Carbon dioxide reduction solutions

The mechanism of carbon dioxide reduction in aqueous and nonaqueous solutions was investigated by several authors. It is now generally accepted that the reduction of carbon dioxide to formate ions is a multistep reaction with the intermediate formation of free radicals CO2 and HCO2 either in the solution or adsorbed on the electrode ... 

Mechanisms of carbon dioxide reduction in both aqueous and nonaqueous solutions have been studied mainly at metal electrodes. 

Selective carbon dioxide reduction to CO has been accomplished in a non-aqueous medium that includes tricarbonyl (2,2 -bipyridinium) rhenium , /ac-Re(bpy) (CO)3X (X=Cl, Br) as light-active component and homogeneous catalyst for C02 reduction [183-185]. In dimethylformamide solutions that include TEOA as sacrificial electron donor, photosensitized reduction of C02 to CO proceeds with a quantum efficiency of

Mechanistic investigations have revealed that reductive ET quenching of the rhenium complex (Eq. (54)) yields the catalytic intermediate active in deoxygenation of C02. It has been suggested that carbon... 

A seminar on global wanning and chemistry s role was given. In the seminar chemistry s role was focused to various solutions for carbon dioxide reduction and energy shortage. 

The concentration of carbon dioxide reduction products (formic acid, formaldehyde, and methanol) in the reactor at the end of each run is listed in Table 1. The methanol concentration was determined by gas chromatography using a Porpac T column. Formic acid was determined with an Dionex ion chromatography column, and the formaldehyde was determined with a colorimetric chromatropic acid analysis (J ). We did not examine the solution or gas phase for methane. 

A new method of reducing carbon dioxide/bicarbonate solutions to form methanol and other reduced products is presented. The method overcomes the traditional limitations of electrochemical reduction of carbon dioxide at a cathode in that both the surface potential and concentration of reducing species can be varied independently. 

Regarding suitable cathodes for the electrocatalytic reduction of carbon dioxide to methanol, indium, and tin have good prospects because each has a high overpotential for hydrogen evolution, the chief competitor in aqueous solution for carbon dioxide reduction to methanol ... 

Pearce, D.J. and D. Pletcher (1986). A study of the mechanism for the elecirocatalysis of carbon dioxide reduction by nickel and cobalt square planar eomplexes in solution, y. Electroanal. Chem. 197(1—2), 317—330. 

Huang, H., et al. 1991. In situ Fourier transform infrared spectroscopic study of carbon dioxide reduction on polycrystalline platinum in acid solutions. Langmuir 7 1154-1157. 

K. Subramanian, G. Gomathi and K. Asokan, Reduction of carbon dioxide to formate in an electrochemical membrane reactor in KHCO3 buffer solutions. In N.R. Neelameggham and R.G. Reddy (eds.). Carbon Dioxide Reduction Metallurgy, Publication of The Minerals, Metals Materials Society (TMS), Warrendale,... 

Faurenczy G, J06 F, Nadasdi F (2000) Towards an easy carbon dioxide reduction in aqueous solution. High Press Res 18 251-255... 

Gas Reduction. The use of a gaseous reduciag agent is attractive because the metal is produced as a powder that can easily be separated from the solution. Carbon dioxide, sulfur dioxide, and hydrogen can be used to precipitate copper, nickel, and cobalt, but only hydrogen reduction is appHed on an iadustrial scale. In the Sherritt-Gordon process, the excess ammonia is removed duting the purification to achieve a 2 1 ratio of NH iNi ia solution. Nickel powder is then precipitated by... 

Carbon dioxide generated by the fermentation process must be removed to help maintain the pH of the solution at pH 7.6—8.0. Carbon dioxide also inhibits the activity of the bacteria. The oxidation reduction potential is kept at 100—200 mV. The ideal temperature in the reactor varies with different strains in the bacteria but generally is 25—35°C. 

Diethanolamine (DEA) has replaced MEA as the most widely used amine solvent. High load DEA technologies, such as that developed by Elf Aquitaine, permit the use of high (up to 40 wt % DEA) concentration solutions. The Elf Aquitaine—DEA process allows lower cinculation rates, and has consequent reductions ia capital and utility expenses. DEA tends to be more resistant to degradation by carbonyl sulfide and carbon disulfide than MEA. DEA is, however, susceptible to degradation by carbon dioxide. 

Cold methanol has proven to be an effective solvent for acid gas removal. Cold methanol is nonselective in terms of hydrogen sulfide and carbon dioxide. The carbon dioxide is released from solution easily by reduction in pressure. Steam heating is required to release the hydrogen sulfide. A cold methanol process is Hcensed by Lurgi as Rectisol and by the Institute Francaise du Petrole (IFP) as IFPEXOL. 

As a matter of fact, the main advantage in comparison with HPLC is the reduction of solvent consumption, which is limited to the organic modifiers, and that will be nonexistent when no modifier is used. Usually, one of the drawbacks of HPLC applied at large scale is that the product must be recovered from dilute solution and the solvent recycled in order to make the process less expensive. In that sense, SFC can be advantageous because it requires fewer manipulations of the sample after the chromatographic process. This facilitates recovery of the products after the separation. Although SFC is usually superior to HPLC with respect to enantioselectivity, efficiency and time of analysis [136], its use is limited to compounds which are soluble in nonpolar solvents (carbon dioxide, CO,). This represents a major drawback, as many of the chemical and pharmaceutical products of interest are relatively polar. 

The reduction of carbon dioxide is another of the basic electrochemical reactions that has been studied at modified electrodes. The reduction at Co or Ni phthalocyanine in acidic solution yields formic acid or carbon monoxide A very high selectiv-... 

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