R2P (Resid to Propylene)
When the process objective is maximum propylene production, specific technology features must be added to the RFCC unit (R2R technology). The challenge is particularly great when the feedstock contains residue.
Axens’ strategy to maximize propylene production includes the following elements:
- Maximize the yield of light olefins and maximum liquid using FCC cracking catalyst at high severity in combination with proprietary FCC hardware to promote low delta coke (feed injectors, stripper packing) and minimize fuel gas (RS² separator, feed injectors).
- Minimize hydrogen transfer reactions by reducing the hydrocarbon partial pressure, optimizing the FCC catalyst, adjusting the reaction time.
- Utilize ZSM-5 catalyst additive at optimum concentrations in equilibrium catalyst to convert the light olefin precursors that exist in the cracked gasoline product.
- Employ two-stage catalyst regeneration strategy when processing residue feed to maintain high catalyst activity and minimize catalyst deactivation to reduce the cost of catalyst consumption.
- Convert Butene and Pentene into oligomers for recycle cracking in the FCC into propylene using FlexEneTM.
- Integrate a dedicated riser zone for light naphtha cracking if maximum propylene is targeted - PetroRiserTM.
Selection of the optimal catalytic system is vital as the base catalyst and the much more costly ZSM-5 additive must work together to maximize the production of propylene. The added cost of the ZSM-5 is usually offset by the higher margin for petrochemical products. However, the window of opportunity to use ZSM-5 is wider with the Axens two-stage regeneration R2R design because of the lower cost of catalyst consumption compared to other technologies and the ability to process lower valued residue feeds.
Depending on the quality of the feed and the propylene and other product targets, Axens can develop customized solutions for:
- Maximum LPG and Gasoline or "High Propylene"
- Maximum Propylene