DE112005003497T5 - Process for the preparation of hydrochlorosilanes - Google Patents

Abstract

method for producing one or more hydrochlorosilanes, comprising the conversion of hydrogen, a chlorine source and silicon particles, a hydrochloride accelerator metal by chemical Depositing was deposited, comprising the removal of oxygen from the surface the silicon particles, reducing a reducible substance, which includes the hydrochlorination accelerator metal, and the deposition of the hydrochlorination accelerator material to the oxygen Silicon particles.

Description

Background and abstract

These The invention relates to a process for the preparation of hydrogen-containing Chlorosilanes, in particular trichlorosilane and dichlorosilane, of silicon.

It is known to produce trichlorosilane by reacting silicon tetrachloride with hydrogen and silicon without using a catalyst or accelerator (Ingle, et al. US 4526769 ). The entire reaction process is represented by: 3SiCl ₄ + 2H ₂ + Si → 4HSiCl ₃ (1)

It is also known that trichlorosilane can be prepared by reacting hydrogen chloride and silicon without a catalyst, represented by: 3HCl + Si → HSiCl ₃ + H ₂ (2)

It is also known that the reaction rate and the reaction selectivity can be increased if certain metals, such as copper, are used (Breneman, et al. US 4676967 ). The manner in which such a catalyst is incorporated into the process has been the subject of several publications. Further, a catalyst is required to remove significant amounts of dichlorosilane through the reaction: 2HCl + Si → H ₂ SiCl ₂ (3) to create.

Wagner ( US 2,499,009 ) used large amounts of copper halides in a stepwise roasting process to produce a copper-silicon material suitable for promoting the formation of dichlorosilane. However, the batch processing, the high annealing end temperature, and the high concentration of copper required made his method impracticable and posed serious environmental challenges to the disposal of the waste containing the large amounts of copper. Downing ( US 4314908 ) teaches a process in which copper oxide is roasted with silicon for metallurgical purposes in a hydrogen atmosphere at an elevated temperature to produce a substantially uniform distribution of copper on the surface of the silicon. Mui ( US 5250716 ) describes the formation of a copper-silicon alloy by reacting copper (I) chloride vapor with silicon. Wakamatsu ( DE 196 54 154 ) teaches that trichlorosilane can be produced using a copper silicide catalyst. Margaria et al. ( US 6057469 ) describes copper deposited on the surface of silicon granules. Bulan et al. ( US patent application 2004/0022713 A1 ) indicates that, for copper to be effective, it must be in a granular form that is 30 to 100 times finer than the silicon particles. Alternatively, the copper can be incorporated into the bulk of the silicon by adding copper in the form of elemental copper metal or as a copper compound to the silicon during metallurgical processing. However, such incorporation into the bulk must be done with a much higher copper concentration to achieve the same catalytic effect as when the copper is deposited only on the surface of the silicon. The higher levels of copper required by the addition to the bulk presents a challenge to the effective removal of the spent silicon containing the additional copper.

In all of these prior art processes, considerable effort has been made to produce a very finely divided form of copper and a subsequent, carefully controlled process of closely and efficiently contacting this fine form of copper with a silicon material. Performing the copper coating in a zone outside the hydrogenation reaction zone, eg downing (FIG. US 4314908 ) also has additional handling issues to prevent the treated material from re-forming an oxide coating which subsequently inhibits the hydrogenation reaction. These special processes invariably increase the cost and complexity of the entire manufacturing process.

All Prior art methods recognize the effect of natural surface oxide considering silicon the role of the accelerator or catalyst not. A natural one Oxide on the silicon metal prevents the effective binding of copper to the silicon surface, what in turn reduces the effective incorporation of the catalyst or the benefit of the catalyst is delayed until the natural oxide removed by another chemical process within the process can be. The natural Oxide can be removed a bit by extreme grinding. But if Once the oxide is removed, the silicon must be in an oxygen-free state State, a difficult and expensive procedure in practical commercial ventures.

It would therefore be useful to have a simplified process for forming an active catalyst species to improve the production of hydrochlorosilanes. With an active and active catalyst, hydrochlorosilanes can be generated from the reaction of silicon and hydrogen with a chlorine source. The source of chlorine may be hydrogen chloride, silicon tetrachloride or a combination of these two. Further, depending on the purpose, the ratio of dichlorosilane and trichlorosilane can be changed by the hydrogen: Chlo Rid ratio, the gas residence time, and the reaction temperature and pressure are changed when the effective catalyst is used.

