Rhone-poulenc Specialites Chimiques

Serge Jacubert

Jean Grosbois

Philippe Nataf

Jean-Michel Verdier

Jean-Yves Dumousseau

Bernard Boudot

Eric Le Roux

Shaped articles, e.g., bars, of semiconductor-grade, ultra-pure silicon, are facilely and efficiently produced by thermally decomposing/pyrolyzing a monosilane feedstream on a red-heated silicon support member, whereby high purity silicon is deposited thereon, and thence recycling the majority of the by-product reaction admixture into said monosilane feedstream.

Production of shaped articles of ultra-pure silicon

Shaped articles, e.g., bars, of semiconductor-grade, ultra-pure silicon, are facilely and efficiently produced by thermally decomposing/pyrolyzing a monosilane feedstream on a red-heated silicon support member, whereby high purity silicon is deposited thereon, and then recycling the majority of the by-product reaction admixture into said monosilane feedstream.

Lithium metal is continuously prepared, in specially adapted electrolytic cell, by (i) continuously electrolyzing a mixture of molten salts including lithium chloride, said mixture comprising the medium of electrolysis, (ii) continuously withdrawing admixture of product lithium metal with said mixture of molten salts, and (iii) continuously discharging formed chlorine gaseous phase therefrom, wherein the medium of electrolysis is maintained at a temperature ranging from the melting point of said mixture of molten salts, at the eutectic composition thereof, to 400.degree. C., and said gaseous chlorine phase is maintained at a temperature not exceeding 300.degree. C.

Continuous production of lithium metal by electrolysis of lithium

Lithium metal is continuously prepared by, in a specially adapted electrolytic cell, (i) continuously electrolyzing the lithium chloride which comprises a mixture of molten salts, which mixture comprises the medium of electrolysis and such medium of electrolysis naturally circulating within an interspace defined between the electrodes of the cell, said interspace being devoid of physical barrier between said electrodes, (ii) continuously withdrawing therefrom product lithium metal in admixture with the mixture of molten salts, and (iii) continuously discharging undiluted chlorine gas therefrom.

Continuous electrolysis of lithium chloride into lithium metal

Lithium is continuously converted into lithium hydride, is suitable phase contactor/decanter apparatus, by continuously hydrogenating in a first reaction zone, at elevated temperatures, an agitated intimate admixture of metallic lithium in a mixture of molten salts, continuously discharging the effluent of said hydrogenation reaction to a second zone of decantation, whereby said effluent is separated into a floating light phase essentially consisting of unreacted lithium metal and a heavy phase which comprises product lithium hydride dissolved in said mixture of molten salts, continuously recycling floating light phase back to the hydrogenation reaction zone, continuously withdrawing heavy phase from said zone of decantation, and recovering product lithium hydride from said withdrawn heavy phase.

Continuous hydrogenation of lithium into lithium hydride

Silane, SiH.sub.4, is continuously produced in an integrated process, by continuously (i) reacting a chlorosilane with the lithium hydride recycled in a base mixture of molten salts comprising lithium chloride and at least one other alkali or alkaline earth metal chloride, in a discrete first reaction zone, (ii) recovering silane product from said first reaction zone, (iii) cycling the silane depleted product of reaction from said first reaction zone, which comprises said base mixture and the additional amounts of LiCl produced in said first reaction zone, to a discrete electrolysis second reaction zone, (iv) electrolyzing lithium chloride comprising said first zone reaction product in said electrolysis second reaction zone, (v) recovering chlorine gas from said electrolysis second reaction zone, (vi) cycling the chlorine depleted product of electrolysis from said second reaction zone, which comprises said base mixture and the lithium metal produced in said electrolysis second reaction zone, to a discrete hydrogenation third reaction zone, (vii) hydrogenating the lithium metal comprising said second zone reaction product in said hydrogenation third reaction zone, and (viii) recycling the product of reaction from said hydrogenation third reaction zone, which comprises said base mixture and the first zone reactant lithium hydride produced in said hydrogenation third reaction zone, to said first reaction zone.

Continuous preparation of silane, SiH.sub.4

Essentially pure silane, SiH.sub.4, is facilely prepared in plural reactors, by (i) reacting chlorosilane with lithium hydride in a mixture of molten salts which comprises lithium chloride and potassium chloride, in a discrete first reaction zone, said mixture of molten salts being essentially eutectic in composition, the amount of chlorosilane being at least 5% less than that amount stoichiometrically required for reaction with the lithium hydride, and the amount of lithium hydride comprising at most 20 mole % of said mixture of molten salts, (ii) recovering product silane from said discrete first reaction zone, (iii) transferring said mixture of molten salts comprising unreacted lithium hydride dissolved therein from said discrete first reaction zone to a discrete second reaction zone, (iv) reacting chlorosilane with said unreacted lithium hydride dissolved in said mixture of molten salts in said discrete second reaction zone, the amount of chlorosilane being at least 2% in excess of that amount stoichiometrically required for reaction with said unreacted lithium hydride, and (v) recovering product silane from said discrete second reaction zone.

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Viroflay, France

Serge Jacubert