Carbon dioxide in methanol

Figure 1. Solubilities of carbon dioxide in methanol-water-lithium chloride at 25°C...

The experimental and predicted results for the ternary system carbon dioxide-methanol-water are listed in Table 7. Chang and Rousseau [47] have measured the solubilities of carbon dioxide in methanol-water mixtures at differents pressures and at temperatures below the critical temperature of carbon dioxide while Yoon [51] have measured the liquid and vapor phase equilibrium composition but overestimates shightly these of carbon dioxide in the liquid phase. 

Naitoh, A., K. Otha, T. Mizuno, H. Yoshida, M. Sakai, and H. Noda (1993). Electrochemical reduction of carbon dioxide in methanol at low temperature. Electrochim. Acfa 38(15) 2177-2179. 

Figure 14-14. Solubility of carbon dioxide in methanol, partial pressure of carbon dioxide = 1 atm. Data of Heitert (1956)...

Figure 14-15. Effect of partial pressure on solubility of carbon dioxide in methanol. Data of Hochgesand (1968)...

Fig. 157. Solubility of carbon dioxide in methanol at 0°C and several pressures pco2> Plots of the mole fraction Nco2 Pcoi nd the corresponding mole ratio Xco2 vs Pco2 o" 1 R-line diagram. From the cm /g S data of Krichevskii and Lebedeva. ...

B.R. Eggins, C. Ennis, R. McConnell and M. Spence, Improved yields of oxalate, glyoxalate and glycolate from electrochemical reduction of carbon dioxide in methanol,/. Appl. Electrochem. T1,1997, 706-712. 

K. Ohta, M. Kawamoto, T. Mizuno and D.A. Lowy, Electrochemical reduction of carbon dioxide in methanol at ambient temperature and pressure, /. Appl. Electrochem. 28,1998,717-724. 

Only recently has a mechanism been proposed for the copper-cataly2ed reaction that is completely satisfactory (58). It had been known for many years that a small amount of carbon dioxide in the feed to the reactor is necessary for optimum yield, but most workers in the field beHeved that the main reaction in the formation of methanol was the hydrogenation of carbon monoxide. Now, convincing evidence has been assembled to indicate that methanol is actually formed with >99% selectivity by the reaction of dissociated, adsorbed hydrogen and carbon dioxide on the metallic copper surface in two steps ... 

The catalytic steam-reforming process of methanol on Cu/ZnO/Ab03 catalyst primarily produces hydrogen and carbon dioxide. In addition, the minor quantities of carbon monoxide are also produced. This mechanism is explained in terms of parallel reactions [11]. 

Kuwabata S, Nishida K, Tsuda R, Inoue H, Yoneyama H (1994) Photochemical reduction of carbon dioxide to methanol using ZnS microcrystaUite as a photocatalyst in the presence of methanol dehydrogenase. J Electrochem Soc 141 1498-1503... 

From the applied point of view, this reaction can be used to solve some important issues (1) production of organic subproducts (e.g., methanol, carbon monoxide, oxalic acid), which can be used for synthesizing many valuable organic substances (2) manufacture of synthetic fuels or energy-storage media and (3) removal and utilization of carbon dioxide in life-support systems for closed environments of spacecraft or submarines. 

Figure 6.8 Separation of Triton X-114 by SFC using prograMmed elution on a 10 cm x 2 mm I.D. Nucleosil column, 3 micrometer packing, at 170 C with UV detection at 278 nm. The separation on the left was performed under isobaric conditions at 210 bar with a mobile phase of carbon dioxide -t- methanol (2 + 0. 5) ml/min. The separation in the center was obtained using a ccmt. sition gradient from 0.025 to 0.4 ml/mln over 8 min with other conditions as above. The separation on the right was obtained using a pressure program from 130 to 375 bar over 8 min with the same mobile phase used for the isobaric sepeuration. (Reproduced with permission from ref. 57. Copyright Preston Publications, Inc.)...

There is no doubt that these applications will grow in the future and that the range of supercritical fluids used (carbon dioxide and methanol modified carbon dioxide, nitrogen dioxide, ammonia, fluoro-hydrocarbons) will increase as will the combination of this technique with mass spectrometric identification of separated compounds. 

Reindt and Hoffler [50] optimized parameters in the supercritical fluid extraction of polyaromatic hydrocarbons from soil. These workers used carbon dioxide -8% methanol for extraction and obtained 88-101% recovery of polyaromatic hydrocarbons in the final high-performance liquid chromatography. 

Barnabas et al. [51] have discussed an experimental design approach for the extraction of polyaromatic hydrocarbons from soil using supercritical carbon dioxide. They studied 16 different polyaromatic hydrocarbons using pure carbon dioxide and methanol modified carbon dioxide. The technique is capable of determining down to lOOmg kgy1 polyaromatic hydrocarbons in soils. 

