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What are the optimal pathways towards increasing naphtha and LPG production (for petrochemical feedstocks)?

Feb-2025

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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
Mark Schmalfeld, BASF Refinery Catalysts, mark.schmalfeld@basf.com

Production of naphtha and liquefied petroleum gas (LPG) as petrochemical feedstocks is critical for meeting the demands of various industries. To increase the yield of these valuable products, a multifaceted approach is essential, focusing on optimising processes, catalysts, and operational parameters. Several optimal pathways can enhance the production of naphtha and LPG via fluid catalytic cracking (FCC), hydrocracking, and catalytic reforming.

FCC is a widely utilised process for converting heavy hydrocarbons into lighter products. The selection of advanced zeolite-based catalysts is pivotal because they can significantly enhance selectivity towards naphtha and LPG. Innovations in catalyst composition, including the incorporation of specific metals or alterations to the pore structure, can lead to improved performance and greater product yields. Additionally, optimising reaction conditions such as temperature and pressure is crucial for maximising the production of lighter hydrocarbons.

Higher temperatures generally favour LPG yield, while specific pressure adjustments can enhance naphtha production. High-severity FCC operation can further maximise light products (LPG, C2=) if the refinery has appropriate product recovery facilities. However, the high coke yield and high cat-to-oil required to achieve high-severity operation may require significant feed rate reduction. Hardware design features, such as a dedicated riser to catalytically crack recycled naphtha to more light olefins or special riser terminations to increase residence time, are an additional handle to maximise light olefins production.
Hydrocracking is another critical process that can be optimised to improve yields. The development of bifunctional catalysts that combine hydrogenation and cracking functionalities can enhance the conversion of heavier feedstocks into lighter products, such as naphtha and LPG. Furthermore, maintaining an adequate supply of hydrogen is essential for facilitating hydrocracking, which can further increase LPG yields from heavier fractions.

Catalytic reforming processes also play a vital role in converting naphtha into high-octane gasoline components and generating aromatics. By adjusting catalyst properties and operating conditions, the catalytic reforming process can be optimised to maximise LPG yields as a byproduct while simultaneously improving the quality of gasoline components. Integrating reforming with other processes can recycle hydrogen and maximise the overall efficiency of naphtha conversion, creating a more streamlined production chain.

Utilising diverse feedstocks is also essential for enhancing naphtha and LPG yields. Employing a variety of feedstocks, including heavier crude fractions and biogenic sources, can lead to increased overall production. Tailoring processing conditions based on the characteristics of the feedstock can further optimise yields. Additionally, implementing pretreatment processes to remove impurities can enhance the quality of the feedstock before it enters conversion units, thus improving the efficiency of subsequent processing steps.

Effective heat and energy management strategies are a key consideration for lowering operational costs to make the economics of naphtha and LPG production more attractive. Implementing heat integration and recovery systems minimises energy consumption during processing. Efficient energy use not only lowers operational costs but also enhances the economics of naphtha and LPG production. Optimising reactor designs for better thermal management can further improve conversion rates and increase product yields.

Leveraging data analytics can optimise production processes significantly. Utilising real-time data analytics and machine learning algorithms allows for continuous monitoring and optimisation of production processes. Predictive maintenance and operational adjustments based on data insights can enhance overall efficiency. Additionally, developing simulation models can help analyse various scenarios and optimise process parameters for maximum naphtha and LPG production.

Incorporating sustainability into production processes is increasingly important. Exploring carbon capture and utilisation technologies can minimise the environmental impact of increased production, thereby improving the sustainability of operations while maintaining high output levels. Investigating bio-based feedstocks and waste-to-energy technologies can also contribute to naphtha and LPG production, aligning with broader sustainability goals.

In conclusion, to optimise the production of naphtha and LPG for petrochemical feedstocks, a comprehensive approach that encompasses advanced catalyst development, process optimisation, feedstock flexibility, and innovative technologies is essential. By leveraging these pathways, the petrochemical industry can enhance the yield of these valuable products while improving both economic and environmental sustainability. The future of naphtha and LPG production lies in the integration of these strategies to meet the growing demand for petrochemical feedstocks in an environmentally responsible manner.

Jan-2025