Catalytic Conversion of Direct Process High-Boiling Component to Chlorosilane Monomers in the Presence of Hydrogen Chloride

Europaisches Patentamt 19 European Patent Office

Office europeen des brevets © Publication number : 0 635 51 0 A1

12 EUROPEAN PATENT APPLICATION

@ Date of filing : 04.07.94

© Priority : 19.07.93 US 94593 Inventor : Halm, Roland Lee 507 Brentwood Drive Madison, Indiana (US) @ Date of publication of application Inventor : Dhaul, Ajay Kumar 25.01.95 Bulletin 95/04 710 Highland Avenue, Apt.7 @ Designated Contracting States : Carrollton, Kentucky (US) DE FR GB Inventor : Johnson, Richard Gordon Route 2, Box 492-E8 © Applicant : DOW CORNING CORPORATION Hanover, Indiana (US) P.O. Box 994 Midland, Michigan 48686-0994 (US) © Representative : Bullows, Michael Dow Corning Limited, © Inventor : Chadwick, Kirk Michael Cardiff Road 7 Erw'r Delyn Close Barry, South Glamorgan CF63 7YL, Wales (GB) Penarth, South Glamorgan (GB)

© The present invention is a process for converting a high-boiling component resulting from the reaction of an organochloride with silicon into commercially more desirable monosilanes. The process comprises contacting the high-boiling component with hydrogen chloride at a temperature within a range of 250°C. to 1000°C. in the presence of a catalyst selected from activated carbon, platinum supported on alumina, zeolite, AICI3 and AICI3 supported on a support selected from carbon, alumina and silica.

