WO2014116341A1

WO2014116341A1 - Mehtod for preparing a trihalosilane

Info

Publication number: WO2014116341A1
Application number: PCT/US2013/069522
Authority: WO
Inventors: Aaron COPPERNOLL; Catharine HORNER; Krishna Janmanchi
Original assignee: Dow Corning Corp
Current assignee: Dow Silicones Corp
Priority date: 2013-01-25
Filing date: 2013-11-12
Publication date: 2014-07-31
Anticipated expiration: 2015-07-25

Abstract

A method of preparing a reaction product including a trihalosilane includes contacting a supported copper catalyst with H₂ and a silicon tetrahalide at a temperature of at least 300 °C to form the reaction product. The supported copper catalyst contains Cu and optionally one or more of Au and Mg. The method is performed without a separate step of adding a hydrogen halide after contacting the supported copper catalyst with the silicon tetrahalide.

Description

METHOD FOR PREPARING A TRIHALOSILANE

[0001] A number of methods of producing trihalosilane have been disclosed. For example, the reaction of HCI with zero-valent silicon has been described. In addition, trichlorosilane has been produced by passing silicon tetrachloride (SiCl4), H2, and HCI over zero-valent silicon (Si⁰) at 600 °C. Furthermore, trichlorosilane (HSiCl3) has been produced by passing H2 and S1CI4 over silicon particles in a first stage, adding HCI to the effluent from the first stage, and then passing the effluent and HCI over more silicon particles optionally containing a catalyst (i.e., CuCI) in a second stage. Finally, HSiCl3 has been produced by passing H2, S1CI4, and HCI over Si⁰ containing homogeneously distributed copper silicide.

[0002] Recently, Dow Corning developed a multiple step method of preparing a trihalosilane. The method includes the separate and consecutive steps of (i) contacting a copper catalyst with hydrogen gas and a silicon tetrahalide at a temperature of from 500 to 1400 °C to form a silicon-containing copper catalyst comprising at least 0.1 % (w/w) of silicon; and (ii) contacting the silicon-containing copper catalyst with a hydrogen halide at a temperature from 100 to 600 °C to form the trihalosilane.

[0003] While the art describes methods of producing trichlorosilane, these methods have some limitations. Many of these processes employ Si⁰. Since Si⁰ is typically produced by the highly energy-intensive carbothermic reduction of silicon dioxide, using Si° adds costs to these processes. Other methods require multiple processing steps with repeated catalyst regeneration steps necessitated by decreasing yield or selectivity of the method to form the desired trihalosilane.

[0004] Therefore, there is a need for more economical and simpler methods of producing trihalosilanes that avoid the need for using Si⁰, have fewer process steps, and that have more uniform yield and/or selectivity.

BRIEF SUMMARY OF THE INVENTION

[0005] A method of preparing a reaction product comprising a trihalosilane is disclosed. The method comprises:

(i) heating a reactor , at a temperature of at least 300 °C

(ii) contacting, in the reactor, a supported copper catalyst with H2 and a silicon tetrahalide of formula S1X4, where each X is independently halo, and where the supported copper catalyst comprises

a support and a metal selected from copper (Cu) and a combination comprising Cu and at least one element selected from gold (Au) and magnesium (Mg), thereby forming the reaction product comprising the trihalosilane; with the proviso that the method is performed without a separate step of adding a hydrogen halide from outside the reactor after contacting the supported copper catalyst with the silicon tetrahalide, in order for the method to form the trihalosilane.

DETAILED DESCRIPTION OF THE INVENTION

[0006] The method of preparing the reaction product comprising the trihalosilane may comprise:

(p1 ) optionally purging a supported copper catalyst, where the supported copper catalyst comprises

a support and

a metal selected from

Cu and

a combination comprising Cu and at least one element selected from

Au and Mg;

(i) heating a reactor to a temperature at least 300 °C;

(ii) contacting, in the reactor, the supported copper catalyst with H2 and a silicon tetrahalide of formula S1X4, where each X is independently halo; and

(iii) optionally recovering the trihalosilane. The inventors surprisingly found that the trihalosilane is formed by the method without a separate step of adding a hydrogen halide, from a source outside the reactor, after contacting the supported copper catalyst with the silicon tetrahalide.

[0007] The method described herein produces the reaction product comprising the trihalosilane. This method uses silicon tetrahalide as a reactant to form the trihalosilane. Silicon tetrahalide is a byproduct of industrial processes and may be produced using less energy than the energy required to produce Si ⁰. Thus, the method described herein may be more economical than prior processes for producing trihalosilane. Without wishing to be bound by theory, it is thought in some embodiments that the method may generate a hydrogen halide in situ, thereby eliminating the need for a separate step of adding a hydrogen halide from outside the reactor after contacting the supported copper catalyst with the silicon tetrahalide. Therefore, the method described herein may be simpler than prior processes for producing trihalosilane.

[0008] The trihalosilane produced by the method of the invention can be used as a reactant (e.g., raw material) to make high purity polycrystalline silicon such as solar grade polycrystalline silicon, which is used in solar cells or semiconductor grade polycrystalline silicon, which is used in electronic chips. Alternatively, the trihalosilane can be used as a reactant (e.g., raw material) in hydrolysis processes to produce polysiloxane resins, which find use in many industries and applications. Alternatively, the trihalosilane can be used as a reactant (e.g., raw material) to make organosilanes.

