WO2014172034A1 - Process for the production of silane products from calcium silicide - Google Patents

Process for the production of silane products from calcium silicide Download PDF

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Publication number
WO2014172034A1
WO2014172034A1 PCT/US2014/025583 US2014025583W WO2014172034A1 WO 2014172034 A1 WO2014172034 A1 WO 2014172034A1 US 2014025583 W US2014025583 W US 2014025583W WO 2014172034 A1 WO2014172034 A1 WO 2014172034A1
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silane
reactant
organohalide
alternatively
subscript
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PCT/US2014/025583
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French (fr)
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Kurt E. Anderson
Aswini K. Dash
Charles Alan Hall
Dimitris Katsoulis
Jonathan David Wineland
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Dow Corning Corporation
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Publication of WO2014172034A1 publication Critical patent/WO2014172034A1/en

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    • C—CHEMISTRY; METALLURGY
    • C07—ORGANIC CHEMISTRY
    • C07F—ACYCLIC, CARBOCYCLIC OR HETEROCYCLIC COMPOUNDS CONTAINING ELEMENTS OTHER THAN CARBON, HYDROGEN, HALOGEN, OXYGEN, NITROGEN, SULFUR, SELENIUM OR TELLURIUM
    • C07F7/00—Compounds containing elements of Groups 4 or 14 of the Periodic System
    • C07F7/02—Silicon compounds
    • C07F7/08—Compounds having one or more C—Si linkages
    • C07F7/12—Organo silicon halides
    • C—CHEMISTRY; METALLURGY
    • C01—INORGANIC CHEMISTRY
    • C01B—NON-METALLIC ELEMENTS; COMPOUNDS THEREOF; METALLOIDS OR COMPOUNDS THEREOF NOT COVERED BY SUBCLASS C01C
    • C01B33/00—Silicon; Compounds thereof
    • C01B33/08—Compounds containing halogen
    • C01B33/107—Halogenated silanes
    • C—CHEMISTRY; METALLURGY
    • C01—INORGANIC CHEMISTRY
    • C01B—NON-METALLIC ELEMENTS; COMPOUNDS THEREOF; METALLOIDS OR COMPOUNDS THEREOF NOT COVERED BY SUBCLASS C01C
    • C01B33/00—Silicon; Compounds thereof
    • C01B33/08—Compounds containing halogen
    • C01B33/107—Halogenated silanes
    • C01B33/10705—Tetrafluoride
    • C—CHEMISTRY; METALLURGY
    • C01—INORGANIC CHEMISTRY
    • C01B—NON-METALLIC ELEMENTS; COMPOUNDS THEREOF; METALLOIDS OR COMPOUNDS THEREOF NOT COVERED BY SUBCLASS C01C
    • C01B33/00—Silicon; Compounds thereof
    • C01B33/08—Compounds containing halogen
    • C01B33/107—Halogenated silanes
    • C01B33/1071—Tetrachloride, trichlorosilane or silicochloroform, dichlorosilane, monochlorosilane or mixtures thereof
    • C—CHEMISTRY; METALLURGY
    • C01—INORGANIC CHEMISTRY
    • C01B—NON-METALLIC ELEMENTS; COMPOUNDS THEREOF; METALLOIDS OR COMPOUNDS THEREOF NOT COVERED BY SUBCLASS C01C
    • C01B33/00—Silicon; Compounds thereof
    • C01B33/08—Compounds containing halogen
    • C01B33/107—Halogenated silanes
    • C01B33/10768—Tetrabromide; Tetraiodide
    • C—CHEMISTRY; METALLURGY
    • C07—ORGANIC CHEMISTRY
    • C07F—ACYCLIC, CARBOCYCLIC OR HETEROCYCLIC COMPOUNDS CONTAINING ELEMENTS OTHER THAN CARBON, HYDROGEN, HALOGEN, OXYGEN, NITROGEN, SULFUR, SELENIUM OR TELLURIUM
    • C07F7/00—Compounds containing elements of Groups 4 or 14 of the Periodic System
    • C07F7/02—Silicon compounds
    • C07F7/08—Compounds having one or more C—Si linkages
    • C07F7/0803—Compounds with Si-C or Si-Si linkages
    • C07F7/0805—Compounds with Si-C or Si-Si linkages comprising only Si, C or H atoms
    • C—CHEMISTRY; METALLURGY
    • C07—ORGANIC CHEMISTRY
    • C07F—ACYCLIC, CARBOCYCLIC OR HETEROCYCLIC COMPOUNDS CONTAINING ELEMENTS OTHER THAN CARBON, HYDROGEN, HALOGEN, OXYGEN, NITROGEN, SULFUR, SELENIUM OR TELLURIUM
    • C07F7/00—Compounds containing elements of Groups 4 or 14 of the Periodic System
    • C07F7/02—Silicon compounds
    • C07F7/08—Compounds having one or more C—Si linkages
    • C07F7/0803—Compounds with Si-C or Si-Si linkages
    • C07F7/0825—Preparations of compounds not comprising Si-Si or Si-cyano linkages
    • C07F7/0827—Syntheses with formation of a Si-C bond
    • C—CHEMISTRY; METALLURGY
    • C07—ORGANIC CHEMISTRY
    • C07F—ACYCLIC, CARBOCYCLIC OR HETEROCYCLIC COMPOUNDS CONTAINING ELEMENTS OTHER THAN CARBON, HYDROGEN, HALOGEN, OXYGEN, NITROGEN, SULFUR, SELENIUM OR TELLURIUM
    • C07F7/00—Compounds containing elements of Groups 4 or 14 of the Periodic System
    • C07F7/02—Silicon compounds
    • C07F7/08—Compounds having one or more C—Si linkages
    • C07F7/12—Organo silicon halides
    • C07F7/121—Preparation or treatment not provided for in C07F7/14, C07F7/16 or C07F7/20
    • C07F7/123—Preparation or treatment not provided for in C07F7/14, C07F7/16 or C07F7/20 by reactions involving the formation of Si-halogen linkages
    • Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
    • Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
    • Y02P—CLIMATE CHANGE MITIGATION TECHNOLOGIES IN THE PRODUCTION OR PROCESSING OF GOODS
    • Y02P20/00—Technologies relating to chemical industry
    • Y02P20/50—Improvements relating to the production of bulk chemicals
    • Y02P20/582—Recycling of unreacted starting or intermediate materials

Definitions

  • halosilanes are produced commercially by the Mueller-Rochow Direct Process, which comprises passing a halide compound over zero-valent silicon (Si 0 ) 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. When a hydrogen halide is used, a mixture of hydridohalosilanes is produced by the Direct Process.
  • the typical process for making the Si 0 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 Si 0 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 Si 0 .
  • halosilanes find use in different industries.
  • Hydridotrihalosilanes such as trichlorosilane (HSiCl3), are useful as reactants in chemical vapor deposition processes for making high purity polycrystalline silicon, which is used in solar cells (solar grade polysilicon) or electronic chips (semiconductor grade polysilicon).
  • hydridotrihalosilanes are useful as reactants in hydrolysis processes to produce polysiloxanes, such as resins.
  • Tetrahalosilanes can be used as reactants to make hydridohalosilanes and organohalosilanes.
  • Diorganodihalosilanes such as
  • dimethyldichlorosilane can be used as reactants to produce a wide range of
  • Organohydridohalosilanes can be used as reactants to make polyorganohydridosiloxanes, which are useful as waterproofing agents; alternatively organohydridohalosilanes can be used as reactants for making other organohalosilanes.
