US20020151737A1 - Dust recirculation in the direct synthesis of chlorosilanes and methylchlorosilanes in a fluidized bed - Google Patents
Dust recirculation in the direct synthesis of chlorosilanes and methylchlorosilanes in a fluidized bed Download PDFInfo
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- US20020151737A1 US20020151737A1 US10/119,626 US11962602A US2002151737A1 US 20020151737 A1 US20020151737 A1 US 20020151737A1 US 11962602 A US11962602 A US 11962602A US 2002151737 A1 US2002151737 A1 US 2002151737A1
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- fluidized bed
- dust
- suspension
- silicon
- silanes
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- 239000000428 dust Substances 0.000 title claims abstract description 38
- 230000015572 biosynthetic process Effects 0.000 title claims abstract description 31
- 238000003786 synthesis reaction Methods 0.000 title claims abstract description 31
- YGZSVWMBUCGDCV-UHFFFAOYSA-N chloro(methyl)silane Chemical class C[SiH2]Cl YGZSVWMBUCGDCV-UHFFFAOYSA-N 0.000 title claims description 38
- 239000005046 Chlorosilane Substances 0.000 title claims description 15
- KOPOQZFJUQMUML-UHFFFAOYSA-N chlorosilane Chemical class Cl[SiH3] KOPOQZFJUQMUML-UHFFFAOYSA-N 0.000 title claims description 15
- 239000000725 suspension Substances 0.000 claims abstract description 32
- XUIMIQQOPSSXEZ-UHFFFAOYSA-N Silicon Chemical compound [Si] XUIMIQQOPSSXEZ-UHFFFAOYSA-N 0.000 claims abstract description 26
- 229910052710 silicon Inorganic materials 0.000 claims abstract description 21
- 239000010703 silicon Substances 0.000 claims abstract description 21
- 239000007788 liquid Substances 0.000 claims abstract description 18
- 239000000047 product Substances 0.000 claims abstract description 16
- 150000004756 silanes Chemical class 0.000 claims abstract description 12
- 239000007795 chemical reaction product Substances 0.000 claims abstract description 10
- 238000010924 continuous production Methods 0.000 claims abstract description 4
- 125000001495 ethyl group Chemical group [H]C([H])([H])C([H])([H])* 0.000 claims abstract description 3
- 239000001257 hydrogen Substances 0.000 claims abstract description 3
- 229910052739 hydrogen Inorganic materials 0.000 claims abstract description 3
- 125000004435 hydrogen atom Chemical group [H]* 0.000 claims abstract description 3
- 125000002496 methyl group Chemical group [H]C([H])([H])* 0.000 claims abstract description 3
- 239000011541 reaction mixture Substances 0.000 claims abstract description 3
- 238000000034 method Methods 0.000 claims description 30
- 239000002245 particle Substances 0.000 claims description 17
- 239000007789 gas Substances 0.000 claims description 11
- 238000001914 filtration Methods 0.000 claims description 9
- 238000006243 chemical reaction Methods 0.000 description 13
- 239000003054 catalyst Substances 0.000 description 12
- NEHMKBQYUWJMIP-UHFFFAOYSA-N chloromethane Chemical compound ClC NEHMKBQYUWJMIP-UHFFFAOYSA-N 0.000 description 11
- 239000007787 solid Substances 0.000 description 7
- 239000000203 mixture Substances 0.000 description 6
- 238000004821 distillation Methods 0.000 description 5
- RYGMFSIKBFXOCR-UHFFFAOYSA-N Copper Chemical compound [Cu] RYGMFSIKBFXOCR-UHFFFAOYSA-N 0.000 description 4
- VEXZGXHMUGYJMC-UHFFFAOYSA-N Hydrochloric acid Chemical compound Cl VEXZGXHMUGYJMC-UHFFFAOYSA-N 0.000 description 4
- 229910052802 copper Inorganic materials 0.000 description 4
- 239000010949 copper Substances 0.000 description 4
- 229910000041 hydrogen chloride Inorganic materials 0.000 description 4
- IXCSERBJSXMMFS-UHFFFAOYSA-N hydrogen chloride Substances Cl.Cl IXCSERBJSXMMFS-UHFFFAOYSA-N 0.000 description 4
- 238000009833 condensation Methods 0.000 description 3
- 230000005494 condensation Effects 0.000 description 3
- PXHVJJICTQNCMI-UHFFFAOYSA-N nickel Substances [Ni] PXHVJJICTQNCMI-UHFFFAOYSA-N 0.000 description 3
- 239000012071 phase Substances 0.000 description 3
- JTJMJGYZQZDUJJ-UHFFFAOYSA-N phencyclidine Chemical class C1CCCCN1C1(C=2C=CC=CC=2)CCCCC1 JTJMJGYZQZDUJJ-UHFFFAOYSA-N 0.000 description 3
- XEEYBQQBJWHFJM-UHFFFAOYSA-N Iron Chemical compound [Fe] XEEYBQQBJWHFJM-UHFFFAOYSA-N 0.000 description 2
- KQHIGRPLCKIXNJ-UHFFFAOYSA-N chloro-methyl-silylsilane Chemical class C[SiH]([SiH3])Cl KQHIGRPLCKIXNJ-UHFFFAOYSA-N 0.000 description 2
- 229910052804 chromium Inorganic materials 0.000 description 2
- 239000011651 chromium Substances 0.000 description 2
