Methanol current applications

Today, synthesis gas is mainly used for the production of ammonia (120 x 10 t/yr ) and methanol (30 X 10 t/yr ) followed by pure hydrogen for hydro-treating in refineries. Other current applications are in the production of higher alcohols by hydroformulation and a number of products including acetic acid, formaldehyde, dimethyl ether (DME), and methyl-tert-butyl ether (MTBE) in all cases methanol is used as a coreactant. 

The use of methanol offers the best results in the trans-esterification of oils and fats. Compared with other alcohols, methanol requires shorter reaction times and smaller catalyst amounts and alcohol/oil molar ratios [10,12,15,16,51,52]. These advantages lead to reduced consumption of steam, heat, water, and electricity, and use of smaller processing equipment to produce the same amount of biodiesel. Biodiesel applications continue to expand. Thus, in addition to its use as fuel, biodiesel has been employed in the synthesis of resins, polymers, emulsifiers, and lubricants [53-64]. Concerning the range of applications, new biodiesel production processes should be considered as alternatives to the production based on methanol. Currently, methanol is primarily produced from fossil matter. Due to its high toxicity, methanol may cause cancer and blindness in humans, if they are overexposed to it. Methanol traces are not desired in food and other products for human consumption [15]. In contrast, ethanol emerges as an excellent alternative to methanol as it is mainly produced from biomass, is easily metabolized by humans, and generates stable fatty acid esters. Additionally, fatty acid ester production with ethanol requires shorter reaction times and smaller amounts of alcohol and catalyst compared to the other alcohols, except methanol, used in transesterification processes [11,15,16]. 

By far the preponderance of the 3400 kt of current worldwide phenolic resin production is in the form of phenol-formaldehyde (PF) reaction products. Phenol and formaldehyde are currently two of the most available monomers on earth. About 6000 kt of phenol and 10,000 kt of formaldehyde (100% basis) were produced in 1998 [55,56]. The organic raw materials for synthesis of phenol and formaldehyde are cumene (derived from benzene and propylene) and methanol, respectively. These materials are, in turn, obtained from petroleum and natural gas at relatively low cost ([57], pp. 10-26 [58], pp. 1-30). Cost is one of the most important advantages of phenolics in most applications. It is critical to the acceptance of phenolics for wood panel manufacture. With the exception of urea-formaldehyde resins, PF resins are the lowest cost thermosetting resins available. In addition to its synthesis from low cost monomers, phenolic resin costs are often further reduced by extension with fillers such as clays, chalk, rags, wood flours, nutshell flours, grain flours, starches, lignins, tannins, and various other low eost materials. Often these fillers and extenders improve the performance of the phenolic for a particular use while reducing cost. 

In contrast with the AFC, the PAFC can demonstrate reliable operation with 40 percent to 50 percent system efficiency even when operating on low quality fuels, such as waste residues. This fuel flexibility is enabled by higher temperature operation (200°C vs. 100°C for the AFC) since this raises electro-catalyst tolerance toward impurities. Flowever, the PAFC is still too heavy and lacks the rapid start-up that is nec-essaiy for vehicle applications because it needs preheating to 100°C before it can draw a current. This is unfortunate because the PAFC s operating temperature would allow it to thermally integrate better with a methanol reformer. 

Such bimetallic alloys display higher tolerance to the presence of methanol, as shown in Fig. 11.12, where Pt-Cr/C is compared with Pt/C. However, an increase in alcohol concentration leads to a decrease in the tolerance of the catalyst [Koffi et al., 2005 Coutanceau et ah, 2006]. Low power densities are currently obtained in DMFCs working at low temperature [Hogarth and Ralph, 2002] because it is difficult to activate the oxidation reaction of the alcohol and the reduction reaction of molecular oxygen at room temperature. To counterbalance the loss of performance of the cell due to low reaction rates, the membrane thickness can be reduced in order to increase its conductance [Shen et al., 2004]. As a result, methanol crossover is strongly increased. This could be detrimental to the fuel cell s electrical performance, as methanol acts as a poison for conventional Pt-based catalysts present in fuel cell cathodes, especially in the case of mini or micro fuel cell applications, where high methanol concentrations are required (5-10 M). 

Fig. 2.8. (a)On-line mass spectroscopic detection of HD (m/e = 3) produced by application of a potential step to 0.97 V vs. PdH to a Pt electrode in 10 2 M CD3OH/10 4 M/HClO4/0.1 M NaC104/H20 during 0.5 s, followed by a potential step to —0.44 V vs. Pd-H. For comparison HD signal without methanol oxidation when switching the potential from open circuit to H2 evolution at — 0.44 V (b). Upper part recording of current. 

Only a very small proportion of the fatty acids are present in the free, unester-ified form and the vast majority are components of other lipids. Nevertheless it is important to be able to measure and identify the free fatty acids present in either form and for this they must be first extracted into an organic solvent and then usually converted to their methyl ester. The simplest method of methyla-tion, which is applicable to both esterified and non-esterified fatty acids, is to heat the lipid sample for 2 h under a current of nitrogen at 80-90°C with 4% sulphuric acid in methanol. After cooling and the addition of water, the resulting methyl esters are extracted several times into hexane and the combined extracts are dried over sodium carbonate and anhydrous sodium sulphate. The solvent fraction is then reduced in volume by a stream of nitrogen. 

Analytical and preparative high-speed counter-current chromatography (HSCCC) has also found application for the separation of lycopene from crude extract of tomato paste. An aliquot of 2g of crude extract of tomato paste was percolated five times with 50 ml of chloroform-methanol (2 1) at ambient temperature. The combined organic phase was evaporated to dryness under a nitrogen stream. The nonaqueous two-phase system... 

Apart from hydrocarbons and gasoline, other possible fuels include hydrazine, ammonia, and methanol, to mention just a few. Fuel cells powered by direct conversion of liquid methanol have promise as a possible alternative to batteries for portable electronic devices (cf. below). These considerations already indicate that fuel cells are not stand-alone devices, but need many supporting accessories, which consume current produced by the cell and thus lower the overall electrical efficiencies. The schematic of the major components of a so-called fuel cell system is shown in Figure 22. Fuel cell systems require sophisticated control systems to provide accurate metering of the fuel and air and to exhaust the reaction products. Important operational factors include stoichiometry of the reactants, pressure balance across the separator membrane, and freedom from impurities that shorten life (i.e., poison the catalysts). Depending on the application, a power-conditioning unit may be added to convert the direct current from the fuel cell into alternating current. 

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