• How is the dual focus on increasing butylene and propylene production being met?



  • Alvin Chen, BASF, alvin.u.chen@basf.com

    While butylene pricing is often quite stable (typically either very high or very low), propylene pricing has seen significant volatility over the past few years. One approach that many refiners have adopted, to address the dual focus on butylene and propylene production, is to formulate a base FCC catalyst with moderate overall LPG= selectivity and an emphasis on strong C₄= selectivity. Such a catalyst coupled with judicious usage of ZSM-5 offers excellent C₄= selectivity during times when C₃= value is low. However, it still allows the refiner to capture short-term C₃= opportunities while maintaining a strong C4= yield.

    One strategy for the optimum base catalyst is to optimise the acid site distribution on the catalyst by increasing total surface area while reducing acid site density, allowing similar catalytic activity with reduced hydrogen transfer. Since it is known that butylenes are more sensitive than propylene to hydrogen transfer effects, a catalyst with this approach will target both products depending on process conditions and externally added ZSM-5. BASF applies this catalyst design approach in the Multiple Frameworks Topologies (MFT) technology, where secondary zeolite frameworks are also used to further improve butylenes to propylene flexibility. Catalysts like Fourte and Fourtune for VGO applications and Fortitude for resid applications are examples of the MFT catalyst technology for FCC units.

    It should not be forgotten that operating conditions, such as catalyst-to-oil ratio and reactor outlet temperature, also have an impact on butylenes to propylene distribution, with butylenes favoured at mild severity conditions, while propylene is favoured at high severity conditions.