[0009] The supported copper catalyst used in the method comprises Cu. Cu may be used as the only metal on the support. Alternatively, the supported copper catalyst may comprise a combination comprising Cu and at least one element selected from Au and Mg. Alternatively, the combination may include all three of Cu, Au, and Mg. When the combination is used, the combination typically comprises 0.1 % to less than 100%, alternatively from 50% to less than 100%, alternatively, 70% to less than 100%, alternatively, from 80% to 99.9%, of Cu, based on the total weight of the combination, with the balance of the combination being at least one of Au and Mg.

[0010] The supported copper catalyst further comprises a support. Examples of supports include, but are not limited to, oxides of aluminum, titanium, zirconium, and silicon; activated carbon; carbon nanotubes; fullerenes; graphene and other allotropic forms of carbon. In one embodiment, the support is activated carbon. Alternatively, the supported copper catalyst may be free of carbon, for example, when alumina or silica is used as the support. "Free of carbon" means that the support is not activated carbon, e.g., the support may be a metal oxide such as alumina, silica, titania, or zirconia. Without wishing to be bound by theory, it is thought that using a supported copper catalyst that is free of carbon may be beneficial to reduce potential for contamination of the reaction product with carbonaceous compounds that could be detrimental to a particular use of the trihalosilane, for example, when the trihalosilane will be used as a raw material to prepare polycrystalline silicon, particularly semiconductor grade polycrystalline silicon.

[0011 ] The supported copper catalyst typically comprises 0.1 % to less than 100%, alternatively 0.1 % to 65%, alternatively 0.1 % to 55%, and alternatively 0.1 % to 35%, of the metal, based on the combined weight of the support and the metal; with the balance being the support. In one embodiment, the metal is copper, and the supported copper catalyst is copper and the support. Alternatively, the metal is a combination of copper and one or more of Au and Mg; and the supported copper catalyst is the combination and the support.

[0012] As used herein, the term "metal" refers to zero-valent metal, a metal compound, or a combination of zero-valent metal and a metal compound. The oxidation number of the metal can vary, for example, from 0 to an oxidation number equal to the metal's group number in the Periodic Table of Elements; alternatively the oxidation number is from 0 to 2, alternatively the oxidation number is 0 for Cu and Au, and the oxidation number 2 for Mg. As used herein, "Periodic Table of the Elements" refers to the lUPAC periodic table of the elements dated June 2012, and available at

http://www.iupac.org/fileadmin/user_upload/news/IUPAC_Periodic_Table-1 Jun12.pdf.

[0013] The supported copper catalyst may be prepared by, for example, dissolving a copper salt, such as cupric chloride or cupric nitrate, in a solvent, such as water or acid, applying this copper salt solution to a support, and reducing the copper salt on the surface of the support. For example, CuC _ can be dissolved in water or hydrochloric acid and mixed with activated carbon. Excess CuC _ solution can then be removed, and the activated carbon-CuCl2 mixture dried. The CuC _ can then be reduced on the activated carbon with hydrogen at high temperature, typically 500 °C, to give the supported copper catalyst. One skilled in the art would understand that the order of addition and reduction and multistep addition of salts and subsequent reduction can also be carried out to prepare the supported copper catalyst. In addition, it is contemplated that the supported copper catalyst may be prepared by separately reducing separate metals on separate supports and then mixing the separately supported metals to form the supported copper catalyst.

[0014] Alternatively, the supported copper catalyst may be prepared by a process comprising impregnating or depositing-adsorbing a metal halide such as a metal chloride

(e.g., CuCI) or metal nitrate (e.g., 0υ(ΝΟ₃)₂) or hydrate thereof (e.g., CuCI-H₂0) and, optionally when there are at least two different metals at least one co-metal chloride or nitrate (e.g., CUCI3 and Mg(N03)₂) on a support such as carbon to give an impregnated or deposited-adsorbed material; and activatingly reducing the metal and, if present the additional metal(s), of the impregnated or deposited-adsorbed material so as to produce the supported copper catalyst, which may be finely divided. The activatingly reducing means adding electrons or hydrogen (e.g., via H₂(g) or a hydride reagent such as NaBH₄) so as to produce a functional catalyst. The "depositing-adsorbing" means accumulating material onto a surface of a support when the material is slurried in an aqueous solution. The resulting deposited-adsorbed material would be retained by the support even after washing the carrier with deionized or distilled water.

[0015] An illustrative example of the depositing-adsorbing technique may be found in Example 3 of WO 201 1 /106194. The "impregnating" means permeating with a wetted, melted, or molten substance substantially throughout a support (e.g. , via an incipient wetness technique), preferably to a point where essentially all of a liquid phase substance is adsorbed, producing a liquid-saturated but unagglomerated solid. An illustrative example of the impregnating technique may be found in Example 1 of WO 201 1 /106194. The support may be activated carbon or a metal oxide, as described above. If desired the supported copper catalyst may be dried, e.g., at 120 °C under vacuum (e.g., <20 kPa) for 4 hours under a bleed of an inert gas (e.g., nitrogen, helium, or argon gas). A method of making the supported metallic catalysts is also described in detail in the EXAMPLES section below.

