Biodiesel production from supercritical carbon dioxide extracted Jatropha oil using subcritical hydrolysis and supercritical methylation

This study investigates supercritical carbon dioxide (SC-CO₂) extraction of triglycerides from powdered Jatropha curcas kernels followed by subcritical hydrolysis and supercritical methylation of the extracted SC-CO₂ oil to obtain a 98.5% purity level of biodiesel. Effects of the reaction temperature, the reaction time and the solvent to feed ratio on free fatty acids in the hydrolyzed oil and fatty acid esters in the methylated oil via two experimental designs were also examined. Supercritical methylation of the hydrolyzed oil following subcritical hydrolysis of the SC-CO₂ extract yielded a methylation reaction conversion of 99%. The activation energy of hydrolysis and trans-esterified reactions were 68.5 and 45.2 kJ/mole, respectively. This study demonstrates that supercritical methylation preceded by subcritical hydrolysis of the SC-CO₂ oil is a feasible two-step process in producing biodiesel from powdered Jatropha kernels.     

Optimization of the supercritical fluid coextraction of oil and diterpenes from spent coffee grounds using experimental design and response surface methodology

The reported work aimed at the optimization of operating conditions of the supercritical fluid extraction (SFE) of spent coffee grounds (SCG) using pure or modified CO₂, with particular emphasis on oil enrichment with diterpenes like kahweol, cafestol and 16-O-methylcafestol. The analysis comprised the application of Box–Behnken design of experiments and response surface methodology, and involved three operating variables: pressure (140–190 bar), temperature (40–70 °C) and cosolvent (ethanol) addition (0–5 wt.%). The best conditions to maximize total extraction yield are 190 bar/55 °C/5 wt.% EtOH, leading to 11.97% (g_oil/100 g_SCG). In terms of the concentration of diterpenic compounds in the supercritical extracts, the best operating conditions are 140 bar/40 °C/0 wt.% EtOH, providing 102.90 mg g⁻¹_oil. The measurement of extraction curves near optimized conditions (140 bar/55 °C/0 wt.% EtOH and 190 bar/55 °C/0 wt.% EtOH) confirmed the trends of the statistical analysis and revealed that SFE enhances diterpenes concentration by 212–410% at the expenses of reducing the extraction yield between 39% and 79% in comparison to n-hexane extraction.     

Continuous extraction of glycerol acetates from their mixture using supercritical carbon dioxide

Supercritical carbon dioxide was used for partially selective extraction of triacetin from a mixture of triacetin, diacetin, and monoacetin with a molar ratio of 1:2:1. The extraction was carried out in two stages. In the first stage, a central composite design was used to optimize the four variables of pressure, temperature, liquid CO₂ flow rate, and extraction time at three levels using a semi-continuous, supercritical carbon dioxide extraction setup. The composition of the extract under the predicted optimum conditions (i.e., 109 bar, 56 °C, 0.86 mL min⁻¹, and 61 min) was about 69% triacetin accompanied by only 30% diacetin and no detectable monoacetin. In the second stage, the effect of the two factors, pressure (100, 109, and 140 bar) and liquid CO₂ flow rates of 0.86 and 1.5 mL min⁻¹ measured at average laboratory temperature (27 °C) and pressure (0.89 bar), were studied using a continuous, supercritical carbon dioxide fractionation setup equipped with a glass-bead packed column kept under a thermal gradient of 56-70 °C. The experimental design was organized as a 3 × 2 general factorial design. Under the best conditions (i.e., 140 bar and 1.5 mL min⁻¹), the extraction yield of triacetin and diacetin were 41.8 and 3.0%, respectively, without any detectable monoacetin as verified by GC-FID.     

Supercritical carbon dioxide extraction of oil from Mexican chia seed (Salvia hispanica L.): Characterization and process optimization

Supercritical carbon dioxide (SC-CO₂) was employed to extract oil rich in omega-3 fatty acids (FAs) from chia seeds, and the physicochemical properties of the oil were determined. A central composite rotatable design was used to analyze the impact of temperature (40 °C, 60 °C and 80 °C), pressure (250 bar, 350 bar and 450 bar) and time (60 min, 150 min and 240 min) on oil extraction yield, and a response surface methodology (RSM) was applied. The extraction time and pressure had the greatest effects on oil. The highest oil yield was 92.8% after 300 min of extraction time at 450 bar. The FA composition varied depending on operating conditions but had a high content of α-linolenic acid (44.4-63.4%) and linoleic acid (19.6-35.0%). The rheological evaluation of the oils indicated a Newtonian behavior. The viscosity of the oil decreased with the increase in temperature following an Arrhenius-type relationship.     

