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•Continuous esterification of oleic acid and supercritical methanol with γ-Al2O3.•Both the global and Eley-Rideal mechanism-based kinetics models were established.•Effects of impurity ...water and pressure on biodiesel conversion were examined.•Slow deactivation of catalyst was observed under supercritical condition for 30 h.
A continuous pack-bed reactor experimental system was employed to investigate the heterogeneous catalytic esterification of oleic acid and sub/supercritical methanol with γ-Al2O3 as the catalyst. The experiment conditions were pressure of 10–20 MPa, temperature of 175–325 °C, residence time of 0.2–7 min and methanol/oil molar ratio of 20:1. A global one-step second order reversible kinetic model and a three-step Eley-Rideal mechanism model were proposed. The influence of impurity water and reaction pressure on the supercritical heterogeneous catalytic reaction were examined, and the stability of γ-Al2O3 under supercritical conditions was also evaluated. It was found that γ-Al2O3 showed excellent catalytic performance in both subcritical and supercritical processes, promoting theoretical maximum biodiesel yield at 20 MPa, 275 °C in 1 min. The impurity water hindered the conversion of biodiesel due to its negative influence on both the esterification reaction and the catalyst. Finally, the stability of γ-Al2O3 was tested under supercritical condition for 30 h.
Aurantiochytrium
sp. is an emerging alternative source of polyunsaturated fatty acids (PUFAs), docosahexaenoic acid (DHA), and squalene, playing an important role in the phasing out of traditional ...fish sources for these compounds. Novel lipid extraction techniques with a focus on sustainability and low environmental footprint are being developed for this organism, but the exploration of other added-value compounds within it is still very limited. In this work, a combination of novel green extraction techniques (high hydrostatic pressure extraction (HPE) and supercritical fluid extraction (SFE)) and traditional techniques (organic solvent Soxhlet extraction and hydrodistillation (HD)) was used to obtain lipophilic extracts of
Aurantiochytrium
sp., which were then screened for antioxidant (DPPH radical reduction capacity and ferric-reducing antioxidant potential (FRAP) assays), lipid oxidation protection, antimicrobial, anti-aging enzyme inhibition (collagenase, elastase and hyaluronidase), and anti-inflammatory (inhibition of NO production) activities. The screening revealed promising extracts in nearly all categories of biological activity tested, with only the enzymatic inhibition being low in all extracts. Powerful lipid oxidation protection and anti-inflammatory activity were observed in most SFE samples. Ethanolic HPEs inhibited both lipid oxidation reactions and microbial growth. The HD extract demonstrated high antioxidant, antimicrobial, and anti-inflammatory activities making, it a major contender for further studies aiming at the valorization of
Aurantiochytrium
sp. Taken together, this study presents compelling evidence of the bioactive potential of
Aurantiochytrium
sp. and encourages further exploration of its composition and application.
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•A well-regulated, stable and incessant nanonization method was demonstrated.•The critical conditions of SC-CO2 were consistent and resulting in desired yields.•Altered physical state ...of lonidamine resulted in the solubility improvement.•Improved solubility enhanced the anti-tumor effects of lonidamine after nanonization.
Despite the significant advancements in the pharmaceutical manufacturing process, the aqueous solubility of most of the potent drugs has remained as an unresolved problem during the formulation development and drug delivery processes. To address this critical issue, we modified the continuous-rapid expansion of supercritical solution (RESS-C) process, which is incessant, stable and well-regulated. Initially, the solubility of lonidamine (LND) in supercritical carbon dioxide (SC-CO2) was tested using a static analytical method at altered critical conditions (T: 308.15-328.15K, P: 10.0-30.0MPa). Under optimized conditions (LND conc.- 0.5% (w/v), flow rate- 1.0mL/min, T- 328.15K, P- 20.0MPa and CO2 flow rate- 30.0g/min), the modified RESS-C process resulted in nano-sized spheres with a smooth surface and a narrow particle size distribution. Further, the crystal properties of the samples and their molecular interactions were elucidated. The altered physical state of RESS-C processed LND from crystalline to amorphous resulted in the solubility improvement and also enhanced the in vitro antiproliferative effects compared to the unprocessed LND, demonstrating the potential of the modified RESS-C process in improving the bioavailability of poorly water-soluble drugs.