  • a process for preparing a reaction product comprising a silane product comprises:
  • step (ii) further comprises steps (ii) and (iii), where steps (ii) and (iii) are performed separately and consecutively after step (i), and where step (ii) is contacting, at a temperature from 200 °C to 1400 °C, the spent reactant with a silane of formula H a RbSiX(4_ a _b), where subscript a is 0 to 4, subscript b is 0 or 1 , a quantity (a + b) ⁇ 4, with the provisos that the silane of formula H a RbSiX(4_ a _b) is distinct from the silane product of formula Rm H nSiX(4-m-n) > ancl tnat wnen tne quantity (a + b) ⁇ 4, then step (ii) further comprises contacting the spent reactant with H2; thereby forming a reactant, and
  • step (iii) is contacting the reactant formed in step (ii) with an additional organohalide at a temperature from 300 °C to 700 °C to form an additional silane product of formula R m H n SiX(4 -m-n ).
  • Bu “Bu” means butyl and includes various structures including nBu, sec- butyl, tBu, and iBu.
  • Pr “Pr” means propyl and includes various structures such as iPr and nPr. iPr Isopropyl
  • AlkyI means an acyclic, branched or unbranched, saturated monovalent hydrocarbon group.
  • 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, as well as other branched, saturated monovalent hydrocarbon groups of 6 or more carbon atoms.
  • Alkyl groups have at least one carbon atom.
  • 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.
  • Alkyi 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 aralkyi groups include benzyl, tolyl, xylyl, phenylethyl, phenyl propyl, and phenyl butyl.
  • Aralkyi 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.
  • 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.
  • 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.
  • 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.
  • 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.
  • 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.
  • Cycloalkyl means a cyclic saturated hydrocarbon group, and cycloalkyl includes a saturated 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.
  • Calcium silicide means a material including both silicon and calcium that are intermixed at an atomic level, and the arrangement of the atoms can be described using crystal log raphic principles and models. Calcium silicides may be represented by the general formula Ca p Si q , where subscript p ⁇ 1 and subscript q > 1 ; alternatively 1 > p > 2, and 1 > q > 2. [0014] "Purging" means to introduce a gas stream to the reactor containing the calcium silicide, or the reactant, to remove unwanted gaseous or liquid materials.
  • 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 the reactor in a batch process.
  • residence time may refer to the time during which one reactor volume of the calcium silicide makes contact with the organohalide as the calcium silicide passes through the reactor system in a continuous process or during which the calcium silicide is placed within the reactor in a batch process.
  • residence time may refer to the time for one reactor volume of a reactant gas to pass through a reactor charged with the calcium silicide, e.g., the time for one reactor volume of the organohalide to pass through a reactor charged with the calcium silicide.
  • the process for preparing a reaction product comprising a silane product comprises:
  • process further comprises steps (ii) and (iii), where steps (ii) and (iii) are performed separately and consecutively after step (i), and where
  • step (ii) is contacting, at a temperature from 200 °C to 1400 °C, the spent reactant with a silane of formula H a RbSiX(4_ a _b), where subscript a is 0 to 4, subscript b is 0 or 1 , a quantity (a + b) ⁇ 4, with the provisos that the silane of formula H a RbSiX(4_ a _b) is distinct from the silane product of formula Rm H nSiX(4-m-n) > ancl tnat wnen tne quantity (a + b) ⁇ 4, then step (ii) further comprises contacting the spent reactant with H2; thereby forming a reactant, and
  • step (iii) is contacting the reactant formed in step (ii) with an additional organohalide at a temperature from 300 °C to 700 °C to form an additional silane product of formula R m H n SiX(4 -m-n) ,; and
  • step (iv) where step (iv) is repeating steps (ii) and (iii) at least one time to form a further additional silane product of formula R m H n SiX( 4-m-n) ;
  • step (v) is recovering the silane product after step (i) and/or step (iii) and/or step (iv).
  • An organohalide is used as a reactant in the process.
  • the organohalides described herein may be used as the additional organohalide in step (iii) as well as in step (i).
  • the specific organohalide selected for step (i) and step (iii) may be the same or different.
  • the organohalide used in the process may have formula RX, where each R is independently a monovalent organic group and X is a halogen atom.
  • R may be selected from the group consisting of alkyl, aralkyi, alkenyl, alkynyl, aryl, and carbocyclic, as defined above.
  • R may be an alkyl group or a cycloalkyl group.
  • R may be an alkyl group or an aryl group.
  • the alkyl groups for R may have 1 to 1 0 carbon atoms, alternatively 1 to 6 carbon atoms, and alternatively 1 to 4 carbon atoms.
  • the cycloalkyl groups for R may have 4 to 10 carbon atoms, alternatively 6 to 8 carbon atoms.
  • the aryl groups for R may have 4 to 10 carbon atoms, alternatively 6 to 8 carbon atoms.
  • Alkyl groups containing at least three carbon atoms may have a branched or unbranched structure.
  • R may be Me, Et, or Ph.
  • R may be Me.
  • X may be Br, CI or I ; alternatively Br or CI; and alternatively CI.
  • 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, cyclohexyl bromide, phenyl chloride, phenyl bromide, and phenyl iodide.
  • the organohalide may be an aliphatic hydrocarbyl halide.
  • the aliphatic hydrocarbyl halide may be a compound of formula H e CfXg, where subscript e represents average number of hydrogen atoms present, subscript f represents average number of carbon atoms present, and subscript g represents average number of halogen atoms present. Subscript e is 0 or more, subscript f is 1 or more, and subscript g is 1 or more.
  • a quantity (e + g) a quantity (2f + 2).
  • each X is independently a halogen atom , as described above.
  • subscript g may be 1 to 10, alternatively 1 to 6, alternatively 1 to 4, and alternatively 1 .
  • subscript g may be 1 to 4.
  • subscript g may be at least 2, alternatively 2 to 4.
  • suitable organohalides include, but are not limited to, methyl chloride (H3CCI), methylene chloride (H2CCI2), chloroform (HCCI3), carbon tetrachloride (CCI4), and dichloroethane.
  • a calcium silicide is reacted with an organohalide in step (i) of the process.
  • the calcium silicide is as defined above and may be a pre-formed calcium silicide.
  • the calcium silicide is exemplified by one or more of CaSi2, CaSi, and Ca2Si. Calcium silicides are commercially available.
  • the process may further comprise adding an additional ingredient ⁇ i.e., an ingredient other than the organohalide, described above) before and/or during contacting the organohalide and calcium silicide in step (i) (and/or before and/or during step (iii)).
  • This additional ingredient may be H2, a promoter, or both.
  • a promoter may be added during contacting the organohalide with the calcium silicide (and/or the reactant formed in step (ii)). Up to 5% of a promoter may be added, based on the combined weights of the organohalide and calcium silicide (or reactant).
  • the promoter may be selected from Al, Sn, Zn, and/or P, compounds, e.g., halides such as chlorides, of Al, Sn, Zn, and/or P, and combinations of two or more of said promoters.
  • the process can be performed in any reactor suitable for the combining of gases and solids or any reactor suitable for the combining of liquids and solids.
  • the reactor configuration can be a batch vessel, packed bed, stirred bed, vibrating bed, moving bed, re-circulating beds, or a fluidized bed.
  • the reactor for may be a packed bed, a stirred bed, or a fluidized bed.
  • the reactor may have means to control the temperature of the reaction zone, e.g., the portion of the reactor in which the organohalide contacts the calcium silicide.
  • the temperature at which the organohalide (and, when present, the additional ingredient) is contacted with the calcium silicide in step (i) (and/or the reactant in step (iii)) is 300 °C to 700 °C; alternatively 300 °C to 600 °C; alternatively 300 °C to 500 °C; alternatively 500°C to 700°C; alternatively 600°C to 700°C; alternatively 500°C to 600°C; alternatively 300 °C to 400 °C; alternatively 400 °C to 500 °C; alternatively 370°C to 400 °C; and alternatively 320 °C to 370 °C.
