Catalysis 2025 Issue

S edge

Mo edge

HYD

DDS

HYD

DDS

Figure 2 Model of the DDS (light green frames) and the HYD (blue frames) active sites in CoMo hydrotreating catalysts

inhibition, and overall better performance at low pressure and in the red operating region, is typical of catalysts with smaller metal slabs and stronger metal-support interaction (Type I). HYD selectivity, on the other hand, is enhanced by lower metal-support interaction (Type II). Notably, NiMo catalysts have higher HYD selectivity than CoMo catalysts, regardless of other characteristics. The relationship between the morphology of the active metal phase and the DDS and HYD activity/selectivity is visualised in Figure 2 for a CoMo catalyst. The DDS reac- tion pathway occurs at the positions available for the cobalt (Co) atoms at the slabs’ sulphur edges (light green frames). Conversely, all hydrogenation reactions, including the HYD pathway for HDS, take place on the molybdenum (Mo) atoms adjacent to the slabs’ edges (blue frames). Smaller metal slabs possess more DDS sites relative to HYD sites and are thus more DDS selective. At equal metal slabs size, a catalyst’s HYD character can be further increased by lower- ing the interaction between the metal slabs and the support. In general, smaller and better-dispersed metal slabs are highly beneficial for the hydrotreaters’ performance in all applications and operating regions. They lead to higher efficiency with more activity provided for the same amount of metal. They also provide higher stability thanks to their greater tolerance to nitrogen and PNAs and lower

tendency to coking, metal mobility, and sintering. The advantage of smaller and better-dispersed metal slabs is greater for applications that rely heavily on the DDS reaction pathway for HDS, such as low- and medium- pressure distillate hydrotreating and fluid catalytic cracking pretreatment (FCC-PT). Low- and medium-pressure distillate hydrotreating Pulsar is Ketjen’s latest catalyst platform alongside Quasar. Initially introduced for distillate hydrotreating, this technol- ogy has now been further developed for FCC-PT applica- tions in partnership with Nippon Ketjen. This collaboration led to the market introduction of KF 917 Pulsar at the end of 2024. Two grades are applied for distillate hydrotreating, KF 787 and KF 774. The two catalysts combined cover all types of distillate applications from low to medium-to-high pressure (typically, 10-60 bar/150-900 psig PPH₂). Despite their recent introduction, distillate hydrotreat- ing Pulsar grades have already become a standard in the industry, with more than 7,000 tons of catalyst applied and 60 commercial cycles. One of the key features of the Pulsar technology is its advanced active phase morphology. Pulsar metal slabs are significantly better dispersed and approxi - mately 40% smaller than in previous generation catalysts. Their size distribution is also very narrow. Figure 3

TEM analysis: comparison

90% 80% 100%

0% 30% 20% 10% 40% 50% 60% 70%

KF 757 KF 787 P ulsar

Estimated slab length (nm)

Figure 3 Statistical analysis of the metal slabs’ length in spent KF 787 Pulsar after operating with cracked feedstock at high temperature (3D-STEM study)

Catalysis 2025