Catalysis 2025 Issue

present only if nitrogen is (almost) completely removed. This typically occurs in applications with a PPH₂ outlet above 35-40 bar (500-580 psig), where the entire reactor, including the bottom section, operates in the green region. Zone 1, at the top, is usually affected by the inhibitory effect on HDS by refractory nitrogen and PNAs, which is particularly strong at moderate pressure and when upgrad- ing distressed and cracked feedstock. A catalyst with high DDS selectivity is preferred in Zone 1 unless PPH₂ is high enough for the inhibition effects to be sufficiently low. Zone 2 is the part of the reactor where the inhibition by nitrogen and PNAs is low enough for the HYD function to become effective. In this zone, a catalyst with higher HDN activity and HYD selectivity is preferred when operating in the green regime, as it can lower nitrogen more quickly and is more effective at removing refractory sulphur to meet ULSD specifications. Conversely, in the yellow and red regimes, a higher DDS-selective catalyst is necessary. Note that operations at low or medium pressure with a very high intake of cracked feedstock usually do not reach Zone 3. Zone 3 is reached only if product nitrogen is low enough, typically close to zero ppmwt when operating at low and medium pressure. The benefit of Zone 3 compared to Zone 2 is the drastically reduced inhibition on hydrogenation reactions, which boosts HDS and HDA activity, thereby maximising volume swell. Since Zone 3 requires favourable thermodynamic conditions for hydrogenation, it can only exist when the bottom section of the reactor operates in the green region (Figure 1). Note that Zone 3 is easier to reach in the earlier part of the operating cycle, when the weighted average bed temperature (WABT) is lower and the HYD and HDN/HDS selectivity of the catalyst is higher. KF 787 has very high DDS selectivity and delivers supe- rior HDS and HDN activity and stability in both low- and medium-pressure applications, allowing the processing of a wide range of feedstocks, including straight-run gasoil (SRGO) and cracked feedstock. KF 787 is suited for any zone of the reactor. Depending on H₂ availability, it can be applied standalone or in combination with KF 774, with

Guard Removes particulates & poisons Starts saturating olens Zone 1 Saturates olens & converts easy S (DDS) Starts converting N & PNAs to Di-/Mono-As ( HYD ) Zone 2 Converts hard S (HYD / DDS) Converts N & PNAs to Di-/ Mono-As (HYD) Zone 3 (Nitrogen-free zone ) Boosts removal of hard S (HYD) Saturates part of Mono-As (HYD) Zone 3 is typically reached only at high enough pressure (PPHout ≥ 35-40 bar/500-580 psig)

Log S, N

Guard

Zone 1

Zone 2

S < 10 ppm

Zone 3

illustrates the results of a statistical analysis of the metal slab lengths measured using 3D scanning transmission electron microscopy (3D-STEM) after testing KF 787 along- side reference catalyst KF 757. The 40-day activity test was conducted to produce ultra-low sulphur diesel (ULSD) while feeding cracked feedstock at low pressure, including the red operating regime (Figure 1), with temperatures as high as 380°C/715°F. Despite the severe operating con- ditions, the small size and the excellent dispersion of the metal slabs in KF 787 were very well preserved. The benefits of applying KF 787 and KF 774 in distillate applications can be explained by considering the reac- tions occurring in a diesel hydrotreater and by recalling the observations on the operating regimes and the effect on the catalyst properties on performance, as discussed in the previous sections. As illustrated in Figure 4 , two or three operating zones exist in a distillate hydrotreater below the guard bed section. The third zone at the reactor bottom is Figure 4 Reactor zones and the function of DDS vs HYD activity in distillate hydrotreaters

385

Cumulative LCO processed (rel%)

142% 100% 42%

380

KF 787

375

KF 757

370

KF 757

TOS

365

KF 787 vs KF 757 cycle

360

Same PPH outlet: 36 bar (520 psig) Feed N : 250 vs 180 ppm Feed density : 860 vs 852 g/l ( 33.0 vs 34.6 ˚API) Same LCO properties Avg LCO : 11.2 vs 7.9 wt% 6.5˚C / 12˚F lower SOR normalised WABT 42% more LCO processed

KF 787

6.5˚C

Norm WABT KF 757 Norm WABT KF 787 P ulsar

355

350

TOS

Figure 5 Low-to-medium pressure KF 787 commercial case: 6.5°C /12°F lower normalised SOR WABT and 42% more LCO processed

Catalysis 2025