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Percentage of zinc transferred was also very small. On the contrary, the percentage on
tin transferred is significant and very different depending on the treatment
temperature under nitrogen.
It seems that tin can be transferred under nitrogen from activated particles to a fresh
silicon particles, the transfer being favoured by higher temperature: 4 to 5 times more
tin has been transferred during the treatment at 200 or 300°C. Amount of tin in the
+100µm fraction at the end of the reaction varies between 70 and 250ppm.
Impact of temperature and cocatalyst addition on copper transport
In this experimental section, cocatalysts tin and zinc were added together with fresh
silicon on day 2. As before, the mix of contact mass and silicon was stirred under
nitrogen at a fixed temperature.
The quantity of cocatalyst added is calculated based on the quantity of fresh silicon
added on day 2. The ratio (added cocatalyst / added fresh silicon) is the same as the
initial ratio loaded on day 1.
As tin and zinc are added to the reactor, only copper transfer can be estimated.
Table 2
: Mixing silicon and contact mass with cocatalyst under nitrogen at fixed temperature
before MCS reaction : analysis of fractions from day 1 and from day 2
Catalyst content Cu transfer
Exp Temp Cocatalyst Si Fraction
Weight
Si utiliz.
Cu Sn
Zn
Cu
(°C) added (day)
(g)
(wt%)
(wt%)(ppm) (ppm) (%)
4
25°C Sn + Zn -100µm (d1)
113g
46%
2,8 190 2090
4
25°C Sn + Zn +100µm (d2)
44g
11%
0,8 210 800
6.5%
5
200°C Sn + Zn -100µm (d1)
120g
43%
2,3 100 2170
5
200°C Sn + Zn +100µm (d2)
48g
4%
1,0 260 770
4.8%
6
300°C Sn + Zn -100µm (d1)
100g
52%
3
200 2200
6
300°C Sn + Zn +100µm (d2)
47g
6%
0,7 210 910
4.5%
Catalyst and cocatalyst content on the fraction +100ppm, is nearly the same for the 3
experiments, and does not vary based on the treatment temperature.
The composition of the fraction +100µm is significantly affected by cocatalyst
addition: compared to experiments 1-3 without cocatalyst addition, the amount of zinc
was doubled (from 400-500ppm to 800-900ppm), the amount of tin was the same as
in experiments 2 and 3 (no cocatalyst addition, T = 200-300°C). However, copper
transport was not significantly improved by cocatalyst addition (from 3-6% to 5-6%
of Cu transferred).
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