High-pressure Carbon Dioxide Research Articles

Understanding Behavior of Polycaprolactone–Gelatin Blends under High Pressure CO2

Polycaprolactone (PCL) is widely used in biomedical applications as electrospun fibers or porous foams. As PCL is synthetic polymer, many researchers have explored blends of PCL–gelatin to combine mechanical and bioactive properties of individual components. High pressure carbon dioxide (CO2) has been studied to foam and impregnate many biocompatible polymers. In case of PCL–gelatin blends, certain compositions can be swelled reversibly under high pressure CO2 without permanent deformation. This allows successful impregnation of PCL–gelatin blends under CO2. This study summarizes effect of different treatments adopted during impregnation process including high pressure CO2 on several blend compositions of PCL–gelatin blends. Stress relaxation, polymer melting and dissolution were observed during several treatments which affects porosity and scaffold structure significantly. Results summarized in this study will aid in optimum selection of PCL–gelatin blend composition for biomedical applications. Furthermore, CO2 solubility in polymers is restricted due to thermodynamic limitations but can be altered in the presence of a co-solvent to produce better foams. PCL can be foamed using supercritical CO2. However, CO2 foaming of PCL–gelatin blend becomes challenging to simultaneous swelling of PCL and compression of gelatin providing blend structural stability. This study has demonstrated ability of supercritical CO2 to foam PCL–gelatin blends in presence of water to create porous structure. These foams were subjected post-fabrication crosslinking and supercritical CO2 without losing porosity of foams. Thus, creating a strategy to use environmentally benign processes to fabricate, crosslink and impregnate porous scaffolds for biomedical applications.

Evaluation of HPCD batch treatments on enzyme inactivation kinetics and selected quality characteristics of cloudy juice from Golden delicious apples

Cloudy apple juice has been treated by high pressure carbon dioxide (HPCD) as non-thermal technology to inactive polyphenoloxidase and pectinmethylesterase in batch mode. Stirring speed (from 200 to 600 rpm) induced an increase in the enzyme inactivation rate while a triple cycle of pressurization/depressurization led to the same enzyme inactivation efficiency. Enzyme inactivation kinetics were determined at different temperatures (from 35 to 45 °C) and pressures (from 10 to 20 MPa). Data were described by the first order kinetic model and the Weibull model. For the first order kinetic model, decimal reduction time for HPCD treatment was found to be smaller than for mild heating, in the same temperature range. The same tendency was observed for the first decimal reduction time in the Weibull model. HPCD treatment resulted in a homogenization effect reflected in the shifting of the particle size distribution towards smaller diameters after treatment. HPCD treatment did not result in a change of water and oxalate soluble pectin content, total phenolic compounds and hidroxymethylfurfural content.

Influence of Water on the Carbon Dioxide Solubility in [OTf]- and [eFAP]-Based Ionic Liquids

The solubility of high-pressure carbon dioxide in mixtures of ionic liquid and water was determined experimentally for 1-ethyl-3-methylimidazolium trifluoromethanesulfonate and 1-alkyl-3-methylimidazolium tris(pentafluoroethyl)trifluorophosphate ionic liquids (where alkyl is ethyl, butyl, or hexyl). Experiments were performed at 313.15 K and/or 318.15 K, at pressures up to 10 MPa, and for various compositions (dry ionic liquids, 0.1 or 10 wt % of water), depending on the ionic liquid under investigation. It was found that the solubility of carbon dioxide in tris(pentafluoroethyl)trifluorophosphate-based ionic liquids is not affected by the water content, whereas for 1-ethyl-3-methylimidazolium trifluoromethanesulfonate, the carbon dioxide sorption capacity is reduced by up to 10%, when 10 wt % of water is present in the system, at the same temperature and pressure.

