WO2014149224A1

WO2014149224A1 - Method for preparing a halosilane using copper silicides as catalysts

Info

Publication number: WO2014149224A1
Application number: PCT/US2014/015468
Authority: WO
Inventors: Aaron COPPERNOLL; Aswini DASH; Matthew GAVE; Catharine HORNER; Krishna Janmanchi; Dimitris Katsoulis; Vladimir PUSHKAREV
Original assignee: Dow Corning Corporation
Priority date: 2013-03-15
Filing date: 2014-02-10
Publication date: 2014-09-25

Abstract

A method for preparing a reaction product includes: optional step (1 ) contacting, at a temperature from 200 ¾ to 1400 °C, an ingredient including a silane of formula H_aR_bSiX_(4- _a-k), where subscript a is 0 to 4, subscript b is 0 or 1, a quantity (a + b) < 4, each R is independently a monovalent organic group, and each X is independently a halogen atom, with the proviso that when the quantity (a + b) < 4, then the ingredient further includes H₂; with a copper silicide; thereby forming a reactant; and step (2) contacting the reactant with an organohalide at a temperature from 100 °C to 600 °C; thereby forming the reaction product and a spent reactant. The reaction product is distinct from the silane used in step (1 ), and the reaction product includes a halosilane of formula R₂SiX₂, where each R is independently a monovalent organic group, and each X is independently a halogen atom. Step (1 ) of the method may be optional. When step (1 ) is present, steps (1 ) and (2) are performed separately and consecutively.

Description

METHOD FOR PREPARING A HALOSILANE USING COPPER SILICIDES AS

CATALYSTS

[0001] Various halosilanes find use in different industries. Diorganodihalosilanes, such as dimethyldichlorosilane, are hydrolyzed to produce a wide range of polyorganosiloxanes, such as polydiorganosiloxanes.

[0002] Methods of preparing halosilanes are known in the art. Typically, halosilanes are produced commercially by the Mueller-Rochow Direct Process, which comprises passing a halide compound over zero-valent silicon (Si⁰) in the presence of a copper catalyst and various optional promoters. Mixtures of halosilanes are produced by the Direct Process. When an organohalide is used, a mixture of organohalosilanes is produced by the Direct Process.

[0003] The typical process for making the Si⁰ used in the Direct Process consists of the carbothermic reduction of S1O2 in an electric arc furnace. Extremely high temperatures are required to reduce the S1O2, so the process is energy intensive. Consequently, production of Si⁰ adds costs to the Direct Process for producing halosilanes. Therefore, there is a need for a more economical method of producing halosilanes that avoids or reduces the need of using Si⁰.

[0004] In addition to the Direct Process, diorganodihalosilanes have been produced by the alkylation of silicon tetrachloride and various methylchlorosilanes by passing the vapors of these chlorosilanes together with an alkyl halide over finely divided aluminum or zinc at elevated temperatures. However, this process results in the production of a large amount of aluminum chloride or zinc chloride, which is costly to dispose of on a commercial scale.

[0005] Therefore, there is a need for a more economical method of producing halosilanes that avoids the need for Si⁰ produced by reducing S1O2 at extremely high temperatures and that does not require the costly disposal of byproducts.

BRIEF SUMMARY OF THE INVENTION

[0006] A method for preparing a reaction product comprising a halosilane comprises: optional step (1 ) contacting, at a temperature from 200 °C to 1400°C, an ingredient comprising a silane of formula H_aR|₃SiX(4_-a-|_:)), where subscript a is 0 to 4, subscript b is 0 or 1 , a quantity (a + b) < 4, each R is independently a monovalent organic group, and each X is independently a halogen atom, with the proviso that when the quantity (a + b) is < 4, then the ingredient further comprises H2; with a copper silicide; thereby forming a reactant; and step (2) contacting the reactant with an organohalide at a temperature from 100°C to 600 °C; thereby forming the reaction product and a spent reactant. When step (1 ) is present, steps (1 ) and (2) are performed separately and consecutively.

DETAILED DESCRIPTION OF THE INVENTION

[0007] The Brief Summary of the Invention and the Abstract are hereby incorporated by reference. All ratios, percentages, and other amounts are by weight, unless otherwise indicated. The articles 'a', 'an', and 'the' each refer to one or more, unless otherwise indicated by the context of the specification. Abbreviations used herein are defined in Table A, below.

Table A - Abbreviations

[0008] "AlkyI" means an acyclic, branched or unbranched, saturated monovalent hydrocarbon group. Examples of alkyl groups include Me, Et, Pr, 1 -methylethyl, Bu, 1 - methylpropyl, 2-methylpropyl, 1 ,1 -dimethylethyl, 1 -methylbutyl, 1 -ethylpropyl, pentyl, 2- methylbutyl, 3-methylbutyl, 1 ,2-dimethylpropyl, 2,2-dimethylpropyl, hexyl, heptyl, 2- ethylhexyl, octyl, nonyl, and decyl; and as well as other branched saturated monovalent hydrocarbon groups with 6 or more carbon atoms. Alkyl groups have at least one carbon atom. Alternatively, alkyl groups may have 1 to 12 carbon atoms, alternatively 1 to 10 carbon atoms, alternatively 1 to 6 carbon atoms, alternatively 1 to 4 carbon atoms, alternatively 1 to 2 carbon atoms, and alternatively 1 carbon atom.

[0009] "AralkyI" and "alkaryl" each refer to an alkyl group having a pendant and/or terminal aryl group or an aryl group having a pendant alkyl group. Exemplary aralkyl groups include benzyl, tolyl, xylyl, phenylethyl, phenyl propyl, and phenyl butyl. Aralkyl groups have at least 6 carbon atoms. Monocyclic aralkyi groups may have 6 to 12 carbon atoms, alternatively 6 to 9 carbon atoms, and alternatively 6 to 7 carbon atoms. Polycyclic aralkyi groups may have 7 to 17 carbon atoms, alternatively 7 to 14 carbon atoms, and alternatively 9 to 10 carbon atoms.

[0010] "Alkenyl" means an acyclic, branched, or unbranched unsaturated monovalent hydrocarbon group, where the monovalent hydrocarbon group has a double bond. Alkenyl groups include Vi, allyl, propenyl, and hexenyl. Alkenyl groups have at least 2 carbon atoms. Alternatively, alkenyl groups may have 2 to 12 carbon atoms, alternatively 2 to 10 carbon atoms, alternatively 2 to 6 carbon atoms, alternatively 2 to 4 carbon atoms, and alternatively 2 carbon atoms.

