The methanol economy is a suggested future economy in which methanol and dimethyl ether replace fossil fuels as a means of energy storage, ground transportation fuel, and raw material for synthetic hydrocarbons and their products. It offers an alternative to the proposed hydrogen economy or ethanol economy.
In the 1990s, Nobel prize winner George A. Olah advocated a methanol economy; in 2006, he and two co-authors, G. K. Surya Prakash and Alain Goeppert, published a summary of the state of fossil fuel and alternative energy sources, including their availability and limitations, before suggesting a methanol economy.
Methanol can be produced from a wide variety of sources including still-abundant fossil fuels (natural gas, coal, oil shale, tar sands, etc.) as well as agricultural products and municipal waste, wood and varied biomass. It can also be made from chemical recycling of carbon dioxide.
In 2005, the Nobel laureate George A. Olah called for the creation of an economy in methanol in the essay Beyond Oil and Gas: The Methanol Economy and in 2006 together with two other co-authors published a book on this subject In these books, the authors summarize the status of fossil fuel sources and other alternative energy sources, their availability and limitations before suggesting the experimentation of the so-called methanol economy.
Methanol is a fuel that can be used both for thermal engines and for fuel cells. Thanks to its good octane number it can be used directly as fuel in cars (including hybrid cars and plug-in models) using various types of internal combustion engines already in use. Methanol can also be used in the fuel cell, either directly, in DMFC cells, or indirectly, after its transformation into hydrogen by reforming.
Under normal conditions, methanol is a liquid, which allows it to be easily stored, transported and distributed, similar to what is done with petrol and diesel. Chemically, it can also be rapidly transformed by dehydration into dimethyl ether, a diesel substitute that has a cetane number of 55.
In the years 2000, methanol is used on a large scale (about 37 million tons per year) as an elementary chemical brick to produce numerous complex chemicals and polymeric materials. In addition, it can be easily converted by the “methanol to olefin” (MTO) process in ethylene and propylene, unsaturated hydrocarbons which can be used to produce synthetic hydrocarbons of higher molecular weight and other derivatives thereof, which are normally obtained from petroleum and natural gas.
Sources of methanol
Methanol can be efficiently produced from a wide variety of sources, including some very abundant types of fossil fuel (natural gas, coal, oil shale, bituminous sand, etc.), but also from agricultural waste products and common rubbish differentiated urban, from wood, and from various types of biomass.
Recycling of carbon dioxide
A far more radical hypothesis is to obtain methanol from the chemical recycling of carbon dioxide. Initially the main source could be the emissions rich in CO 2 from power plants that burn fossil fuels or discharges from cement factories and other factories. In a longer time, considering the decrease in fossil fuel resources and the effect of their use on the Earth ‘s atmosphere, even the low concentration of CO 2natural could be captured and recycled to obtain methanol: in this way it would be a supplement to the same natural cycle of photosynthesis. New, more efficient absorbing substances are being developed, capable of capturing atmospheric CO 2, which in some cases mimic the action of living plants. The chemical recycling of CO 2 to obtain new fuels and materials could then become possible and sustainable, making these “non-fossil carbon fuels” renewable on a time scale comparable to human lifespan. In Iceland, in 2011/2012, a production of two million liters of methanol per year has already begun with this system.
Methanol is a fuel for heat engines and fuel cells. Due to its high octane rating it can be used directly as a fuel in flex-fuel cars (including hybrid and plug-in hybrid vehicles) using existing internal combustion engines (ICE). Methanol can also be burned in some other kinds of engine or to provide heat as other liquid fuels are used. Fuel cells, can use methanol either directly in Direct Methanol Fuel Cells (DMFC) or indirectly (after conversion into hydrogen by reforming).
In internal combustion engines (ICE)
Methanol has a high octane number (RON of 107 and MON of 92), which makes it an adequate substitute for gasoline. It has a higher flame speed than petrol, which leads to greater efficiency as well as greater latent vaporization heat (3.7 times higher than petrol), which implies that the heat generated by the engine can be removed more effectively, making it possible to use air-cooled engines. Furthermore, methanol burns producing less polluting than petrol and is safer in the case of fire. However, methanol has only half the energy content per volume compared to gasoline (8,600 BTU / pound).
