PTQ Q2 2023 Issue

Co-processing alternative feedstocks through the FCC

Decarbonise your FCC by co-processing alternative feedstocks, and enhance the incorporation of biogenic carbon in products

Oliver Dobson, Mike Watson, Wayne Armstrong, Marie Goret-Rana, Matthew Ryder and Paul Diddams Johnson Matthey

T he fluid catalytic cracking (FCC) unit continues to be a significant source of refinery margin, enabling refin - ers to upgrade the bottom of the barrel to valuable transportation fuels and petrochemical feedstocks while also maximising liquid volume yield. The inherent process flexibility of the FCC enables refiners to react swiftly to changing market economics, ranging from maximising dis - tillate production to maximising petrochemical precursors. However, despite these benefits, the FCC is a major con - tributor to CO2 emissions from the refinery, leading opera - tors to consider decarbonisation strategies to help deal with these unavoidable CO2 emissions. One approach is to reduce grey carbon intake through co-processing of alternative feedstocks. This allows the FCC energy balance to be respected while also reducing the contribution of fossil fuels to overall CO2 emissions from coke combusted. FCC co-processing is in its infancy, but several refiners are exploring new feedstocks. Some of these feedstocks, such as biomass pyrolysis oils, can also help refiners meet RED II advanced biofuel mandates, which currently require transportation fuels to contain at least 3.5% advanced biofuel-derived energy by 2030. Under Annex IX, biomass pyrolysis oil can be double counted, offering a potentially low-cost solution to meet the RED II targets. Methanol option Capture and re-use of FCC flue gas, either for sequestration

or use as syngas feedstock for production of methanol, pro - vides an additional approach to decarbonise. Methanol has significant potential to become a low carbon energy vec - tor. Johnson Matthey has developed HyCOgen, a reverse water gas shift technology that achieves the appropriate CO2 conversion required for methanol synthesis. Johnson Matthey has a long history in methanol synthesis and flow - sheet design. Capture and re-use of FCC flue gas, either for sequestration or use as syngas feedstock for production of methanol, provides an additional approach to decarbonise Various alternative feedstock types are being looked at for co-processing in the FCC. These feed types each have their own unique combination of impacts on FCC yields, selectivities, and unit performance. Potentially important feedstocks and their impact are summarised in Table 1 . Co-processing biomass pyrolysis oils can be a significant challenge in the FCC (see Table 1). Biomass pyrolysis oils are highly unstable due to their significantly high levels of oxy - genated compounds. These oxygenates risk polymerisation

Examples of feedstocks potentially important for FCC co-processing

Feed

Challenges

RED II targets Limited to 7%

Vegetable oils

• Oxygenates can be an issue in some cases • Political competition with food sector

Biomass pyrolysis oils

• Increased coke selectivity

Advanced biofuels >3.5%

• Increased dry gas selectivity • Immiscible with conventional oil feeds

(Biomass pyrolysis oil can be double counted, effectively lowering the limit)

• Thermally unstable • Oxygenates, chlorides, calcium, potassium, etc

Waste plastic pyrolysis oils

• Chlorides and other contaminants

No impact

Table 1

PTQ Q2 2023