[0011] "Alkynyl" means an acyclic, branched, or unbranched unsaturated monovalent hydrocarbon group, where the monovalent hydrocarbon group has a triple bond. Alkynyl groups include ethynyl and propynyl. Alkynyl groups have at least 2 carbon atoms.

Alternatively, alkynyl groups may have 2 to 12 carbon atoms, alternatively 2 to 10 carbon atoms, alternatively 2 to 6 carbon atoms, alternatively 2 to 4 carbon atoms, and alternatively 2 carbon atoms.

[0012] "Aryl" means a cyclic, fully unsaturated, hydrocarbon group. Aryl is exemplified by, but not limited to, Ph and naphthyl. Aryl groups have at least 5 carbon atoms.

Monocyclic aryl groups may have 5 to 9 carbon atoms, alternatively 6 to 7 carbon atoms, and alternatively 6 carbon atoms. Polycyclic aryl groups may have 10 to 17 carbon atoms, alternatively 10 to 14 carbon atoms, and alternatively 12 to 14 carbon atoms.

[0013] "Carbocycle" and "carbocyclic" refer to a hydrocarbon ring. Carbocycles may be monocyclic or alternatively may be fused, bridged, or spiro polycyclic rings. Carbocycles have at least 3 carbon atoms. Monocyclic carbocycles may have 3 to 9 carbon atoms, alternatively 4 to 7 carbon atoms, and alternatively 5 to 6 carbon atoms. Polycyclic carbocycles may have 7 to 17 carbon atoms, alternatively 7 to 14 carbon atoms, and alternatively 9 to 10 carbon atoms. Carbocycles may be saturated or partially unsaturated.

[0014] "Cycloalkyl" refers to a saturated hydrocarbon group including a carbocycle. Cycloalkyl groups are exemplified by cyclobutyl, cyclopentyl, cyclohexyl, and

methylcyclohexyl. Cycloalkyl groups have at least 3 carbon atoms. Monocyclic cycloalkyl groups may have 3 to 9 carbon atoms, alternatively 4 to 7 carbon atoms, and alternatively 5 to 6 carbon atoms. Polycyclic cycloalkyl groups may have 7 to 17 carbon atoms, alternatively 7 to 14 carbon atoms, and alternatively 9 to 10 carbon atoms.

[0015] "Copper silicide" means a material including both silicon and copper that are intermixed at an atomic level, and the arrangement of the atoms can be described using well known crystallographic principles and models. Example phases of copper silicides are found in the phase diagram (Okamoto H., J. Phase. Equilib., Vol. 23, 2002, p 281 -282) and include, but are not limited to: Cu₀.88^Si0.12> ^Cu0.85^Si0.15> ^Cu0.83^Si0.17> ^Cu4.15^Si0.85> Cui 5Si4,and CU317S1. In addition, copper silicide may further include Cu and Si individually, provided that the amount of Cu present is not sufficient to cause sintering in the method described herein. Exemplary copper silicides include, but are not limited to, CU7S1, CU5S1, CU4S1, and CU3S1. Other exemplary copper silicides include, but are not limited to, K-CU7S1, Y-CU5S1, 5-Cu4 88Si, e-Cu4Si, and n.-Cu3Si. Other exemplary copper silicides include, but are not limited to n.-Cu3Si, n.'-Cu3Si, n."-Cu3Si, n.-Cu317S1, η'-

Cu3i 7Si, and n."-Cu317S1.

[0016] "Metallic" means that the metal has an oxidation number of zero.

[0017] "Purging" means to introduce a gas stream into a container to remove unwanted materials.

[0018] "Treating" means to introduce a gas stream into a container to pre-treat a component before contacting the component with another component. Treating includes contacting the reactant to reduce or otherwise activate it before contacting it with the organohalide in step (2) of the method. Treating may further include contacting the copper silicide to reduce or otherwise activate it before contacting it with the ingredients comprising the H2 and the silane in step (1 ) of the method.

[0019] "Residence time" means the time which a component takes to pass through a reactor system in a continuous process, or the time a component spends in the reactor in a batch process. For example, residence time in step (1 ) refers to the time during which one reactor volume of the copper silicide makes contact with the ingredient comprising the silane as the copper silicide passes through the reactor system in a continuous process or during which the copper silicide is placed within the reactor in a batch process.

Alternatively, residence time may refer to the time for one reactor volume of reactive gases to pass through a reactor charged with the copper silicide in step (1 ). (E.g., residence time includes the time for one reactor volume of and the ingredient comprising the silane in step (1 ) to pass through a reactor charged with the copper silicide or the time for one reactor volume of organohalide to pass through a reactor charged with the reactant in step (2) of the method described herein.)

[0020] "Reactant" means a solid product that is formed in step (1 ) of the method described herein, and/or re-formed in step (3) of the method described herein.

[0021 ] "Spent reactant" refers to the reactant after it has been contacted with the organohalide. For example, spent reactant may be present after step (2) (or after step (4), when step (4) is present in the method). The spent reactant after step (2) (or step (4)) contains an amount of silicon that is less than the amount of silicon in the reactant before beginning step (2) (or after step (3) and before beginning step (4)). Spent reactant may, or may not, be exhausted, i.e., spent reactant may contain some silicon that may or may not be reactive with the organohalide.

