microporous structure is present.

The carrier also has a macroporous structure. This ent stands when the microporous carrier particles to agglomerates be united, with the macropores through the cavities be formed between the carrier particles (Zwischenkornvolu men). The macropores generally have a pore size of about 7 to 15,000 nm, preferably from 14 to 175 nm. The Macropores, also referred to as "feed pores" can promote the diffusion of the reactants to the carrier particles and into the micropores, in which the individual Reak take place predominantly. The micropores can therefore also referred to as "active pores". The macropores become determined by mercury porosimetry (Carlo-Erba-Porosi meter, pressure 2,000 bar).

It is with the absorption / oxidation agent of the invention possible, large quantities of said oxidizable gaseous Compounds to almost 100% oxidatively destroy and the Reaction products and the non-oxidizable compounds absorb absorptive. The absorption / oxida according to the invention tion means shows over the previous oxidizing agents 1.5 to 5 times the absorption capacity, based on SiH₄.

The micropore widths of the carrier are preferably about 0.4 to 2 nm, in particular about 0.5 to 1.5 nm.

Preferred supports are zeolites, double layer hydroxocarbonates and / or optionally bridged layer used silicate.  

Examples of carriers with a one-dimensional microporous structure are (abbreviations according to the IUPAC nomenclature):
LTL (Linde type L), a synthetic zeolite having the formula K₆Na₃ [Al₉Si₂₇O₇₂] · 21H₂O (micropore width 0.71 nm)
AFI (AlPO₄-5) having the formula [Al₁₂P₁₂O₄₈] · (C₃H₇) ₄NOH · xH₂O and the structural isotypes SAPO-5; SSZ-24 (silicic acid range) with micropore widths of 0.73 nm;
VPI-5, MCM-9 with micropore widths of 1.2 nm;
AlPO₄-8 with micropore widths of 0.87 x 0.79 nm;
Mazzite types with micropore widths of 0.74 nm;
LZ-202 with micropores of 0.563x0.34 nm.

Examples of carriers with a two-dimensional microporous structure are:
Hydrotalcite, a dialuminium hexamagnesium carbonate Hexadecahydroxid tetrahydrate having the formula Al₂Mg₆ (OH) ₁₆CO₃ · 4H₂O, with microporenweiten (layer distances) of about 0.78 nm or a hydrotalcite isotype with the formula Al₂Mg _4,5 (OH) ₁₃CO₃ · 3 1/2 H₂O with a microporous width of 0.76 nm.

Ferrierite, a zeolite having the formula Na₂Mg₂ [Al₆Si₃₁O₇₂] · 18 H₂O and its structural silicic acid isotypes, z. ZSM-35, NU-23 with channels of 0.42 x 0.54 nm connected by channels of 0.48 x 0.35 nm;
Mordenite, a zeolite having the formula Na₈ [Al₈Si₄₀O₉₆] · 24 H₂O and its siliceous structural isotypes with 0.7 × 0.65 nm channels, which are connected by short alternating channels with pore widths of 0.3 nm;
Heulandite, a microporous zeolite of 0.76 x 0.3 nm and 0.47 x 0.26 nm;
Clinoptilolite, a zeolite with channel diameters of 0.47 x 0.26 nm and 0.46 x 0.33 nm, respectively;
Examples of carriers with a three-dimensional microporous structure are:
Beta heulandite with micropore widths of 0.75 x 0.57 nm and 0.65 x 0.56 nm, respectively;
Faujasites such as Linde X, Linde Y, SAPO-37, CSZ-3, LZ-210 with micropore widths of about 0.74 nm;
LTA (Linde type A) with the formula Na₁₂ [Al₁₂Si₁₂O₄₈] 27 H₂O and its structural isotypes SAPO-42 and kieselsäu rereichen types (1 Si / Al 3) with a microporous diameter of 0.41 nm, resulting in the formation of combine spherical cages with a diameter of 1.14 nm;
MFI (ZSM-5 = pentasil) with the formula Na _n [Si _96-n Al _n O₁₉₂] x 16 H₂O (n 8) and its structural isotypes silicalite-1 (Si / Al = ∞), boralite TS-1, ( Si, Ge) -MFI, with channel diameters of 0.25 x 0.57 nm, which channels are connected by sinusoidal channels with widths of 0.53 x 0.56 nm and at the crossover score cages with a diameter of about zero , 9 nm are formed;
Faujasite with the formula Na₅₈ [Al₅₈Si₁₃₄O₃₄₈] · 24 H₂O and the structural isotypes zeolite X (1 Si / Al 1.5), zeolite Y (Si / Al 2.5), SAPO-37 with channel widths of 0.74 nm and verbin cages with a diameter of 1.18 nm.