- LIKFHECYJZWXFJ-UHFFFAOYSA-N dimethyldichlorosilane Chemical compound C[Si](C)(Cl)Cl LIKFHECYJZWXFJ-UHFFFAOYSA-N 0.000 description 2
- 238000001704 evaporation Methods 0.000 description 2
- 230000008020 evaporation Effects 0.000 description 2
- 239000007791 liquid phase Substances 0.000 description 2
- 229910052759 nickel Inorganic materials 0.000 description 2
- 239000002574 poison Substances 0.000 description 2
- 231100000614 poison Toxicity 0.000 description 2
- -1 polysiloxanes Polymers 0.000 description 2
- 239000000843 powder Substances 0.000 description 2
- 238000001556 precipitation Methods 0.000 description 2
- 238000002360 preparation method Methods 0.000 description 2
- 230000009257 reactivity Effects 0.000 description 2
- 238000000926 separation method Methods 0.000 description 2
- 229910021332 silicide Inorganic materials 0.000 description 2
- 239000011863 silicon-based powder Substances 0.000 description 2
- VYZAMTAEIAYCRO-UHFFFAOYSA-N Chromium Chemical compound [Cr] VYZAMTAEIAYCRO-UHFFFAOYSA-N 0.000 description 1
- 229910005331 FeSi2 Inorganic materials 0.000 description 1
- 238000009825 accumulation Methods 0.000 description 1
- 230000003213 activating effect Effects 0.000 description 1
- 238000009835 boiling Methods 0.000 description 1
- 239000006227 byproduct Substances 0.000 description 1
- 239000011362 coarse particle Substances 0.000 description 1
- 150000001875 compounds Chemical class 0.000 description 1
- 239000000470 constituent Substances 0.000 description 1
- 238000010276 construction Methods 0.000 description 1
- 238000001816 cooling Methods 0.000 description 1
- 238000005336 cracking Methods 0.000 description 1
- 238000009295 crossflow filtration Methods 0.000 description 1
- 230000007423 decrease Effects 0.000 description 1
- 238000005194 fractionation Methods 0.000 description 1
- 229910021485 fumed silica Inorganic materials 0.000 description 1
- 239000007792 gaseous phase Substances 0.000 description 1
- 230000001771 impaired effect Effects 0.000 description 1
- 238000009776 industrial production Methods 0.000 description 1
- 230000002452 interceptive effect Effects 0.000 description 1
- 229910052742 iron Inorganic materials 0.000 description 1
- 239000011133 lead Substances 0.000 description 1
- 230000007257 malfunction Effects 0.000 description 1
- 238000004519 manufacturing process Methods 0.000 description 1
- 239000000463 material Substances 0.000 description 1
- 239000011236 particulate material Substances 0.000 description 1
- 229920001296 polysiloxane Polymers 0.000 description 1
- 230000002035 prolonged effect Effects 0.000 description 1
- 230000001698 pyrogenic effect Effects 0.000 description 1
- 230000003134 recirculating effect Effects 0.000 description 1
- 238000005201 scrubbing Methods 0.000 description 1
- 238000004904 shortening Methods 0.000 description 1
- FVBUAEGBCNSCDD-UHFFFAOYSA-N silicide(4-) Chemical compound [Si-4] FVBUAEGBCNSCDD-UHFFFAOYSA-N 0.000 description 1
- FDNAPBUWERUEDA-UHFFFAOYSA-N silicon tetrachloride Chemical compound Cl[Si](Cl)(Cl)Cl FDNAPBUWERUEDA-UHFFFAOYSA-N 0.000 description 1
- 239000011856 silicon-based particle Substances 0.000 description 1
- 239000002893 slag Substances 0.000 description 1
- 239000002002 slurry Substances 0.000 description 1
- 230000002269 spontaneous effect Effects 0.000 description 1
- 238000003756 stirring Methods 0.000 description 1
- 238000004381 surface treatment Methods 0.000 description 1
- ZDHXKXAHOVTTAH-UHFFFAOYSA-N trichlorosilane Chemical compound Cl[SiH](Cl)Cl ZDHXKXAHOVTTAH-UHFFFAOYSA-N 0.000 description 1
- 239000005052 trichlorosilane Substances 0.000 description 1
- 238000010626 work up procedure Methods 0.000 description 1
Classifications
-
- C—CHEMISTRY; METALLURGY
- C07—ORGANIC CHEMISTRY
- C07F—ACYCLIC, CARBOCYCLIC OR HETEROCYCLIC COMPOUNDS CONTAINING ELEMENTS OTHER THAN CARBON, HYDROGEN, HALOGEN, OXYGEN, NITROGEN, SULFUR, SELENIUM OR TELLURIUM
- C07F7/00—Compounds containing elements of Groups 4 or 14 of the Periodic Table
- C07F7/02—Silicon compounds
- C07F7/08—Compounds having one or more C—Si linkages
- C07F7/12—Organo silicon halides
- C07F7/16—Preparation thereof from silicon and halogenated hydrocarbons direct synthesis
Definitions
- the invention relates to a process for the direct synthesis of chlorosilanes and methylchlorosilanes in a fluidized bed, in which process silicon-containing dust formed is introduced in the form of a suspension in a liquid into the fluidized bed.
