Methanol is used as a gasoline component or in the form of ether (MTBE) in gasoline and Fatty Acid Ester (FAME) in diesel. High concentration methanol blends, such as M85 is used in special Flexible Fuel Vehicles (FFVs). Methanol is used in China as various blends ranging from M5 to M100. In some markets, the focus is on gasoline/ethanol/methanol blends (GEM) fuel blends. In many regions, for example in Europe and North America, blending of methanol is limited up to a few percentages in gasoline. Mid-level or high-level alcohol fuel blends could enable automakers to design high efficiency engines to compensate low energy density of methanol.
When considering methanol use as gasoline component, corrosion inhibitors, co-solvents, and alcohol compatible materials in vehicles are needed to resist phase separation, to maintain stability and safety.
Methanol can reduce emissions of carbon monoxide, hydrocarbons and nitrogen oxides when compared to gasoline. However, formaldehyde emissions tend to increase, especially at cold-starts. Methanol is biodegradable.
IEA AMF work on methanol:
Methanol was the primary alternative fuel considered for transport sector in 1970’s and 1980’s. At that time, the major driving force was to reduce dependence on fossil oil. Methanol was used as a transportation fuel until the mid-1990s in North America and Europe, and it is still used today, for example, in China, and in form of ether (MTBE) in gasoline and in the form of Fatty Acid Esters (FAME) in diesel. Methanol is also used for race cars and in some other specialty engine applications for its high octane numbers.
In China, methanol is used as a motor fuel in various blends ranging from 5% methanol in gasoline (M5) to 100% methanol (M100). Methanol accounts for 7-8% of China’s transportation fuel pool. Methanol-blended fuels are explored also by other countries, such us Israel, Australia, Sweden, Poland, United Kingdom, Iceland, Netherlands, Trinidad and Tobago, Iran, Pakistan, Vietnam, Azerbaijan, and Uzbekistan. In some markets, the focus is on blends of gasoline, ethanol and methanol (GEM). In this concept, ethanol is serving as a co-solvent for methanol. Higher blends containing 85 vol-% methanol and 15 vol-% gasoline (M85), can be used only in special Flexible Fuel Vehicles (FFVs), which were actually first developed for methanol and later on optimized for ethanol.
Methanol is typically produced from natural gas, but it can also be made from coal or biomass. Methanol is sometimes called “wood alcohol”, because it was once produced as a byproduct of wood distillation. (Methanol Institute). Today, biomethanol is also produced from glycerine, which is a byproduct from production of Fatty Acid Esters (BioMCN). Commercial-scale renewable methanol production facilities are now being operated, with the potential for multiple counting under the European Union’s Renewable Energy Directive. Even when produced from natural gas, methanol has a slight greenhouse gas emission benefit over gasoline. Methanol is one of the most common chemicals globally with capacity of about 95 million metric tons (IHS Chemical). According to a new IHS global market study, driven by Chinese demand growth, global methanol demand increased 23% from 2010 to 2012, and annual demand for the product is expected to increase from 61 million metric tons in 2012 to 146 MMT in 2022. Methanol prices are competitive with gasoline prices, even when considered on an energy equivalent basis (Bromberg and Cheng 2010). In fact, methanol prices in China are considerably lower than gasoline on an energy equivalent basis, and this has been a key factor driving the strong growth of methanol as a transportation fuel in China over the last years.
Auto manufacturer's recommendations for fuel gasoline qualities in the WWFC 2006 edition states that "Methanol is not permitted". In Europe, max. 3 vol-% methanol is allowed to be blended in gasoline under the Fuel Quality Directive (2009/30/EC) and CEN standard (EN 228). In the U.S., ASTM D 4814-10a limits methanol up to 0.3 vol-% or up to 2.75 vol-% with an equal volume of butanol, or higher molecular weight alcohol. U.S. EPA waivers under the substantially similar rule allow for methanol levels higher than ASTM D4814-10a, with the “Octamix” waiver allowing a maximum of 5% by volume methanol, with a minimum 2.5 vol-% co-solvents (one or a mixture of higher alcohols including ethanol, propanols, butanols and pentanols). ASTM D5797-07 standards specifying fuel methanol blends (M70- M85) are now being updated by an ASTM Task Force. Specifications for neat methanol exist as well, for example ASTM D-1152/97 and specification of the International Methanol Producers & Consumers Association.
In China, a national standard for M85 fuel containing up to 85% of methanol is approved to be used as motor fuel (Green Car Advisor 2009, Methanol Institute 2011). In addition, standards are in place in several provinces in China that govern the use of methanol in various blends with gasoline ranging from 5% to 100%, while a national standard for M15 fuel is in the final drafting stage. Table 1 shows some properties of methanol.
Table 1. Selected fuel properties of methanol.
