High-pressure CO2 Research Articles

Dehydrogenative Diboration of Alkynes Catalyzed by Ir/CO/tBuNC System

Catalytic dehydrogenative diboration (DHDB) of alkyne with HBpin was achieved using [Ir(COD)Cl]2 and other related Ir precursors under CO atmosphere. The selectivity for DHDB over hydroboration was higher in less polar solvents and under higher CO pressure. It was further improved when catalytic amount of tBuNC was added to the reaction. It was possible to achieve DHDB of both terminal and internal alkynes with selectivity for DHDB of up to 9:1 under the best conditions. Some DHDB products were isolated on the preparative scale.

Bio-tar-derived porous carbon with high gas uptake capacities

The separation of CO2 from the nature gas is a challenge for solid sorbents. Bio-tar, a low cost and renewable carbon source, is employed to synthesis the ultra-microporous carbon materials. Carbonization of bio-tar with potassium hydroxide (KOH) at high temperatures (>700 °C) yields porous carbon materials with high surface areas of up to 2595 m2 g−1 and high CO2 uptake performance of 5.35 mmol g−1 at 1 bar and 0 °C. This carbon material also shows good CO2/CH4 selectivity in mixed gas and excellent cyclability. In gas breakthrough test, the retention time of bio-tar-derived carbon for carbon dioxide and methane adsorption is 849 s g−1 and 337 s g−1, respectively. The retention time of CO2 is 157 s g−1 at 150 °C while CH4 is nearly non-adsorption. The carbon material has good cycle performance for carbon dioxide adsorption. Molecular simulations suggest that CO2 density in micro and narrow mesopores will be increased at high pressures. This is consistent with the observation that these pores are mainly responsible for the material’s high-pressure CO2 capacity. This study provides insights in designing of bio-tar material and further developing for CO2 capture from natural gas.

Powder coating and dissolution rate modification of L-leucine supplements with hydrophilic fumed SiO2 nanoparticles by ultrasonic irradiation in high-pressure liquid CO2

The dissolution properties of l-leucine (L-Leu) supplements with hydrophobic surfaces were improved by coating particles with hydrophilic fumed SiO2 nanoparticles (Aerosil 200FAD) using ultrasonic irradiation in high-pressure liquid carbon dioxide (CO2). Shock waves generated by the collapse of cavitation bubbles induced by ultrasonic irradiation accelerated the deagglomeration and dispersion of SiO2 nanoparticles and achieved dry-particle coating in high-pressure liquid CO2. The dissolution rate of the l-Leu microparticles was increased by coating with SiO2 nanoparticles. The effects of the experimental conditions (size and concentration of the SiO2 nanoparticles, coating method, depressurizing method, and ultrasonic irradiation time) on the morphology and dissolution rate of the composite particles were also investigated.

Liquid CO 2 high‐pressure fracturing of coal seams and gas extraction engineering tests using crossing holes: A case study of Panji Coal Mine No. 3, Huainan, China

Owing to the low coal permeability coefficients and poor gas extraction efficiencies associated with the extraction of coal in the Huainan coal mining area, the aim of this study was to design, for the first time, a high-pressure low-temperature liquid CO2 (LCO2) pump for engineering tests with respect to the fracturing of coal seams and the improvement of CH4 recovery in China. To reasonably calculate the initiation pressure for the coal seam fracturing as well as the gas flow parameters, theoretical analysis with field testing were integrated in the design. In addition, considering the interim gas extraction standard, the gas extraction equivalent radius based on this standard was calculated. The test results revealed a maximum LCO2 pressure of 20.6 MPa, which surpasses the theoretical maximum pressure (19.5 MPa) required for the fracturing of coal seams. During the entire gas extraction process, the CO2 concentrations in boreholes K1 and K3 decrease exponentially with time, showing attenuation coefficients of 0.0205 and 0.0231, respectively. The attenuation coefficients of the three attenuation stages of the original coal seam gas flow rate were 0.0314, 0.2142, and 0.1198, which were higher than those corresponding to the test area. The CH4 concentration in boreholes K1 and K3 in the test area were both higher than that in the original coal seam, and the maximum CH4 flow rates in these boreholes were 1.31- and 1.72-fold higher than that in the original coal seam, respectively. The comparative analysis of CH4 concentrations and flow rates indirectly showed an improvement in the permeability of the coal seam. Further, a quantitative equivalent gas extraction evaluation method based on LCO2 fracturing of coal seam and gas displacement was proposed. Furthermore, based on a comprehensive evaluation, the effective displacement radius caused by the LCO2 fracturing test was 9 m, with a displacement efficiency of 23.95%, and a displacement volume ratio of 0.21. This method offered the possibility of realizing the quantitative evaluation of the LCO2 injection amount and the gas extraction effect, and provides a basis for optimizing the LCO2 fracturing of coal seams as well as the gas extraction process.

