Reduction of methanol

Thus the reduction of methanol is not believed to proceed via a mechanism similar to that for carbon dioxide or carbon monoxide. Copper electrodes also reduce carbon monoxide to methane. 

Methanol Reduction at Ruthenium. The reduction of methanol to methane does occur as shown by the data in Table III. The data for each electrode are presented in the order that they were collected. Rates can be higher for methanol reduction compared to carbon dioxide reduction though faradaic efficiencies are lower. Unlike carbon dioxide reduction, the rate of methane formation is extremely... 

The separation of polar analytes can also be optimized by applying ternary eluent mixtures. In this case, the retention is adjusted with binary mixtures with methanol-water for k in the desired range (2polar analytes resolution [57]. 

Methanopterin (or a variant) is found in all methanogens, except possibly at very low levels in Methanosphaera stadtmanii[A6, %, 9]. This latter organism produces methane solely by the reduction of methanol to methane, with no methanol oxidation, and thus needs no methanopterin in the methanogenic pathway (however, it may need a low level for biosynthetic needs, e.g. in synthesis of serine or glycine [120]). 

Those methanogcns which possess a hydrogenase can in addition form methane by the reduction of methanol with molecular hydrogen ... 

The reduction of methanol with H2 to methane represents the simplest form of methane fermentation, and turned out to be extremely useful for studying the mechanism of ATP synthesis in cell suspensions [41] (see below). Growth at the expense of CH3OH reduction with H2 has been demonstrated so far only with Methanosphaera stadtmanae [42] and... 

K. Richau, R. Mohr, S.P. Nunes, Reduction of methanol permeability in polyetherketone-heteropolyacid membranes. Journal of Membrane Science 217 (2003) 5-15. 

Paradoxically, the efforts to reduce the methanol permeabilities of Nalion with inorganic or organic fillers in most cases yield composite membranes with permeabilities similar to that obtained by optimizing the cast procedure of pure Nafion [302]. Nevertheless, the reduction of methanol permeability by itself is not a criterion for improving DMFC performance because it is usually associated to a reduction of the proton conductivity. We will analyze this property in Sect. 6.5.5 as a previous step to discuss the behavior of the proton-conducting membranes in terms of alcohol selectivity defined by Eq. 6.2. 

Liang ZX, Shi JY, Liao SJ, Zeng JH (2010) Noble metal nanowiies incorporated Nafion membranes for reduction of methanol crossover in direct methanol fuel cells. Int J Hydrogen Energ 35 9182-9185... 

Ponce ML, Prado L, Ruffmann B, Richau K, Mohr R, Nunes SP (2003) Reduction of methanol permeability in polyetherketone - heteropolyacid membranes. J Membr Sci... 

Further reduction of methanol (methyl alcohol, CH3OH) then produces methane (CH4) while further oxidation of methanoic acid (formic acid, HCO2H) generates carbon dioxide (CO2) (Figure 9.1). 

Firstly, there is a preponderance of reactions in aqueous solutions (in sharp contrast to the journal literature) and several oxidations in methanol, while aprotic solvents only appear in a few reactions as mixtures with water. The major reason for this is associated with the stability of the electrolysis medium especially with respect to the counter-electrode reaction. The cxidation/reduc-tion of water leads only to Oj-f and Hj + OH" and the reduction of methanol to Hj and CHjO", Hence, these reactions may conveniently be used to maintain the pH of the electrolyte at a constant level while leading to no contamination of the system. In contrast, the oxidation/reduction of aprotic... 

Many other inorganic materials such as Caj (PO ), BPO, ZrPO, etc., when blended with Nafion membranes will show improvement on the membranes properties such as thermal stability, proton conductivity, and lower methanol permeation. Nafion doped with cesium cations also show evidence of good performance in the operation of DMFCs. The presence of cesium ions in the membrane, specifically in the water-rich domains, causes a ranarkable reduction of methanol permeation [43]. However, the proton conductivity could be depressed to a lesser extent by the presence of the cesium ions in the membrane. Nevertheless, at ambient conditions, the combined parameter of both proton conductivity and methanol permeabiUty shows better performance of Cs -doped membranes than the Nafion 117 membranes in the operation of DMFC. Table 15.1, shows permeability values for Nafion 117 membrane and four different Nafion 117 modified membranes. A reduction in the permeability values when the Nafion 117 membrane is modified with appropriate methanol inhibiting material can be seen. A very sharp reduction is particularly noticed in the case of Cs -doped manbrane. This indicates that exchange of by Cs cations is very effective in reducing methanol content in the hydrophilic domains of Nafion. 

Table 2 Reduction of methanol crossover in S-PEK by the addition of inorganic additives (data from [42])...

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