Sulfation reaction or CuO/γ-alumina sorbent can be classified into three types in terms of the amount of sulfate ions present on the support namely, surface, slightly deep, and bulk sulfations as a function of reaction temperature and CuO loading.
The effects of regeneration temperature, types of sulfate and the number of sulfation-regeneration cycles on the regeneration characteristics have been determined in a thermogravimetric analyzer (TGA). The reductions of sulfate on copper and alumina sites occur above 300℃ and 400℃ respectively with 5 vol%-$H_2$. Sulfur compounds produced from the regeneration reaction are $SO_2(＜450℃)$ and $H_2S(＞450℃)$. Residual sulfate is observed in all the sorbents after the regeneration at 300 ~ 500℃. The amount of residual sulfate decreases with increasing temperature upto 450℃ but, it remains constant with a further increase in temperature upto 500℃. The amount of residual sulfate in surface sulfation is larger than that in bulk sulfation due to strong interaction between $SO_2$ and alumina. In the sulfation-regeneration cycle reaction, residual sulfate is accumulated up to 4th cycles however, the accumulation does not proceed further with increasing the cycle up to 10 times with the sulfation activity of 3th cycles.
The inhibiting effect of $SO_2$ on the regeneration reaction of sulfated sorbent have also been determined with variation of $SO_2$ concentration. The regeneration reaction is inhibited largely with $SO_2$ concentration. The evidences of inhibition are the low initial reaction rate and lower pseudoequilibrium in the regeneration reaction. For lower $SO_2$ concentrations, weight gain occurs after rapid initial weight loss.
After bulk sulfation, surface area and pore volume of the sulfated sorbent are smaller compared with the fresh sorbent. Surface area and pore volume of the regenerated sorbent increase with increasing reduction temperature.