Detailed description

In order to produce an effective catalyst using silicon, the difficulties presented by a native oxide on the surface of the silicon can be overcome by employing a type of reaction in which the silicon is first exposed to a reducing atmosphere to remove the surface oxide. Hydrogen gas at an elevated temperature can do this by the reaction: H ₂ + SiO ₂ (solid) → Si (metal) + H ₂ O (vapor) (4) to reach.

The resulting silicon surface is then substantially free of oxide, if these are in an oxygen-free state Environment is maintained.

Copper (I) chloride is a reducible substance that is rapidly reduced by hydrogen at elevated temperatures: CuCl + H ₂ → 2HCl + Cu (metal) (5)

The Reduction of the reaction (5) is autogenous in a hydrogen atmosphere at temperatures above about 275 ° C.

Commercially available Silicon for metallurgical purposes or pure silicon is used as starting material for the Preparation of Trichlorosilane by the Reaction (1) or (2) used. Such silicon inherently has a natural one Oxide, which is present on the silicon surface. After the usual In commercial practice, the silicon is ground and sieved to to provide a particle size for themselves the specific requirements of the chosen process planning is suitable. A particle size of about 200 microns is for Many methods are suitable, but the size is irrelevant, as long as the particles are small enough to be in one mixing environment, such as in a fluid bed reactor or a stirred bed reactor, to work, with gases easily brought into contact with the silicon particles can be.

By is the alloying of the effective amount of copper on the oxide-free silicon surface the utilization of copper is pretty good and the amount of copper, needed to achieve the advantage is, is very low. This advantage is achieved by adding additional Amounts of copper and silicon, as needed, are fed while the production of hydrochlorosilanes at normal temperature and pressure progresses.

To produce the hydrochlorosilanes generally according to reactions (1, 2 or 3), silicon is placed in a vessel such as a fluid bed reactor or a mechanically stirred bed reactor and the reactor is charged to the usual operating conditions of 275 ° C-550 ° C with a feed brought by gaseous hydrogen and a chlorine source. The source of chlorine may be hydrogen chloride, silicon tetrachloride or a combination thereof. In the absence of hydrogen chloride, the non-catalyzed reaction finds: SiCl ₄ + H ₂ → HCl + HSiCl ₃ (6) instead of silicon, and a small amount of HCl (<1%) is formed. The temperature, reactor residence time and hydrogen and chloride concentrations can be adjusted to produce the required product mixture. The HCl aggressively attacks the silicon at any temperature above 275 ° C via reaction (2). The combination of reactions (2) and (6) leads to the reaction (1). The effect of the silicon is to remove HCl from the reaction environment and shift the equilibrium concentration of reaction (1) to the right, thereby increasing the overall yield of hydrochlorosilanes.

At the same time, the surface of the silicon is attacked by the hydrogen to remove surface oxides and adsorbed moisture: H ₂ + SiO (H) → Si + H ₂ O (7)

The reactions (6) and (7) are operated with an excess amount of H ₂ . Reactions (6) and (7) taken together remove all oxides or the moisture content of at least part of the surface of the silicon. The resulting substantially oxide-free silicon surface is then able to effectively take up and bind an active copper metal.

Copper, most effectively in the form of copper (I) chloride (CuCl), is then added to the reactor and reduction with excess hydrogen at 275 ° C to 550 ° C is accomplished by reaction (5) to form a copper metal and to form additional HCl. The atomic-based copper is deposited on at least a portion of the substantially oxide-free surface of the silicon by chemical vapor deposition to form a copper-silicon alloy. In particular, particles of CuCl are reduced in situ in close proximity to the oxide-free silicon to form the effective alloy catalyst. The copper deposit may consist of randomly arranged "islands" of copper on the surface of the silicon. The copper-silicon surface alloy is a very effective catalyst for the reactions (1), (2) and (3). Very successful results are obtained with copper levels of less than 1.0%. A particularly efficient mode of operation is achieved when copper amounts to 0.01% to 0.5% of the mass of the copper-alloyed silicon. From an environmental point of view, it is considered that the lower the copper usage is to achieve the required yield of hydrochlorosilanes, and the small amounts identified herein are an order of magnitude lower than those previously required.

