Methyl Alcoholเมทานอล, Methanol, เมทิลแอลกอฮอล์, Methyl Alcohol, MeOH
เมทานอล (อังกฤษ: methanol) หรือ เมทิลแอลกอฮอล์ (อังกฤษ: methyl alcohol) มีสูตรโครงสร้างแบบย่อ CH3OH เป็นของเหลวใส ระเหยง่าย เป็นพิษ นิยมใช้เป็นตัวทำละลาย และใช้เป็นเชื้อเพลิง ในธรรมชาติ เมทานอลเป็นผลิตภัณฑ์จากการสลายสารอาหารแบบไม่ใช้ออกซิเจนของแบคทีเรียหลายชนิด (ดูการผลิตเมทานอลจากของเสียเพื่อทำเป็นก๊าซชีวภาพ) ซึ่งเมทานอลจะระเหยออกสู่อากาศภายนอก แล้วสลายตัวได้คาร์บอนไดออกไซด์และน้ำ หากเราเผาเมทานอลกับอากาศ จะได้คาร์บอนไดออกไซด์กับน้ำ ดังสมการด้านล่างนี้ 2 CH3OH + 3 O2 → 2 CO2 + 4 H2O ซึ่งเปลวไฟที่ได้จากการเผาเกือบจะมองไม่เห็นเลย ดังนั้นจึงควรระมัดระวังหากมีการใช้เมทานอลเป็นเชื้อเพลิง นอกจากนี้เมทานอลยังใช้ผสมเอทานอล เพื่อมิให้สามารถรับประทานได้ (denatured alcohol) ทั้งนี้เพื่อประโยชน์ในทางภาษีอากร Methanol, also known as methyl alcohol, wood alcohol, wood naphtha or wood spirits, is a chemical with the formula CH3OH (often abbreviated MeOH). Methanol acquired the name "wood alcohol" because it was once produced chiefly as a byproduct of the destructive distillation of wood. Modern methanol is produced in a catalytic industrial process directly from carbon monoxide, carbon dioxide, and hydrogen. Methanol is the simplest alcohol, and is a light, volatile, colorless, flammable liquid with a distinctive odor very similar to, but slightly sweeter than, that of ethanol (drinking alcohol).[5] At room temperature, it is a polar liquid, and is used as an antifreeze, solvent, fuel, and as a denaturant for ethanol. It is also used for producing biodiesel via transesterification reaction. Methanol is produced naturally in the anaerobic metabolism of many varieties of bacteria, and is commonly present in small amounts in the environment. As a result, there is a small fraction of methanol vapor in the atmosphere. Over the course of several days, atmospheric methanol is oxidized with the help of sunlight to carbon dioxide and water. Methanol burns in oxygen including open air, forming carbon dioxide and water: 2 CH3OH + 3 O2 → 2 CO2 + 4 H2O Methanol ingested in large quantities is metabolized to formic acid or formate salts, which is poisonous to the central nervous system, and may cause blindness, coma, and death. Because of these toxic properties, methanol is frequently used as a denaturant additive for ethanol manufactured for industrial uses. This addition of methanol exempts industrial ethanol (commonly known as "denatured alcohol" or "methylated spirit") from liquor excise taxation in the US and some other countries. Applications Methanol, a common laboratory solvent, is especially useful for HPLC, UV/VIS spectroscopy, and LCMS due to its low UV cutoff. Feedstock The largest use of methanol by far is in making other chemicals. About 40% of methanol is converted to formaldehyde, and from there into products as diverse as plastics, plywood, paints, explosives, and permanent press textiles. Also in the early 1970s, a methanol to gasoline process was developed by Mobil for producing gasoline ready for use in vehicles. One such industrial facility was built at Motunui in New Zealand in the 1980s. In the 1990s, large amounts of methanol were used in the United States to produce the gasoline additive methyl tert-butyl ether (MTBE). While MTBE is no longer marketed in the U.S., it is still widely used in other parts of the world. In addition to direct use as a fuel, methanol (or less commonly, ethanol) is used as a component in the transesterification of triglycerides to yield a form of biodiesel. Other chemical derivatives of methanol include dimethyl ether, which has replaced chlorofluorocarbons as an aerosol spray propellant, and acetic acid. Dimethyl ether (DME) also can be blended with liquified petroleum gas (LPG) for home heating and cooking, and can be used as a diesel replacement for transportation fuel. Methanol-to-Olefins/Methanol-to-Propylene (MTO/MTP), among others processes such as: Metathesis, Propane Dehydrogenation (PDH), High Severity FCC, and Olefins Cracking, is a new and novel lower-cost chemical process for on-purpose propylene production technology of high interest to the petrochemical marketplace, to supply the tight propylene market. The market became tight because of the ethane prices falling in the USA, due to the exploration of shale gas reserves. The low price ethylene produced from this raw material has given chemical producers in North America a feedstock advantage. Such change has put naphtha-fed steam crackers at a disadvantageous position, with many of them shutting down or revamping to use ethane as feedstock. Nevertheless, the propylene output rates from ethane-fed crackers are negligible. Fuel for vehicles Main articles: Methanol fuel and methanol economy Methanol is used on a limited basis to fuel internal combustion engines. Pure methanol is required by rule to be used in Champcars, Monster Trucks, USAC sprint cars (as well as midgets, modifieds, etc.), and other dirt track series, such as World of Outlaws, and Motorcycle Speedway. Methanol is also used, as the primary fuel ingredient since the late 1940s, in the powerplants for radio control, control line and free flight airplanes (as methanol is required in the engines that primarily power them), cars and trucks, from such an engine's use of a platinum filament glow plug being able to ignite the methanol vapor through a catalytic reaction. Drag racers and mud racers, as well as heavily modified tractor pullers, also use methanol as their primary fuel source. Methanol is required with a supercharged engine in a Top Alcohol Dragster and, until the end of the 2006 season, all vehicles in the Indianapolis 500 had to run methanol. Mud racers have mixed methanol with gasoline with nitrous oxide to produce more power than mixing gasoline and nitrous oxide alone.