[0022] In one embodiment, the method for preparing the reaction product comprising the halosilane comprises separate and consecutive steps (1 ) and (2), where:

step (1 ) is contacting, at a temperature from 200 °C to 1400°C, an ingredient comprising a silane of formula H_aRbSiX(4__a_b), where subscript a is 0 to 4, subscript b is 0 or 1 , a quantity (a + b) < 4, each R is independently a monovalent organic group, and each X is independently a halogen atom, with the proviso that when the quantity (a + b) < 4, then the ingredients further comprise H2; with a copper silicide; thereby forming a reactant; and step (2) is contacting the reactant with an organohalide at a temperature from 100 °C to 600 °C; thereby forming the reaction product and a spent reactant; and

where the method optionally further comprises steps (3) and (4), where when steps (3) and (4) are present, steps (3) and (4) are performed separately and consecutively after step (2), and where

step (3) is contacting, at a temperature from 200 °C to 1400°C, the spent reactant with an additional ingredient comprising an additional silane of formula H_aR|₃SiX(4_-a-|₃), where subscript a is 0 to 4, subscript b is 0 or 1 , the quantity (a + b) < 4, each R is independently a monovalent organic group, and each X is independently a halogen atom, with the proviso that when the quantity (a + b) < 4, then the additional ingredient further comprises H2; thereby re-forming the reactant, and

step (4) is contacting the reactant re-formed in step (3) with additional organohalide at a temperature from 100°C to 600 °C; and

where the method optionally further comprises step (5), where step (5) is repeating steps (3) and (4) at least one time; and

where the method optionally further comprises step (6), where step (6) is recovering the halosilane.

[0023] In an alternative embodiment, the method for preparing a reaction product comprising a halosilane comprises:

optional step (1 ) contacting, at a temperature from 200 °C to 1400°C, an ingredient comprising a silane of formula H_aRbSiX(4__a_b), where subscript a is 0 to 4, subscript b is 0 or 1 , a quantity (a + b) < 4, each R is independently a monovalent organic group, and each X is independently a halogen atom, with the proviso that when the quantity (a + b) < 4, then the ingredient further comprises H2; with a copper silicide; thereby forming a reactant; and step (2) contacting the reactant with an organohalide at a temperature from 100 °C to 600 °C; thereby forming the reaction product and a spent reactant;

with the proviso that when step (1 ) is present, steps (1 ) and (2) are performed separately and consecutively; and

where the method optionally further comprises steps (3) and (4), where when steps

(3) and (4) are present, steps (3) and (4) are performed separately and consecutively after step (2), and where

step (3) is contacting, at a temperature from 200 °C to 1400 °C, the spent reactant with an additional ingredient comprising an additional silane of formula H_aRbSiX(4__a_b), where subscript a is 0 to 4, subscript b is 0 or 1 , the quantity (a + b) < 4, each R is independently a monovalent organic group, and each X is independently a halogen atom, with the proviso that when the quantity (a + b) < 4, then the additional ingredient further comprises H2; thereby re-forming the reactant, and

step (4) is contacting the reactant re-formed in step (3) with additional organohalide at a temperature from 100 °C to 600 °C; and

[0024] When step (1 ) is present, steps (1 ) and (2) are performed separately and consecutively. "Separate" and "separately" mean that step (1 ) and step (2) do not overlap or coincide. "Consecutive" and "consecutively" mean that step (2) is performed after step (1 ) in the method; however, additional steps may be performed between step (1 ) and (2), as described below. "Separate" and "separately" refer to either spatially or temporally or both. "Consecutive" and "consecutively" refers to temporally (and furthermore occurring in a defined order).

[0025] The silane used in step (1 ) has formula H_aR|₃SiX(4_-a-|₃), where subscript a is 0 to

4, subscript b is 0 to 2, and a quantity (a + b) < 4. Alternatively, subscript a may be 0 or 1 , subscript b may be 0 or 1 , and 0 < (a + b) < 1 . Each R is independently a monovalent organic group, and each X is independently a halogen atom. Alternatively, in the formula ^Ha^RbSiX(4-a-b) _> ^{eacn x ma}y ^De independently selected from Br, CI, and I; alternatively Br and CI; alternatively CI and I ; and alternatively each X may be CI. Each R may be a hydrocarbyl group. Each R may be independently selected from alkyl, alkenyl, alkynyl, aryl, aralkyi, and carbocyclic as defined above. Alternatively, each R may be a hydrocarbyl group independently selected from alkyl, aryl, and carbocyclic. Alternatively, each R may be alkyl, such as Me, Et, Pr, or Bu; alternatively Me. The silane may comprise a tetrahalosilane (S1X4), a trihalosilane (HS1X3), a dihalosilane (H2S1X2), a monohalosilane

(H3S1X), silane (S1H4), or a combination thereof. Alternatively, the silane may comprise a tetrahalosilane, a trihalosilane, or a combination thereof. Alternatively, the silane may be a tetrahalosilane of formula S1X4, (i.e., where a = 0 and b = 0 in the formula above) where each X is as described above. Examples of the tetrahalosilane include, but are not limited to, silicon tetrachloride, silicon tetrabromide, silicon tetraiodide, and silicon tetrafluoride. Alternatively, the silane may be a trihalosilane such as HS1X3, (where a = 1 and b = 0 in the formula H_aR|₃SiX(4_-a-|_:))) and/or RS1X3, (where a = 0 and b = 1 in the formula

H_aR|3SiX(4__a_b)), where R and X are as described above. Examples of trihalosilanes include trichlorosilane (HSiCl3), tribromosilane, methyltrichlorosilane (CH3SiCl3), methyltribromosilane, ethyltrichlorosilane, ethyltribromosilane, and a combination thereof. Alternatively, when the silane used comprises SiH4, then in step (1 ), H2 may be omitted; when the quantity (a + b) < 4, then in step (1 ) the ingredients further comprise H2. The silane used in step (1 ) is distinct from the halosilane in the reaction product.

[0026] The copper silicide used in step (1 ) is a pre-formed copper silicide. The copper silicide is as defined above. The copper silicide may be, for example, one or more of CU7S1, CU5S1, CU4S1, and CU3S1. Alternatively, the copper silicide may be one or more of

K-CU7S1, Y-CU5S1, £-Cu4Si, and n.-Cu3Si. Alternatively, the copper silicide may be CU3S1, CU5S1, or a combination thereof. Alternatively, the copper silicide may be CU3S1.

Alternatively, the copper silicide may be CU5S1. Copper silicides are commercially available.

[0027] The reactor in which step (1 ) is performed may be any reactor suitable for the combining of gases and solids. For example, the reactor configuration can be a batch vessel, packed bed, stirred bed, vibrating bed, moving bed, re-circulating beds, or a fluidized bed. When using re-circulating beds, the copper silicide can be circulated from a bed for conducting step (1 ) to a bed for conducting step (2). To facilitate reaction, the reactor should have means to control the temperature of the reaction zone, e.g., the portion of the reactor in which the H2 and the silane contact the copper silicide in step (1 ) and/or the portion of the reactor in which the organohalide contacts the reactant in step (2).