These and other carriers are for example in the literature H. van Bekkum, E.M. Flanigen, J.C. Jansen, "Introduc tion to Zeolite Science and Practice, Studies in Surface Science and Catalysis "Vol. 58, Elsevier 1991, pages 728-735 and in "Ullmanns Enzyklopadie der technischen Chemie", volume 17, (1979), pages 9 to 18 described (micropores approximately 0.4 to 0.71 nm).

The layered silicates differ from the above-mentioned zeolites in that the micropores are not channel-shaped as in hydrotalcite, but form two-dimensional intermediate layers (slits), wherein the pore widths can be about 1 to 2.5 m, in particular 1 to 2 nm. Examples of layered silicates are bilayer silicates, such as kaolin and talc, and in particular the smectitic three-layer silicates, which include montmorillonite, beidellite, saponite, glauconite and hectorite. The interlayer distances (pore widths) depend on the type of interlayer cations. Thus, the interlayer distance decreases when the alkaline interlayer ions are replaced by alkaline earth ions or higher-valent ions. A special case of these layer silicates are the bridged phyllosilicates, which are also referred to as "pillared clays". In these Schichtsili caten the individual layers by polyvalent polyoxy cations (eg., [Al₁₃O₄ (OH) ₂₄ (H₂O) ₁₂] ⁷⁺ or [Zr₄ (OH) ₈ (H₂O) ₁₆] ⁸⁺ bridged, so that the individual layers are effectively supported by "pillars" against each other. The layer spacings are depending on the intercalated cation about 0.4 to 2.7 nm, z. 0.8 to 0.9 nm for Al "pillared clays" and 0.9 to 1.1 nm for Zr "pillared clays". Examples of unbridged phyllosilicates can be found in "Ullmanns Enzyklopadie der technischen Chemie", Volume 23 (1983), pages 311 to 323. Examples of "pillared clays" are in the article by F. Figueras "Pillared Clays as Catalysts" in Catal. Rev. Sci. Eng., 30 (3), pp. 457-499 (1988).

The particularly preferred supports according to the invention are the hydrotalcites and the hydrotalcite-like isotypes in which the magnesium ions are replaced by other divalent ions such as Zn ²⁺ or Cu ²⁺ and the aluminum ions by other trivalent ions such as Cr ³⁺ and / or Fe ³⁺ or partially replaced. As a result, the micro pore size can be varied. This is generally between about 0.4 and 0.9 nm.

The absorption / oxidation agent according to the invention is coated with an oxidizing agent, which is preferably selected from the group of Mn ^(VII) , V ^(V) or Cr ^(VI) compounds. Examples of these compounds are the permanganates, such as KMnO₄, vanadium pentoxide or alkali metal, ammonium or Erdalkalivanadate (eg., NH₄VO₃) or CrO₃ or the corresponding alkali or Erdalkalichromate or bichro mate, such as Na₂CrO₇.

Preference is given to compounds which, due to the strong Electronegativity of the oxygen decomposing on the hydrides such as alkali and alkaline earth permanganates, NH₄VO₃ and / or Na₂CrO₇.

The oxidizing agents can also be formed in situ. So For example, silver may be deposited on the carrier, the intermediate is converted into Ag₂O, if the removing gaseous hydrides and / or halogen compounds Oxygen is fed.  

Some of the carriers used according to the invention react alkaline due to their alkali or alkaline earth metal content, whereby the oxidative decomposition or the absorptive bond of acidic reactants and / or decomposition pro is favored. This effect can be increased if the wearer additionally with one or more basic compound (s), in particular with at least one Hydroxide or other alkaline reacting compound a metal of the alkali or alkaline earth group, in particular of K, Na, Cs, Mg and / or Ca, is activated.

The absorption / oxidation agents according to the invention are preferably in the form of round logs, monoliths, granules, Extrudates or tablets before, which has the advantage that the Flow resistance is reduced in the reactors.