  • the pressure at which the organohalide (and, when present, the additional ingredient) are contacted with the calcium silicide in step (i) (and/or the reactant in step (iii)) can be sub-atmospheric, atmospheric, or super-atmospheric.
  • 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.
  • the mole ratio of H2 to organohalide contacted with the calcium silicide (and/or the reactant) 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 , alternatively 4:1 to 2:1 , and alternatively 4:1 to 1 :1 .
  • the residence time for the organohalide (and, when present the additional ingredient) in step (i) is sufficient for the organohalide (and, when present the additional ingredient) to contact the calcium silicide and form the silane product.
  • the residence time for the additional organohalide to contact the reactant in step (iii) and form the silane product may be the same or different from the residence time for step (i).
  • a sufficient residence time for step (i) (and/or step (iii)) 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, and alternatively 0.5 s to 10 s.
  • the desired residence time may be achieved by adjusting the flow rate of the organohalide (and the H2, when present), or by adjusting the total reactor volume, or by any combination thereof.
  • the organohalide and H2 may be fed to the reactor
  • the H2 and the organohalide may be mixed together before feeding to the reactor; alternatively, the H2 and the organohalide may be fed into the reactor as separate streams.
  • the calcium silicide is present in a sufficient amount in step (i).
  • a sufficient amount of calcium silicide is enough calcium silicide to form the silane product, described below, when the organohalide (and, when present the additional ingredient) is contacted with the calcium silicide.
  • a sufficient amount of calcium silicide may be at least 0.01 mg calcium silicide per cubic centimeter (mg CapSiq/cm 3 ) of reactor volume; alternatively at least 0.5 mg CapSiq/cm 3 of reactor volume, and alternatively 1 mg to
  • the reactant is present in a sufficient amount in step (iii).
  • the amount of the reactant may be the same or different from the amount of calcium silicide used in step (i).
  • the amount of reactant is exemplified by the amount of calcium silicide described above for step (i).
  • step (i) and step (iii) of the process may each independently be conducted for at least 0.1 s, alternatively 1 s to 30 hr, alternatively 1 min to 8 hr, alternatively 1 hr to 5 hr, and alternatively 3 hr to 30 hr.
  • Step (i) is typically conducted until the amount of silicon in the calcium silicide falls below a predetermined limit, e.g., until the calcium silicide is spent.
  • step (i) may be conducted until the amount of silicon in the calcium silicide is below 90%, alternatively 1 % to 90%, alternatively 1 % to 40%, of its initial weight percent.
  • the initial weight percent of silicon in the calcium silicide is the weight percent of silicon in the calcium silicide before the calcium silicide is contacted with the organohalide in step (i) (or the weight percent of silicon in the reactant after step (ii) and before step (iii)).
  • the amount of silicon in the calcium silicide and/or the reactant can be monitored by correlating production of the reaction product of step (i) (and/or step (iii)) with the weight percent of silicon in the calcium silicide (and/or the reactant) and then monitoring the reactor effluent or may be determined as described above.
  • the process further comprises steps (ii) and (iii) after step (i). Steps (ii) and (iii) are performed separately and consecutively. "Separate” and “separately” mean that step (ii) and step (iii) do not overlap or coincide. "Consecutive” and “consecutively” mean that step (iii) is performed after step (ii) in the process; however, additional steps may be performed between step (ii) and (iii), 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).
  • steps (ii) and (iii) are to recycle spent reactant formed in step (i).
  • a reactant comprising a calcium silicide will form in step (ii).
  • the reactant formed in step (ii) will then be reacted with additional organohalide in step (iii) (i.e., in place of the calcium silicide used in step (i) of the process).
  • the spent reactant after step (i) contains an amount of silicon less than the amount of silicon in the calcium silicide before beginning step (i).
  • the spent reactant left after step (iii) contains an amount of silicon less than the amount of silicon in the reactant formed in step (ii).
  • the amount of reduction in the amount of silicon in the spent reactant as compared to the reactant may be greater than 1 %, alternatively greater than 10%, alternatively greater than 20%, alternatively greater than 50%, greater than 90%, alternatively greater than 95%, alternatively greater than 99%, and alternatively 99.9%, of its initial weight.
  • the amount of the reduction may be 90% to 99.9%.
  • the amount of the reduction may be 1 % to 99.9%, and alternatively 10% to 99.9%.
  • Step (ii) comprises contacting the spent reactant with a silane, and optionally H2, at a temperature from 200 °C to 1400 °C to form a reactant, which comprises at least 0.1 % of Si.
  • the silane used in step (ii) has formula H a RbSiX(4_ a _b), where subscript a is 0 to 4, subscript b is 0 or 1 , a quantity (a + b) ⁇ 4, with the provisos that the silane of formula H a R bSiX(4-a-b) is distinct from the silane product of formula Rm H nSiX(4-m-n)> ancl tnat when the quantity (a + b) ⁇ 4, then the ingredient further comprises H2.
  • subscript b 0.
  • “Distinct” as used herein means that the silane of formula H a R
  • unreacted silane from step (ii) may be combined with the additional silane product in step (iii), and/or the further additional silane product of step (iv), and may be recovered in step (v).
  • the reactor in which step (ii) is performed may be any reactor suitable for the combining of gases and solids.
  • the reactor configuration can be a batch vessel, packed bed, stirred bed, vibrating bed, moving bed, re-circulating beds, or a fluidized bed.
  • the reactor for step (ii) may be the same as for step (i).
  • the reactor for step (ii) may be different than the reactor for step (i).
  • the calcium silicide (or the reactant) and spent reactant can be circulated from a bed for conducting step (i) (and/or step (iii)) to a bed for conducting step (ii).
  • the reactor should have means to control the temperature of the reaction zone, e.g., the portion of the reactor in which the silane contacts the calcium silicide in step (ii) and/or the portion of the reactor in which the organohalide contacts the reactant in step (iii).
  • the temperature at which the silane is contacted with the spent reactant in step (ii) 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.
  • the pressure at which the silane is contacted with the spent reactant in step (ii) can be sub-atmospheric, atmospheric, or super-atmospheric.
  • 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.
  • the mole ratio of H2 to silane contacted with the spent reactant in step (ii) 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 .
  • the residence time for the silane is sufficient for the silane to contact the spent reactant and form the reactant in step (ii).
  • a sufficient residence time for 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.
  • the residence time for the spent reactant to be in contact with the silane in step (ii) 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 ingredient comprising 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.
  • step (ii) 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.
  • the spent reactant is in a sufficient amount.
  • a sufficient amount of spent reactant is enough spent reactant to form the reactant, described below, when the ingredient comprising the silane is contacted with the spent reactant.
  • a sufficient amount of spent reactant may be at least 0.01 mg spent reactant/cm 3 of reactor volume; alternatively at least 0.5 mg spent reactant/cm 3 of reactor volume, and alternatively 1 mg spent reactant/cm 3 of reactor volume to maximum bulk density of the reactant (i.e., product of step ii)) based on the reactor volume, alternatively 1 mg to 1 ,200 mg spent reactant/cm 3 of reactor volume, alternatively 1 mg to 1 ,000 mg spent reactant/cm 3 of reactor volume, and alternatively 1 mg to 900 mg spent reactant/cm 3 of reactor volume.
  • step (ii) is usually conducted for at least 0.1 s, alternatively from 1 s to 5 hr, alternatively from 1 min to 1 hr.
  • the product of step (ii) is the reactant.
  • the reactant formed in step (ii) may comprise re-formed calcium silicide and optionally additional silicon deposited from the silane.
