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    عطر القصايد
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    جديد

    تاريخ التسجيل: Jun 2006
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    الحقوووووووووووووووووووووووووووني

    سلااااااااااااااااااااااااااااااام

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    بليزززز ساعدوووني

    من مواضيع عطر القصايد :


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  2. [2]
    نورالاسراء
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    عضو فعال جداً


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    السلام عليكم
    هذا يا عطر القصايد من احسن المواقع الذى يتكلم عن المواد الكيميائية
    وهذه صفحة الميتانول
    http://en.wikipedia.org/wiki/Methanol

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    السلام عليكم
    شكرا يا أخت نور

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  4. [4]
    حسام النجار
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    عضو


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    Not to be confused with Menthol.
    Methanol







    IUPAC namemethanolOther nameshydroxymethane
    methyl alcohol
    methyl hydrate
    wood alcohol
    carbinolIdentifiersCAS number[67-56-1]RTECS numberPC1400000SMILES
    [show]
    CO

    ChemSpider ID864PropertiesMolecular formulaCH3OHMolar mass32.04 g/molAppearancecolorless liquidDensity0.7918 g/cm³, liquidMelting point–97 °C, -142.9 °F (176 K)
    Boiling point64.7 °C, 148.4 °F (337.8 K)
    Solubility in waterFully miscibleAcidity (pKa)~ 15.5Viscosity0.59 mPa·s at 20 °CDipole moment1.69 D (gas)HazardsMSDSExternal MSDSEU classificationFlammable (F)
    Toxic (T)NFPA 704
    3
    3
    1

    R-phrasesR11, R23/24/25, R39/23/24/25S-phrases(S1/2), S7, S16, S36/37, S45Flash point11 °CRelated compoundsRelated alkanolsethanol
    butanolRelated compoundschloromethane
    methoxymethaneSupplementary data pageStructure and
    properties
    n, εr, etc.Thermodynamic
    data
    Phase behaviour
    Solid, liquid, gasSpectral dataUV, IR, NMR, MSExcept where noted otherwise, data are given for
    materials in their standard state
    (at 25 °C, 100 kPa)

    Infobox references

    Methanol, also known as methyl alcohol, carbinol, wood alcohol, wood naphtha or wood spirits, is a chemical compound with chemical formula CH3OH (often abbreviated MeOH). It is the simplest alcohol, and is a light, volatile, colourless, flammable, poisonous liquid with a distinctive odor that is somewhat milder and sweeter than ethanol. 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. As a result, there is a small fraction of methanol vapor in the atmosphere. Over the course of several days, atmospheric methanol is oxidized by oxygen with the help of sunlight to carbon dioxide and water.
    Methanol burns in air forming carbon dioxide and water:
    2 CH3OH + 3 O2 → 2 CO2 + 4 H2O A methanol flame is almost colorless, causing an additional safety hazard around open methanol flames.
    Because of its poisonous properties, methanol is frequently used as a denaturant additive for ethanol manufactured for industrial uses— this addition of a poison economically exempts industrial ethanol from the rather significant 'liquor' taxes that would otherwise be levied as it is the essence of all potable alcoholic beverages. Methanol is often called wood alcohol because it was once produced chiefly as a byproduct of the destructive distillation of wood. It is now produced synthetically by a multi-step process: natural gas or coal gas and steam are reformed in a furnace to produce hydrogen and carbon monoxide; then, hydrogen and carbon monoxide gases react under pressure in the presence of a catalyst.
    *******s

    [hide]


    [edit] History

    In their embalming process, the ancient Egyptians used a mixture of substances, including methanol, which they obtained from the pyrolysis of wood. Pure methanol, however, was first isolated in 1661 by Robert Boyle, who called it spirit of box, because he produced it via the distillation of boxwood. It later became known as pyroxylic spirit. In 1834, the French chemists Jean-Baptiste Dumas and Eugene Peligot determined its elemental composition. They also introduced the word methylene to organic chemistry, forming it from Greek methy = "wine" + hȳlē = wood (patch of trees). Its intended origin was "alcohol made from wood (substance)," but it has Greek language errors. The term "methyl" was derived in about 1840 by back-formation from methylene, and was then applied to describe "methyl alcohol." This was shortened to "methanol" in 1892 by the International Conference on Chemical Nomenclature. The suffix -yl used in organic chemistry to form names of carbon groups, was extracted from the word "methyl."
    In 1923, the German chemists Matthias and Pier, working for BASF developed a means to convert synthesis gas (a mixture of carbon monoxide, carbon dioxide, and hydrogen) into methanol. A patent was filed Jan 12 1926 (reference no. 1,569,775). This process used a chromium and manganese oxide catalyst, and required extremely vigorous conditions—pressures ranging from 50 to 220 atm), and temperatures up to 450 °C. Modern methanol production has been made more efficient through use of catalysts (commonly copper) capable of operating at lower pressures.
    The use of methanol as a motor fuel received attention during the oil crises of the 1970s due to its availability and low cost. Problems occurred early in the development of gasoline-methanol blends. As a result of its low price, some gasoline marketers over-blended. Others used improper blending and handling techniques.
    In 2006 astronomers using the MERLIN array of radio telescopes at Jodrell Bank Observatory discovered a large cloud of methanol in space, 300 billion miles across.