Principles of Gold Nanoparticles Stabilization with Chitosan in Carbonic Acid Solutions Under High CO2 Pressure

Principles of Gold Nanoparticles Stabilization with Chitosan in Carbonic Acid Solutions Under High CO2 Pressure

Bioceramic powders for bone regeneration modified by high-pressure CO2 process

Non-stoichiometric nanocrystalline apatites present enhanced bioactivity compared to stoichiometric hydroxyapatite. The purpose of this work was to modify the calcium phosphates (CaP) generally used to prepare bioactive ceramics in the aim of obtaining a biomimetic apatite powder. Hydroxyapatite (HA) powder, amorphous tricalcium phosphate (amTCP) powder and a blend of these two were modified by means of an innovative, simple, “green” carbonation process, involving water and high-pressure CO2 (80 bar). This process induced a modification of the CaP, which is sensitive to the environment in which it is located and, in particular, to the pH variations that occur during the treatment phase (decrease in the pH) and during the degassing phase (return to neutral pH). FTIR and Raman spectroscopy, XRD and SEM analyses showed that, depending on the type of initial CaP powder, high-pressure CO2 treatment led to the formation of different types of calcium phosphate phases. This process allowed partial dissolution of the initial powder, mainly of TCP when present, and precipitation of a new CaP phase. HA and HA/amTCP powders were transformed into a mixture of OCP and immature carbonated apatite (PCCA) phases, including OCP maturation/transformation into PCCA. In the case of amTCP powder, a DCPD phase was also present due to the high TCP solubility and an earlier precipitation during the degassing step. This work shows the great potential of such an innovative low-temperature and high-pressure process to transform HA, HA/TCP and TCP powder into bioactive biphasic ceramics composed of OCP and PCCA similar to bone mineral.

Molten Salt Treated Cu Foam Catalyst for Selective Electrochemical CO2 Reduction Reaction

AbstractThe electrochemical reduction of CO2 is a promising route to convert waste products to valuable chemicals. Search for suitable and efficient CO2 reduction electrocatalysts with high C2:C1 selectivity holds great promise. Herein, for the first time we have developed a molten salt oxidized method to modify the morphology and oxidation state of a Cu‐foam catalyst. The catalyst displayed a current density of 30 mA cm−2 (−1.4 V versus reversible hydrogen electrode) and an ethylene/methane ratio of 870. We provide insight into the improved performance of the catalysts by cross section scanning transmission electron microscopy and quasi in situ soft X‐ray spectroscope, which show that copper oxides are surprisingly reconstructed with Cu (I) and Cu (0) on the surface during the reaction. First principle calculations also demonstrate that the partly reduced Cu2O (111) surface has a high reactivity and selectivity for C2+ products. Furthermore, the molten salt treated catalysts could be applied to the direct synthesis of multi‐carbon fuels, including C3‐C4 compounds in high CO2 pressure electrocatalytic reduction. Our results demonstrate that molten salt are both the oxidizing agent and reaction medium, which is a promising approach for synthesis of highly active CO2 electrocatalysts, which may open a new way for industrial application.