  • the reactant comprises an amount of silicon of at least 0.1 %, alternatively 0.1 % to 90%, alternatively 1 % to 60%, alternatively 1% to 50%, alternatively 1 % to 35%, and alternatively 0.1 % to 35%, based on the total weight of calcium and silicon in the reactant.
  • the percentage of silicon can be determined using standard analytical tests. For example, the percentage of Si may be determined using ICP-AES and ICP-MS.
  • Step (iii) comprises contacting the reactant formed in step (ii) with an additional organohalide under conditions as described for step (i), above to form the reaction product comprising the silane product.
  • the silane product produced in step (iii) may be the same as or different from the silane product produced in step (i). However the silane product produced in step (iii) has formula Rm H nSiX(4-m-n) > where R, m, and n are as described above.
  • step (iv) is repeating steps (ii) and (iii) at least 1 time, alternatively from 1 to 10 5 times, alternatively from 1 to 1 ,000 times, alternatively from 1 to 100 times, and alternatively from 1 to 10 times.
  • the process may further comprise vaporizing the organohalide by known methods, such as pre-heating, before contacting the organohalide with the calcium silicide in step (i) and/or before contacting the additional organohalide with the reactant in step (iii).
  • the process may further comprise bubbling the hydrogen through liquid organohalide to vaporize the organohalide before contacting with the calcium silicide in step (i) and/or before contacting the additional organohalide with the reactant in step (iii).
  • the process may further comprise pre-heating above the melting point and liquefying or vaporizing the organohalide before contacting with the calcium silicide in step (i) and/or before contacting the additional organohalide with the reactant in step (iii).
  • the process described herein may further comprise purging the reactor before contacting the organohalide with the calcium silicide in step (i) and/or before contacting the additional organohalide with the reactant in step (iii).
  • Purging 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, alternatively 300 °C to 500 °C, to remove unwanted materials, such as H2, O2, H2O and/or HX, where X is as defined above.
  • Purging may be accomplished with an inert gas, such as N2 or Ar, or with a reactive gas, such as H2 or the organohalide.
  • the process may further comprise recovering the silane product from the reaction product.
  • the silane product may be recovered from the reaction product by, for example, removing gaseous reaction product from the reactor followed by condensation and isolation of one or more silane product species in the reaction product by distillation.
  • the reaction product produced by the process described and exemplified herein comprises a silane product of formula Rm H nSiX(4-m-n) > where R and X, and subscripts m and n, are as defined and exemplified above.
  • subscript m is 0, 1 , 2, 3, or 4; and alternatively m is 0, 1 or 2.
  • subscript n is 0, 1 , or 2, and alternatively n is 0 or 1 .
  • the quantity (m + n) is 0, 1 , 2, or 3.
  • the quantity (m + n) is 2.
  • dihalosilanes prepared according to the present process include, but are not limited to, diorganodihalosilanes such as dimethyldichlorosilane (i.e., (CH3)2SiCl2), dimethyldibromosilane, diethyldichlorosilane, and diethyldibromosilane; or organohydridodihalosilanes, such as methyldichlorosilane (i.e., CH 3 (H)SiCI 2 ) and dimethylchlorosilane (i.e., (CH 3 ) 2 HSiCI).
  • diorganodihalosilanes such as dimethyldichlorosilane (i.e., (CH3)2SiCl2), dimethyldibromosilane, diethyldichlorosilane, and diethyldibromosilane
  • organohydridodihalosilanes such as methyldichloros
  • trihalosilanes examples include, but are not limited to, organotrihalosilanes such as methyltrichlorosilane (i.e., Ch ⁇ SiC ⁇ ), ethyltrichlorosilane (i.e., CH3CH2SiCl3), and methyltribromosilane (i.e., CH3SiBr3).
  • organotrihalosilanes such as methyltrichlorosilane (i.e., Ch ⁇ SiC ⁇ ), ethyltrichlorosilane (i.e., CH3CH2SiCl3), and methyltribromosilane (i.e., CH3SiBr3).
  • the process described herein may be used to produce hydridotrihalosilanes such as trichlorosilane (i.e., HS1CI3).
  • the process described herein may be used to produce silicon tetrahalides, such as silicon tetrach
  • reaction apparatus used was an open-ended glass tube with quartz wool to hold the calcium silicide in place.
  • the tube was connected to a flow reactor comprising a Lindberg/Blue Minimite 1 inch tube furnace and Brooks mass flow controller to control gas flow.
  • An O-ring was fitted over the glass tube at the inlet to prevent flow of gases around the outside.
  • the reactor effluent was passed through an actuated 6-way valve (Vici) with constant 100 uL injection loop before being discarded.
  • Samples were taken from the reactor effluent by actuating the injection valve and the 100 uL sample passed directly into the injection port of a 6890A Agilent GC and GC-MS equipped with a TCD and a FID for analysis.
  • the hydrogen was ultra high purity hydrogen from Airgas (Radnor, PA).
  • CaSi2, CaSi, and Ca2Si were obtained from ACI alloys.
  • Example 1 a sample of CaSi2 (0.52gm) was loaded into the reactor and purged with Argon (30 seem) at 200 °C for 60 min. Argon flow was stopped and the sample was treated with H2 (30sccm) at 500 °C for 2h. Next, H2 flow was replaced with Argon and the temperature of the reactor tube was reduced to 300 °C. Subsequently, Argon flow was ceased, and MeCI was flowed through the reactor. Samples were taken from the reactor effluent and injected into a GC/GC-MS for analysis using an online switching valve. The reaction was run while varying the reaction temperature as well as repetition experiments carried out under the same reaction conditions. The data are summarized in Table 1 . Table 1 : CaSi2 reaction with MeCI
  • MeSiCl3(6.0%) The balance was a mixture of methylene and bis-methylene chloromethyl silanes of formula [Me x ClySi] 2 (CH 2 ) z , where subscript x is 1 , 2, or 3; subscript y is 1 2 or
  • 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.
  • a range of "300 to 700" may be further delineated into a lower third, i.e., 300 to 433, a middle third, i.e., 434 to 566, and an upper third, i.e., 567 to 700, 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
  • 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.

Abstract

A process for preparing a reaction product including a silane product includes step (i), (ii), and (iii). Step (i) is contacting an organohalide with a calcium silicide at a temperature from 300 °C to 700 °C to form the reaction product including a spent reactant and the silane product. The silane product has formula RmHnSiX(4-m-n), where each R is independently a monovalent organic group, each X is independently a halogen atom; subscript m is 0 to 4; subscript n is 0 to 2; and a quantity (m + n) is 0 to 4. Step (ii) is contacting, at a temperature from 200 °C to 1400 °C, the spent reactant with a silane of formula HaRbSiX(4-a-b), where subscript a is 0 to 4, subscript b is 0 or 1, a quantity (a + b) ≤ 4. The silane of formula HaRbSiX(4-a-b) is distinct from the silane product of formula RmHnSiX(4-m-n). When the quantity (a + b) < 4, then step (ii) further includes contacting the spent reactant with H2; thereby forming a reactant. Step (iii) is contacting the reactant formed in step (ii) with an additional organohalide at a temperature from 300 °C to 700 °C to form an additional silane product of formula RmHnSiX(4-m-n). Steps (ii) and (iii) are performed separately and consecutively after step (i).

Description

Process for the Production of Silane Products from Calcium Silicide
[0001] 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. When a hydrogen halide is used, a mixture of hydridohalosilanes is produced by the Direct Process.
[0002] 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.