Other reducible copper compounds may additionally or as a substitute for the copper chloride be used. It can Copper oxide or mixtures of copper oxide and copper metal used become. However, if these are used, the additional Moisture content resulting from the hydrogen reduction of copper oxide is formed, leading to a loss of chlorosilane by hydrolysis of the Chlorosilanes to siloxanes, high-boiling impurities, the one pose serious problem in the elimination. Another suitable reducible material is chloroplatinic acid. If Silicon tetrachloride is the source of chlorine should be the accelerator metal so chosen be that this the hydrochlorination reaction in the presence of Silicon tetrachloride and hydrogen can promote. When the chlorine source Hydrogen chloride is, the accelerator metal should be a metal that is the hydrochlorination of silicon in the presence of hydrogen chloride and promote hydrogen can.

If a material such as an accelerator metal is not bonded to the silicon surface is, it is in the catalyzing of the reaction (1) ineffective. For example, if an accelerator metal on one otherwise non-reactive surface, like silica or carbon, does not become a promoter Effect observed. The accelerator metal must be on the surface of the Silicon are present. The rapid consumption of silicon only occurs in the area immediately adjacent to the place of the accelerator metal adjacent to the oxide-free silicon surface.

The Accelerator metal-silicon alloy need not be uniform on the surface of silicon. It only has to be sufficient Quantity will be available. And the removal of the natural oxide on the silicon does not have to be complete or be uniform, only sufficient to the amount of the deposited Accelerator metal record.

A increased Temperature is maintained to make the one or the other several desired ones To reach Hydrochlorosilane. To the production of trichlorosilane of silicon tetrachloride according to the reaction (1) to favor, For example, the temperature inside the reactor is best kept at 400 ° C to 500 ° C. To the production of trichlorosilane and dichlorosilane from HCl according to the reactions (2) and (3) to favor, the temperature inside the reactor is best kept at 275 ° C to 350 ° C.

Of the Reactor should be of a type that deoxidizes the mixing Silicon containing the reducible substance comprising the promoter metal, relieved, so that the decomposing reducible substance on the surface of silicon on which the accelerator metal is to be deposited. Especially suitable reactors include fluidized bed reactors, wherein the mixing power is provided by moving gas, mechanically moved Bed reactors, such as a reaction rotary kiln and stirred bed reactors, and tower reactors, wherein the silicon and copper chloride particles by the gravitational force against an ascending stream of hydrogen-rich gas can fall. The hydrogenation reaction can also be carried out in a dilute phase (less solid Particles in proportion to the reactor volume) become.

In the practical implementation This process will produce fresh silicon for addition to the hydrochlorination reactor needed to maintain a substantially constant stock of material, since the silicon is consumed by the reaction (1), (2) or (3) and hydrochlorosilanes are removed from the reactor. The granular silicon can either continuously or discontinuously in small increments supplied become. In the simultaneous supply of copper (I) chloride powder with the grained Silicon can be used as a single, simplified system. The copper (I) chloride is therefore preferably directly to the Given reaction zone, where it breaks down into copper and on the substantially oxide-free surface of the silicon already present in the reaction zone. The fresh silicon fed together with the cuprous chloride will delight a short treatment period in the reaction zone to his natural Losing oxide and being so for the reaction with the copper (I) chloride prepared at the next Opportunity is added. With this procedure must be no special precautions are taken to either the silicon or to pretreat the copper-containing substance, and the overall result is an advantageously high rate of production of hydrochlorosilanes at normal temperature and pressure.

Other materials that promote the hydrochlorination or the formation of proportionally higher yields of more hydrogenated chlorosilila can be added in a similar way. In choosing the shape of the accelerator material, the best results are achieved with those forms that can either be vaporized at the reaction conditions or reduced by hydrogen at the elevated temperature present in the reaction zone to deposit an accelerator metal. Such materials include the oxides, carbonates and chlorides of zinc and tin and the chlorides and carbonates of ruthenium, rhenium, platinum, silver, osmium and nickel.

