Renewable Diesel and HVO Naphtha: Steam Cracking Optimization

The refining and petrochemical industry is undergoing a period of transformation driven by the need to reduce emissions, improve energy efficiency, and adapt to an evolving energy system in transition. In this context, the downstream sector has begun redefining the traditional role of refineries, evolving toward industrial complexes capable of integrating fuel production and petrochemical feedstock generation within the same infrastructure. This convergence between refining and petrochemicals emerges as one of the strategic pillars for maintaining the competitiveness of existing assets while moving toward operational models with lower carbon intensity aligned with the development of low-carbon fuels and next-generation renewable fuels.

Within this transition, renewable diesel produced through the hydroprocessing of renewable feedstocks, a key pathway in the production of advanced renewable fuels for industrial decarbonization, has emerged as one of the most relevant technological platforms for the decarbonization of heavy transportation. Unlike other biofuels, HVO renewable diesel (Hydrotreated Vegetable Oil) exhibits properties compatible with conventional diesel specifications, allowing its direct use in existing infrastructure under standards such as ASTM D975, with ASTM D975 remaining one of the key regulatory benchmarks.

Beyond its role as a transportation fuel, HVO production processes generate a series of renewable coproducts, including light paraffinic hydrocarbon fractions known as HVO naphtha. These streams are beginning to attract interest in the petrochemical industry as potential feedstocks for steam cracking units aimed at producing light olefins.

This approach, which will be the subject of technical analysis in several forums at the AFPM Annual Meeting 2026, proposes a new pathway for industrial integration in which renewable diesel coproducts can be incorporated into the petrochemical value chain, expanding the opportunities for value creation within modern refineries.

Renewable Diesel in the Downstream Context

The evolution of downstream refining has incorporated renewable diesel as a technically viable solution to reduce carbon intensity without substantially modifying existing infrastructure. Produced through hydroprocessing processes, primarily hydrodeoxygenation (HDO), this fuel has a molecular structure composed of saturated paraffins, chemically like fossil diesel. This structural similarity enables its direct integration into conventional logistics and distribution systems.

Is renewable diesel better than conventional diesel?

From a regulatory perspective, renewable diesel can meet specifications such as ASTM D975, which makes it a true drop-in fuel. This means it can be blended with or completely replace petroleum-derived diesel without requiring modifications to engines, storage tanks, or transportation networks. In addition, because it originates from renewable feedstocks, its life-cycle carbon intensity can be significantly reduced, depending on the feedstock (raw material) used and the hydrogen source employed during processing. However, in terms of energy performance and operational behavior, both fuels can perform very similarly, as they share comparable physicochemical properties.

Difference between renewable diesel and biodiesel

It is essential to distinguish between FAME (Fatty Acid Methyl Esters), commonly known as biodiesel, and HVO (Hydrotreated Vegetable Oil). FAME is produced through transesterification and contains oxygen within its molecular structure, which affects its oxidative stability and limits its blending ratio. In contrast, HVO is a fully saturated hydrocarbon, free of oxygen, with greater thermal stability and improved operational compatibility in cold climates and long-term storage systems

Hydroprocessing and Generation of Renewable Fractions

The production of renewable diesel is based on hydroprocessing technologies adapted to biogenic feedstocks. Unlike conventional petroleum processing, these streams contain oxygen within their molecular structure and therefore require catalytic stages designed to remove heteroatoms and convert triglycerides or fatty acids into paraffinic hydrocarbons compatible with fossil fuels. During this process, not only renewable diesel is produced, but also several light and middle fractions that can be further valorized within the refinery.

To better understand how hydroprocessing technologies convert renewable feedstocks into renewable diesel and valuable coproducts, the following video provides a clear overview of the process and its industrial relevance. Video source: Topsoe in youtube. This content is used for informational and educational purposes, and all rights belong to its respective owner.

Hydrotreating and Hydrodeoxygenation (HDO)

In the first stage of the process, renewable feedstocks undergo hydrotreating, one of the most critical steps in modern hydroprocessing, where impurities are removed and the molecules are stabilized under hydrogen-rich conditions, elevated temperature, and metallic catalysts. Subsequently, hydrodeoxygenation (HDO) takes place, a key reaction that removes the oxygen present in triglycerides through the formation of water, carbon dioxide, or carbon monoxide. At the same time, hydrogen participates in the saturation of double bonds, transforming unsaturated compounds into linear paraffins. This set of reactions requires a significant consumption of hydrogen, making it one of the most relevant operational factors affecting the economics of the process.

