Effect of solid acid catalysts on blended primary and tertiary amines systems

“The effect of the amount of acid catalysts including Ȗ-Al2O3 and HZSM-5 on cyclic capacity of solution 5 M
MEA+2 M MDEA is shown in Fig. 5 while the effect of the catalysts on the cyclic capacity of 5 M MEA+1.25 M
DEAB is illustrate in Fig. 6. Similar effect of the catalysts can be seen in both amine mixtures. An increase in the
amount of catalyst contributed to a higher cyclic capacity. This is because the solid acid catalysts provide a low
energy barrier pathway. Comparing between Ȗ-Al2O3 and HZSM-5, HZSM-5 which the majority of its acid sites are
Bronsted sites has a higher performance in increasing the cyclic capacity compared to Ȗ-Al2O3 which is Lewis acid
catalyst [8].
Fig. 7 illustrates the effect of amine types and catalysts on absorption efficiency. It is a plot of the absorption
efficiency obtained from different amine mixtures (5 M MEA, 5 M MEA/ 2 M MDEA, and 5 M MEA/ 1.25 DEAB)
contacting different catalysts (Ȗ-Al2O3 and HZSM5) against the catalysts weight. The absorption efficiency of all
three amine mixtures increased with increasing catalyst weight. Comparing between three amine mixtures, MEA
had the lowest absorption efficiency. This is a reflection of the higher cyclic capacity of MEA/MDEA and
MEA/DEAB than MEA. The effect of catalysts on absorption efficiency in MEA/MDEA and MEA/DEAB systems
is not as significant as in MEA system.
Fig. 8 shows the effect of amines mixtures (5 M MEA, 5 M MEA/ 2 M MDEA, and 5 M MEA/ 1.25 DEAB)
and catalysts (Ȗ-Al2O3 and HZSM-5) on heat duty. It can be noticed that the heat duty of 5 M MEA decreased
significantly with the increase of catalyst weight while only slight effect of acid catalyst was seen in the mixed
amine systems (MEA/MDEA and MEA/DEAB). This is because in mixtures of primary and tertiary amine there is
HCO3- that helps facilitate the desorption process. Therefore, the heat duty is already low without the existence of
the catalysts.”


Leave a Comment