In compression ignition engines (diesel engine)
Methanol by itself is a bad substitute for diesel fuels. But, due to chemical dehydration, methanol can be transformed into dimethyl ether (DME), which is instead a good diesel fuel with a cetane number of 55-60, better than the cetane number 45-55 of regular diesel. Compared to diesel fuels, DME has much lower emissions of particulate matter, NO x and CO and does not emit any type of sulfur dioxide or sulfur dioxide (SO x). Methanol is also used to produce biodiesel, through the transesterification of vegetable oils.
In advanced engines or in fuel cells fueled by methanol
The use of methanol and ether-dimethyl can be combined with hybrid engine and electric car technologies, so as to obtain a greater mileage (kilometers per liter) and lower emissions. These fuels can be used in both fuel cells and catalysts that operate reforming by obtaining hydrogen to feed the fuel cell, or directly “burning” methanol in direct methanol fuel cells (DMFCs).
For the production of electricity
Methanol and DME can be used in gas turbines to generate electricity. The currently very expensive fuel cell (PAFC, MCFC, SOFC) models can be used for electricity generation, especially in environments where low noise is required, in addition to low heat generation, such as hospitals; or a very low weight of the plant, as in air or space transport vehicles.
As a domestic fuel
Methanol and DME can be used in commercial buildings and homes to generate heat and / or electricity. The DME can be used in commercial gas stoves / kitchens, without major modifications. In developing countries, methanol could be used as a fuel for the kitchen, since it burns much cleaner than wood (less nano-particles and CO), and in this way reduces some of the problems related to domestic pollution.. It should however be mixed with petrol, diesel, or with coloring-adulterants, in order to avoid any possible fraud, and the lethal use as an additive to drinks, an event that occurred in Italy with the methanol wine scam.
Basic element for chemistry and polymeric materials
Currently methanol is widely used on a large scale as a base material for producing a variety of chemicals and other products such as plastics polymers. With the process known as “methanol to gasoline” (MTG), methanol can be transformed into gasoline. Using the “methanol to olefin” (MTO) process, methanol can be converted into ethylene and propylene alkenes, the two chemicals manufactured in greater quantities by the petrochemical industry. These are important building blocks for the production of essential polymers (LDPE, HDPE, PP) and other chemical intermediates that are currently produced from petroleum derivatives. Their production starting from methanol could therefore reduce dependence on oil. It will also make it possible to continue producing these basic chemicals and plastics, even after the end of fossil fuel depots.
Methanol is already used today on a large scale to produce a variety of chemicals and products. Global methanol demand as a chemical feedstock reached around 42 million metric tonnes per year as of 2015. Through the methanol-to-gasoline (MTG) process, it can be transformed into gasoline. Using the methanol-to-olefin (MTO) process, methanol can also be converted to ethylene and propylene, the two chemicals produced in largest amounts by the petrochemical industry. These are important building blocks for the production of essential polymers (LDPE, HDPE, PP) and like other chemical intermediates are currently produced mainly from petroleum feedstock. Their production from methanol could therefore reduce our dependency on petroleum. It would also make it possible to continue producing these chemicals when fossil fuels reserves are depleted.
Today most methanol is produced from methane through syngas. Trinidad and Tobago is currently the world’s largest methanol exporter, with exports mainly to the United States. The natural gas that serves as feedstock for the production of methanol comes from the same sources as other uses. Unconventional gas resources such as coalbed methane, tight sand gas and eventually the very large methane hydrate resources present under the continental shelves of the seas and Siberian and Canadian tundra could also be used to provide the necessary gas.
The conventional route to methanol from methane passes through syngas generation by steam reforming combined (or not) with partial oxidation. New and more efficient ways to convert methane into methanol are also being developed. These include:
Methane oxidation with homogeneous catalysts in sulfuric acid media
Methane bromination followed by hydrolysis of the obtained bromomethane
Direct oxidation of methane with oxygen
Microbial or photochemical conversion of methane
Partial methane oxidation with trapping of the partially oxidized product and subsequent extraction on copper and iron exchanged Zeolite (e.g. Alpha-Oxygen)
All these synthetic routes emit the greenhouse gas carbon dioxide CO2. To mitigate this, methanol can be made through ways minimizing the emission of CO2. One solution is to produce it from syngas obtained by biomass gasification. For this purpose any biomass can be used including wood, wood wastes, grass, agricultural crops and their by-products, animal waste, aquatic plants and municipal waste. There is no need to use food crops as in the case of ethanol from corn, sugar cane and wheat.
