Effect of CO2 pressure

We have investigated the electrochemical reduction of CO2 under high pressure on various metal electrodes in aqueous electrolytes.[1-2] The effect of CO2 pressure on the electrochemical CO2 reduction on metal electrodes was studied. The CO2 reduction at large current density could be achieved on metal electrodes by the high pressure electrolyses due to high concentration of CO2 in the aqueous electrolyte. 

High-rate photoelectrolysis of CO2 was conducted in a high pressure CO2 + methanol medium using p-type semiconductor electrodes. Current densities of up to 100 mA cm 2 were achieved, with current efficiencies of up to 93 % for CO production on a p-InP photocathode. The effect of CO2 pressure on the product distributions was examined for p-InP and p-GaAs. 

Fig.3. ENMP hydrogenation. Effect of CO2 pressure on selectivity of EAMP formation. Reaction conditions catalyst 4%Pd/C - 0.5 g, water - 20 ml, [ENMP] = 1.0 mol/1,...

Figure 7 shows a plot of particle size vs. the ratio of CO2 to aqueous solution mass flow rates. The volumetric flow rates presented in Tables I and II were converted to mass flow rates utilizing the densities of water and dense CO2. It is interesting to observe that, for the two sets of the data of myo inositol (i.e., the effects of CO2 pressure as well as CO2 flow rate), the figure shows a correlation of particle size vs. mass flow rate ratio (the triangles in Figure 7). Particles reduce in size as the CO2 to solution flow rate ratio increases. The data of mannitol (the effect of CO2 flow rate), as represented by the diamonds, also foil in line with the data of myo-inositol.

Figure 4. Effect of CO2 pressure on on morphology of macroporous crosslinked polymer monolith, (a) BET surface area (continuous line = total surface area, hed line = micropore surface area) (b) Percent micropore volume (c) Median pore diameter (d) Intrusion volume (macropore volume).

Table 5.5 Investigations of the effect of CO2 pressure on the E parameter for CaCOs decomposition [9]. (Prom the data reported in different works.)...

Stoichiometric and catalytic Diels-Alder reactions in SCCO2 have been studied extensively. The first report appeared in 1987. The reaction of maleic anhydride and isoprene was conducted in SCCO2, and the effect of CO2 pressure (80-430 bar) on the reaction rate was investigated (Scheme 33). A large increase in the rate was observed near the critical pressure at 35°C. At pressures of 200 bar and above, the... 

The relative rate constants for reaction of Br with toluene (kj ) and cyclopropylbenzene (k(3) in SC-CO2 were assessed by direct competition (Scheme 9). The rate constant ratio k( /lqj in SC-CO2 (40 C, 1,300 psi) was 1.2 0.2 and is nearly identical to that found in CCI4 at the same temperature (1.3 0.1). These obseivations also support the hypothesis that Br properties (i.e., reactivity/selectivtiy) are unaffected by complexation to CO2 solvent. Earlier work has shown that kQ/kjj varies as a function of solvent internal pressure (57). We are presently examining the effect of CO2 pressure on kc/kjj. 

The effect of CO2 pressure was also studied under the same conditions using butyl carbamate in acetonitrile with benzyl chloride as the alkylating agent (equation 7). The results are shown in Figure 1 below and demonstrate the unexpected result that increasing CO2 pressure decreases the rate of the reaction. 

TABLE 4-1. Effect of CO2 pressure on yeast cell growth. 

Figure 7 Effect of CO2 pressure on glass transition temperatures of PS and PMMA [8].

Figure 9-79E. CO2 absorption from atmosphere effect of tower pressure on ICqs at veirious liquor rates. Reproduced by pemrrission of the American Institute of Chemical Engineers, Spector, N. A., emd Dodge, B. F., Trans. AI.Ch.E., V. 42 (1946) p. 827 all rights reserved.

Figure 6-7 Effect of CO2/O2 Ratio on Cathode Performance in an MCFC, Oxygen Pressure is 0.15 atm (20, Figure 5-10, Pgs. 5-20)...

Catalytic hydrogenation in supercritical carbou dioxide has been studied. The effects of temperature, pressure, and CO2 concentration on the rate of reaction are important. Hydrogenation rates of the two double bonds of an unsaturated ketone on a commercial alumina-supported palladium catalyst were measured in a continuous gra-dient-less internal-recycle reactor at different temperatures, pressures, and C02-to-feed ratios. The accurate control of the organic, carbon dioxide, and hydrogen feed flow rates and of the temperature and pressure inside the reactor provided reproducible values of the product stream compositions, which were measured on-line after separation of the gaseous components (Bertucco et al., 1997). 