Extraction of pomegranate seed oil using subcritical propane and supercritical carbon dioxide

Extraction of oil from pomegranate seeds as a waste product of the juice industry using supercritical carbon dioxide and subcritical propane was studied in this work. The influence of the main operating conditions of extraction, namely, the temperature and pressure of extraction on the oil extraction yield and the correspondent fatty acid profile were analyzed and reported here. Soxhlet extraction with n-hexane was done for comparison with supercritical extraction resulting in a maximum yield of oil of 22.31 wt %. Supercritical carbon dioxide and subcritical propane extracted up to 58.53% (corresponding to maximum yield of 13.06 wt %) and 76.73% (corresponding to maximum yield of 17.12 wt %) of the total amount of pomegranate seed oil as measured using Soxhlet extraction, respectively. Results indicated that the subcritical propane is a suitable and selective solvent for the extraction of the pomegranate seed oil in function of smaller times and pressures employed compared to carbon dioxide extraction. The fatty acid composition of the extracted oil showed the presence of fatty acids of C₁₆, C₁₈, C₂₀, C₂₂, and C₂₄ carbon chains. Punicic (C_18.3) was the major fatty acids and comprise up to 70% of the total fatty acid content of the extracted oil among all samples. Finally, Lack??s plug flow model as developed by Sovova was applied to both extraction systems and a good agreement with the experimental results was obtained.     

CO2 supercritical fluid extraction of Jordanian oil shale utilizing different co-solvents

In this study, extracting shale oil from Jordanian oil shale using supercritical fluid extraction has been investigated. Experimental data indicates that by using supercritical extraction with carbon dioxide, using co-solvents can be viable. A relatively high yield can be obtained at relatively moderate pressure. At the highest temperature and pressure of 450 °C and 3200 psi, respectively, and with hexane as a co-solvent, the highest yield obtained was 100 kg/ton of oil shale, which was at the highest temperature and pressure of 450 °C and 3200 psi, respectively, and with hexane as a co-solvent. Increasing both the operating pressure and temperature increases the oil yield. In the supercritical state, carbon dioxide along with other co-solvents, such as hexane and acetone, interact with the kerogen leading to the dissolution of fragments due to an increase in solubility and mass transfer.Increasing the particle size of oil shale for extraction decreases the oil yield. Most of the extracted oil obtained is saturated hydrocarbons, olefinic and a portion of aromatic hydrocarbons. As the extraction temperature increases, the production of low-molecular weight compounds increases.     

Extraction of oil from chia seeds with supercritical CO2

Chia (Salvia Hispanic, L.) is a crop that was used as food, medicine and paints by the Aztec Indians in Mexico before 1492, and now has a promissory future in several countries. Chia seeds oil is rich in polyunsaturated fatty acids, particularly omega-3 linolenic acid (54-67%) and omega-6 linoleic acid (12-21%) which pose great benefits for human and animal health.The oil extraction from Chia seeds using supercritical CO₂ seems to be a good alternative because it operates at low temperature with good mass-transfer rates and with no solvent residual in the final product.The objective of this work is to evaluate the extraction yield of oil from chia seeds and the concentration of omega-3 and omega-6 acids using supercritical extraction with CO₂ at three pressures: 136, 272, and 408 bar, and three temperatures: 40, 60, and 80 °C.     

Comparison of different extraction methods for the extraction of major bioactive flavonoid compounds from spearmint (Mentha spicata L.) leaves

Different bioactive flavonoid compounds including catechin, epicatechin, rutin, myricetin, luteolin, apigenin and naringenin were obtained from spearmint (Mentha spicata L.) leaves by using conventional soxhlet extraction (CSE) and supercritical carbon dioxide (SC-CO₂) extraction at different extraction schemes and parameters. The effect of different parameters such as temperature (40, 50 and 60 °C), pressure (100, 200 and 300 bar) and dynamic extraction time (30, 60 and 90 min) on the supercritical carbon dioxide (SC-CO₂) extraction of spearmint flavonoids was investigated using full factorial arrangement in a completely randomized design (CRD). The extracts of spearmint leaves obtained by CSE and optimal SC-CO₂ extraction conditions were further analyzed by high performance liquid chromatography (HPLC) to identify and quantify major bioactive flavonoid compounds profile. Comparable results were obtained by optimum SC-CO₂ extraction condition (60 °C, 200 bar, 60 min) and 70% ethanol soxhlet extraction. As revealed by the results, soxhlet extraction had a higher crude extract yield (257.67 mg/g) comparing to the SC-CO₂ extraction (60.57 mg/g). Supercritical carbon dioxide extract (optimum condition) was found to have more main flavonoid compounds (seven bioactive flavonoids) with high concentration comparing to the 70% ethanol soxhlet extraction (five bioactive flavonoids). Therefore, SC-CO₂ extraction is considered as an alternative process compared to the CSE for obtaining the bioactive flavonoid compounds with high concentration from spearmint leaves.     