[0028] The temperature at which the ingredient comprising the silane is contacted with the copper silicide in step (1 ) may be from 200°C to 1400 °C; alternatively 500 °C to 1400 °C; alternatively 600 °C to 1200 °C; and alternatively 650 °C to 1 100 °C. [0029] The pressure at which the ingredient comprising the silane is contacted with the copper silicide in step (1 ) can be sub-atmospheric, atmospheric, or super-atmospheric. For example, the pressure may range from 10 kilopascals absolute (kPa) to 2100 kPa;

alternatively 101 kPa to 2101 kPa; alternatively 101 kPa to 1 101 kPa; and alternatively 101 kPa to 900 kPa; and alternatively 201 kPa to 901 kPa..

[0030] The mole ratio of H2 to silane contacted with the copper silicide in step (1 ) may range from 10,000:1 to 0.01 :1 , alternatively 100:1 to 1 :1 , alternatively 20:1 to 5:1 , alternatively 20:1 to 4:1 , alternatively 20:1 to 2:1 , alternatively 20:1 to 1 :1 , and alternatively 4:1 to 1 :1 .

[0031] The residence time for the ingredient comprising the silane is sufficient for the ingredient comprising the silane to contact the copper silicide and form the reactant in step (1 ). For example, a sufficient residence time for the ingredient comprising the silane may be at least 0.01 s, alternatively at least 0.1 s, alternatively 0.1 s to 10 min, alternatively 0.1 s to 1 min, alternatively 0.5 s to 10 s, alternatively 1 min to 3 min, and alternatively 5 s to 10 s. Alternatively, the residence time for the copper silicide to be in contact with the ingredient comprising the silane in step (1 ) is typically at least 0.1 min; alternatively at least 0.5 minutes; alternatively 0.1 min to 120 min; alternatively 0.5 min to 9 min; alternatively 0.5 min to 6 min. The desired residence time may be achieved by adjusting the flow rate of the H2 and the silane, or by adjusting the total reactor volume, or by any combination thereof. The desired residence time of the reactant may be achieved by adjusting the flow rate of the reactant, or by adjusting the total reactor volume, or a combination thereof.

[0032] In step (1 ), when H2 is present, the H2 and the silane may be fed to the reactor simultaneously; however, other methods of combining, such as by separate pulses, are also envisioned. The H2 and the silane may be mixed together before feeding to the reactor; alternatively, the H2 and the silane may be fed into the reactor as separate streams.

[0033] In step (1 ), the copper silicide is in a sufficient amount. A sufficient amount of copper silicide is enough copper silicide to form the reactant, described below, when the ingredient comprising the silane is contacted with the copper silicide. For example, a sufficient amount of copper silicide may be at least 0.01 mg copper silicide/cm³ of reactor volume; alternatively at least 0.5 mg copper silicide/cm³ of reactor volume, and

alternatively 1 mg copper silicide/cm³ of reactor volume to maximum bulk density of the copper silicide based on the reactor volume, alternatively 1 mg to 5,000 mg copper silicide/cm³ of reactor volume, alternatively 1 mg to 1 ,000 mg copper silicide/cm³ of reactor volume, and alternatively 1 mg to 900 mg copper silicide/cm³ of reactor volume.

[0034] There is no upper limit on the time for which step (1 ) is conducted. For example, step (1 ) is usually conducted for at least 0.1 s, alternatively from 1 s to 5 hr, alternatively from 1 min to 1 hr.

[0035] The product of step (1 ) is the reactant. The reactant comprises an amount of silicon of at least 0.1 %, alternatively 0.1 % to 90%, alternatively 1 % to 50%, alternatively 1 % to 35%, based on the total weight of reactant. The percentage of silicon in the reactant can be determined using standard analytical tests. For example, the percentage of Si may be determined using ICP-AES and ICP-MS.

[0036] Step (2) of the method is contacting the reactant with the organohalide at a temperature from l OO i to 600 °C; thereby forming the reaction product and the spent reactant. The organohalide may have formula RX, where R is a monovalent organic group and X is a halogen atom. The halogen atom selected for X in the organohalide may be the same as the halogen atom selected for X in the silane used in step (1 ). Alternatively, the halogen atom selected for X in the organohalide may differ from the halogen atom selected for X in the silane used in step (1 ). The group selected for R in the organohalide may be the same as the group selected for R for the silane described above in step (1 ) (when subscript b > 0 in the formula H_aR|₃SiX(4__a_b))- Alternatively, the group selected for R in the organohalide may differ from the group selected for R in the silane described above for step (1 ). Alternatively, R may be selected from alkyl, alkenyl, alkynyl, aryl, aralkyl, and carbocyclic as defined above. Alternatively, R may be a hydrocarbyl group selected from alkyl, aryl, and carbocyclic. Alternatively, each R may be alkyl, such as Me, Et, Pr, or Bu; alternatively Me. Alkyl groups containing at least three carbon atoms can have a branched or unbranched structure. Alternatively, each X may be independently selected from Br, CI, and I; alternatively Br and CI; alternatively CI and I; and alternatively each X may be CI. Examples of the organohalide include, but are not limited to, methyl chloride, methyl bromide, methyl iodide, ethyl chloride, ethyl bromide, ethyl iodide, cyclobutyl chloride, cyclobutyl bromide, cyclohexyl chloride, and cyclohexyl bromide.

[0037] The reactors suitable for use in step (2) are as described for step (1 ). The same reactor may be used for step (1 ) as used in step (2). Alternatively, separate reactors may be used for steps (1 ) and (2). When separate reactors are used, the type of reactor in each step may be the same or different. In step (2), the organohalide may be contacted with the reactant by feeding the organohalide into a reactor containing the reactant produced in step (1 ). [0038] The residence time of the organohalide is sufficient for the organohalide to react with the reactant to form the reaction product comprising the halosilane in step (2). For example, a sufficient residence time of the organohalide may be at least 0.01 s, alternatively at least 0.1 s, alternatively 0.5 s to 10 min, alternatively 1 s to 1 min, alternatively 1 s to 10 s. The desired residence time can be achieved by adjusting the flow rate of the organohalide, or the total reactor volume, or a combination thereof.