- chlorosilanes silicon is reacted with hydrogen chloride, in the presence or absence of a copper catalyst, to form trichlorosilane and tetrachlorosilane.
- Chlorosilanes are required, for example, for the preparation of pyrogenic silica. Pyrogenic silicas can also be prepared from methylchlorosilanes and mixtures of methylchlorosilanes and chlorosilanes without the product quality being impaired.
- Both processes can be carried out batchwise, continuously or semicontinuously. In industrial production, they are preferably carried out continuously.
- the continuous direct synthesis is carried out in fluidized-bed reactors in which chloromethane or hydrogen chloride and gaseous reaction products act as the fluidizing medium.
- the silicon required is milled to a powder having a particular particle size before the synthesis.
- the silicon powder is mixed with copper catalysts and promoters to form a catalyst-containing composition.
- This catalyst-containing composition is subsequently introduced into the fluidized-bed reactor and reacted therein. Unreacted chloromethane, gaseous methylchlorosilanes, gaseous by-products, catalyst constituents, and finely divided dusts leave the reactor.
- FIG. 1 shows a system comprising a reactor, a main cyclone with recirculation and an after-cyclone with a dust collection vessel.
- part of the particulate material precipitated in the after-cyclone are subjected to a surface treatment and subsequently fed back into the reactor as solids. This is said to achieve a high silicon conversion.
- the gas stream leaving the cyclone(s) always still contains residual dust which has to be separated prior to the distillation of the methylchlorosilanes.
- 4,328,353 proposes that the gas stream which has passed through the cyclone be subjected to a hot gas filtration and the pulverulent material obtained here be recirculated to the reactor or discharged from the process.
- the possibility of passing these fine dusts without further treatment to a reaction with HCl (chlorosilane synthesis) is also disclosed.
- EP-A-900802 likewise describes a hot gas filtration with subsequent recirculation of the particles.
- the invention provides a continuous process for the direct synthesis of silanes of the formula 1
- R is hydrogen, methyl or ethyl
- a is 0, 1, 2, 3 or 4,
- a product stream comprising gaseous silanes of the formula 1, further gaseous reaction products, unreacted RCl and silicon-containing dust is discharged from the fluidized bed, wherein at least part of the dust is introduced in the form of a suspension in a liquid selected from among liquid silanes of the formula 1, further liquid reaction products and mixtures thereof into the fluidized bed.
- the silicon required for the direct synthesis is milled to a powder having a particle size of preferably not more than 2000 ⁇ m, in particular not more than 500 ⁇ m, prior to the synthesis.
- the particle size of the recovered dust is preferably not more than 200 ⁇ m, in particular not more than 30 ⁇ m.
- gaseous reaction products present in the product stream are mainly oligosilanes, carbosilanes, siloxanes and high-boiling cracking products.
- the gaseous reaction products are liquefied and, like the liquid silanes of the formula 1, may serve as suspension medium for the dust.
- suspension refers to all mixtures of dust and liquid which are pumpable, including slurries and suspensions in which the dust particles remain suspended for only a short time after stirring in the dust.
- the suspensions are preferably capable of being sprayed, and are most preferably sprayed into the fluidized bed. To stabilize the suspensions, it is possible to add customary suspension aids.
- the suspension preferably contains from 0.5% by weight to 30% by weight, more preferably from 1% by weight to 10% by weight, of dust.
- the silicon powder is mixed with copper catalysts and promoters to form a catalyst-containing composition.
- This catalyst-containing composition is subsequently introduced into the fluidized-bed reactor and reacted at a temperature of preferably 260-350° C. Since the reaction is exothermic, the heat of reaction which is liberated has to be removed by means of a cooling system. Gaseous products and finely divided dusts leave the reactor.
- the relatively coarse entrained particles can be separated from the gas stream by means of one or more cyclones and be returned to the reactor or discharged from the system via dust collection vessels. The very fine entrained particles can be separated off in downstream components of the plant. In this way, a high conversion of silicon can be ensured.
- the chlorosilane synthesis is carried out at a temperature of about 300-800° C.; the reaction is likewise exothermic but does not have to be catalyzed.
- the quality demands made of the silicon to be used are considerably less severe than in the methylchlorosilane synthesis, since in this case various elements present in the silicon as secondary components, for example Ni or Cr, do not act as catalyst poisons, and various silicide phases, for example FeSi 2 , are able to react with HCl, unlike the case of MeCl.
