Next, the substance will
pass through the drying process after impregnation to remove solvents from the
support. The drying rate has to be well control in order to produce a good performance
catalyst. It cannot not be too slow as the metal salts will disperse in the
pores of support. However, it also cannot be too high as precipitation will
form on the outer surface of the support. There are a total of four different
categories of metal profiles during the dispensation of the active metal in the
support, it includes uniform, egg-shell, egg-white and egg-yolk. The selection
on the metal profiles is determined by the required activity and selectivity of
the reaction. Factors that will affect the drying process include rate of
heating process, degree of liquid saturation, liquid viscosity, volume of pores
and distribution of pore size.
The substance will then send to calcination process where
gas-solid and solid-solid surface reaction will take place. Calcination is a
further heat treatment process which able to decompose the active metal with formation
of an oxide and remove the gaseous products from the reaction. During this
process, a sintering of the active metal and a reaction of the meal oxide with
the support can occur. Moreover, oxidation in this process will able to reduce
the size of the metal particles and this will eventually affect the dispersion
of metal on the nano-scale level.
Lastly, the final process of the manufacturing of
industrial catalyst will be the filtration process. It is knowns as the more
common solid-liquid separation process which used to precipitate and
crystallize catalyst in the production of catalyst. In this process, separation
of the chemical substance will be achieved by forcing the particulate
suspension through a filter membrane with pressure drive or vacuum-driven flow.
The filter cake will formed from the solid particles accumulated over tine one the
filter membrane. The removal of residual electrolytes will normally achieved by
subsequently washing the filter cake.