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particles (solid phase) go to the solvent (liquid 
phase) and they are removed as the excess solvent through the membrane pores. 
The size of the pores in the membrane was 5 microns. The loss of silicon after 
removal of the excess solvent was less than 1%.
1.2. Synthesis of monosilane by using alkoxysilanes
 
The procedure described in the previous section
- 
alkoxysilanes synthesis 
technology is the basis for the development of technologies of monosilane 
synthesis
, 
which is 
the next step in 
the way
of development silane technology of 
polycrystalline silicon. 
As a result of studying the processes of monosilane synthesis by catalytic 
disproportionation,
also analysis of the literature and patent data identified the 
following factors that impede to the effective i
mplementation of the process:
desire to purification of 
triethoxysilane 
obtained by the direct reaction of 
metal silicon and alcohol up to 
99.999% 
purity 
requires
complicated multi-stage 
process and 
equipment;
catalysts proposed for disproportionation process are or especially dangerous 
substances (for example, tert butoxide) or have low activity, requiring 
much
time 
for the process flowing and reducing its effectiveness
;
monosilane purification is carried out in a multistage process and as 
result, it 
lead
s to complication of structure of the equipment and increase
s production costs
;
monosilane synthesis process is a batch process. 
Studies have primarily 
were aimed
to solving these problems. As a result, we 
developed a new technology of synthesis of monosilane without these 
disadvantages and experimental installation of its implementation
(fig.1.4)
. 
Monosilane synthesis by catalytic disproportionation of triethoxysilane is as 
follows:
4SiH(OC
2
H
5
)
3
 
→ SiH
4
 + 3Si(OC
2
H
5
)
4 
(1.6)
 
After separation of ethoxysilanes
in special columns, triethoxysilane is 
collected in a special container; from this container triethoxysilane goes to 
the 
adsorber by 
dosing pump. A degree of triethoxysilane cleaning with the real 
temperature of the adsorber reaches >99.99% that is suffic
ient for monosilane 
synthesis. 
Sodium ethylate was used as a catalyst. Sodium ethylate quickly captures 
moisture from the air atmosphere. Even the standard samples of sodium ethylate 
107 

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from Sigma
-Aldrich delivered in a special container under inert gas protection 
forcedly contact with atmosphere air when the samples are loaded into a reactor 
and partially lose their activity. Therefore, the sodium ethylate preparation was 
proposed to be performed before its use in a protective environment of 
tetraethoxysilane. For a catalyst to be prepared, metallic sodium with purity of at 
least 99.9% is slowly dissolved in absolute ethanol alcohol taken in an excess 
amount exceeding the stoichiometric one by 5 times. After full dissolution of 
sodium, tetraethoxysilane is added to the solution, then ethyl alcohol is distilled off 
and the solution of just prepared sodium ethylate in tetraethoxysilane goes to the 
reactor for monosilane synthesis. The envoriment of tetraethoxysilane fully 
protects the catalyst surface from atmospheric moisture with its initial activity.