The following, non-limiting Examples illustrate the implementation of this method:

EXAMPLE 1

A fluid bed reactor 122 cm in diameter was loaded with 13,000 kg of metallurgical grade silicon ground to a mean particle diameter of 200 microns. The reactor was started by flowing 3350 m ³ / h of hydrogen at a temperature of 500 ° C and a pressure of 3 MPa. After the reactor had reached operating temperature, silicon tetrachloride vapor was started at a flow rate of 3350 m ³ / h at a temperature of 500 ° C and a pressure of 3 MPa. A reactor product containing 20 mole percent trichlorosilane based on a hydrogen-free base was obtained. When the reactor amount decreased by 150 kg due to the consumption of silicon by the reaction (1), the periodic addition of metallurgical grade silicon was started and the process continued in this manner for several days. After three days of operation, the equivalent of 72% of the original loaded silicon mass had been consumed and replaced with an equal amount of fresh metallurgical silicon. At this point, a mixture of metallurgical grade silicon and cuprous chloride was prepared by adding 4.5 kg of cuprous chloride to a bulk bag containing 1363 kg of silicon. Using a pneumatic conveyor belt to transport the copper / silicon mixture to a sluice hopper at the top of the fluid bed reactor, the normal metallurgical reactor feed of metallurgical silicon was replaced by the copper / silicon mixture. Shortly after the addition of the copper (I) chloride / silicon mixture, it was found that the hydrogen consumption had increased significantly. The reactor product, based on a hydrogen-free base, increased to 25 mole percent trichlorosilane. As long as the copper (I) chloride / silicon was further added to increase the consumed silicon, the yield of trichlorosilane remained at the higher level. When the addition of copper chloride was stopped, the yield of trichlorosilane began to decrease and eventually returned to the original level before the start of the supply of copper (I) chloride. The rate of decrease indicated that the copper had attached to the silicon so that it was washed out of the reactor only when the bonded silicon particle was chemically etched to a size less than the entrainment size (~ 15 microns). was. Analysis of the reaction mass after the trichlorosilane conversion had returned to its precatalyst level indicates that no copper accumulated while the amount of copper in the reactor leached fine silicon dropped in direct proportion to the reduced yield of trichlorosilane.

This Example shows that the addition of a reducible substance, which contains an accelerator metal, directly to the reaction zone, in the already oxide-free silicon is present, to a higher Conversion into trichlorosilane leads. It also shows that the copper chloride is tight with the silicon linked and that the yield of trichlorosilane directly with the concentration related to copper in the reaction mass.

EXAMPLE 2

Fifty grams of ground metallurgical grade silicon (average particle size = 200 microns) were placed in a 25 mm diameter test tube, held in a small oven and heated to a temperature of 525 ° C with a flow of hydrogen. Silicon tetrachloride was placed in a thermostated reservoir maintained at 25 ° C. The provision was made by bubbling hydrogen through the reservoir to saturate it with silicon tetrachloride and then flowing the saturated hydrogen, along with additional hydrogen to obtain a H ₂ : SiCl ₄ molar ratio of 2.0, into the bottom of the silicon containing test tube. The total hydrogen flow was 12 cm ³ / min. At the effluent of the reaction tube, a membrane was installed which allowed the collection of a small gas sample for analysis by gas chromatography. At a reactor temperature of 525 ° C, the yield of trichlorosilane was 4.6%.

EXAMPLE 3

Using the same apparatus as in Example 2, 49 g of metallurgical grade silicon was placed in the reaction tube and heated to 525 ° C in a hydrogen atmosphere. After the silicon was exposed to the hot hydrogen, 0.39 g of copper (I) chloride was added to the reactor while hydrogen continued to flow through. Then the water became flow through the thermostated reservoir of silicon tetrachloride passed and tested the outflow. The concentration of trichlorosilane based on a hydrogen-free base was 6.14%.

EXAMPLE 4

Under Using the same apparatus as in Example 2, the reactor loaded with 50 g of silicon, on which previously 1% platinum was deposited. The trichlorosilane concentration when reacted at 525 ° C with the Standard flow of hydrogen and silicon tetrachloride 6.05%, based on a hydrogen-free Base.

