Catalysis 2024 Issue

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Moles SOx added to batch

SO(g) BaO

MgO SO(g)

CaO Rare earth oxide

SO(g) BaSO

MgSO SO(g)

CaSO Rare earth sulphate

Figure 2 Order of sulphation of vanadium traps. Rare earth is least susceptible to sulphating

earth oxides, which prevents the passivation of vanadium. Figure 2 shows a thermodynamic calculation performed by BASF where increasing amounts of SOx are added to a batch containing Ba, Ca, Mg, and rare earth oxides, finding that sulphation occurs in that order. This calculation demon- strates that vanadium traps using rare earth are more toler- ant to sulphur at regenerator conditions than the alternative alkaline earth oxides that more readily sulphate. Based upon this finding, BASF commercialised its pro - prietary Valor rare earth-based vanadium passivation tech- nology with the goal of improving vanadium passivation through increased sulphur tolerance. Figure 3 shows the results of a study in which a conventional alkaline earth- based V-trap and the rare earth-based V-trap Valor were both exposed to SOx in laboratory deactivation conditions. The samples were then analysed for vanadium and sul- phur uptake using scanning electron microscopy (SEM) and imaging software for quantification. As seen in Figure 3, the Valor vanadium trap contains significantly less sulphur following the deactivation procedure. It contains noticeably

higher levels of vanadium, confirming that a rare earth-based V-trap is more effective in passivating vanadium because of improved tolerance to sulphur. The impact on FCC catalyst performance because of Valor can be seen in Figure 4. Laboratory cracking evaluations of FCC catalysts deactivated in the presence of metals (3,000 ppm V and 3,000 ppm Ni), one containing a rare earth- based catalyst (Valor) and the other containing an alkaline earth-based catalyst, shows that the catalyst using a rare earth-based vanadium passivation technology maintains significantly higher activity at comparable catalyst-to-feed ratios (cat/oil). The only difference in these catalyst designs is the vana- dium passivator used. Thus, this higher activity can be attributed to improved vanadium passivation technology. This laboratory-scale experiment demonstrated that the improved sulphur tolerance of a vanadium passivator can result in increased activity maintenance in the presence of vanadium contaminant. Vanadium passivation in FCC unit trials While performance in laboratory testing provides insight into strategies for guarding against vanadium contamination

Valor Existing V-passivation technology

Cat/oil

Figure 4 Laboratory testing results of FCC catalyst deactivated to levels of 3,000 ppm V and 3,000 ppm Ni. Cat/ oil equals amount of FCC catalyst vs amount of FCC feed

Figure 3 Sulphur and vanadium present the displayed deactivation. Brighter areas indicate higher concentrations

Catalysis 2024