The refluxing reaction of acetone on CaC2 surface
About 100 g of acetone was added to a 250 mL three-necked
round-bottom flask and 40 g of granular CaC2 was put on the
porous glass support of the distillation column, for details
please see Fig. S1 (ESI).† The flask was heated to the boiling
state of the liquid by an electric heater and the temperature of
the liquid and vapor in the column was recorded by two thermocouples.
In the boiling state, the acetone vapor went up to
the Allihn condenser through a side pipe, and condensed
therein to its boiling liquid and dropped back to the surface of
CaC2 catalyst. In order to reduce the evaporation loss of acetone,
we used a 40% glycol aqueous solution (10 C) as the coolant
of the condenser connected to a cryogenic thermostatic bath
(DFY-10/10, Shanghai Lingbiao), and all the connecting joints
were securely sealed by PTFE sealing tape and parafilm. The
condensation reaction occurred constantly on the surface of
CaC2. The as-formed products were removed instantly from the
catalyst by the refluxing acetone to the flask, and remained
there in the whole reaction process due to their much lower
volatility than acetone and easier condensation in the side pipe
by air cooling. As such, deep condensation of acetone can be
avoided significantly. Once steady reflux had been established,
the temperatures in the flask and the reaction zone were
recorded and then the start timing for the reaction was recorded.
A syringe was used for sampling the liquid mixture at set
time intervals. The resulting water from condensation of
acetone reacts with CaC2 immediately, forming C2H2 and
Ca(OH)2. The acetylene gas was collected by a draining method
from the top of the condenser, and the Ca(OH)2 formed on the
surface of CaC2 was washed away dynamically by the down-
flowing liquid. |