[0039] The residence time for the reactant to be in contact with the organohalide in step

(2) is typically at least 1 minute; alternatively at least 5 minutes; alternatively 1 min to 120 min; alternatively 5 min to 90 min; alternatively 5 min to 60 min. Alternatively, there is no upper limit on the residence time for which step (2) is conducted. The desired residence time of the reactant in step (2) may be achieved by adjusting the flow rate of the reactant, or by adjusting the total reactor volume, or a combination thereof.

[0040] The temperature at which organohalide is contacted with the reactant in step (2) may be from 100°C to 600 °C, alternatively 200 °C to 500 °C, and alternatively 250 °C to 375 °C.

[0041] Step (2) is typically conducted until the amount of silicon in the reactant falls below a predetermined limit, e.g., until the reactant is spent. For example, step (2) may be conducted until the amount of silicon in the reactant is below 90%, alternatively 1 % to 90%, alternatively 1 % to 40%, of its initial weight percent. The initial weight percent of silicon in the reactant is the weight percent of silicon in the reactant before the reactant is contacted with the organohalide in step (2) (or the weight percent of silicon in the reactant after step

(3) and before step (4), when these steps are present). The amount of silicon in the reactant can be monitored by correlating production of the reaction product of step (2) with the weight percent of silicon in the reactant and then monitoring the reactor effluent or may be determined as described above.

[0042] The pressure at which the organohalide is contacted with the reactant in step (2) can be sub-atmospheric, atmospheric, or super-atmospheric. For example, the pressure may range from 10 kilopascals absolute (kPa) to 2100 kPa; alternatively 101 kPa to 2101 kPa; alternatively 101 kPa to 1 101 kPa; and alternatively 101 kPa to 900 kPa; and alternatively 201 kPa to 901 kPa..

[0043] The reactant is present in a sufficient amount. A sufficient amount of reactant is enough reactant to form the halosilane, described herein, when the reactant is contacted with the organohalide. For example, a sufficient amount of reactant may be at least 0.01 mg reactant/cm³ of reactor volume; alternatively at least 0.5 mg reactant/cm³ of reactor volume; alternatively 0.01 mg reactant/cm³ of reactor volume to maximum bulk density of the reactant in the reactor volume, alternatively 1 mg to 5,000 mg reactant/cm³ of reactor volume, alternatively 1 mg to 1 ,000 mg reactant/cm³ of reactor volume, and alternatively 1 mg to 900 mg reactant/cm³ of reactor volume.

[0044] The resulting reaction product of the method described above comprises the halosilane. The halosilane may have general formula (4-c)SiX_c, where each X is independently a halogen atom, and each R is independently a monovalent organic group, as described above; and subscript c is 0, 1 , 2, or 3. Alternatively, the halosilane may be a diorganodihalosilane of formula R2S1X2, where each X is independently a halogen atom, and each R is independently a monovalent organic group, as described above.

Alternatively, the halosilane may be a mixture of two or more organohalosilanes, e.g., a diorganodihalosilane and an organotrihalosilane or two or more different

diorganodihalosilanes.

[0045] The method described herein may optionally further comprise purging and/or treating. Purging and/or treating may be performed before contacting the copper silicide with the ingredient comprising the silane in step (1 ) and/or before contacting the reactant with the organohalide in step (2) and/or before contacting the spent reactant with the additional ingredient in step (3) and/or before the contacting the reactant re-formed in step (3) with the (additional) organohalide in step (4), and/or before step (5). The purging step comprises introducing a gas stream into the reactor containing the copper silicide, the reactant, and/or the spent reactant to remove unwanted materials. Unwanted materials in step (2), and when present step (4), may include, for example, H2, O2, H2O and HX, where X is a halogen atom as defined above. Purging may be accomplished with an inert gas, such as argon or nitrogen, or with a reactive gas, such as the organohalide;

alternatively purging may be performed with an inert gas. The treating step may comprise introducing a gas stream into the reactor containing the copper silicide to pre-treat the copper silicide before contacting it with the ingredient comprising the silane. Alternatively, the treating step may comprise introducing a gas stream into the reactor containing the reactant to activate and/or reduce it before contacting the reactant with the organohalide. Treating may be accomplished with a gas, such as H2 or the organohalide; alternatively

H2. Purging and/or treating may be performed at ambient or elevated temperature, e.g., at least 25 °C, alternatively at least 300 °C, alternatively 25 °C to 500 °C, and alternatively 300°C to 500 °C.

[0046] In step (2) of the method the reactant and the organohalide may be contacted in the absence of H2, in the absence of the silane, or in the absence of both H2 and the silane. [0047] The method may optionally further comprise steps (3) and (4) after step (2). Steps (3) and (4) may be performed separately and consecutively. The purpose of steps (3) and (4) is to recycle spent reactant by repeating steps (1 ) and (2), e.g., using spent reactant in place of the copper silicide used in step (1 ) of the method. The spent reactant after step (2) contains an amount of silicon less than the amount of silicon in the reactant before beginning step (2). The spent reactant left after step (4) contains an amount of silicon less than the amount of silicon in the reactant re-formed in step (3). For example, the amount of reduction in the amount of silicon in the reactant as compared to spent reactant may be greater than 90%, alternatively greater than 95%, alternatively greater than 99%, and alternatively 99.9%, of its initial weight. Alternatively, the amount of the reduction may be 90% to 99.9%.

[0048] Step (3) comprises contacting the spent reactant with an additional ingredient comprising an additional silane, under conditions as described above for step (1 ), at a temperature from 200 ¾ to 1400 °C to re-form the reactant comprising at least 0.1 % of Si. The additional silane used in step (3) may be more of the same silane used above in step (1 ). Alternatively, the additional silane used in step (3) may be a silane of formula

Ha^RbSiX(4-a-b) _> where at least one instance of R, X, subscript a, or subscript b is different than that used in the silane in step (1 ). H2 may be used in step (3) as described above for step (1 ). Step (4) comprises contacting the reactant re-formed in step (3) with additional organohalide (under conditions as described for step (2), above) at a temperature from 100 °C to 600 °C to form the reaction product comprising the halosilane.

[0049] Without wishing to be bound by theory, it is thought that the method described herein allows for maximizing the number of cycles for repeating steps (3) and (4). The method may optionally further comprise step (5), which is repeating steps (3) and (4) at least 1 time, alternatively from 1 to 10⁵ times, alternatively from 1 to 1 ,000 times, alternatively from 1 to 100 times, and alternatively from 1 to 10 times.