Hydrocracking and Isomerization

Once long paraffinic chains are obtained, additional hydrocracking stages may be applied, with hydrocracking playing a key role in controlling product distribution to adjust the fractionation and produce streams with specific boiling ranges. In parallel, isomerization modifies the molecular structure, and this isomerization step is essential to improve cold flow properties, generating iso-paraffins that improve critical fuel properties such as low-temperature performance and flow characteristics.

Renewable Feedstocks

HVO units can process a variety of renewable feedstocks, including vegetable oils, used cooking oils, and animal fats. Depending on the type of feedstock and the operational severity, hydroprocessing generates multiple fractions, including renewable diesel, HVO naphtha, light gases, and renewable propane, expanding opportunities for integration with other refinery and petrochemical processes

Renewable Diesel Process Diagram and Generation of HVO Naphtha

The production of renewable diesel (HVO) is based on a sequence of operations typical of hydroprocessing, adapted to transform biogenic feedstocks into paraffinic hydrocarbons compatible with existing fossil fuel infrastructure. The process begins with the feeding of renewable raw materials, such as vegetable oils, used cooking oils, and animal fats. These streams contain triglycerides and fatty acids with oxygen in their molecular structure, which requires catalytic transformation through hydrogen.

In the first stage, the feedstock or raw material undergoes hydrotreating and hydrodeoxygenation (HDO), where oxygen is mainly removed in the form of water, carbon monoxide, or carbon dioxide. Under conditions of high hydrogen pressure and temperature, unsaturated bonds are saturated and the molecules are converted into long-chain paraffins, chemically like the hydrocarbons present in conventional diesel. This set of reactions takes place within a hydroprocessing reactor, where specific catalysts allow control of conversion and process stability.

Subsequently, the hydrotreated stream is sent to a fractionation column, a key stage for separating the products by boiling range. From this separation, several commercial streams are obtained: renewable diesel (HVO) as the main product, HVO naphtha in the C5–C10 range, renewable propane (LPG), and small quantities of light gases.

From a mass balance perspective, these co-products represent a relevant fraction of the process and open opportunities for value creation within the industrial complex. HVO naphtha has begun attracting interest as a potential feedstock for petrochemical units, especially in steam crackers, where it can be converted into light olefins. In this way, the process diagram not only describes the production of renewable fuel but also highlights how renewable diesel coproducts can be integrated into the petrochemical value chain.

What Is HVO Naphtha? Technical Definition and Conceptual Framework

HVO naphtha (Hydrotreated Vegetable Oil naphtha) is a light fraction generated as a coproduct in renewable diesel production units through hydroprocessing processes, particularly during the hydrodeoxygenation (HDO) stage and subsequent fractionation. From a process engineering perspective, this stream corresponds to a hydrocarbon cut in the approximate C5–C10 range, separated in the fractionation column along with other streams derived from the hydroprocessing of renewable feedstocks.

Definition from a Process Engineering Perspective

Unlike petroleum-derived naphtha, HVO naphtha has a composition dominated by linear paraffins and iso-paraffins, resulting from the catalytic saturation of triglycerides and fatty acids present in oils and fats of biogenic origin. This processing pathway explains its low sulfur and aromatic content, as well as a relatively high hydrogen-to-carbon (H/C) ratio. These characteristics give HVO naphtha chemical properties that differ from those of conventional fossil naphtha streams, particularly in terms of thermal stability and behavior in petrochemical conversion processes.

Is There a Formal Regulatory Definition?

Currently, there is no specific technical standard that formally defines HVO naphtha. Existing regulations focus primarily on the main fuel produced in the process. For example, the ASTM D975 standard establishes diesel specifications for use in internal combustion engines, while the European standard EN 15940 regulates paraffinic fuels derived from hydrotreatment processes, including HVO. As a result, the identification of HVO naphtha relies more on criteria such as chemical composition, process origin, and petrochemical application potential rather than on an independent regulatory definition.

Differences with conventional fossil naphtha

Parameter	Fossil Naphtha	HVO Naphtha
Aromatics	Moderate	Very low
Sulfur	Low	Ultra-low
Paraffins	Mixed	High
H/C Ratio	Lower	Higher

These differences have direct implications for its behavior in petrochemical processes such as steam cracking, where the high paraffin content may favor the production of light olefins, while also contributing to lower emissions associated with sulfur and aromatic compounds during processing.