Supercritical CO2 extraction of lipids and astaxanthin from Brazilian redspotted shrimp waste (Farfantepenaeus paulensis)

Brazilian redspotted shrimp (Farfantepenaeus paulensis) waste is an important source of carotenoids such as astaxanthin and lipids with a high ω−3 fatty acids content, mainly docosahexaenoic acid (DHA) and eicosapentaenoic acid (EPA). In order to establish an efficient and environmental friendly recovery process, the lipids and astaxanthin were extracted from the freeze-dried redspotted shrimp waste (including head, tail and shell) using supercritical carbon dioxide. The effects of the extraction conditions of pressure (200-400 bar) and temperature (40-60 °C) on the global yield (X₀), astaxanthin extraction yield and astaxanthin concentration in the extract were evaluated. It was found that the pressure and temperature showed a very low significant effect on the lipid extraction yield using supercritical CO₂. In comparison with lipid extraction by solvents, maximum efficiency of supercritical fluid extraction achieved 64% of hexane extraction yield. On the other hand, temperature and pressure had significant effects on astaxanthin extraction yield. Thegreatest amount of extract was obtained at 43 °C and 370 bar, with 39% of recovery.     

Supercritical CO2 extraction of oil, carotenoids, squalene and sterols from lotus (Nelumbo nucifera Gaertn) bee pollen

The high-quality oil, abundant in carotenoids, squalene and sterols (mainly consisting of campesterol, stigmasterol, β-sitosterol and β-amyrin), was extracted by supercritical CO₂ from lotus bee pollen for its potential nutraceutical use. The effects of extraction pressure and temperature on the yields and the compositions of the extracts were investigated by using a two-factor central composite rotatable design experiment. ANOVA for response surface model demonstrated that the data were adequately fitted into four polynomial models. The yields of the oil, carotenoids, squalene and sterols were significantly influenced by the experimental variables. It was predicted that maximum oil yield obtained at the extraction pressure of 38.2 MPa and temperature of 49.7 °C contained the maximum amount of carotenoids, squalene and sterols. GC-FID analysis of the fatty acid composition of lotus bee pollen oil showed that polyunsaturated fatty acids accounted for approximately 22% of the total fatty acids.     

Supercritical carbon dioxide fractionation of fish oil fatty acid ethyl esters

Fractionation of fish oil fatty acid ethyl esters was investigated with the aim of obtaining a lipid fraction enriched in ω-3 fatty acids and with a suitable EPA/DHA ratio. The results obtained highlight the possibility of modifying the original fatty acid ethyl esters concentration by optimizing the extraction conditions in terms of pressure, temperature, and supercritical carbon dioxide flow rate. Supercritical fluid fractionation (SFF) appears to be a useful processing technique for changing the composition of lipids in order to obtain high value functional products. The use of proper fractionation temperatures and pressures along the column influenced the solvent-to-feed ratio to obtain fractions with suitable composition for market requirements.     

Supercritical CO2 extraction of omega-3 rich oil from Sacha inchi (Plukenetia volubilis L.) seeds

Supercritical carbon dioxide (SC-CO₂) was employed to extract omega-3 rich oil from Sacha inchi (Plukenetia volubilis L.) seeds and partially defatted cake. For ground seeds, the supercritical extraction was carried out at temperatures of 40, 50 and 60 °C and pressures of 300 and 400 bar, and for the cold pressed partially defatted cake, the extraction was carried out with 300 bar at 40 °C and with 400 bar at 60 °C. The global extraction yields (X₀), oil solubility, fatty acid composition of the oil and tocopherol content were determined. The seed samples used in this work contained 54.3% oil, of which 50.5% was linoleinc acid (ω-3). The maximum extraction recovery for the seeds as 92% at 400 bar and 60 °C, but on one occasion a recovery of 99.1% oil was obtained when cold pressed extraction was employed, followed by supercritical extraction at 400 bar and 60 °C. A high tocopherol content of about 2–3 g/kg of oil was obtained.     

