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Electrochemical conversion

The electrochemical conversions of conjugated dienes iato alkadienedioic acid have been known for some time. Butadiene has been converted iato diethyl-3,7-decadiene-l,10,dioate by electrolysis ia a methanol—water solvent (67). An improvement described ia the patent Hterature (68) uses an anhydrous aprotic solvent and an electrolyte along with essentially equimolar amounts of carbon dioxide and butadiene a mixture of decadienedioic acids is formed. This material can be hydrogenated to give sebacic acid. [Pg.63]

The metallic or semi-metallic character of many common sulfides implies the significance of electrochemical factors in the study of their oxidation, which is relevant to environmental, energy, and metallurgical issues, e.g., in connection with the direct electrochemical conversion of sulfide ores to metals, the pressure leaching of ore materials, or flotation processes. [Pg.261]

In the phosphoric acid fuel cell as currently practiced, a premium (hydrogen rich) hydrocarbon (e.g. methane) fuel is steam reformed to produce a hydrogen feedstock to the cell stack for direct (electrochemical) conversion to electrical energy. At the fuel electrode, hydrogen ionization is accomplished by use of a catalytic material (e.g. Pt, Pd, or Ru) to form solvated protons. [Pg.575]

The quantitativeness of the electrochemical conversion is governed by Faraday s laws ... [Pg.25]

Further, it can be seen from Fig. 1.1 that under all conditions prevailing Cu is the positive and Zn the negative pole however, in case (b) Cu is the cathode (reduction) and Zn the anode (oxidation). Considering the flow direction within the electrolyte, one usually finds that the anode is upstream and the cathode downstream. It is also clear that by the electrochemical conversions the original galvanic cell is depleted in case (b), but can be restored by the external electrical energy source in case (c). [Pg.26]

Complex (21), a Con-cyclam analogue, is very active for the reduction of N02 and NH2OH intermediates and catalyzes the complex electrochemical conversion of N03 to NH3 325 Gold electrodes modified with cobalt-cyclam incorporated in Nafion films,324 or by electropolymerization of the pyrrole-substituted cobalt cyclam (22)326 have shown catalytic activity for the reduction of nitrate in strongly basic media. [Pg.491]

Several researchers have considered photosynthesis in nature as a model for electrochemical conversion of sunlight to chemical energy [8]. Photosynthesis is discussed in several textbooks [37-40]. The topic of photosynthesis and photoelectrochemistry is discussed in Section 7.5. [Pg.240]

The electrolysis in aqueous sulfuric acid with methanol as a cosolvent was perfomed in a filterpress membrane cell stack developed at Reilly and Tar Chemicals. Because of the low current density of the process, a cathode based on a bed of lead shot was used. A planar PbOa anode was used. The organic yield was 93% with approximately 1% of a dimer. The costs of the electrochemical conversion were estimated as one-half of the catalytic hydrogenation on a similar scale. [Pg.153]

Fuel cells and electrolyzers are counterparts for the electrochemical conversion and generation, respectively, of hydrogen and oxygen ... [Pg.314]

Laviron has studied an especially interesting class of nitro compounds containing a second basic site, e.g. 4-nitropyridine (14)33. Even two-dimensional representations such as those encountered earlier (Schemes 2-4) are inadequate to represent this mechanistically very complex situation. Laviron showed, however, that the electrochemical conversion of 14 to the corresponding ArN(OH)2 species can be satisfactorily explained in terms of a modified so-called bi-cubic diagram (Figure 1). Note that the each of the front and rear planes of the bi-cubic model consists of a seven-component reaction diagram analogous to that of... [Pg.845]

If the target is to find new electrochemical conversions - perhaps of expensive compounds - then the products only have to be accessible in small amounts for their identification. A high yield concerning the reactants is required but technical aspects such as energy consumption are not interesting. In this case, a small volume will probably be the most important feature of the electrochemical cell. [Pg.30]

