Patentamt |||| ||| 1 1|| ||| ||| ||| || || || || ||| |||| || JEuropaischesJ European Patent Office Office europeen des brevets (11) EP 0 635 510 B1 (12) EUROPEAN PATENT SPECIFICATION (45) Date of publication and mention (51) Int. CI.6: C07F 7/1 2, C07F7/16 of the grant of the patent: 24.02.1999 Bulletin 1999/08 (21) Application number: 94304886.8 (22) Date of filing: 04.07.1994 (54) Catalytic conversion of direct process high-boiling component to chlorosilane monomers in the presence of hydrogen chloride Katalytische Umsetzung von hochsiedenden RLickstanden der Direktsynthese in Chlorosilanmonomere in Gegenwart von Chlorwasserstoff Conversion catalytique du residu a point d'ebullition eleve obtenu par le procede direct en chlorosilanes monomeres en presence de chlorure d'hydrogene (84) Designated Contracting States: • Dhaul, Ajay Kumar DE FR GB Carrollton, Kentucky (US) • Johnson, Richard Gordon (30) Priority: 19.07.1993 US 94593 Hanover, Indiana (US) (43) Date of publication of application: (74) Representative: 25.01.1995 Bulletin 1995/04 Spott, Gottfried, Dr. et al Patentanwalte (73) Proprietor: Spott, Weinmiller & Partner DOW CORNING CORPORATION Sendlinger-Tor-Platz 11 Midland, Michigan 48686-0994 (US) 80336 Munchen (DE) (72) Inventors: (56) References cited: • Chadwick, Kirk Michael EP-A- 0 082 969 EP-A-0155 626 Penarth, South Glamorgan (GB) EP-A- 0 537 740 EP-A- 0 564 109 • Halm, Roland Lee EP-A- 0 574 912 EP-A- 0 634 417 Madison, Indiana (US) FR-A- 1 093 399 US-A- 2 709 176 US-A- 3 432 537 CO o LO LO CO Note: Within nine months from the publication of the mention of the grant of the European patent, give CO any person may notice to the European Patent Office of opposition to the European patent granted. Notice of opposition shall be filed in o a written reasoned statement. It shall not be deemed to have been filed until the opposition fee has been paid. (Art. Q_ 99(1) European Patent Convention). LU Printed by Xerox (UK) Business Services 2.16.7/3.6 1 EP 0 635 510 B1 2 Description in a reactor and have a long life in said process. [0007] Our process may be run in any standard type [0001 ] The present invention is a process for convert- reactor for contacting silanes and hydrogen chloride. ing a high-boiling component, resulting from the reac- The process may be run as a batch process, semi-con- tion of an organochloride with silicon, into more 5 tinuous or continuous process. The process can be run, commercially desirable monosilanes. The process com- for example, in a fixed-bed reactor, a stirred-bed reactor prises contacting the high-boiling component with or a f luidized-bed reactor. Preferred is when the process hydrogen chloride at a temperature within a range of is run as a continuous process in a fluidized-bed reac- 250°C. to 1 000°C. in the presence of a catalyst selected tor. from platinum supported on alumina, zeolite, AICI3 and 10 [0008] This present process is useful for converting a AICI3 supported on a support selected from carbon, alu- high-boiling component resulting from the reaction of an mina and silica. organochloride with silicon to form monosilanes. The [0002] The high-boiling component useful in our proc- term "high-boiling component" refers to those materials ess results from a process typically referred to as the with a boiling point above that of the diorganodichlorosi- "Direct Process," where an organohalide is reacted with is lane formed by the reaction of the organochloride with silicon in the presence of a suitable catalyst to form silicon. For example when methyl chloride is reacted monosilanes. The Direct Process is described more with silicon, the diorganodichlorosilane will be dimethyl- fully in US-A 2,380,995 and US-A 2,488,487. It is the dichlorosilane and the high-boiling component will com- main commercial process by which organohalosilanes prise those materials having a boiling point greater than (i.e. monosilanes), for example dimethyldichlorosilane 20 that of dimethyldichlorosilane, i.e. greater than 70°C. and trimethylchlorosilane, are formed. These organoha- [0009] In a typical process for reacting an organochlo- losilanes are reactive compounds which can undergo ride with silicon, the reaction is conducted at a tempera- numerous reactions to form a variety of useful silicon ture of 270°C. to 350°C., in the presence of a suitable containing compounds and polymers. A major commer- catalyst. Gaseous product and unreacted feed are con- cial use of organohalosilanes is in the production of 25 tinuously removed from the process. The removed gas- polysiloxane polymers which are useful as heat transfer eous product and unreacted feed are subsequently fluids, lubricants and the like and which can be further distilled to remove monosilanes leaving behind a high- processed, for example, to form silicone elastomers, boiling