A process for removal of impurities, in particular of dopants, from chlorosilanes which includes the following steps: (a) heating a deposition surface (3); (b) contacting the heated deposition surface (3) with at least one gaseous chlorosilane mixture, the gaseous chlorosilane mixture including at least one chlorosilane and at least one impurity, in particular at least one dopant; (c) at least partially removing the impurity, in particular the dopant, by forming polycrystalline silicon depositions on the deposition surface (3), the polycrystalline silicon depositions being enriched with the impurity, in particular with the dopant; (d) discharging the purified gaseous chlorosilane mixture; (e) contacting the heated deposition surface (3) with an etching gas to return the polycrystalline silicon depositions and the impurity, in particular the dopant, into the gas phase to form a gaseous etching gas mixture; and (f) discharging the gaseous etching gas mixture.

A cracking process for a reaction distillation of chlorosilane slurry includes feeding a chlorosilane slurry into a phase separator, drying a solid phase, feeding a chlorosilane polymer into a plate distillation column, returning kettle materials of the plate distillation column, and dividing a material produced from a top of the column. The process adopts an ionic liquid catalyst, which is environmentally friendly and reusable. The cracking and distillation of chlorosilane polymer are carried out simultaneously to shorten the time and increase the utilization rate of raw materials, which can reduce energy consumption and save costs and facilitate industrial production. A plate column is used as a distillation column, in which the two phases of the gas and liquid are sufficiently contacted. Therefore, the transfer of mass and heat is good, the production capacity is good, and the tower is not easily blocked, thereby making it easy to clean.

Metallurgical silicon containing impurities of carbon and/or carbon-containing compounds is classified and subsequently used selectively for chlorosilane production. The process comprises the steps of: a) determining the free carbon proportion which reacts with oxygen up to a temperature of 700° C., b) directing metallurgical silicon in which the free carbon proportion is ≤150 ppmw to a process for producing chlorosilanes and/or directing metallurgical silicon in which the free carbon proportion is >150 ppmw to a process for producing methylchlorosilanes. As a result of the process, metallurgical silicon having a total carbon content of up to 2500 ppmw can be used for producing chlorosilanes.

Metallurgical silicon containing impurities of carbon and/or carbon-containing compounds is classified and subsequently used selectively for chlorosilane production. The process comprises the steps of: a) determining the free carbon proportion which reacts with oxygen up to a temperature of 700° C., b) directing metallurgical silicon in which the free carbon proportion is ≤150 ppmw to a process for producing chlorosilanes and/or directing metallurgical silicon in which the free carbon proportion is >150 ppmw to a process for producing methylchlorosilanes. As a result of the process, metallurgical silicon having a total carbon content of up to 2500 ppmw can be used for producing chlorosilanes.

The invention relates to a process for the preparation of trichlorosilane (HSiCl3) which comprises the reaction of tetrachlorosilane (SiCU) with hydridosilanes in the presence of a catalyst.

A cleaning system comprise: a first pipe 20 connected to a reactor 10 used for producing polysilicon by using chlorosilane as a raw material; a heat exchanger 30 connected to the first pipe 20; a second pipe 60 provided between the heat exchanger 30 and the first pipe 20; and a driving unit 50 provided at the first pipe 20 or the second pipe 60. A cleaning liquid circulates through the first pipe 20, the heat exchanger 30 and the second pipe 60 by the driving unit 50.

A cleaning system comprise: a first pipe 20 connected to a reactor 10 used for producing polysilicon by using chlorosilane as a raw material; a heat exchanger 30 connected to the first pipe 20; a second pipe 60 provided between the heat exchanger 30 and the first pipe 20; and a driving unit 50 provided at the first pipe 20 or the second pipe 60. A cleaning liquid circulates through the first pipe 20, the heat exchanger 30 and the second pipe 60 by the driving unit 50.

Boron, phosphorus, arsenic, antimony and other impurities are at least partially removed from a mixture containing at least one chlorosilane and/or organochlorosilane by a) contacting the liquid mixture with a carrier material functionalized with an amidoxime of the general structural formula (I),

##STR00001##

where CAR=carrier material and R.sup.1, R.sup.2 are independently of one another H, alkyl, alkenyl, aryl, alkylaryl; and b) optionally removing the functionalized carrier material.

A dehydration method in accordance with an embodiment of the present invention includes: a first dehydration step of bringing hydrogen chloride gas (21) and concentrated sulfuric acid (13A) into contact with each other; and a second dehydration step of bringing hydrogen chloride gas (21A) that has been obtained through the first dehydration step into contact with concentrated sulfuric acid (13B). A concentration of the concentrated sulfuric acid used in the second dehydration step is higher than a concentration of the concentrated sulfuric acid used in the first dehydration step.

The invention relates to a method for increasing the purity of oligosilanes and/or oligosilane compounds, in which a first liquid substance mixture formed from at least 50% oligosilane compounds comprising inorganic oligosilanes and/or halogenated oligosilanes and/or organically substituted oligosilanes is provided, and the first liquid substance mixture is subjected to at least one purification sequence, wherein in a first step a) the liquid substance mixture is temperature adjusted to a temperature at which at least one fraction of the oligosilane compounds solidify, and in a second step b) at least one fraction of the liquid substance mixture is separated.