ROUMIANA PETROVA STATEVA

ROUMIANA PETROVA STATEVA
Bulgarian Academy of Sciences | BAS · Institute of Chemical Engineering

Full Professor; PhD; MSc

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134
Publications
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Publications

Publications (134)
Article
Full-text available
In this study, sustainable technology microwave-assisted extraction (MAE) in association with green solvents was applied to recover phenolic compounds from spent coffee grounds (SCGs). A design of experiments (DOE) was used for process optimization. Initially, a 24−1 two level Fractional Factorial Design was used and ratios “solvent to solute” and...
Article
An example of a sustainable and renewable but highly underused biomass with considerable potential as a source of a wide spectrum of valuable compounds is Arctium lappa, also known as burdock. In this work the feasibility and efficiency of advanced techniques applying compressed fluids to recover value from burdock seeds and roots was examined, and...
Article
Full-text available
In the present study a new Bulgarian strain of Scenedesmus sp. was taxonomically and molecularly identified as Scenedesmus obliquus. Тhe most favorable cultivation conditions in terms of temperature, light intensity and growth phase were determined. The biochemical composition analyses showed that the strain is among the best producers of proteins,...
Article
Full-text available
The development of a bio-based economy has its foundations in the development of efficient processes to optimize biomass potential. In this context there are a multitude of molecules that can be either synthetized or recovered from biomass, among those the so-called 12 building-blocks reported by the US Department of Energy. Even if their identific...
Chapter
This chapter covers the challenges of thermodynamic properties and phase equilibrium calculations in biofuels process design. The development and application of a robust, reliable and versatile tool a thermodynamic modeling framework (TMF), based on advanced scientific knowledge for modeling and simulation of biofuel‐related systems is of key impor...
Article
The use of biomass, particularly, a second-generation one, as a renewable raw material is crucial to sustain the chemical industry. To favor the development of such processes, one needs to make a cost evaluation, which requires the knowledge of process thermodynamics and kinetics. In this paper, measurements of different physicochemical properties...
Article
Spent coffee grounds (SCGs) were extracted with supercritical CO2 at temperatures from 313 to 333 K, pressures up to 50.0 MPa and different scCO2 flow rates. The addition of co-solvents isopropanol, ethanol and ethyl lactate decreased the time to achieve the maximum oil yield, to half of that with pure CO2. Analysis of the extracted oils by NMR, sh...
Article
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 °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...
Article
Full-text available
The thermodynamic behavior of mixtures is fundamental for the process systems engineering. Phase stability analysis is a key step for process design and it implies the global minimization of Tangent Plane Distance Function (TPDF). This thermodynamic calculation is challenging and effective global optimization methods are required. In this paper, tw...
Article
Pressurized liquid extraction (PLE) of Arctium lappa leaves using aqueous ethanol is examined and presented for the first time in this work. In addition, global extraction yields, chemical composition, phenolic compounds and antioxidant activity of the PLE extracts were compared with those obtained by supercritical fluid extraction (SFE). PLE extra...
Article
Literature data on the extraction of carotenoids from microalgae with supercritical carbon dioxide (scCO 2 ) were used to describe the process as an extraction of a solution of carotenoids in oil. A mathematical model for oil extraction from microalgae, including also the adsorption on microalgal surfaces, was extended for this purpose. The working...
Article
Full-text available
The huge amounts of waste generated every year by the industry, in addition to the great loss of valuable materials, pose serious organisational problems, both from an economic and ecological point of view. Many of the residues, however, have the potential to be reused and utilized completely via integrated bio-refining technologies. Extraction tec...
Article
Full-text available
This work addresses the modelling and simulation of the kinetics of CO 2 supercritical extraction of oils from biomass. Experimental and simulation results from different matrices and models are presented. gPROMS Model Builder is used to find solutions to three different models applied to study the extraction of three different volatile oils from a...
Article
Full-text available
In our work for the first time is outlined the application of a novel methodology to examine whether the roots of Arctium Lappa, commonly known as burdock, can be considered a potential feedstock for a biorefinery targeted to producing valuable medicinal products with a wide spectrum of applications. The biorefinery should implement predominantly m...
Article
Full-text available
In this study, an advanced green extraction technique applying supercritical CO 2 (scCO 2) and scCO 2 with co-solvent (esters, alcohols or hydroalcoholic solutions) is used to obtain value added compounds from the aerial (leaves and seeds) and underground (roots) parts of Arctium lappa, commonly known as burdock. In order to increase the yields mul...
Article
Full-text available
A supercritical fluid extraction (SFE) with pure CO 2 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 achiev...