[0016] The silicon tetrahalide used in the method has the formula S1X4, where each X is independently halo; alternatively X is Br, CI, F, or I; alternatively Br, CI, or I; and alternatively CI. Examples of the silicon tetrahalide include, SiBr4, S1CI4, S1F4, and S1I4.

Alternatively, the silicon tetrahalide is S1CI4.

[0017] The method can be performed in any reactor suitable for the contacting of gases and solids. For example, the reactor configuration can be a packed bed, stirred bed, vibrating bed, moving bed, re-circulating bed, or a fluidized bed (FBR). Alternatively, the reactor may be a FBR. To facilitate reaction, the reactor may have means to control the temperature of the reaction zone, i.e., the portion of the reactor in which H2 and S1X4 contact the supported copper catalyst. The H2 and S1X4 may be fed to the reactor simultaneously; however, other methods of combining, such as by separate pulses, are also envisioned. The H2 and S1X4 may be mixed together before feeding to the reactor; alternatively, the H2 and S1X4 may be fed into the reactor as separate streams.

[0018] The temperature of the reactor in which H2 and S1X4 are contacted with the supported copper catalyst is at least 300 °C. Alternatively, the temperature may be 300 °C to 950 °C; alternatively 450 °C to 950 °C; alternatively 500 °C to 950 °C, and alternatively 750 °C to 950 °C.

[0019] The pressure at which H2 and S1X4 are contacted with the supported copper catalyst can be sub-atmospheric, atmospheric, or super-atmospheric. For example, the pressure is typically atmospheric pressure (0 kilopascals gauge) to 5,000 kilopascals gauge (kPag); alternatively 0 kPag to 415 kPag.

[0020] The mole ratio of H2 to silicon tetrahalide (H2/SiX4) contacted with the supported copper catalyst may be 15:1 to 1 :1 , alternatively 1 1 :1 to 1 :1 , alternatively 10:1 to 1 :1 , alternatively 5:1 to 1 :1 , alternatively 4:1 to 1 :1 , alternatively 3:1 to 1 :1 , alternatively 2:1 to 1 :1 , and alternatively 4:1 to 2:1 . One benefit of the method described herein is that a relatively low H2/S1X4 ratio may be used with good conversion and selectivity, thereby reducing the amount of H2 required. Therefore, alternatively, the relatively low H2/S1X4 molar ratio may be 4:1 to 1 :1 , alternatively 3:1 to 1 :1 , alternatively 2:1 to 1 :1 , and alternatively 4:1 to 2:1 . [0021 ] The residence time for the H2 and S1X4 in the reactor is sufficient for the H2 and

S1X4 to contact the supported copper catalyst and form the trihalosilane. A sufficient residence time for the H2 and S1X4 is typically at least 0.01 seconds (s) ; alternatively at least 0.1 s; alternatively from 0.1 s to 10 minutes (min) ; alternatively from 0.1 s to 1 min; alternatively from 1 s to 10 s. As used herein, "residence time" means the time which a material takes to pass through a reactor system in a continuous process, or the time a material spends in a reactor in a batch process. Alternatively, residence time may refer to the time for one reactor volume of reactant gases to pass through a reactor charged with catalyst. (E.g., the time for one reactor volume of H2 and S1X4 to pass through a reactor charged with supported copper catalyst.)

[0022] The supported copper catalyst is used in a sufficient amount. A sufficient amount of supported copper catalyst is enough supported copper catalyst to form the trihalosilane, when the H2 and S1X4 are contacted with the supported copper catalyst. The exact amount of supported copper catalyst depends upon various factors including the type of reactor used (e.g., batch or continuous), the residence time, temperature, the H2/SiX4 molar ratio, and the particular silicon tetrahalide used. However, a sufficient amount of supported copper catalyst may be at least 0.01 milligram catalyst per cubic centimeter (mg catalyst/cm³) of reactor volume; alternatively at least 0.5 mg catalyst/cm³ of reactor volume, and alternatively 1 mg catalyst/cm³ of reactor volume to the maximum bulk density of the metal oxide supported copper catalyst, alternatively 1 mg to 5,000 mg catalyst/cm³ of reactor volume, alternatively 1 mg to 1 ,000 mg catalyst/cm³ of reactor volume, and alternatively 1 mg to 900 mg catalyst/cm³ of reactor volume.

[0023] There is no upper limit on the time for which the method is conducted. Without wishing to be bound by theory, it is thought that the method may be performed indefinitely as if a hydrogen halide (HX) is formed in situ and reacted to make the trihalosilane as the H2 and S1X4 are contacted with the supported copper catalyst, thereby eliminating the need for separate and consecutive method steps to regenerate the catalyst. For example, step (ii) of the method may conducted for at least 0.1 s, alternatively 1 s to 30 hours (h), alternatively 1 s to 5 h, alternatively 1 min to 30 h, alternatively 3 h to 30 h, alternatively 3 h to 8 h, and alternatively 3 h to 5 h.

[0024] The method described herein may also comprise purging the reactor before the contacting of the supported copper catalyst with the H2 and S1X4. As used herein,

"purging" means to introduce a gas stream to the reactor containing the supported copper catalyst to remove unwanted materials. Unwanted materials are, for example, air, O2 and/or H2O. Purging may be accomplished with a gas such as Ar, He, H2, and/or N2; alternatively H2; alternatively an inert gas such as Ar, He, and/or N2. Alternatively, the purge gas may be S1X4, where X is as defined above.

