Patent GB-1009703-A (GB)
Title: Improvements in and relating to the preparation of hydrogen-containing compounds of groups ó¾ú¼ó¶ and of the periodic table
IPC: C25B9/19
Filed: 1962-04-10
Abstract: <PICT:1009703/C6-C7/1> Hydrogen containing compounds of Group III, IV or V are made by electrolysing a non-oxidizing melt containing halides of alkali and alkaline earth metals to give a metal, removing the metal to another zone also containing the melt and reacting the metal with hydrogen at a temperature high enough to form but not <PICT:1009703/C6-C7/2> decompose the hydride, removing the hydride dissolved in the melt to another zone and contacting it with a halogen containing compound of element of Group III, IV or V at a temperature above the melt freezing point but below product decomposition temperature. Examples of hydrogen containing compounds are NH3, N2H4, SiH4, B2H6, GeH4 and PH3. The melt may be a binary or ternary mixture, e.g. Li, Na, K, Rb, Cs, Ca, Sr, Ba, as fluorides, chlorides or bromides but LiCl-KCl is preferred. The halogen containing compounds may be BCl3, GeCl4, PCl3 and SiCl4, the latter may be made in situ by reaction of silicon with chlorine, e.g. that produced by electrolysing the melt.  In a specific embodiment for producing silane, Fig. 2, a melt of 45% LiCl +55% KCl is maintained between melt freezing point and 500  DEG C. and electrolysed in chamber 28 by cathode 26 which passes through an insulating sleeve 27, the sleeve 39 of a closed heat-resistant container 20 and anode vessel 24, through a ceramic diaphragm 29 and into chamber 28.  The anode chamber 24 contains silicon 6 as anode surrounded by a graphite ring 23 connected to electric lead 21 insulated by sleeve 22.  Li metal produced at 26 rises through pipe 30 to the hydriding chamber 32 which contains melt maintained at 450-625  DEG C., where the metal is converted into LiH by H2 introduced through tube 37. SiCl4 produced at anode 6 rises up pipe 31 to hydrogenating chamber 33 maintained between melt freezing point and 500  DEG C., where it meets the lithium hydride-rich melt from chamber 32 and is converted into SiH4.  Since chambers 32 and 33 are maintained at relative high and low temperatures respectively by conventional heaters, the melt circulates up pipe 34, down 33, and back up 35 to 32.  In another embodiment, Fig. 3 (not shown), a similar arrangement of pipes is used but the container is divided vertically by a porous diaphragm of electrically insulating material to give two compartments one of which has a base-introduced cathode and the other containing lump silicon lying on an anode contact plate to which electrical connection is made by a lead-in sheathed in an insulating sleeve.  A simpler embodiment, Fig. 1 (not shown), is N-shaped with the electrodes situated at its extremities. In Fig. 4, the cell wall 64 serves as a cathode and the metal rises between 65 and 64 passing through pipe 66 into hydriding cell 67 containing melt.  Hydrogen introduced through 69 reacts with the metal and the mixture of melt and hydride passes through connection 72 to hydrogenating chamber 70, due to the temperature differential between 67 and 70, where SiCl4 is introduced through pipe 71.  Pipes 73, 75 and 76 act as recirculation pipes for the melt.  Chlorine produced by graphite anode 61 attached to the sleeve insulated electrical lead-in 63 and 62, passes to lump silicon 85 where SiCl4 is produced.  The silicon chloride passes through trap 80, condenser 81, liquid seal 83 and evaporator 82 and into pipe 71.  In another embodiment, Figs. 5 and 6 (not shown), two pairs of reaction chambers are provided wherein one of each pair is equipped with an anode and a cathode and means for introducing or venting gas whilst the various reaction chambers are connected to one another by pipes. The electrolysis cells are operated alternatively as the composition of the melt changes.ALSO:<PICT:1009703/C3/1> <PICT:1009703/C3/2> Organic hydrosilanes are made by electrolysing a non-oxidizing melt containing halides of alkali and alkaline earth metals to give a metal, removing the metal to another zone also containing the melt and reacting the metal with hydrogen at a temperature high enough to form but not decompose the hydride, removing the hydride dissolved in the melt to another zone and contacting it with an organic chlorosilane at a temperature above the meltfreezing point but below product decomposition temperature. The conversion of dimethyl-silicon dichloride to dimethyl-silane is mentioned. The melt may be a binary or ternary mixture, e.g. Li, Na, K, Rb, Cs, Ca, Sr, Ba, as fluorides, chlorides or bromides but LiCl-KCl is preferred.  In a specific embodiment for producing silane, Fig. 2, a melt of 45% LiCl+ 55% KCl is maintained between melt-freezing point and 500 DEG  C. and electrolysed in chamber 28 by cathode 26 which passes through an insulating sleeve 27, the sleeve 39 of a closed heat-resistant container 20 and anode vessel 24, through a ceramic diaphragm 29 and into chamber 28.  