[0050] If the organohalide (or the silane) are liquids at or below standard temperature and pressure, the method may further comprise pre-heating and gasifying the organohalide (and/or the silane) by known methods before contacting the silane with the copper silicide in step (1 ), and/or the spent reactant step (3), and/or before contacting the organohalide with the reactant in step (2) and/or step (4). Alternatively, the method may further comprise bubbling the H2 through liquid silane to vaporize the silane before contacting with the copper silicide in step (1 ), and/or the spent reactant in step (3).

[0051 ] If the silane is a solid at or below standard temperature and pressure, the method may further comprise pre-heating above the melting point and liquefying or vaporizing the silane before bringing it in contact with the copper silicide in step (1 ) and/or the spent reactant in step (3). If the organohalide is a solid at or below standard temperature and pressure, the method may further comprise pre-heating above the melting point and liquefying or vaporizing the organohalide before bringing it in contact with reactant in step (2) and/or step (4).

[0052] The method may optionally further comprise step (5). Step (5) comprises recovering the reaction product produced (i.e., product of step (2) and/or step (4)). The reaction product comprises the halosilane described above. The halosilane may be recovered from the reaction product by, for example, removing gaseous product from the reactor followed by isolation by distillation. The halosilane may have general formula

R(4_-c)SiX_c, where each X is independently a halogen atom, and each R is independently a monovalent organic group, as described above; and subscript c is 0, 1 , 2, or 3.

Alternatively, the halosilane may have formula R2S1X2, where each R and X are as described above. Exemplary halosilanes that may be produced by the method include organotrihalosilanes and/or diorganodihalosilanes. Organotrihalosilanes are exemplified by methyltrichlorosilane, methyltribromosilane, and ethyltrichlorosilane. Examples of diorganodihalosilanes prepared according to the present process include, but are not limited to, dimethyldichlorosilane (i.e., (CH3)2SiCl2), dimethyldibromosilane,

diethyldichlorosilane, and diethyldibromosilane. Examples of other organohalosilanes that may be produced in addition to the diorganodihalosilane include, but are not limited to, methyltrichlorosilane (i.e., CH3SiCl3), and methyltribromosilane (i.e., CH3SiBr3).

[0053] A hydrogen halide may be present in the reaction product produced according the present method. The hydrogen halide has formula HX, where X is as defined above. The hydrogen halide may be separated from the halosilane via condensation, distillation, or other means and collected or fed to other chemical processes.

[0054] The method described herein produces halosilanes, particularly

organohalosilanes such as diorganodihalosilanes. The organohalosilanes may be used as reactants in hydrolysis processes to produce polyorganosiloxanes. Diorganodihalosilanes, such as dimethyldichlorosilane, can be used as reactants in processes for producing polydiorganosiloxanes. Organotrihalosilanes may be used as reactants in processes for producing polyorganosiloxanes, such as resins. The polyorganosiloxanes thus produced find use in many industries and applications.

[0055] The method described herein may offer the advantage of not producing large amounts of metal halide byproducts requiring costly disposal. Still further, the method may have good selectivity to produce diorganodihalosilanes, as compared to other halosilanes. Finally, the reactant may be re-formed and reused in the method, and the re-forming and reuse may provide increasing diorganodihalosilane production and/or selectivity.

EXAMPLES

[0056] 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. In the tables below, 'nd' means not done or not determined.

[0057] The reaction apparatus used in these examples 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. Brooks instrument 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 S1CI4 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.

[0058] The effluent of the reactor containing the reaction product 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 column suitable for analyzing chlorosilanes, 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.

[0059] In comparative example 1 , a metallic copper catalyst (4.15 grams) was treated with H2/S1CI4 for 30 min at 750 °C by bubbling H2 through the stainless steel S1CI4 bubbler.

The total flow of H2 and S1CI4 was 150 seem and the mole ratio of H2 to S1CI4 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 reactor containing the metallic 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. Use of metallic copper caused pressure to build within the system, not allowing for adequate H2/S1CI4 flow, therefore GC results were not accurate. Comparative

Example 1 demonstrated that metallic copper catalyst built up pressure within the reactor, and upon removal, was shown to be sintered together. The results are shown in Table 1 . Table 1 : Production of Trichlorosilane Using Metallic Copper Catalyst at 750 °C with H₂/SiCI₄ = 4

[0060] In example 1 , a sample of CU3S1 (0.6gm) was loaded into the flow-through, quartz tube reactor and treated with H₂ (30 mL/min) at 500 °C for 60.0 min. Next, a H₂ and S1CI4 gas mixture (H2/S1CI4 molar ratio of 4.0) was fed into the activated silicides bed at a temperature of 750 °C for 30 min. During this treatment process, production of HSiCl3

(28% yield) was seen as confirmed by GC/GC-MS analysis. Next, S1CI4 flow was stopped whereas H₂ was continuously flowed through the catalyst bed while the temperature of the reactor was lowered to 320 °C. At this stage, flow of H₂ was stopped and replaced with

MeCI at a flow rate of 5 seem. After 5 min, a gas sample was analyzed by GC/GC-MS that showed the presence of only Me₂SiCI₂ species selectively in low concentration. For next

40 min at 320 °C, only Me₂SiCI₂ was seen. When the temperature of reactor was increased to 350 °C, the Me₂SiCI₂ selectivity dropped to 78% with the balance of the reaction product as MeSiCl3 (22%). The reaction was continued until Me₂SiCI₂ selectivity dropped to 30%.

[0061 ] At this stage, MeCI flow was stopped and a H₂/SiCl4 gas mixture at 750 °C was flowed through the reactor. Next MeCI was fed in as described earlier at 350 °C, resulting in regeneration of Me₂SiCI₂ selectivity (84%).

[0062] In example 2, a sample of Cu3Si (0.6gm) was loaded into the reactor and treated with Argon (30 mL/min) at 400 °C for 120 min. The flow of argon was stopped and replaced with MeCI (5sccm) at 320 °C. After 5 min, a gas sample of the reactor effluent was analyzed by GC/GC-MS that showed the presence of methylchlorosilanes with Me₂SiCI₂ as the major species (73%). The reaction was continued for another 4 h until Me₂SiCI₂ selectivity dropped to 48%. At this stage MeCI flow was stopped and the spent reactant was treated with H₂ at 500 °C for 1 h and subsequently reacted with a H₂ and SiCl4 gas mixture (H₂/SiCl4 molar ratio of 4.0) at a temperature of 750 °C for 30 min. During this treatment step, production of HSiCl3 was seen as confirmed by GC/GC-MS analysis.