Biomass → Syngas (CO, CO2, H2) → CH3OH
Methanol can be synthesized from carbon and hydrogen from any source, including still available fossil fuels and biomass. CO2 emitted from fossil fuel burning power plants and other industries and eventually even the CO2 contained in the air, can be a source of carbon. It can also be made from chemical recycling of carbon dioxide, which Carbon Recycling International has demonstrated with its first commercial scale plant. Initially the major source will be the CO2 rich flue gases of fossil-fuel-burning power plants or exhaust from cement and other factories. In the longer range however, considering diminishing fossil fuel resources and the effect of their utilization on earth’s atmosphere, even the low concentration of atmospheric CO2 itself could be captured and recycled via methanol, thus supplementing nature’s own photosynthetic cycle. Efficient new absorbents to capture atmospheric CO2 are being developed, mimicking plants’ ability. Chemical recycling of CO2 to new fuels and materials could thus become feasible, making them renewable on the human timescale.
Methanol can also be produced from CO2 by catalytic hydrogenation of CO2 with H2 where the hydrogen has been obtained from water electrolysis. This is the process used by Carbon Recycling International of Iceland. Methanol may also be produced through CO2 electrochemical reduction, if electrical power is available. The energy needed for these reactions in order to be carbon neutral would come from renewable energy sources such as wind, hydroelectricity and solar as well as nuclear power. In effect, all of them allow free energy to be stored in easily transportable methanol, which is made immediately from hydrogen and carbon dioxide, rather than attempting to store energy in free hydrogen.
CO2 + 3H2 → CH3OH + H2O
or with electric energy
CO2 +5H2O + 6 e−1 → CH3OH + 6 HO−1
6 HO−1 → 3H2O + 3/2 O2 + 6 e−1
CO2 +2H2O + electric energy → CH3OH + 3/2 O2
The necessary CO2 would be captured from fossil fuel burning power plants and other industrial flue gases including cement factories. With diminishing fossil fuel resources and therefore CO2 emissions, the CO2 content in the air could also be used. Considering the low concentration of CO2 in air (0.04%) improved and economically viable technologies to absorb CO2 will have to be developed. For this reason, extraction of CO2 from water could be more feasible due to its higher concentrations in dissolved form. This would allow the chemical recycling of CO2, thus mimicking nature’s photosynthesis.
In the process of photosynthesis, green plants use the energy of sunlight to split water into free oxygen (which is released) and free hydrogen. Rather than attempt to store the hydrogen, plants immediately capture carbon dioxide from the air to allow the hydrogen to reduce it to storable fuels such as hydrocarbons (plant oils and terpenes) and polyalcohols (glycerol, sugars and starches). In the methanol economy, any process which similarly produces free hydrogen, proposes to immediately use it “captively” to reduce carbon dioxide into methanol, which, like plant products from photosynthesis, has great advantages in storage and transport over free hydrogen itself.
Methanol is a liquid under normal conditions, allowing it to be stored, transported and dispensed easily, much like gasoline and diesel fuel. It can also be readily transformed by dehydration into dimethyl ether, a diesel fuel substitute with a cetane number of 55.
Comparison with hydrogen
Methanol economy advantages compared to a hydrogen economy:
Efficient energy storage by volume, as compared with compressed hydrogen. When hydrogen pressure-confinement vessel is taken into account, an advantage in energy storage by weight can also be realized. The volumetric energy density of methanol is considerably higher than liquid hydrogen, in part because of the low density of liquid hydrogen of 71 grams/litre. Hence there is actually more hydrogen in a litre of methanol (99 grams/litre) than in a litre of liquid hydrogen, and methanol needs no cryogenic container maintained at a temperature of -253 °C.
A liquid hydrogen infrastructure would be prohibitively expensive. Methanol can use existing gasoline infrastructure with only limited modifications.
Can be blended with gasoline (for example in M85, a mixture containing 85% methanol and 15% gasoline).
User friendly. Hydrogen is volatile, and its confinements uses high pressure or cryogenic systems.
Less losses: Hydrogen leaks more easily than methanol. Heat will evaporate liquid hydrogen, giving expected losses up to 0.3% per day in storage tanks. (see Chart Ferox storage tanks Liquid oxygen).
Comparison with ethanol
Can be made from any organic material using proven technology going through syngas. There is no need to use food crops and compete with food production. The amount of methanol that can be generated from biomass is much greater than ethanol.
Can compete with and complement ethanol in a diversified energy marketplace. Methanol obtained from fossil fuels has a lower price than ethanol.
