Chlorosilane Disproportionation Catalyst and Method for Producing a Silane Compound by Means of the Catalyst

Home , Chlorosilane, Dichlorosilane, Hydrogen chloride, Silane, Trichlorosilane

turopaiscnes patentamt European Patent Office © Publication number: 0 213 215 Office europeen des brevets A1

EUROPEAN PATENT APPLICATION

Application number: 85110110.5 C01B © Int. CI.4: 33/107 , C01 B 33/04 , ~ B01J 31/02 © Date of filing: 12.0&85

© Date of publication of application: © Applicant: DENKI KAGAKU KOGYO KABUSHIKI 11.03.87 Bulletin 87/11 KAISHA 4-1, Yuraku-cho 1-chome © Designated Contracting States: Chiyoda-ku Tokyo(JP) BE CH GB IT LI NL © Inventor: Yamada, Mitsunori 55-1, Oaza-Suzawa Oml-machi Nishi-Kubiki-gun Niigata-ken(JP) Inventor: Ishii, Masaji 4- 33-4-302, Tsurumaki Setagaya-ku Tokyo(JP) inventor: Miyai, Akira 1964-5, Yamazaki-machi Mashida-shi Tokyo(JP) Inventor: Nakajima, Yukihlko 5- 33-18, Asahi-machl Atsugishi Kanagawa-ken(JP) Inventor: Sato, Shinsei 3-5-22, Mlnami-Rlnkan Yamato-shi Kanagawa-ken(JP)

*) Chlorosilane disproportionation catalyst and method for producing a silane compound by means of the catalyst

(57/ A chlorosilane disproportionation catalyst comprising a tertiary amine of the formula:

5 R^ » N-R (A) R N

£2 where each R represents an aliphatic hydrocarbon N group and the sum of carbon atoms in the three aliphatic hydrocarbon groups as R is 12 or more, and a tertiary amine hydrochloride of the formula: EL LU

arox uopy centre 0 213 215

R\ + - N-RH CI (B)

where R is as defined above.

2 U 213 215 2

CHLOROSILANE DISPROPORTIONATION CATALYST AND METHOD FOR PRODUCING A SILANE COM- POUND BY MEANS OF THE CATALYST

as taught in U.S. Patent No. 2,732,282 has to be onv^iwanuuiNU ur I HE IINVCIN I IUIN conducted at a reaction temperature of 150°C and above; (ii) the method of using aliphatic FIELD OF THE INVENTION cyanamides as taught in U.S. Patent No. 2,732,280 5 requires the pretreatment with a Lewis acid; (iii) the The present invention relates to a chlorosilane method of using dimethylformamide or dimethyl- disproportionation catalyst and a method for pro- butylamide as taught in U.S. Patent No. 3,222,511 ducing a silane compound by means of the cata- is liable to deteriorate the catalyst used for the More lyst. particularly, the present invention relates reaction; and (iv) the method of using a tertiary to a chlorosilane disproportionation catalyst com- to amine containing a hydrocarbon composed of an prising a specific tertiary amine and a hydrochlo- alkyl group with 1 or 2 carbon atoms, as taught in ride thereof as the main components, and a meth- U.S. Patent No. 2,834,648 is required to be con- od for continuously producing a silane compound ducted at a temperature of 150 8 C and above, as is such as dichlorosilane, monochlorosilane or mon- the case with the catalyst of the above-mentioned Dsilane, by supplying a starting material 75 method (i), besides which a pressure resistant ves- chlorosilane and the catalyst into a reaction tower, sel has to be used, and, in spite of its equilibrated whereby the disproportionation reaction by means conversion ratio (calculated value) being 18% at 3f the specific catalyst and the separation by dis- the reaction temperature of 150" C, the actual con- tillation are conducted simultaneously. Further, the version ratio is as low as about 10%, hence a large Dresent invention relates to a process for producing 20 size apparatus is required to attain a desired quan- a silane compound efficiently by combining a pro- tity of production. :ess for synthesizing trichlorosilane from silicon of Further, U.S. Patent No. 4,113,845 discloses metallurgical grade or silicon tetrachloride, with the use of a fixed bed type reactor packed with an above method for producing a silane compound. anion exchange resin containing a tertiary amine as 25 the catalyst, wherein a starting material chlorosilane such as trichlorosilane or dichlorosilane is supplied DESCRIPTION OF THE PRIOR ART in a liquid state from one port of the reactor and reacted at a temperature of from 30 to 200 °C Demands for silane compounds such as dich- under a pressure of from 1 to 30 atm, whereby a orosilane (SiH,CI,), monochlorosilane (SiH,CI) and 30 reaction product comprising monosilane, monoch- nonosilane (SiH«) are expected to increase more lorosilane, dichlorosilane, trichlorosilane and silicon ind more as they are useful as the raw materials tetrachloride is obtainable from the other port of the or the high silicon purity to be used for elements reactor. However, since the above-mentioned equa- or semiconductors, solar cells, etc. In particular, it tions (1), (2) and (3) for the disproportionation reac- been las desired that dichlorosilane and mon- ts tion are equilibrium reactions, it is not possible to >silane be produced efficiently and in a large quan- complete the reaction of the starting material ity. chlorosilane 100%, even if the reaction is con- It is known to obtain a silane by the dispropor- ducted for an extended period of time. For exam- ionation reaction of SiHCI3 in the presence of a ple, the following Table indicates the equilibrated :atalyst, in accordance with the following equilib- to composition of monosilane, monochlorosilane, dich- ium reactions. lorosilane, trichlorosilane and silicon tetrachloride at (1) 2SiHCI3ssSiH,Cls + SiCI. a temperature of 80 °C when the disproportionation (2) 2SiH2CI,5* SiHCI, + SiH3CI reaction of trichlorosilane or dichlorosilane as the (3) 2SiH,CI s* SiH4 + SiH2CI, starting material has reached the state of equilib- (4) 4SiHCI3 » SiH, + 3SiCI, (as a whole) « rium. The disproportionation of chlorosilanes has »een studied since old, and various proposals have teen made. However, they still have disadvan- ages. For example, (i) the method of using nitrites 3 0 213 215 '4

(mol %) Starting Mono- Tri- Silicon material Mono- chloro- Dichloro- chloro- tetra- chlorosilane silane silane silane chloride silane