- the dust collected in a chlorosilane synthesis it is possible for the dust collected in a chlorosilane synthesis to be introduced in the form of a suspension into the fluidized bed of a methylchlorosilane synthesis by the Müller-Rochow method, or for the dust collected in a methylchlorosilane synthesis by the Müller-Rochow method to be introduced in the form of a suspension into the fluidized bed of a chlorosilane synthesis.
- Solid/liquid separation by means of evaporation processes or filtration is more effective than solid/gas separation by means of hot gas filtration. Condensation of the product stream after hot gas filtration and/or distillation of the methylchlorosilanes therefore produces an additional liquid dust-containing methylchlorosilane product stream.
- This dust-containing methylchlorosilane product stream is preferably introduced as a suspension into the fluidized bed.
- equipment used for preparing methylchlorosilanes in a fluidized-bed reactor are preferably either (A) at least 2 cyclones, a subsequent condensation unit and a downstream concentrator unit or (B) at least 2 cyclones with subsequent hot gas filtration and a downstream suspension unit.
- a preferred embodiment of the process is carried out using the equipment described in (A) above.
- the product stream leaving the fluidized-bed reactor of the methylchlorosilane synthesis passes through a 1st cyclone, where the relatively coarse particles are precipitated and recirculated to the reactor.
- the finer particles are precipitated. These finer particles may either be returned in the form of a suspension to the reactor or may be discharged. Discharge can be carried out continuously or at intervals. At least part of the methylchlorosilanes formed are condensed from the remaining product stream by means of appropriate measures.
- Condensation can be achieved, for example, by passing the product stream into liquid methylchlorosilanes, by introducing this stream into a scrubbing tower operated using liquid methylchlorosilanes, or into a fractionation column provided with appropriate internals.
- the gaseous phase comprises mainly unreacted chloromethane and volatile methylchlorosilanes.
- the chloromethane is, after appropriate work-up, fed back into the production process.
- the liquid phase comprises mainly methylchlorosilanes and solids.
- the solids are concentrated by an appropriate method, for example filtration, in particular crossflow filtration, or evaporation of part of the methylchlorosilane, to such an extent that the suspension remains.
- the solids-free methylchlorosilanes are passed to distillation while the suspension is sprayed into a running fluidized-bed reactor for preparing methylchlorosilanes and/or chlorosilanes.
- the methylchlorosilanes When the suspension is sprayed into the reactor, the methylchlorosilanes vaporize and the dust particles agglomerate to form larger, quite stable aggregates, or may form stable deposits on existing Si grains.
- the size of the agglomerates depends very strongly on the chosen process conditions, for example the solids content of the suspension. Depending on size, the agglomerates remain in the reactor or are precipitated in the 1st cyclone and returned to the reactor. This portion of the agglomerates is thus once again available to the desired reaction. The smaller agglomerates are precipitated in the 2nd cyclone and leave the reaction system via this route.
- the suspension is introduced into a reactor for preparing chlorosilanes and the liquid phase comprises mainly methylchlorodisilanes, part of the latter can be cleaved in the reactor to produce more useful methylchlorosilanes.
- a further preferred embodiment of the process is carried out in the equipment described in (B) above.
- the product stream leaving the fluidized-bed reactor of the methylchlorosilane synthesis passes through the 1st cyclone.
- the coarser particles are precipitated there and returned to the reactor.
- the exit system is subjected to a hot gas filtration as described, for example, in U.S. Pat. No. 4,328,353.
- the dusts precipitated by this phase of the process are mixed with liquid methylchlorosilanes and/or methylchlorodisilanes or methylchlorosilanes laden with solids, which are obtained in the subsequent distillation section, so as to form a suitable suspension.
- the suspension is preferably processed further as in embodiment (A) and, in particular, is introduced into a reactor for preparing chlorosilanes in order to prevent accumulation of interfering elements/compounds.
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- Chemical & Material Sciences (AREA)
- Organic Chemistry (AREA)
- Silicon Compounds (AREA)
Abstract
Description
- 1. Field of the Invention
- The invention relates to a process for the direct synthesis of chlorosilanes and methylchlorosilanes in a fluidized bed, in which process silicon-containing dust formed is introduced in the form of a suspension in a liquid into the fluidized bed.
- 2. Background Art
- In the Müller-Rochow direct synthesis, chloromethane is reacted with silicon in the presence of a copper catalyst and suitable promoters to produce methylchlorosilanes. In this process, very high selectivity to the target product dimethyldichlorosilane is necessary. Dimethyldichlorosilane is required, for example, for the preparation of linear polysiloxanes.
- In the direct synthesis of chlorosilanes, silicon is reacted with hydrogen chloride, in the presence or absence of a copper catalyst, to form trichlorosilane and tetrachlorosilane. Chlorosilanes are required, for example, for the preparation of pyrogenic silica. Pyrogenic silicas can also be prepared from methylchlorosilanes and mixtures of methylchlorosilanes and chlorosilanes without the product quality being impaired.
