Classifications

• • C—CHEMISTRY; METALLURGY
  • C01—INORGANIC CHEMISTRY
  • C01B—NON-METALLIC ELEMENTS; COMPOUNDS THEREOF; METALLOIDS OR COMPOUNDS THEREOF NOT COVERED BY SUBCLASS C01C
  • C01B33/00—Silicon; Compounds thereof
  • C01B33/02—Silicon
  • C01B33/021—Preparation
  • C01B33/027—Preparation by decomposition or reduction of gaseous or vaporised silicon compounds other than silica or silica-containing material
  • C01B33/03—Preparation by decomposition or reduction of gaseous or vaporised silicon compounds other than silica or silica-containing material by decomposition of silicon halides or halosilanes or reduction thereof with hydrogen as the only reducing agent
• • C—CHEMISTRY; METALLURGY
  • C01—INORGANIC CHEMISTRY
  • C01B—NON-METALLIC ELEMENTS; COMPOUNDS THEREOF; METALLOIDS OR COMPOUNDS THEREOF NOT COVERED BY SUBCLASS C01C
  • C01B33/00—Silicon; Compounds thereof
  • C01B33/08—Compounds containing halogen
  • C01B33/107—Halogenated silanes
  • C01B33/1071—Tetrachloride, trichlorosilane or silicochloroform, dichlorosilane, monochlorosilane or mixtures thereof

