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Fig.1.4. General view of the experimental setup for the implementation of the process of 
synthesis of monosilane 
The catalytic disproportionation of triethoxysilane is performed in a reactor 
where the catalyst solution - 
sodium ethylate dissolved in tetraethoxysilane in 1:15 
proportions - 
is fed from the bottom. The ratio of catalyst solution and 
triethoxysilane in our experiments was between 1:10 and 1:20. The use of just 
prepared sodium ethylate as a catalyst makes it possible to reduce the contact time 
more than 5 times. The monosilane synthesis reaction was performed at a 
temperature ranging from 0 to 50 C at a pressure of 1 to 2 bar. Sodium ethylate 
from Sigma
-
Aldrich was used for comparison. The results obtai
ned under different 
conditions of monosilane synthesis are shown in Table. 1.
The results showed the high efficiency of the just prepared catalyst of sodium 
ethylate. 
 
108 

---

Table 1 
The experimental results of monosilane synthesis 
Further, for realization of the continuous process of synthesis, triethoxysilane 
was fed into the reactor at the constant rate of 200 mL per hour with a dosing 
pump GRUNDFOS® DME 60
-
10 AR. Gas
-chromatographic control of the 
samples fro
m the reactor showed that the content of triethoxysilane in the reaction 
mixture remained constant within ± 5%. Gaseous monosilane was continuously 
withdrawn into the collector where it was condensed on the collector walls cooled 
by liquid nitrogen. Moreover, at the reactor outlet gaseous monosilane passed 
through an adsorption trap where it was freed from ethoxysilane vapors. From the 
collector liquid monosilane was directed to further purification on the absorber 
where triethoxysilane cooled below 
-140
о
С
was used as an absorbent. The contact 
time in the absorber was 15 minutes. Then monosilane was separated from 
triethoxysilane at 
-
80° C. Purified monosilane was directed into a reservoir for 
accumulation. 
Thus, the proposed technical solutions for the monosilane synthesis allows:
- increasing the productivity of the technological process by reducing the 
contact time of the reactants more than 5 times;
- 
maximizing the conversion of triethoxysilane;
- ensuring the monosilane synthesis reaction in a continuous mode with the 
high and stable rate of synthesis. 
1.3. Growth of polycrystalline silicon
 
by monosilane
 
Monosilane was directed from the collector to the reactor through the gas 
distribution system for growing the rods on the surface of seeds made of high-
purity silicon. A pyrolysis method - thermal decomposition of monosilane - was 
used to obtain polycrystalline silicon. The process follows the following scheme:
SiH
4
 
→ Si + H
2
 
(1.7)
 
Thermal decomposition of monosilane starts at a temperature of 450°C and 
r
eaches 100% decomposition of molecules at 950°C. The rod temperature is given 
by direct resistive heating of the silicon rod - 
seed. The optimal temperature is 
850°C for which the rate of crystal growth was 0.4 kg / m
2
•hr and monosilane