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The present invention is a process for converting ess. a high-boiling component, resulting from the reaction Our process may be run in any standard type re- of an organochloride with silicon, into more commer- actor for contacting silanes and hydrogen chloride. cially desirable monosilanes. The process comprises The process may be run as a batch process, semi- contacting the high-boiling component with hydrogen 5 continuous or continuous process. The process can chloride at a temperature within a range of 250°C. to be run, for example, in a fixed-bed reactor, a stirred- 1000°C. in the presence of a catalyst selected from bed reactor or a fluidized-bed reactor. Preferred is activated carbon, platinum supported on alumina, when the process is run as a continuous process in a zeolite, AICI3 and AICI3 supported on a support select- fluidized-bed reactor. ed from carbon, alumina and silica. 10 This present process is useful for converting a The high- boiling component useful in our process high-boiling component resulting from the reaction of results from a process typically referred to as the "Di- an organochloride with silicon to form monosilanes. rect Process," where an organohalide is reacted with The term "high-boiling component" refers to those silicon in the presence of a suitable catalyst to form materials with a boiling point above that of the diorga- monosilanes. The Direct Process is described more 15 nodichlorosilane formed by the reaction of the orga- fully in US-A 2,380,995 and US-A 2,488,487. It is the nochloride with silicon. For example when methyl main commercial process by which organohalosi- chloride is reacted with silicon, the diorganodichloro- lanes(i.e. monosilanes), for example dimethyldichlor- silane will be dimethyldichlorosilane and the high- osilane and trimethylchlorosilane, are formed. These boiling component will comprise those materials hav- organohalosilanes are reactive compounds which 20 ing a boiling point greaterthan that of dimethyldichlor- can undergo numerous reactions to form a variety of osilane, i.e. greater than 70°C. useful silicon containing compounds and polymers. A In a typical process for reacting an organochlor- major commercial use of organohalosilanes is in the ide with silicon, the reaction is conducted at a temper- production of polysiloxane polymers which are useful ature of 270°C. to 350°C., in the presence of a suit- as heat transfer fluids, lubricants and the like and 25 able catalyst. Gaseous product and unreacted feed which can be further processed, for example, to form are continuously removed from the process. The re- silicone elastomers, resins, sealants and adhesives. moved gaseous product and unreacted feed are sub- Operation of the Direct Process results not only sequently distilled to remove monosilanes leaving in the production of the desirable monosilanes, but behind a high-boiling component. also in a high boiling component typically considered 30 The high-boiling component is a complex mixture to be all materials with a boiling point higher than the that can include compounds containing SiSi, SiOSi, particular diorganodihalosilane produced in the proc- SiCSi, SiCCSi and SiCCCSi linkages alone or in com- ess. The high-boiling component is a complex mix- bination in each molecule. The high-boiling compo- ture that includes compounds containing SiSi, SiOSi, nent can include silicon containing solids and soluble SiCSi, SiCCSi and SiCCCSi linkages in the mole- 35 and insoluble compounds of copper, aluminum and cules. Typical compounds are described in US-A zinc. The high-boiling component may contain, for ex- 2,598,435 and US-A 2,681,355. The high-boiling ample, organic substituted and non-organic substitut- component may also comprise silicon containing sol- ed silanes, disilanes, trisilanes, disiloxanes, silane ids and soluble and insoluble compounds of copper, oligomers, siloxane oligomers, silalkylenes and sili- aluminum and zinc. 40 con containing solids, all of which may be converted In current commercial operations for performing to monosilanes by our process. the Direct Process, the high-boiling component can The present process is especially useful for con- constitute as much as ten percent of the resultant verting polysilanes in the high-boiling component to product. Therefore, it is desirable to convert the high- monosilanes, where the polysilanes are described by boiling component into more commercially desirable 45 formula RaHbSinCI2n+2- a- b and where each R is a rad- products to both reduce low-value by-products and to ical independently selected from alkyls comprising improve raw material utilization. one to six carbon atoms, n = 2 to 20, a = 0 to 2n+2, b The prior art for converting the high-boiling com- = 0 to 2n+2 and a+b = 0 to 2n+2. ponent of the Direct Process into more usable mono- The polysilanes useful in the present process can silanes is represented by US-A 2,598,435; US-A so consist of n number of silicon atoms where n is an in- 2,681,355; US-A2,709,176 and US-A 2,842,580. teger from two to 20. Preferred is when n equals two. The aforementioned problems of the prior art are The polysilanes can be substituted with a=0 to 2n+2 solved by a catalyzed process for the high conversion number of R radicals, where each R is independently of a high-boiling component produced by the Direct selected from alkyls of one to six carbon atoms. The Process to monosilanes. Further, it is unexpected that 55 radical Rcan be methyl, ethyl, propyl and t-butyl. Pre- such a catalyzed process could employ readily avail- ferred is when R is methyl. able and inexpensive catalysts which can be easily The polysilanes in the high-boiling component retained in a reactor and have a long life in said