A new method for producing porous polymer materials using carbon dioxide and a piston

A new method for manufacturing a porous polymer material is developed. In this method, nonwoven fabric sheets are placed in a high-pressure vessel and carbon dioxide is introduced at its vapor pressure. Then, stacked nonwoven fabric sheets are pressed by a piston along with liquefying carbon dioxide to produce a porous polymer material. Through holes were generated in the manufactured polymer material and scanning electron micrographs revealed that the polymer fibers largely remained intact. Surface observation after peeling off the sheet indicates that physical bonding by caulking to be the possible bonding mechanism. According to this technology, stacking sheets with different mesh roughness could enable the fabrication of a filter with a gradient in the mesh. Pressing an enzyme or a catalyst within the stacked fabric sheets can create a reaction cartridge. Drug-containing porous materials that can control the drug-release rate are also expected.

Effect of high-pressure carbon dioxide processing on the inactivation of aerobic mesophilic bacteria and Escherichia coli in human milk

ABSTRACTThe effect of high-pressure carbon dioxide processing on inactivation of aerobic mesophilic bacteria and Escherichia coli ATCC 25922 inoculated in human milk was investigated. The effect of the ratio between sample mass and CO2 (1:0.2; 1:0.6 and 1:1 m/m); depressurization rate (1, 5.5 and 10 MPa/min); and pressure cycling (1, 3 and 5) were the process variables studied. The best reductions in aerobic mesophilic bacteria as well as in E. coli (>6.0 and >5.0 log, respectively) were obtained with a ratio of 1:1, a depressurization rate of 10 MPa/min, and one cycle of pressurization/depressurization. The depressurization rate was found to be an important variable in the inactivation process. The results suggest that high-pressure carbon dioxide processing can be applied to human milk as a safe alternative to the pasteurization employed in human milk banks.

Dissolution and modification of cellulose using high-pressure carbon dioxide switchable solution

High-pressure carbon dioxide switchable solution with 1,8-diazabicyclo [5.4.0] undec-7-ene (DBU) and ethylene glycol (EG) was applied for a dissolution and modification of cellulose derived from a cassava pulp waste. The switchable solution of DBU and EG were formed by adding carbon dioxide under a pressure range of 0.1–10.0MPa and a temperature range of 298 and 333K. The cellulose was dissolved into the CO2 switchable system at a pressure of 0.1 and 5.8MPa and a temperature of 313K. The precipitates of bicarbonate salt of reaction between DBU and carbon dioxide were observed in the switchable solution at the higher pressures and lower temperatures. The cellulose was also modified in the switchable solution with the ionized DBU, EG and carbon dioxide as analyzed by Fourier transform infrared spectroscopy. The modified cellulose was then utilized for the fabrication of the transparent film.

Analysis of the germination proteins in Alicyclobacillus acidoterrestris spores subjected to external factors.

The presence of Alicyclobacillus acidoterrestris, a thermoacidophilic and spore-forming bacterium, in pasteurized acidic juices poses a serious problem for the processing industry. Therefore, the use of other more effective techniques, such as high hydrostatic pressure (HHP) and supercritical carbon dioxide (SCCD), is considered for preserving juices in order to inactivate these bacteria, while reducing the loss of nutrients and sensory quality of juices. On the other hand, HHP and SCCD when combined with a moderately elevated temperature can induce germination of bacterial spores, making them more vulnerable to inactivation. The spore germination can be also induced by nutrients, such as L-alanine or a mixture of asparagine, glucose, fructose and potassium ions (AGFK). The aim of this work was to determine whether applying activating agents: HHP, SCCD and nutrient germinants (L-alanine and the AGFK mixture), could influence the number of spores which start to germinate and how this affects the proteins involved in the spore germination. SDS-PAGE was used to resolve proteins isolated from the A. acidoterrestris spores. The results that were obtained indicate that the germination of A. acidoterrestris spores treated with HHP, SCCD and nutrient germinants reflect the number of spores which start to germinate. The SDS-PAGE data indicated changes in the level of selected proteins occurring when subjected to the germination activating factors as well as noticeable differences in those proteins' molecular weights.