The blending vapor pressure of methanol is high. This means that despite the low vapor pressure of neat methanol (32 kPa at 37.8 °C), the addition of methanol into gasoline results in an increase in vapor pressure of the blended fuel (Figure 1). This is due to the capability of methanol to form azeotropes with hydrocarbons of gasoline. However, when blending ratio of alcohol increases, vapor pressure gradually declines as illustrated in Ethanol chapter.
Figure 1. Increase of vapor pressure when blending methanol, ethanol, and alcohol blends with gasoline. (Methanol Institute a).
Methanol is more prone to phase separation than ethanol when blended with gasoline (Ethanol chapter). Methanol requires co-solvents to be blended with gasoline even at low concentrations to provide a stable fuel blend. Examples of possible co-solvents are isopropanol and tertiary butanol (Figure 2).
Figure 2. Water tolerance of methanol with co-solvents in gasoline. TBA = tertiary butanol; NBA = normal butanol; IPA = isopropanol. (Methanol Institute a).
Methanol may be introduced into the transport sector in low or high concentration blends for light duty or heavy duty applications.
Methanol is already used as a blending component for gasoline, however, in most regions, for example in Europe and North America, blending of methanol is limited up to a few percentages in gasoline. Infrastructure and cars are not designed for methanol use in these regions. When considering methanol use as gasoline component, corrosion inhibitors, co-solvents, and alcohol compatible materials in vehicles are needed to resist phase separation, maintain stability and safety. Materials and compatibility issues as well as safety aspects are discussed e.g. in the publications from The Methanol Institute. Aluminum, carbon steel, stainless steel, bronze, Flurel™, fluorosilicone, polysulfide rubber, Viton™, acetal, nylon, Teflon™, and fiberglass-reinforced are recommended materials. Materials that are not recommended include galvanized metals, Buna-N™, neoprene, polyurethane, and alcohol-based pipe dome. According to Bromberg and Cheng (2010) methanol fuels at any concentration can be very aggressive towards magnesium, and if water is present, towards aluminum. Corrosion inhibitor additives and formulated engine oils can be effective to reduce corrosive effects of methanol. Bromberg and Cheng (2010) mention that it is not clear if conventional fibre-reinforced tanks are compatible with methanol fuels at high temperatures, since adverse effects have been observed in this tank and lining material at 50 °C.
Methanol can be used as a high concentration blend, M85, in special FFV cars. Blends of gasoline, ethanol and methanol (GEM) are tri-component blends with constant air-to-fuel ratio of 9.7:1, which is same ratio as air-to-fuel ratio for E85 fuel (Figure 3). In these blends, ethanol serves as a co-solvent for methanol fuel blends. Behaviour of virtual and physical alcohol sensors used in the FFV cars have been studied with GEM blends, as well as performance of cars at cold temperatures, emissions and costs. The results indicate that GEM blends could be used in FFV cars as a drop-in alternative to E85 fuel (Turner et al. 2012).
Mid-level alcohol fuel blends (A20-A30) or high-level alcohol fuels could be considered as high octane fuels that would allow automakers to optimize cars with higher engine compression ratios, downsized engines, increased turbocharging, and enhanced direct injection. High engine efficiency could compensate for methanol’s low energy density. Bromberg and Cheng (2010) have also highlighted the potential of directly injected spark ignited engines for heavy-duty vehicles.
Figure 3. Gasoline, ethanol, methanol blends (GEM) with air-to-fuel ratio equivalent to conventional E85 fuel. (Turner et al. 2012).
Extensive reports and reviews of exhaust emissions with methanol fuels have been prepared by Bromberg and Cheng (2010), Bechtold et al. (2007) and Ohlström et al. (2001). Methanol can reduce emissions of carbon monoxide, hydrocarbons and nitrogen oxides when compared to gasoline. However, formaldehyde emissions tend to increase, especially at cold-starts.
Neat methanol burns with an invisible flame, which is a safety risk aspect. Otherwise methanol may be considered even as a safer fuel than gasoline, harder to ignite, slower burning, and producing one-eighth the heat of gasoline. Methanol, like all transportation fuels is toxic and should not be ingested. Methanol is readily biodegradable in both aerobic and anaerobic environments, and with a half-life in ground and surface water of one to six days.
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Methanol Institute b. Methanol Institute's Technical Product Bulletin: Methanol Gasoline Blends - Alternative Fuel For Today's Automobiles and Cleaner Burning Octane For Today's Oil Refinery. Available online: http://www.methanol.org/.../Blenders-Product- Bulletin-(Final).aspx
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Turner, J.W.G., Pearson, R.J., McGregor, M.A., Ramsay, J.M., Dekker, E., Iosefa, B., Dolan, G.A., Johansson, K. and Bergström, K. ac (2012) GEM Ternary blends: Testing Iso-stoichiometric mixtures of gasoline, ethanol, and methanol in a production Flex-Fuel Vehicle Fitted with a Physical Alcohol Sensor. Society of Automotive Engineers. SAE Technical Paper 2012-01-1279.