Definitions

• the present invention relates to a method for the production of trichlorosilane by reaction of silicon with silicon tetrachloride and hydrogen gas, and silicon for the use in production of trichlorosilane from silicon tetrachloride and hydrogen.
• TCS can also be produced by reacting metallurgical grade with hydrogen chloride (HCI) gas in a fluidized bed reactor, solid bed reactor or in a stirred bed reactor. This process is generally carried out at a temperature between 250 and 1100 0 C. In the reaction, other volatile silanes than TCS are also formed, mainly STC. The amount of STC is typically about 10-85% depending on the reactor temperature, impurity content in the metallurgical silicon and any catalysts added to the reactor.
• HCI hydrogen chloride
• STC is also produced in large amounts during decomposition of TCS to pure silicon and in the redistribution reactions to produce silane (SiH 4 ) from TCS.
• STC SiH 4 + 3SiCl 4
• STC is mainly used to produce silicon dioxide (fume silica) by reacting STC with hydrogen and oxygen. Some STC is also used to produce optical fibres or sold to other applications. In general too much STC is available in the market and recycling is required to balance the production.
• the advantage of reacting STC with metallurgical silicon and hydrogen is that the by-product from the decomposition or redistribution step is recycled to TCS. Recycling will reduce the amount of silicon required to produce polysilicon since the silicon that otherwise produces STC will be converted to polysilicon. Only part of the STC can be converted to TCS in one reactor pass and maximum conversion of STC is given by the equilibrium composition. Complete conversion of the STC requires multiple reactor passes and subsequent distillations to remove TCS. Normally, the conversion of STC in one reactor pass is lower than predicted from the equilibrium composition due to the fact that reaction kinetics are important at these temperatures.
• Metallurgical grade silicon contains a number of contaminating elements like Fe, Ca, Al, Mn, Ni, Zr, O, C, Zn, Ti, B, P and others. Some contaminants will either be inert to STC, or, like Fe and Ca, form solid, stable chlorides. The stable metal chlorides will, depending on their size, either be blown out of the reactor with the silane or be accumulated in the reactor. Other contaminants like Al, Zn, Ti, B and P normally form volatile metal chlorides, which leave the reactor together with the silanes produced. O and C are enriched in slag particles of the silicon that do not react or react very slowly with STC and tend to accumulate in the reactor. The smallest slag particles can be blown out of the reactor and trapped in the filter systems.
• the present invention thus relates to a method for the production of trichlorosilane by reaction of silicon with silicon tetrachloride and hydrogen gas at a temperature between 400 and 800 0 C and a pressure of 0.1 - 30 atm in a fluidized bed reactor, in a stirred bed reactor or in a solid bed reactor, which method is characterised in that silicon containing less than 50 ppmw of manganese is added to the reactor.
• the silicon supplied to the reactor contains less than 35 ppmw of manganese.
• the present invention further relates to a method for production of trichlorosilane by reaction of silicon with silicon tetrachloride and hydrogen gas at a temperature between 400 and 500 0 C and a pressure of 0.1 to 30 atm in a fluidized bed reactor, in a stirred bed reactor or in a solid bed reactor, which method is characterized in that the amount of manganese in the reactor is kept at a maximum level of 200 ppmw, based on the weight of the silicon in the reactor.
• the amount of manganese in the reactor is kept at a maximum level of 150 ppmw based on the weight of the silicon in the reactor. It has surprisingly been found that by keeping the manganese content in the reactor at a maximum level of.200 ppmw, conversion of silicon tetrachloride, and thereby also the amount of silicon consumed, is increased.
• the present invention further relates to a method for the production of silicon containing less than 50 ppmw manganese by carbothermic reduction of quartz for use in the production of trichlorosilane by reaction of silicon with silicon tetrachloride and hydrogen gas at a temperature between 400 and
• the manganese content in the silicon produced is controlled by selecting raw materials having a low content of manganese and by using electrodes, electrode paste and electrode casings having a low content of manganese.
• the silicon may after solidification be leached, preferably with HF, HCI and/or FeCI 3 solution.
• the present invention also relates to a method for grinding and milling silicon containing less than 50 ppmw manganese for use in the production of trichlorosilane by reaction of the silicon with silicon tetrachloride and hydrogen gas at a temperature between 400 and 800 0 C, which method is characterized in that the milling and grinding are carried out using grinding bodies having a low manganese content.
• the present invention relates to the use of silicon containing less than 50 ppmw manganese for the production of trichlorosilane by reaction of silicon with silicon tetrachloride and hydrogen gas.
• Figures 1 and 2 show diagrams for theoretical conversion of STC (based on equilibrium calculation).
• FIGS. 3 to 6 show diagrams for STC conversion in a fluidized bed reactor, described as first pass STC conversion in the process of the present invention. Detailed description of the invention
• the composition of the product gas from the reactor mainly STC and TCS was measured with a gas chromatograph (GC).
• GC gas chromatograph
• Argon is used as an internal standard for the GC measurements.
• the reactivity of the samples was measured as first pass conversion of silicon tetrachloride.
• Synthetic silicon samples of highly pure silicon alloyed with 0.21% Fe, 0.12% Al and 25, 50 and 200 ppmw Mn respectively were produced in an induction furnace, milled and screened to a particle size between 125 and 180 ⁇ m (samples A, B, C).
• a silicon with a very low Mn content of 1 ppmw was produced in the same way and is identified as sample D.
• Samples A, B, C and D were used to produce trichlorosilane at 55O 0 C in a continuous laboratory fluidized bed reactor as described above.
• the STC conversion obtained with samples A, B, C and D is shown in Figure 3.
• Silicon produced by Elkem AS, Bremanger Smelteverk, containing 5 ppmw manganese was milled and screened to a particle size between 125 and 180 ⁇ m (sample E). 50 mg (1% by weight) of manganese powder was added to the reactor when about 25% of the initial silicon had been consumed.
• a synthetic silicon sample of highly pure silicon alloyed with 0.21 % Fe, 0.12% Al was produced in an induction furnace, milled and screened to a particle size between 125 and 180 ⁇ m (sample D).
• Sample D was used to produce trichlorosilane at 55O 0 C in a continuous laboratory fluidized bed reactor as described above.
• Samples E, F, G, H and I were used to produce trichlorosilane at 550°C in a continuous laboratory fluidized bed reactor as described above. Two runs were made with sample E. The STC conversion obtained with samples E through I is shown in Figure 6.

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• Chemical & Material Sciences (AREA)
• Organic Chemistry (AREA)
• Inorganic Chemistry (AREA)
• Silicon Compounds (AREA)

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Cited By (11)

Citations (2)

• 2005
  • 2005-09-22 NO NO20054402A patent/NO20054402L/no not_active Application Discontinuation
• 2006
  • 2006-09-20 WO PCT/NO2006/000320 patent/WO2007035108A1/en active Application Filing

Patent Citations (2)

Non-Patent Citations (4)

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