High-pressure carbon dioxide adsorption kinetics of potassium-modified hydrotalcite at elevated temperature

A method for characterizing the high-pressure CO2 adsorption kinetics of potassium-modified hydrotalcite at elevated temperatures based on a modified static bed is proposed. The pressure drop of the adsorption tube with time was measured by a series of high-sensitivity pressure sensors to calculate the CO2 adsorption curves of the adsorbent. The concept of a hot/cold spot is introduced to eliminate the temperature deviation caused by the dead volume of the pipelines and the temperature disproportion in the tubes. As compared to conventional characterization methods such as thermal gravimetric analysis and fixed bed testing, the proposed method avoids the displacement effect, making it possible to obtain actual adsorption curves above atmospheric pressure. The effect of adsorption temperature (300–450°C) and CO2 partial pressure (0.1–2MPa) and a reversible adsorption isotherm with 30min adsorption/30min desorption, as well as desorption performance under vacuum, were investigated. The adsorption/desorption curves of hydrotalcite increased linearly with the logarithm of the adsorption time in almost all tested conditions. The CO2 uptake reached approximately 0.7 of the total adsorption capacity in less than 0.1min of adsorption time and exceeded 0.9 after 5min. A simple one-step kinetic model based on Elovich-type equations is built to describe the adsorption behavior of hydrotalcite at CO2 partial pressures above atmospheric pressure.

Recent advances in cured raw ham manufacture

ABSTRACTCured raw hams are a valuable and popular group of meat products. The consumption and international trade have increased during the last years, therefore new technologies to accelerate the production process and to increase product quality and safety are needed. In the current review, an overview of European protected cured raw hams is presented. Furthermore, traditional methods for cured raw ham production together with recent advantages in the techniques for pretreatment (trimming, blade tenderization, and freeze-thawing), curing/salting (tumbling, vacuum impregnation, pulsed pressure, ultrasound, pulsed electric fields, simultaneous thawing/salting), drying/ripening (Quick-Dry-Slice-process, oil drop application, high temperature short time process) and postprocessing (vacuum and modified atmosphere packaging, high hydrostatic pressure, high pressure carbon dioxide, high pressure carbon dioxide with ultrasound) are described. Moreover, application techniques and effects of protective cultures and starter cultures, such as molds, yeasts, coagulase-negative staphylococci and lactic acid bacteria, on cured raw ham quality and safety are reviewed.

Hierarchically structured nanoporous carbon tubes for high pressure carbon dioxide adsorption.

Mesoscopic, nanoporous carbon tubes were synthesized by a combination of the Stoeber process and the use of electrospun macrosized polystyrene fibres as structure directing templates. The obtained carbon tubes have a macroporous nature characterized by a thick wall structure and a high specific surface area of approximately 500 m²/g resulting from their micro- and mesopores. The micropore regime of the carbon tubes is composed of turbostratic graphitic areas observed in the microstructure. The employed templating process was also used for the synthesis of silicon carbide tubes. The characterization of all porous materials was performed by nitrogen adsorption at 77 K, Raman spectroscopy, infrared spectroscopy, thermal gravimetric analysis (TGA), scanning electron microscopy (SEM) as well as transmission electron microscopy (TEM). The adsorption of carbon dioxide on the carbon tubes at 25 °C at pressures of up to 30 bar was studied using a volumetric method. At 26 bar, an adsorption capacity of 4.9 mmol/g was observed. This is comparable to the adsorption capacity of molecular sieves and vertically aligned carbon nanotubes. The high pressure adsorption process of CO2 was found to irreversibly change the microporous structure of the carbon tubes.

Ultrafast, Scale-Up Synthesis of Pure and Stable Amorphous Carbonate Mineral Nanoparticles

As important precursors of crystalline phases, amorphous phases of minerals, especially carbonate-based minerals, have been attracting more and more interest in fundamental research and materials chemistry, as well as industrial applications. However, it is still challenging to largely and rapidly synthesize stable amorphous carbonate minerals without the assistance of stabilizers. In this paper, we report an ultrafast method for the high-yield, scale-up synthesis of amorphous carbonate mineral nanoparticles (CaCO3, MgCO3, SrCO3, and their hybrids) within 1 min through the fast diffusion of high-pressure carbon dioxide into ethanol. The present strategy not only allows for the massive production of pure and stable amorphous carbonates but also shows great potential in industrial uses like water treatment.