Conference Paper
Full-text available
The overproduction of free radicals and oxidative stress are involved in the progression of degenerative diseases. Natural antioxidant substances and unsaturated fatty acids like ω-3 and ω-6 play a key role in interfering with the oxidation process by inhibiting free radicals. Spent coffee and grape seeds are waste by-products from daily coffee con...
Article
Full-text available
Supercritical CO2 extraction of oil from grape seed samples obtained from a Portuguese industry without any previous treatment was carried out at temperatures from (313 to 333) K, pressures up to 40.0 MPa and different scCO2 flow rates. The qualitative analysis of the crude oil was carried out by NMR. The fatty acids were analyzed by GC-FID with re...
Article
Full-text available
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 scCO2 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...
Article
In this work, a multicomponent model for understanding the relationship between the chemical compositions of an extract and extracted plant is developed and presented for the first time. Its robustness and efficiency were validated on the example of furanocoumarins and waxes extracted from aerial parts of common rue with supercritical CO2 at pressu...
Article
Full-text available
The solubility of ferulic acid in ethyl lactate + water mixtures was measured at ambient temperature and pressure, and reported for the first time in this work. It was demonstrated that the acid solubility in the respective mixed solvents was considerably higher than in either pure ethyl lactate or water. Similar behavior pattern was recently repor...
Article
Full-text available
The present paper examines the performance of cubic equations of state (CEoSs) and semi-empirical density-based models in correlating the solubility in supercritical carbon dioxide (scCO2) of several solid compounds of interest to the food industry, namely 2-propenamide, bixin, β-carotene and C-tetramethylcalix[4]resorcinarene. The four target solu...
Article
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 supercriti...
Article
This paper presents a new approach to modelling the kinetics of a supercritical fluid extraction of a mixture of solids. Experimental data on pure long-chain n-alkanes solubility in supercritical CO2 (scCO2) was reviewed and selected data was correlated applying a semi-empirical density-based model and an equation of state. On the example of extrac...
Article
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 w...
Article
The solubilities of two C-tetraalkylcalix[4]-resorcinarenes, namely C-tetramethylcalix[4]resorcinarene and C-tetrapentylcalix[4]resorcinarene, in supercritical carbon dioxide (SCCO 2) 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...
Chapter
Knowledge of phase equilibria behaviour of food substances and green solvents under high pressure conditions is required to exploit to the full the advantages of high pressure fluid technology for green food processing. Data are currently available for quite a large number of systems at a wide range of conditions; still experimental measurement of...
Book
Full-text available
The aim of this book is to present the fundamentals of high pressure technologies from the perspective of mass transfer phenomena and thermodynamic considerations. Novel food applications are exposed and their relation to chemical analysis, extraction, reaction and particle formation processes are outlined. The chapters are written by a diverse gro...
Article
Thymol (2-isopropyl-5-methylphenol) is the main monoterpene phenol found in thyme essential oil. This compound has revealed several biological properties, such as antibacterial, anti-inflammatory, and antioxidant. In this work, a comparison was made between the performance of different green solvents (ethanol, limonene and ethyl lactate), by pressu...
Article
The paper introduces a novel approach to the solution of the phase stability problem under constant temperature and pressure with equations of state (EoSs) as the thermodynamic model. An effective strategy that is designed to consecutively transform the tangent-plane distance function (hyper)surface and guarantees a nonrepetitive determination of a...
Article
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 is...
Article
The solubility of (−)-α-bisabolol, ((−)-6-methyl-2-(4-methyl-3-cyclohexen-1-yl)-5-hepten-2-ol), a monocyclic sesquiterpene alcohol, in sub- and supercritical CO2 was measured at the temperatures (313.2, 323.2, and 333.2) K and pressures ranging from (7 to 12.5) MPa by a dynamic method. To the best of our knowledge, there are no previous measurement...
Article
Ethyl lactate (ethyl 2-hydroxypropanoate) is emerging as an ecofriendly solvent with wide applications in the food, pharmaceutical, and fine chemical industries. Furthermore, its potential use as a solvent in chemical reactions which could be performed in supercritical media and as an effective cosolvent in supercritical extraction processes and/or...
Article
Two different numerical techniques, applying either the SRK or the PC-SAFT equations of state, were used to predict the multiphase behavior exhibited by the ternary systems nitrogen + methane + ethane, nitrogen + methane + propane, and nitrogen + methane + n-butane. The predictions with both equations of state were compared against experimental dat...