proc- can contain b number of hydrogen atoms substituted 2 3 EP0 635 510 A1 4 on the silicon atoms, where b = 0 to 2n+2. der or pellets. The polysilanes in the high-boiling component In general, it is preferred that the activated carbon can also contain from zero to 2n+2 chlorine atoms. have a diameter within a range of 0.001 mm to 20 mm. The high-boiling component can contain silalky- More preferred is when the activated carbon has a di- lenes, where each silalkylene can comprise one or 5 ameter within a range of 0.01 mm to 5 mm and a sur- more silalkylene bonds described by formula Si(C)zSi face area greater than 1000 m2/g. and z is an integer from one to six. Preferred is when The weight of activated carbon in relation to the z is an integer from one to three. The silalkylene mol- weight of high-boiling componentand hydrogen chlor- ecules can comprise SiSi bonds and SiOSi bonds as ide added to the process will depend upon such fac- well as silalkylene bonds. The silicon atoms of the si- 10 tors as the type and size of the activated carbon, the lalkylene molecules can be further substituted with chemical composition of the high-boiling component, the radical R, where R is as previously described, with the process temperature and the type of reactor em- chlorine and with hydrogen. Preferred is when the sil- ployed. When the process is run as a batch or a semi- icon atoms of the silalkylenes are substituted with continuous process, a useful weight of activated car- methyl. is bon is considered to be within a range of 0.1 to 30 The preferred high-boiling component is one re- weight percent of the combined weight of the high- sulting from the reaction of methyl chloride with silicon, boiling component and the hydrogen chloride added the high-boiling component having a boiling point great- to the process. er than 70°C. This high-boiling component can contain The catalyst can be platinum supported on alumi- Me2CISiSiMe2CI, Me2CISiSiMeCI2, MeCI2SiSiMeCI2, 20 na. The amount of platinum can be from 0.1 to 10 Me2CISiSi(Me)(CI)SiMeCI2, Me2CISiCH2SiMe2CI, weight percent platinum. Preferred is when the Me2 CISiCH2SiMeCI2, MeCI2SiCH2SiMeCI2, Me2CIS amount of platinum is within a range of 0.5 to 2.0 (CH2)2SiMeCI2, Me2CISi(CH2)3SiMeCI2, Me2CISiCH2 weight percent. The concentration of platinum re- Si(Me)(CI)SiMeCI2, Me2CISiCH2Si(Me)(CI)CH2SiMeCI2 tained on an alumina support used in the process will and Me2CISiOSiMeCI2, where Me is methyl, all of 25 depend upon such factors as discussed for the use of which may be converted to monosilanes by the pres- activated carbon. In general, when the process is run ent process. as a batch or semi-continuous process a useful con- The high-boiling component is contacted with hy- centration of platinum on alumina support is consid- drogen chloride, where the ratio of the weight of high- ered to be that which provides a catalyst concentra- boiling component added to the reactor to the weight 30 tion within a range of 0.1 to 30 weight percent of the of hydrogen chloride is within a range of 5:1 to 0.05:1. combined weight of the high-boiling component and Preferred is where the ratio of the weight of high- the halogen chloride added to the process. boiling component to the weight of hydrogen chloride The catalyst can be a zeolite. The zeolite catalyst is within a range of 3:1 to 1:1. can be of the natural occurring type, for example, cha- The process is conducted at a temperature within 35 bazite, mordenite, erionite, faujasite and clinoptilolite. a range of 250°C. to 1 000°C. A preferred temperature The zeolite catalyst can be a synthetic zeolite of the is within a range of 450°C. to 550°C. zeol ite A, X, L or Y types or of the h ig h si lica synthetic While pressure is not critical to the present proc- zeolite types such as ZSM-5 and ZSM-11. Preferred ess, it is preferred that the process be run at a gauge is when the zeolite catalyst is selected from a group pressure within a range of 0 to 6.9 MPa (zero to 1 000 40 of synthetic zeolite catalyst consisting of LZ-Y-64, LZ- psi). More preferred is when the process is run at a Y-74 and LZ-M-8. pressure within a range of 0 to 689.5 kPa (zero psi to The concentration of zeolite catalyst used in the 100 psi). process will depend upon such factors as discussed The process is conducted in the presence of a for the use of activated carbon. In general, when the catalyst selected from activated carbon, platinum 45 process is run as a batch or semi-continuous process, supported on alumina, zeolite, AICI3 and AICI3 sup- a useful concentration of zeolite is considered to be ported on a support selected from carbon, alumina within a range of 0.1 to 30 weight percent of the com- and silica. bined weight of the high-boiling component and the A preferred catalyst is activated carbon. By "acti- hydrogen chloride added to the process. vated carbon", it is meant a microcrystalline, nongra- so The catalyst can be AICI3. The concentration of phite form of carbon, having an internal porosity, the AICI3 catalyst used in the process will depend upon carbon having been activated by any standard proc- such factors as discussed for the use of activated car- ess known in the art for producing activated carbon, bon. In general, when the process is run as a batch for example, chemical activation or gas activation as or semi-continuous process, a useful concentration described in Kirk-Othmer, Concise Encyclopedia of 55 of AICI3 catalyst is considered to be within a range of Chemical Technology, John Wiley & Sons publishers, 0.1 to 30 weight percent of the combined weight of the 1985, p. 204 to 205. The activated carbon can be in high-boiling components and the hydrogen chloride the form of, for example, flakes, chips, particles, pow- added to the process. 3 5 EP0 635 510 A1 6