Temperature-dependent Crystallization and Phase Transition of Poly(L-lactic acid)/CO2 Complex Crystals

Semicrystalline polymers can crystallize in the unique crystalline polymorph and show different phase behaviors under the high-pressure CO2 treatment. Understanding such unique crystallization and phase transition behavior is of fundamental importance for the CO2-assisited processing of semicrystalline polymers. Herein, we investigated the polymorphic crystalline structure, phase transition, and structure-property relationships of poly(L-lactic acid) (PLLA) treated by CO2 at different pressures (1–13 MPa) and crystallization temperatures (Tc’s, 10–110 °C). PLLA crystallized in the PLLA/CO2 complex crystals under 7–13 MPa CO2 at Tc ≤ 50 °C but the common a crystals under the high-pressure CO2 at Tc ≥ 70 °C. Solid-state nuclear magnetic resonance analysis indicated that the PLLA/CO2 complex crystals possessed weaker interactions between the PLLA chains than the common a crystals. The PLLA/CO2 complex crystals were metastable and transformed into the thermally stable a crystals via the solid-to-solid route during heating or annealing at the temperature above 50 °C. The complex crystals of PLLA produced at low Tc was more ductile than the a crystals due to the lower crystallinity and the plasticizing effect of CO2.

Platinum cross‐linked chitosan hydrogels synthesized in water saturated with CO2 under high pressure

AbstractThe creation of biocompatible composite hydrogels from renewable biopolymers with stabilized functional platinum nanoparticles seems to be an important scientific task. The formation of such hydrogels in a unique medium of carbonic acid under high pressure CO2 is promising due to its sterilizing ability under pressure, biocompatibility after decompression and environmental friendliness. In the present work, stable chitosan hydrogels with platinum nanoparticles were obtained in such solutions. The hydrogel nature of the composites was confirmed by rotational rheology. The physicochemical characteristics were studied using Fourier transform infrared, X‐ray photoelectron, ultraviolet–visible spectroscopies, transmission electron, scanning electron and atomic force microscopies. It was found that nanoparticles of oxidized Pt of approximately 4.5 nm in size are stabilized by chitosan in the composite. The resulting chitosan/Pt hydrogels were also tested for antimicrobial activity and shown strong activity against Gram‐positive bacteria (B. subtilis and B. coagulans) and slight activity against E. coli.

Constraints on deep, CO2-rich degassing at arc volcanoes from solubility experiments on hydrous basaltic andesite of Pavlof Volcano, Alaska Peninsula, at 300 to 1200 MPa

Abstract The solubility of CO2 in hydrous basaltic andesite was examined in fO2-controlled experiments at a temperature of 1125 °C and pressures between 310–1200 MPa. Concentrations of dissolved H2O and CO2 in experimental glasses were determined by ion microprobe calibrated on a subset of run glasses analyzed by high-temperature vacuum manometry. Assuming that the solubility of H2O in mafic melt is relatively well known, estimates of XH2Ofluid and PH2Ofluid in the saturating fluid were modeled, and by difference, values for XCO2fluid and PCO2fluid were obtained (XCO2 ~0.5–0.9); fCO2 could be then calculated from the fluid composition, temperature, and pressure. Dissolved H2O over a range of 2.3–5.5 wt% had no unequivocal influence on the dissolution of CO2 at the pressures and fluid compositions examined. For these H2O concentrations, dissolved CO2 increases with fCO2 following an empirical power-law relation: dissolved CO2 (ppmw) = 14.9−3.5+4.5[fCO2 (MPa)]0.7±0.03. The highest-pressure results plot farthest from this equation but are within its 1 standard-error uncertainty envelope. We compare our experimental data with three recent CO2-H2O solubility models: Papale et al. (2006); Iacono-Marziano et al. (2012); and Ghiorso and Gualda (2015). The Papale et al. (2006) and Iacono-Marizano et al. (2012) models give similar results, both over-predicting the solubility of CO2 in a melt of the Pavlof basaltic andesite composition across the fCO2 range, whereas the Ghiorso and Gualda (2015) model under-predicts CO2 solubility. All three solubility models would indicate a strong enhancement of CO2 solubility with increasing dissolved H2O not apparent in our results. We also examine our results in the context of previous high-pressure CO2 solubility experiments on basaltic melts. Dissolved CO2 correlates positively with mole fraction (Na+K+Ca)/Al across a compositional spectrum of trachybasalt-alkali basalt-tholeiite-icelandite-basaltic andesite. Shortcomings of current solubility models for a widespread arc magma type indicate that our understanding of degassing in the deep crust and uppermost mantle remains semi-quantitative. Experimental studies systematically varying concentrations of melt components (Mg, Ca, Na, K, Al, Si) may be necessary to identify solubility reactions, quantify their equilibrium constants, and thereby build an accurate and generally applicable solubility model.

