JP2005119956A5 - - Google Patents

Claims (14)

In a method for producing tetrafluorosilane by decomposing hexafluorosilicic acid with sulfuric acid,
A step of decomposing hexafluorosilicic acid in sulfuric acid in a first reactor to form tetrafluorosilane and hydrogen fluoride and taking out the produced tetrafluorosilane (step 1);
Part of the sulfuric acid solution obtained in Step 1 containing hydrogen fluoride is transferred to the second reactor, and the hydrogen fluoride and silicon dioxide supplied to the second reactor are reacted to contain hexafluorodisiloxane. The step of producing tetrafluorosilane (Step 2), and the reaction product containing hexafluorodisiloxane and tetrafluorosilane obtained in Step 2 are transferred to the first reactor, and the hexafluorodisiloxane in the reaction product is fluorinated. A process for producing tetrafluorosilane, comprising a step (step 3) of reacting with hydrogen fluoride to convert to tetrafluorosilane and taking out tetrafluorosilane together with tetrafluorosilane in step 1.   Aqueous hexafluorosilicic acid and sulfuric acid were fed to the first reactor and silicon dioxide was fed to the second reactor continuously or intermittently, respectively, and tetrafluorosilane was continuously or intermittently fed from the first reactor. The manufacturing method of the tetrafluorosilane of Claim 1 taken out.   The method for producing tetrafluorosilane according to claim 1 or 2, wherein the sulfuric acid concentrations in the first reactor and the second reactor are maintained at 70 mass% or more.   The method for producing tetrafluorosilane according to any one of claims 1 to 3, wherein the reaction temperature of the first reactor and the second reactor is 60 ° C or higher.   The method for producing tetrafluorosilane according to claim 1 or 2, wherein an average particle size of silicon dioxide supplied to the second reactor is 30 µm or less.   The method for producing tetrafluorosilane according to claim 1, comprising a step of bringing tetrafluorosilane taken out from the first reactor into contact with sulfuric acid at 50 ° C. or less and absorbing and removing hydrogen fluoride contained in tetrafluorosilane. .   The method for producing tetrafluorosilane according to claim 6, wherein the tetrafluorosilane taken out from the first reactor is brought into countercurrent contact with sulfuric acid supplied to a sulfuric acid supply path to the first reactor.   The manufacturing method of the tetrafluorosilane of Claim 1 or 2 including the refinement | purification process which contacts the molecular sieving carbon and removes the impurity in the tetrafluorosilane taken out from the 1st reactor.   The method for producing tetrafluorosilane according to claim 8, wherein the impurities to be removed are at least one selected from the group consisting of hydrogen fluoride, hydrogen chloride, sulfur dioxide, hydrogen sulfide, and carbon dioxide.   The method for producing tetrafluorosilane according to claim 8 or 9, wherein molecular sieve carbon having a pore size smaller than that of tetrafluorosilane is used.   The method for producing tetrafluorosilane according to claim 10, wherein molecular sieve carbon calcinated in an inert gas atmosphere and then pretreated through high-purity tetrafluorosilane is used.   A gas for optical fiber production, comprising the tetrafluorosilane gas obtained by the production method according to any one of claims 1 to 11, wherein the contents of transition metal, phosphorus and boron are each 100 ppb or less.   A semiconductor manufacturing gas comprising the tetrafluorosilane gas obtained by the manufacturing method according to claim 1, wherein the contents of transition metal, phosphorus and boron are each 100 ppb or less.   A gas for manufacturing a solar cell, comprising a tetrafluorosilane gas obtained by the production method according to claim 1, wherein the contents of transition metal, phosphorus and boron are each 100 ppb or less.