Trichloro- 0.04 0.52 10.6 ' 77.1 11.8 silane

Dichloro- 10.2 15.6 38.8 34.7 0.65 silane

Further, even when the disproportionation reac- proportionation reaction. Thus, they are hardly ap- tion is brought to the equilibrated condition by 75 plicable to a practical operation on an industrial using trichlorosilane as the starting material, mon- scale. osilane and monochlorosilane contained in the reaction product are 0.04 mol % and 0.52 mol %, respectively, which figures indicate a very low re- SUMMARY OF THE INVENTION action rate for producing monosilane or monoch- 20 lorosilane in a single stage reaction. Therefore, It is an object of the present invention to pro- when, for example, monosilane is produced by vide a chlorosilane disproportionation catalyst using trichlorosilane as the starting material, the whereby a disproportionation reaction can be com- reaction product from the reaction vessel at the pleted in a short period of time at a low tempera- first stage is charged in a distilling device to sepa- 25 ture with a high conversion, by using a specific rate a mixture containing therein monosilane, mon- tertiary amine and a hydrochloride thereof as the ochlorosilane, and dichlorosilane, wherein dich- disproportionation catalyst. lorosilane is the principal component (composition A second object of the present invention is to A) and a mixture of trichlorosilane and silicon tetra- provide a method for continuously producing a chloride (composition B), and then the composition 30 silane compound such as monosilane, monoch- A is fed into the reaction vessel at the second lorosilane or dichlorosilane from a starting material stage, whereupon, since the equilibrated composi- chlorosilane such as trichlorosilane. tion from the disproportionation reaction contains A third object of the present invention is to 10.2 mol % of monosilane, as is apparent from the reuse silicon tetrachloride formed as a by-product table, monosilane can be separated and recovered 35 by the disproportionation reaction. As shown in the by feeding this reaction product into the distilling foregoing equation (4), when 1 mol of SiH« is apparatus. However, since the rate of reaction in produced by the disproportionation reaction, 3 mol the disproportionation reaction is low, the unreacted of SiCU is obtained as a by-product. In terms of substance should be circulated in a large quantity weight, 17 kg of SiCU is produced with respect to 1 for use, with the consequence that enormous 40 kg of SiH,. When SiH, is to be obtained in a large amount of energy was disadvantageous^ required quantity and at a low cost, this by-product SiCU is for the operations of the reaction vessel and the required to be re-used. distilling tower. Heretofore, in the method of using an ion- Furthermore, N-methyl-2-pyrrolidone, exchange resin, the by-product SiCU is introduced methylimidazole, tetramethylurea, tetramethyl- 45 into a reaction system consisting of silicon of met- guanidine, trimethylsilylimidazole, benzothiazole, allurgical grade, hydrogen, and hydrogen chloride, N,N-dimethylacetamide and the like, as disclosed then treated at a temperature of 600°C or so, and e.g. U.S. Patents No. 4,018,871 and 4,038,371 or re-converted to trichlorosilane (SiHCU). However, as Japanese Unexamined Patent Publication No. described in the foregoing, since the reaction rate 17918/1981, exhibit catalytic activities in the dis- 50 in the disproportionation reaction is low, a large proportionation reaction of silane compounds. How- amount of unreacted substance needs to be used ever, they are per se solid, or become powdery by recycling, on account of which the reaction solid when brought in contact with a silane com- vessel and the distilling apparatus should be made pound such as trichlorosilane or dichlorosilane. large in scale. Thus, an enormous amount of en- Consequently, it becomes difficult to separate them 55 ergy is disadvantageously required. from the silane compound produced by the dis-

4 5 0 213 215 6

That is to say, the third object of the present method according to the second object of the invention is to provide an integral process with the present invention which is excellent in the rate of least amount of recycling of the unreacted sub- disproportionation reaction, including the re-use of stance and less energy consumption by use of the SiCU as a by-product. Namely, the present invention provides' a chlorosilane disproportionation catalyst comprising a tertiary amine of the formula:

N-R (A)

wnere eacn r. an represents aliphatic hydrocarbon 75 group and the sum of carbon atoms in the three aliphatic hydrocarbon groups as R is 12 or more, and a tertiary amine hydrochloride of the formula:

"\ + - .N-RH CI (B)

wnere i-i is as aennea aoove. Figures 3 and 4 are schematic diagrams Further, the present invention provides a meth- illustrating the processes for the production of the od for continuously producing a silane compound starting materials according to the Examples of the such as monosilane or dichlorosilane by the dis- present invention. proportionation reaction of a starting material chlorosilane such as trichlorosilane, which comprises: DETAILED DESCRIPTION OF THE INVENTION a) supplying the starting material chlorosilane and the above-mentioned chlorosilane In the present invention, the chlorosilane is at disproportionation catalyst into reaction tower a 30 least one chlorosilane selected from SiHCI,, SiH2CI, having a distilling function; and SiH3CI. b) obtaining, from the top of the tower, a The reason why the sum of carbon atoms in silane compound containing more hydrogen atoms the aliphatic hydrocarbon groups as R is limited to than the starting material chlorosilane; 12 or more in the present invention is that when a c) withdrawing, from the bottom of the tower, tertiary amine having less than 12 carbon atoms is a liquid mixture comprising the catalyst and silane added to the chlorosilane, white solid will form and compounds containing more chlorine atoms as by- it becomes impossible to conduct the reaction in a products; uniform liquid phase, and as will be apparent from d) separating the silane compounds and the Examples given hereinafter, the tertiary amine hav- catalyst in the liquid mixture; and less than «o ing 12 carbon atoms is inferior in the e) recycling the separated catalyst to the disproportionation reaction rate to the one having reaction tower. 12 or more carbon atoms. There is no particular restriction as to the upper limit of the sum of carbon atoms. However, from the viewpoints of the bHIfcr UbSUHIPTION Or THE DRAWINGS performance and costs, the sum of carbon atoms is preferably from 12 to 36. 1 Figure is a schematic diagram illustrating As the compound of the formula (A), there may an apparatus used for the production of silane be mentioned tri-n-butylamine, tri-n-pentylamine, compounds as described in Examples. tri-n-hexyiamine, tri-n-heptylamine, tri-n-octylamine, Figures 2 is a schematic diagram illustrating 35 tri-n-decylamine and tri-n-dodecylamine. the process for the preparation of the starting material according to a Comparative Example. 7 0 213 215 8