- In both processes, not only a very high productivity, measured as the amount of silanes formed per unit time and per reaction volume, but also a very high silicon conversion combined with reliable and flexible operation of the overall plant are required.
- Both processes can be carried out batchwise, continuously or semicontinuously. In industrial production, they are preferably carried out continuously.
- The continuous direct synthesis is carried out in fluidized-bed reactors in which chloromethane or hydrogen chloride and gaseous reaction products act as the fluidizing medium. The silicon required is milled to a powder having a particular particle size before the synthesis.
- In the methylchlorosilane synthesis, the silicon powder is mixed with copper catalysts and promoters to form a catalyst-containing composition. This catalyst-containing composition is subsequently introduced into the fluidized-bed reactor and reacted therein. Unreacted chloromethane, gaseous methylchlorosilanes, gaseous by-products, catalyst constituents, and finely divided dusts leave the reactor.
- In U.S. Pat. No. 4,281,149, FIG. 1 shows a system comprising a reactor, a main cyclone with recirculation and an after-cyclone with a dust collection vessel. In this process, part of the particulate material precipitated in the after-cyclone are subjected to a surface treatment and subsequently fed back into the reactor as solids. This is said to achieve a high silicon conversion. The gas stream leaving the cyclone(s) always still contains residual dust which has to be separated prior to the distillation of the methylchlorosilanes. U.S. Pat. No. 4,328,353 proposes that the gas stream which has passed through the cyclone be subjected to a hot gas filtration and the pulverulent material obtained here be recirculated to the reactor or discharged from the process. The possibility of passing these fine dusts without further treatment to a reaction with HCl (chlorosilane synthesis) is also disclosed. EP-A-900802 likewise describes a hot gas filtration with subsequent recirculation of the particles.
- When very fine dusts are introduced directly into fluidized-bed reactors of the chlorosilane synthesis or methylchlorosilane synthesis, these particles are very quickly swept out again, and are thus not available to the reaction. At the same time, the recirculation of fine dusts in this manner leads to a considerably greater load on the entire dust precipitation system.
- Furthermore, these very fine silicon dusts in dry form are extremely reactive toward air and atmospheric moisture, i.e. when this product stream accidentally comes into contact with air, as may occur in the case of a malfunction in the plant, spontaneous ignition has to be reckoned with.
- It is an object of the present invention to provide a continuous process for the direct synthesis of chlorosilanes and methylchlorosilanes in a fluidized bed, in which process the finely divided dusts which are formed and are entrained within the reaction product can be reused effectively.
- The invention provides a continuous process for the direct synthesis of silanes of the formula 1
- RaSiCl4−a (1)
- by reacting finely divided silicon metal with R—Cl in a fluidized bed, where
- R is hydrogen, methyl or ethyl and
- a is 0, 1, 2, 3 or 4,
- where a product stream comprising gaseous silanes of the formula 1, further gaseous reaction products, unreacted RCl and silicon-containing dust is discharged from the fluidized bed, wherein at least part of the dust is introduced in the form of a suspension in a liquid selected from among liquid silanes of the formula 1, further liquid reaction products and mixtures thereof into the fluidized bed.
- It has been found that the very fine dust particles formed in the continuous fluidized-bed process very readily agglomerate to form larger units or deposit on existing Si grains when the dust particles are introduced in the form of a suspension into a running fluidized-bed reactor. As a result, the silicon-containing dust remains in the fluidized bed for a prolonged period and is reacted effectively therein. An increased load on the dust precipitation system is thusly avoided. Even very fine silicon-containing dusts can be handled safely in the process, and a high overall silicon conversion is achieved. Disadvantages such as decreases in selectivity and/or reactivity and/or shortening of the operating time (“campaign”) of the reactor in the methylchlorosilane synthesis can be avoided by this method.
- The silicon required for the direct synthesis is milled to a powder having a particle size of preferably not more than 2000 μm, in particular not more than 500 μm, prior to the synthesis. The particle size of the recovered dust is preferably not more than 200 μm, in particular not more than 30 μm.
- Further gaseous reaction products present in the product stream are mainly oligosilanes, carbosilanes, siloxanes and high-boiling cracking products. The gaseous reaction products are liquefied and, like the liquid silanes of the formula 1, may serve as suspension medium for the dust.
- The term “suspension” refers to all mixtures of dust and liquid which are pumpable, including slurries and suspensions in which the dust particles remain suspended for only a short time after stirring in the dust. The suspensions are preferably capable of being sprayed, and are most preferably sprayed into the fluidized bed. To stabilize the suspensions, it is possible to add customary suspension aids. The suspension preferably contains from 0.5% by weight to 30% by weight, more preferably from 1% by weight to 10% by weight, of dust.
