When a driver fills their tank, it is unlikely they have octane on their mind, even if they are choosing between regular and premium gasoline. However, in the refining world, we know that much more goes on behind the scenes for customers to be able to make this choice. Above all, octane is more than just a consumer option at the pump, it is a critical marker of performance and value.
As things currently stand, preserving octane during processing is no simple feat for refiners as they grapple with complexities such as environmental regulations, cost pressures and shifting global fuel demands associated with the process.
Today’s refiners, therefore, face the increasingly delicate balancing act of meeting ultra-low sulfur specifications while managing inevitable octane loss. Add in the commercial realities of competitive markets, raw material costs and sustainability expectations, and the challenge becomes even deeper.
This is where advancements in catalyst technology are helping refiners address the challenge by improving desulfurization activity, allowing reactors to operate at lower temperatures, while maintaining octane selectivity, supporting both compliance and operating economics.
Why octane matters. An octane rating measures how resistant a fuel is to knocking—in other words, how much it can be compressed before auto-igniting. For example, a higher octane number means the fuel is better at preventing knocking (which can harm an engine), making high-octane fuel more valued. For consumers, this difference between low- and high-octane fuel shows up in price; but for refiners, the gap represents a bigger commercial lever.
In the refining process, reducing sulfur content, a regulatory requirement in most markets, can come at the cost of octane. In the U.S., for example, the Environmental Protection Agency (EPA) mandates a reduction in federal gasoline sulfur emissions standard from 30 parts per million (ppm) to 10 ppm, which would apply to refiners and importers.1 Other respective regions also carry their own regulations, such as the EU’s European Union Sulphur Directive, supporting the worldwide initiative for sulfur reduction.2 While these measures deliver clear air quality benefits, the hydrodesulfurization (HDS) units used to remove the sulfur can also strip away valuable octane from the product, resulting in the tricky tradeoff between environmental compliance and product value.
The current industry landscape. Hydrotreating of cracked gasoline, particularly fluid catalytic cracking (FCC) naphtha, is a critical step in producing compliant fuels, but it is also a sensitive unit operation. Any loss of octane during sulfur removal impacts the refinery’s ability to deliver premium-grade fuels and, in turn, reduces profitability.
At the core of these challenges are two key components, selectivity and activity:
High selectivity (i.e., octane retention): This is essential for refiners in gasoline hydrotreating. It refers to the ability to remove sulfur while preserving as much octane as possible. All catalysts will lose some octane to achieve lower sulfur targets, but optimizing selectivity helps refiners retain as much octane as possible without compromising sulfur removal.
Activity (referring to energy and cost efficiency): This pertains to the temperature required to achieve a target level of sulfur removal. Higher operating temperatures drive up energy consumption and costs. This is why refiners look to catalysts that achieve high sulfur removal at lower temperatures, offering the valuable benefits of energy savings, reduced carbon dioxide (CO2) emissions, and extended cycle length, reducing long-term catalyst changeout costs.
Shaping a more sustainable approach. Catalyst regeneration—the process of reusing spent catalysts instead of replacing them with new ones—has long been a proven option in hydroprocessing applications. Extending a catalyst’s useful life delivers significant cost-savings, reducing fresh catalyst purchases while also reducing landfill waste, cutting demand for mined raw materials and lowering overall lifecycle emissions. Until recently, however, regenerated catalysts were less common in cracked gasoline HDS service due to the demanding selectivity requirements.
Today, refiners can benefit from both the cost savings of catalyst reuse as well as performance levels equivalent to fresh products by combining targeted regeneration with tailored catalyst selection.
Innovations such as the authors’ company’s catalysta enable refiners to meet ultra-low sulfur targets while maintaining the same octane selectivity as fresh alternatives but at lower operating temperatures thanks to improved desulfurization activity. Built on selectively regenerated nickel-molybdenum (NiMo) and cobalt-molybdenum (CoMo) catalysts optimized for FCC gasoline HDS units, The company’s catalysta helps refiners cut changeout costs and conserve raw materials without sacrificing cycle length or fuel quality.
In testing, the catalysta has demonstrated:
Maintained selectivity: Retaining octane at similar levels to fresh catalysts and protecting product value in markets where the price gap between high- and low-octane fuel is significant.
Improved activity at lower temperatures: Allowing refiners to achieve target sulfur removal while running units at lower severity, which reduces energy use and extends cycle length.
These performance characteristics address both the primary driver (octane retention at fresh catalyst levels) and the secondary benefit (cycle length in a way that can be applied in real-world refining conditions).
Overcoming barriers to adoption. In one study, catalyst comparisons were conducted using an X4500 high-throughput testing unit developed by hte GmbH, a specialist in catalyst testing technology. This parallel trickle-bed reactor system allows up to 16 catalysts to be evaluated simultaneously under identical, tightly controlled feed and operating conditions. Testing 16 reactors in parallel requires around 30 liters (l)–50 l of feed per week with independent temperature control to enable multi-condition screening in a single run.
The X4500’s precision in feed distribution and temperature management ensures reproducibility even with challenging FCC naphtha feeds, enabling statistically robust side-by-side performance comparisons (FIG. 1). This approach provided a reliable basis for benchmarking the company’s catalysta against existing commercial alternatives.
When considering the two key pillars of activity and selectivity, trials found that the catalysta delivered high desulfurization activity at lower temperatures while maintaining octane selectivity equivalent to fresh catalysts (FIG. 2).
Lower operating temperatures translate directly into lower energy use, while extended cycle lengths contribute to reduced catalyst changeout frequency and overall operating costs.
The road ahead. For today’s refineries, the challenge is not just to meet today’s fuel specifications but to do so in ways that make sense for both the balance sheet and long-term sustainability goals. Catalyst technology in FCC gasoline HDS is advancing toward a model that supports compliance, performance and cost-effectiveness. While octane loss remains unavoidable when meeting lower sulfur targets, the ability to maintain octane selectivity equivalent to fresh catalysts—at lower operating temperatures and with the cost benefits of catalyst reuse—adds new dimensions to how refiners manage value.
In a competitive environment where cost control is paramount and environmental pressures continue to mount, solutions like the authors’ company’s catalysta demonstrate that it is possible to work within tight regulatory limits without sacrificing operating economics or cycle length, and with the added benefit of reducing waste and raw material demand. HP
NOTES
Evonik’s OctaMax™ catalyst
LITERATURE CITED
U.S. Environmental Protection Agency (U.S.), “Sulfur dioxide (SO2) pollution,” online: Sulfur Dioxide (SO2) Pollution | US EPA
European Union, “EUR-Lex, European Union Sulphur Directive” online: Directive - 2016/802 - EN - EUR-Lex
With a background in chemistry, Ryan Seyler has spent 5 yrs at Evonik and now works as a Technical Business Manager. She specializes in translating technical insight into commercially relevant solutions and working closely with cross-functional teams.
Dan Miskin leads Hydroprocessing Catalyst RD&I Americas at Evonik, specializing in hydroprocessing technologies within the catalyst business line. His experience includes 5 yrs in refining as a production engineer, with current work centered on solutions for catalyst reuse, renewable feedstocks and advanced plastic recycling.