HVO Naphtha in Steam Cracking: Operational Parameters and Limits

HVO naphtha has begun to attract attention in the petrochemical industry as a potential petrochemical feedstock for steam cracking units, enabling its use as a strategic petrochemical feedstock, mainly due to its highly paraffinic composition. In steam cracking furnaces, where hydrocarbon molecules are subjected to extremely high temperatures to produce light olefins, the molecular structure of the feedstock has a direct impact on reaction kinetics, process selectivity, and the operational stability of the system.

Chemical Composition and Thermal Behavior

From a molecular perspective, HVO naphtha is composed primarily of linear paraffins and iso-paraffins, resulting from the complete saturation of compounds present in renewable feedstocks during the hydrotreating process. This high proportion of saturated hydrocarbons creates a chemical profile different from that of conventional fossil naphtha, which typically contains significant amounts of naphthenes and aromatics.

In terms of thermal behavior, paraffinic hydrocarbons tend to exhibit cracking kinetics favorable for the formation of light olefins, particularly ethylene and propylene, where ethylene yield optimization becomes a key performance indicator. At the same time, the lower presence of aromatics reduces certain secondary reaction pathways that can lead to the formation of heavy compounds or solid deposits. This characteristic can contribute to greater thermal stability of the process, although the actual behavior will depend on operating conditions and the feedstock blending strategy used in the furnace.

Critical Parameters in Steam Cracking

The performance of HVO naphtha in steam cracking units is determined by several key operational parameters. Among the most important is the furnace temperature, which typically ranges between 780 and 900 °C, where the thermal cleavage of carbon–carbon bonds occurs. Another determining factor is the residence time, generally maintained between 0.1 and 0.5 seconds, allowing the maximization of olefin formation before undesired secondary reactions take place.

Steam dilution also plays an essential role, as it helps reduce the partial pressure of hydrocarbons and limits coke formation on the metallic surfaces of the reactor. In turn, cracking severity, defined by the combination of temperature and residence time, must be carefully adjusted to optimize product yield while minimizing excessive thermal degradation.

Impact on Ethylene and Propylene Yield

Due to its paraffinic nature, HVO naphtha can promote reaction pathways that lead to higher yields of light olefins, particularly ethylene, compared with feeds containing larger proportions of aromatics. Likewise, the lower presence of aromatic compounds in the feed stream can help reduce certain heavy by-products, improving overall process efficiency. However, yield optimization ultimately depends on factors such as furnace severity, the exact composition of the feed, and the blending strategy with fossil streams within the petrochemical complex.

Co-products and Cuts: HVO Naphtha and Propane By-product

The renewable diesel production process through hydrodeoxygenation (HDO) not only generates the main fuel product but also produces a series of hydrocarbon coproducts that are part of the unit’s mass balance. During the catalytic conversion of triglycerides and fatty acids, molecular chains are transformed into saturated paraffins, and depending on operating conditions and the nature of the feedstock or raw material, the process produces light fractions that are subsequently separated in the fractionation stage.

Among these coproducts, HVO naphtha stands out, typically located within the C5–C10 boiling range, as well as renewable propane, generated as a result of the cleavage of the glycerol groups present in triglycerides. This propane can be recovered as renewable LPG, becoming a commercially valuable by-product within the energy value chain.

From a refining engineering perspective, these fractions provide opportunities for integration with other processes within the industrial complex. HVO naphtha, for example, can be used as a feedstock for petrochemical units, particularly in steam cracking processes, while renewable propane can be incorporated into LPG streams or used as a feedstock or raw material in conversion units.

In this way, the modern refinery seeks to maximize the value of each fraction generated, integrating fuels and petrochemical products within the same processing platform. This strategy allows optimization of process economics and strengthens the convergence between the refining and petrochemical sectors, which are becoming increasingly interdependent in the current energy landscape.

Industrial Case: ENI and the Integration of Renewable Diesel with Petrochemicals

One of the most representative examples of the evolution of refining toward integrated biorefining and petrochemical models is the one developed by ENI, the Italian energy company that has led the conversion of conventional refineries into facilities dedicated to the production of HVO-based renewable fuels (Hydrotreated Vegetable Oil). This transformation process began with the conversion of the Venice refinery (Porto Marghera) in 2014, considered the world’s first biorefinery, marking a milestone in industrial decarbonization strategies obtained from the adaptation of an existing petroleum refinery. Later, in 2019, the company completed a similar project at the Gela refinery in Sicily.