One of the potential drawbacks of using high concentrations of methanol (and other alcohols, such as ethanol) in fuel is the corrosivity to some metals of methanol, particularly to aluminium. Methanol, although a weak acid, attacks the oxide coating that normally protects the aluminum from corrosion: 6 CH3OH + Al2O3 → 2 Al(OCH3)3 + 3 H2O The resulting methoxide salts are soluble in methanol, resulting in a clean aluminium surface, which is readily oxidized by dissolved oxygen. Also, the methanol can act as an oxidizer: 6 CH3OH + 2 Al → 2 Al(OCH3)3 + 3 H2 This reciprocal process effectively fuels corrosion until either the metal is eaten away or the concentration of CH3OH is negligible. Concerns with methanol's corrosivity have been addressed by using methanol-compatible materials, and fuel additives that serve as corrosion inhibitors. When produced from wood or other organic materials, the resulting organic methanol (bioalcohol) has been suggested as renewable alternative to petroleum-based hydrocarbons. Low levels of methanol can be used in existing vehicles, with the use of proper cosolvents and corrosion inhibitors. Methanol fuel has been proposed for ground transportation. The chief advantage of a methanol economy is that it could be adapted to present internal combustion engines with a minimum of modification in both engines and infrastructure to store and deliver liquid fuel. Government policy The European Fuel Quality Directive allows up to 3% methanol with an equal amount of cosolvent to be blending in gasoline sold in Europe. China uses more than one billion gallons of methanol per year as a transportation fuel in both low level blends used in existing vehicles, and as high level blends in vehicles designed to accommodate the use of methanol fuels. In the USA in 2011, the Open Fuel Standard Act of 2011 was introduced in the US Congress to encourage car manufacturers to warrant their cars to burn methanol as a fuel in addition to gasoline and ethanol. The bill is being championed by the Open Fuel Standard Coalition.[citation needed] Other applications Methanol is a traditional denaturant for ethanol, the product being known as "denatured alcohol" or "methylated spirit". This was commonly used during the Prohibition to discourage consumption of bootlegged liquor, and ended up causing several deaths. Methanol is also used as a solvent, and as an antifreeze in pipelines and windshield washer fluid. In some wastewater treatment plants, a small amount of methanol is added to wastewater to provide a carbon food source for the denitrifying bacteria, which convert nitrates to nitrogen to reduce the nitrification of sensitive aquifers. During World War II, methanol was used as a fuel in several German military rocket designs, under the name M-Stoff, and in a roughly 50/50 mixture with hydrazine, known as C-Stoff.
Methanol was used as an automobile coolant antifreeze in the early 1900s. Methanol is used as a denaturing agent in polyacrylamide gel electrophoresis. Direct-methanol fuel cells are unique in their low temperature, atmospheric pressure operation, allowing them to be miniaturized to an unprecedented degree. This, combined with the relatively easy and safe storage and handling of methanol, may open the possibility of fuel cell-powered consumer electronics, such as for laptop computers and mobile phones. Methanol is also a widely used fuel in camping and boating stoves. Methanol burns well in an unpressurized burner, so alcohol stoves are often very simple, sometimes little more than a cup to hold fuel. This lack of complexity makes them a favorite of hikers who spend extended time in the wilderness. Similarly, the alcohol can also be gelled to reduce risk of leaking or spilling, as with the brand "Sterno". Methanol is mixed with water and injected into high performance diesel and gasoline engines for an increase of power and a decrease in intake air temperature in a process known as water methanol injection. Energy carrier Methanol is also useful as an energy carrier. It is easier to store than hydrogen, burns cleaner than fossil fuels, and is biodegradable
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