Pulicaria jaubertii
(PJ) is a fragrant herb traditionally used in medication and as a food seasoning. To date, there are no studies on the use of supercritical fluids extraction with carbon dioxide ...(SFE-CO
2
) on PJ. This study evaluates and compares the Total phenolic contents (TPC), antioxidant activity by DPPH
·
, antioxidant capacity by ABTS
·+
, and antibacterial activities of the PJ extract. Extraction was done by using two different methods namely, SFE-CO
2
with 10% ethanol (EtOH) as a co-solvent and conventional extraction by Shaking (Sh) with two solvents (EtOH and water) with different concentrations (100, 70, 50, 30 and 0% v/v). The highest extraction yield and antioxidant capacity were obtained by Sh-EtOH 50% 13.9% and 91.24 Trolox equivalents per g dry extract (mg TE/g DE) respectively. The extract obtained by Sh-EtOH 70% represented the highest TPC and antioxidant inhibition values (899.02 mg gallic acid equivalents (GAE)/g DE and 76.93%) respectively. The SFE-CO
2
extract has significantly greater antimicrobial activity and is more effective against Gram-positive bacteria. The most sensitive bacterium was
B. subtilis
, while the most resistant bacterium was
P. aeruginosa
. The optimum values of minimal inhibitory concentration (MIC) and minimal bactericidal concentration (MBC) against
B. subtilis
were noticed in SFE-CO
2
extract (0.4 mg/ml) for both. Overall, the results of this study indicated that PJ is a good source of TPC, antioxidants, and antibacterial compounds.
•A visualization study on rapid evaporation of supercritical liquid is performed.•Transient heat transfer is studied during rapid depressurization process.•The temperature and NEF are discussed from ...both experimental and numerical methods.
A combination of experimental studies and numerical simulations is employed to probe into the transient heat transfer phenomenon during rapid depressurization of supercritical fluid in a cylindrical vessel connected to atmosphere via a sudden valve on the top. The effects of initial conditions on heat transfer characteristics are studied, and the morphological characteristics of supercritical fluid are analyzed. Results show: (i) there is a strong re-circulation inside the supercritical fluid with a sudden pressure drop. The heat transfer process is divided into four stages: the initial depressurization stage, the rapid evaporation stage, the nucleate boiling stage and the surface evaporation stage; (ii) under the subcritical state, a higher temperature contributes to a faster temperature drop rate and a shorter fast evaporation time. Moreover, a higher initial pressure leads to a lower equilibrium temperature and a shorter time it takes to reach the equilibrium temperature; (iii) differences are presented in terms of the effect of initial pressure in subcritical and supercritical zones on temperature drop rate with a turn near the critical point. A higher initial pressure gives rise to a higher equilibrium temperature, a slower temperature drop rate and the gradual increasing fast evaporation time; (iv) the experimental data are in good agreement with the calculated results, with a maximum error of 10%.
•The theory of pseudoboiling is used to divide a gas chiller into a three sections: a pre-cooler, a condenser and a super-cooler.•The effect of variable heat capacity on required heat exchange area, ...effectiveness and entropy generation is shown.•The effect of variability of the heat transfer coefficient is analysed.•The propagation of uncertainty in heat transfer rate predictions into effectiveness and required heat exchange area is investigated.
Supercritical CO2 is used as a work fluid in both heat pump and power cycles. As a fluid at supercritical pressure is heated or cooled, it may undergo a smooth transition from a liquid-like state to a gas-like state or vice versa. This transition, during which the thermophysical properties vary sharply with temperature, can be referred to as pseudo- boiling or condensation. Using both analytical and numerical methods, it is shown that pseudoboiling theory helps to understand how the unique heat transfer characteristics of a supercritical fluid affect heat exchanger performance and design, in particular a gas chiller. Due to pseudo-condensation, classical approaches such as the ε−NTU and LMTD methods fail when rating or designing a sCO2 gas chiller. Using the heat of pseudo-condensation, the heat exchanger can be regarded to consist of a pre-cooler, condenser and a super-cooler. By further dividing the pre-cooler and super-cooler into two parts and subsequently applying the ε−NTU method per part yields very good results with respect to both the prediction of required size and entropy generation for various operating parameters. The influence of pseudo-condensation is reduced at higher pressures and is negligible when the structural energy required for the transition from liquid-like to a gas-like state is smaller than the required thermal energy required. It is shown that the local effectiveness of the condenser part is reduced (more so than the other parts) when the heat capacity ratio RC is varied from unity to less than unity, leading to enhanced irreversibility due to pseudo-condensation. Furthermore, the enhanced and deteriorated heat transfer regime (such as when a sCO2 downward flow is cooled) lead to significantly different required heat exchanger sizes. Finally, through the use of Monte Carlo simulations, it shown that the uncertainty of a Nusselt correlation complicates designing heat exchangers in which pseudo-condensation occurs. The simulations show that heat exchangers should be 50% larger than the size that is predicted using a Nusselt correlation if the design performance is to be ensured.
