Handbook of Solvents - George Wypych - ChemTech - Ventech!

1530 Klaus-Dirk Henning
Figure 22.1.16. Surface reaction of cyclohexanone on activated carbon (After reference 25).
Figure 22.1.17. Surface reaction of methyl ethyl ketone on activated
carbon (After reference 25).
During adsorption of methyl
ethyl ketone in the presence of oxygen,
some catalytic surface reactions
occur (Figure 22.1.17). The
reaction products are acetic acid,
di-acetyl, and presumably also
di-acetyl peroxide. Di-acetyl has
an intensive green coloration and
a distinctive odor. Important for
the heat balance of the adsorber is
that all of the reactions are strongly exothermic.
Unlike the side products of cyclohexanone, acetic acid the reaction product of the
MEK (corrosive!) will be removed from the activated carbon during steam desorption. Adsorption
performance is thus maintained even after a number of cycles.
Operators of ketones recovery plants should adhere to certain rules and also take some
precautions 25
• Adsorption temperature should not be higher than 30°C (the surface reaction rates
increase exponentially with temperature).
• The above requirement of low-adsorption temperatures includes:
a) adequate cooling after the desorption step;
b) a flow velocity of at least 0.2 m/s in order to remove the heat of adsorption.
Since ketones will, even in an adsorbed state, oxidize on the activated carbon due to
the presence of oxygen, these further precautions should be taken:
• keep the adsorption/desorption cycles as short as possible,
• desorb the loaded activated carbon immediately at the lowest possible temperatures,
• desorb, cool and blanket the equipment with inert gas before an extended shut down.