Article
Full-text available
In the 21st century, the mission of chemical engineering is to promote innovative technologies that reduce or eliminate the use or generation of hazardous materials in the design and manufacture of chemical products. The sustainable use of renewable resources, complying with consumer health and environmental requirements, motivates the design, opti...
Article
Solubilities of red 153, (3-[[4-[[5,6(or 6,7)-dichloro-2-benzothiazolyl]azo]phenyl]ethylamino]propanenitrile), an azo compound, and disperse blue 1 (1,4,5,8-tetraaminoantraquinone) in supercritical carbon dioxide (SC CO2) 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 r...
Article
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...
Article
Experimental and modeling studies of the liquid−liquid equilibria at ambient pressure of three model systems—squalene + ethyl lactate, olive oil + ethyl lactate, and squalene + olive oil + ethyl lactate—were performed with the view to explore the potential application of an agrochemical solvent, namely, ethyl lactate, to recover squalene from pretr...
Article
Full-text available
The ability of two thermodynamic approaches to predict the solubility of solid compounds in hot pressurized water is studied and compared. The Regular Solution Theory, based on the solubility parameter concept, and UNIFAC-based models were applied to calculate the solute activity coefficient and then, solubility predictions were compared with exper...
Article
The relevant applications that supercritical fluid extraction (SFE) has attained in the food industry in the last decades increased the interest in the development of thermodynamic models to represent the phase equilibria of systems comprising food-related substances and supercritical carbon dioxide (SCCO2). The targets are twofold: (i) calculation...
Article
The extracts of valuable vegetable oils containing a number of minor components (sterols, tocopherols, carotenoids, etc.) have added value as pharmaceuticals and food additives. Beta-sitosterol (BS) as minor component of vegetable oil was extracted from ground seeds of sea buckthorn with supercritical CO2 at pressures 15–60 MPa and temperatures 40–...
Article
Full-text available
This paper is part of a study on the possibility of using aqueous two-phase systems (ATPSs) for separation of low-molar-mass organic acids in the biotechnology industry. We present for the first time experimental data on the influence of titrating organic acids on the phase behaviour of the ATPSs, containing poly(ethyleneglycol) (PEG) and poly(ethy...
Article
Full-text available
This paper is part of a study on the possibility of using aqueous two-phase systems (ATPSs) for separation of low-molar-mass organic acids in the biotechnology industry. We present for the first time experimental data on the influence of titrating organic acids on the phase behaviour of the ATPSs, containing poly(ethyleneglycol) (PEG) and poly(ethy...
Conference Paper
We have recently developed several new methods for property prediction to complement the traditional group contribution techniques, asymptotic behavior correlations and Quantitative Structure-Property Relationships (QSPR). These methods include the Quantitative Structure-Structure Property Relationship (QS2PR), the shortcut QS2PR method (SC-QS2PR)...
Article
A new method for applying Quantitative Structure Property Relationship type methods for prediction of properties needed for phase equilibrium calculation is presented. The use of the new method is demonstrated by predicting vapor pressure for members of the 1-alkene homologous series. It is shown that the new method enables the prediction of vapor...
Article
In this work, novel techniques for predicting vapor pressure and binary interaction coefficients for homologous series are developed based on the previously proposed targeted quantitative structure−property relationship (TQSPR) and QS2PR methods. For predicting vapor pressure variation as a function of temperature, a two-reference compound (TRC) QS...
Article
In this paper, which forms part of a study on aqueous two-phase systems (ATPS) for separation of low-molar-mass organic acids in the biotechnology industry, we examine the phase behaviour of ATPSs containing poly(ethylene glycol) (PEG) and poly(ethyleneimine) (PEI) as a function of pH, the nature of the acid used for titrating PEI, and the addition...
Article
In this work, we present the modeling of the vapor−liquid−liquid equilibria (VLLE) for three ternary systems that are of interest in the natural gas and oil industry: nitrogen + methane + n-pentane, nitrogen + methane + n-hexane, and nitrogen + methane + n-heptane. The capabilities of the PC-SAFT and SRK equations of state to predict the complex ph...
Article
Solubilities of ethanamide (acetamide) and 2-propenamide (acrylamide) in supercritical carbon dioxide were measured at T = (308.2, 318.2, and 333.2) K over the pressure range (9.0 to 40.0) MPa by a flow-type apparatus. The solubility of acetamide (2.3·10−4 to 31.3·10−4) in the overall region of measurements is approximately twice that of acrylamide...