Both facilities operate using Ecofining™ technology, jointly developed by ENI and Honeywell UOP, a catalytic hydroprocessing process that converts vegetable oils, used cooking oils, and animal fats into paraffinic hydrocarbons compatible with fossil fuels. From these renewable feedstocks, the biorefineries primarily produce renewable diesel, along with other coproducts such as renewable propane (renewable LPG) and renewable naphtha, commonly referred to as bio-naphtha or HVO naphtha.

Beyond its use as a blending component in fuel mixtures, Eni has explored the potential of this bio-naphtha as a feedstock for the petrochemical industry. Due to its paraffinic composition and low sulfur and aromatic content, this stream can be used in processes such as steam cracking, where it is possible to produce renewable light olefins, including ethylene and propylene. These olefins can in turn be converted into polymers and plastics with a lower carbon footprint, aligned with advanced decarbonization strategies and broader low-emission industrial frameworks.

The model implemented by Eni illustrates how integration between refining and petrochemicals can become a key mechanism to maximize the value of renewable diesel coproducts while contributing to the transition toward industrial systems with lower climate impact. This approach is increasingly complemented by parallel developments in alternative renewable energy pathways, including renewable gas production strategies aligned with low-carbon fuel ecosystems, which reinforce the broader industrial decarbonization landscape.

Optimization of Steam Cracking with HVO Bio-Naphtha

The incorporation of HVO bio-naphtha as a feedstock in steam cracking units requires careful optimization of furnace operating conditions to maximize the production of light olefins while maintaining process stability. Although its highly paraffinic composition may favor the generation of ethylene and propylene, the behavior of the feedstock or raw material under high-temperature conditions requires specific adjustments in cracking severity and coke control systems.

Operational Severity Adjustment

One of the most relevant factors is the control of operational severity, primarily defined by the combination of temperature, pressure, and the steam-to-hydrocarbon ratio. In steam cracking furnaces, temperatures typically operate within elevated ranges to promote the cleavage of carbon–carbon bonds. However, when highly paraffinic streams such as HVO naphtha are processed, it becomes necessary to balance thermal severity to maximize olefin formation without excessively increasing secondary reactions.

The steam-to-hydrocarbon ratio also plays a key role, as steam reduces the partial pressure of hydrocarbons, improves heat transfer, and helps limit coke deposition on the internal surfaces of the reactor.

Coke Formation Control

Coke formation is one of the main operational challenges in cracking furnaces. To mitigate this phenomenon, several strategies are employed, including the use of advanced metallurgical materials in furnace coils, designed to withstand extreme temperatures and minimize carbon adhesion. In addition, coke inhibitors may be used—compounds that reduce the polymerization reactions responsible for the formation of solid deposits. Complementarily, furnaces require periodic cleaning cycles or decoking operations, necessary to remove accumulated carbon and maintain thermal efficiency.

Impact on Furnace Cycles and Maintenance

The composition of HVO bio-naphtha can influence the duration of furnace operating campaigns, since the rate of coke formation determines the frequency of shutdowns for decoking. Proper control of severity and feed composition helps extend operating cycles and reduce maintenance costs.

Recommended Operational Strategies

Among the most used strategies is the implementation of controlled blends between HVO naphtha and fossil naphtha, which allows gradual adjustment of feed behavior within the furnace. It is also recommended to apply pretreatment stages to remove trace contaminants, implement continuous coke monitoring systems, and maintain precise control of operational severity to optimize yield and process reliability.

Limitations and Challenges of Renewable Diesel

Despite its growing adoption in the energy sector as part of the transition toward low-carbon fuels, renewable diesel faces a series of technical and economic challenges that influence its large-scale expansion. One of the most relevant factors is the high hydrogen intensity required during the hydrotreating process. The removal of oxygen present in renewable feedstocks through hydrodeoxygenation (HDO) involves significant hydrogen consumption, which can increase operating costs, especially in refineries where hydrogen supply is limited or dependent on fossil sources.

Another important challenge is feedstock availability. The most commonly used raw materials—such as vegetable oils, used cooking oils, and animal fats—have a limited supply and compete with other industrial sectors, including food markets, biofuels, and oleochemicals. This competition for raw materials can generate price pressures and affect the economic viability of new projects.

In addition, there is the CAPEX associated with the conversion or construction of biorefineries, particularly when existing units must be adapted to process biogenic feedstocks. Finally, the actual carbon balance of renewable diesel depends on the origin of the feedstock, the energy consumption of the process, and the hydrogen source used, making it necessary to carefully evaluate its climate impact across the full life cycle.