- In the methylchlorosilane synthesis by the Müller-Rochow method, the silicon powder is mixed with copper catalysts and promoters to form a catalyst-containing composition. This catalyst-containing composition is subsequently introduced into the fluidized-bed reactor and reacted at a temperature of preferably 260-350° C. Since the reaction is exothermic, the heat of reaction which is liberated has to be removed by means of a cooling system. Gaseous products and finely divided dusts leave the reactor. Depending on the plant construction, it is possible, for example, for the relatively coarse entrained particles to be separated from the gas stream by means of one or more cyclones and be returned to the reactor or discharged from the system via dust collection vessels. The very fine entrained particles can be separated off in downstream components of the plant. In this way, a high conversion of silicon can be ensured.
- The chlorosilane synthesis is carried out at a temperature of about 300-800° C.; the reaction is likewise exothermic but does not have to be catalyzed. The quality demands made of the silicon to be used are considerably less severe than in the methylchlorosilane synthesis, since in this case various elements present in the silicon as secondary components, for example Ni or Cr, do not act as catalyst poisons, and various silicide phases, for example FeSi2, are able to react with HCl, unlike the case of MeCl.
- It is possible for the dust collected in a chlorosilane synthesis to be introduced in the form of a suspension into the fluidized bed of a methylchlorosilane synthesis by the Müller-Rochow method, or for the dust collected in a methylchlorosilane synthesis by the Müller-Rochow method to be introduced in the form of a suspension into the fluidized bed of a chlorosilane synthesis.
- Complete recirculation of all dusts into the fluidized-bed reactor as described, for example, in EP-A-900802, can cause catalyst poisons such as lead, chromium and nickel and unreactive particles such as iron silicides and slag to accumulate in the reaction system, particularly in the methylchlorosilane synthesis. As a result, the selectivity, reactivity and the operating time of the reactor can be reduced as a result. For this reason, preference is given to recirculating only from 10 to 90% by weight, in particular from 20 to 80% by weight, of the dust into the fluidized bed. In a further preferred variant, the recirculation of the dust, i.e. the introduction of the dust as a suspension into the fluidized bed, is carried out in phases, particularly at times at which an increased amount of fine dusts is obtained, as may be the case, for example, when starting up a reactor.
- Solid/liquid separation by means of evaporation processes or filtration is more effective than solid/gas separation by means of hot gas filtration. Condensation of the product stream after hot gas filtration and/or distillation of the methylchlorosilanes therefore produces an additional liquid dust-containing methylchlorosilane product stream. This dust-containing methylchlorosilane product stream is preferably introduced as a suspension into the fluidized bed.
- In the present process, equipment used for preparing methylchlorosilanes in a fluidized-bed reactor are preferably either (A) at least 2 cyclones, a subsequent condensation unit and a downstream concentrator unit or (B) at least 2 cyclones with subsequent hot gas filtration and a downstream suspension unit.
- A preferred embodiment of the process is carried out using the equipment described in (A) above. The product stream leaving the fluidized-bed reactor of the methylchlorosilane synthesis passes through a 1st cyclone, where the relatively coarse particles are precipitated and recirculated to the reactor. In the 2nd cyclone, the finer particles are precipitated. These finer particles may either be returned in the form of a suspension to the reactor or may be discharged. Discharge can be carried out continuously or at intervals. At least part of the methylchlorosilanes formed are condensed from the remaining product stream by means of appropriate measures. Condensation can be achieved, for example, by passing the product stream into liquid methylchlorosilanes, by introducing this stream into a scrubbing tower operated using liquid methylchlorosilanes, or into a fractionation column provided with appropriate internals. After this process, the gaseous phase comprises mainly unreacted chloromethane and volatile methylchlorosilanes. The chloromethane is, after appropriate work-up, fed back into the production process. The liquid phase comprises mainly methylchlorosilanes and solids. The solids are concentrated by an appropriate method, for example filtration, in particular crossflow filtration, or evaporation of part of the methylchlorosilane, to such an extent that the suspension remains.
- The solids-free methylchlorosilanes are passed to distillation while the suspension is sprayed into a running fluidized-bed reactor for preparing methylchlorosilanes and/or chlorosilanes.
- When the suspension is sprayed into the reactor, the methylchlorosilanes vaporize and the dust particles agglomerate to form larger, quite stable aggregates, or may form stable deposits on existing Si grains. The size of the agglomerates depends very strongly on the chosen process conditions, for example the solids content of the suspension. Depending on size, the agglomerates remain in the reactor or are precipitated in the 1st cyclone and returned to the reactor. This portion of the agglomerates is thus once again available to the desired reaction. The smaller agglomerates are precipitated in the 2nd cyclone and leave the reaction system via this route. The methylchlorosilanes sprayed in ultimately end up in the distillation unit and do not have to be disposed of with the dust.
- If the suspension is introduced into a reactor for preparing methylchlorosilanes, the activating effect of the catalyst-containing silicon particles which are already passing through a direct synthesis for preparing methylchlorosilanes, as described in U.S. Pat. No. 5,625,088, can simultaneously be achieved.