The compound of the formula (B)-is a hy- (5) Since the reaction system is a uniform drochloride of the compound represented by the liquid phase system, there is no necessity for agi- formula (A) and is usually readily obtained by add- tation and other homogenizing operations. Thus, ing hydrochloric acid or -hydrogen chloride gas to a the transportation and various handling of the cata- solutiorTof the above-mentioned tertiary amine. 5 lyst become advantageously simple. There are of When the compounds of the formulas (A) and - course various advantages besides the above. (B) are to be used as a catalyst, the tertiary amine Now, the method for the disproportipnation of a and its hydrochloride are preferably used in such chlorosilane by means of the catalyst of the proportions that the former constitutes from 20 to present invention will be described. Conventional 98 mol % and the latter constitutes from 2 to 80 to methods may be employed for the production of mol %. If the latter is less than 2 mol %, the silane compounds such as SiH2CI2 and SiH, by the catalytic activity is weak, and if the latter exceeds disproportionation reaction by means of the cata- 80 mol %, hydrochloric acid is likely to be freed lyst of the present invention. For instance, there during the reaction, thus leading to the following may be employed a series of operations which reactions, whereby it becomes difficult to obtain the 75 comprises mixing the chlorosilane and the catalyst, desired silane compound having a greater number subjecting the mixture to the disproportionation re- of hydrogen atoms efficiently. action, and separating the resulting silane com- SiH, + HCI - SiH3CI + H2 pounds such as SiH2CI2 and SiH. by condensation or distillation. These operations may be carried out SiH,CI + HCI- SiH2CI2 + H2 20 simultaneously. Namely, the disproportionation and/or redistribution of the present invention may SiH2CI2 + HCI- SiHCI, + H2 be conducted by contacting the chlorosilane with the catalyst of the present invention. The reaction SiHCU + HCI- SiCU + H2 is conducted preferably at a temperature of from It is particularly preferred that the catalyst com- 25 10 to 300°C, more preferably from 20 to 150"C. prises from 70 to 90 mol % of the tertiary amine of To activate and reuse the used catalyst, it is the formula (A) and from 10 to 30 mol % of the desirable to add at least one of hydrogen chloride tertiary amine hydrochloride of the formula (B). gas, hydrochloric acid and water, to the used cata- The catalyst is used preferably in an amount of lyst. Hydrogen chloride, hydrochloric acid or water from 2 to 50 mol % relative to the starting material 30 may be added to a recycling line for the catalyst or chlorosilane. directly to the reaction tower. Further, in the case A particularly preferred catalyst comprises from of hydrogen chloride, it may be added to the line 70 to 90 mol % of tri-n-butylamine and/or tri-n- for supplying the starting material chlorosilane to octylamine, and from 10 to 30 mol % of tri-n- the reaction tower. butylamine hydrochloride and/or tri-n-octyiamine 35 The disproportionation may be conducted in a hydrochloride. batch system or in a continuous system. However, According to the present invention as de- the following continuous method is preferred. scribed in the foregoing, the following effects will In the method for continuously producing a be obtained. silane compound such as monosilane or dich- (1 ) The catalyst of the present invention pro- 40 lorosilane by the disproportionation reaction of a vides a conversion which is closer to the equili- starting material chlorosilane such as trich- brated conversion, at a temperature of less than lorosilane, the above-mentioned catalyst of the 150°C in comparison with the conventional cata- present invention and the starting material lyst. chlorosilane were supplied to a reaction tower hav- (2) When the catalyst of the present inven- 45 ing a distilling function; a silane compound contain- tion is used, the equilibrated conversion is reached ing more hydrogen atoms than the starting material in a short period of time, which means a high chlorosilane is obtained from the top of the tower, disproportionation velocity, and which makes it while a liquid mixture comprising the catalyst and possible to reduce the size of the reaction appara- by-product silane compounds containing more tus. so chlorine atoms, is withdrawn from the bottom of the (3) The catalyst according to the present reaction tower; then, the silane compounds and the invention is completely soluble in the chlorosilane catalyst in the above-mentioned liquid mixture, are starting material, and also has a boiling point of separated; and the separated catalyst is then re- 200°C and above. Accordingly, it serves to lower cycled to the reaction tower. the vapor pressure in the reaction liquid, and ad- 55 In this method, the reason why the sum of vantageously contributes to safety in the operation. • carbon atoms in the three aliphatic hydrocarbon (4) The catalyst can be readily separated groups as R of the catalyst is limited to 12 or more, from the reaction product such as SiH2CI2 or SiH«. is that compounds containing less than 12 carbon

