Octane: Properties, Uses & Industrial Specifications
Octane is a hydrocarbon in the alkane family with the molecular formula C₈H₁₈ and CAS number 111-65-9 for n-octane. It is relevant to petroleum refining, fuel research, and hydrocarbon processing. The term octane number, however, refers to gasoline’s resistance to engine knocking rather than the concentration of this compound in fuel.
Understanding the difference between a specific hydrocarbon and a fuel rating helps refineries, fuel formulators, and industrial buyers evaluate fuel quality and select suitable materials.
At a Glance
This hydrocarbon has several structural isomers with different molecular structures and physical properties. Iso-octane, specifically 2,2,4-trimethylpentane, serves as the 100-point reference in the conventional gasoline-rating scale.
What Is This Hydrocarbon?
The compound contains eight carbon atoms and belongs to the alkane family, which consists of saturated hydrocarbons. Its structural isomers include straight-chain n-octane and various branched-chain compounds.
In the conventional reference system for gasoline knock resistance, iso-octane is assigned a value of 100 and n-heptane a value of 0. A fuel’s rating reflects its performance in standardized engine tests; it does not indicate the percentage of a particular hydrocarbon present in the fuel.
Technical Specifications
| Specification | Typical Value for n-Octane |
|---|---|
| Product Name | n-Octane |
| Chemical Name | Octane |
| CAS Number | 111-65-9 |
| Molecular Formula | C₈H₁₈ |
| Molecular Weight | 114.23 g/mol |
| Appearance | Clear, colorless liquid |
| Density at approximately 20°C | Approximately 0.70 g/cm³ |
| Boiling Point at Atmospheric Pressure | Approximately 125.6°C |
| Melting Point | Approximately −56.8°C |
| Water Solubility | Practically insoluble |
| Chemical Family | Alkanes |
These are typical reference values for n-octane. Specifications may differ for other isomers or commercial mixtures. Confirm the applicable product specification and Safety Data Sheet (SDS) before purchase or handling.
What Is a Gasoline Octane Rating?
A fuel rating measures gasoline’s resistance to knocking under standardized test conditions. Engine knock occurs when part of the fuel-air mixture ignites abnormally, potentially affecting performance and causing damage under certain operating conditions.
Using the grade recommended by the vehicle manufacturer helps ensure appropriate engine operation. A higher-rated fuel does not automatically improve power or fuel economy in an engine designed for a lower grade.
Types of Fuel Ratings
Research Octane Number (RON)
RON measures knock resistance under standardized conditions using a designated single-cylinder test engine. It is used in many countries as a gasoline-quality indicator.
Motor Octane Number (MON)
MON is determined under a different, generally more demanding set of test conditions. The difference between RON and MON helps characterize fuel behavior under varying operating conditions.
Anti-Knock Index (AKI)
AKI is calculated as the average of RON and MON: (RON + MON) / 2. It is commonly displayed on gasoline pumps in the United States and Canada.
Industrial Applications
Petroleum Refining
Refineries use processes such as catalytic reforming, isomerization, and alkylation to produce gasoline blend components with desired properties. These processes affect fuel composition and knock resistance; they are not simply methods of adding n-octane to gasoline.
Fuel Formulation and Testing
Hydrocarbon components and reference fuels are used in formulation, laboratory testing, and research into combustion behavior. The appropriate material depends on the specific test method and formulation requirements.
Automotive Engineering
Resistance to engine knock is important when designing and calibrating engines, particularly those with high compression ratios or turbocharging. The required fuel grade depends on engine design and the manufacturer’s recommendations.
Energy Research
Researchers use standardized fuel ratings to compare gasoline performance and investigate combustion behavior. These measurements help evaluate formulations under defined test conditions.
Factors to Consider When Selecting Fuel
- Follow the fuel grade specified by the vehicle manufacturer.
- Distinguish between a hydrocarbon’s chemical identity and a fuel’s rating.
- Consider the relevant regional measurement system, such as RON or AKI.
- Evaluate specifications and regulatory requirements before blending or industrial use.
Global Fuel Market Context
Demand for gasoline blend components and high-quality fuels is influenced by vehicle technology, refinery capacity, fuel regulations, and regional consumption patterns. Refiners optimize formulations to meet performance specifications and applicable environmental standards.
Demand for individual hydrocarbons differs from demand for fuel additives and finished gasoline. These products should not be treated as interchangeable categories.
Handling and Storage
- Store in compatible, tightly closed containers or approved tanks.
- Keep away from ignition sources, sparks, and hot surfaces.
- Provide suitable ventilation and follow applicable flammable-liquid requirements.
- Use appropriate protective equipment when handling the material.
- Prevent releases to drains and the environment.
- Follow the supplier’s SDS and local transport and storage regulations.
Explore Chemical Products and Resources
Visit the AasadChimie product catalog to explore available chemical products. For information about supply, specifications, and packaging, contact the team through the contact page.
You can also browse our chemical articles and industry resources for related technical information.
International Sources and References
- PubChem – Octane
- U.S. Energy Information Administration – Gasoline
- U.S. Department of Energy
- American Petroleum Institute
What is octane?
Octane is a hydrocarbon belonging to the alkane family, with the molecular formula C₈H₁₈. It has several structural isomers and is relevant to petroleum refining, hydrocarbon processing, and fuel research.
What is the difference between octane and octane number?
Octane is a chemical compound, while the octane number measures gasoline's resistance to engine knocking. A fuel's octane rating does not indicate how much octane it contains.
What is the chemical formula of n-octane?
The chemical formula of n-octane is C₈H₁₈, its molecular weight is approximately 114.23 g/mol, and its CAS number is 111-65-9.
What are the physical properties of n-octane?
n-Octane is a clear, colorless liquid with a density of approximately 0.70 g/cm³ at 20°C. Its boiling point is approximately 125.6°C, and it is practically insoluble in water.
What is iso-octane?
Iso-octane commonly refers to 2,2,4-trimethylpentane, a branched-chain hydrocarbon used as the 100-point reference in the conventional octane-rating scale.
What is the difference between RON, MON, and AKI?
RON (Research Octane Number) and MON (Motor Octane Number) measure knock resistance under different standardized test conditions. AKI (Anti-Knock Index) is the average of RON and MON and is commonly displayed on fuel pumps in the United States and Canada.
Does higher-octane gasoline always improve engine performance?
No. Higher-octane gasoline does not automatically increase power or fuel economy. The benefits depend on engine design, operating conditions, and whether the manufacturer recommends or requires a higher octane grade.
How is octane relevant to petroleum refining?
Octane-related properties are important when refiners formulate gasoline. Processes such as catalytic reforming, isomerization, and alkylation help produce blending components with the required fuel characteristics.
Is n-octane flammable?
Yes. n-Octane is a flammable hydrocarbon liquid. It must be kept away from ignition sources and handled with appropriate ventilation, protective equipment, and fire-safety precautions.
How should n-octane be stored?
Store it in tightly closed, compatible containers in a suitable, well-ventilated area away from heat, sparks, and open flames. Always follow the supplier's Safety Data Sheet (SDS) and applicable storage regulations.