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| A '''methanol reformer''' is a device used in [[chemical engineering]], especially in the area of [[fuel cell]] technology, which can produce pure [[hydrogen]] gas and [[carbon dioxide]] by reacting a [[methanol]] and [[water]] (steam) mixture.
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| :<math>\mathrm{ CH_3OH_{(g)} + H_2O_{(g)} \;\longrightarrow\; CO_2 + 3\ H_2 \qquad} \Delta H_{R\ 298}^0 = 49.2\ \mathrm{kJ/mol} </math>
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| <small>Methanol is transformed into hydrogen and carbon dioxide by pressure and heat and interaction with a [[catalysis|catalyst]].</small>
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| == Technology ==
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| A mixture of water and methanol with a molar [[concentration]] ratio (water:methanol) of 1.0 - 1.5 is pressurized to approximately 20 [[bar (unit)|bar]], vaporized and heated to a temperature of 250 - 360 [[Celsius|°C]]. The hydrogen that is created is separated through the use of [[Pressure swing adsorption]] or a [[hydrogen-permeable membrane]] made of [[polymer]] or a [[palladium]] alloy.
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| There are two basic methods of conducting this process.
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| * The water-methanol mixture is introduced into a tube-shaped reactor where it makes contact with the catalyst. Hydrogen is then separated from the other [[reagent|reactants]] and products in a later chamber, either by pressure swing adsorption (PSA), or through use of a membrane where the majority of the hydrogen passes through. This method is typically used for larger, non-mobile units.
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| * The other process features an integrated reaction chamber and separation membrane, a [[membrane reactor]]. In this, relatively new approach, the reaction chamber is made to contain high-temperature, hydrogen-permeable membranes that can be formed of [[refractory metals]], palladium alloys, or a PdAg-coated [[ceramic]]. The hydrogen is thereby separated out of the reaction chamber as the reaction proceeds, This purifies the hydrogen and, as the reaction continues, increases both the reaction rate and the amount of hyrogen extracted.
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| With either design, not all of the hydrogen is removed from the product gases (raffinate). Since the remaining gas mixture still contains a significant amount of chemical energy, it is often mixed with air and burned to provide heat for the endothermic reforming reaction.
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| == Advantages and disadvantages ==
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| Methanol reformers are being considered as a component of a hydrogen fuel cell-powered vehicle. A prototype car, the [[Mercedes-Benz NECAR|NECAR 5]], was introduced by [[Daimler-Chrysler]] in the year 2000. The primary advantage of a vehicle with a reformer is that it does not need a pressurized gas tank to store hydrogen fuel; instead methanol is stored as a liquid. The logistic implications of this are great; pressurized hydrogen is difficult to store and produce. Also, this could help ease the public's concern over the danger of hydrogen and thereby make fuel cell powered vehicles more attractive. However, methanol, like [[gasoline]], is toxic and (of course) flammable. The cost of the PdAg membrane and its susceptibility to damage by temperature changes provide obstacles to adoption.
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| While hydrogen power produces energy without CO<sub>2</sub>, a methanol reformer creates the gas as a byproduct. <!---The high level of greenhouse gases in our atmosphere significantly contributes to [[global warming]].--->
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| Methanol (prepared from natural gas) that is used in an efficient fuel cell, however, releases less CO<sub>2</sub> in the atmosphere than gasoline, in a net analysis.<ref>George A. Olah (2005). "Beyond Oil and Gas: The Methanol Economy". Angewandte Chemie International Edition 44 (18): 2636–2639. {{doi|10.1002/anie.200462121}}</ref>
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| == References ==
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| <references/>
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| * Emonts, B. et al.: ''Compact methanol reformer test for fuel-cell powered light-duty vehicles'', J. Power Sources 71 (1998) 288-293
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| * Wiese, W. et al.: ''Methanol steam reforming in a fuel cell drive system'', J. Power Sources 84 (1999) 187-193
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| * Peters, R. et al.: ''Investigation of a methanol concept considering the particular impact of dynamics and long-term stability for use in a fuel-cell-powered passenger car'', J. Power Sources 86 (1999) 507-514
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| == See also ==
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| *[[Steam reforming]]
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| *[[Partial oxidation]]
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| *[[PROX]]
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| [[Category:Hydrogen production]]
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| [[Category:Fuel cells]]
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| [[Category:Chemical engineering]]
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| [[Category:Membrane technology]]
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