Development of Pump-Drive Turbine Module with Hydrostatic Bearing for Supercritical CO2 Power Cycle Application

The turbomachinery used in the sCO2 power cycle requires a high stable rotor-bearing system because they are usually designed to operate in extremely high-pressure and temperature conditions. In this paper, we present a pump-drive turbine module applying hydrostatic bearing using liquid CO2 as the lubricant for a 250 kW supercritical CO2 power cycle. This design is quite favorable because stable operation is possible due to the high stiffness and damping of the hydrostatic bearing, and the oil purity system is not necessary when using liquid CO2 as the lubricant. The pump-drive turbine module was designed to operate at 21,000 rpm with the rated power of 143 kW. The high-pressure liquid CO2 was supplied to the bearing, and the orifice restrictor was used for the flow control device. We selected the orifice diameter providing the maximum bearing stiffness and also conducted a rotordynamic performance prediction based on the designed pump-drive turbine module. The predicted Campbell diagram indicates that a wide range of operation is possible because there is no critical speed below the rated speed. In addition, an operation test was conducted for the manufactured pump-drive turbine module in the supercritical CO2 cycle test loop. During the operation, the pressurized CO2 of the 70 bar was supplied to the bearing for the lubrication and the shaft vibration was monitored. The successful operation was possible up to the rated speed and the test results showed that shaft vibration is controlled at the level of 2 μm for the entire speed range.

Zinc Imine Polyhedral Oligomeric Silsesquioxane as a Quattro-Site Catalyst for the Synthesis of Cyclic Carbonates from Epoxides and Low-Pressure CO2.

In the present research, the synthesis, spectroscopic characterization, and structural investigations of a unique ZnII complex of imine-functionalized polyhedral oligomeric silsesquioxane (POSS) is designed, and hereby described, as a catalyst for the synthesis of cyclic carbonates from epoxides and CO2. The uncommon features of the designed catalytic system is the elimination of the need for a high pressure of CO2 and the significant shortening of reaction times commonly associated with such difficult transformations like that of styrene oxide to styrene carbonate. Our studies have shown that imine-POSS is able to chelate metal ions like ZnII to form a unique coordination complex. The silsesquioxane core and the hindrance of the side arms (their steric effect) influence the construction process of the homoleptic Zn4@POSS-1 complex. The compound was characterized in solution by NMR (1H, 13C, 29Si), ESI-MS, UV/Vis spectroscopy and in the solid state by thermogravimetric/differential thermal analysis (TG-DTA), elemental analysis, diffuse reflectance infrared Fourier transform spectroscopy (DRIFTS), cross-polarization magic angle spinning (CP MAS) NMR (13C, 29Si) spectroscopy, and X-ray crystallography.

High-Pressure CO Phases on Co(0001) and Their Possible Role in the Fischer–Tropsch Synthesis

The cobalt catalyst used in the Fischer-Tropsch synthesis, under the conditions of the reaction, is covered by a dense adsorption layer in which CO is the main constituent. To obtain insight into t...