[0025] The method may further comprise pre-heating and vaporizing the S1X4, such as by known methods, before contacting with the supported copper catalyst. Alternatively, the method may further comprise bubbling the H2 through the S1X4 to vaporize the S1X4 before contacting the vaporous S1X4 with the supported copper catalyst.

[0026] The method may further comprise recovering the reaction product, for example, to purify the trihalosilane produced. The trihalosilane may be recovered by, for example, removing gaseous trihalosilane and any other vapors from the reaction product followed by condensation of the vapors and/or isolation of the trihalosilane from any other compounds in the reaction product by distillation.

[0027] The trihalosilane produced by the method described and exemplified herein has the formula HS1X3, wherein X is as defined and exemplified for the silicon tetrahalide.

Examples of trihalosilanes prepared according to the present process include, but are not limited to, HS1CI3, HSiBrCl2, HSiB^, and HS1I3; alternatively, the trihalosilane produced may be HS1CI3.

EXAMPLES

[0028] These examples are intended to illustrate some embodiments of the invention and should not be interpreted as limiting the scope of the invention set forth in the claims. The comparative examples are non-invention examples. The following table describes the abbreviations and terms used in this specification.

Table 1 . List of abbreviations and terms used herein.

Abbreviation Word

Sel. Selectivity

Selectivity mole % of product, based on weight of product and all

other silicon-containing products

GC gas chromatography

ND none detected

Temp. Temperature

P Pressure

kPag kilopascals (gauge)

min Minutes

s Seconds

U Micro

L Liter

m Meter

[0029] Activated carbon, CuCI₂-2H₂0, AUCI3, and MgCI₂-6H₂0 and other reagents used in the examples were purchased from Sigma Aldrich (Milwaukee, Wl). A method of producing a supported copper catalyst comprising copper, gold, and magnesium was performed by dissolving CuCI₂-2H₂0 (99+%, 1 .0526 g), 0.0192 g AuCI₃ (99%), and

0.0357 g MgCI₂-6H₂0 (99.995%) in 2.1 ml_ of deionized H₂0 and 0.1 ml_ concentrated

HCI, to form a metal salt mixture. This metal salt mixture was then added to 1 .1734 g of activated carbon. Excess liquid not absorbed by the activated carbon was dabbed away, and then the activated carbon was dried at 175 °C. The resulting dried metal loaded activated carbon had a final dry weight of 1 .9355 g. Based on the starting weight of the activated carbon and metal solution loading, the metal loading on the dried metal loaded activated carbon was calculated to be 22.3% Cu, 0.71 % Au, and 0.24% Mg. The dried metal loaded activated carbon (0.77 g) was charged into a quartz glass tube, and the charged tube was placed into a flow reactor. Activation and reduction of this supported copper catalyst was performed by flowing H₂ at 1 00 seem (controlled via Brook 5850E mass flow controller) into the glass tube containing the catalyst in the reactor at 600 °C for 5 hours. The heating was accomplished using a Lindberg/Blue Minimite 1 inch tube furnace.

[0030] The reaction apparatus (reactor) comprised a 4.8 mm inner diameter quartz glass tube in a flow reactor. The reactor tube was heated using a Lindberg/Blue Minimite 2.54 cm tube furnace. Brook 5850E mass flow controllers were used to control gas flow rates. A stainless steel SiCl4 bubbler was used to introduce S1CI4 into the H₂ gas stream. The amount of SiCl4 in the H₂ gas stream was adjusted by changing the temperature of the

SiCl4 in the bubbler according to calculations using well-known thermodynamic principles. For reactions run at pressures above atmospheric pressure, a back pressure regulator (GO type Hastelloy® rated for 0- 500 psig) was introduced at the back end of the reactor. The reactor effluent passed through an actuated 6-way valve from Vici.

[0031] The effluent of the reactor containing the reaction product comprising the trihalosilane comprising trichlorosilane was passed through an actuated 6-way valve (Vici) with constant 100 μΙ_ injection loop before being discarded. Samples were taken from the reaction effluent stream by actuating the injection valve and the 100 μΙ_ sample passed directly into the injection port of a 6890A Agilent GC for analysis with a split ratio at the injection port of 5:1 . The GC contained a single 30 m Rtx-DCA column (Restek, 320 urn inner diameter, 1 μιη thick film), which was split at the outlet. One path went to a TCD for quantization of the reaction products and the other path went to a Flame Ionization Detector.

[0032] Flow rate ratios were determined using known thermodynamic principles and the flow rates of hydrogen and S1CI4 at standard temperature and pressure.

COMPARATIVE EXAMPLE 1

[0033] A copper catalyst (0.6085 g) comprising an activated carbon supported mixture of 22.3% Cu, 0.71 % Au, and 0.24% Mg was prepared as described above. The copper catalyst was then treated with H2 and SiCl4 at a mole ratio of H2 to SiCl4 of 16:1 for 30 min by bubbling H2 (100 seem) through a stainless steel bubbler containing liquid SiCl4 at 0 °C and into a flow reactor containing the copper catalyst at 750 °C to form a silicon- containing copper catalyst comprising 4% Si. After 30 min, the S1CI4 flow was ceased, and the hydrogen flow was maintained for 1 h while cooling the reactor contents to 300 °C.

