Electrooxidation, ethylene

Electrooxidation, ethylene, 30 254-255 Electrophiles, reactions with carbanions, 35 392-393... 

Ethylene Glycol and its Derivatives. - The electrooxidation ethylene glycol has been the subject of very extensive studies during the last 20 years. Ethylene glycol (EG) was and is considered as a prospective fuel in fuel cell systems. The overall oxidation... 

Demarconnay L, Brimaud S, Coutanceau C, Leger JM. 2007. Ethylene Glycol electrooxidation in alkaline medium at pluri-metalhc FT based catalysts. J Electroanal Chem 601 169-180. 

Electrochemical epoxidation of olefins has been developed for the production of ethylene and propylene oxides in aqueous sodium chloride or bromide solution. However, associated with these electrolyses are difficulties in achieving product selectivity as well as in obtaining high yields of the epoxides. Recently, a regiose-lective )-epoxidation of polyisoprenoids (23) to (24), promoted by electrooxidation in an MeCN/THF/H20-NaBr-(Pt) system, has been achieved (Scheme 10) [52]. 

After Little s proposal, many researchers have pursued such an exciting system in vain. Even metallic behavior was rarely seen in doped organic polymers, gels, and actuators. As mentioned in Sect. 3.4.4, MCso with linearly polymerized Ceo" exhibited one-dimensional (M = Rb, Cs) or three-dimensional (M = K) metallic behavior [144]. Recently a doped poly aniline was reported to exhibit a metallic temperature dependence for a crystalline polymer chemical oxidation of monomers grew crystallite polyaniline [329] early doping studies on polypyrrole (PFg) and poly(3,4-ethylene-dioxythiophene)X (X = PFg, BF4, and CF3SO3) prepared by electrooxidation at low temperatures also showed a metallic temperature dependence below 10-20 K (Scheme 16) [330, 331]. 

Ethylene can be oxidized to acetaldehyde in high yields similar to the Wacker-process if electrogenerated palladium(ll) is used as catalyst. In this way the copper(II) catalyzed air oxidation of palladium(O) is replaced by the electrooxidation according to Eq. (40). 

Methanol electrooxidation is not the only alternative to hydrogen being studied for alkaline fuel cells. Ethanol, ethylene glycol, and other alcohols are also currently being considered. 

Fig. 13. Rate of ethylene electrooxidation versus adsorption energy (50).

Homogeneous catalysis by redox metals is also known for nonelectro-chemical processes. Thus, ethylene is oxidized to acetaldehyde in the Wacker process in aqueous solutions containing Pd " (504). Apart from complex formation and insertion (505), ionic oxidation and reduction may take place. It is noteworthy that palladium oxidation to form ions that act as homogeneous catalysts has been suggested as an important step in ethylene electrooxidation on solid palladium electrocatalysts 28, 29). 

The selectivity of palladium and gold for alkene oxidation to aldehydes 28,29,170) was attributed initially to adsorption strength. However, electrooxidation in the presence of palladium ions indicates possible homogeneous alkene insertion, similar to the Wacker process 304). Homogeneous reaction is also involved in redox oxidations of hydrocarbons. In this case, the nature of the metal ions is expected to control selectivity. Indeed, toluene yields 20% benzaldehyde in electrolytes containing Ce salts, while oxidation proceeds to benzoic acid with Cr redox catalysts 311). In addition, the concentration of redox catalysts appears to affect yields in nonelectrochemical oxidation of ethylene large amounts of palladium chloride promote butene formation at the expense of acetaldehyde 312). Finally, the role of the electrolyte and solvent should not be ignored. For instance, electrooxidation of ethylene on carbon, in aqueous solution of acetic acid yields acetaldehyde 313) in the... 

The electrooxidation of ethylene glycol was studied on Bi modified Pt(lll) by voltanunetry and real-time IR spectroscopy. Two major oxidation products were found, with and without modification oxalic acid and CO2. It is assumed that these products were obtained via distinct reaction pathways. 

Electrochemical reactions probably occur in a larger amount of intermediate steps than the corresponding gas phase reactions. For example, electrooxidation of ethylene requires the transfer of twelve electrons. When the over-all oxidation reactions... 

F. Ficicioglu and F. Kadirgan, Electrooxidation of ethylene glycol on a platinum doped polyaniline electrode, J. Electroanal. Chem., 451, 95 99 (1998). 

A. Kelaidopoulou, E. Abelidou, A. Papoutsis, E.K. Polychromiadis, and G. Kokkinidis, Electrooxidation of ethylene glycol on Pt-based catalysts dispersed in polyaniline, J. Appl. 

Kim HJ, Choi SM, Green S, Tompsett GA, Lee SH, Huber GW, Kim WB (2011) Highly active and stable PtRuSn/C catalyst for electrooxidations of ethylene glycol and glycerol. Appl Catal B Environ 101 366-375... 