6 a 0 213 215 10

atoms are unaesiraoie since tney are iiKeiy to torm temperature to the above-mentioned range, the solid substances when contacted with a silane gauge pressure Is usually maintained at a level of compound such as trichlorosilane, dichlorosilane or from 0 to 40 kg/cms, preferably from 0 to 20 silicon tetrachloride, although they have catalytic kg/cm2. activities. Namely, the reaction tower to be used in 5 When the disproportionation reaction of the the present invention is a trays tower or a packed starting material chlorosilane is conducted in the tower having a distilling function. Accordingly, the presence of the catalyst in the reaction tower hav- solid substances are likely to clog the plates or the ing the distilling function, the above-mentioned dis- packing materials, whereby smooth continuous op- proportionation reactions (1), (2) and (3) proceed eration can hardly be conducted. io simultaneously, whereby monosilane, monoch- The sum of carbon atoms in the three aliphatic lorosilane, dichlorosilane, trichlorosilane and silicon hydrocarbon groups as R of the catalyst is prefer- tetrachloride will be formed. Their boiling points are ably from 12 to 36. A preferred catalyst comprises -118°C, -30°C, 8°C, 32°C and 56°C, respectively. tri-n-butylamine and/or tri-n-octylamine. The most Further, since the reaction tower per se has the preferred catalyst is the one obtained by adding at 75 distilling function, there will be a concentration dis- least one member selected from the group consist- tribution from the top of the tower in the sequence ing of hydrogen chloride gas, hydrochloric acid and of monosilane, monochlorosilane, dichlorosilane, water, to tri-n-butylamine and/or tri-n-octylamine. trichlorosilane and silicon tetrachloride. The amount of the addition is adjusted to bring the Now, the method for the production of a silane hydrochloride concentration in the catalyst to a 20 compound according to the present invention will level of from 2 to 80 mol %, preferably from 10 to be described with reference to the drawings. 30 mol %. Figure 1 is a schematic diagram illustrating the The catalyst is used preferably in an amount of apparatus to be used in Examples of the present from 2 to 50 mol %, more preferably from 5 to 40 invention. The starting material chlorosilane such mol % relative to the starting material chlorosilane. ?5 as trichlorosilane or dichlorosilane is supplied to an Now, the reaction tower to be used in the upper portion of the reaction tower 1 via a starting present invention will be described. The reaction material supply line 4. The reaction tower 1 is a tower is of a distillation tower type. For instance, it stainless steel distilling tower having a diameter of is a plate tower with its interior being partitioned by 83 mm and a height of 2000 mm with 18 stages. sieve trays or bubble cap trays, or a packed tower io Each tray is a sieve tray having 37 perforations with its interior filled with packing material such as with a diameter of 1.5 mm. Above the tower 1, a Raschig rings or pall rings. While the reaction condenser 3 made of stainless steel is provided, tower may be of any structure, provided that it has which is adapted to be cooled by circulating a distillation function, the more desirable is a reac- methanol dry ice in a jacket. At the lower portion of tion tower having a large liquid hold-up capacity, )5 the reaction tower 1, a reboiler 2 equipped with a because the disproportionation reaction of the heater having a maximum output power of 1 KW is silane compound according to the present inven- provided. tion is conducted in a liquid phase. In the reaction In the reaction tower 1, separation by distilla- tower according to the present invention, the sepa- tion takes place simultaneously with the dispropor- ■ation by distillation of the reaction product is car- (0 tionation reaction, whereby the gas rich in the low ied out simultaneously with the reaction, and ac- boiling point components formed by the dispropor- :ordingiy the temperature at the top of the reaction tionation reaction moves upward and cooled by the :ower is low, while the temperature at the bottom of condenser 3, whereby the accompanying high boil- tie tower is high. Thus, a temperature gradient is ing point components will be condensed. The low produced within the reaction tower, whereby the « boiling point components will then be condensed eaction temperature is not constant. However, the by a condenser 6 made of stainless steel and eaction is usually conducted at a temperature of cooled with liquid nitrogen, and recovered in a rom 10 to 300 °C, preferably from 20 to 150QC. If liquid state in a collecting tank 7. he temperature is less than 10°C, the reaction rate On the other hand, the high boiling point com- s low, and the disproportionation reaction does not o ponents such as trichlorosilane and silicon tetra- substantially proceed. On the other hand, if the chloride formed by the disproportionation reaction, emperature exceeds 300°C, the thermal decompo- will move to the bottom of the tower, and will then sition of the cataiyt is likely to take place, such be withdrawn together with the catalyst to the evap- )eing undesirable. The reaction is conducted in a oration tank 9 while the liquid level is controlled by wiling state, and in order to keep the reaction 5 the reboiler 2. The evaporation tank 9 is a stainless steel vessel having an internal capacity of 3 liters and equipped with an agitator. A jacket is provided thereon, and a heating oil is circulated in the jacket 11 0 213 215 12 to heat the evaporation tank. This evaporation tank distilling tower 41 is mainly SiHCU which is intro- 9 is operated at a temperature which is higher than duced into a reaction tower 43 which carries out the boiling point of silicon tetrachloride formed by the third step of the reaction and in which the the disproportionation reaction and lower than the tertiary amine and its hydrochloride are present as boiling point of the catalyst. Trichlorosilane and 5 the catalyst. From the top of this tower 43, a silicon tetrachloride withdrawn from the reboiler 2 mixture of silanes 49 consisting principally of SiH, are evaporated, collected in a condenser 1 1 cooled is taken out, and forwarded to a silane distilling with methanol dry ice, and recovered in a tank 12. tower 42 to carry out the fifth step of the distillation, The catalyst remaining in the evaporation tank 9 is from which SiH, as the end product is taken out as withdrawn by a pump 10 and recycled to the top of io the tower top component. the reaction tower 1. If necessary, at least one of On the other hand, the high boiling point com- hydrogen chloride gas, hydrochloric acid and water ponent in the silane distilling tower 42 is returned is supplemented via any one of supply lines 13 to to the reaction and distilling tower 43. Since the 16. high boiling point component in the reaction tower For the purpose of the comparison, Figure 2 75 contains a mixture of silanes with SiHCU and SiCU illustrates a conventional disproportionation method as the principal components as well as the catalyst, wherein an ion exchange resin is employed. Refer- this high boiling point component is introduced into ring to Figure 2, reference numeral 20 designates a a distilling vessel 52 to carry out the fourth step of trichlorosilane synthesizing tower, from which pro- the separation where the mixture of silanes and the duced gas 26, consisting principally of SiHCIj and 20 catalyst are separated. The catalyst 48 is returned SiCU, enters into the subsequent distilling tower 21 . to the reaction tower 43, while the mixture of The principal components of the gas at the top part silanes is recycled to the distilling tower 41 . SiCU is of the distilling tower are SiHCU and SiH2CI2 which sent back to the trichlorosilane synthesizing vessel enter further into the subsequent distilling tower 22. 40. On the other hand, SiHCU is taken out of the 25 Thus, the present invention suffices with a sin- bottom part 31 of the distilling tower 22, then gle unit of the reaction tower and two units of the introduced into a disproportionation tower 24 filled distilling tower, and the total process steps can be with an ion-exchange resin, and disproportionated. five, even inclusive of. the trichlorosilane synthesiz- The disproportionated mixture of silanes enters into ing vessel and the evaporator, hence the method of the distilling tower 21, from the bottom part 30 of 30 the present invention provides a simplified process which a high boiling point substance of SiCU is in comparison with the conventional method. taken out and sent back to the trichlorosilane syn- The operating conditions at each process step thesizing tower 20. are as follows: the first step is conducted at the On the other hand, SiH2CI2 as the principal operating temperature of from 400 to 700 °C under component at the top part of the distilling tower 22 35 a pressure range of from zero to 30 kg/cm2G; the enters into a disproportionation tower 25 filled with second step is carried out under a pressure in a an ion-exchange resin. The silane compound as range of from zero to 2 kg/cm2G; the third step is disproportionated therein is then introduced into a carried out at a temperature in a range of from zero silane distilling tower 23, from the top 29 of which to 300 °C under a pressure range of from zero to SiH, is taken out. A high boiling point component 40 40 kg/cm2G; the fourth step is done at a tempera- from the bottom 32 of the distilling tower 23 is ture in a range of from 70 to 200°C under a returned to the distilling tower 22. pressure range of from zero to 4 kg/cm2G; and the As described in the above, the conventional fifth step is conducted at a temperature in a range disproportionation process required two units of of. from -10 to -40°C under a pressure range of disproportionation tower and three units of the dis- 45 from 15 to 40 kg/cm2G, although such temperature tilling tower, the total process steps for the reaction and pressure conditions depend also on the purity being six, including the synthesis of trichlorosilane. of SiH, as the ultimate product. In the following, explanations will be given in As will be described in Examples, the present reference to Figure 3 as to the disproportionation invention provide-; a high rate of disproportionation reaction according to the present invention. Refer- 50 reaction, besides the afore-described various ef- ring to the flow chart in Figure 3, a reference fects, hence the recycling quantity of the unreacted numeral 40 designates a trichlorosilane synthesiz- substances becomes decreased with the conse- ing vessel to. carry out the first step of the hy- quent reduction in size of the distilling tower and, drogenation reaction according to the present in- further, least utility, and other advantages. vention. Produced gas 44 contains SiHCU and SiCU 55 as the principal components which are sent into a distilling tower 41 to carry out the second step of the distillation. The component at the top of the

