Effect Of Carbon Dioxide Pressure Research Articles

Supercritical Fluid Extraction of Oils and Waxes from Grape Seeds with Carbon Dioxide

Abstract—The effect of carbon dioxide pressure, temperature, and time on the efficiency of supercritical fluid extraction of fatty oil and wax from grape seeds is studied. We find the optimum conditions for the production of oil and wax from grape seeds using supercritical carbon dioxide as an efficient extracting solvent, which showed an advantage over traditionally used organic solvents. The organoleptic and physicochemical parameters of extracts are determined; the fatty acid composition of grape oil is studied using chromato-mass spectrometry. It has been shown that two natural valuable products can be obtained from grape seeds by supercritical fluid extraction with carbon dioxide, namely, grape-seed oil and wax, which are used widely in the food, pharmaceutical, and cosmetological industries.

Corrosion Behavior of Austenitic Stainless Steels in CO2-Saturated Synthetic Oil Field Formation Water

The corrosion behavior of austenitic and superaustenitic stainless steels was investigated in carbon dioxide-saturated synthetic oil field formation water using cyclic polarization tests. In order to measure the effect of carbon dioxide pressure, the samples were also exposed in a pressurized medium containing carbon dioxide and synthetic air. For this purpose, tests were performed for long exposure time at 80 °C under 8 MPa of a mixture of carbon dioxide and synthetic air both acting togethere. The results indicated that the type of corrosion on the surfaces of the samples after all the tests was pitting corrosion. According to the results, the AL-6XNPLUS™ steel presented the best performance in all experiments. The results also indicated that the conventional austenitic stainless steels are not suitable for the use in carbon dioxide containing environment in aqueous medium.

Utilization of Alkali-Activated Olivine in Soil Stabilization and the Effect of Carbonation on Unconfined Compressive Strength and Microstructure

This paper reports for the first time the stabilization of soil using olivine and the application of novel techniques utilizing alkaline activation and carbonation. A rigorous study addressed the effect of carbon dioxide pressure and alkali concentration (10-M sodium hydroxide soil additions from 5 to 20%) between 7 and 90 days. Microstructural and compositional changes were evaluated using microscopic, spectroscopic, and diffraction techniques. Results demonstrate the advantages of using olivine in the presence of NaOH and the associated increases in soil shear strength of up to 40% over 90 days. Samples subjected to carbonation for a further 7 days led to additional increases in soil strength of up to 60%. Microstructural investigations before and after carbonation attributed the strength development to the formation of Mg(OH)2, hydrated magnesium carbonates, and M─S─H, A─S─H gel phases. The impact of this work is far reaching and provides a new soil stabilization approach. Key advantages include significant improvements in soil strength with a lower carbon footprint compared with lime or cement stabilization.

Utilisation of carbonating olivine for sustainable soil stabilisation

This paper describes the first study demonstrating the potential of olivine as a soil stabiliser. Olivine has been shown to provide a reactive source of magnesium oxide capable of sequestering carbon dioxide. The effects of olivine additions on consistency limits, compaction characteristics and unconfined compressive strength (UCS) of soil are described. The effect of carbon dioxide pressure, and carbonation period, on the UCS of olivine-treated soil is of great importance in defining treated properties. Results highlight the benefits of olivine in soft soil stabilisation with reference to the UCS. Use of 20% olivine decreased the plasticity index and optimum moisture content while increasing the maximum dry density of the soil. The greatest strength was developed after carbonation at 200 kPa for 168 h in the soil containing 20% olivine. Structural and compositional analysis using scanning electron microscopy and X-ray diffraction confirmed the benefits of olivine in terms of decreasing the discontinuity of soil. This was attributed to the crystallisation products responsible for strength development after carbonation, respectively. The paper is significant as it presents a more environmentally friendly method of stabilising soils compared with alternative methods using high embodied energy binders such as cement.