- If the suspension is introduced into a reactor for preparing chlorosilanes and the liquid phase comprises mainly methylchlorodisilanes, part of the latter can be cleaved in the reactor to produce more useful methylchlorosilanes.
- A further preferred embodiment of the process is carried out in the equipment described in (B) above. The product stream leaving the fluidized-bed reactor of the methylchlorosilane synthesis passes through the 1st cyclone. The coarser particles are precipitated there and returned to the reactor. The exit system is subjected to a hot gas filtration as described, for example, in U.S. Pat. No. 4,328,353. The dusts precipitated by this phase of the process are mixed with liquid methylchlorosilanes and/or methylchlorodisilanes or methylchlorosilanes laden with solids, which are obtained in the subsequent distillation section, so as to form a suitable suspension.
- The suspension is preferably processed further as in embodiment (A) and, in particular, is introduced into a reactor for preparing chlorosilanes in order to prevent accumulation of interfering elements/compounds.
- While embodiments of the invention have been illustrated and described, it is not intended that these embodiments illustrate and describe all possible forms of the invention. Rather, the words used in the specification are words of description rather than limitation, and it is understood that various changes may be made without departing from the spirit and scope of the invention.
Claims (7)
Applications Claiming Priority (3)
Application Number | Priority Date | Filing Date | Title |
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DE10118483A DE10118483C1 (en) | 2001-04-12 | 2001-04-12 | Continuous direct synthesis of silane and mono-, di-, tri- and tetra-chlorosilanes, used e.g. in production of linear polysiloxanes or pyrogenic silica, in fluidized bed includes recycling dust containing silicon as suspension in liquid |
DE10118483 | 2001-04-12 | ||
DE10118483.2 | 2001-04-12 |
Publications (2)
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US6465674B1 US6465674B1 (en) | 2002-10-15 |
US20020151737A1 true US20020151737A1 (en) | 2002-10-17 |
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US10/119,626 Expired - Fee Related US6465674B1 (en) | 2001-04-12 | 2002-04-10 | Dust recirculation in the direct synthesis of chlorosilanes and methylchlorosilanes in a fluidized bed |
Country Status (6)
Country | Link |
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US (1) | US6465674B1 (en) |
EP (1) | EP1249453B1 (en) |
JP (1) | JP3759721B2 (en) |
CN (1) | CN1164596C (en) |
DE (2) | DE10118483C1 (en) |
MY (1) | MY122853A (en) |
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US20050226803A1 (en) * | 2004-04-08 | 2005-10-13 | Wacker-Chemie Gmbh | Process for preparing trichloromonosilane |
US20060183958A1 (en) * | 2003-04-01 | 2006-08-17 | Breneman William C | Process for the treatment of waste metal chlorides |
US20070086936A1 (en) * | 2003-07-07 | 2007-04-19 | Jan-Otto Hoel | Method for production of trichlorosilane and silicon for use in the production of trichlorosilane |
US20090016947A1 (en) * | 2006-03-03 | 2009-01-15 | Wacker Chemie Ag | Recycling of high-boiling compounds within an integrated chlorosilane system |
US20100032630A1 (en) * | 2008-08-04 | 2010-02-11 | Hariharan Alleppey V | Recovery of silicon from kerf silicon waste |
US20100129281A1 (en) * | 2007-04-25 | 2010-05-27 | Per Bakke | A process for the recycling of high purity silicon metal |
CN101440102B (en) * | 2008-12-19 | 2011-07-20 | 山东东岳有机硅材料有限公司 | Method for processing methyl monomer synthesized washing slurry |
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CN1321731C (en) * | 2005-01-26 | 2007-06-20 | 浙江大学 | Reactor of organic silicon fluidized bed with cyclone separator |
US8168123B2 (en) * | 2009-02-26 | 2012-05-01 | Siliken Chemicals, S.L. | Fluidized bed reactor for production of high purity silicon |
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DE102010001691A1 (en) * | 2010-02-09 | 2011-08-11 | Wacker Chemie AG, 81737 | Separation of solids and mixtures containing liquid silicon compounds |
DE102010063446A1 (en) * | 2010-12-17 | 2012-06-21 | Wacker Chemie Ag | Direct synthesis of alkylchlorosilanes in a liquid reaction medium |
DE102011005647A1 (en) * | 2011-03-16 | 2012-10-04 | Evonik Degussa Gmbh | Composite process for the conversion of STC-containing and OCS-containing side streams to hydrogen-containing chlorosilanes |