[0034] The reactor containing the silicon-containing copper catalyst was then purged with a 50 seem argon flow for 15 min. After the purging, HCI was fed through the reactor at a flow rate of 5 seem. The reaction effluent was periodically analyzed by GC to determine the HS1CI3 selectivity. After the silane production rate declined, the HCI feed was ceased, and the silicon-containing copper catalyst was contacted again with H2 and S1CI4 for 30 min at 750 °C to reform the silicon-containing copper catalyst. The reformed silicon- containing copper catalyst was then purged with argon and contacted again with HCI as described above.

[0035] This cycle of treating the copper catalyst with H2 and S1CI4 to form the silicon- containing copper catalyst (step (i)) and exposing the silicon-containing catalyst formed to HCI (step (ii)) was repeated six times. In some cycles, hydrogen or argon were co-fed with the HCI to the catalyst. Each cycle's conditions and the selectivity results are shown in Table 2. Comparative Example 1 shows that HS1CI3 can be produced with good selectivity, the benefits of adding hydrogen with the hydrogen halide, and that the silicon- containing copper catalyst can be regenerated repeatedly.

Table 2. Production of HS1CI3 at various temperatures and pressures with catalyst comprising Cu, Au, and Mg on activated carbon.

* - balance of material is methylated silicon-containing products.

COMPARATIVE EXAMPLE 2

[0060] A catalyst comprising 16.5% Cu, 0.7% Au, and 0.2% Mg on activated carbon was prepared and treated as described in Comparative Example 1 , except the stainless steel bubbler was at 23 °C to give a mole ratio of H2 to S1CI4 of 10:1 and the time was varied as indicated in Table 3, to form a silicon-containing copper catalyst comprising 4% Si. The silicon-containing copper catalyst was reacted in step 2 as in Comparative Example 1 but with the parameters listed in Table 3 and at 300 °C in every cycle. Comparative Example 2 shows that HSiCl3 can be produced with good selectivity, the benefits of adding hydrogen with the hydrogen halide, and that the silicon-containing copper catalyst can be regenerated repeatedly.

Table 3. Production of HSiCl3 at various temperatures and pressures with catalyst comprising Cu, Au, and Mg on activated carbon.

4 H₂: 100 HCI: 5 seem 14 ND 24.3 75.7 seem Ar: 10 seem 31 ND 15.4 84.6

Temp: 850 P: 14 kPag 55 ND ND 100.0

°C 79 ND ND 100.0

P: 34 kPag

SiCI4: 28.3

seem

5 H₂: 100 HCI: 5 seem 14 ND 35.4 64.6

seem H₂: 10 seem 31 ND 24.1 75.9

Temp: 850 P: 14 kPag 51 ND 22.1 77.9

°C

P: 28 kPag

SiCI4: 29.9

seem

6 H₂: 100 HCI: 5 seem 17 ND 22.9 77.1

seem Ar: 10 seem 36 ND 15.1 84.9

Temp: 850 P: 14 kPag 53 ND 13.0 87.0

°C 72 ND ND 100.0

P: 159 kPag 91 ND ND 100.0

SiCI4: 5.0

seem

7 H₂: 100 HCI: 2 seem 18 4.5 85.7 9.8

seem H₂: 20 seem 36 ND 17.8 82.2

Temp: 850 P: 345 kPag 53 ND 1 1 .9 88.1

°C

P: 28 kPag

Time: 60 min

SiCI4: 30.7

seem

8 H₂: 100 HCI: 2 seem 18 2.4 84.9 12.7

seem Ar: 20 seem 35 ND 23.6 76.4

Temp: 850 P: 345 kPag 53 ND 8.1 91 .9

°C 71 ND 7.2 92.9

P: 28 kPag

Time: 60 min

SiCI4: 29.6

seem

COMPARATIVE EXAMPLE 3

[0036] A catalyst comprising 16.3% (w/w) Cu, 0.7% (w/w) Au, and 0.2% (w/w) Mg on activated carbon was prepared and treated as described in Comparative Example 1 , except the stainless steel bubbler was at 22 °C to give a mole ratio of H2 to S1CI4 of 10:1 and the time was varied as indicated in Table 4, to form a silicon-containing copper catalyst comprising 4% Si. The silicon-containing copper catalyst was reacted in step 2 as in Comparative Example 1 but with the parameters listed in Table 4 and at 300 °C in every cycle. Table 4. Production of HS1CI3 at various temperatures and pressures with catalyst comprising Cu, Au, and Mg on activated carbon (16.3% (w/w) Cu, 0.7% (w/w) Au, 0.2%

(w/w) Mg on activated carbon).

COMPARATIVE EXAMPLE 4

[0037] A catalyst comprising 17.3% (w/w) Cu, 0.7% (w/w) Au, and 0.2% (w/w) Mg on activated carbon was prepared and treated as described in Comparative Example 1 , except the stainless steel bubbler was at 23 °C to give a mole ratio of H2 to S1CI4 of 10:1 and the time was varied as indicated in Table 5, to form a silicon-containing copper catalyst comprising 4% Si. The silicon-containing copper catalyst was reacted in step 2 as in Comparative Example 1 but with the parameters listed in Table 5 and at 300 °C in every cycle.