Supercritical fluids extraction and anti-solvent purification of carotenoids from microalgae and associated bioactivity

This study investigated co-solvent modified supercritical carbon dioxide extraction of lipids and carotenoids from the microalgal species of Nannochloropsis oculata. Supercritical carbon dioxide (SCCO₂) anti-solvent precipitation of carotenoids from the extracts following purification of Zeaxanthin was also examined. Continuous modification by ethanol of supercritical carbon dioxide extractions showed that the addition ratio was important for extraction efficiency of lipids and carotenoids. SCCO₂ extraction at 350 bar, 323 K and 16.7 wt% of ethanol addition yielded 239.7 mg of triglycerides and 7.61 mg of carotenoids per gram extract with a total yield of 15.5%. SCCO₂ anti-solvent experiments showed that the content of Zeaxanthin in the precipitate was greater than that in the fraction of normal phase column chromatography. The purest Zeaxanthin (93.8%) was then successfully isolated from the purified fraction by using a reverse-phase HPLC column chromatography. Rat macrophages treated by ultra-sonicated water extracts of the SCCO₂ defatted algae showed a positive phagocytotic activity.     

Extraction of sesame seed (Sesamun indicum L.) oil using compressed propane and supercritical carbon dioxide

This work is aimed to investigate the extraction of sesame seed (Sesamun indicum L.) oil using supercritical carbon dioxide and compressed propane as solvents. The extractions were performed in a laboratory scale unit in a temperature and pressure range of 313-333 K and 19-25 MPa for carbon dioxide and 303-333 K and 8-12 MPa for propane extractions, respectively. A 2² factorial experimental design with three replicates of the central point was adopted to organize the data collection for both solvents. The results indicated that solvent and density were important variables for the CO₂ extraction, while temperature is the most important variable for the extraction yield with propane. The extraction with propane was much faster than that with carbon dioxide due to the fact that propane is a better solvent for vegetable oils compared to carbon dioxide. On the other hand, characteristics of extracted oil, its oxidative stability determined by DSC and chemical profile of constituent fatty acids determined by gas chromatography, were similar to both solvents. The mathematical modeling of the extraction kinetics using a second order kinetic presented good results for the extraction with both solvents.     

Supercritical fluid extraction from dried banana peel (Musa spp., genomic group AAB): Extraction yield, mathematical modeling, economical analysis and phase equilibria

Supercritical fluid extraction from dried banana peel (Musa spp., subgroup Prata, genomic group AAB, popularly known in Brazil as Enxerto) was studied. The aspects investigated were: overall extraction curve (OEC), mass transfer modeling of the yield curves, economical analysis of the process and phase equilibrium data for the pseudo-ternary system of banana peel extract, carbon dioxide and ethanol. The extraction operating conditions evaluated were: pressure ranging from 100 bar to 300 bar, temperature from 40 to 50 °C and constant solvent flow rate of 5.0 gCO₂/min. Experimental extraction data were correlated using three kinetic models based on mass transfer equations (logistic, diffusion and Esquível models). Phase equilibrium measurements were performed using pressure from 64.9 bar to 239.9 bar and mass fraction of supercritical extract from 0.52 to 3.55 wt%. Yield results ranged from 0.6 to 6.9% d.b. (dry basis). The lowest deviation between experimental and correlated data was obtained by the Logistic model, except for the curve at 300 bar and 40 °C which was best represented by the Esquível model. The economical analysis identified the possibility to apply the supercritical fluids to obtain extracts from banana peel in an industrial scale. Phase equilibrium for the supercritical extract from banana peel with carbon dioxide modified by ethanol exhibited liquid-liquid, vapor-liquid (bubble point) and vapor-liquid-liquid phase transitions. A crossover phenomenon for the systems evaluated was observed for pressures between 200 bar and 240 bar, for both groups of assays, i.e., supercritical extraction and phase equilibrium.     

Supercritical carbon dioxide extraction of triglycerides from Jatropha curcas L. seeds

This study examines the effects of pressure, temperature and solvent to solid ratio (SSR) on extraction efficiency of triglycerides from powdered Jatropha seeds by using supercritical carbon dioxide extraction. Supercritical extractions were designed for pressures ranging from 250 to 350 bar, temperatures ranging from 313 to 333 K and SSR values ranging from 65:1 to 125:1. All values were selected using response surface methodology in order to determine their effects on the concentration of triglycerides from the extracted oil. Using 3750 g of carbon dioxide over 5 h, a supercritical carbon dioxide extraction (at 350 bar, 333 K and an SSR value of 125:1) yielded 43.51% oil. The concentration and extraction efficiency (i.e. recovery) of triglycerides in the extract reached 657.1 mg/g and 97.62%, respectively. Changes in pressure presented more effective in increasing the recovery of triglycerides, but both temperature and the SSR value are important in obtaining high concentration of triglycerides from the Jatropha seeds that are useful for biodiesel materials.     