8 13 0 213 215 14

in me roregoing explanations ot tne present metically sealed condition by varying the reaction invention, there has been shown a process of ob- temperature, and the kind and amount of the cata- taining SiH« as the end product. It should however lyst, as shown in Table 1 below. The quantity of be noted that the same effect as mentioned above the chlorosilane in the gas phase was quantitatively can be obtained in the case of taking out SiH2CI2 as 5 measured by gas chromatography time-sequential- the end product. ly. The amount of the hydrochloride in each case In the trichlorosilane synthesizing vessel in the was 20 mol % relative to the tertiary amine. The first step, trichlorosilane is prepared from silicon of hydrochloride was formed by introducing the terti- metallurgical grade as a starting material. Instead ary amine into the autoclave and then blowing HCI of this process, there may be employed a process to thereinto. A change in the quantity of SiHCIi in the as shown in Figure 4 wherein silica, carbon and gas phase corresponds to its conversion ratio, and chlorine as starting materials are reacted at a high Table 1 below indicates the time until the con- temperature in a silicon tetrachloride synthesizing centration of SiHCIj takes a constant value and the furnace to produce silicon tetrachloride, and the concentrations of SiHCIj and SiCU at that time. silicon tetrachloride thus obtained is purified in a 75 Table 1 shows that the shorter the time is, the low boiling component removal tower B and a high faster is the conversion velocity (i.e. dispropor- boiling component removal tower C, then intro- tionation velocity), and the lower the concentration duced into a trichlorosilane synthesizing tower D value of SiHCI, is, the better becomes the conver- and converted to trichlorosilane by reduction with sion. Also, in Table 1 below, the equilibrated con- hydrogen. This method is advantageous in the 20 centration of SiHCIj obtained by calculation is case where silane gas is produced in a large shown as a reference. amount, since the power consumption is thereby For the purpose of comparison, under the essentially small, and the cost for the operation is same conditions as in Example 1 above, the dis- low. Here, the synthesis of silicon tetrachloride is proportionation reactions were carried out by using conducted usually at a temperature of from 1 100 to 25 trimethylamine, triethylamine, trirn-propylamine, 1400°C in a reaction system such as a fixed bed trimethylamine hydrochloride, and triethylamine hy- system, a transfer bed system or a fluidized bed drochloride as the catalysts, at the reaction tem- system. Further, when silicon carbide is added to peratures of 25° C, 50° C, and 1008C, respectively. the starting material as a catalyst in an amount of The results are shown in Table 1 below - from 1 to 10% by weight, the reaction rate is jo (experiments No. 20 -No. 30). The catalysts were improved. Further, from the viewpoint of the effi- present as solid substance in the reaction liquid, ciency of energy, the synthesis of trichlorosilane by and the agitator was employed for sufficient disper- reduction with hydrogen is advantageously con- sion of the catalysts. ducted at a molar ratio of SiCU/H2 within a range of According to the present invention as shown in from 1 : 1 to 1 : 2, at a temperature within a range ?5 Table 1, the equilibrated conversion was obtained of from 1200 to 1400°C. in 38 min. and 5 min. at the respective reaction Now, the present invention will be described in temperatures of 25°C and 100°C in experiments detail with reference to Examples. However, it No. 8 and No. 9. In contrast to this, according to should be understood that the present invention is comparative experiments No. 20 and No. 22, the t>y no means restricted by these specific Exam- to equilibrated conversion was not obtained even at Dles. the end of 240 min. and 10 min., respectively. This difference leads to a difference in the production quantity of SiH,CI2 which amounts to 7 times and 2 ^WMCLt 1 times, respectively, when manufacturing SiH2CI2 from SiHCIj in the reaction vessels of the same Using trichlorosilane (SiHCIj), which was placed capacity. This proves that the effect to be derived n an autoclave (SUS 304) of 500 cc capacity and from the present invention is apparently superior. >rovided with a jacket and an agitator, the dis- (roportionation reaction was conducted in a her- o