The catalyst can be AICI3 supported on a support methylchlorodisilanes, disilmethylenes, polysilanes selected from carbon, alumina and silica. The amount and silalkylenes. of AICI3 retained on the support is within a range of 0.1 to 30 weight percent. Preferred is when the amount of Example 2 AICI3 is within a range of 0.5 to 5.0 weight percent. The 5 concentration of supported AICI3 will depend upon Ahigh-boiling component resulting from the reac- such factors as discussed above for the use of acti- tion of methyl chloride with silicon was contacted with vated carbon. In general, when the process is run as hydrogen chloride in the presence of a packed bed of a batch or a semi-continuous process, a useful con- activated carbon catalyst. The process was conduct- centration of supported AICI3 catalyst is considered to 10 ed similar to that described in Example 1, with the be within a range of 0.1 to 30 weight percent of the high-boiling component composition, reactor design combined weight of the high-boiling component and and reaction temperature being the same. The reac- the hydrogen chloride added to the process. tor was packed with 12 g of Calgon™ BPL 1 mm by The optimum contact time for the high-boiling 3.3 mm activated carbon pellets (Calgon, Pittsburgh, component and hydrogen chloride with the catalyst 15 PA). The high-boiling component was fed to the reac- will depend on factors such as the type of catalyst, tor at a rate of 92 g/h and hydrogen chloride was fed chemical composition of the high-boiling component to the reactor at a rate of 57 g/h. Gaseous product ex- and the degree of conversion and product selectivity iting the reactor was collected and analyzed as de- desired. In general, contact times within a range of scribed in Example 1. The collected product was one second to five hours are useful. Longer contact 20 found to comprise 93 weight percent chlorosilane times may be employed, but appear to offer no advan- monomers and included those chlorosilane mono- tage and may result in excessive scission of silicon- mers described for the product of Example 1 . carbon bonds and silicon-hydrogen bonds present in the monosilanes. A preferred contact time in a contin- Example 3 uous reactor system is within a range of one second 25 to five minutes. Ahigh-boiling component resulting from the reac- If desired, the monosilane containing product of tion of methyl chloride with silicon was contacted with the present process can be further separated by stan- hydrogen chloride in the presence of activated carbon dard means, for example, distillation to separate the catalyst in a fluidized-bed reactor. The composition of monosilanes from a high-boiling component and the 30 the high-boiling component, reactor design and proc- high-boiling component can then be recycled to the ess temperature was similar to that described in Ex- process. ample 1. The reactor was filled with 25 g of a 0.1 mm The following examples are provided to facilitate to 0.3 mm pulverized activated carbon (North Ameri- understanding and to demonstrate the effectiveness can, Columbus, OH). The high-boiling component of the present invention. 35 was fed to the reactor at a rate of 75 g/h and hydrogen chloride was fed to the reactor at a rate of 57 g/h. The Example 1 (Not within the scope of the present process was conducted for 24 hours with gaseous invention). product exiting the reactor being collected and analyzed as described in Example 1 . Ahigh-boiling component resulting from the reac- 40 The collected product was determined to consist tion of methyl chloride with silicon was contacted with of similar species as identified in Example 1. Of the hydrogen chloride in the absence of catalyst. The re- product collected, 88 weight percent was chlorosilane actor consisted of a 2.5 cm diameter by 50 cm length monomers. quartz tube maintained at 500°C. The high-boiling component consisted of, by weight, 55% methylchlor- 45 Example 4 odisilane, 5% disilmethylenes, 35% other polysilanes and silalkylenes and 5% silicon containing solids. The Ahigh-boiling component resulting from the reac- high-boiling component was fed at a rate of 117 g/h tion of methyl chloride with silicon was contacted with to the reactor and hydrogen chloride was fed to the re- hydrogen chloride in the presence of a zeolite cata- actor at 50 g/h. The process was conducted for one 50 lyst. The process was conducted similar to that de- hour with gaseous product exiting the reactor being scribed in Example 1, with the high-boiling compo- collected in a cold condenser. The condensed product nent composition, reactor design and reaction tem- was analyzed by gas chromatography using a thermal perature being the same. The reactor was packed conductivity detector (GC-TC) and found to consist of with 15 g of zeolite LZ-Y-74 extruded 1.6 mm pellets 59 weight percent chlorosilane monomers. Chlorosi- 55 (UOP Inc., Tarrytown, NY). The high-boiling compo- lane monomers detected included HSiCI3, SiCI4, nent was fed to the reactor at a rate of 75 g/h and hy- MeHSiCI2, Me3SiCI, MeSiCI3 and Me2SiCI2. Other drogen chloride was fed to the reactor at a rate of 57 species detected in the condensed product included g/h. The process was conducted for one hour with 4 7 EP0 635 510 A1 8 gaseous product exiting the reactor being collected 5. A process according to claim 4 where the high- and analyzed as described in Example 1. boiling component comprises polysilanes descri- The collected product was determined to consist bed by formula RaHbSinCI2n+2-a-b. where each R of similar species as described in Example 1. Of the is a radical independently selected from alkyls product collected, 81 weight percent was chlorosilane 5 comprising one to six carbon atoms, n = 2 to 20, monomers. a = 0 to 2n+2, b = 0 to 2n+2 and a+b = 0 to 2n+2.