Next, S1CI4 flow was stopped, and H₂ was continuously flowed through the reactor while the temperature of the reactor was lowered to 320 °C. The flow of H2 was stopped and replaced with MeCI (5sccm). After 5 min, a gas sample of the reactor effluent was analyzed by GC/GC-MS that showed the presence of only Me2SiCl2 (100%) species selectively in low concentration. After 25 min, another gas injection to GC/GC-MS showed Me2SiCl2 selectivity dropped to 73% at the expense of MeSiCl3 production. The MeCI reaction was continued for additional 2 h resulting in reactor effluent containing Me2SiCl2 (44%), MeSiCI₃ (49%), and SiCU (7%).

[0063] In example 3, a sample of CU3S1 (0.5gm) was loaded into the flow-through, quartz tube reactor and treated with Argon (30 mL/min) at 400 °C for 120 min. The flow of argon was stopped and replaced with MeCI (5sccm) at 320 °C. After 5min, a sample of the reactor effluent was analyzed by GC/GC-MS that showed the presence of

methylchlorosilanes with Me2SiCl2 as the major species (73%). The reaction was continued for 9h resulting in production of Me2SiCl2 (50%), MeSiCl3 (19%), Μβββ (3%), SiCU (2%), MeHSiCI₂ (17%), and Me₂HSiCI (8%), with Si conversion = 25%. [0064] In example 4, three grams of CU5S1 (250um-1 .3mm, ACI alloys) were loaded into the reactor. The reactor was purged under N2 and pressure checked for any leaks. Then the reactor was heated under 100 seem of H2 at 500 °C for 2 hours, and then the temperature was increased to 750 °C and maintained for 30 min. After 30 minutes, the reactor temperature was decreased to 320 °C and when the reactor reached 320 °C, the reactor was purged with an argon flow of 50 seem for 30 min. After 30 min, the argon flow was ceased, and CH3CI (also designated MeCI) was fed through the reactor at a flow rate of 5 seem, 300 °C and atmospheric pressure for 90 min until no significant

methylchlorosilanes were observed in the reactor effluent analyzed by GC.

[0065] After this very first cycle (cycle 1 ), the copper catalyst was reduced by feeding 100 seem H2 at 500 °C to the reactor for 1 hour. Next, H2 and SiCl4 were fed to the reactor for

30 min at 750 °C by bubbling H2 through the stainless steel SiCl4 bubbler. The total flow of H2 and SiC was 150 seem with the mole ratio of H2 to SiCl4 of 1 :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 reactor containing the copper catalyst to form a reactant compromising 30 wt% Si. After 30 minutes, the S1CI4 flow was ceased and a hydrogen flow of 100 seem was maintained while cooling to 300 °C over 1 hour. When the reactor reached 300 °C, the reactor was purged with an argon flow of 50 seem for 30 min. [0066] After 30 min, the argon flow was ceased, and CH3CI (MeCI) was fed through the reactor at a flow rate of 5 seem, 300 °C and atmospheric pressure for 90 min. The reactor effluent was periodically sampled and analyzed by GC to determine the weight percent of (CH3)2SiCl2 and other chlorosilanes based on the total mass leaving the reactor.

Next, the CH3CI (MeCI) feed was ceased, and the spent reactant was treated with H2 at

500 °C for 30-60 min and contacted again with H2/SiCl4, to re-form the reactant, for 30 min at 750 °C. The combined flow rate of H2 and SiCl4 was 150 seem, and the mole ratio of H2 to S1CI4 was 1 :1 . After the reactant was re-formed, the reactor was purged with argon, again, and CH3CI (MeCI) was contacted with the re-formed reactant as described above. The cycle was repeated, and the results are shown in Table 4. This example

demonstrated that under the conditions of this example 4, a mixture of methylchlorosilanes was produced by the method with dimethyldichlorosilane being the major product.

Table 4: Production of methylchlorosilanes over CU5S1 catalyst treated at 750 °C with

H₂/SiCI₄ = 1 and 5 seem of CH3CI (MeCI) at 300 °C

[0067] In example 5, 2.5 grams of Cu3Si (250um-1 .3mm, ACI alloys) were loaded into the reactor. The reactor was purged with N2 and pressure checked for any leaks. Then the reactor was heated at 500 °C under 100 seem of H2 for 2 hours, and then the temperature was increased to 750 °C and maintained for 30 min. After 30 minutes, the reactor temperature was decreased to 320 °C, and when the reactor reached 320 °C, the reactor was purged with an argon flow of 50 seem for 30 min. After 30 min, the argon flow was ceased, and CH3CI (MeCI) was fed through the reactor at a flow rate of 5 seem, 300 °C and atmospheric pressure for 90 min, until no significant methylchlorosilanes were observed in the reactor effluent analyzed by GC.

[0068] After this first cycle, the copper catalyst was reduced by feeding 100 seem H2 into the reactor at 500 °C for 1 hour. Next, H2 and S1CI4 were fed into the reactor for 30 min at 750 °C by bubbling H2 through the stainless steel S1CI4 bubbler. The total flow of H2 and S1CI4 was 150 seem with the mole ratio of H2 to SiCl4 of 1 :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 reactor containing the copper catalyst to form the reactant comprising 30 wt% Si. After 30 minutes, the S1CI4 flow was ceased and a hydrogen flow of 100 seem was maintained while cooling to 300 °C over 1 hour. When the reactor reached 300 °C, the reactor was purged with an argon flow of 50 seem for 30 min. After 30 min, the argon flow was ceased, and CH3CI (MeCI) was fed through the reactor at a flow rate of 5 seem, 300 °C and atmospheric pressure for 90 min. The reactor effluent was periodically sampled and analyzed by GC to determine the weight percent of

(CH3)2SiCl2 and other chlorosilanes based on the total mass leaving the reactor.