Table 5. Production of HS1CI3 at various temperatures and pressures with catalyst comprising Cu, Au, and Mg on activated carbon (17.3% Cu, 0.7% Au, and 0.2% Mg on C).

EXAMPLE 1 - Production of Trichlorosilane Using Activated Carbon Supported Copper Catalyst

[0038] A copper catalyst (0.5 grams) comprising an activated carbon supported mixture of copper, gold and magnesium, prepared by incipient wetness impregnation, was treated with H₂/SiCl4 for 30 min at 750 °C - 950 °C by bubbling H₂ through a stainless steel S1CI4 bubbler. The total flow of H2 and S1CI4 was varied from 1 10 seem to 150 seem and the mole ratio of H2 to S1CI4 was 5:1 to 1 1 :1 . The S1CI4 flow was controlled by H2 flow by varying the bubbler temperature from 1 1 °C to -3.6 °C. The gas and vapor leaving the bubbler was fed into the glass tube of a flow reactor containing the supported copper catalyst at 0 to 60 psig pressure for 30 min. The reaction was periodically sampled and analyzed by GC to determine the weight percent HS1CI3, based on the total mass leaving the reactor. The results are shown in Table 6. Example 1 demonstrated that

trichlorosilane was produced by the method described herein under the conditions in this example.

Table 6: Production of Trichlorosilane Using (22.3wt% Cu-0.71wt% Au-0.24wt% Mg)/C Catalyst at 750°C-950°C with H₂/SiCI₄ = 5-1 1

EXAMPLE 2 - Production of Trichlorosilane Using Activated Carbon Supported Copper Catalyst at low H2 to S1CI4 ratios

[0039] A copper catalyst (0.5 grams) comprising an activated carbon supported mixture of copper, gold and magnesium, prepared by incipient wetness impregnation, was treated with H₂/SiCl4 for 30 min at 750 °C to 950 °C by bubbling H₂ through a stainless steel S1CI4 bubbler. The total flow of H2 and S1CI4 was 150 seem and the mole ratio of H2 to S1CI4 was 1 to 4. The S1CI4 flow was controlled by H2 flow by varying the bubbler temperature from 14.6°C to 37.2 °C. The gas and vapor leaving the bubbler is fed into the glass tube of a flow reactor containing the supported copper catalyst at atmospheric pressure for 30 min. The reaction was periodically sampled and analyzed by GC to determine the weight percent HSiCl3, based on the total mass of the reaction product leaving the reactor. The results are shown in Table 7. Example 2 demonstrates that trichlorosilane was produced by the method described herein and tetrachlorosilane conversion to trichlorosilane was increased with increase in reaction temperature and decreases with decreasing H2 to

SiCl4 ratios. Table 7: Production of Trichlorosilane Using Activated Carbon Supported Copper Catalyst at low H2 to S1CI4 ratios

EXAMPLE 3 - Production of Trichlorosilane Using Activated Carbon Supported Copper Catalyst by Varying Copper Loading in the Catalyst

[0040] Hydrodechlorination of tetrachlorosilane was carried out using activated carbon supported copper catalysts by varying copper loading in the catalyst from 22% to 50% synthesized by incipient wet impregnation. An amount of 0.5 g of the supported copper catalyst was treated with H2/SiCl4 for 30 min at 950 °C by bubbling H2 through a stainless steel SiCl4 bubbler. The total flow of H2 and SiCl4 was 150 seem and the mole ratio of H2 to S1CI4 was 4. The S1CI4 flow was controlled by H2 flow by keeping the bubbler temperature at 14.6°C. The gas and vapor leaving the bubbler was fed into the glass tube of a flow reactor containing the supported copper catalyst at atmospheric pressure for 30 min. The reaction was periodically sampled and analyzed by GC to determine the weight percent HS1CI3, based on the total mass leaving the reactor. The results are shown in

Table 8.

Table 8: Production of Trichlorosilane Using Activated Carbon Supported Copper Catalyst by Varying Copper Loading in the Catalyst at 950 °C and H2/SiCl4 = 4

EXAMPLE 4 - Time on Stream Studies

[0041] An activated carbon supported copper catalyst was prepared as described above, and 0.5 grams of this catalyst ((22.3wt% Cu-0.71wt% Au-0.24wt% Mg)/C) was treated with H2/S1CI4 for 3h continuously at 950 °C by bubbling H2 through a stainless steel SiCl4 bubbler. The total flow of H2 and S1CI4 was 150 seem and the mole ratio of H2 to SiCl4 was 4. The SiCl4 flow was controlled by H2 flow by keeping the bubbler temperature at

14.6°C. The gas and vapor leaving the bubbler was fed into the glass tube of a flow reactor containing the supported copper catalyst at atmospheric pressure for 3h. The reaction was periodically sampled and analyzed by gas chromatography to determine the weight percent HSiCl3, based on the total mass leaving the reactor. The results showed that in less than an hour, yield of trichlorosilane was greater than 20%, and this yield was maintained for more than 3 h. Example 4 demonstrated that trichlorosilane was produced by the method, and the catalyst used in the conditions of this example was stable for more than 3 h without loss of activity.