[0003] Various halosilanes find use in different industries. Hydridotrihalosilanes, such as trichlorosilane (HSiCl3), are useful as reactants in chemical vapor deposition processes for making high purity polycrystalline silicon, which is used in solar cells (solar grade polysilicon) or electronic chips (semiconductor grade polysilicon). Alternatively, hydridotrihalosilanes are useful as reactants in hydrolysis processes to produce polysiloxanes, such as resins. Tetrahalosilanes can be used as reactants to make hydridohalosilanes and organohalosilanes. Diorganodihalosilanes, such as
dimethyldichlorosilane, can be used as reactants to produce a wide range of
polyorganosiloxanes, such as polydiorganosiloxanes. Organohydridohalosilanes can be used as reactants to make polyorganohydridosiloxanes, which are useful as waterproofing agents; alternatively organohydridohalosilanes can be used as reactants for making other organohalosilanes.
BRIEF SUMMARY OF THE INVENTION
[0004] A process for preparing a reaction product comprising a silane product comprises:
(i) contacting an organohalide with a calcium silicide at a temperature from 300 °C to 700 °C to form the reaction product comprising a spent reactant and the silane product, where the silane product has formula RmHnSiX(4-m-n)> where each R is independently a monovalent organic group, each X is independently a halogen atom; subscript m is 0 to 4; subscript n is 0 to 2; and a quantity (m + n) is 0 to 4; and
where the process further comprises steps (ii) and (iii), where steps (ii) and (iii) are performed separately and consecutively after step (i), and where step (ii) is contacting, at a temperature from 200 °C to 1400 °C, the spent reactant with a silane of formula HaRbSiX(4_a_b), where subscript a is 0 to 4, subscript b is 0 or 1 , a quantity (a + b) < 4, with the provisos that the silane of formula HaRbSiX(4_a_b) is distinct from the silane product of formula RmHnSiX(4-m-n)> ancl tnat wnen tne quantity (a + b) < 4, then step (ii) further comprises contacting the spent reactant with H2; thereby forming a reactant, and
step (iii) is contacting the reactant formed in step (ii) with an additional organohalide at a temperature from 300 °C to 700 °C to form an additional silane product of formula RmHnSiX(4-m-n).
DETAILED DESCRIPTION OF THE INVENTION
[0005] 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 1 , below.
Table 1 - Abbreviations
Abbreviation Word
% Percent
°C degrees Celsius
Bu "Bu" means butyl and includes various structures including nBu, sec- butyl, tBu, and iBu.
iBu Isobutyl
nBu normal butyl
tBu tertiary butyl
cm Centimeter
Et Ethyl
FID flame ionization detector
g Gram
GC gas chromatograph and/or gas chromatography
GC-MS gas chromatograph- mass spectrometer and/or gas chromatography- mass spectrometry
hr Hour
ICP-AES Inductively Coupled Plasma Atomic Emission Spectroscopy
ICP-MS Inductively Coupled Plasma Mass Spectrometry
kPa kilopascals Abbreviation Word
Me Methyl
mg Milligram
min Minutes
mL Milliliters
mol mole
P pressure
Ph Phenyl
Pr "Pr" means propyl and includes various structures such as iPr and nPr. iPr Isopropyl
nPr normal propyl
s Seconds
seem standard cubic centimeters per minute
TCD thermal conductivity detector
uL Microliter
Vi Vinyl
Yield (%) Mole %, based on all silicon containing compounds, of halosilane in the reaction product
[0006] "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, as well as other branched, saturated monovalent hydrocarbon groups of 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.
[0007] "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 aralkyi groups include benzyl, tolyl, xylyl, phenylethyl, phenyl propyl, and phenyl butyl. Aralkyi 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. [0008] "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.
[0009] "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.
[0010] "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.
[0011] "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.
[0012] "Cycloalkyl" means a cyclic saturated hydrocarbon group, and cycloalkyl includes a saturated 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.
[0013] "Calcium silicide" means a material including both silicon and calcium that are intermixed at an atomic level, and the arrangement of the atoms can be described using crystal log raphic principles and models. Calcium silicides may be represented by the general formula CapSiq, where subscript p≥ 1 and subscript q > 1 ; alternatively 1 > p > 2, and 1 > q > 2. [0014] "Purging" means to introduce a gas stream to the reactor containing the calcium silicide, or the reactant, to remove unwanted gaseous or liquid materials.
[0015] "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 the reactor in a batch process. For example, residence time may refer to the time during which one reactor volume of the calcium silicide makes contact with the organohalide as the calcium silicide passes through the reactor system in a continuous process or during which the calcium silicide is placed within the reactor in a batch process. Alternatively, residence time may refer to the time for one reactor volume of a reactant gas to pass through a reactor charged with the calcium silicide, e.g., the time for one reactor volume of the organohalide to pass through a reactor charged with the calcium silicide.
[0016] The process for preparing a reaction product comprising a silane product comprises:
(i) contacting an organohalide with a calcium silicide at a temperature from 300 °C to 700 °C to form the reaction product comprising a spent reactant and the silane product, where the silane product has formula RmHnSiX(4-m-n), where each R is independently a monovalent organic group, each X is independently a halogen atom ; subscript m is 0 to 4; subscript n is 0 to 2; and a quantity (m + n) is 0 to 4; and
where the process further comprises steps (ii) and (iii), where steps (ii) and (iii) are performed separately and consecutively after step (i), and where
step (ii) is contacting, at a temperature from 200 °C to 1400 °C, the spent reactant with a silane of formula HaRbSiX(4_a_b), where subscript a is 0 to 4, subscript b is 0 or 1 , a quantity (a + b) < 4, with the provisos that the silane of formula HaRbSiX(4_a_b) is distinct from the silane product of formula RmHnSiX(4-m-n)> ancl tnat wnen tne quantity (a + b) < 4, then step (ii) further comprises contacting the spent reactant with H2; thereby forming a reactant, and
step (iii) is contacting the reactant formed in step (ii) with an additional organohalide at a temperature from 300 °C to 700 °C to form an additional silane product of formula RmHnSiX(4-m-n),; and
where the process optionally further comprises step (iv), where step (iv) is repeating steps (ii) and (iii) at least one time to form a further additional silane product of formula RmHnSiX(4-m-n) ; and
where the process optionally further comprises step (v), where step (v) is recovering the silane product after step (i) and/or step (iii) and/or step (iv). [0017] An organohalide is used as a reactant in the process. The organohalides described herein may be used as the additional organohalide in step (iii) as well as in step (i). The specific organohalide selected for step (i) and step (iii) may be the same or different.
[0018] The organohalide used in the process may have formula RX, where each R is independently a monovalent organic group and X is a halogen atom. R may be selected from the group consisting of alkyl, aralkyi, alkenyl, alkynyl, aryl, and carbocyclic, as defined above. Alternatively, R may be an alkyl group or a cycloalkyl group. Alternatively, R may be an alkyl group or an aryl group. The alkyl groups for R may have 1 to 1 0 carbon atoms, alternatively 1 to 6 carbon atoms, and alternatively 1 to 4 carbon atoms. The cycloalkyl groups for R may have 4 to 10 carbon atoms, alternatively 6 to 8 carbon atoms. The aryl groups for R may have 4 to 10 carbon atoms, alternatively 6 to 8 carbon atoms. Alkyl groups containing at least three carbon atoms may have a branched or unbranched structure. Alternatively, R may be Me, Et, or Ph. Alternatively, R may be Me.
Alternatively, X may be Br, CI or I ; alternatively Br or CI; and alternatively 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, cyclohexyl bromide, phenyl chloride, phenyl bromide, and phenyl iodide.