EXAMPLE 5

Under Using the same apparatus as in Example 2, the reactor with a mixture of 49.9 g of silicon for metallurgical purposes and 0.1 g of 5% platinum loaded on silica gel. The result was a trichlorosilane concentration, based on a hydrogen-free base, of 4.28%.

EXAMPLE 6

Under Using the same apparatus as in Example 2, the reaction tube with 49 g white Quartz and 0.1 g of 5% platinum on activated carbon filled. Under the same standard conditions like that used in Example 2 was the trichlorosilane concentration in the effluent <0.1%.

In this explanatory Examples show that one is both an active accelerator metal as well as a source of metallic silicon must have to the Promote hydrogenation reaction. The absence of the accelerator metal leads to reduced yields (Example 2), in the absence of silicon, but with one active hydrogenation catalyst, no conversion takes place (example 6). To provide the better conversion, the active one must Accelerator metal be closely connected to the silicon (examples 2 and 4 compared to Example 5).

EXAMPLE 7

Using the same apparatus as that of the reactor with 50 g of silicon can be described in Example 2 are loaded for metallurgical purposes, and / are heated min hydrogen chloride at 300 ° C under a flow of 12 cm ³ / min of hydrogen and 6 cm ^3. After the silicon has been exposed to the mixture of hot hydrogen and hydrogen chloride for several hours, 0.4 g of copper (I) chloride is added to the reactor while the hydrogen / hydrogen chloride flow is continued. In a test as in Example 2, the effluent contains trichlorosilane and several percent of dichlorosilane. Without the copper-silicon alloy catalyst, the amount of dichlorosilane would only be traces.

In In the present specification, methods for the production of Hydrogen-containing chlorosilanes with reference to preferred embodiments described. Other embodiments will be apparent to one skilled in the art in light of this description or the execution the method disclosed herein. The description and the examples should be considered as exemplary only during the actual scope the invention and the inventive idea by the following claims become.

Summary

Process for the preparation of hydrochlorosilanes

Hydrogen-containing Chlorosilanes are prepared by reacting with hydrogen Silicon tetrachloride and / or hydrogen chloride and silicon, wherein the surface of silicon by chemical vapor deposition of one or more catalytic Materials, such as copper, has been modified.

Claims (26)

