What Cetane Number Measures
Cetane number (CN) is a measure of a diesel fuel's ignition delay; the time between fuel injection and the start of combustion. A higher CN means shorter ignition delay, producing smoother pressure rise, reduced combustion noise, better cold startability, and lower hydrocarbon and NOx emissions from incomplete combustion during warmup.
Minimum CN specifications vary by market: EN 590 requires CN ≥ 51 in Europe; Indonesian SNI standards and most Southeast Asian markets require CN ≥ 48-51 for commercial diesel. The base CN of distillate stocks varies significantly depending on crude origin and refining process. This catalytic cracking produces lower-CN streams than straight-run distillate, creating a consistent need for CN improvement at the blending stage.
Refinery economics: Cetane Number Improvers provide a direct, cost-accessible route to upgrading distillate stocks, allowing refiners to blend higher proportions of low-CN cracked streams while maintaining specification compliance and improving overall refinery economics.
Chemistry and Mechanism
These thermally labile compounds decompose rapidly at diesel combustion temperatures (above 150°C), generating reactive radicals that initiate fuel oxidation and shorten the ignition delay chain through a chemical rather than physical mechanism.
Several distinct chemical approaches are available in the market, each offering a different balance of CN lift efficiency, treat cost, and performance profile across varying diesel base stocks. The right choice depends on the starting cetane of the base fuel, the target CN lift required, blend composition, and total cost-in-use. Lamurindo works with customers to identify the most cost-effective option for their specific fuel pool.
Performance Benefits
- Reduced ignition delay results in smoother combustion pressure rise and less "diesel knock", particularly important for older high-compression engines and cold climates.
- Cold-start improvement: at low ambient temperatures, higher CN fuels start more reliably with reduced white smoke (unburned hydrocarbons) during warmup.
- Shorter ignition delay reduces the premixed combustion fraction, lowering NOx formation and particulate matter during transient engine operation.
- Enables blending of cycle oil and other FCC-derived low-CN streams at higher ratios without specification failure.
- Compatible with biodiesel/FAME blends. FAME has naturally higher CN than petroleum diesel, but blending with lower-CN petroleum components may still require CNI correction to meet specification.
Treat Rate and Diminishing Returns
Cetane improvers exhibit diminishing returns. The CN lift per unit of additive decreases as treat rate increases. Typical treat rates range from 500 to 3,000 mg/kg, delivering 2 to 8 CN points depending on the base fuel's paraffin distribution and starting CN. Highly aromatic fuels (LCO-heavy blends) show reduced responsiveness and may require higher doses. Technical screening against your specific base stock is recommended for optimal treat rate determination.