The ionic conductivity of a solution depends on the viscosity, diffusivity, and dielectric constant of the solvent, and the dissociation constant of the molecule. EFL mixtures can carry charge. The conductivity of perfluoroacetate salts in EFL mixtures of carbon dioxide and methanol is large (10 to 10 " S/cm for salt concentrations of 0.05-5 mM) and increases with salt concentration. The ionic conductivity of tetra-methylammonium bicarbonate (TMAHCO3) in methanol/C02 mixtures has specific conductivities in the range of 9-14 mS/cm for pure methanol at pressures varying from 5.8 to 14.1 MPa, which decreases with added CO2 to a value of 1-2 mS/cm for 0.50 mole fraction CO2 for all pressures studied. When as much as 0.70 mole fraction... 

In addition to the microchannel technology, Battelle has developed a stable, nonpyrophoric, carbon dioxide selective, methanol reforming catalyst. - The catalyst has been demonstrated to be stable in... 

Plant. In plants, mevinphos is hydrolyzed to phosphoric acid dimethyl ester, phosphoric acid, and other less toxic compounds (Hartley and Kidd, 1987). In one day, the compound is almost completely degraded in plants (Cremlyn, 1991). Casida et al. (1956) proposed two degradative pathways of mevinphos in bean plants and cabbage. In the first degradative pathway, cleavage of the vinyl phosphate bond affords methylacetoacetate and acetoacetic acid, which may be precursors to the formation of the end products dimethyl phosphoric acid, methanol, acetone, and carbon dioxide. In the other degradative pathway, direct hydrolysis of the carboxylic ester would yield vinyl phosphates as intermediates. The half-life of mevinphos in bean plants was 0.5 d (Casida et ah, 1956). In alfalfa, the half-life was 17 h (Huddelston and Gyrisco, 1961). 

Exit gases from the Mathieson process are passed through a scrubber to remove any unreacted sulfur dioxide. The Solvay process uses sodium chlorate and sulfuric acid, with methanol as the reducing agent. Products from this process are chlorine dioxide, formic acid, and carbon dioxide. In improved Solvay processes, sulfuric acid demand is reduced by crystallizing out the by-products sodium sulfate, sodium sesquisulfate, or sodium bisulfate (Kaczur and Cawlfield 1993 Vogt et al. 1986). 

Alternatively, copper(l) sulfide may be prepared by heating copper with hydrogen sulfide and hydrogen or by heating the metal with sulfur in an atmosphere of carbon dioxide and methanol vapor. 

The elemental sulfur is removed by conventional technology. The gases are purified by the Lurgi Rectisol process which uses a low temperature methanol wash to remove H2S, COS and CO2. The acid gas stream is then passed to a Stretford unit which is preferred to the Claus unit because of the high percentage of carbon dioxide in the stream. Sulfur in the stack gas would be removed by conventional flue gas desulfurization techniques and the sulfur would then remain as sulphite sludge and not be recovered as elemental sulfur. 

Separations were performed on either silica- or amino-bonded stationary phase columns, using carbon dioxide with various modifiers as mobile phases. Each column exhibited distinctly different selectivities to the examined sulfonamides, the amino-bonded column being much more sensitive to modifier variations. In a continuation of the sulfonamide study, packed-column SFC was further evaluated for possible application to the analysis of furazolidone, chloramphenicol, and lincomycin residues (82). Separation was effected on an amino-bonded stationary phase using carbon dioxide with methanol modifier as the mobile phase, whereas detection was accomplished by MS. 

Supercritical-fluid chromatography has been applied by Ramsey et al. (213) for the determination of trimethoprim, along with three steroid hormones, in swine kidney. Separation was performed on a Spherisorb 5 amino-bonded column, using carbon dioxide with methanol modifier as the mobile phase. Detection at levels greater than 10 ppm was accomplished by tandem mass spectrometry using thermospray interface. However, this method lacks the sensitivity required to detect the low ppb levels likely to occur in milk and tissues. 

Salt effects of lithium chloride and calcium chloride on the solubility of carbon dioxide in a mixture of methanol and water were observed at 25°C and 1 atm. Experimental results can be correlated by the Setschenow equation for a fixed solvent composition of salt-free basis. The salting-out parameter is not linear with solvent composition, which is opposite to the results obtained when a mixed salt is used. 

In the present investigation, the salt effects of lithium chloride and calcium chloride on the solubility of carbon dioxide in the mixed solvents of methanol and water were experimentally studied at 25°C and 1 atm. 

Figure I. Conversion of toluene and methanol with the intervention of carbon dioxide in the side-chain alkylation of toluene with methanol over CsNaX-CsOH...

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