Increasing permeability of coal seams using the phase energy of liquid carbon dioxide

Carbon dioxide (CO2) is a major greenhouse gas, and it is also an energy source that can be utilized. This paper describes a new technology designed to increase the permeability of coal seams using the phase energy of CO2. The technology, named as liquid carbon dioxide phase change fracturing technology, is classified as physical blasting. The kernel of this technology is the blasting system, which consists of release tube containing release holes, cutting plate, liquid storage tube containing heating pipe, guide tube and detonator following the order from the top to the bottom. By starting the detonator, special chemicals in the heating pipe begin to react and a lot of heats then are released instantly to heat the liquid carbon dioxide in liquid storage tube. This process brought about the phase change of carbon dioxide and then caused the dramatically expansion of the volume of carbon dioxide. When the pressure of carbon dioxide in the liquid storage tube exceeds the strength of the cutting plate, the cutting plate is damaged and high pressure carbon dioxide enters the release tube and acts on the coal body. The sphere of influence of this technology in coal seams was studied by the numerical study. Then, a large-scale industrial experiment using the technology was conducted in an underground coal mine in China based on the modeling results. Application of this technology could not only improve the efficiency of coal seam gas extraction but could also turn carbon dioxide into energy to improve energy efficiency.

High pressure carbon dioxide for impregnation of clove essential oil in LLDPE films

Abstract High-pressure carbon dioxide (CO2) impregnation is a promising technology in the development of active packaging films. Clove essential oil (CEO), a multicomponent active agent naturally rich in eugenol, was incorporated in linear low density polyethylene (LLDPE) films by using high pressure CO2 impregnation. The parameters of temperature (25, 35 and 45 °C), pressure (150 and 250 bar) and CEO:CO2 mass ratio (2 and 10%) were screened using a variable-volume view cell for 4 h to determine the best impregnation conditions. Kinetic assays of CEO impregnation were also performed. The highest amount of CEO (40.2 mg g− 1 of LLDPE) impregnated was obtained at 10% CEO:CO2 mass ratio, 45 °C and 150 bar. The impregnation at 2 h showed advantage in reducing processing time. A preferential eugenol impregnation was observed due to thermodynamic interactions and mass transfer phenomena. Thermal and mechanical properties of LLDPE films remained stable after high pressure processing. Industrial relevance The development of innovative technologies for active packaging systems has attracted the interest of food, pharmaceutical, and chemical industries. The consumer's demand for products with low healthy risk makes the CEO an advantageous active agent for packaging development purposes, besides possessing strong antimicrobial and antioxidant activities. The employment of high pressure CO2 allowed a homogeneous CEO impregnation in LLDPE films without damaging mechanical and thermal properties of the polymer matrix, which is important for industrial applications. The CEO-impregnated LLDPE films have potential use in antimicrobial and antioxidant packaging systems.

The Effect of High Pressure Techniques on the Stability of Anthocyanins in Fruit and Vegetables.

Anthocyanins are a group of phenolic compounds responsible for red, blue and violet colouration of many fruits, vegetables and flowers. The high content of these pigments is important as it influences directly their health promoting properties as well as the sensory quality of the product; however they are prone to degradation by, inter alia, elevated temperature and tissue enzymes. The traditional thermal methods of food preservation cause significant losses of these pigments. Thus, novel non-thermal techniques such as high pressure processing, high pressure carbon dioxide and high pressure homogenization are under consideration. In this review, the authors attempted to summarize the current knowledge of the impact of high pressure techniques on the stability of anthocyanins during processing and storage of fruit and vegetable products. Furthermore, the effect of the activity of enzymes involved in the degradation of these compounds has been described. The conclusions including comparisons of pressure-based methods with high temperature preservation techniques were presented.