[0069] Next, the CH3CI (MeCI) feed was ceased, and the spent reactant was treated with H₂ at 500 °C for 30-60 min and contacted again with H₂/SiCl4, for 30 min at 750 °C, to reform the reactant. The combined flow rate of H2 and SiCl4 was 150 seem, and the mole ratio of H2 to SiCl4 was 1 :1 . After the reactant was re-formed, the reactor was purged with argon, again, and CH3CI (MeCI) was contacted with the re-formed reactant as described above. The cycle was repeated, and this example demonstrated that under the conditions of this example 5, a mixture of methylchlorosilanes could be produced by the method with dimethyldichlorosilane being the major product.

[0070] Without wishing to be bound by theory, it is thought that the use of the copper silicide described herein may be more scalable to commercial processes than a similar process in which a supported copper catalyst is used instead of the copper silicide described herein. The use of the copper silicide may prevent sintering of the copper catalyst while being suitable to use in a commercial scale reactor, such as a fluidized bed reactor. [0071] The disclosure of ranges includes the range itself and also anything subsumed therein, as well as endpoints. For example, disclosure of a range of 2.0 to 4.0 includes not only the range of 2.0 to 4.0, but also 2.1 , 2.3, 3.4, 3.5, and 4.0 individually, as well as any other number subsumed in the range. Furthermore, disclosure of a range of, for example, 2.0 to 4.0 includes the subsets of, for example, 2.1 to 3.5, 2.3 to 3.4, 2.6 to 3.7, and 3.8 to 4.0, as well as any other subset subsumed in the range.

[0072] 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 with any other member or members of the group, and each member provides adequate support for specific embodiments within the scope of the appended claims. For example, disclosure of the Markush group: alkyl, aryl, and carbocyclic includes the member alkyl individually; the subgroup alkyl and aryl; and any other individual member and subgroup subsumed therein.

[0073] 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 200 to 1400" may be further delineated into a lower third, i.e., from 200 to 600, a middle third, i.e., from 600 to 1000, and an upper third, i.e., from 1000 to 1400, 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 35%, a subrange from 10% to 25%, a subrange from 23% to 30%, 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 "1 to 9" includes various individual integers, such as 3, as well as individual numbers including a decimal point (or fraction), such as 4.1 , which may be relied upon and provide adequate support for specific embodiments within the scope of the appended claims.

[0074] 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 for preparing a reaction product comprising a halosilane comprises separate and consecutive steps (1 ) and (2), where:

step (1 ) is contacting, at a temperature from 200 °C to 1400 °C, an ingredient comprising a silane of formula H_aRbSiX(4__a_b), where subscript a is 0 to 4, subscript b is 0 or 1 , a quantity (a + b) < 4, each R is independently a monovalent organic group, and each X is independently a halogen atom, with the proviso that when the quantity (a + b) < 4, then the ingredients further comprise H2; with a copper silicide; thereby forming a reactant; and step (2) is contacting the reactant with an organohalide at a temperature from

100 °C to 600 °C; thereby forming the reaction product and a spent reactant; and

2. A method for preparing a reaction product comprising a halosilane comprises:

optional step (1 ) contacting, at a temperature from 200 °C to 1400 °C, an ingredient comprising a silane of formula H_aRbSiX(4_-a-b), where subscript a is 0 to 4, subscript b is 0 or 1 , a quantity (a + b) < 4, each R is independently a monovalent organic group, and each X is independently a halogen atom, with the proviso that when the quantity (a + b) < 4, then the ingredient further comprises H2; with a copper silicide; thereby forming a reactant; and step (2) contacting the reactant with an organohalide at a temperature from 100 °C to 600 °C; thereby forming the reaction product and a spent reactant; with the proviso that when step (1 ) is present, steps (1 ) and (2) are performed separately and consecutively; and

step (3) is contacting, at a temperature from 200 °C to 1400°C, the spent reactant with an additional ingredient comprising an additional silane of formula H_aR|₃SiX(4_-a-|_:)), where subscript a is 0 to 4, subscript b is 0 or 1 , the quantity (a + b) < 4, each R is independently a monovalent organic group, and each X is independently a halogen atom, with the proviso that when the quantity (a + b) < 4, then the additional ingredient further comprises H2; thereby re-forming the reactant, and

3. The method of claim 1 or claim 2, where the copper silicide is one or more of CU7S1, Cu₅Si, Cu₄Si, and Cu₃Si.

4. The method of claim 1 or claim 2, further comprising purging and/or treating:

purging and/or treating the copper silicide, before contacting the copper silicide with the ingredient comprising the silane in step (1 ); and/or

purging and/or treating the reactant, before contacting the reactant with the organohalide in step (2); and/or

purging and/or treating, the spent reactant before contacting the spent reactant with the additional ingredient in step (3) ; and/or

purging and/or treating the reactant re-formed in step (3), before the contacting the reactant re-formed in step (3) with the additional organohalide in step (4); and/or

before step (5), purging and/or treating an additional spent reactant produced in step (4).

5. The method of claim 1 or claim 2, where in step (1 ), H2 is present, and a mole ratio of the H2 to the silane ranges from 20:1 to 1 :1 .

6. The method of claim 1 or claim 2, where the silane comprises one or more of a tetrahalosilane of formula S1X4, a trihalosilane of formula HS1X3, a dihalosilane of formula

H2S1X2, a monohalosilane of formula H3S1X, silane of formula S1H4, or a combination thereof.

7. The method of claim 1 or claim 2, where a = 0, b = 0, and the silane is a tetrahalosilane of formula S1X4.

8. The method of claim 1 or claim 2, where the organohalide has formula RX, where R is alkyl or aryl, and X is CI.

9. The method of of claim 1 or claim 2, where contacting the reactant with the organohalide in step (2), and when present step (4), is performed in the absence of H2.

10. The method of claim 1 or claim 2, where the reaction product comprises a halosilane of formula R(4-c)SiX_c, where subscript c is 0, 1 , 2, or 3.

1 1 . The method of claim 1 or claim 2, where the reaction product comprises a halosilane of formula R2SiX2-

12. The method of claim 10 or claim 1 1 , where R is alkyl or aryl; and X is CI, Br, or I.

13. A halosilane prepared by the method of any one of the preceding claims.

14. A method comprising using the halosilane of claim 13 as a reactant to make a polyorganosiloxane.

15. A polyorganosiloxane prepared by the method of claim 14.