Can be blended in gasoline like ethanol. In 2007, China blended more than 1 billion US gallons (3,800,000 m3) of methanol into fuel and will introduce methanol fuel standard by mid-2008. M85, a mixture of 85% methanol and 15% gasoline can be used much like E85 sold in some gas stations today.
High energy costs currently associated with generating and transporting hydrogen offsite.
Depending on the feedstock the generation in itself may be not clean.
Presently generated from natural gas still dependent on fossil fuels (although any combustible hydrocarbon can be used).
Energy density (by weight or volume) one half of that of gasoline and 24% less than ethanol
If no inhibitors are used, methanol is corrosive to some common metals including aluminum, zinc and manganese. Parts of the engine fuel-intake systems are made from aluminum. Similar to ethanol, compatible material for fuel tanks, gasket and engine intake have to be used.
As with similarly corrosive and hydrophilic ethanol, existing pipelines designed for petroleum products cannot handle methanol. Thus methanol requires shipment at higher energy cost in trucks and trains, until new pipeline infrastructure can be built, or existing pipelines are retrofitted for methanol transport.
Methanol, as an alcohol, increases the permeability of some plastics to fuel vapors (e.g. high-density polyethylene). This property of methanol has the possibility of increasing emissions of volatile organic compounds (VOCs) from fuel, which contributes to increased tropospheric ozone and possibly human exposure.
Low volatility in cold weather: pure methanol-fueled engines can be difficult to start, and they run inefficiently until warmed up. This is why a mixture containing 85% methanol and 15% gasoline called M85 is generally used in ICEs. The gasoline allows the engine to start even at lower temperatures.
With the exception of low level exposure, methanol is toxic. Methanol is lethal when ingested in larger amounts (30 to 100 mL). But so are most motor fuels, including gasoline (120 to 300 mL) and diesel fuel. Gasoline also contains small amounts of many compounds known to be carcinogenic (e.g. benzene). Methanol is not a carcinogen, nor does it contain carcinogens. However, methanol may be metabolized in the body to formaldehyde, which is both toxic and carcinogenic. Methanol occurs naturally in small quantities in the human body and in edible fruits.
Methanol is a liquid: this creates a greater fire risk compared to hydrogen in open spaces as Methanol leaks do not dissipate. Methanol burns invisibly unlike gasoline. Compared to gasoline, however, methanol is much safer. It is more difficult to ignite and releases less heat when it burns. Methanol fires can be extinguished with plain water, whereas gasoline floats on water and continues to burn. The EPA has estimated that switching fuels from gasoline to methanol would reduce the incidence of fuel related fires by 90%.
Methanol is water-soluble: accidentally released, it may undergo relatively rapid groundwater transport, causing groundwater pollution, although this risk has not been thoroughly studied. An accidental release of methanol in the environment would, however, cause much less damage than a comparable gasoline or crude oil spill. Unlike these fuels, methanol is biodegradable and totally soluble in water, and would be rapidly diluted to a concentration low enough for microorganism to start biodegradation. This effect is already exploited in water treatment plants, where methanol is already used for denitrification and as a nutrient for bacteria.
Methanol and its derivatives, such as dimethyl ether, can then be used to generate electricity both in classic internal combustion engines and as fuel in methanol fuel cells.
Storage, transport and distribution of the methanol, which is liquid at room temperature, can use the existing infrastructure and technology. Wide distances between consumers and producers of regenerative energies can then be efficiently bridged. The energy storage density is about 50% of the storage density for gasoline and diesel.
In Iceland, Carbon Recycling International operates a methanol production plant. The plant was named after Olah.
In Germany there is a project of the Carbon2Chem initiative of ThyssenKrupp and the Federal Ministry of Education and Research for the production of methanol from smelters.
According to a study by the consulting firm Methanol Market Services Asia (MMSA), it is estimated that worldwide capacity will increase by 55.8 million tonnes in 2027, of which 38 million tonnes will be used as fuel.
The production of methanol in China is mainly based on coal and is to be used both as high methanol-containing fuel such as M85 and M100 and as a derivative such as dimethyl ether. In 2007, the price of spot methanol in China was about 40% of the price of gasoline. State commissions in China are working on national methanol fuel standards, Chinese automakers are working on improved methanol engines.
The Chinese capacity for dimethyl ether production from methanol is expected to rise from just under one million tonnes in 2007 to over six million tonnes. The company Sinopec alone wants to expand its DME capacity to three million tons.
Source from Wikipedia