Catalytic Conversion of Direct Process High-Boiling Component to Chlorosilane Monomers in the Presence of Hydrogen Chloride
Total Page:16
File Type:pdf, Size:1020Kb
Europaisches Patentamt 19 European Patent Office Office europeen des brevets © Publication number : 0 635 51 0 A1 12 EUROPEAN PATENT APPLICATION © Application number : 94304886.8 © int. ci.6: C07F 7/12, C07F 7/16 @ 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) © Catalytic conversion of direct process high-boiling component to chlorosilane monomers in the presence of hydrogen chloride. © The present invention is a process for con- verting a high-boiling component resulting from the reaction of an organochloride with silicon into commercially more desirable mono- silanes. 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 sili- ca. < O In m CO CO LU Jouve, 18, rue Saint-Denis, 75001 PARIS 1 EP0 635 510 A1 2 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.