    [edit] Production

    Today, synthesis gas is most commonly produced from the methane component in natural gas rather than from coal. Three processes are commercially practiced. At moderate pressures of 1 to 2 MPa (10–20 atm) and high temperatures (around 850 °C), methane reacts with steam on a nickel catalyst to produce syngas according to the chemical equation:
    CH4 + H2OCO + 3 H2 This reaction, commonly called steam-methane reforming or SMR, is endothermic and the heat transfer limitations place limits on the size of and pressure in the catalytic reactors used. Methane can also undergo partial oxidation with molecular oxygen to produce syngas, as the following equation shows:
    2 CH4 + O2 → 2 CO + 4 H2 this reaction is exothermic and the heat given off can be used in-situ to drive the steam-methane reforming reaction. When the two processes are combined, it is referred to as autothermal reforming. The ratio of CO and H2 can be adjusted to some extent by the water-gas shift reaction,
    CO + H2OCO2 + H2, to provide the appropriate stoichiometry for methanol synthesis.
    The carbon monoxide and hydrogen then react on a second catalyst to produce methanol. Today, the most widely used catalyst is a mixture of copper, zinc oxide, and alumina first used by ICI in 1966. At 5–10 MPa (50–100 atm) and 250 °C, it can catalyze the production of methanol from carbon monoxide and hydrogen with high selectivity
    CO + 2 H2 → CH3OH It is worth noting that the production of synthesis gas from methane produces 3 moles of hydrogen for every mole of carbon monoxide, while the methanol synthesis consumes only 2 moles of hydrogen for every mole of carbon monoxide. One way of dealing with the excess hydrogen is to inject carbon dioxide into the methanol synthesis reactor, where it, too, reacts to form methanol according to the chemical equation
    CO2 + 3 H2 → CH3OH + H2O Although natural gas is the most economical and widely used feedstock for methanol production, other feedstocks can be used. Where natural gas is unavailable, light petroleum products can be used in its place.

    [edit] Applications

    Methanol is a common laboratory solvent. It is especially useful for HPLC and UV/VIS spectroscopy due to its low UV cutoff.

    [edit] 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.[citation needed] In the 1990s, large amounts of methanol were used in the United States to produce the gasoline additive methyl tert-butyl ether (MTBE), though leakage has led to many states banning it. 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.

    [edit] Automotive fuel

    Main article: Methanol fuel
    Methanol is used on a limited basis to fuel internal combustion engines, mainly by virtue of the fact that it is not nearly as flammable as gasoline. Pure methanol is required by rule to be used in Champcars, USAC sprint cars (as well as midgets, modifieds, etc.), and other dirt track series such as World of Outlaws. Methanol is also used in radio control, control line and free flight airplanes (required in the "glow-plug" engines that primarily power them), cars and trucks. Drag racers and mud racers 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 and nitrous oxide to produce more power than gasoline and nitrous oxide alone.
    One of the drawbacks of methanol as a fuel is its corrosivity to some metals, including aluminum. Methanol, although a weak acid, attacks the oxide coating that normally protects the aluminium from corrosion:
    6 CH3OH + Al2O3 → 2 Al(OCH3)3 + 3 H2O The resulting methoxide salts are soluble in methanol, resulting in clean aluminum surface, which is readily oxidized by some 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.
    When produced from wood or other organic materials, the resulting organic methanol (bioalcohol) has been suggested as renewable alternative to petroleum-based hydrocarbons. However, one cannot use pure methanol in modern petroleum cars without modification, due to potential damage to metal piping and rubber seals.

    [edit] Other applications

    Methanol is a traditional denaturant for ethanol, thus giving the term methylated spirit.
    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 food source of carbon for the denitrifying bacteria, which convert nitrates to nitrogen.
    During World War II, methanol was used as a fuel in several German military rocket designs, under name M-Stoff, and in a mixture as C-Stoff.
    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.[1]
    Methanol is also a widely used fuel in camping and boating stoves. The Swedish made Trangia stoves are among the best known alcohol burning 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. In Roland Mueser's book Long-Distance Hiking: Lessons from the Appalachian Trail, Mueser did a survey of stoves used by thru-hikers and found that alcohol was the only stove type with a zero percent failure rate.

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