Electrochemical reduction of carbon dioxide to formic acid at a tin cathode in divided and undivided cells: effect of carbon dioxide pressure and other operating parameters

The reduction of carbon dioxide to formic acid at a tin cathode was studied in both divided and undivided cells. In the first stage of the study, the effect of some operating parameters, including the working potential and the nature of the supporting electrolyte and of the cathode, on both the cathodic reduction of CO2 and the anodic oxidation of formic acid was investigated in a divided cell. In a second stage, the reduction of carbon dioxide was performed in an undivided cell with the aim of studying the effect on the generation of formic acid of various operating parameters such as current density, cathode to anode area ratio, mixing rate and nature of the anode and of the supporting electrolyte. A detailed investigation on the effect of the carbon dioxide pressure was also carried out. The utilization of relatively high CO2 pressures (15–30bar) allowed to achieve high concentrations of formic acid (up to 0.46molL−1) working with high current density (up to 90mAcm−2) and using cheap and simple undivided cell and electrodes.

Effect of Carbon Dioxide Pressure on 4-<i>t</i>-Butylphenol Hydrogenation Activity of Supported Rhodium Catalyst

Hydrogenation of 4-t-butylphenol over an activated carbon-supported rhodium catalyst in carbon dioxide solvent was analyzed based on phase observation with a view cell and calculations of the solubility of 4-t-butylphenol using the Peng-Robinson equation of state as a function of carbon dioxide pressure. The reaction experiments showed that the initial reaction rate of 4-t-butylphenol at 313 K under 2 MPa of hydrogen pressure was increased by the addition of carbon dioxide, especially above a total pressure of 11 MPa. Direct visual observation showed that the solubility of 4-t-butylphenol increased with higher carbon dioxide pressure. The calculations based on the Peng-Robinson equation of state also showed that the solubility of 4-t-butylphenol in the 4-t-butylphenol–carbon dioxide–hydrogen (2 MPa) system at 313 K significantly increased by addition of carbon dioxide above a total pressure of 11 MPa. We concluded that the increase in the hydrogenation rates was caused by the increased concentration of 4-t-butylphenol substrate in the carbon dioxide solvent.

Phase Behavior of Hydrogenation of 2-tert-Butylphenol over a Charcoal-Supported Rhodium Catalyst in Carbon Dioxide Solvent

Catalytic hydrogenation of 2-tert-butylphenol over a charcoal-supported rhodium catalyst in carbon dioxide solvent at 313 K was studied in a batch reactor. To elucidate the effect of carbon dioxide pressure on the initial rate of reaction, the phase behavior of the ternary (2-tert-butylphenol−carbon dioxide−hydrogen) system was separately observed with a view cell, and the calculations of vapor−liquid equilibrium and compositions in the vapor and liquid phases inside the reactor were carried out using the Peng−Robinson equation of state. The hydrogenation behavior in the carbon dioxide solvent is discussed based on the phase behavior of the ternary system.

Catalytic performance of pyridinium salt ionic liquid in the synthesis of cyclic carbonate from carbon dioxide and butyl glycidyl ether

The catalytic performance of pyridinium salt ionic liquids in the reaction of butyl glycidyl ether and carbon dioxide was investigated in this study. The catalytic activity was studied in a batch reactor with different 1-alkylpyridinium salt ionic liquids at 60–140°C. The conversion of butyl glycidyl ether was affected by the structure of the ionic liquid; the one with the cation of bulkier alkyl chain length showed better reactivity. The effect of carbon dioxide pressure, reaction temperature and zinc bromide co-catalyst on this reaction was also discussed.

Effect of carbon dioxide pressure on Listeria monocytogenes in physiological saline and foods

The effect of 15,30 and 60 atm CO2pressure at 25,35 and 45°C on Listeria monocytogenes was studied. A biphasic curve was observed in the CO2treatments. A primary curve was characterized with very little killing and a secondary curve was showed straight-line inactivation kinetics. An increase of pressure and/or temperature enhanced the antimicrobial effects of CO2. Listeria monocytogenes suspended in physiological saline containing 1% brain–heart infusion broth was completely inactivated under 60 atm CO2treatment in 115,75 and 60 min at 25,35 and 45°C, respectively. A minimum D -value was obtained under 60 atm CO2pressure at 45°C. High pressure CO2treatment technique can possibly be applied to reduce microbiol load in whole and skim milk; and carrot, orange, peach, and apple juices.

