PTQ Q4 2025 Issue

to a limited extent, product selectivity. This includes adjust- ing the riser temperature, feed preheat, regenerator tem- perature (if the unit has a catalyst cooler), riser or stripping steam rates, and air rates (if operating a partial burn unit). Steam and air rates are almost always adjusted in response to changing feed or operating conditions to maintain optimal performance. However, the reactor, regenerator, and feed temperatures are often adjusted in response to market shifts. A common example is lowering the riser temperature in the winter in response to the shift from higher gasoline demand to higher diesel demand. Close communication between economics and planning (e&p) and operations will enable quick responses to changing market conditions. That said, these handles cannot fine-tune product selectivity, which will be further discussed. FCC additives allow for a much greater range of product flexibility and can be implemented quickly, sometimes in just days. Perhaps the best-known additive is the ZSM-5 zeo- lite that cracks gasoline into LPG olefins and is often used to keep alky units full and/or to improve gasoline octane. There are now several variations of ZSM-5 products, allow- ing refiners to further dial in the yield and quality of their LPG and gasoline streams. Other additives include bottoms- upgrading additives and metals traps. These can be a good option when dealing with opportunity feeds with higher Conradson Carbon Residue (CCR), higher metals, or lower crackability. Engineers should talk with their additive supplier to learn about the latest products and to explore options that would be a good fit for their operation. Refiners can also consider a catalyst reformulation to meet future needs. FCC catalyst suppliers can adjust many features of their catalysts, including the zeolite type and structure, rare earth exchange, Si/Al ratio, matrix selection and design, and zeolite-to-matrix ratio, which allows them to design for a wide variety of unit configurations, FCC feedstocks, and product demand. Additionally, each supplier has different manufacturing methods and feedstocks, so even if one sup- plier is struggling to meet a refiner’s need, another might have a viable solution. It should be emphasised that proper catalyst selection and transition is a lengthy process, taking several months to a year to go from initial consideration of catalyst alternatives to fully turning over the catalyst inventory. Success with any option is a team effort. Engineering, E&P, operations, logistics, and purchasing should all work together to predict refinery needs, understand constraints, and implement solutions. Best success is obtained when refinery leadership facilitates communication and empow - ers their teams. With aligned teams and informed choices, FCC-focused refiners can adapt effectively, even mid-cycle, to evolving market conditions. Q What process and operating conditions are required to make the newest hydroprocessing catalyst formulations perform optimally? A Woody Shiflett, Ph.D., Blue Ridge Consulting LLC, blu- eridgeconsulting2020@outlook.com After some 40-plus years of dealing with hydrotreating and hydrocracking catalysts and their technologies, it has

become evident that catalytic science has yet to bypass the limits of thermodynamics and the predominant kinetics for hydroprocessing, and carbon deposition that deactivates hydroprocessing catalysts. Paramount with respect to pro- cesses and operations, the key requirements remain ‘keep the hydrogen partial pressure high’ and ‘operate at as low a temperature as possible’. One cannot unmake polynuclear aromatic coke deactiva- tion precursors that have arisen from a thermodynamic limit. Many of the guidelines seem to still hold from a 2002 paper by Shiflett: “Excessive catalyst deactivation often results from inadequate hydrogen partial pressure to hydrogenate coke precursor compounds either in the oil or absorbed on the catalyst surface. It is therefore highly recommended that recy- cle hydrogen gas rates be three to four times the estimated hydrogen consumption. Gas purity must be taken into account in setting the recycle gas rates when hydrogen purity is low in the system. A second contributor to excessive catalyst deac- tivation is exposing the catalyst to temperatures in excess of what is required to achieve the operating objective. When available, make use of quench even early in a cycle to minimise outlet catalyst bed temperatures. Also, when operating at mild conditions or processing an ‘easier’ feed, avoid over-treating by adjusting the processing temperatures lower.” In addition, the unit needs to have state-of-the-art reactor gas-liquid distribution internals above each catalyst bed to minimise radial temperature spread, maximise hydrogen util- isation, and effectively employ most of the catalyst loaded. Reactor beds should not exceed the 5-7m maximum depth range to mitigate the normal tendency in trickle-bed units to be maldistributed with bed depth. Nonetheless, great strides have been made in catalyst activities to maximise cycle periods at lower temperatures while still meeting performance requirements. Indeed, the bulk metal sulphide Ni-W-Mo formulations of the last couple of decades are high activity examples, represented first by Nebula, then later by Celestia products co-developed by ExxonMobil and Ketjen, ART’s ICR-1000 series developed by Chevron, and Honeywell UOP’s Ultimet. These ultra-high activity catalysts have high hydrogena- tion activity that optimally requires higher hydrogen partial pressure to perform best and adequate hydrogen for satura- tion reactions. In addition, optimal performance within lim- ited hydrogen constraints can be tailored into new catalyst formulations by tight control of catalyst pore size distribution morphology and control the size of the active metal sulphide slab structures on the high surface area support, such as the Ketjen Pulsar series of catalysts. Expectations are that machine learning and ultimately AI will facilitate optimal integration of process unit design with catalyst design and screening. Considering vast databases of hydroprocessing catalyst test data, AI algorithms could specify potential catalyst activity, selectivity, and even sta- bility. Coupled with high-throughput testing already in wide usage, machine learning and AI offer great potential in opti- mising testing itself to accelerate identification of catalyst formulations and novel materials.

Ultimet is a mark of Honeywell UOP.

PTQ Q4 2025