[0019] Alternatively, the organohalide may be an aliphatic hydrocarbyl halide. The aliphatic hydrocarbyl halide may be a compound of formula HeCfXg, where subscript e represents average number of hydrogen atoms present, subscript f represents average number of carbon atoms present, and subscript g represents average number of halogen atoms present. Subscript e is 0 or more, subscript f is 1 or more, and subscript g is 1 or more. When the organohalide is a noncyclic aliphatic hydrocarbyl halide, then a quantity (e + g) = a quantity (2f + 2). When the organohalide is a monocyclic cycloalkyl halide, then the quantity (e + g) = 2f. Each X is independently a halogen atom , as described above. Alternatively, subscript g may be 1 to 10, alternatively 1 to 6, alternatively 1 to 4, and alternatively 1 . Alternatively, subscript g may be 1 to 4. Alternatively, subscript g may be at least 2, alternatively 2 to 4. Examples of suitable organohalides include, but are not limited to, methyl chloride (H3CCI), methylene chloride (H2CCI2), chloroform (HCCI3), carbon tetrachloride (CCI4), and dichloroethane.
[0020] A calcium silicide is reacted with an organohalide in step (i) of the process. The calcium silicide is as defined above and may be a pre-formed calcium silicide. The calcium silicide is exemplified by one or more of CaSi2, CaSi, and Ca2Si. Calcium silicides are commercially available. The process may further comprise adding an additional ingredient {i.e., an ingredient other than the organohalide, described above) before and/or during contacting the organohalide and calcium silicide in step (i) (and/or before and/or during step (iii)). This additional ingredient may be H2, a promoter, or both.
[0021] In step (i) and/or step (iii) of the process described herein, a promoter may be added during contacting the organohalide with the calcium silicide (and/or the reactant formed in step (ii)). Up to 5% of a promoter may be added, based on the combined weights of the organohalide and calcium silicide (or reactant). The promoter may be selected from Al, Sn, Zn, and/or P, compounds, e.g., halides such as chlorides, of Al, Sn, Zn, and/or P, and combinations of two or more of said promoters.
[0022] The process can be performed in any reactor suitable for the combining of gases and solids or any reactor suitable for the combining of liquids 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. Alternatively, the reactor for may be a packed bed, a stirred bed, or a fluidized bed. To facilitate reaction, the reactor may have means to control the temperature of the reaction zone, e.g., the portion of the reactor in which the organohalide contacts the calcium silicide.
[0023] The temperature at which the organohalide (and, when present, the additional ingredient) is contacted with the calcium silicide in step (i) (and/or the reactant in step (iii)) is 300 °C to 700 °C; alternatively 300 °C to 600 °C; alternatively 300 °C to 500 °C; alternatively 500°C to 700°C; alternatively 600°C to 700°C; alternatively 500°C to 600°C; alternatively 300 °C to 400 °C; alternatively 400 °C to 500 °C; alternatively 370°C to 400 °C; and alternatively 320 °C to 370 °C.
[0024] The pressure at which the organohalide (and, when present, the additional ingredient) are contacted with the calcium silicide in step (i) (and/or the reactant in step (iii)) 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.
[0025] When H2 is present, the mole ratio of H2 to organohalide contacted with the calcium silicide (and/or the reactant) 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 , alternatively 4:1 to 2:1 , and alternatively 4:1 to 1 :1 .
[0026] The residence time for the organohalide (and, when present the additional ingredient) in step (i) is sufficient for the organohalide (and, when present the additional ingredient) to contact the calcium silicide and form the silane product. (The residence time for the additional organohalide to contact the reactant in step (iii) and form the silane product may be the same or different from the residence time for step (i).) For example, a sufficient residence time for step (i) (and/or step (iii)) 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, and alternatively 0.5 s to 10 s. The desired residence time may be achieved by adjusting the flow rate of the organohalide (and the H2, when present), or by adjusting the total reactor volume, or by any combination thereof.
[0027] When H2 is used, the organohalide and H2 may be fed to the reactor
simultaneously; however, other methods of combining, such as by separate pulses or separate streams, are also envisioned. The H2 and the organohalide may be mixed together before feeding to the reactor; alternatively, the H2 and the organohalide may be fed into the reactor as separate streams.
[0028] The calcium silicide is present in a sufficient amount in step (i). A sufficient amount of calcium silicide is enough calcium silicide to form the silane product, described below, when the organohalide (and, when present the additional ingredient) is contacted with the calcium silicide. For example, a sufficient amount of calcium silicide may be at least 0.01 mg calcium silicide per cubic centimeter (mg CapSiq/cm3) of reactor volume; alternatively at least 0.5 mg CapSiq/cm3 of reactor volume, and alternatively 1 mg to
10,000 mg CapSiq/cm3 of reactor volume, where subscripts p and q are as defined above.
The reactant is present in a sufficient amount in step (iii). The amount of the reactant may be the same or different from the amount of calcium silicide used in step (i). The amount of reactant is exemplified by the amount of calcium silicide described above for step (i).
[0029] There is no upper limit on the time for which step (i) (and step (iii) of the process is conducted. For example, step (i) and step (iii) of the process may each independently be conducted for at least 0.1 s, alternatively 1 s to 30 hr, alternatively 1 min to 8 hr, alternatively 1 hr to 5 hr, and alternatively 3 hr to 30 hr.
[0030] Step (i) is typically conducted until the amount of silicon in the calcium silicide falls below a predetermined limit, e.g., until the calcium silicide is spent. For example, step (i) may be conducted until the amount of silicon in the calcium silicide is below 90%, alternatively 1 % to 90%, alternatively 1 % to 40%, of its initial weight percent. The initial weight percent of silicon in the calcium silicide is the weight percent of silicon in the calcium silicide before the calcium silicide is contacted with the organohalide in step (i) (or the weight percent of silicon in the reactant after step (ii) and before step (iii)). The amount of silicon in the calcium silicide and/or the reactant can be monitored by correlating production of the reaction product of step (i) (and/or step (iii)) with the weight percent of silicon in the calcium silicide (and/or the reactant) and then monitoring the reactor effluent or may be determined as described above.
[0031 ] The process further comprises steps (ii) and (iii) after step (i). Steps (ii) and (iii) are performed separately and consecutively. "Separate" and "separately" mean that step (ii) and step (iii) do not overlap or coincide. "Consecutive" and "consecutively" mean that step (iii) is performed after step (ii) in the process; however, additional steps may be performed between step (ii) and (iii), 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). The purpose of steps (ii) and (iii) is to recycle spent reactant formed in step (i). Without wishing to be bound by theory, it is thought that a reactant comprising a calcium silicide will form in step (ii). The reactant formed in step (ii) will then be reacted with additional organohalide in step (iii) (i.e., in place of the calcium silicide used in step (i) of the process). The spent reactant after step (i) contains an amount of silicon less than the amount of silicon in the calcium silicide before beginning step (i). The spent reactant left after step (iii) contains an amount of silicon less than the amount of silicon in the reactant formed in step (ii). For example, the amount of reduction in the amount of silicon in the spent reactant as compared to the reactant may be greater than 1 %, alternatively greater than 10%, alternatively greater than 20%, alternatively greater than 50%, 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%. Alternatively, the amount of the reduction may be 1 % to 99.9%, and alternatively 10% to 99.9%.
[0032] Step (ii) comprises contacting the spent reactant with a silane, and optionally H2, at a temperature from 200 °C to 1400 °C to form a reactant, which comprises at least 0.1 % of Si. The silane used in step (ii) has formula HaRbSiX(4_a_b), where subscript a is 0 to 4, subscript b is 0 or 1 , a quantity (a + b) < 4, with the provisos that the silane of formula HaRbSiX(4-a-b) is distinct from the silane product of formula RmHnSiX(4-m-n)> ancl tnat when the quantity (a + b) < 4, then the ingredient further comprises H2. Alternatively, subscript a is 3 or 4; and alternatively subscript a = 4. Alternatively, subscript b = 0.