5 IO 0 213 215 16

" ' ' Table 1 , ; , . , I | Time lapsea SiHCl3 con- 3iCld con- Ea„jlih_„,. Sxperi- Reac- Quantity Starting! until SiHCl3 centration Kind centration SiHCT «T ment of catalyst tion of material concentra- when it when it eentrati No- temp, catalyst SiHCl3 tion becomes became became tranon (°C) (mol) (mol) constant(min)constant(%) constant (%) (*) 1 Tri-n-butylamine 50 0.1 1 7 79.8 10.3 79.0 2 Tri-n-pentylamine 50 0.1 1 7 79.4 10.5 7g.o 3 Tri-n-hexylamine 50 0.1 1 6 79.5 10.3 79,0 4 Tri-n-heptylamine 50 0.1 1 6 79.3 11. 0 7g.0 5 Tri-n-octylamine 50 0.1 1 6 79.4 10.9 79.0 6 Tri-n-deeylamine 50 0.1 1 '6 79.4 10.5 79.0 7 Tri-n-dodecylamine 50 0.1 1 6 79.5 10.2 79.0 " 8 Tri-n-butylamine 25 0.1 1 38 80.2 11.5 80.0 " 9 100 0.1 1 2 76.0 13.6 76.0 " 10 150 0.1 1 1.5 74.5 14.4 74.0 11 Tri-n-octylamine 25 0.1 1 25 80.5 10.5 80.0 12 " 100 0.1 1 2 76.2 12.8 76.0 " 13 150 0.1 1 1.5 74.5 14.4 74.0 14 Tri-n-butylamine 50 0.04 1 55 85.8 7.1 79.0 15 " . 50 0.05 1 30 81.0 10.1 79.O 18 " 50 0.2 1 6 79.8 10.7 79.0 17 Tri-n-octylamine 50 0.04 1 40 84.7 8.1 79.0 " 18 50 0.05 1 24 80.5 9.7 79.0 " 19 50 0.2 1 5 79.0 11.3 79.0 20 Trimethylamine 25 0.1 1 240 95.6 3.1 • 80.0 " 21 50 0.1 1 60 92.0 5.0 79.0 " 22 100 0.1 1 10 80.3 10.9 76.o 23 Triethylamine 25 0.1 1 240 9Z.3 1.5 80.0 " 24 ,50 0.1 1 60 91.0 5.1 79.0 " 25 100 0.1 1 11 80.0 10.7 76.0 26 Tri-n-propylamine 25 0.1 1 210 93.2 4.2 80.0 " 27 50 0.1 1 55 88.8 7.0 79.0 " 28 100 0.1 1 10 79.0 10.6 76.0 29 Trimethylamine 50 0.1 1 220 87.5 7.3 n hydrochloride 79 30 Triethylamine 50 0.1 1 250 86.0 8.2 74 n hydrochloride

)

J 1 / U 213 215 18

For the purpose of comparison, under the same conditions as in Example 2 above, the disproportionation reactions were conducted by using triethylamine, tri-n-propylamine and trimethylamine SiHCIj used as the starting material in Example hydrochloride as the catalysts, at reaction tempera- 1 above was changed to SiH2Clj, and the dis- tures of 25°C, 50°C, and 100°C, respectively. The proportionation reaction was conducted under the results are shown in Table 2 below (experiments conditions as shown in Table 2 below, while quan- No. 42 -No. 48). The experiments were carried out titatively measuring concentration of SiH, in the gas by use of the agitator as was the case with the phase by gas chromatography. Table 2 indicates above-mentioned comparative experiments No. 20 the time when the concentration of SiH, became -No. 30. constant and the concentration thereof at that time. Also, in Table 2 below, the equilibrated concentration of SiH, obtained by calculation is shown as a reference. 70

o 01 •a a « u o JO >— ' CD o o CO a» 0) Of CO to CO CO CO CO CD fr- CO CO •a S-3 § W CO o o V US It in CN *J + in CO r-4 CM CO o m § E 2 CO CD CD to CO CO t- in in CO CO CO CO - a ccS«c«o a 11 H2 Ot5- » O n o 3 S3 o 3 C n c3 8b Li »h ML< CO cB o CO i ;2 t!, CNI CM CO COin J E jj : 8 S i C ( H 3 ( ) XI en 00 -i c 'E o c fl as i CO E OT ^

o « E

o ♦J • —i =9 in 3 n => 3 3 3 n3 s i

a) 3 3 V s -i3 ^ 3 3 CO 3 3 >• 3 n co M ^ 3 u a 5 -r >< 01 s >1 E? o c to 01> u 01 o r ° c 0 a £2 I I i c B a i 9) 1 s 2 C G 5 G G -I ^1 -4 -i

o r r «! 0) ■J E

1 19 0 213 215 20

tion of HCI. The conditions and the results are shown in Table 3. Experiments No. 49, No. 50, No. EXAMPLE 3 59, No. 60 and No. 67 in Table 3 are comparative examples. Experiments were conducted in the same man- 5 ner as in experiments No. 1 and No. 5 of- Example 1 except that the concentration of the hydrochloride was varied by changing the amount of the introduc-

10 Table 3

Time lapsed Equilibrated Hydro- Reaction until SiHCl3 SiHCl3 SiCl4 SiHCl3 Exoeri- Kind of merit catalyst chloride temp. concentra- concentra- concentra- concentra- No content tion becomes tion tion tion (%) constant (mol %) (°C) (min) (%) (%) (as calculated) 49 Trioctylamine - 50 12 80.1 11.2 79.0 50 " 1 50 11 79.6 11.0 79.0 51 " 2 50 7 78.3 10.5 79.0 52 " - 5 50 7 79.0 10.8 79.0 53 " 10 50 6 78.8 10.4 79.0 " 54 . 20 50 6 79.4 10.9 79.0 55 " 30 50 6 79.0 10.9 79.0 56 " 40 50 6 78.9 11.5 79.0 57 " 80 50 6 78.6 11.7 79.0 58 " 80 50 6 76.3 11.9 79.0 59 " 85 50 6 72.6 14.9 79.0 60 Tributylamine - 50 14 80.2 11.3 79.0 61 " 1 50 13 80.1 11.1 79.0 62 " 2 50 8 79.6- 10.8 79.0 63 " 10 50 7 78.3 10.9 79.0

64 " 20 50 7 79.8 10.3 79.0 65 " 30 50 6 78.2 11.9 79.0 66 " 80 50 6 76.4 12.0 79.0 67 " 85 50 6 70.6 17.0 79.0

As described in the foregoing, the present in- «. (1 ) The catalyst of the present invention pro- vention provides a chlorosilane disproportionation vides a conversion which is closer to the equili- catalyst composed essentially of a specific tertiary orated conversion, at a temperature of less than amine and its hydrochloride, and a method for the 150°C in comparison with the conventional cata- disproportionation of a chlorosilane by means of the catalyst. The following effects are obtainable by the present invention.

