Catalysis 2025 Issue

The third case consists of a high-pressure ULSD hydro- treater, operating with an outlet PPH₂ of 66 bar/960 psig and processing a feedstock primarily composed of SRGO, LCO, and coker gasoil (CGO). The unit is hydrogen- constrained due to limitations of the make-up gas compres- sor. The primary objective is to extend cycle length to consist - ently achieve a five-year cycle while also increasing volume swell. This is being accomplished by applying a NiMo/KF 774 catalyst Stax configuration. KF 774 has been positioned at the reactor bottom with the dual objective of maximising HDS activity without consuming too much hydrogen and safeguarding stability for the entire five-year cycle. The catalyst system has successfully achieved both objec - tives thus far in the cycle. This is highlighted in Figure 6 by the 3.5°C/6°F lower SOR WABT, 0.1°C/0.2°F lower monthly deactivation rate, and the 2.7 g/ml/0.8°API volume swell increase compared to the first 15 months on stream of the previous cycle, which was loaded with NiMo/KF 780. The unit is expected to exceed the five-year target cycle length. FCC-Pretreat The economic value of FCC-PT depends on its ability to enhance the yields and quality of FCC unit products. The main objectives in FCC-PT include minimising sulphur lev - els through HDS, reducing nitrogen and aromatic content by optimising HDN and HDA, and increasing the conver - sion of vacuum gasoil (VGO) to diesel-range products. Figure 7, analogous to Figure 4 for distillate hydrotreating, illustrates the main operating zones and the role of the DDS and HYD functionalities of the catalyst in a low- and medi- um-pressure FCC-PT unit (inlet PPH₂ < 90 bar/1,300 psig). Unlike in distillate hydrotreaters, in FCC-PT units Zone 3 (nitrogen-free zone) is never reached due to the signifi - cantly higher presence of refractory nitrogen and PNAs in VGO and heavy coker gasoil (HCGO), owing to their higher boiling points. Consequently, FCC-PT reactors operate either entirely in Zone 1, or in Zones 1 and 2. Zone 1 in FCC-PT is defined as the part of the reactor where predominantly olefins and easy sulphur are con - verted. In Zone 1, the main limiting factor for performance is the inhibition by refractory nitrogen and PNAs, particu - larly on the removal of hard sulphur. HDN and HDA reac - tions tend to be further constrained by the relatively low hydrogen pressure. Loading a catalyst with high DDS activity in Zone 1 is crucial for two reasons: DDS is the fastest reaction route to remove sulphur and helps limit coke formation on the active metal phase. Additionally, good pore accessibility is important to allow the deposition of coke and metals with- out significantly impacting reactants’ mass transfer. When the intermediate product nitrogen falls to a suffi - ciently low level, Zone 2 is reached. Refractory sulphur also starts being converted as HDS proceeds via both the DDS and HYD routes. Due to the reduced inhibition, HDN of refractory nitrogen and HDA are also favoured. While the exact nitrogen and corresponding sulphur levels marking the transition from Zone 1 to Zone 2 vary by operation, it is generally assumed that Zone 2 starts below a product sulphur level of approximately 1,500 ppmwt.

Guard Removes particulates & poisons Manages asphalt e nes, CCR , and H-PNAs Zone 1 (3 , 500-1 , 500 ppm S) Saturates olens & converts easy S (DDS) S tarts converting N & (H-)PNAs to Di-/Mono-As ( HYD ) Zone 2 (1 , 500-200 ppm S) Converts S via both HDS pathways (DDS + HYD) Converts N & PNAs to Di-/ Mono-As (HYD)

Log S, N

Guard

Zone 1

Zone 2

S N

A catalyst for Zone 2 still requires high DDS activity but also needs sufficiently high HYD activity. An open pore structure is highly beneficial also in Zone 2, especially when the main operating target is increased conversion of VGO feed to diesel, as it provides better stability against coke deposition, particularly at the high temperatures where maximum conversion is achieved. The features that make Pulsar technology excel in distillate hydrotreating also make it effective in low- and medium- pressure FCC-PT operations in Zones 1 and 2, both in HDS and conversion mode. The small size of the Pulsar metal slabs provides very high DDS activity, low nitrogen and PNAs inhibition, and low tendency to coking. Their high dispersion and narrow size distribution increase stability by reducing the likelihood of metal migration and sintering. The first catalyst developed for FCC-PT using Pulsar technology is KF 917, a high-performance NiCoMo grade for low- and medium-pressure operations, created in col- laboration with Nippon Ketjen’s R&D centre in Niihama, Japan. Launched in the last quarter of 2024, it already has a commercial application. Its active phase provides high DDS selectivity and nitrogen tolerance, leading to high HDS activity and stability, as well as improved HDN and HDA activity with moderate hydrogen consumption. KF 917 is highly effective in both Zones 1 and 2 of the reactor. Its performance advantage can be monetised by refiners by increasing the intake of more distressed feedstock and/or through lowering operating WABT and increasing cycle length. Additional benefits include opera - tional flexibility and robustness. KF 917 can treat a broad range of feedstocks, including high percentages of HCGO, with increased resistance to operational upsets. Its advan - tage over previous generation KF 907 is demonstrated through two comprehensive pilot plant tests, as summa - rised in Figure 8, highlighting advantages in terms of SOR activity, enhanced stability, and its capability to process more challenging feedstock. The first test consisted of a side-by-side comparison of the two catalysts at low pressure fed with VGO and operat - ing at a constant product sulphur level of 1,500 ppmwt. To Figure 7 Reactor zones and role of the catalyst’s DDS and HYD functionalities in a low- and medium-pressure FCC-PT hydrotreater

Catalysis 2025