component. resins, sealants and adhesives. [0010] The high-boiling component is a complex mix- [0003] Operation of the Direct Process results not only 30 ture that can include compounds containing SiSi, SiOSi, in the production of the desirable monosilanes, but also SiCSi, SiCCSi and SiCCCSi linkages alone or in combi- in a high boiling component typically considered to be nation in each molecule. The high-boiling component all materials with a boiling point higher than the particu- can include silicon containing solids and soluble and lar diorganodihalosilane produced in the process. The insoluble compounds of copper, aluminum and zinc. high-boiling component is a complex mixture that 35 The high-boiling component may contain, for example, includes compounds containing SiSi, SiOSi, SiCSi, organic substituted and non-organic substituted silanes, SiCCSi and SiCCCSi linkages in the molecules. Typical disilanes, trisilanes, disiloxanes, silane oligomers, compounds are described in US-A 2,598,435 and US-A siloxane oligomers, silalkylenes and silicon containing 2,681 ,355. The high-boiling component may also com- solids, all of which may be converted to monosilanes by prise silicon containing solids and soluble and insoluble 40 our process. compounds of copper, aluminum and zinc. [0011] The present process is especially useful for [0004] In current commercial operations for perform- converting polysilanes in the high-boiling component to ing the Direct Process, the high-boiling component can monosilanes, where the polysilanes are described by constitute as much as ten percent of the resultant prod- formula RaHbSinCI2n+2-a-b anc) where each R is a radi- uct. Therefore, it is desirable to convert the high-boiling 45 cal independently selected from alkyls comprising one component into more commercially desirable products to six carbon atoms, n = 2 to 20, a = 0 to 2n+2, b = 0 to to both reduce low-value by-products and to improve 2n+2 and a+b = 0 to 2n+2. raw material utilization. [001 2] The polysilanes useful in the present process [0005] The prior art for converting the high-boiling can consist of n number of silicon atoms where n is an component of the Direct Process into more usable mon- so integer from two to 20. Preferred is when n equals two. osilanes is represented by US-A 2,598,435; US-A The polysilanes can be substituted with a=0 to 2n+2 2,681,355; US-A 2,709,176 and US-A 2,842,580. number of R radicals, where each R is independently [0006] The aforementioned problems of the prior art selected from alkyls of one to six carbon atoms. The are solved by a catalyzed process for the high conver- radical R can be methyl, ethyl, propyl and t-butyl. Pre- sion of a high-boiling component produced by the Direct 55 ferred is when R is methyl. Process to monosilanes. Further, it is unexpected that [0013] The polysilanes in the high-boiling component such a catalyzed process could employ readily available can contain b number of hydrogen atoms substituted on and inexpensive catalysts which can be easily retained the silicon atoms, where b = 0 to 2n+2. 2 3 EP 0 635 510 B1 4 [0014] The polysilanes in the high-boiling component [0022] In general, it is preferred that the activated car- can also contain from zero to 2n+2 chlorine atoms. bon have a diameter within a range of 0.001 mm to 20 [001 5] The high-boiling component can contain silalk- mm. More preferred is when the activated carbon has a ylenes, where each silalkylene can comprise one or diameter within a range of 0.01 mm to 5 mm and a sur- more silalkylene bonds described by formula Si(C)zSi 5 face area greater than 1000 m2/g. and z is an integer from one to six. Preferred is when z [0023] The weight of activated carbon in relation to the is an integer from one to three. The silalkylene mole- weight of high-boiling component and hydrogen chlo- cules can comprise SiSi bonds and SiOSi bonds as well ride added to the process will depend upon such factors as silalkylene bonds. The silicon atoms of the sila- as the type and size of the activated carbon, the chemi- lkylene molecules can be further substituted with the 10 cal composition of the high-boiling component, the proc- radical R, where R is as previously described, with chlo- ess temperature and the type of reactor employed. rine and with hydrogen. Preferred is when the silicon When the process is run as a batch or a semi-continu- atoms of the silalkylenes are substituted with methyl. ous process, a useful weight of activated carbon is con- [0016] The preferred high-boiling component is one sidered to be within a range of 0.1 to 30 weight percent resulting from the reaction of methyl chloride with sili- 15 of the combined weight of the high-boiling component con, the high-boiling component having a boiling point and the hydrogen chloride added to the process.