|1-butanol is less volatile than ethanol, and butanol-gasoline blends are less volatile than ethanol blends. Adding a fraction of butanol to an ethanol blend brings down the volatility. Click to enlarge. Source: BP|
New fuel testing results on bio-derived 1-butanol presented by DuPont and BP at the SAE World Congress indicate that biobutanol has proven to perform similarly to unleaded gasoline on key parameters, based on ongoing laboratory-based engine testing and limited fleet testing.
According to BP Biofuels program manager Frank Gerry, biobutanol formulations meet key characteristics of a “good” fuel, including high energy density, controlled volatility, sufficient octane and low levels of impurities.
He described early testing data that indicate that biobutanol fuel blends at a nominal 10 vol% level perform very similarly to unleaded gasoline fuel. Additionally, the energy density of biobutanol is closer to unleaded gasoline.
Butanol does not phase-separate in the presence of water, unlike ethanol. With a lower oxygen content than ethanol, higher volumetric concentrations of butanol could be blended into gasoline while still adhering to oxygen limits. Fuel testing also has proven that biobutanol does not phase separate in the presence of water, and has no negative impact on elastomer swelling.
Combined with ethanol in gasoline blends, butanol can bring down the vapor pressure of the fuel.
|1 Blend values of alcohol octane numbers and vapor pressure.|
2 Summer / Winter specifications.
|Sp. Gravity 60/60 F||0.794||0.814||0.720 - 0.775|
|Heating Value [MJ/l]||21.1 - 21.7||26.9 - 27.0||32.2 - 32.9|
|RON||106 - 1301||941||95|
|MON||89 - 1031||80 - 811||85|
|Rvp@ 5% / 10% [psi]||311 / 201||6.41 / 6.41||< 7.8 / 152|
|Oxygen [%wt]||34.7||21.6||< 2.7|