Question
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What are the optimal pathways towards increasing naphtha and LPG production (for petrochemical feedstocks)?
Feb-2025
Answers
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Carl Keeley, Johnson Matthey , carl.keeley@matthey.com
Naphtha is a fraction derived from crude oil and can also be obtained from natural gas condensates, petroleum distillates, and other less common routes. It is primarily used to produce gasoline and as a feedstock for petrochemical products. LPG is commonly used for heating and cooking and includes products like propane, butane, and propane-butane blends. In addition to propane and butane, crude oil refining produces LPG olefins; these olefins are used to enhance gasoline quality and serve as feedstocks for petrochemical production.
While gasoline demand is projected to decline as the US, Europe, and China adopt fuel alternatives and move towards a net zero economy, demand for naphtha and LPG for petrochemical production is expected to continue to grow (source: bp Energy Outlook 2024).
Crude oil is produced in many locations, with physical properties unique to the location from which it is extracted. Certain types of crude oil provide a higher yield of straight-run naphtha and LPG after distillation. By carefully selecting the crude oil blend to process, oil refineries can maximise naphtha and LPG production. In addition to crude oil distillation, oil refineries can use conversion process technologies such as FCC to increase naphtha and LPG production.
By optimising feedstock selection, equipment, process conditions, catalyst formulations, and additives, the FCC units can maximise naphtha and LPG yields depending on refinery economics. In general, FCC feeds are predominantly paraffinic. Paraffinic feeds are easier to crack and normally provide the highest naphtha and LPG yields. Enhancements in feed injection, feed-catalyst mixing, and product and catalyst separation can boost naphtha yields. In addition, routing naphtha to a second reaction zone or dedicated riser can significantly increase LPG yields.
Each FCC unit has its own operating window based on its available equipment and other constraints. Generally, high operating severity drives both thermal and catalytic cracking reactions. However, thermal cracking produces low-value byproducts like dry gas. Optimising FCC catalyst selection and incorporating additives enables the operator to reduce operating severity and significantly increase naphtha and LPG production.
Commercial FCC catalysts are engineered materials to optimise yields within unit constraints. The matrix materials perform the precracking of large molecules. The smaller, intermediate products produced can then enter the ultra-stable Y (USY) zeolite, where they are further converted into naphtha, LPG, dry gas, and coke. In addition to the FCC catalyst, specialist additives can be added to enhance LPG yield and increase propylene and butylenes production. Other additives are available that enable operators to boost LPG olefins when FCC gasoline olefinicity is low.
Utilising reliable and accurate catalyst and additive addition systems is essential for optimising the addition of FCC catalyst and additives. Frequent, small additions are preferable to infrequent, large ones, as larger additions can upset FCC circulation and catalyst retention, leading to sub- optimal performance. Likewise, regular, small withdrawals of spent catalyst are recommended. Expertise in the catalyst and additive addition system design is crucial, as poorly designed systems can result in compromised safety and reliability, as well as reduced production of FCC naphtha and LPG.
As refining markets continue to evolve, the operational flexibility of FCC units adapts accordingly, enabling refiners to remain competitive and profitable. The primary product streams consist of naphtha for gasoline production, along with naphtha and propylene for petrochemical production. Additional downstream naphtha and LPG olefins processing requires hydrogen and purification steps, requiring catalyst and absorbents.
Jan-2025
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