Example 5 6. A process according to claim 4, where the high- boiling component comprises silalkylenes which Ahigh-boiling component resulting from the reac- 10 contain one or more silalkylene bonds and are de- tion of methyl chloride with silicon was contacted with scribed by formula Si(C)zSi and z = 1, 2 or 3. hydrogen chloride in the presence of a platinum on alumina. The process was conducted similar to that 7. A process according to claim 1 where the catalyst described in Example 1, with the high-boiling compo- is selected from activated carbon, zeolite LZ-Y- nent composition, reactor design and reaction tem- 15 74 and platinum supported on alumina. perature being the same. The reactor was packed with 16 g of a one weight percent platinum on 1 .6 mm 8. A process according to claim 7 where the catalyst alumina spheres (UOP Inc., Tarrytown, NY). The is activated carbon having a diameter within a high-boiling component was fed to the reactor at a range of 0.01 to 5 mm and a surface area greater rate of 88 g/h and hydrogen chloride was fed to the re- 20 than 1000 m2/g. actor at a rate of 57 g/h. The process was conducted for one hour with gaseous product exiting the reactor collected and analyzed as described in Example 1. The collected product was determined to consist of similar species as described in Example 1. Of the 25 product collected, 82 weight percent was chlorosilane monomers.

Claims 30

1. A process for converting a high-boiling component, resulting from the reaction of an organochloride with silicon, to monosilanes, the process comprising contacting the high-boiling compo- 35 nent with hydrogen chloride at a temperature within a range of 250°C. to 1000°C. in the presence of a catalyst selected from activated carbon, platinum supported on alumina, zeolite, AICI3 and AICI3 supported on a support selected from car- 40 bon, alumina and silica.

2. A process according to claim 1 where the process is conducted at a gauge pressure within a range of 0 to 6.9 MPa (zero to 1 000 psi). 45

3. A process according to claim 1 where the ratio of the weight of the high-boiling component to the weight of the hydrogen chloride added to the process is within a range of 5:1 to 0.05:1. 50

4. A process according to claim 1 where the catalyst is activated carbon and the high-boiling component results from the reaction of methyl chloride with silicon and the high-boiling component com- 55 prises polysilanes, silalkylenes, silicon containing solids and soluble and insoluble compounds of copper, aluminum and zinc. 5 ■ juiuptau i aid it Application Number Office tUKUf tAI'l SEARCH REPORT EP 94 30 4886

LfyjK.uLviiLn ia lurMSiuiLKElJ iu BE RELEVANT BV,J ^ >.«<-iuit vi uvvwikih wun inaicauon, wnere appropriate, Kcicvant t-i-AhsincAiiON of the of relevant passages to claim APPLICATION (lnt.CI.6) n rK-A-i uyj ;>yy (UUW LUKNING CORPORATION) * C07F7/12 the whole document * C07F7/16 D 5, US-A-2 681 355 (BARRY, A.J. ET AL.)

D,A JS-A-2 709 176 (BLUESTEIN, B.A.) * the whole document *

A JS-A-3 432 537 (GUINET, P.A.E. ET AL.) " the whole document *

A EP-A-0 082 969 (DYNAMIT NOBEL AG) " the whole document *

A IP-A-0 537 740 (WACKER-CHEMIE GMBH) * the whole document *

P,X IP-A-0 574 912 (WACKER-CHEMIE GMBH) ' the whole document *

A :P-A-0 155 626 (BAYER AG) ' the whole document * ir.i 1IINK AI. Mr.l.IJM SEARCHED (lnt.CI.6) :07F

|>i^9«.»i. svai vh i^vii ua» uccii utuwd up ror ail claims r.xaMner HE HAGUE I September 1994 inkel, L : ineory or principle underlying the invention : earlier patent document, but published on, or : particularly relevant if taken alone after the filing date : particularly relevant if combined with another ' : document cited in the application document of the same category : document cited for other : technological background reasons 1 : non-written disclosure : member of the same patent family, : intermediate document document corresponding