EXAMPLE 5 - Production of Trichlorosilane Using Alumina Supported Copper Catalyst (30wt%Cu/AI₂O₃)

[0042] Hydrodechlorination of tetrachlorosilane was carried out using alumina supported copper catalysts by using different particle size of alumina synthesized by incipient wet impregnation. An amount of 0.5 grams of catalyst was treated with H2/S1CI4 for 30 min at 750 °C by bubbling H2 through a stainless steel SiCl4 bubbler. The total flow of H2 and

SiCl4 was 150 seem, and the mole ratio of H2 to SiCl4 was varied from 1 to 4. The S1CI4 flow was controlled by H2 flow by varying the bubbler temperature from 14.6°C to 37.2 °C.

The gas and vapor leaving the bubbler was fed into the glass tube of a flow reactor containing the copper catalyst at atmospheric pressure for 30 min. The reaction was periodically sampled and analyzed by GC to determine the weight percent HSiCl3, based on the total mass leaving the reactor. The results are shown in Table 9. Example 5 demonstrated that trichlorosilane was produced by the method with the conditions in this example. Table 9: Production of Trichlorosilane Using Alumina Supported Copper Catalyst

(30wt%Cu/AI₂O₃)

EXAMPLE 6 - Production of Trichlorosilane Using Silica gel Supported Copper Catalyst (30wt%Cu/SiO₂)

[0043] Hydrodechlorination of tetrachlorosilane was carried out using silica gel supported copper catalysts by synthesized by incipient wet impregnation. An amount of 0.75 g of catalyst was treated with H2/S1CI4 for 30 min at temperatures ranging from 500 °C to 750 °C by bubbling H₂ through a stainless steel S1CI4 bubbler. The total flow of H₂ and S1CI4 was 150 seem and the mole ratio of H₂ to S1CI4 was maintained at 1 . The S1CI4 flow was controlled by H₂ flow by keeping the bubbler temperature at 37.2 °C. The gas and vapor leaving the bubbler was fed into the glass tube of a flow reactor containing the supported copper catalyst at atmospheric pressure for 30 min. The reaction was periodically sampled and analyzed by GC to determine the weight percent HS1CI3, based on the total mass of reaction product leaving the reactor. The results are shown in Table 10. Example 6 demonstrated that trichlorosilane production increased with an increase in reaction temperature under the conditions in this example.

Table 10: Production of Trichlorosilane Using Silica gel Supported Copper Catalyst (30wt%Cu/SiO₂)

EXAMPLE 7 - Production of Trichlorosilane Using Silica 65wt% CuO/Silica (spray dried catalyst)

[0044] A spray dried 65wt% CuO/SiC>2 catalyst obtained from Sud Chemie was tested for the hydrodechlorination of tetrachlorosilane to trichlorosilane. An amount of 1 gram of this catalyst was reduced under H2 at 500 °C with 100 seem for 3h to 4h then treated with

H2/S1CI4 for 30 min at 750 °C to 950 °C by bubbling H2 through a stainless steel S1CI4 bubbler. The total flow of H2 and SiCl4 was 150 seem, and the mole ratio of H2 to SiCl4 was varied from 1 to 4. The S1CI4 flow was controlled by H2 flow by varying the bubbler temperature from 14.6°C to 37.2 °C. The gas and vapor leaving the bubbler was fed into the glass tube of a flow reactor containing the copper catalyst at atmospheric pressure for 30 min. The reactor effluent was periodically sampled and analyzed by GC to determine the weight percent HS1CI3, based on the total mass leaving the reactor. The results are shown in Table 1 1 .

Table 1 1 : Production of Trichlorosilane Using Silica 65wt% CuO/Silica (spray dried catalyst)

COMPARATIVE EXAMPLE 5 - Production of Trichlorosilane Using Unsupported Copper Catalyst

[0045] An unsupported copper catalyst (4.15 grams) was treated with H2/SiCl4 for 30 min at 750 °C by bubbling H2 through a stainless steel SiCl4 bubbler. The total flow of H2 and SiCl4 was 150 seem and the mole ratio of H2 to SiCl4 was 4:1 . The S1CI4 flow was controlled by H2 flow by keeping the bubbler temperature at 14.6°C. The gas and vapor leaving the bubbler was fed into the glass tube of a flow reactor containing the unsupported copper catalyst at atmospheric pressure for 30 min. The reaction was periodically sampled and analyzed by GC to determine the weight percent HSiCl3, based on the total mass leaving the reactor. Use of unsupported copper was shown to build pressure within the system, not allowing for adequate H2/SiCl4 flow, therefore GC results were not accurate.

Comparative Example 5 demonstrated that unsupported copper catalyst built up pressure within the reactor, and upon removal, was shown to be sintered together. The results are shown in Table 12.

Table 12: Production of Trichlorosilane Using Unsupported Copper Catalyst at 750 °C with H₂/SiCI₄ = 4

[0046] Without wishing to be bound by theory, it is thought that the method described herein may provide one or more benefits over previously disclosed processes for making trihalosilanes. In the method herein, a lower amount of H2 relative to S1X4 may be used with good yield as compared to previous processes.

