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Question

  • What catalyst additive technologies are available to enhance propylene production in our FCC unit?

    Jan-2022

Answers


  • Mark Schmalfeld, BASF - Refining Catalysts, mark.schmalfeld@basf.com

    Amit Shah, Technical Service Manager, BASF, Amit.shah@basf.com, Lynne Tan, Technology Manager, BASF, Lynne.tan@basf.com, and Mark Schmalfeld, Global Marketing Manager, BASF, mark.schmalfeld@basf.com

    There are various routes for maximum propylene production and the best route is what is suitable for respective refineries’ target and scope. Many licensors provide technological solutions to revamp existing FCC units for more propylene production, but a significant investment and long lead time are expected. A suitable catalyst design is a quick and easy alternative for FCC units to maximise propylene under existing hardware configurations.

    Propylene maximisation approaches are similar across a wide range of feed types, however it can be more difficult in resid applications. To accomplish maximum propylene from a resid feed, a catalyst needs to have high metals tolerance to prevent activity and conversion loss due to contaminant metals, and good coke selectivity to better manage heat balance, which is often a key challenge. An ideal maximum propylene catalyst will leverage on these unique characteristics to deliver optimal bottoms conversion to produce light naphtha, the precursor for propylene, and accentuates the effects of an olefin additive (using a ZSM-5 type zeolite) to produce high propylene yield and selectivity.

    Conventional and easier to implement approaches are changes in operating conditions, feed quality, naphtha recycle, and use of ZSM-5 additives.

    Recent developments in olefin additive technology (using ZSM-5 zeolites) may be used for boosting propylene yield from current levels. Typical olefin additives contain significant percentages of ZSM-5 zeolite. Leading catalyst suppliers have now launched latest generation ZSM-5 additives that contains >50% crystals. Using such a high crystal ZSM-5 additive while maintaining the dosing rate the same as the incumbent additive can significantly boost propylene yield, provided sufficient olefin precursors are available in the light gasoline stream. The quantum of incremental propylene that can be achieved depends on specific application.

    Additionally, the base FCC catalyst design can have a significant influence on propylene yields. Tuning and optimisation of the rare earth on zeolite, catalyst surface areas, and zeolite to matrix surface areas can play a key role in producing propylene.

    Net propylene produced from the FCC unit can also be increased by reducing/minimising the losses in the dry gas/fuel gas. In one patented application, a refinery added a chiller to cool the naphtha used in the primary absorber to minimise the loss of propylene in the fuel gas. The value of propylene in a petro-refinery is high enough to payback additional investment in a short time.

    Other developments for boosting propylene yield would involve FCC technology licensors offering latest technologies that can be implemented in an existing FCC unit with hardware additions/modifications.

     

    Jan-2022