12 0 213 215 22

W wnen tne catalyst ot tne present inven- collecting tank 7 was analyzed by gas chromatog- tion is used, the equilibrated conversion is reached raphy, and it was found that the recovered liquid in a short period of time, which means a high contained 85 mol % of monosilane, 8.5 mol % of disproportionation velocity, and which makes it monochlorosilane and 6.5 mol % of dichlorosilane. possible to reduce the size of the reaction appara- 5 On the other hand, the chlorosilane evaporated tus. from the evaporation tank 9 was cooled in the (3) The catalyst according to the present condenser 11 and recovered in the tank 12 at a invention is completely soluble in the chlorosilane rate of 3.82 kg/hr. The composition of the recov- as the starting material, and also has a boiling point ered liquid was analyzed by gas chromatography, of 200°C and above. Accordingly, it serves to lower 70 and it was found that the liquid consisted of 48 mol the vapor pressure in the reaction liquid, and ad- % of trichlorosilane and 52 mol % of silicon tetra- vantageously contributes to safety in the operation. chloride. (4) The catalyst can be readily separated from the reaction product such as SiH,CI, or SiH4. (5) Since the reaction system is a uniform 75 EXAMPLE 5 liquid phase system, there is no necessity for agi- tation and other homogenizing operations. Thus, The operation was conducted in the same the transportion and various handling of the cata- manner as in Example 4 except that 2 liters of tri-n- lyst become advantageously simple. butylamine was charged to the evaporation tank 9 20 and 38 liters of hydrogen chloride gas was blown into it to prepare a catalyst containing 20 mol % of EXAMPLE 4 tri-n-butyiamine hydrochloride, and the catalyst thereby obtained was recycled to the reaction Into the evaporation tank 9, 2 liters of tri-n- tower 1 at a flow rate of 570 g/hr. As the results, a octylamine was charged, and then 21 liters of hy- 25 low boiling gas was obtained from the top of the drogen chloride gas was blown into it to prepare a tower at a rate of 170 g/hr. The recovered liquid catalyst containing 20 mol % of tri-n-octylamine consisted of 81 .5 mol % of monosilane, 9.5 mol % hydrochloride. Then, the heating medium oil in the of monochlorosilane, 8.0 mol % of dichlorosilane jacket was heated and maintained at a temperature and 1.0 mol % of trichlorosilane. On the other of 100°C. On the other hand, the condenser 3 30 hand, the chlorosilane mixture evaporated from the above the reaction tower was cooled with methanol evaporation tank 9 was cooled in the condenser 1 1 , dry ice of -60°C. The reboiler 2 at the bottom of and recovered in the storage tank 12 at a rate of the reaction tower was then heated by an electric 3.83 kg/hr. The recovered liquid consisted of 55 heater. Trichlorosilane was continuously supplied mol % of trichlorosilane and 45 mol % of silicon from the starting material supply conduit 4 into the 35 tetrachloride. reaction tower 1 at a flow rate of 4.0 kg/hr. At the same time, the catalyst in the evaporation tank 9 was circulated to the reaction tower 1 at a flow rate EXAMPLE 6 of 1.07 kg/hr by the operation of the catalyst cir- culation pump 10. The internal pressure of the «o The operation was conducted in the same reaction tower 1 was adjusted by an adjusting valve manner as in Example 4 except that the condenser 5 and maintained at a gauge pressure of 2 kg/cm2. 3 was cooled by circulating a saline of -10"C. As Wso, the liquid level of the reboiler 2 was adjusted the results, a gas mixture comprising 7 mol % of oy an adjusting valve 8 so that the liquid surface monosilane, 13 mol % of monochlorosilane, 66 mol was maintained at a constant level, and the reac- '5 % of dichlorosilane and 14% of tirchiorosilane was tion solution containing the catalyst in the reboiler obtained at a rate of 950 g/hr from the condenser was withdrawn to the evaporation tank 9. While 3. On the other hand, the chlorosilane mixture supplying hydrogen chloride gas to the recovered comprising 43 mol % of trichlorosilane and 57 mol catalyst at a flow rate of 50 cc/min through the % of silicon tetrachloride was recovered at a rate of supply line 13, the recovered catalyst was continu- o 3.05 kg/hr from the evaporation tank 9. ously recycled to the reaction tower. The reaction was continuously carried out for 20 hours while maintaining the temperature of the reboiler 2 at the EXAMPLE 7 oottom of the reaction tower at 85 °C, whereby a ow boiling gas was obtained from the top at a rate 5 The operation was conducted in the same 3f 180 g/hr. The recovered liquid collected in the manner as in Example 4 except that instead of hydrogen chloride gas, steam was supplied from the line 16 of Figure 1 at a flow rate of 30 cc/min.

3 23 0 213 215 24

The yield of the low boiling gas from the top was synthesizing trichlorosilane from silicon of methal- 175 g/hr, and the composition of the gas was lurgical. grade, hydrogen chloride, hydrogen and substantially the same as the one obtained in Ex- silicon tetrachloride, with a monosilane reaction and ample 4. distillation process of Example 4. A Hastelloy reactor having an internal capacity of 20 liters was used as the trichlorosilane syn- EXAMPLE 8 thesizing furnace 40, and operated at 600 °C under a pressure of 2 kg/cm2G. The conversion of trich- The operation was conducted in the same lorosilane in this step was 30%. The conditions for manner as in Example 4 except that instead of io the reaction tower 43 and the evaporator 52 were hydrogen chloride gas, a 35% hydrochloric acid the same as in Example 4. aqueous solution was supplied from the line 16 in As the results, the consumption of the starting Figure 1 at a flow rate of 40 cc/min, whereby material silicon of metallurgical grade was about 65 substantially the same results as in Example 7 g/hr under a monosilane production condition of 68 were obtained. 15 g/hr. In order to show the effects of the present invention clearly, the compositions of the silane mixtures around the distillation tower 41 were mea- EXAMPLE 9 sured, and the results are shown in Table 4. For the purpose of comparison, comparative experi- The operation was conducted in the same 20 ments were conducted by using the conventional manner as in Example 4 except that hydrogen ion exchange resins under the same conditions for chloride gas was supplied from the line 15 in the production of monosilane. The temperature of Figure 1 at a flow rate of 50 cc/min, whereby the ion exchange resin bed was 60°C. The com- substantially the same results as in Example 4 positions of the silane mixtures around the distilla- were obtained. 25 tion tower 21 are likewise shown in Table 4. It is apparent from Table 4 that the amount of treatment in the distillation tower according to the EXAMPLE 10 present invention is about 8 kg/hr which is more than 50% less that 14 kg/hr of the comparative An experiment for the production of monosilane 30 example. This means that the apparatus can be was conducted in accordance with the flow chart made compact and simplified. shown in Figure 3, to demonstrate the production of monosilane by the combination of the step for