[0047] The method described herein may also be simpler and allow for a longer run time without drop in selectivity necessitating the need to regenerate the catalyst, as shown in Example 4. Furthermore, for example, in Example 1 and Comparative Example 1 , it can be seen that a yield of trichlorosilane may be maintained for a longer period of time using the method described herein as compared to a previous method.

[0048] Furthermore, the method described herein may be suitable for making HS1CI3 for semiconductor grade polycrystalline silicon production, particularly when a carbon free supported copper catalyst (such as a silica or alumina supported copper catalyst) is used, thereby minimizing potential for carbon contamination of trihalosilane in the reaction product because carbon contamination is undesirable in the raw materials used for polycrystalline silicon production, particularly semiconductor grade polycrystalline silicon.

[0049] All ratios, percentages, and other amounts described herein are by weight, unless otherwise indicated by the context of the specification. With respect to any Markush groups relied upon herein for describing particular features or aspects of various embodiments, it is to be appreciated that different, special, and/or unexpected results may be obtained from each member of the respective Markush group independent from all other Markush members. Each member of a Markush group may be relied upon individually and or in combination and provides adequate support for specific embodiments within the scope of the appended claims.

[0050] It is also to be understood that any ranges and subranges relied upon in describing various embodiments of the present disclosure independently and collectively fall within the scope of the appended claims, and are understood to describe and contemplate all ranges including whole and/or fractional values therein, even if such values are not expressly written herein. The enumerated ranges and subranges sufficiently describe and enable various embodiments of the present disclosure, and such ranges and subranges may be further delineated into relevant halves, thirds, quarters, fifths, and so on. As just one example, a range "of 300 to 950" may be further delineated into a lower third, i.e., from 300 to 516, a middle third, i.e., from 517 to 733, and an upper third, i.e., from 734 to 950, which individually and collectively are within the scope of the appended claims, and may be relied upon individually and/or collectively and provide adequate support for specific embodiments within the scope of the appended claims. In addition, with respect to the language which defines or modifies a range, such as "at least," "greater than," "less than," "no more than," and the like, it is to be understood that such language includes subranges and/or an upper or lower limit. As another example, a range of "at least 0.1 %" inherently includes a subrange from 0.1 % to 65%, a subrange from 10% to 25%, a subrange from 23% to 50%, and so on, and each subrange may be relied upon individually and/or collectively and provides adequate support for specific embodiments within the scope of the appended claims. Finally, an individual number within a disclosed range may be relied upon and provides adequate support for specific embodiments within the scope of the appended claims. For example, a range of "4:1 to 1 :1 " includes various individual members, such as 3:1 , as well as individual numbers including a decimal point (or fraction), such as 2.1 :1 , which may be relied upon and provide adequate support for specific embodiments within the scope of the appended claims.

[0051] The subject matter of all combinations of independent and dependent claims, both singly and multiply dependent, is expressly contemplated but is not described in detail for the sake of brevity. The disclosure has been described in an illustrative manner, and it is to be understood that the terminology which has been used is intended to be in the nature of words of description rather than of limitation. Many modifications and variations of the present disclosure are possible in light of the above teachings, and the disclosure may be practiced otherwise than as specifically described.

Claims

CLAIMS:

1 . A method of forming a reaction product in a reactor comprises:

(i) heating the reactor to a temperature of at least 300 °C,

a support, and

a metal selected from copper and a combination comprising copper and at least one element selected from gold and magnesium,

thereby forming the reaction product comprising the trihalosilane; with the proviso that the method is performed without a separate step of adding a hydrogen halide from outside the reactor after contacting the supported copper catalyst with the silicon tetrahalide in order for the method to form the trihalosilane.

2. The method of claim 1 , where the supported copper catalyst comprises 0.1 wt% to 65 wt% copper with the balance of the supported copper catalyst being the support.

3. The method of claim 1 , where the supported copper catalyst comprises 0.1 wt% to 55 wt% of the combination, and the combination comprises copper, gold, and magnesium , with the balance of the supported copper catalyst being the support.

4. The method of any one of claims 1 to 3, where the supported copper catalyst is free of carbon.

5. The method of any one of the preceding claims, where a mole ratio of H2 to silicon tetrahalide is 1 1 :1 to 1 :1 .

6. The method of any one of the preceding claims, where the temperature is 500 °C to 950 °C.

7. The method of any one of the preceding claims, where step (ii) of the method is performed at a pressure of 0 kPag to 415 kPag.

8. The method of any one of the preceding claims, where the method produces the trihalosilane for at least 30 min.

9. The method of claim 8, where the method produces the trihalosilane for at least 3 h.

10. The method of any one of the preceding claims, further comprising one or more steps, where:

additional step (p1 ) is purging the supported copper catalyst before step (ii), and/or additional (iii) is recovering the trihalosilane.

11 . The method of any one of the preceding claims, where the trihalosilane has the formula HS1X3, where X is F, CI, Br, or I.

12. The method of any one of the preceding claims, where the hydrogen halide is HCI, the silicon tetrahalide is S1CI4, and the trihalosilane is HSiCl3.

13. The method of any one of the preceding claims, further comprising using the trihalosilane as a reactant to make high purity polycrystalline silicon.

14. The method of any one of the preceding claims, further comprising using the trihalosilane as a reactant to make polysiloxane resins.

15. The method of any one of the preceding claims, further comprising using the trihalosilane as a reactant to make organosilanes.