The significant, often decisive, influence of the solvent in chemical reactions similarly is valid for electrochemical reactions too, for example, due to protic or aprotic and electrophilic or nucleophilic properties. If an excess of reactants can be used as solvent, a particularly uncomplicated operation will be possible. An additional solvent should be inert. The requirements for the solvent in dissolving power for reactants and products and the criteria regarding an easy separation of the products from the reaction mixture, for example, the boiling point, are comparable for chemical and electrochemical conversions. Generally, there is an interest to use, as far as possible, inexpensive, nontoxic, and easy to handle solvents. [Pg.47]

For the dehydrogenation of CH—XH structures, for example, of alcohols to ketones, of aldehydes to carboxylic acids, or of amines to nitriles, there is a wealth of anodic reactions available, such as the nickel hydroxide electrode [126], indirect electrolysis [127, 128] (Chapter 15) with I , NO, thioanisole [129, 130], or RUO2/CP [131]. Likewise, selective chemical oxidations (Cr(VI), Mn02, MnOJ, DMSO/AC2O, Ag20/Celite , and 02/Pt) [94] are available for that purpose. The advantages of the electrochemical conversion are a lower price, an easier scale-up, and reduced problems of pollution. [Pg.83]

The radicals undergo the usual reactions as dimerizations, disproportionations, atom-transfer reactions, or additions [3]. Compared to homogeneous radical reactions, bimolecular dimerizations and disproportionations are favored at the electrode. Stationary radical concentrations are higher in heterogeneous electrochemical conversions because the radicals are confined to a narrow reaction layer at the electrode surface. This layer arises from the slow diffusion of the radicals generated in high concentration at the electrode surface into the bulk of the solution and their fast reaction on this way. The more reactive the radical is, the narrower the reaction layer will be and thus the higher is the concentration of the radical. [Pg.128]

Conversion Engineering Conference Proceedings, Volume 3, Conversion Technologies/Electrochemical Conversions, San Diego, CA August 3-7, 1992, published by Society of Automotive Engineers, Inc., Warrendale, PA, 407, 1992. [Pg.93]

This idea of current flowing as a function of polarizing the electrode (shifting its potential away from equilibrium) lies at the very heart of voltammetry. Note that the magnitude of the current - and current is a derivative quantity (equation (2.1)) - tells us the rate at which the electrochemical conversion occurs. [Pg.135]

Fuel cell operation entails (1) coupled proton migration and water fluxes in the PEM, (2) circulation and electrochemical conversion of electrons, protons, reactant gases, and water in CLs, and (3) gaseous diffusion and water exchange via vaporization/condensation in pores and channels of CLs, GDLs, and EEs. All components of an operating cell have to cooperate well in order to optimize the highly nonlinear interplay of these processes. It can be estimated that this optimization involves several 10s of parameters. [Pg.346]


See other pages where Electrochemical conversion is mentioned: [Pg.183]    [Pg.610]    [Pg.945]    [Pg.210]    [Pg.222]    [Pg.222]    [Pg.223]    [Pg.224]    [Pg.225]    [Pg.225]    [Pg.576]    [Pg.206]    [Pg.155]    [Pg.273]    [Pg.265]    [Pg.347]    [Pg.8]    [Pg.460]    [Pg.163]    [Pg.50]    [Pg.85]    [Pg.401]    [Pg.421]    [Pg.497]    [Pg.92]    [Pg.92]    [Pg.93]    [Pg.93]    [Pg.93]    [Pg.351]    [Pg.417]    [Pg.93]   
See also in sourсe #XX -- [ Pg.22 , Pg.49 , Pg.88 , Pg.129 , Pg.134 , Pg.135 , Pg.141 , Pg.304 , Pg.305 , Pg.350 ]

See also in sourсe #XX -- [ Pg.179 ]

See also in sourсe #XX -- [ Pg.647 ]




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