"Distinct" as used herein means that the silane of formula HaR|3SiX(4-a-|3) and the silane product of formula RmHnSiX(4-m-n) differ from one another. At least one of the following conditions is met: a≠ n, b≠ m, and/or (4-m-n)≠ (4-a-b). One skilled in the art would recognize that unreacted silane from step (ii) may be combined with the additional silane product in step (iii), and/or the further additional silane product of step (iv), and may be recovered in step (v). [0033] The reactor in which step (ii) 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. The reactor for step (ii) may be the same as for step (i). Alternatively, the reactor for step (ii) may be different than the reactor for step (i). When using re-circulating beds, the calcium silicide (or the reactant) and spent reactant can be circulated from a bed for conducting step (i) (and/or step (iii)) to a bed for conducting step (ii). 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 silane contacts the calcium silicide in step (ii) and/or the portion of the reactor in which the organohalide contacts the reactant in step (iii).
[0034] The temperature at which the silane is contacted with the spent reactant in step (ii) 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.
[0035] The pressure at which the silane is contacted with the spent reactant in step (ii) 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.
[0036] The mole ratio of H2 to silane contacted with the spent reactant in step (ii) 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 .
[0037] The residence time for the silane is sufficient for the silane to contact the spent reactant and form the reactant in step (ii). For example, a sufficient residence time for 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 spent reactant to be in contact with the silane in step (ii) 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 ingredient comprising 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.
[0038] In step (ii), 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.
[0039] In step (ii), the spent reactant is in a sufficient amount. A sufficient amount of spent reactant is enough spent reactant to form the reactant, described below, when the ingredient comprising the silane is contacted with the spent reactant. For example, a sufficient amount of spent reactant may be at least 0.01 mg spent reactant/cm3 of reactor volume; alternatively at least 0.5 mg spent reactant/cm3 of reactor volume, and alternatively 1 mg spent reactant/cm3 of reactor volume to maximum bulk density of the reactant (i.e., product of step ii)) based on the reactor volume, alternatively 1 mg to 1 ,200 mg spent reactant/cm3 of reactor volume, alternatively 1 mg to 1 ,000 mg spent reactant/cm3 of reactor volume, and alternatively 1 mg to 900 mg spent reactant/cm3 of reactor volume.
[0040] There is no upper limit on the time for which step (ii) is conducted. For example, step (ii) is usually conducted for at least 0.1 s, alternatively from 1 s to 5 hr, alternatively from 1 min to 1 hr.
[0041] The product of step (ii) is the reactant. Without wishing to be bound by theory, it is thought that the reactant formed in step (ii) may comprise re-formed calcium silicide and optionally additional silicon deposited from the silane. The reactant comprises an amount of silicon of at least 0.1 %, alternatively 0.1 % to 90%, alternatively 1 % to 60%, alternatively 1% to 50%, alternatively 1 % to 35%, and alternatively 0.1 % to 35%, based on the total weight of calcium and silicon in the reactant. The percentage of silicon can be determined using standard analytical tests. For example, the percentage of Si may be determined using ICP-AES and ICP-MS.
[0042] Step (iii) comprises contacting the reactant formed in step (ii) with an additional organohalide under conditions as described for step (i), above to form the reaction product comprising the silane product. The silane product produced in step (iii) may be the same as or different from the silane product produced in step (i). However the silane product produced in step (iii) has formula RmHnSiX(4-m-n)> where R, m, and n are as described above.
[0043] Without wishing to be bound by theory, it is thought that the process described herein allows for maximizing the number of cycles for repeating steps (ii) and (iii). The process may optionally further comprise step (iv), which is repeating steps (ii) and (iii) 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. [0044] If the organohalide is a liquid at or below standard temperature and pressure (or the temperature and pressure selected for the process), the process may further comprise vaporizing the organohalide by known methods, such as pre-heating, before contacting the organohalide with the calcium silicide in step (i) and/or before contacting the additional organohalide with the reactant in step (iii). Alternatively, the process may further comprise bubbling the hydrogen through liquid organohalide to vaporize the organohalide before contacting with the calcium silicide in step (i) and/or before contacting the additional organohalide with the reactant in step (iii).
[0045] If the organohalide is a solid at or below standard temperature and pressure, the process may further comprise pre-heating above the melting point and liquefying or vaporizing the organohalide before contacting with the calcium silicide in step (i) and/or before contacting the additional organohalide with the reactant in step (iii).
[0046] The process described herein may further comprise purging the reactor before contacting the organohalide with the calcium silicide in step (i) and/or before contacting the additional organohalide with the reactant in step (iii). Purging 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, alternatively 300 °C to 500 °C, to remove unwanted materials, such as H2, O2, H2O and/or HX, where X is as defined above. Purging may be accomplished with an inert gas, such as N2 or Ar, or with a reactive gas, such as H2 or the organohalide.
[0047] The process may further comprise recovering the silane product from the reaction product. The silane product may be recovered from the reaction product by, for example, removing gaseous reaction product from the reactor followed by condensation and isolation of one or more silane product species in the reaction product by distillation. The reaction product produced by the process described and exemplified herein comprises a silane product of formula RmHnSiX(4-m-n)> where R and X, and subscripts m and n, are as defined and exemplified above. Alternatively, subscript m is 0, 1 , 2, 3, or 4; and alternatively m is 0, 1 or 2. Alternatively, subscript n is 0, 1 , or 2, and alternatively n is 0 or 1 . Alternatively, the quantity (m + n) is 0, 1 , 2, or 3. Alternatively, the quantity (m + n) is 2.
[0048] The process described herein may be used to produce various silanes such as trihalosilanes, dihalosilanes, and tetrahalosilanes. Examples of dihalosilanes prepared according to the present process include, but are not limited to, diorganodihalosilanes such as dimethyldichlorosilane (i.e., (CH3)2SiCl2), dimethyldibromosilane, diethyldichlorosilane, and diethyldibromosilane; or organohydridodihalosilanes, such as methyldichlorosilane (i.e., CH3(H)SiCI2) and dimethylchlorosilane (i.e., (CH3)2HSiCI). Examples of other trihalosilanes that may be produced include, but are not limited to, organotrihalosilanes such as methyltrichlorosilane (i.e., Ch^SiC^), ethyltrichlorosilane (i.e., CH3CH2SiCl3), and methyltribromosilane (i.e., CH3SiBr3). Alternatively, the process described herein may be used to produce hydridotrihalosilanes such as trichlorosilane (i.e., HS1CI3). Alternatively, the process described herein may be used to produce silicon tetrahalides, such as silicon tetrachloride (i.e., S1CI4) . Alternatively, the process described herein may be used to produce tetraorganosilanes, such as Me4Si or Et4Si.
EXAMPLES
[0049] 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 these examples, the reaction apparatus used was an open-ended glass tube with quartz wool to hold the calcium silicide in place. The tube was connected to a flow reactor comprising a Lindberg/Blue Minimite 1 inch tube furnace and Brooks mass flow controller to control gas flow. An O-ring was fitted over the glass tube at the inlet to prevent flow of gases around the outside. The reactor effluent was passed through an actuated 6-way valve (Vici) with constant 100 uL injection loop before being discarded. Samples were taken from the reactor effluent by actuating the injection valve and the 100 uL sample passed directly into the injection port of a 6890A Agilent GC and GC-MS equipped with a TCD and a FID for analysis. The hydrogen was ultra high purity hydrogen from Airgas (Radnor, PA). CaSi2, CaSi, and Ca2Si were obtained from ACI alloys.