Process for the preparation of one or more hydrochlorosilanes, comprising reacting hydrogen, a chlorine source and silicon particles a hydrochloride accelerator metal by chemical vapor deposition has been deposited, comprising removing oxygen from the surface of the Silicon particles, reducing a reducible substance, the comprising the hydrochlorination accelerator metal, and the depositing of the hydrochlorination accelerator material to the oxygen Silicon particles. The method of claim 1, wherein the reacting at 275 ° C to 550 ° C is performed. Process according to claim 1 for the preparation of hydrochlorosilanes, including Trichlorosilane and dichlorosilane, wherein: the chlorine source silicon tetrachloride is; and the accelerator metal is a metal that completes the hydrochlorination reaction in the presence of silicon tetrachloride and hydrogen can promote. The method of claim 3, wherein reacting at 400 ° C to 500 ° C is performed. The process of claim 1 for the preparation of hydrochlorosilanes, including trichlorosilane and dichlorosilane, wherein: the source of chlorine is hydrogen chloride; and the accelerator metal is a metal that the Hy drochlorination of silicon in the presence of hydrogen can promote. The method of claim 5, wherein reacting at 275 ° C to 350 ° C is performed. Process for the preparation of one or more hydrochlorosilanes, full: Removing oxygen from at least part of the surface a silicon particle having a surface oxide by heating the Particle in a reducing atmosphere to a silicon particle to produce at least one oxide-free region; deposit a metal that can promote the hydrochlorination of silicon, to the oxide-free region to an accelerator metal-silicon surface alloy by chemical vapor deposition, involving reduction a reducible substance comprising the metal; and Implement of hydrogen, a chlorine source and the accelerator metal-alloyed Silicon to produce one or more hydrochlorosilanes. The method of claim 7, wherein the removing, the Deposit and transfer at 275 ° C up to 550 ° C carried out become. Process according to claim 7 for the preparation of hydrochlorosilanes, including Trichlorosilane and dichlorosilane, wherein: the chlorine source silicon tetrachloride is; and the accelerator metal is a metal that undergoes hydrochlorination of silicon in the presence of silicon tetrachloride and hydrogen promote can. The method of claim 9, wherein the removing, the deposition and the reaction at 400 ° C to 500 ° C are performed. Process according to claim 7 for the preparation of hydrochlorosilanes, including Trichlorosilane and dichlorosilane, wherein: the chlorine source hydrogen chloride is; and the accelerator metal is a metal that undergoes hydrochlorination of silicon in the presence of hydrogen. The method of claim 11, wherein the removing, the deposition and the reaction are carried out at 275 ° C to 350 ° C. Process for the preparation of one or more hydrochlorosilanes, full: Combine hydrogen, a chlorine source and silicon, that's a surface oxide having; Heat of the hydrogen, the chlorine source and the silicon to a sufficient Temperature, so that oxygen from at least one area of the surface the silicon is removed; Contact the silicon with an oxide-free region with a reducible substance containing a Metal that can promote the hydrochlorination of silicon; Heating the reducible substance to a sufficient temperature, so that the substance is reduced and the metal is on the oxide-free Area deposits to an accelerator metal silicon surface alloy to create; and Reacting the hydrogen, the source of chlorine and the accelerator metal-alloyed silicon to one or more Hydrochlorosilane to produce. The method of claim 13, wherein the heats at 275 ° C up to 550 ° C and react at 275 ° C up to 550 ° C carried out becomes. Process according to claim 13 for the preparation of hydrochlorosilanes, einschlißlich Trichlorosilane and dichlorosilane, wherein: the chlorine source silicon tetrachloride is; and the accelerator metal is a metal that undergoes hydrochlorination of silicon in the presence of silicon tetrachloride and hydrogen promote can. The method of claim 15, wherein the heats at 400 ° C up to 500 ° C carried out and the reaction at 400 ° C. up to 500 ° C carried out becomes. Process according to claim 13 for the preparation of hydrochlorosilanes, including Trichlorosilane and dichlorosilane, wherein: the chlorine source hydrogen chloride is; and the accelerator metal is a metal that undergoes hydrochlorination of silicon in the presence of hydrogen. The method of claim 17, wherein the heats at 275 ° C up to 350 ° C and react at 275 ° C up to 350 ° C carried out becomes. The method of claim 1, 7 or 13, wherein the Accelerator metal less than 0.1% of the mass of accelerator metal-alloyed Silicon is. The method of claim 1, 7 or 13, wherein the Accelerator metal 0.01% to 0.5% of the mass of the accelerator metal-alloyed Silicon is. A method according to claim 1, 7 or 13, wherein the reducible substance is copper (I) chloride. A method according to claim 1, 7 or 13, wherein the reducible substance is copper oxide. A method according to claim 1, 7 or 13, wherein the reducible substance is chloroplatinic acid. Method of making one or more hydrochloric acid, comprising: heating a mixture comprising hydrogen, a source of chlorine and silicon having a surface oxide in a vessel at a sufficient temperature and for a sufficient period of time so that oxygen is removed from at least a portion of the surface of the silicon ; Contacting a reducible substance comprising a metal capable of promoting the hydrochlorination of silicon with the silicon having an at least partially oxide-free surface inside the vessel in a reducing atmosphere and at a sufficiently high temperature that the substance is reduced and the metal depositing on the oxide-free surface of the silicon to produce an accelerator-metal-silicon surface alloy; and reacting the hydrogen, the chlorine source and the accelerator-metal-alloyed silicon within the vessel to produce one or more hydrochlorosilanes. Process for forming an accelerator metal-bearing Reaction mass, the process of maintaining silicon particles, Hydrogen, a chlorine source and a reducible substance, comprising a metal capable of promoting hydrochlorination, in the vessel at 275 ° C to 550 ° C and for a sufficient Includes time so that oxygen is removed from the surfaces of the silicon particles is reduced, the reducible substance and the metal itself on the surfaces the silicon particles deposited by chemical vapor deposition to a To form accelerator metal silicon surface alloy. The method of claim 25, wherein: the reducible Substance is copper (I) chloride; and the metal is copper, that on at least part of the surface of the silicon by chemical Vaporizing is deposited to a copper-silicon surface alloy to build.