Catalysis 2025 Issue

Co-processing of chemical recycling products in FCC units

To perform a techno-economic assessment it is important to determine the crackability and the yield structure effects of alternative feedstocks

Rafael Orejas Contreras Repsol María Bescansa Leirós Grace GmbH & Co. KG Spain Nelson Olong and Stefan Brandt Grace GmbH

A dvanced chemical recycling is projected to increase over the coming years and decades to improve the circularity of plastics, reduce environmental pollution, and decrease the dependency on fossil crude. The use of unconventional feedstocks, such as waste-derived streams in refinery processes, continues to be evaluated from an eco - nomic, regulatory, and environmental perspective. As Figure 1 shows, it is projected that the availability of plastic waste for chemical recycling will increase to about 7-20 million tons by 2030, with continued growth thereaf - ter. Ideally, mixed plastic waste is converted by advanced chemical recycling processes to monomers as feedstocks for new plastic production to maximise carbon circularity. However, suitable conversion processes are not yet com - mercially available at scale. Pyrolysis technologies are find - ing increased application for advanced chemical recycling, producing a liquid product, plastics-derived pyrolysis oil (PDPO), which requires secondary conversion in existing refining or petrochemical assets for valorisation. The fluid catalytic cracking (FCC) unit is one of the most flexible units in a crude oil refinery. The unique properties of the FCC unit allow significant adjustments to unit operation and, therefore, yield patterns within short periods of time. The daily catalyst addition allows for catalyst optimisation while the unit is operational. Severe catalyst deactivation can be proactively miti - gated by increased catalyst additions within the catalyst management strategy of the refinery. Longer term cata - lyst deactivation factors will require catalyst reformulation in collaboration with the FCC catalyst supplier. However, any significant feedstock change requires a thorough risk assessment regarding its consequences on unit operation, conversion, yield pattern, catalyst inventory and, if possible, downstream processing. Risk assessment considerations Determination of the physical and chemical attributes of respective feedstocks will provide a basic understanding of potential conversion and yield impacts and indicate con- taminants that might affect catalyst management as well as downstream equipment. Physical attributes include density, viscosity, refractive index, boiling point distribution,

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and moisture content, influencing handling, transport, and processing. Chemical attributes involve elemental composi - tion, molecular structure, and the presence of specific com - pounds, which determine reactivity, conversion efficiency, and compatibility with catalysts. For example, Figure 2 depicts results from different plastics-derived feed samples received by Grace. The data Any significant feedstock change requires a thorough risk assessment regarding its consequences on unit operation, conversion, yield pattern, catalyst inventory and, if possible, downstream processing proves the heterogeneity of the received samples in terms of contaminant and heteroatom contents and allows an initial assessment of impacts on FCC catalyst, operation, conversion, yield structure, and emissions. Some of the feedstocks with very high Calcium (Ca) or Conradson carbon content will have an impact on catalyst deactivation and unit operation. Calcium is a known poison to the FCC catalyst, which deposits on the external surface Figure 1 Outlook of plastic waste potential for chemical recycling by pyrolysis Based on OECD data 1

Catalysis 2025