Two-color emission of BaWO4 crystals pumped by 472 nm 0.11 ps laser pulses for frequency conversion into the longwave IR domain

The frequency conversion of Ti:Sapphire laser second harmonic pulses into two-color emission using a tandem of BaWO4 Raman crystals was experimentally demonstrated with an internal efficiency of ∼17%. The output emission contained symmetrical Stokes and anti-Stokes spectral components separated by 902 cm−1 with a full-width half-maximum bandwidth of ≥110 cm−1 each. The applicability of this two-color emission was numerically verified for the production of longwave infrared ultrashort pulses suitable for seeding a high-pressure CO2 laser amplifier via difference frequency generation in LiGaS2 crystal.

Genetic Improvement of Torulaspora delbrueckii for Wine Fermentation: Eliminating Recessive Growth-Retarding Alleles and Obtaining New Mutants Resistant to SO2, Ethanol, and High CO2 Pressure.

The use of Torulaspora delbrueckii has been repeatedly proposed to improve a wine’s organoleptic quality. This yeast has lower efficiency in completing wine fermentation than Saccharomyces cerevisiae since it has less fermentation capability and greater sensitivity to SO2, ethanol, and CO2 pressure. Therefore, the completion of fermentation is not guaranteed when must or wine is single-inoculated with T. delbrueckii. To solve this problem, new strains of T. delbrueckii with enhanced resistance to winemaking conditions were obtained. A genetic study of four wine T. delbrueckii strains was carried out. Spore clones free of possible recessive growth-retarding alleles were obtained from these yeasts. These spore clones were used to successively isolate mutants resistant to SO2, then those resistant to ethanol, and finally those resistant to high CO2 pressure. Most of these mutants showed better capability for base wine fermentation than the parental strain, and some of them approached the fermentation capability of S. cerevisiae. The genetic stability of the new mutants was good enough to be used in industrial-level production in commercial wineries. Moreover, their ability to ferment sparkling wine could be further improved by the continuous addition of oxygen in the culture adaptation stage prior to base wine inoculation.

Transient behaviour of liquid CO2 decompression: CFD modelling and effects of initial state parameters

A non-equilibrium phase transition computational fluid dynamics (CFD) model for liquid CO2 decompression with higher prediction accuracy is presented. In this model, Span-Wagner equation of state (EoS) is applied and compiled, the slip velocity between phases is considered, and the interphase mass transfer is controlled by introducing relaxation time coefficients. For validation, the numerical results are compared with the “shock tube” test results, showing good agreement. On this basis, the transient behaviour of the high-pressure liquid CO2 pipelines during decompression is investigated, and the influences of initial state parameters (density and temperature) on the transient behaviour are further studied. It is found that the pressure change amplitude, the pressure change rate, the temperature change amplitude and the temperature change rate, as well as the outlet massflow increase with an increase in initial density and temperature. The durations of the sudden drop process of pressure and temperature are about 100 microseconds (μs). The degree of superheat of liquid CO2 decreases with an increase in initial density during decompression. Besides, the pressure plateau value has a negative linear correlation with the initial density, while a positive linear correlation with the initial temperature.

Carbon depositions within the oxide scale and its effect on the oxidation behavior of low alloy steel in low (0.1 MPa), sub-(5 MPa) and supercritical (10 MPa) CO2 at 550°C

The oxidation behavior of CrMoV steel in 0.1, 5, and 10 MPa CO2 was studied at 550 °C for 500 h. Reaction rates decreased from 0.1–5 MPa, and breakaway occurred sooner with increasing pressure. Amorphous carbon was identified within the inner layer in all CO2 pressure values, while graphite was mainly detected under 5 and 10 MPa. Carbon deposition may link to the formation of Fe- and (Fe, Ni)-rich M3C carbides at the oxide/steel interface, which catalyzed the Boudouard reaction. A high external CO2 pressure and the oxidation of Cr-rich carbides within the steel may favor carbon depositions.

Composite amine mixed matrix membranes for high-pressure CO2-CH4 separation: synthesis, characterization and performance evaluation.