Article
Trans-3-phenyl-2-propenoic acid (cinnamic acid; trans-cinnamic acid) is widely used in food, cosmetics, and pharmaceuticals because of its reported antimicrobial, antifungal, and antioxidant properties. This paper is devoted to the experimental measurement of the solubility of solid trans-cinnamic acid in pure supercritical CO2 and in supercritical...
Article
Full-text available
Prebiotic carbohydrates are defined as non-digestible carbohydrates that beneficially affect the host by selectively stimulating the growth and/or activity of a limited number of bacteria in the colon.The present study is focused on two prebiotic ketosugars: tagatose and lactulose, which are currently obtained by alkaline isomerization of their res...
Article
Modern semi-empirical cubic EOSs are usually attached by complex functionalities, such as Huron-Vidal (HV)-type mixing rules. Although this practice improves the flexibility of the models, it also complicates consideration of an overall picture of phase behavior. As a result, GE-based equations are usually adjusted to the experimental data by way o...
Article
This work explores the capabilities of UNIFAC-based models to predict the solubility of different solid solutes in subcritical water as a function of temperature. The original UNIFAC, its modified (Dortmund) version and the A-UNIFAC model, which explicitly includes association effects between groups, are applied to calculate the solubility of solid...
Article
The ability of the targeted quantitative structure−property relationships (TQSPR) method to predict properties for groups of congeneric compounds was tested with Tc and pc data for five homologous series: n-alkanes, 1-alkenes, 1-alkanols, n-alkylbenzenes, and n-alkanoic acids. Training sets were identified from a database of 326 hydrocarbon and oxy...
Article
The targeted quantitative structure–property relationship (TQSPR) method of Brauner et al. [Brauner, N., Stateva, R. P., Cholakov, G. St., & Shacham, M. (2006). A structurally “targeted” QSPR method for property prediction. Industrial & Engineering Chemistry Research, 45, 8430–8437] is analyzed in this study with respect to its various algorithmic...
Conference Paper
Full-text available
The present work is part of a broader study devoted to the application of aqueous two-phase systems (ATPSs) for in situ separation of low molar mass organic acids in the biotechnology industry. The ATPSs studied comprise poly(ethyleneglycol) (PEG) and poly(ethyleneimine) PEI. The PEG average molar mass was 4000 gmol-1
Conference Paper
Full-text available
Prediction of thermophysical properties required for heat transfer calculation and the design and development of thermal systems is considered. Newly developed computational methods for property prediction are described and their use is demonstrated for the prediction of various constant properties, such as normal boiling and melting temperature, c...
Article
In this paper, which forms part of a study on aqueous two-phase systems (ATPS) for separation of low-molar-mass organic acids in the biotechnology industry, we present experimental results on the phase equilibria of ATPS containing poly(ethylene glycol) (PEG) and either K2HPO4 or KH2PO4 or a fixed mixture of the two phosphates. The measurements wer...
Article
Linear QSPRs, containing 1 through 4 descriptors, are developed for predicting the normal boiling temperature, melting point temperature, and critical properties for the n-alkane, 1-alkene, n-alkylbenzene, 1-alcohol, and alkanoic monocarboxylic acid homologous series. It has been shown that property values for which experimental data are available...
Article
Full-text available
Prediction of thermophysical properties required for heat transfer calculation and the design and development of thermal systems is considered. Newly developed computational methods for property prediction are described and their use is demonstrated for the prediction of various constant properties, such as normal boiling and melting temperature, c...
Article
Development of Quantitative Structure Property Relationships (QSPR) for property prediction, targeted for a particular applicability domain (AD), and definition of the AD boundaries are considered. The AD is defined in terms of the target compound (for which a property has to be predicted) belonging to a homologous series and including carbon atoms...
Article
The targeted quantitative structure–property relationship (TQSPR) method of Brauner et al. [2006. A structurally “targeted” QSPR method for property prediction. Industrial & Engineering Chemistry Research 45, 8430–8437] is analyzed in this study with examples involving prediction of critical temperatures of hydrocarbons. Targeted are 108 hydrocarbo...
Article
Data on menthol + CO2 phase behaviour and menthol solubility in dense CO2 are needed to optimise supercritical extraction of peppermint oil. The paper presents novel experimental data for the phase diagram of (−)-menthol + CO2 binary system in the temperature range 5–40 °C and pressures up to 8.2 MPa, including menthol melting point depression, as...
Article
The Area method for phase stability analysis is re-examined from the viewpoint of the topology of thermodynamic surfaces. A new generalization of the Area method objective function and the maximum area criterion is proposed in terms of the convex envelope of thermodynamic surfaces. Several special cases for two-component, single- and two-phase syst...