Abstract:
The Catalytic conversion of synthesis gas (a mixture of
CO:./CO/H.) to
methanol is an
important
industrial process.
The zinc promoted Raney Copper
catalyst
produced by partial
leaching was
found to produce
yields of
methanol double to
that obtained
on a commercial
catalyst.
The importance of
-methanol as
a clean synthetic
fuel and
chemical feedstock
has led to
wide spread interest in improving economics of
product ion.
In this investigation Al-33.1 wt% Cu-17.6 wt% Zn and Al-32.4 wt% Cu-9.3 wt% Zn alloys were prepared and subjected for leaching at various temperatures ( 30,40 and 50"c) and different aqueous -sodium hydroxide concentration ( 20 , 30 and 40 wt% ) at a constant time of one hour. The leaching mechanism in the above alloy systems are studied with the help of Scanning Electron Microscope (SEM), X-ray diffraction studies and Electron Probe Micro Analysis (EPMA).
It is observed from the X-ray analyses and Micro Probe results that the two phases CuAl and solid solution of Aluminium are present in the as-cast alloys, whereas in leached alloy Cu and Cu•:,,O phases are present in the alloy.
Coring effect has been observed in the solid solution of Aluminium containing Copper and Zinc. .
For both alloys, the leached thickness increased with increase in temperature and sodium hydroxide concentration.
While leaching, solid solution of Aluminium is leached out. This is due to the electrode potential difference developed between the two phases. These two phases are electrically short circuited through the body of the alloy. As soon as the alloy is in contact with the aqueous sodium hydroxide solution, local cell action takes place and dissolution takes place at anode.
It is observed from the Electron Probe Microscopic Analysis, that the concentration of Aluminium. and Zinc decreased uniformly in the leached region, where as the amount of Copper is proportionally high. It is also observed that Aluminium is leached out from CuAl: phase