The key challenge in the synthesis of composite mixed matrix membrane (MMMs) is the incompatible membrane fabrication using porous support in the dry–wet phase inversion technique. The key objective of this research is to synthesize thin composite ternary (amine) mixed matrix membranes on microporous support by incorporating 10 wt% of carbon molecular sieve (CMS) and 5–15 wt% of diethanolamine (DEA) in polyethersulfone (PES) dope solution for the separation of carbon dioxide (CO2) from methane (CH4) at high-pressure applications. The developed membranes were evaluated for their morphological structure, thermal and mechanical stabilities, functional groups, as well as for CO2-CH4 separation performance at high pressure (10–30 bar). The results showed that the developed membranes have asymmetric structure, and they are mechanically strong at 30 bar. This new class of PES/CMS/DEA composite MMMs exhibited improved gas permeance compared to pure PES composite polymeric membrane. CO2-CH4 perm-selectivity enhanced from 8.15 to 16.04 at 15 wt% of DEA at 30 bar pressure. The performance of amine composite MMMs is theoretically predicted using a modified Maxwell model. The predictions were in good agreement with experimental data after applying the optimized values with AARE % = ∼less than 2% and R2 = 0.99.

A simple experiment on global warming.

A simple experiment has been developed to demonstrate the global warming potential of carbon dioxide (CO2) gas in the Earth's atmosphere. A miniature electric resistance heating element was placed inside an inflatable balloon. The balloon was filled with either air or CO2. Whereas the CO2 partial pressure on the earth's atmosphere is approximately 4 × 10−4 atm, in this experiment, a high partial pressure of CO2 (1 atm) was used to compensate for the short radiation absorption path in the balloon. The element was heated to approximately 50°C, the power was then switched off and the element's cooling trends in air and in CO2 were monitored. It took a longer time to cool the heating element back to ambient temperature in CO2 than in air. It also took longer times to cool the element in larger size balloons and in pressurized balloons when they were filled with CO2. To the contrary, the balloon size or pressure made no difference when the balloons were filled with air. A simple mathematical model was developed, and it confirmed that the radiative heat loss from the element decreased significantly in CO2. This investigation showed that the cooling rate of an object, with surface temperature akin to temperatures found on Earth, is reduced in a CO2-rich atmosphere because of the concomitant lower heat loss to its environment.

Experimental investigation on flow field and induced strain response during SC-CO2 jet fracturing

Even though some numerical simulations and experiments of high-pressure CO2 jetting have conducted, the concerns of the flowing field and induced strain response during SC-CO2 jet fracturing are still unclear. Thus, this study is aimed to investigate the SC-CO2 jetting flow field and strain response in the rock via directly High-Speed Photography (HSP) and strain analysis. The development of SC-CO2 jet in high ambient pressure and limited perforation was analyzed. And the effect of jet pressure, ambient pressure and jet distance on the flow field and strain variation on organic glass was comprehensively studied. According to the results of the flow field of, it is found that the length of the jet core grows with the jet velocity gradually increasing in the time of (0.5–8)x104μs level when SC-CO2 jet starts to penetrate into the perforation and the wall-attached jet appears in the ambient vessel. when the jet pressure varied from 15 MPa to 55 Ma, the penetration depth sharply grows and the maximum strain increases approximately 9.4 times. When the ambient pressure is 8.5 MPa, the optimal jet distance is 6 mm because of the largest penetration depth and maximum strain value. Reducing the ambient pressure to 5.5 MPa, the optimal jet distance rise up to 10 mm. It is concluded that there is optimal jet distance under low ambient pressure, and reducing jet distance is better for the jet fracturing under high ambient pressure. Finally, the relationship between the flow field and strain variation is investigated and discussed by combining the HSP images and strain curves. The above research would be helpful for understanding the flow characteristic and its influence on strain variation around perforation under the ambient environment, which is meaningful for improve the operation procedure of CO2 fracturing.