14 2t> 0 213 215 26

5 27 0 213 215 28

Claims

1. A chlorosilane disproportionation catalyst comprising a tertiary amine of the formula:

^N-R (A) R/ where each R represents an aliphatic hydrocarbon group and the sum of carbon atoms in the three aliphatic hydrocarbon groups as R is 12 or more, and a tertiary amine hydrochloride of the formula:

R> S^N-RH+C1~ (B)

where R is as defined above. 25 drochloride of the formula (B) is tri-n-butylamine 2. The chlorosilane disproportionation catalyst hydrochloride, tri-n-octylamine hydrochloride or a according to Claim 1, wherein the sum of carbon mixture thereof. atoms in the three aliphatic hydrocabon groups as 5. The chlorosilane disproportionation catalyst R is from 12 to 36. according to Claim 1 , which comprises from 20 to 3. The chlorosilane disproportionation catalyst 30 98 mol % of the tertiary amine of the formula (A) according to Claim 1 , wherein the tertiary amine of and from 2 to 80 mol % of the tertiary amine the formula (A) is at least one member selected hydrochloride of the formula (B). from the group consisting of tri-n-butylamine, tri-n- 6. The chlorosilane disproportionation catalyst pentylamine, tri-n-hexylamine, tri-n-heptylamine, tri- according to Claim 1, which comprises from 70 to n-octylamine, tri-n-decylamine and tri-n- 35 90 mol % of the tertiary amine of the formula (A) dodecylamine, and the tertiary amine hydrochloride and from 10 to 30 mol % of the tertiary amine of the formula (B) is at least one member selected hydrochloride of the formula (B). from the group consisting of hydrochlorides of such 7. A method for disproportionating at least one amines. chlorosilane selected from the group consisting of 4. The chlorosilane disproportionation catalyst 40 monochlorosilane, dichlorosilane and trich- according to Claim 1 , wherein the tertiary amine of lorosilane, characterized in that the disproportiona- the formula (A) is tri-n-butyiamine, tri-n-octylamine tion is conducted by means of a chlorosilane dis- or a mixture thereof, and the tertiary amine hy- proportionation catalyst comprising a tertiary amine of the formula: 45

(A) R" 50 where each R represents an aliphatic hydrocarbon group and the sum of carbon atoms in the three aliphatic hydrocarbon groups as R is 12 or more, and amine of the formula: a tertiary hydrochloride 55

16 0 213 215 30

N-RH CI (B) R where R is as defined above. (a) supplying the starting material 8. A method for continuously producing a chlorosilane and a chlorosilane disproportionation silane compound such as monosilane or dich- catalyst comprising a tertiary amine of the formula: lorosilane by the disproportionation reaction of a starting material chlorosilane such as trichlorosilane, which comprises: 70

N-K (A)

wnere eacn n represents an anpnatic hydrocarbon group and the sum of carbon atoms in the three aliphatic hydrocarbon groups as R is 12 or more, 20 and a tertiary amine hydrochloride of the formula:

N-RH+C1~ (B)

wnere n is as aennea aoove, into a reaction tower 10. The method according to Claim 8, wherein laving a distilling function; ?o the reaction tower is operated at a temperature of b) obtaining, from the top of the tower, a from 10 to 300 °C under a gauge pressure of from silane compound containing more hydrogen atoms 0 to 40 kg/cm2. tian the starting material chlorosilane; 1 1 . The method according to Claim 8, wherein c) withdrawing, from the bottom of the tower, the starting material chlorosilane is trichlorosilane i liquid mixture comprising the catalyst and silane ?5 prepared by reacting metal silicon of metallurgical compounds containing more chlorine atoms as by- grade, hydrogen, hydrogen chloride and silicon tet- products; rachloride, followed by distillation. d) separating the silane compounds and the 12. The method according to Claim 8, wherein catalyst in the liquid mixture; and the staring material chlorsilane is trichlorosilane e) recycling the separated catalyst to the io prepared by reacting silica, carbon and chlorine eaction tower. gas to form silicon tetrachloride, condensing the 9. The method according to Claim 8, wherein formed silicon tetrachloride gas and subjecting it to he catalyst is used in an amount of from 2 to 50 distillation to remove low and high boiling compo- nol % relative to the starting material chlorosilane. nents, followed by reduction with hydrogen to con- 15 vert the silicon tetrachloride to trichlorosilane.

7 1213 215 ETA -5/97

0 213 215

LU ct 3 CD

C\jCO

51 T7TL Application number Office »-wnwi-cj*r« amnun HtrUKT

EP 85 11 0110

. ■ w vwiwu/Lntu iv DC MCLCVAN F r.««. j _ _ —— — i of relevant wLAoolrltATION OF THE passages to claim APPLICATION (Int CI 4 )

C 01 B 33/107 L- / C 01 B 33/04 :orp ) . B 01 J 31/02 Claims 1-5; page 6, lines L5-37; page 7, lines 4-10, 19-23; sage 8, line 31 - page 9, line 31

- — — — — — \ wijiiijiu-ijj -12 ;lectric corp. ) Claims 1-6 *

OGYO K . K . ) Claims 1-12; figures 1-3 * tOHNiWU. rltLDS EARCMED (Int CM,

: ui B ■ 01 J

IE examiner HAGUE 23-C5-1986 ERTENS J.

— — — • i *j meory or principle underlying the invention earlier rticularly relevant if taken alone patent document, but published on, or Y rticulariy relevant If after the filing date combined with another document cited the dc eument of the same cst&gory in application A te hnolooical bacnground document cited tor other reasons nc n-wnrten disclosure in1 ermediate member of the same patent family, document document corresponding