The carriers can be treated with binders (eg aluminum metahydrate) or other alumina hydrates into agglomerates wherein the carriers are preferably in dry form be mixed. At this stage can also alkaline Activator substances in solid or preferably dissolved Form are added. Subsequently, the Oxidationsmit Added tel in dissolved form, and the mixture is preferred wise plasticized by kneading.

For the production of extrudates, the plastic mass without further additives directly to the desired diameter extru diert and dried. The obtained absorption / oxidation agent can be used in this form. This is true especially for the permanganate-containing compositions, where no further temperature treatment is carried out. The chromate or vanadate-containing compositions are appropriately calcined, preferably at temperatures of about 350 to 550 ° C.

For the production of tablets, the plasticized mass  dried, granulated over a sieve, with a small amount a pressing assistant, such as graphite, mixed and into tablets pressed. The tablets can then be calcined.

For the production of monoliths, the plastic mass on set a suitable stiffness and extruded into honeycomb diert. Subsequently, the monolithic honeycombs can be calcined become.

Of course, the plastic mass can also be dried directly and optionally calcined and then granulated, for example, to an average particle size of about 1 to 5 mm.

Alternatively, the plastic mass can be calcined directly, then granulated, and then in a conventional manner under Use of a pressing aid to tablets are pressed.

The invention will be elucidated by the following examples tert.  

Examples 1-6

1500 g support (1st X zeolite [0.74 nm]; 2nd Y zeolite [0.74 nm]; 3. Mordenite [0.3 nm]; 4. pentasil [(0.54 x 0.52) nm]; 5. Ca Bentonite [1.5 nm]; 6. hydrotalcite [0.78nm]), 1500g of aluminum metahydrate (binder) and 243 g Ca (OH) ₂ were dry in a kneader mixed. 363 g of KMnO₄ were dissolved in 500 ml of water solved. The solutions became common to the solid mixture metered, wherein for setting the optimum viscosity of water was added (500 to 1000 ml); the mixture became 30 - 45 plasticized. The mixture was mixed with a double-Z kneader kneaded and in an extruder (Händle PVZM 8B) too Extruded moldings with a diameter of 1.5 mm. The Shaped bodies were broken into lengths of about 3 mm and 12 Hours dried at 120 ° C.

Example 7

The procedure was as in Example 6, but instead of of KMnO₄ 350 g Na₂Cr₂O₇ were used. After drying the broken extrudates were at 250 ° C for 3 hours calcined.

Example 8

The procedure was as in Example 6, but instead of of KMnO₄ 327 g NH₄VO₃ were used. The broken one Extrudates were calcined at 500 ° C for 3 hours.

Example 9

The procedure was as in Example 6, but the KMnO₄- Content was halved (182 g).  

Example 10

It was worked as in Example 6, but the double KMnO₄ content (726 g) was used.

Example 11

1500 g of hydrotalcite, 1500 g of aluminum metahydrate, 363 g of KMnO₄, and 243 g of Ca (OH) ₂ were mixed with 2 liters of water and how plasticized according to Example 6. Further processing took place as in Example 6.

Example 12

1500 g of hydrotalcite, 1500 g of aluminum metahydrate and 363 g KMnO₄ were mixed with 2 liters of water and plasticized. Then, the procedure was continued as in Example 6.

Comparative Example 1

As a comparison, a commercially available Hopcalite was the composition 49.5 wt .-% MnO₂, 21.8 wt .-% CuO, 24.8 Wt .-% Al₂O₃, 3.80 wt .-% Ag₂O and 0.1 wt .-% K₂O in the form of Extrudates with a diameter of 1.5 mm and a length used by about 5 mm, as described in EP-B-0 309 099 is described.

Comparative Example 2

Following the procedure of Example 1, an absorption / Oxidizing agent with the composition 54 wt -.% Al₂O₃, 16 % By weight of SiO 2, 11% by weight of CaO and 1.4% by weight of KMnO 4.

applications

The described absorption / oxidation agents (absorbers)  were in a steel tube with an inner diameter of 25 mm and a length of 150 mm. The absorber volume was 60 ml. The upper and lower end of the bed was with Covered with quartz wool. The measuring gas used was a mixture of 20 Vol. -% SiH₄ or AsH₃ in nitrogen. The systems were added Room temperature with the sample gas at a flow of 250 ml / min (corresponding to a linear velocity of about 0.9 cm / s), and the time to gas breakthrough (End point detection) was measured with an ICP spectrometer (type "Modu le ", Spectro, Cleve). From the data obtained the capacity was in liters hydride / kg absorption / oxidation agent calculated.

