Methanol and Other Liquid Fuels

An ideal fuel for any fuel cell would be a liquid fuel already in regular use, such as petrol. Unfortunately such fuels simply do not react at a sufficient rate to warrant consideration - with the exception of methanol. The nse of methanol can either be direct , where it is used as a reactant at the anode, or indirect , where it is reformed into hydrogen first in a separate unit. Both these nses show great promise. The former is considered in depth in Chapter 6. The nse of methanol as a hydrogen carrier, releasing the hydrogen in a reformer unit, is considered in some detail in the fueling fuel cells chapter. Chapter 8. 

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Commercial catalyst are available for the production of methanol and other liquid fuels from synthetic gases. The main problem is the catalyst deactivation due to chemical poisoning from chlorine and sulphur. 

From these shortcomings, the tasks for the designation of improved fuel cell membranes, compared with the state of the art, can be defined. The property profile of improved ionomer fuel cell membranes includes high -conductivity, low water/ methanol uptake, low methanol (and other liquid fuel) permeability, and fuel cell-applicability also at T > 100°C, because the higher the fuel cell operation temperature, the higher the fuel utilization, and applicability also in other (electro)membrane processes. Last but not least, the membranes should have a low price. 

Low methanol (and other liquid fuel) permeability Fuel cell-applicability also at T > 100°C... 

Syngas produced from gasification of coal, biomass, petroleum coke, and other types of feedstock can be used to generate electricity or to produce hydrogen and other liquid fuels or chemicals (ammonia, methanol, dimethyl ether, and diesel fuel) by... 

The third way of coal pipelining intensification supposes using the carrier liquid different than water. Oil products (crude oil, residual fuel oil, kerosene, fuel or Diesel oil and various mineral oils) or hydrocarbons (methanol, ethanol, carbonic acid, and other liquid organic compositions) can be used as a carrier liquid. 

Interest in methanol as an alternative fuel revived in the late 1990s—for fuel cells. It wasn t the first time this type of alcohol attracted the attention of the clean-energy community. A number of strategists had argued decades earlier that hydrogen, normally a gas, might not be the preferred eco-fuel for automotive use after all and that perhaps some other liquid fuel might be preferable. 

DMFCs have potential near-term applications mainly in the portable power source market, as they are smaller, lighter, simpler, and cleaner than conventional batteries. Liquid methanol is consumed directly in a DMFC, which implies a higher energy density of the fuel cell system. But the power densities achievable with state-of-the-art DMFCs are still very small in comparison to hydrogen-fuelled PEMFCs. One of the major problems lies in the use of liquid methanol solution on the anode of the DMFC, which, on the one hand, keeps the ionomeric membrane water saturated (and thus no humidification is needed) but, on the other hand, does not keep fuel (methanol or any other organic fuel, e.g., formic acid, ethanol) and water from permeating to the cathode side, since the basic PFSA membranes are permeable to both methanol and water. - The fuel and water crossover from anode to cathode hampers the performance of the air cathode. 

In addition to COM and CWM, CLM technology has been extended to include mixtures of coal-methanol, solvent-refined coal-oil, petroleum-coke oil, and other solid-fuel-liquid mixtures. However, for the purposes of this text, the contents of this section are limited to the more mature technologies involving COM and to CWM (Morrison, 1980 Argonne, 1990c). 

However, DMFCs do suffer some drawbacks such as lower electrical efficiency and higher catalyst loadings as compared to H2 fuel cells. Efforts should be continued on developing anode catalysts with improved methanol oxidation kinetics, cathode catalysts with a high tolerance to methanol, membranes with lower methanol permeation rates, and strategies to reduce the methanol crossover rate. Attention should also be given to other direct-feed fuel cells using other liquid fuels (such as formic acid). 

This half-cell was used for evaluating methanol oxidation catalysts and catalyst layers [24], as described in the following section. It is expected that this cell could also be suitable to mimic fuel cell operating conditions for other liquid fuel oxidation because the WE structure is similar to the structure of the anode in a direct liquid fuel ceU. 

Since methanol exists as a liquid in the temperature range of -97°C to 64°C at atmospheric pressure, it can be stored, transported, and may be used in liquid form similar to other liquid fuels like gasoline and diesel, and this makes DMFC compact and suitable for portable applications such as a battery substitute in laptop computers. A major disadvantage of DMFC is its low efficiency compared to other types of fuel cells. Additional challenges for the design of DMFC include the corrosiveness and poisonous nature of methanol fuel. 

This dissolved fuel t5q>e of cell can be used with other liquid fuels such as methanol (Muller et al., 2000 Sinor J. E. Consultants, 1997). An advantage of a liquid fuel like methanol is its high theoretical capacity per volume and weight. 

Minor species, such as CO, result from subsequent dissociation reactions governed by thermodynamics. Of the various fuels involved, methanol is the simplest liquid-based fuel to reform due to the lack of carbon-carbon bond and low reformation temperature of only around 200°C [21]. This temperature can easily be coupled to low-temperature systems. The PAFC is almost perfectly thermally matched to the methanol reformation temperature, so that waste heat from the fuel cell can be used to drive the process. For PEFCs, some additional input heat is needed for methanol and other fuel reformation. For high-temperature fuel cells, methanol (and other fuel) reformation can be accomplished internally or externally, as discussed in Chapter 7. The reformation temperature of other fuels can be several hundreds of degrees higher than that of methanol, depending on the complexity and strength of the chemical bonds as well as the catalyst used to promote the reaction. 

In the United States, in particular, recent legislation has mandated sweeping improvements to urban air quality by limiting mobile source emissions and by promoting cleaner fuels. The new laws require commercial and government fleets to purchase a substantial number of vehicles powered by an alternative fuel, such as natural gas, propane, electricity, methanol or ethanol. However, natural gas is usually preferred because of its lower cost and lower emissions compared with the other available alternative gas or liquid fuels. Even when compared with electricity, it has been shown that the full fuel cycle emissions, including those from production, conversion, and transportation of the fuel, are lower for an NGV [2]. Natural gas vehicles offer other advantages as well. Where natural gas is abundantly available as a domestic resource, increased use... 

Methanol, CH OH, is a clean-burning liquid fuel being considered as a replacement for gasoline. Calculate the theoretical yield in kilograms of C02 produced by the combustion of 1.00 L of methanol (of density 0.791 g-cm ) and compare it with the 2.16 kg of CO, generated by the combustion of 1.00 L. of octane. Which fuel contributes more C02 per liter to the atmosphere when burned What other factors would you take into consideration when deciding which of the two fuels to use See Box 14.2. 

After petroleum resource are depleted, methanol is the logical liquid fuel for the above-mentioned and other applications, because it can be... 

Methanol is a clean-burning liquid that can be used to power electricity-generating turbines as well as a fuel for automobiles and other vehicles. It can also be a valuable feedstock for a variety of chemicals (e.g., in the manufacture of acetic... 

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