Improved Understanding of CO2–Water Pretreatment of Guayule Biomass by High Solids Ratio Experiments, Rapid Physical Expansion, and Examination of Textural Properties

In this work, we provide a systematic study of CO2–water pretreatment of guayule biomass to optimize the residual ground bagasse from natural rubber extraction for hydrolysis and fermentation. Guayule biomass is mixed with water then loaded into a 250 mL reactor with exposure to a biphasic environment consisting of a CO2-rich vapor phase and water-rich liquid phase. The pressure is then rapidly released for a “physical expansion” effect. The pretreated biomass is enzymatically hydrolyzed, and the sugar concentration in hydrolysate is measured. Experimental runs are conducted in the temperature range of 145 to 210 °C and pressure range of 3.4 to 34 MPa. The solids ratio (dry solids mass/water mass) is between 0.17 and 1.7. The packing density is between 0.03 and 0.2 g of biomass per cm3 of the reactor, and the holding time ranges from 20 to 840 min. A 4-fold increase in the reactor volume is performed and optimized with a 1-L vessel. High-pressure carbon dioxide–water pretreatment increases surface area of...

Valuable new platform chemicals obtained by valorisation of a model succinic acid and bio-succinic acid with an ionic liquid and high-pressure carbon dioxide

Biomass and catalysis form a bridge between bio-based industry and the current process technology.

Porous 3D polymers for high pressure methane storage and carbon dioxide capture

Porous 3D polymers, fabricated using multidentate monomers, efficiently adsorb CO2 and CH4 up to 180 bar.

CO2 Induced Foaming Behavior of Polystyrene near the Glass Transition

This paper examines the effect of high-pressure carbon dioxide on the foaming process in polystyrene near the glass transition temperature and the foaming was studied using cylindrical high-pressure view cell with two optical windows. This technique has potential applications in the shape foaming of polymers at lower temperatures, dye impregnation, and the foaming of polystyrene. Three sets of experiments were carried out at operating temperatures of 50, 70, and 100°C, each over a range of pressures from 24 to 120 bar. Foaming was not observed when the polymer was initially at conditions below Tg but was observed above Tg. The nucleation appeared to occur randomly leading to subsequent bubble growth from these sites, with maximum radius of 0.02–0.83 mm. Three models were applied on the foaming experimental data. Variable diffusivity and viscosity model (Model C) was applied to assess the experimental data with the WLF equation. The model shows very good agreement by using realistic parameter values. The expansion occurs by diffusion of a dissolved gas from the supersaturated polymer envelope into the bubble.

Theoretical predictions suggest carbon dioxide phases III and VII are identical.

Solid carbon dioxide exhibits a rich phase diagram at high pressures. Metastable phase III is formed by compressing dry ice above ∼10-12 GPa. Phase VII occurs at similar pressures but higher temperatures, and its stability region is disconnected from III on the phase diagram. Comparison of large-basis-set quasi-harmonic second-order Møller-Plesset perturbation theory calculations and experiment suggests that the long-accepted structure of phase III is problematic. The experimental phase III and VII structures both relax to the same phase VII structure. Furthermore, Raman spectra predicted for phase VII are in good agreement with those observed experimentally for both phase III and VII, while those for the purported phase III structure agree poorly with experimental observations. Crystal structure prediction is employed to search for other potential structures which might account for phase III, but none are found. Together, these results suggest that phases III and VII are likely identical.

Chemo-Enzymatic Synthesis and Characterization of Renewable Thermoplastic and Thermoset Isocyanate-Free Poly(hydroxy)urethanes from Ferulic Acid Derivatives

This study presents the syntheses and characterization of renewable nonisocyanate polyurethanes (NIPUs) from a new family of aromatic C5-cyclocarbonate precursors with different functionalities obtained from nontoxic ferulic acid derivatives by glycidylation and carbonation under high carbon dioxide pressure. Depending on the functionality, linear NIPU chains (thermoplastics) or cross-linked NIPU networks (thermosets) have been obtained. The thermoplastic NIPUs molar masses were determined using SEC and 1H NMR. The thermal and thermo-mechanical properties of the NIPUs were assessed by DSC, DMA (for thermosets), and TGA to determine the influence of the NIPU chemical structure on its properties. The range of Tg obtained (17–72 °C) was efficiently correlated with the degree of freedom and the molar mass of the NIPU repeat unit.