The results obtained for SiH₄ / N₂ as a test gas or AsH₃ / N₂ as test gas are summarized in Table I and Table II.

Furthermore, in the same apparatus was the same Test conditions a test gas with 20 vol.% SiF₄ and 80 vol.% N₂ examined. The initial concentration was as in the Hydrides determined. The results obtained are in Table III indicated.

Table I Test gas SiH₄ / N₂ Input concentration 20%, initial concentration - <1 ppm example Capacity [1 SiH₄ / 1 absorber] Comparative Example 1 30 Comparative Example 2 45 example 1 60 Example 2 60 Example 3 60 Example 4 60 Example 5 55 Example 6 160 Example 7 100 Example 8 110 Example 9 80 Example 10 190 Example 11 100 Example 12 75

Table II Test gas AsH₃ / N₂ Input concentration 20%, initial concentration <1 ppm example Capacity [1 AsH₃ / 1 absorber] Comparative Example 1 30 Comparative Example 2 40 example 1 50 Example 2 50 Example 3 50 Example 4 50 Example 5 45 Example 6 70 Example 7 60 Example 8 60 Example 9 55 Example 10 80 Example 11 50 Example 12 45

Table III Test gas SiF₄ / N₂ Input concentration 20%, initial concentration <1 ppm example Capacity [1 SiF₄ / 1 absorber] Comparative Example 1 23 Comparative Example 2 45 example 1 50 Example 2 50 Example 3 45 Example 4 55 Example 5 55 Example 6 180 Example 7 120 Example 8 100 Example 9 110 Example 10 200 Example 11 130 Example 12 100

The results show that the composition of the invention a particularly high oxidation capacity for SiH₄ (Table I) or AsH₃ (Table II). in principle However, there is activity towards all hydrides, as well compared to many halogen compounds (Table III). The Comparison of Examples 11 and 12 shows that the addition of a Activator (Ca (OH) ₂) in Example 11 to increase the Absorption capacity for SiH₄ and AsH₃ leads.

The absorption capacity for SiF₄ is in the Invention compositions better than the Vergleichzu compositions (see Table III). Furthermore, as with the Hydrides Example 11 has a better absorption capacity than Example 12.

Claims (8)

1. absorption / oxidation agent for removal of environmen- loading gaseous hydrides and / or halogen compounds of elements of Group III, IV, V and / or VI or subgroup VI of the Periodic Table, characterized by a macroporous support with a one, two - or three-dimensional intrinsic (inner) microporous microporous structure with micropores of about 0.3 to 3 nm, which is coated with an oxidizing agent. 2. absorption / oxidation agent according to claim 1, characterized characterized in that the micropore width of the carrier is about 0.4 to 2, preferably about 0.5 to 1.5 nm. 3. absorption / oxidation agent according to claim 1 or 2, since characterized in that the carrier comprises a zeolite Double layer hydroxocarbonate and / or an optionally represents bridged sheet silicate. 4. absorption / oxidation agent according to claim 3, characterized characterized in that the double-layered hydroxocarbonate a Hydrotalcite or a hydrotalcite isotype. 5. absorption / oxidation agent according to one of the preceding claims, characterized in that the oxidizing agent contains at least one Mn ^(VII) , V ^(V) or Cr ^(VI) compound. 6. absorption / oxidation agent according to one of the preceding Claims, characterized in that the carrier additional with one or more basic compound (s), in particular with at least one hydroxide of a metal the alkali or alkaline earth group, in particular of K, Na, Cs, Mg and / or Ca is activated.   7. absorption / oxidation agent according to one of the preceding Claims, characterized in that it is in the form of round ling, monoliths, granules, extrudates or tablets is present. 8. Use of the absorption / oxidation agent according to a of claims 1 to 7 for the removal of polluting gaseous hydrides and / or halogen compounds of Elements from the group III, IV, V and / or VI of the Periodic table, in particular of B₂H₆, SiH₄, GeH₄, PH₃, AsH₃, SeH₂, SiCl₄, SiH₂Cl₂, SiF₄, NF₃, SiF₄, NF₃, WF₆, SeH₂ and / or SeF₆.