María José Cocero

Supercritical Fluid Extraction of Sunflower Seed Oil with CO2-Ethanol Mixtures

The effect of ethanol addition to supercritical carbon dioxide (SC-CO2), up to 20%, on sunflower seed oil extraction over the range of 150 to 350 bars and 42 to 80°C was studied. A nonrecirculating home-made bench-scale system was used as extraction equipment. The oil-SC-CO2-ethanol mixture was reduced to atmospheric pressure in a test tube, where two phases, oil and ethanol, were obtained and ethanol-saturated CO2 was liberated to the atmosphere. Results show that sunflower oil solubility in SC-CO2 greatly increases with addition of ethanol as entrainer over the whole range of pressure and temperature conditions. Some phospholipids are co-extracted at levels directly proportional to the added ethanol. Moreover, a large amount of phospholipids was recovered in the ethanolic phase. Acidity of the extracted oil with ethanol as entrainer was lower than that without alcohol. Part of the free fatty acids was found in the ethanolic phase.

Crystallization of β-carotene by a GAS process in batch Effect of operating conditions

Abstract β-carotene has been successfully recrystallized from ethyl acetate and dichloromethane solutions using carbon dioxide as antisolvent in a batch bench plant for GAS process. The aim of this work is to study the influence of operating variables (concentration, temperature, stirring rate and type of solvent) and the efficiency of the GAS process on final size of the crystals. Crystals smaller than 1 μm are obtained at temperature of 298 K, pressure of 5.8 MPa, from 1 g/l solutions and with a stirring rate of 25 Hz. GAS process yields trans isomer with high efficiency separation. Solubility of β-carotene in CO 2 plus ethyl acetate at different temperatures (298, 313 and 333 K) from 4.3 to 9.8 MPa were measured, values ranged between 0.45 ( P =7.2 MPa, T =333 K) and 0.010 g/l ( P =8.1 MPa, T =313 K). In addition, distribution and size of the crystals from raw and recrystallized β-carotene for the CO 2 –ethyl acetate system are studied.

Encapsulation and Co-Precipitation Processes with Supercritical Fluids: Applications with Essential Oils

Essential oils have important commercial applications as preservatives and flavours, and more recently as natu- ral antimicrobial agents. These applications require a suitable formulation constituted by biodegradable compounds that protect the essential oil from degradation and evaporation at the same time that allows for a sustained release. Microcap- sules of biopolymers loaded with essential oils meet these requirements. Such microcapsules can be prepared with differ- ent processes such as spray-drying, freeze-drying and coacervation, and supercritical fluids are an advantageous medium for this purpose. Some supercritical fluid-based precipitation processes have already been applied to produce these micro- capsules. Amongst them, the results obtained with Particles from Gas Saturated Solutions (PGSS), PGSS-drying and Con- centrated Powder Form (CPF) processes are particularly promising. Recent developments in the preparation of formula- tions with supercritical fluids include the preparation of liposomes and micelles, which can be suitable carriers for essen- tial oils.

Chemical recycling of polycarbonate in a semi-continuous lab-plant. A green route with methanol and methanol–water mixtures

Alkali-catalysed depolymerization of polycarbonate (PC) wastes by alcoholysis in supercritical or near critical conditions has been studied in order to recover the essential monomer bisphenol A (BPA) and dimethyl carbonate (DMC) as a valuable by-product. This work aims to study the continuous process and possible scale-up for decomposition of both commercial PC and PC plastic wastes using methanol as solvent/reagent and NaOH as alkali catalyst. Total depolymerization of PC has been achieved working at a temperature range of 75–180 °C and pressures from 2 to 25 MPa. The influence of operation conditions on product yield, selectivity and reaction rate has been studied, including temperature, pressure, methanol/cosolvent ratio and catalyst concentration. BPA yields of 80–90% (kg product/kg PC) were achieved with a further crystallization and separation of the final product, resulting in BPA pure crystals (99.9%). DMC yield reached 35% (kg DMC/kg PC) and was proved to be strongly dependent on pressure and methanol/H2O ratio. Non desired by-product yield was negligible when pure methanol was used as solvent and selectivity decreased with increasing methanol/H2O ratio.

The influence of the energy absorbed from microwave pretreatment on biogas production from secondary wastewater sludge

In this study, microwave treatment is analyzed as a way to accelerate the hydrolysis in anaerobic digestion of municipal wastewater sludge. The influence of the absorbed energy, power and athermal microwave effect on organic matter solubilization and biogas production has been studied. In addition, a novel method that considers the absorbed energy in the microwave system is proposed, in order to obtain comparable experimental results. The absorbed energy is calculated from an energy balance. The highest solubilization was achieved using 0.54 kJ/ml at 1000 W, where an increment of 7.1% was observed in methane production, compared to the untreated sample. Using a higher energy value (0.83 kJ/ml), methane production further increased (to 15.4%), but solubilization decreased. No power influence was found when 0.54 kJ/ml was applied at 1000, 600 and 440 W. Microwave heating was compared to conventional heating in two different experimental setups, providing similar methane yields in all cases.