Trigonella foenum-graecum L. Seed Oil Obtained by Supercritical CO2 Extraction

Supercritical CO₂ extraction (SC-CO₂) of fenugreek (Trigonella foenum-graecum L.) seed oil and its chemical composition and antioxidant activity were investigated. A central composite design combined with response surface methodology was used to study extraction conditions including pressure, temperature, and time. The optimum extraction conditions were 28.5?MPa extraction pressure, 41?°C extraction temperature, and 118?min extraction time, where 3.78?% yield was predicted. Fenugreek seed oil extracted under optimum conditions by SC-CO₂ was mainly composed of 28.3?% C18:3, 33.45?% C18:2, 9.89?% C16, 8.1?% C18:1, 3.7?% C18, 0.71?% C20, and 0.61?% C22. The fenugreek oil was rich in unsaturated fatty acids (nearly 70?% of the total fatty acids), and polyunsaturated fatty acids accounted for 61.42?% (mass percentage) of the total amount. The 2,2-diphenyl-1-picrylhydrazyl radical-scavenging activity increased from 12.5 to 88.4?% when the concentration was increased from 1 to 12?mg/ml. The reducing power of the seed oil was concentration-dependent. The antioxidant activity of the supercritical fluid extraction extract was superior to those obtained by Soxhlet extraction.     

Extraktion von Milchfett mit überkritischem Kohlendioxid

Extraction of Milk Fat with Supercritical Carbon Dioxide In parallel with fractionation based on crystallization, studies have been made in recent years on milk fat fractionation with supercritical carbon dioxide. This means that the fat is chiefly extracted on the basis of molecular size. The extraction experiments were carried out using a pilot plant extraction apparatus. The milk fat was extracted in 4 or 2 stages. The melting properties of extracts are explained by the compositions of fatty acids and triacylglycerols. The percentages of short chain fatty acids C4–C10 becomes smaller as the extractio proceeds. The percentage of palmitic acid remains virtually unchanged at all stages of the extraction. The percentages of C 18 fatty acids, stearic and oleic acids increase as the extraction proceeds. Cholesterol and aroma compounds of milk fat were clearly enriched in the first extract. Supercritical extraction opens up some new potential for milk fat technology and for the food industry using milk fat. At this stage it wold seem especially interesting to study the possible uses of extracts rich in aroma.     

Aromatic gas oil cracking under realistic FCC conditions in a microriser reactor

A paraffinic hydrowax feed spiked with naphthalene, anthracene, and phenanthrene was cracked in a once-through microriser reactor at 575 °C and with a catalyst-to-oil (CTO) ratio of 4.8 g_cat g_oil⁻¹. The conversion by cracking reactions is limited to the paraffinic fraction of the feed and the alkyl groups associated with the benzene ring in aromatic compounds; the aromatic probes did not crack under the applied conditions, and in fact an additional amount of naphthalene was formed by complex dealkylation and hydrogen transfer reactions. The ‘uncrackabilty’ of aromatics was directly demonstrated by processing an aromatic gas oil, containing 33.3 wt% aromatics. Experiments were performed with residence times between 0.05 and 8.2 s, keeping the temperature (525 °C) and CTO ratio (5.5 g_cat g_oil⁻¹) constant. The data was interpreted with a simplified first-order five-lump kinetic model, where approximately 19 wt% of the feed was found to be uncrackable. HCO (feedstock) conversion took mainly place during the first two seconds and coke was only formed during the first 50 ms of catalyst-oil contact. Gasoline was not overcracked to gas. Approximately 50 wt% of the LCO fraction was formed during this 50 ms and did not change thereafter.     

Continuous production of soybean biodiesel with compressed ethanol in a microtube reactor

This work investigates the production of fatty acid ethyl esters (FAEEs) from the transesterification of soybean oil in supercritical ethanol in a continuous catalyst-free process. Experiments were performed in a microtube reactor in the temperature range of 523 K to 598 K, from 10 MPa to 20 MPa, varying the oil to ethanol molar ratio from 1:10 to 1:40, and evaluating the effects of addition of carbon dioxide as co-solvent. Results showed that ethyl esters yield obtained in the microtube reactor (inner diameter 0.76 mm) were higher than those obtained in a tubular reactor (inner diameter 3.2 mm) possibly due to improved mass-transfer conditions attained inside the microtube reactor. Non-negligible reaction yields (70 wt.%) were achieved along with low total decomposition of fatty acids (< 5.0 wt.%). It is shown that the use of carbon dioxide as co-solvent in the proposed microtube reactor did not significantly affect the ethyl esters yield within the experimental variable ranges investigated.