Browsing by Author "Stateva, Roumiana P."
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- Application of a novel approach to modelling the supercritical extraction kinetics of oil from two sets of chia seedsPublication . Villanueva Bermejo, David; Fornari, Tiziana; Calvo, Maria V.; FONTECHA, JAVIER; Coelho, Jose; Filipe, Rui; Stateva, Roumiana P.The kinetics of the supercritical fluid extraction of edible and discarded chia seeds was studied and modelled for the first time. The total oil was removed at 45 MPa and 60 degrees C after 240 min. The extraction kinetics was simulated using a dynamic model in gPROMS ModelBuilder environment and the kinetic parameters estimated. Triolein was chosen as a model compound of the chia oil. The agreement between the experimental yields and those calculated by the model was good with deviations in the range (1.2-6.6) %, except at 25 MPa and 60 degrees C (AARD = 9.5%). (C) 2019 The Korean Society of Industrial and Engineering Chemistry.
- Experimental Measurements and Correlation of the Solubility of Three Primary Amides in Supercritical CO2: Acetanilide, Propanamide, and ButanamidePublication . Coelho, Jose; Naydenova, Greta P.; Yankov, Dragomir S.; Stateva, Roumiana P.Solubilities of three primary amides, namely, acetanilide, propanamide, and butanamide, in supercritical carbon dioxide were measured at T = (308.2, 313.2, and 323.2) K over the pressure range (9.0 to 40.0) MPa by a flow type apparatus. The solubility behavior of the three solids shows an analogous trend with a crossover region of the respective isotherms between (12 to 14) MPa. The solubility of each amide, at the same temperature and pressure, decreases from propanamide to acetanilide. Pure compound properties required for the modeling were estimated, and the solubilities of the amides were correlated by using the Soave-Redlich-Kwong cubic equation of state with an absolute average relative deviation (AARD) from (1.3 to 6.1) %.
- Green extraction of high added value substances from spent coffee grounds: preliminary resultsPublication . Georgieva, Sílvia S.; Coelho, Jose; Campos, Filipe C.; Robalo, Maria Paula; Stateva, Roumiana P.A supercritical fluid extraction (SFE) with pure CO2 and ethanol as a co-solvent (10 %) of spent coffee grounds was carried out at temperatures from 313 K to 333 K, pressures up to 40.0 MPa and the results obtained were compared with those of the conventional Soxhlet method using n-hexane as a solvent. The best extraction yield (12.0 %) was achieved by SFE with CO2+10 % ethanol, compared to 9.5 - 10.7 % by SFE with pure CO2 and 10.4 % with n-hexane. The antioxidant potential was evaluated by DPPH method and the best antioxidant activity was exhibited by the spent coffee oil obtained by SFE, CO2+10 % ethanol. The quantification and the identification of the oils composition were carried out by NMR. The main constituents of the extracted oils referred to the triacylglycerols (TAGs, 98.9 - 96.8 %). Minor amounts of 1,2 diacylglycerols (1,2 DAGs, 2.7 - 0.68 %), and the diterpenes cafestol (6.02 - 2.26 %), 16-O-methylcafestol (4.86 - 2.00 %) and kahweol (2.11 - 0.71 %), as well as caffeine (1.45 - 0.1 %), were also present in all the extracts.
- Influence of co-solvents on the supercritical extraction kinetics of spent coffee grounds: experimental and modelling studiesPublication . Coelho, Jose; Filipe, Rui; Robalo, Maria Paula; Boyadzieva, Stanislava S.; Cholakov, Georgi; Stateva, Roumiana P.Coffee is one of the most widely used beverages. An estimated 3.5 billion cups of coffee are drunk worldwide every day. In EU alone, for the period 2011-2013, 2.5 Mt of coffee were consumed. Taking into consideration that the production of coffee in 2015 was approximately 9 Mt and that from each kg of coffee 0.91 kg of solid waste is produced, the importance of a further valorization of this residue becomes obvious. In recent years, the biorefinery concept has been identified as the most promising route for employment of the full potential of a biomass by maximizing its conversion into high value products. Its main bottleneck, however, is how to extract the energy and non- energy compounds from the biomass without damaging one or more of the components, e.g. those which are heat sensitive. Spent coffee grounds (SCGs) contain large amounts of fatty acids, lignin, cellulose, hemicellulose, etc. and can be exploited as an excellent source of value-added energy and non-energy related products (e.g, antioxidants and other functional additives).
- On the solubility of three disperse anthraquinone dyes in supercritical carbon dioxide: new experimental data and correlationPublication . Coelho, Jose; Palavra, António F.; Stateva, Roumiana P.Solubility measurements of quinizarin. (1,4-dihydroxyanthraquinone), disperse red 9 (1-(methylamino) anthraquinone), and disperse blue 14 (1,4-bis(methylamino)anthraquinone) in supercritical carbon dioxide (SC CO2) were carried out in a flow type apparatus, at a temperature range from (333.2 to 393.2) K and at pressures from (12.0 to 40.0) MPa. Mole fraction solubility of the three dyes decreases in the order quinizarin (2.9 x 10(-6) to 2.9.10(-4)), red 9 (1.4 x 10(-6) to 3.2 x 10(-4)), and blue 14 (7.8 x 10(-8) to 2.2 x 10(-5)). Four semiempirical density based models were used to correlatethe solubility of the dyes in the SC CO2. From the correlation results, the total heat of reaction, heat of vaporization plus the heat of solvation of the solute, were calculated and compared with the results presented in the literature. The solubilities of the three dyes were correlated also applying the Soave-Redlich-Kwong cubic equation of state (SRK CEoS) with classical mixing rules, and the physical properties required for the modeling were estimated and reported.
