Butane, anodic oxidation

Aliphatic azo compounds may be obtained on anodic oxidation of A,A -dialkylhy-drazines amines or their derivatives may be oxidized to azo compounds in some cases. Anodic oxidation at a graphite electrode of rerf-butylamine containing some aqueous sodium perchlorate thus yields 2,2 -azoisobutane together with some azoxy-te Y-butane and minor amounts of nitro-fe/t-butane [83]. 

Binder and others [230] found that Raney platinum was the best single catalyst for electrochemical oxidation of hydrocarbons. Data obtained by Bianchi [231], Grubb [232], and Cairns and Mclnemey [203], who compared the catalytic activities of various platinum blacks in the anodic oxidation of propane, are consistent with this conclusion. As found by Petrii and Marvet [100], the oxidation rate of methane decreases sharply on changing from platinum to other platinum catalysts. Bockris and Dahms [192] showed that the oxidation rate of ethylene decreases in the series Pt > Rh > Ir and Pd > Au, where platinum is considerably more active than palladium. It was found in [233] that the oxidation rate of propane in alkali decreases in the order Pd > Pt > Ag, and those of ethane ethylene, propylene, and n-butane decrease in the order Pt > Pd... 

The photo-Kolbe reaction is the decarboxylation of carboxylic acids at tow voltage under irradiation at semiconductor anodes (TiO ), that are partially doped with metals, e.g. platinum [343, 344]. On semiconductor powders the dominant product is a hydrocarbon by substitution of the carboxylate group for hydrogen (Eq. 41), whereas on an n-TiOj single crystal in the oxidation of acetic acid the formation of ethane besides methane could be observed [345, 346]. Dependent on the kind of semiconductor, the adsorbed metal, and the pH of the solution the extent of alkyl coupling versus reduction to the hydrocarbon can be controlled to some extent [346]. The intermediacy of alkyl radicals has been demonstrated by ESR-spectroscopy [347], that of the alkyl anion by deuterium incorporation [344]. With vicinal diacids the mono- or bisdecarboxylation can be controlled by the light flux [348]. Adipic acid yielded butane [349] with levulinic acid the products of decarboxylation, methyl ethyl-... 

Figure 9. Temperature programmed oxidation (TPO) data showing CO2 evolution m/e = 44) of thermally deposited carbon from a Cu-Ce02-YSZ SOFC anode material after exposure to n-butane for 30 min (solid line) and a graphite powder sample (dashed line). (Reprinted with permission from ref 172. Copyright 2003 The Electrochemical Society, Inc.)...

Cuadrado and coworkers have synthesized and characterized poly(propylenimine) dendrimers modified with neutral ferrocenyl (Fc) groups (diammino butane-dend-(NHCOFc) , n = 4, 8, 16, 32, and 64, for GO, 1, 2, 3, and 4, respectively, Fig. 4b) [76], These dendrimers also showed a ferrocene-based single redox wave at the same potential E " = +0.59, +0.57, +0.59, +0.58, and +0.59 V versus SCE for GO, 1, 2, 3, and 4, respectively) in TBAH/CH2CI2 solution, pointing to the absence of electronic interactions. In addition, the anodic peak appeared to be diffusional, whereas the cathodic peak appeared to be stripping in shape. These results suggested the deposition of dendrimers during oxidation and their abrupt redissolution upon reduction. 

In the above results, stable coke-free SOFC operation was enabled by balancing the hydrocarbon fuel with H2O, CO2, or O2 in order to achieve a composition where sohd carbon is not stable (Fig. 1). It has also been demonstrated that SOFCs can be operated with reasonable stability in a range of pure hydrocarbons. With Ni-based anodes, it is well known that carbon fibers form that can damage the anode [24, 62, 63]. Furthermore, the presence of steam may not prevent this process, even in amotmts beyond those normally expected to prevent coking [24]. Thus, direct operation with higher hydrocarbons requires replacement of Ni with other electronically conducting oxides or a metal such as Cu. Indeed, when operated with higher hydrocarbons such as -butane, polyaromatic compounds (tars) formed... 

Some researchers have successfiiUy demonstrated partial oxidation in SOFC operating on natural gas and butane. Running an SOFC on air and oxygen can be economical and easy to assemble, but overall efficiency of the cell is reduced as some of the energy is utilised in oxidising hydrocarbon. If the anode selectively carries out partial oxidation of hydrocarbon to produce CO and H2 which is an exothermic reaction, the output from SOFC will increase. Equation (9.6) shows partial oxidation of hydrocarbon. 

---