While blending is a common method used to increase the octane rating of gasoline, there are usually concerns about high costs, availability, and environmental concerns. Due to that, optimising your catalyst system in the gasoline hydrotreater provides the most control to produce high- quality octane gasoline. A Subramani Ramachandran, Technical Service Director, Asia, Ketjen, Patrick McSorley, FCC Technical Service Engineer, Ketjen, and Junghwa Yoon, FCC Technical Service Consultant, Ketjen Refiners have a multitude of options for increasing overall octane barrels output from the refinery, either by increasing FCC gasoline RON and/or by increasing the output of high- octane blend components such as reformate, alkylate, and isomerate. Typically, FCC operators have multiple opera- tional handles to further maximise overall octane barrels from their FCC asset. While short-term operational moves like maximising riser outlet temperature (ROT), maximising CTO (impact depends on conversion level), and deployment of ZSM-5 additives can provide a short-term boost, they tend to move a carefully optimised FCC operation/cata- lyst system to an overall sub-optimal operating point. Our approach in such cases is to work closely with the refiner to design and implement a catalyst reformulation that can provide the necessary octane barrel shifts that the refiner is seeking while maximising overall profitability. Two such case studies of maximising overall octane barrels with dif- An existing customer using the Denali catalyst was looking to further maximise C₄= yields without significant penalty in gasoline volume from their FCC unit along with improved bottoms yields. The Denali family of catalysts incorporates our latest ZT-600 zeolite technology. It provides enhanced coke selectivity and superior activity retention, which directionally lowers hydrogen transfer at similar activity. A reformulated Denali catalyst was designed with direction- ally lower RE content while compensating for the lower resultant activity by enhancing the active-matrix content in the catalyst. Figures 1 and 2 show the key benefits of the reformulated Denali compared to the base. Not only was the reformulation able to provide the desired C₄= increase at minimal gasoline volume loss, but the overall octane bar- rels increase was achieved at lower slurry yields. Traditional approaches to light olefins selectivity optimisation have typically centred around RE-level optimisation, incorporat- ing different shape-selective activity with varying molecu- lar selectivities. In addition to these levers, optimisation of active-matrix content and type is an additional handle from a catalyst formulation standpoint to tailor the system hydrogen transfer index. While matrix components provide bottoms cracking along with activity enhancement, their ability to provide these benefits without enhancing hydro - gen transfer increase (HTI) provides an additional degree of freedom to achieve targeted molecular selectivities. fering yield objectives include: • Maximising net octane barrels • Maximising alkylation (alky) barrels. Maximising net octane barrels
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Figure 1 Butylene yield enhancement vs gasoline compared to incumbent catalyst
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Maximising alky barrels Alternatively, depending on individual refinery configura - tions and economics, maximising alky barrels might be an overriding objective in certain regions. In this case study, the refiner was employing an Action catalyst, which is proven in the industry for its capability to maximise C₄= and C₄ olefi - nicity while providing excellent bottoms cracking. To meet their need, they were supplementing it with conventional ZSM-5 additive additions to increase the desired C₄ olefins. Action+ catalyst was proposed to Ketjen’s refinery partner, which employs a novel stabilisation technology (ZT-500). This new stabilisation technology provides a superior bal- ance between activity increase and HTI compared to con- ventional rare earth modification. This approach allows refiners to maximise C₄= yields at similar C₃= yields at comparable activity (see Figure 3 ), effectively maximising alky barrels more than conventional catalyst (plus additive) approaches would allow. For conventional FCC units oper- ating in maximum fuels mode, tailored approaches such as Action+ result in a significant increase in alkylate octane bar - rels due to a higher octane potential of C₄= relative to C₃= in an alkylation unit while achieving the above at a net lower wet gas volume, compared to conventional approaches. In summary, the FCC unit remains an important vehicle for maximising high-octane gasoline components. Optimal solu- tions will be refinery-specific, depending on economic driv - ers, and there is no one-size-fits-all. As the prior two case studies demonstrate, approaching the challenge holistically Figure 2 Slurry yields vs net octane barrels compared to incumbent catalyst
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PTQ Q3 2024
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