- Recovering value from organic waste materials: Supercritical fluid extraction of oil from industrial grape seedsPublication . Coelho, Jose; Filipe, Rui; Robalo, Maria Paula; Stateva, Roumiana P.Supercritical extraction of oil from grape seed samples obtained from a Portuguese industry was carried out at temperatures from (313-333) K, pressures up to 40.0 MPa and different scCO(2) flow rates. The qualitative analysis of the crude oil was carried out by NMR. The fatty acids were analyzed by GC-Fid with reference to the parameters in Annex I to European Commission Regulation. The results show similar content of TAGs and DAGs both in the n-hexane and scCO(2) extraction methods, but the latter have higher PUPA and lower saturated fatty acids content. A dynamic model was used to simulate the extraction curves in gPROMS ModelBuilder. The grape seed oil was represented as either a one or a three component mixture of triacylglycerols, and the deviation between the experimental and calculated extraction yields was in the range (2-9) % for the first, and (4-11) % for the second case.
- Semi-empirical models and a cubic equation of state for correlation of solids solubility in scCO(2): dyes and calix[4]arenes as illustrative exemplesPublication . Coelho, Jose; Filipe, Rui; Naydenova, Greta P.; Yankov, Dragomir S.; Stateva, Roumiana P.Knowledge of a compound's solubility in the supercritical solvent is crucial to the definition of the optimal operating conditions and consequently to the development of supercritical applications. The present paper examines the performance of two of the most widely used groups of models for correlating the solubility of solid solutes in supercritical carbon dioxide – equations of state (EoSs) and semi-empirical density based models. The Soave-Kwong-Redlich (SRK) EoS with the one-fluid van der Waals mixing rule represents cubic EoSs, while the group of the density-based models includes Chrastil, Kumar and Johnston, Bartle et al., Méndez-Santiago and Teja, Garlapati and Madras, Nejad et al. and Khansary et al. models. The seven solutes chosen as illustrative examples are compounds of interest to the dry dyeing processing techniques and biotechnological processes and have diverse structural complexity. The results obtained reveal that the more recently advocated density-based models (Garlapati and Madras, Nejad et al. and Khansary et al. models) perform better with overall average absolute deviations, AARD, of 6.5, 9.0 and 9.3%, respectively. The 6.7% overall AARD for the SRK CEoS is acceptable and it can be used as a reliable thermodynamic model to predict the solubility of any compound for which there is no sufficient experimental data available.
- Solubilities of C‑Tetraalkylcalix[4]resorcinarenes in SCCO2: experimental measurements, characterization, and correlationPublication . Coelho, Jose; Naydenova, Greta P.; Miloshev, Stoyan M.; Novakov, Christo P.; Petrova, Pavlina P.; Yankov, Dragomir S.; Stateva, Roumiana P.The solubilities of two C-tetraalkylcalix[4]resorcinarenes, namely C-tetramethylcalix[4]resorcinarene and C-tetrapentylcalix[4]resorcinarene, in supercritical carbon dioxide (SCCO2) were measured in a flow-type apparatus at a temperature range from (313.2 to 333.2) K and at pressures from (12.0 to 35.0) MPa. The C-tetraalkylcalix[4]resorcinarenes were synthesized applying our optimized procedure and fully characterized by means of gel permeation chromatography, infrared and nuclear magnetic resonance spectroscopy. The solubilities of the C-tetraalkylcalix[4]resorcinarenes in SCCO2 were determined by analysis of the extracts obtained by HPLC with ultraviolet (UV) detection methodology adapted by our team. Four semiempirical density-based models, and the SoaveRedlichKwong cubic equation of state (SRK CEoS) with classical mixing rules, were applied to correlate the solubility of the calix[4]resorcinarenes in the SC CO2. The physical properties required for the modeling were estimated and reported.
- Solubility of red 153 and blue 1 in supercritical carbon dioxidePublication . Coelho, Jose; Stateva, Roumiana P.Solubilities of red 153, (3-[[4-[[5,6(or 6,7)-dichloro-2-benzothiazolyl]azo]phenyl]ethylamino]propanenitrile), an azo compound, and disperse blue1 (1,4,5,8-tetraaminoantraquinone) in supercritical carbon dioxide (SC CO(2)) were measured at T = (333.2 to 393.2) K over the pressure range (12.0 to 40.0) MPa by a flow type apparatus. The solubility of red 153 (0.985. 10(-6) to 37.2. 10(-6)) in the overall region of measurements is found to be significantly higher than that of disperse blue 1 (1.12.10(-7) to 4.89.10(-7)). The solubility behavior of disperse red 153 follows the general solubility trend displayed by disperse dyes with a crossover pressure at about 20 MPa. On the other hand, blue 1, which is a disperse anthraquinone dye, exhibits unexpected behavior not recorded previously there is no crossover pressure at the temperature and pressure ranges studied, and the dye's solubility at T = 333.2 K practically does not increase with pressure. To the best of our knowledge, there are no previous measurements of blue 1 solubility in SC CO(2) reported in the literature. The experimental data were correlated by using the Soave Redlich Kwong equation of state (EoS) with the one-fluid van der Waals mixing rule, and an acceptable correlation of the solubility data for both dyes was obtained.