A cetane improver is a diesel fuel additive that raises the cetane number of the fuel. Because the fuel then ignites faster after injection, the engine runs quieter, starts easier and burns the fuel more completely. PETRONAX supplies the cetane improver INTRON® cTane 2EHN, based on 2-ethylhexyl nitrate, to refineries, blenders and fuel terminals worldwide.
What is the cetane number?
The cetane number describes how quickly diesel fuel ignites under compression. In other words, it measures the ignition delay: the short time between injection and the start of combustion. A high cetane number means a short delay. In contrast, a low cetane number means a long delay.
During a long delay, unburned fuel builds up in the cylinder. It then ignites all at once, which causes a sharp pressure rise known as diesel knock. As a result, the engine gets louder, wears faster, consumes more fuel and emits more smoke.
Labs measure the cetane number with a test engine under ASTM D613 or EN ISO 5165. For a quick estimate, the calculated cetane index (ASTM D4737) is often used as well.
Why diesel needs a cetane improver
Many refinery streams have a naturally low cetane number. For example, light cycle oil and other cracked distillates contain many aromatics, which ignite poorly. Likewise, severe hydrotreating and some crude grades lower the cetane quality of the final blend.
At the same time, fuel standards set firm limits. EN 590 requires a cetane number of at least 51 in Europe, while ASTM D975 sets a minimum of 40 for No. 2 diesel in the United States. A cetane improver closes this gap at a low treat rate, without changes to the refinery process.
How a cetane improver works
Most cetane improvers are alkyl nitrates. Among them, 2-ethylhexyl nitrate (2-EHN) is the most widely used one in industry. When the fuel is compressed and heated in the cylinder, 2-EHN breaks down. Consequently, it releases free radicals that start the oxidation of the fuel earlier.
Thus, the ignition delay gets shorter and combustion becomes smoother. Moreover, the effect is strongest at low engine loads and in cold starts, where the ignition delay is longest.
Benefits of the INTRON® cTane cetane improver
- Meets fuel specs. Above all, it brings diesel up to the cetane limits of EN 590, ASTM D975 and national standards.
- Low treat rate. Just 200–2,000 ppm is enough, so the cost per cetane point stays low.
- Flexible blending. Refiners can blend more low-cetane streams, such as light cycle oil, into the diesel pool.
- Better engine behaviour. In addition, easier cold starts, less noise and smoother running follow from the shorter ignition delay.
- Fully compatible. Moreover, it works together with detergents, stabilisers, corrosion inhibitors and other diesel additives.
- Simple dosing. Likewise, standard pumps or additive dosing units handle it, batch-wise or continuously.
Test results: cetane number before and after
In an engine test under ASTM D613, our cetane improver raised the cetane number of a base diesel from 45 to 52. Hence, the treated fuel met both the ASTM D975 and the EN 590 requirements. You can read the details in our ASTM D613 test report.
However, the gain in your own fuel depends on its starting cetane number and composition. Therefore, we confirm the dose with a test of your diesel.
Technical data of INTRON® cTane 2EHN
| Property | Typical value |
|---|---|
| Active component | 2-ethylhexyl nitrate (2-EHN) |
| Appearance | Clear to light yellow liquid |
| Density at 20 °C | 960–970 kg/m³ |
| Viscosity at 20 °C | 1.78 mm²/s |
| Pour point | −50 °C |
| Treat rate | 200–2,000 ppm |
| Shelf life | 12 months from production |
Typical values only, not a specification. For the full data, see the INTRON® cTane product page.
Dosage and blending
First, we review the cetane number and composition of your base diesel. Then our experts suggest a treat rate between 200 and 2,000 ppm. You can add the cetane improver as a concentrate or as a pre-blend with treated diesel. For example, use standard pumps in the liquid stream at refineries and terminals, or special additive dosing units, batch-wise or continuously.
Storage, handling and safety
Store the product below 60 °C, away from heat sources, sparks and direct sunlight. Under these conditions, the shelf life is 12 months from production.
Note that 2-EHN is harmful. In particular, long breathing of vapours may cause headache and drowsiness, and contact can irritate the eyes and skin. Therefore, wear protective clothing, gloves, goggles and a mask when you handle it. Finally, always read the current Safety Data Sheet before use.
Buy a cetane improver from PETRONAX
First, test a sample in your lab. After that, scale up to regular supply. Furthermore, we ship to customers in Europe, the Americas, the Middle East, Africa and Asia. Similarly, we supply 200 kg drums and IBC containers for smaller volumes. Finally, for larger volumes, we ship in ISO tank containers, road tankers or rail tank cars. Every shipment comes with a Certificate of Analysis and a Safety Data Sheet. To get an offer, request a quote or write to sales@petronaxcorp.com.
FAQ: cetane improver for diesel fuel
What is a cetane improver?
A cetane improver is a diesel fuel additive that raises the cetane number. As a result, the fuel ignites faster after injection, and the engine runs smoother and cleaner.
How does 2-EHN raise the cetane number?
Put simply, 2-ethylhexyl nitrate breaks down at the high temperature of compression. The free radicals it releases then start the combustion earlier, so the ignition delay gets shorter.
How much cetane improver do I need?
As a rule, the treat rate is 200 to 2,000 ppm. However, the gain depends on the base diesel, so we confirm the dose with a test of your fuel.
Which standards does the cetane number have to meet?
In Europe, EN 590 requires a cetane number of at least 51. In the US, ASTM D975 sets a minimum of 40 for No. 2 diesel. Labs measure it with ASTM D613 or EN ISO 5165.
Is 2-EHN hazardous?
Yes. It is harmful and can decompose when overheated. Therefore, store it below 60 °C, keep it away from heat sources and follow the Safety Data Sheet.
Related resources
- INTRON® cTane 2EHN – our cetane improver product page
- INTRON® cTane ASTM D613 test – cetane number from 45 to 52
- Boost diesel power with a cetane improver – blog article
- 2-ethylhexyl nitrate explained – blog article