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US8875728B2 (en) | 2012-07-12 | 2014-11-04 | Siliken Chemicals, S.L. | Cooled gas distribution plate, thermal bridge breaking system, and related methods |
JP2016530277A (en) | 2013-08-30 | 2016-09-29 | モメンティブ パフォーマンス マテリアルズ インコーポレイテッド | Direct slurry phase synthesis of organohalosilanes from cyclone fine particles |
US10040689B2 (en) | 2014-12-19 | 2018-08-07 | Dow Silicones Corporation | Process for preparing monohydrogentrihalosilanes |
EP3100979A1 (en) * | 2015-06-02 | 2016-12-07 | Evonik Degussa GmbH | Treating of fines solid particles in the production of chlorosilanes by sintering at low temperatures |
KR101987129B1 (en) * | 2016-09-19 | 2019-06-10 | 한화케미칼 주식회사 | Fluidized bed reactor for composing trichlorosilane |
CN106749380B (en) * | 2017-02-23 | 2020-04-07 | 镇江江南化工有限公司 | Methyl chlorosilane monomer synthesis circulation reaction system |
CN109319790B (en) * | 2018-11-09 | 2020-11-24 | 成都蜀菱科技发展有限公司 | Method for producing chlorosilane by using fine silicon powder and chlorosilane product |
KR20220013417A (en) * | 2019-05-29 | 2022-02-04 | 와커 헤미 아게 | Method for preparing trichlorosilane from structure-optimized silicon particles |
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US4281149A (en) * | 1980-03-24 | 1981-07-28 | General Electric Company | Process for treating silicon particles within a silicone reactor system |
US4328353A (en) * | 1981-03-30 | 1982-05-04 | General Electric Company | Process for the manufacture of organohalosilanes |
JPS61236607A (en) * | 1985-04-09 | 1986-10-21 | Toray Silicone Co Ltd | Treatment of activated silicon powder |
DE19530292A1 (en) | 1995-08-17 | 1997-02-20 | Wacker Chemie Gmbh | Process for the preparation of dimethyldichlorosilane |
JPH09194490A (en) * | 1996-01-12 | 1997-07-29 | Shin Etsu Chem Co Ltd | Production of silanes |
JPH1171383A (en) * | 1997-08-29 | 1999-03-16 | Shin Etsu Chem Co Ltd | Production of alkylhalosilane |
-
2001
- 2001-04-12 DE DE10118483A patent/DE10118483C1/en not_active Expired - Fee Related
-
2002
- 2002-02-28 EP EP02004320A patent/EP1249453B1/en not_active Expired - Lifetime
- 2002-02-28 DE DE50200098T patent/DE50200098D1/en not_active Expired - Fee Related
- 2002-03-08 MY MYPI20020833A patent/MY122853A/en unknown
- 2002-04-01 CN CNB02108775XA patent/CN1164596C/en not_active Expired - Fee Related
- 2002-04-10 JP JP2002108313A patent/JP3759721B2/en not_active Expired - Fee Related
- 2002-04-10 US US10/119,626 patent/US6465674B1/en not_active Expired - Fee Related
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US20060183958A1 (en) * | 2003-04-01 | 2006-08-17 | Breneman William C | Process for the treatment of waste metal chlorides |
US20070086936A1 (en) * | 2003-07-07 | 2007-04-19 | Jan-Otto Hoel | Method for production of trichlorosilane and silicon for use in the production of trichlorosilane |
US7462341B2 (en) * | 2003-07-07 | 2008-12-09 | Elkem As | Method for production of trichlorosilane and silicon for use in the production of trichlorosilane |
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US20090016947A1 (en) * | 2006-03-03 | 2009-01-15 | Wacker Chemie Ag | Recycling of high-boiling compounds within an integrated chlorosilane system |
US8557210B2 (en) | 2006-03-03 | 2013-10-15 | Wacker Chemie Ag | Recycling of high-boiling compounds within an integrated chlorosilane system |
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US20100061911A1 (en) * | 2008-08-04 | 2010-03-11 | Hariharan Alleppey V | METHOD TO CONVERT SILICON POWDER TO HIGH PURITY POLYSILICON THROUGH INTERMEDIATE SiF4 |
US20100061913A1 (en) * | 2008-08-04 | 2010-03-11 | Hariharan Alleppey V | Method to convert waste silicon to high purity silicon |
US20100032630A1 (en) * | 2008-08-04 | 2010-02-11 | Hariharan Alleppey V | Recovery of silicon from kerf silicon waste |
US9061439B2 (en) | 2008-08-04 | 2015-06-23 | Semlux Technologies, Inc. | Recovery of silicon from kerf silicon waste |
US9067338B2 (en) * | 2008-08-04 | 2015-06-30 | Semlux Technologies, Inc. | Method to convert waste silicon to high purity silicon |
CN101440102B (en) * | 2008-12-19 | 2011-07-20 | 山东东岳有机硅材料有限公司 | Method for processing methyl monomer synthesized washing slurry |
Also Published As
Publication number | Publication date |
---|---|
EP1249453A1 (en) | 2002-10-16 |
MY122853A (en) | 2006-05-31 |
JP2003012318A (en) | 2003-01-15 |
CN1164596C (en) | 2004-09-01 |
JP3759721B2 (en) | 2006-03-29 |
DE50200098D1 (en) | 2003-12-18 |
DE10118483C1 (en) | 2002-04-18 |
EP1249453B1 (en) | 2003-11-12 |
US6465674B1 (en) | 2002-10-15 |
CN1382690A (en) | 2002-12-04 |
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