Question
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What options are available for increasing the number of higher octane gasoline components?
Jun-2024
Answers
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Subramani Ramachandran, Ketjen, subramani.ramachandran@ketjen.com
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 operational 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/catalyst 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 differing yield objectives include:
• Maximising net octane barrels
• Maximising alkylation (alky) barrels.Maximising net octane barrels
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 directionally 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 barrels increase was achieved at lower slurry yields. Traditional approaches to light olefins selectivity optimisation have typically centred around RE-level optimisation, incorporating different shape-selective activity with varying molecular 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 hydrogen transfer increase (HTI) provides an additional degree of freedom to achieve targeted molecular selectivities.Maximising alky barrels
Alternatively, depending on individual refinery configurations 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 olefinicity 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 balance between activity increase and HTI compared to conventional 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 operating in maximum fuels mode, tailored approaches such as Action+ result in a significant increase in alkylate octane barrels 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 solutions will be refinery-specific, depending on economic drivers, and there is no one-size-fits-all. As the prior two case studies demonstrate, approaching the challenge holistically and partnering with a catalyst technology provider will provide the best outcomes in terms of achieving the desired yield and product quality shifts while maximising overall unit profitability. Various catalytic handles are available with advances in catalyst technology, and a partnership approach is the key to sustained success in a dynamic environment.
DENALI and ACTION are marks of Ketjen.
Jul-2024
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