The anode chamber 24 contains silicon 6 as anode surrounded by a graphite ring 23 connected to electric lead 21 insulated by sleeve 22.  Li metal produced at 26 rises through pipe 30 to the hydriding chamber 32 which contains melt maintained at 450-625 DEG  C., where the metal is converted into LiH by H2 introduced through tube 37.  SiCl4 produced at anode 6 rises up pipe 31 to hydrogenating chamber 33 maintained between meltfreezing point and 500 DEG  C., where it meets the lithium hydride-rich melt from chamber 32 and is converted into SiH4. Since chambers 32 and 33 are maintained at relative high and low temperatures respectively by conventional heaters, the melt circulates up pipe 34, down 33, and back up 35 to 32.  In another embodiment (Fig. 3, not shown), a similar arrangement of pipes is used but the container is divided vertically by a porous diaphragm of electrically insulating material to give two compartments one of which has a base-introduced cathode and the other containing lump silicon lying on an anode contact plate to which electrical connection is made by a lead-in sheathed in an insulating sleeve.  A simpler embodiment (Fig. 1, not shown), is N-shaped with the electrodes situated at its extremities.  In Fig. 4, the cell wall 64 serves as a cathode and the metal rises between 65 and 64 passing through pipe 66 into hydriding cell 67 containing melt. Hydrogen introduced through 69 reacts with the metal and the mixture of melt and hydride passes through connection 72 to hydrogenating chamber 70, due to the temperature differential between 67 and 70, where SiCl4 is introduced through pipe 71.  Pipes 73, 75 and 76 act as recirculation pipes for the melt.  Chlorine produced by graphite anode 61 attached to the sleeve insulated electrical lead-in 63 and 62, passes to lump silicon 85 where SiCl4 is produced. The silicon chloride passes through trap 80 condenser 81, liquid seal 83 and evaporator 82 and into pipe 71.  In another embodiment (Figs. 5 and 6, not shown), two pairs of reaction chambers are provided wherein one of each pair is equipped with an anode and a cathode and means for introducing or venting gas whilst the various reaction chambers are connected to one another by pipes.  The electrolysis cells are operated alternatively as the composition of the melt changes.ALSO:Hydrogen containing compounds of Groups III, IV or V are made by electrolysing a nonoxidizing melt containing halides of alkali and alkaline earth metals to give a metal, removing the metal to another zone also containing the melt and reacting the metal with hydrogen at a temperature high enough to form but not decompose the hydride, removing the hydride dissolved in the melt to another zone and contacting it with a halogen containing compound of element of Groups III, IV or V at a temperature above the melt freezing point but below producr decomposition temperature. Examples of hydrogen containing compounds are NH3, N2H4, SiH4, B2H6, GeH4 and PH3.  The melt may be a binary or ternary mixture, e.g. Li, Na, K, Rb, Cs, Ca, Sr, Ba, as flourides, chlorides or bromides, but LiCl-KCl is preferred.  The halogen containing compounds may be BCl3, GeCl4, PCl3 and SiCl4, the latter may be made in situ by reaction of silicon with chlorine, e.g. that produced by electrolysing the melt.  In a specific embodiment for producing silane, Fig. 2, a melt of 45% LiCl + 55% KCl is maintained between melt freezing point and 500 DEG  C. and electrolysed in chamber 28 by cathode 26 which passes through an insulating sleeve 27, the sleeve 39 of a closed heat-resistant container 20 and anode vessel 24, through a ceramic diaphragm 29 and into chamber 28. The anode chamber 24 contains silicon 6 as <PICT:1009703/C1/1> <PICT:1009703/C1/2> anode surrounded by a graphite ring 23 connected to electric lead 21 insulated by sleeve 22. Li metal produced at 26 rises through pipe 30 to the hydriding chamber 32 which contains melt maintained at 450-625 DEG  C., where the metal is converted into LiH by H2 introduced through tube 37. SiCl4 produced at anode 6 rises up pipe 31 to hydrogenating chamber 33 maintained between melt freezing point and 500 DEG  C., where it meets the lithium hydriderich melt from chamber 32 and is converted into SiH4.  Since chambers 32 and 33 are maintained at relative high and low temperatures respectively by conventional heaters, the melt circulates up pipe 34, down 33, and back up 35 to 32.  In another embodiment (Fig. 3, not shown) a similar arrangement of pipes is used but the container is divided vertically by a porous diaphragm of electrically insulating material to give two compartments one of which has a base-introduced cathode and the other containing lump silicon lying on an anode contact plate to which electrical connection is made by a lead-in sheathed in an insulating sleeve. A simpler embodiment (Fig. 1, not shown) is N-shaped with the electrodes situated at its extremities.  In Fig. 4, the cell wall 64 serves as a cathode and the metal rises between 65 and 64 passing through pipe 66 into hydriding cell