Feng Y, Yin W, Li Z, Huang C, Wang Y (2010) Ethylene glycol, 2-propanol electrooxidation in alkaline medium on the ordered intermetallic PtPb surface. Electrochim Acta 55 6991-6999... 

By the same manner, the electropolymerization of the copper complex of 80 (half-unit = 2,6-diacetylpyridine-mono(ethylene(liamine)) was performed, which led to an electroactive polymeric Him whose electrocatalytic properties towards biodegradable agrochemicals were evaluatedOne can cite the example of the electrooxidative polymerization of 81, a 3-[l-(2-amino-phenylimino)-ethyl]-6-methylpyran-2,4-dione Schiff base. The corresponding films are insoluble in most solvents, electroactive in water but electro-inactive in acetonitrile and they display electrocatalytic properties towards the oxidation of hydroquinone . ... 

Oiang SC, Ho YH, Weaver MJ (1991) Applications of real-time FTIR spectroscopy to the elucidation of complex electroorganic pathways - electrooxidation of ethylene-glycol on gold, platinum, and nickel in alkaline-solution. J Am Chem Soc 113(25) 9506-9513... 

Kadirgan F, BouhiercharbonnierE, Lamy C, Leger JM, Beden B (1990) Mechanistic study of the electrooxidation of ethylene-glycol on gold and adatom-modified gold electrodes in alkaline-medium. J Electroanal Chem 286(1-2) 41-61... 

As we did for ethanol [63], we also studied the electrooxidation of ethylene glycol using S-MWCNT-PdSnmjx and S-MWCNT-PdNimix and demonstrated that the Pd-based bimetallic nanocatalysts are more efficient catalysts than the monodispersed Pd nanocatalyst (results shown in Pig. 6.8 and summarized in Table 6.4). 

Table 6.3 Representative Pd-based nanocatalysts for ethylene glycol and glycerol electrooxidation in afkaline media...

Tanaka H, Kubota J, Miyahara S, Kuroboshi M (2005) Electrooxidation of alcohols in an Ai-oxyl-immobilized poly(ethylene-co-acrylic acid)/ water disperse system. Bull Chem Soc Jpn 78 1677-1684... 

Ho KC, Hung WT (2001) An amperometric N02 gas sensor based on Pt/Nafion electrode. Sens Actuators B 79 11-18 Ho KC, Liao JY, Yang CC (2005) A kinetic study for electrooxidation of NO gas at a Pt/membrane electrode-apphcation to amperometric NO sensor. Sens Actuators B 108 820-827 Imaya H, Ishiji T, Takahashi K (2005) Detection properties of electrochemical acidic gas sensors using halide-halate electrolytic solutions. Sens Actuators B 108 803-807 Ives DJG, Janz GJ (eds) (1961) Reference electrodes theory and practice. Academic, New York, NY Jordan LR, Hauser PC, Dawson GA (1997) Humidity and temperature effects on the response to ethylene of an amperometric sensor utilizing a gold-Nafion electrode. Electroanalysis 9 1159-1162 Katayama-Aramata A, Nakajima H, Fujikawa K, Kita H (1983) Metal electrodes bonded on sohd polymer electrolyte membranes (SPE)—the behaviour of platinum bonded on SPE for hydrogen and oxygen electrode processes. Electrochim Acta 28 777-780... 

This paper focuses on the effects of the carbon and ethylidyne-derived adlayers in electrooxidation. We present brief accounts of how the adlayers were characterized, both electrochemically and in vacuum, and will describe adlayer characterization in more detail in a separate publication [19]. To our knowledge, the effects of carbon adlayers on single crystal electrodes have not been studied, although the situation is somewhat analogous to platinum particles deposited on graphite electrodes, about which quite a bit is known [20,21]. The e ylidyne adlayer is derived from adsorption of ethylene in vacuum [22,23]. Electrochemical adsorption of ethylene and electroreduction to ethane have also been previously studied [24-28]. 

Figure 14.15. TEM images of microwave-synthesized Pt/CNTs from the ethylene glycol solutions of H2PtCl5 with different pH in the presence of CNTs (a) pH = 3.6 (h) pH = 5.8 (c) pH = 7.4 and (d) pH = 9.2 [112]. (Reprinted from Carhon, 43(10), Li X, Chen W-X, Zhao J, Xing W, Xu Z-D, Microwave polyol synthesis of Pt/CNTs catalysts Effects of pH on particle size and electrocatal5nic activity for methanol electrooxidization, 2168-74, 2005, with permission from Elsevier.)...

Neto AO, Vasconcelos TRR, Da Silva RWRV, Linardi M, Spinace EV. Electrooxidation of ethylene glycol on PtRn/C and PtSn/C electrocatalysts prepared by alcohol-reduction process. J Appl Electrochem 2005 35 193-8. 

Demarconnay. L., Brimaud. S., Coutanceau, C., et al. (2007). Ethylene Glycol Electrooxidation in Alkaline Medium at Pluri-metalhc Pt Based Catalysts, J. Electroanal. Chem., 601, pp. 169-180. 

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