[0050] In example 1 , a sample of CaSi2 (0.52gm) was loaded into the reactor and purged with Argon (30 seem) at 200 °C for 60 min. Argon flow was stopped and the sample was treated with H2 (30sccm) at 500 °C for 2h. Next, H2 flow was replaced with Argon and the temperature of the reactor tube was reduced to 300 °C. Subsequently, Argon flow was ceased, and MeCI was flowed through the reactor. Samples were taken from the reactor effluent and injected into a GC/GC-MS for analysis using an online switching valve. The reaction was run while varying the reaction temperature as well as repetition experiments carried out under the same reaction conditions. The data are summarized in Table 1 . Table 1 : CaSi2 reaction with MeCI
Figure imgf000014_0001
[0051] In example 2, a sample of CaSi (0.52 gm) was loaded into the reactor and purged with Argon (30 seem) at 200 °C for 60 min. Argon flow was stopped and the sample was treated with H2 (30sccm) at 500 °C for 2h. Next, H2 flow was replaced with Argon and the temperature of the reactor was lowered to 300 °C. Next, Argon flow was ceased, and MeCI was flowed through the reactor. Samples were taken from the reactor effluent and injected into a GC/GC-MS for analysis using an online switching valve. The reaction was run while varying the reaction temperature as well as repetition experiments carried out under the same reaction conditions. At 420 °C, the product composition contained Me4Si(4.1 %),
Me2HSiCI(1 .3%), MeHSiCI2(6.1 %), Me3SiCI(5.2%), SiCI4(13.2%), Me2SiCI2(3.3%) and
MeSiCl3(6.0%). The balance was a mixture of methylene and bis-methylene chloromethyl silanes of formula [MexClySi]2(CH2)z, where subscript x is 1 , 2, or 3; subscript y is 1 2 or
3, subscript z is 1 or 2; with the proviso that a quantity (x + y) = 3.
[0052] In example 3, a sample of Ca2Si (0.6gm) was loaded into the reactor and purged with Argon (30 seem) at 200 °C for 60 min. Argon flow was stopped and the sample was treated with H2 (30sccm) at 500 °C for 2h. Next, H2 flow was replaced with Argon and the temperature of the reactor tube was reduced to 300 °C. Then, Argon flow was ceased, and MeCI was flowed through the reactor. Samples were taken from the reactor effluent and injected into a GC/GC-MS for analysis using an online switching valve. The reaction was run while varying the reaction temperature as well as repetition experiments carried out under the same reaction conditions. The data are summarized in Table 2.
Table 2: Ca2Si reaction with MeCI and MeCI + H2
Figure imgf000015_0001
a,b: A combination of MeCI (5sccm) + H2 (5sccm) gaseous mixture was introduced
[0053] 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. [0054] 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 700" may be further delineated into a lower third, i.e., 300 to 433, a middle third, i.e., 434 to 566, and an upper third, i.e., 567 to 700, 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.
[0055] 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

1 . A process for preparing a reaction product comprising a silane product comprises:
(i) contacting an organohalide with a calcium silicide at a temperature from 300 °C to
700 °C to form the reaction product comprising a spent reactant and the silane product, where the silane product has formula RmHnSiX(4-m-n)> where each R is independently a monovalent organic group, each X is independently a halogen atom ; subscript m is 0 to 4; subscript n is 0 to 2; and a quantity (m + n) is 0 to 4; and
where the process further comprises steps (ii) and (iii), where steps (ii) and (iii) are performed separately and consecutively after step (i), and where
step (ii) is contacting, at a temperature from 200 °C to 1400 °C, the spent reactant with a silane of formula HaRbSiX(4_a_b), where subscript a is 0 to 4, subscript b is 0 or 1 , a quantity (a + b) < 4, with the provisos that the silane of formula HaRbSiX(4_a_b) is distinct from the silane product of formula RmHnSiX(4-m-n), and that when the quantity (a + b) < 4, then step (ii) further comprises contacting the spent reactant with H2; thereby forming a reactant, and
step (iii) is contacting the reactant formed in step (ii) with an additional organohalide at a temperature from 300 °C to 700 °C to form an additional silane product of formula RmHnSiX(4-m-n) ; and
where the process optionally further comprises step (iv), where step (iv) is repeating steps (ii) and (iii) at least one time to form a further additional silane product of formula RmHnSiX(4-m-n) ; and
where the process optionally further comprises step (v), where step (v) is recovering the silane product after step (i) and/or step (iii) and/or step (iv).
2. The process of claim 1 , further comprising one or more additional steps, where the one or more additional steps are selected from :
purging the reactor before step (i); and/or
vaporizing the organohalide before step (i); and/or
liquefying the organohalide before step (i); and/or
contacting the calcium silicide with H2 before and/or during step (i) ; and/or purging the reactor before step (ii) ; and/or
purging the reactor before step (iii); and/or
liquefying the organohalide before step (iii); and/or
vaporizing the additional organohalide before step (iii) ; and/or
contacting the reactant with H2 before and/or during step (iii).
3. The process of claim 1 or claim 2, where the temperature in step (i) is 300 °C to 500 °C.
4. The process of any one of the preceding claims, where the calcium silicide is one or more of CaSi2, CaSi, and Ca2Si.
5. The process of any one of the preceding claims further comprising adding a promoter selected from Al, Sn, Zn, P, a compound of Al, a compound of Sn, a compound of Zn, a compound of P, and combinations of two or more of said promoters; during step (i) and/or step (iii).
6. The process of any one of the preceding claims, where the silane has formula
HaRbSiX(4-a-b) > where subscript a is 4, and subscript b is 0.
7. The process of any one of the preceding claims, where one of conditions (a) to (e) is satisfied:
(a) the organohalide has formula RX, where R is an alkyl group or an aryl group, and X is Br or CI; or
(b) the organohalide has formula RX, where R is an alkyl group and X is CI; or (c) the organohalide has formula HeCfXg, where subscript e is 0 or more, subscript f is 1 or more, subscript g is 1 or more, the organohalide is a noncyclic aliphatic hydrocarbyl halide, a quantity (e + g) = a quantity (2f + 2), and each X is independently a halogen atom ; or
(d) the organohalide has formula HeCfXg, where subscript e is 0 or more, subscript f is 1 or more, subscript g is 1 or more, the organohalide is a monocyclic cycloalkyi halide, and the quantity (e + g) = 2f, and each X is independently a halogen atom; or
(e) the organohalide is selected from the group consisting of methyl chloride (H3CCI), methylene chloride (H2CCI2), chloroform (HCCI3), carbon tetrachloride (CCI4), and dichloroethane.
8. The process of any one of the preceding claims, where the silane product has formula RmHnSiX(4-m-n), where subscript m is 1 or 2; subscript n is 0 or 1 ; and the quantity (m + n) is 1 , 2, or 3; and the silane product is not a mixture with the silane of silane of formula HaRbSiX(4-a-b).
9. The process of any one of the preceding claims, where the silane product is a hydridotrihalosilane, and the process further comprises using the hydridotrihalosilane as a reactant in a chemical vapor deposition process for making polycrystalline silicon.
10. The process of any one of claims 1 to 8, where the silane product is a
hydridotrihalosilane, and the process further comprises using the hydridotrihalosilane as a reactant in a hydrolysis process to produce a polysiloxane.
1 1 . The process of any one of claims 1 to 8, where the silane product is a tetrahalosilane, and the process further comprises using the tetrahalosilane as a reactant to make a hydridohalosilane and/or an organohalosilane.
12. The process of any one of claims 1 to 8, where the silane product is a
diorganodihalosilane, and the process further comprises using the diorganodihalosilane as a reactant in a hydrolysis process to produce a polyorganosiloxane.
13. The process of any one of claims 1 to 8, where the silane product is an
organohydridohalosilane, and the process further comprises using the
organohydridohalosilane as a reactant to make a polyorganohydridosiloxane.
14. The process of any one of claims 1 to 7, where the silane product is a
tetraorganosilane, and the process further comprises using the tetraorganosilane as a reactant in a chemical vapor deposition process.
15. A product of the process of any one of claims 8 to 14.
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