Engineering in direct synthesis of hydrogen peroxide: targets, reactors and guidelines for operational conditions

The demand for hydrogen peroxide is booming since it is considered as one of the most environmentally friendly and versatile chemical oxidants available and has a wide range of applications. The annual market, close to 3000 kt per year being produced via the auto-oxidation process (with 2-ethyl anthraquinone (traditional) or amyl anthraquinone for mega-plants), is mostly supplied by the company Solvay (30%), followed by Evonik (20%) and Arkema (13%). Nevertheless, the dream of a direct synthesis process is close to a century old and it has gained momentum in research efforts during the last decade with more than 15 groups active in the world. In this review, we focus the discussion on the targets, e.g. plant tonnage, the reactors and the most feasible industrial operational conditions, based on our experience and point of view using the chemical engineering tools available. Thus, direct synthesis can be competitive when on-site production is required and capacities less than 10 kt per year are demanded. The total investment cost should be approximately 40.3 ± 12.1 MM

Supercritical extraction of unsaturated products. Degradation of β-carotene in supercritical extraction processes

(in 2012) for a 10 kt per year size process to be comparable to the traditional process in terms of costs. Moreover, all kinds of reactors used are hereby discussed emphasizing the pros and cons; the most common ones are batch and semi-continuous modes of operation. However, at the moment, demonstrations of continuous operations as well as carefully determined kinetics are needed in order to scale up the process. Finally, operational conditions, including the catalyst composition (active metal, oxidation state and support), promoters (halides and acids–pH–isoelectric point), solvents, pressure and temperature need to be carefully analysed. In our opinion, as we try to show here, H2O2 direct synthesis is a competitive process and is ready for larger scale demonstration. Also, more than a hundred patents within the area support this claim, although the barriers of technology demonstration and further licensing are still pending.

Oxidative stability of sunflower oil extracted with supercritical carbon dioxide

Abstract Supercritical carbon dioxide is a promising solvent for the extraction and crystallization processes of natural compounds, especially thermolabil compounds. It is recognized as exhibiting powerful advantages over conventional solvents. However, so far a crucial point has been ignored, the possible oxidation of unsaturated compounds due to the presence of oxygen in high purity carbon dioxide used in these processes. The highest purity grade of commercial carbon dioxide is ≈2 mg/l STP. Taking into account that the solubility of most natural compounds is ≤0.1%, this means that the oxygen/compound concentration ratio would be high. To test this drawback, the extraction of β-carotene with supercritical carbon dioxide was studied. The β-carotene solubility was found to be 3.8 mg/kg at 30 MPa and 40°C. Therefore, 263 kg of carbon dioxide would be needed to yield 1 g of β-carotene. That meant a 9 mol oxygen/mol β-carotene ratio. Results presented here suggest that β-carotene was oxidized during the extraction process.

Simultaneous and selective recovery of cellulose and hemicellulose fractions from wheat bran by supercritical water hydrolysis

Extraction of oilseeds with supercritical carbon dioxide (SC−CO2) is a promising technique to obtain vegetable oils. However, instability of such oils has been associated in the past with SC−CO2 extraction. The reasons underlying such instability were unclear. Results presented here suggest that oil instability may be related to the oxygen content of CO2. In fact, oil stability decreases sharply when refined oil (additive-free) is re-extracted with SC−CO2 and can be related to the oxygen content in the CO2. Never-theless, oil stability could be improved to the level of conventionally extracted oil by adding trace amounts of ascorbic acid.

Precipitation Processes with Supercritical Fluids : Patents Review

Supercritical water (SCW) has been demonstrated to be an excellent solvent and reaction medium to improve the cellulose hydrolysis selectivity by controlling the reaction time. In this study the conversion of wheat bran into soluble saccharides such as glucose, xylose and arabinose was analysed at 400 °C and 25 MPa with reaction times between 0.2 and 1 s. The process yield was evaluated for two different products: C-6 (glucose derived from cellulose) and C-5 sugars (saccharide derived from hemicellulose hydrolysis). The production of glycolaldehyde, furfural and 5-hydroxymethylfural (5-HMF) was analysed as by-product formation. Operation under supercritical conditions allows a biomass liquefaction of 84% w/w at 0.3 s of residence time. The obtained solid after the hydrolysis was composed of mainly lignin (86% w/w). The highest recovery of cellulose (C-6) and hemicellulose (C-5) as soluble sugars (73% w/w) was achieved at 0.19 s of reaction time. An increase in the reaction time decreased the yield of C-6 and C-5. A total recovery of C-5 was achieved at 0.19 s. On the other hand, the highest yield (65% w/w) of C-6 was achieved at 0.22 s of reaction time. The main hydrolysis product of C-6 and C-5 was glycolaldehyde, yielding 20% w/w at 0.22 s of reaction time. Furfural and 5-HMF production was highly inhibited under the experimental conditions, obtaining yields lower than 0.5% w/w. The hydrolysis reactions were performed in a continuous pilot plant at 400 °C, 25 MPa and residence times between 0.1 s and 0.7 s.