With the increase of people's awareness of food safety, it is crucial to find natural and green antimicrobial agents to replace traditional antimicrobial agents. Essential oils of spices (SEOs) are ...low toxicity or nontoxic, which exhibited antioxidants and antimicrobial activity according to many in vitro and in situ experiments. Spices are widely available and low cost as a plant raw material for the extraction of SEOs. This review summarized highly efficient extraction techniques for SEOs, such as physical field assisted extraction technology, supercritical fluid extraction, and biological-based techniques. Furthermore, purification of SEOs and components were also recapitulated. Purification techniques of SEOs improve their utilization value due to the increased content of bioactive components. Finally, the review concentrated on the applications of SEOs in food industry, including food preservation, food active packaging by means of films or coatings, antioxidant properties. In addition, addressing the problem of unstability of SEOs and its role to inhibit the pathogenic bacteria, the encapsulation of SEOs for use in the food industrial sectors reduces the safety risk to human health.
Supercritical fluids find use in various areas in oil and gas production operations due to their unique properties. Supercritical CO2 (sc-CO2) with its reduced viscosity, increased diffusivity, and ...liquid like density, is attractive for enhanced hydrocarbon recovery, shale gas fracturing and drilling (especially in underbalanced condition). Apart from enhanced hydrocarbon recovery CO2 injection is also desirable due to associated CO2 storage through various trapping mechanisms. CO2-EOR/EGR and storage processes are affected by coupled geochemical, petrophysical and geomechanical alterations due interaction of sc-CO2 with reservoir rock/fluids Along with diffusion/dispersion of sc-CO2 in the fluid filled pore spaces. CO2-monitoring combined with lifecycle analysis can help to ensure safety and optimize the CO2-EOR/storage project, considering the environment. However, many technical, financial and policy challenges need to be overcome to realize the success of the CO2-EOR/storage project and achieve carbon neutrality. This review paper discusses such challenges, the current mitigation practice, gaps and future direction of research. This holistic review would help gain insights into the sc-CO2-EOR/storage mechanisms, selection criteria, various limitations, mitigation and optimizations while applying the method for unconventional reservoirs with heterogeneity and varying fluid properties.
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•A review of sc-CO2 and other fluids for improved hydrocarbon production.•Thickeners reduce sc-CO2 fluid mobility, improving the sweep efficiency.•CO2-philic and phobic groups improve CO2 solubility and viscosity, respectively.•Reduced formation breakdown and increased fracture propagation with sc-CO2 fluid.•Higher CO2 adsorption for storage and enhanced erosion for drilling operations.
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•A combined process for bioactive extraction and preservation was proposed.•High pressure and temperature extraction allowed spent coffee grounds valorization.•Extract was rich in ...polyphenols and caffeine exhibiting high scavenging activity.•Produced loaded liposomes showed small size and high encapsulation efficiency.
Valorization of agro-industrial waste by the extraction of bioactive molecules and their activity preservation by encapsulation is an open topic in process engineering. In this work, a combined approach for the recovery of antioxidants from spent coffee grounds by High Pressure and Temperature Extraction and the entrapment of extract into liposomes using the Supercritical assisted Liposome formation process was proposed. High Pressure and Temperature Extraction showed that high extraction performances (43 ± 2.3 mg Caffeic Acid Equivalents /gDried Spent Coffee Grounds, 59 ± 3 μg Trolox Equivalents/L extract) can be obtained working under inert atmosphere at 150 °C, 60 min using ethanol 54 % (v/v) as solvent. For extract preservation, liposomes were produced by Supercritical assisted liposome formation, investigating different operating pressures and varying the extract cargo into liposomes. Results indicated that 100 bar as operative pressure and 18 mg Caffeic Acid Equivalents /g liposomes as total polyphenol loading allowed to obtain high encapsulation efficiency (89 %), small liposome size (about 200 nm) and without significant reduction of loading antioxidant activity (7%).
Mandelic acid and its derivatives are important chiral analogs which are widely used in the pharmaceutical synthetic industry. The present study investigated the enantiomeric separation of six ...mandelic acids (mandelic acid, 2‐chloromandelic acid, 3‐chloromandelic acid, 4‐chloromandelic acid, 4‐bromomandelic acid, 4‐methoxymandelic acid) on the Chiralpak AD‐3 column by supercritical fluid chromatography. The influences of volume fraction of trifluoroacetic acid, type and percentage of modifier, column temperature, and backpressure on the separation efficiency were investigated. And the enantiomer elution order was determined. The results show that, for a given modifier, the retention factor, the separation factor, and the separation resolution decreased gradually with increasing the volume ratio of the modifier. At the same volume ratio of modifier, the retention factor of the mandelic acid and its derivatives increased in the order of methanol, ethanol, and isopropanol, except 3‐chloromandelic acid. The separation factor and the separation resolution decreased with the increase of column temperature (below the temperature limit). The backpressure affected the enantioseparation process: As the backpressure increased, a corresponding decrease in retention factor was observed. Under the same chiral column conditions, the SFC method exhibited faster and more efficient separation with better enantioselectivity than the HPLC method.
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