The solubility data for naphthalene in ethylene and in CO2 are consistent with the data in Figure 3. The proper way to make the comparison is to use the enhancement factor instead of the solubility. The enhancement factor equals y2P/P2 which is simply the actual solubility divided by the solubility in an ideal gas. The enhancement factor removes the effect of vapor pressure which is useful for comparing fluids at constant reduced temperature but at different actual temperatures. In terms of the fugacity coefficient of the solute, 2, the enhancement factor is given by... 

In this study, ethanol extraction using SC CO2 was achieved from 15 to 75 %(v/v) synthetic ethanol solutions and also from fermentation broth. Effects of temperature, pressure, extraction time and initial ethanol concentration on extraction yield were investigated in the ranges of 313 to 333 K and 80 to 160 atmospheres. Optimum conditions for the batch extraction of 15%(v/v) ethanol solution were found using the Box-Wilson optimization method in a linear form. In addition, the effect of consecutive solvent feeding on extraction yield were investigated both with 15 %(v/v) ethanol solution and with fermentation broth. 

Kinetic resolution of 1-phenylethanol catalyzed by CALB was carried out in the IL/SC-CO2 biphasic system. To prevent undesirable reactions and ensure better conversion of (R)-1-phenylethanol, [bmim][PF,5] was chosen for this kind of experiments. Because of the possible direct and indirect effects of the pressure on the activity of biocatalyst its influence was studied between 6 and 36.5 MPa. At aU conditions examined a biphasic reaction medium was attained, which is illustrated in Figure 8.5. The enzyme was suspended in the IL phase, where the reaction took place. The substrates and products resided largely in the supercritical phase, which was also the extractive phase. 

This effect of CO2 is at first somewhat surprising because it implies that the rate of dissociation of N2OB is being accelerated by CO2, which we would expect only if this dissociation were a unimolecular reaction below its high-pressure limit. N2O6 has 7 atoms and 15 internal vibrations (or their equivalent) and probably 2 active rotations. For a completely classical molecule (which N2O6 is not), the RRK theory (Table XI.2) would predict deviations from the high-pressure limit near 0.1 mm Hg, which is... 

Future studies should be pursued under controlled doping conditions and in atmospheres containing CO2 and O2. The known synergistic effect of CO2 on 02-solubility in silicate melts at very high gas pressures has, in fact, been interpreted in terms of Na2C03 formation in solution. Effects of this type could significantly enhance alkali vapor transport in practical combustion systems. 

With tetramethylsilane the only organic reaction product was the trimethylsilyl methyl mercaptan, (CHj)3SiCH2SH, as expected for a C—H bond insertion. Further evidence that the product arose from S( Z)) insertion was provided by the suppressing effect of CO2 on the reaction. A novel feature of this reaction is the large damping effect of (CH3)4Si on the CO rate, as shown by the product rate vs. substrate pressure plot in Figure 12. From simple stoichiometry the following relation should obtain for paraffinic insertion processes ... 

Supercritical CO2 extraction also has been used to selectively extract phosphatidylcholine from de-oiled soybean lecithin (197). The effects of temperature, pressure, and amount of ethanol on phosphatidylcholine extraction were examined, and a high-purity product could be produced with optimized conditions. 

Then, the process was applied to an used motor oil [51]. It appears clearly that an increase of CO2 pressure still permits to increase the permeate flux but the effect is not significant above 15 MPa, which represents the optimum pressure for oil hltration. As a whole, a hux increase higher than 300% may be reached. Finally, from analysis of permeate and retentate, it follows that there is an excellent rejection rate of metals— Fe, Zn, Cu, etc.—which increases with transmembrane pressure up to more than 99% depending on species. For mass concentration factors of about 27, residues with a total metal content less than 4% of the initial load were found oil regeneration was very effective. 

Most commercial ELSDs employ a standard or modified HPLC nebulizer (Venturi flow type). It was believed that this nebulizer was not necessary for SFC because nebulization of the SFC mobile phase is accomphshed by gas expansion in a restrictor which controls pressure and mobile-phase flow rates. To counter the cooling effects of CO2 decompression in the linear fused-silica restrictor and improve heat transfer, Nizery et al., using a Cunow Clichy Model DDL 10 detector, placed the restrictor tip into a heated brass ring and applied heat to a small section of tubing between the restrictor and the drift tube... 

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