THE RESPONSE OFSACCHAROMYCES CEREVISIAETO FERMENTATION UNDER CARBON DIOXIDE PRESSURE

When laboratory fermenters containing 4 litres of wort were maintained under a variety of conditions at an excess pressure of 2 atm of carbon dioxide throughout fermentation by Saccharomyces cerevisiae (NCYC 1108), the fermentation rate, yeast growth and final concentration of fusel oils all decreased and the final pH increased. This agrees with reported work on the effect of carbon dioxide pressure on fermentation by S. carlsbergensis. The effect of carbon dioxide pressure on the production and removal of vicinal diketones and their precursors by S. carlsbergensis is known to be variable but except at very low temperatures, pressure has either no effect or increases the rate of removal of these compounds in the final stages of fermentation. In the present experiments with a strain of C. cerevisiae, however, carbon dioxide pressure always led to the fresh beer having a higher lever of vicinal diketones and their precursors than the control fermentation, even at temperatures up to 20°C.

Electrochemical measurement on the photoelectrochemical reduction of aqueous carbon dioxide on p-Gallium phosphide and p-Gallium arsenide semiconductor electrodes

The photoelectrochemical reduction of aqueous carbon dioxide was carried out using single crystal p-gallium phosphide and p-gallium arsenide as photocathodes. The organic products measured were mainly formic acid, but also formaldehyde and methanol. The effect of carbon dioxide pressure on the current-potential relationships and on yields of organic reduction products was studied using a photoelectrochemical autoclave, fitted with a quartz window. Highest Faradaic yield of reduction products, 80%, was obtained with a p-GaP cathode at a cathodic bias of -1.00 V (vs. a standard silver electrode), in a medium initially 0.5 M Na 2CO 3, under 8.5 atm pressure of CO 2, a cation exchange diaphragm and a platinum counterelectrode, under illumination with a 150 W Xe lamp.

Effect of carbon dioxide pressure on the rate of decomposition of calcite (CaCO3)

Rates of CO/sub 2/ escape from (1011) clevage surfaces of calcite (CaCO/sub 3/) single crystals were measured at temperatures from 893 to 1073 K and at CO/sub 2/ background pressures, P/sub CO/sub 2//, from 10/sup -2/P/sub eq/, but do not obey the parabolic rate law deduced by earlier investigators from data in a limited pressure range. For P/sub L/ < P /sub CO/sub 2// < 10/sup -2/P/sub eq/, the decomposition rates are essentially independent of P/sub CO/sub 2//, which implies that in this range the apparent activation enthalpy and entropy are unchanged from those measured under vacuum, ..delta..H* = 209 +/- 12 kJ (50 +/- 3 kcal) and ..delta..S* = 84 +/- 12 J/deg (20 +/- 3 cal/deg). The rate-limiting process in this pressure range is probably condensed-phase diffusion of CO/sub 2/ or a surface step for CO/sub 2/ prior to desorption.

Thermal studies on lead(II) salts—I Stoicheiometry of lead carbonate decomposition at 1 atm. pressure

The thermal decomposition of lead(II) carbonate has been studied by thermogravimetry under various partial pressures of carbon dioxide. The TG curves have been followed by X-ray diffraction and the results interpreted in terms of the following reaction scheme: 6 PbCO 3=3( PbCO 3. PbO)+3 CO 23( PbCO 3. PbO)=2( PbCO 3.2 PbO)+ CO 22( PbCO 3.2 PbO)=6 PbO+ CO 2. No evidence of other intermediates was found, and a possible explanation of the many intermediates previously postulated has been made in terms of the effect of carbon dioxide pressure on the rate of decomposition of PbCO 3.PbO.

The effect of carbon dioxide pressure on a bacterial decarboxylase system.

SUMMARY: The effect of CO2 on a decarboxylase system of Streptococcus diacetilactis has been investigated. It was found that the amount of CO2 produced by a culture of the living organism depended upon the proportion of CO2 present in the atmosphere. Under minimum p CO2 the production of CO2 by the organism was stimulated while accumulation of CO2 repressed the formation of the gas. It also appeared that the presence of excess of other products of reaction repressed the production of CO2. An explanation of these phenomena in terms of the law of mass action is advanced. The effect of CO2 upon the production of decarboxylase by the organism was also investigated. There was some indication that the composition of the gaseous environment influenced the production of decarboxylase.