Cracking of hydrotreated waste fats and oils over zeolites for renewable propene production. Part II: Cracking of Hydrotreated & isomerized paraffinic products derived from the Hydroprocessed Esters and Fatty Acids (HEFA) process

[EN] In this work, we explore the production of light olefins by cracking the hydrotreated and isomerized paraffinic products obtained from the Hydroprocessed Esters and Fatty Acids (HEFA) Process. Using isomerized paraffins instead of normal paraffins derived from Hydrotreated Vegetable Oils (HVO) as cracking feedstock may enhance both cracking activity and light olefin selectivity. This possibility is therefore systematically investigated. Zeolitic catalysts with customized micropore size, topology, hierarchical porosity, and framework composition have been employed to optimize the thermodynamic and kinetic aspects of both primary and secondary reactions. A combined optimization of catalysts and process conditions enabled light olefin yields of 60¿65 wt%, with 30¿35 wt% propylene, in a once-through fixed-bed reactor employing ZSM-12, hierarchical ZSM-5, and hierarchical IM-5 as cracking catalysts. Further process refinement, including recycling of the C5 + fraction, significantly enhanced performance, yielding up to 89¿90 wt% light olefins and 46¿48 wt% propylene. Stability tests identified hierarchical ZSM-5 as the most effective zeolite, maintaining high activity and selectivity during extended operations. Finally, a comparison between the results from HVO cracking and those obtained in the present study confirms that ZSM-5 zeolite remains the most active, selective, and stable catalyst for both types of feedstocks. This highlights the versatility of the proposed catalytic strategy for processing a broad range of biogenic feedstocks.