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Specific procedure
The reaction proceeds over 2 days.
On the first day, contact mass of 210g of silicon (0-100µm), and the catalytic species
copper (as CuCl) , zinc and tin (as bronze) added as solid powders are mixed for 20
minutes. The contact mass is loaded into the reactor and maintained under the
experimental procedure described above over a period of 7 hours. During runs,
condensed MCS are collected every hour and analysed by gas chromatography. After
7 hours, the temperature is decreased and the reactive mass is maintained over night at
room temperature under nitrogen.
Day 1 procedure is the same for all the experimental study. The same silicon powder
(same impurities and size distribution 0-100 µm) and the same catalyst quality were
used for all experiments. Around 50g of silicon is converted during day 1.
On the second day, 50g of silicon (125-160µm) are loaded to the reactor. Specific
conditions are used for a period of 2 hours before the reaction is restarted under the
same conditions as in day 1. After 7h reaction with sampling as in day 1, the reaction
is stopped and the mass is cooled under nitrogen. The two fractions – the one from
day one and the one from day 2 - are separated by sieving and characterized.
Day 2 conditions will change for each experiment: contact mass from day 1 and fresh
silicon will be mixed in specific conditions of temperature, cocatalyst addition…
The experimental procedure can be summarized as follows :
Characterization methods
Liquid samples
are collected at every hour and analysed by gas chromatography
.
From GC analysis and mass balance, we can define the following criteria:
Silicon consumption rate:
quantity of silicon converted during the reaction. It is
determined from mass balance on silicon in the outlet condensed gas, analyzed by
GC. It is expressed in weight percent.
Productivity:
Is the methylchlorosilanes mass flow-rate produced per kilo of silicon
initially loaded in the reactor (g MCS/(kg.h)).
Dimethyldichlorosilane
selectivity:
Is
the
weight
percentage
of
dimethyldichlorosilane in the total sample of methylchlorosilanes produced.
Day 1
210g Si 0-100µm
+ catalysts
+7 hours reaction
(MeCl, T)
Day 2
Reacted mass from day 1
+ 50g Si 125-160µm
+ 2h specific conditions
+
7 hours reaction
(MeCl, T)
Post reaction
Sieving
Reacted mass from day 1 /
Reacted mass from day 2
+ analysis of the 2 fractions
(weight, ICP, SEM)
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