Catalyst Deactivation - Spent Hydroprocessing Catalysts - page 67

Figure 4.14: Effect of temperature on coke deposition (vacuum gas oil [VGO], CoMo/Al 2 O 3 ,
3MPa) [From ref. 168 . Reprinted with permission].

Figure 4.15: Effect of temperature on coke on catalyst [From ref. 205 . Reprinted with permission].

when the differences in the origin of residues and H 2 pressure as well the type of catalyst
employed used in various studies are taken into consideration.

The temperature effect on coke formation observed by Gualda and Kasztelan [145,206]
differed from that in Fig. 4.15 [205] . In the former case, the coke build-up increased and
reached a maximum before further increase in the rate of coke formation with temperature
increase was observed. The atmospheric residues used in their studies contained

110 ppm of
V+Ni, i.e., about one third of that in the residue used in the previous studies [145,206] .Onthe
other hand, in the case of the Kuwait atmospheric residue, the coke build-up increased linearly
with increasing temperature from 633 to 693 K [143,207] . These observations again confirm
that trends in the effect of temperature on the coke formation on catalyst surface depend on

∼