Applicable Regulations and Standards

The expansion of renewable diesel in the energy market is supported by a set of technical standards and regulatory frameworks designed to ensure both fuel quality and the sustainability of the feedstocks used in its production. In the United States, the ASTM D975 standard defines the specifications for diesel fuel intended for internal combustion engines. Due to its paraffinic nature and the absence of oxygen in its molecular structure, renewable diesel produced through hydroprocessing can meet these specifications, enabling its use as a drop-in fuel within existing infrastructure.

In the European context, the EN 15940 standard regulates synthetic or hydrotreated paraffinic fuels, including HVO, establishing technical parameters such as cetane number, density, sulfur content, and fuel stability. In parallel, sustainability certification systems play a key role in ensuring feedstock traceability. Among them, ISCC (International Sustainability and Carbon Certification) stands out, widely used to verify the sustainable origin of oils and waste materials used in biofuel production.

At the level of energy policy, regulatory mechanisms such as the Low Carbon Fuel Standard (LCFS) and various renewable fuel content regulations encourage the adoption of renewable diesel through carbon credit schemes and mandatory emission reduction targets in the transportation sector.

Strategic Integration Toward the AFPM Annual Meeting 2026

The development of renewable fuels and the valorization of their coproducts reflect a growing trend toward integration between refining and petrochemicals, a topic that occupies a central place in the technical discussions at the AFPM Annual Meeting 2026. In this new landscape, refineries are evolving into industrial complexes capable of producing both lower-carbon fuels and petrochemical feedstocks.

The production of renewable diesel through hydroprocessing makes it possible to leverage existing infrastructure while simultaneously generating intermediate streams such as HVO naphtha, which can be integrated into petrochemical processes such as steam cracking. This technological convergence contributes to operational decarbonization by maximizing the value of renewable feedstocks while reducing exclusive dependence on fossil fuels.

In this context, the optimization of existing assets becomes a strategic factor for the competitiveness of the downstream sector. The incorporation of renewable streams into petrochemical value chains illustrates how modern refining can adapt to the energy and environmental demands of the future.

Conclusions

The evolution of renewable diesel demonstrates the growing role of renewable fuels in redefining industrial systems, as the energy transition does not only involve replacing fossil fuels but also reconfiguring the industrial architecture of refineries. In this context, HVO naphtha emerges as a strategic component that connects two historically separate domains: fuel production and the generation of advanced petrochemical feedstock streams. By being integrated as a feedstock in steam cracking units, this stream makes it possible to transform biorefining coproducts into light olefins, expanding the economic value of the process beyond the fuel market.

Steam cracking, traditionally associated with the processing of ethane or fossil naphtha, is therefore positioned as a valorization pathway for renewable streams, opening the door to the production of chemicals and polymers with a lower carbon footprint. This technological convergence represents a particularly relevant opportunity for complex refineries, capable of integrating hydroprocessing, fractionation, and petrochemical operations within the same industrial system.

Ultimately, the incorporation of streams such as HVO naphtha reflects a paradigm shift in the downstream sector: the refineries of the future will not only be fuel production centers, but integrated energy and chemical platforms, capable of leading the transition toward a more efficient, sustainable, and low-carbon fuels-driven industrial model.

References

1. Karaba, A., et al. (2021). Experimental evaluation of hydrotreated vegetable oils as novel feedstocks for steam-cracking process. Processes, 9(9), 1504.
   https://www.mdpi.com/2227-9717/9/9/1504 
2. Amin, A., et al. (2019). Review of diesel production from renewable resources. Journal of Energy Chemistry, 34, 192–200.
   https://www.sciencedirect.com/science/article/pii/S2090447919300905 
3. Concawe. (2022). Future diesel-like renewable fuels – Opportunities and challenges.
   https://www.concawe.eu/wp-content/uploads/Rpt-22-18.pdf 
4. Chart Industries / Howden. (2023). Hydrotreated vegetable oil (HVO): Sustainable fuels white paper.
   https://files.chartindustries.com/Howden_SustainableFuels_Whitepaper.pdf 
5. Martí, F. T., et al. (2025). Cracking of hydrotreated waste fats and oils for light olefin production. Fuel Processing Technology.
   https://www.sciencedirect.com/science/article/abs/pii/S0926337325008677 

Frequently Asked Questions (FAQs)