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Broken-and-intact cell model for supercritical fluid extraction: Its origin and limits
Abstract
One group of mathematical models for supercritical fluid extraction from plants is based on the Broken-and-Intact Cell (BIC) concept. A simplified BIC model with analytical solution, derived for the extraction of vegetable oils from seeds, was published in 1994. It has been used by several researchers also for the extraction of other solutes from other plant parts. The aim of this contribution is to show how the simplified BIC model was derived from Lack’s model, for what type of extractions it is suited and where it fails, and how the BIC models have been improved since then.
... Also, the present paper is a logical continuation of recently published [6], where the extraction process was considered for random and stationary particle distribution. The paper [7] provides a basic mathematical model founded on the Broken-and-Intact Cell (BIC) approaches with the applications in simulating the extraction of bioactive compounds from plants using supercritical fluid. The article [8] gives a review of mathematical modelling methods used in the extraction process, along with a thorough analysis of the mathematics behind the different stages in the procedure. ...
... The summation is over all the particles in the computational domain at the time. The rate of exchange of the active compound in i-th particle is (5) Also function ψ(r,t) represents the concentration of the active compound bounded in the particles interpreted as "intact" cells in BIC models [7]. The exchange rate into the solvent is (6) . ...
In this research, we extend our studies of the extraction process from diverse plant materials, introducing advancements to our previous models. Our framework considers dynamic elements by taking into account the motion of the particles, departing from the statical particle assumption in prior articles. Several methods such as moving geometries or modified equations for a system with moving particles in Lagrangian coordinates are introduced to boost the precision of our simulations, taking into account the complex dynamics of the solvent and its interaction with the plant material. Expanding beyond our focus on supercritical carbon dioxide (scCO2), our research is addressing some different applications. Besides the traditional solvent-based extractions, we consider potential applications in filtration, wood industry processes, etc. This allows our model to adapt to diverse industrial contexts with varied extraction mediums. Our coupled system of equations contains fluid dynamics equations for solvent flow, reaction-advection-diffusion equations for solute, and equations governing remaining solute concentration in biomass. The exchange of active material between solid and fluid is modelled by the Langmuir law. Applying finite volume techniques and implemented in the Octave/Matlab environment, our model captures the temporal evolution of two and three dimensional solute distribution and solvent velocity field. This modular framework facilitates the integration of tailor-made laws to represent diverse plant materials, ensuring versatility across applications. Through our simulations, we present the analysis of our modified model’s performance and discuss its advantages and limitations. This research is a slight step forward in understanding and optimising extraction processes, offering valuable insights for industries involved in functional foods, nutraceuticals, pharmaceuticals, cosmetics, filtration, and wood processing.
... The article [1] presents a model with an analytical solution for the extraction of vegetable oils using supercritical carbon dioxide, which can be used to evaluate extraction parameters by comparing the extraction curves calculated by the model with experimental data. The article [2] discusses the origins and limitations of a simplified mathematical model based on the Broken-and-Intact Cell (BIC) concept, which is used to model supercritical fluid extraction of bioactive compounds from plants and suggests improvements to the model that have been developed since its initial publication. The article [3] provides a comprehensive overview of mathematical modelling techniques applied to the extraction process and offers a detailed examination of the mathematical methods used to describe the various stages of the process. ...
... Three-dimensional setting for the computational domain; particles (pieces of biomass) allocated randomly By solving (1)-(2) in this domain we obtain a stationary velocity vector field. First setting is the horizontal direction driven field whereas the particles are situated on top of the computational domain and the second one deals with three-dimensional particle allocation with obstacles visible: Zoom shots of three-dimensional setting for the computational domain. ...
The authors consider the process of extraction from heterogeneous plant material; a novel model offering 3D spatial resolution is proposed and simulation possibilities by applying several modern numerical methods for three dimensional problems are discussed. These types of problems naturally arise when one wishes to mathematically describe the processes of the extraction with solvents such as supercritical carbon dioxide (scCO2). The results of this process meet the demand of the functional foods, nutraceutical, pharmaceutical and cosmetic industries on bioactive compounds. The models used in typical simulations by the industry offer no spatial resolution of the extraction process, however, when novel designs of extractors are developed, the three dimensional flow of the solvent and its interaction with the plant material should be considered. We propose a coupled system of equations consisting of fluid dynamics equations describing the flow of the solvent and reaction-advection-diffusion equations for the solute, plus equations describing the remaining concentration of solute in the biomass. The exchange of the active material between the solid and fluid is modelled by the Langmuir law. The initial distribution of solute in the plant material is not assumed to be homogeneous, nor are the extraction parameters, i.e. heterogeneous mixture of plant materials can be covered by this model. The equations are discretized by using finite volume techniques and currently implemented in Octave/Matlab environment. As a result, the temporal evolution of the three dimensional distribution of the solute is obtained along with the velocity field of the solvent, allowing detailed studies of the extraction process in a virtual design. The model is modular, allowing integrating tailor-made laws to describe various plant materials. The authors present simulation results and analyse the advantages and disadvantages of the proposed methods and approaches.
... As can be seen from this [224] broken and intact cells theory in modeling SFE of solid matrices. Sovová [225] discussed the deficiencies of the original BIC [25] model and reviewed the improvements carried out by different researchers on this model since its publication. It has been noted that the newer BIC models have been reviewed to overcome the drawbacks, but they need numerical solution for mass balance equations instead of analytical solution [225]. ...
... Sovová [225] discussed the deficiencies of the original BIC [25] model and reviewed the improvements carried out by different researchers on this model since its publication. It has been noted that the newer BIC models have been reviewed to overcome the drawbacks, but they need numerical solution for mass balance equations instead of analytical solution [225]. ...
... At present, lots of mass transfer models have been developed, mainly including Broken and intact cell model, the Shrinking Core model, Hot Ball Diffusion model and some simple theoretical models. These models have been summarized in detail in several review papers published in the past [111,112,113]. This section will briefly summarize the above mass transfer kinetic models which are used to predict the performance of extracting active substance from solid matrices by scCO 2 in the recent ten years. ...
... Several existing review papers [111,112] on mass transfer kinetics model of scCO 2 extraction have discussed the research status of Broken and Intact Cell model before 2012 in detail. In fact, the original model has the following problems [112,113]: Firstly, the introduced equilibrium solubility does not consider the interaction between solute and solid matrix, which will affect the desorption equilibrium of solute in fluid phase and solid phase; Secondly, the specific microstructure of different types of solid matrix under the assumption of the original model needs to be further explored; Thirdly, during the extraction process, the changes of physical properties of scCO 2 in the trans-critical region need to be considered, which will affect its extraction performance. Therefore, further researches will mainly focus on the above points. ...
Recently, scCO2 (supercritical-carbon-dioxide) used as the green medium in industrial production has attracted much attention of researchers because of its unique physical properties. Aiming at the direct or indirect interaction between scCO2 and particles, this paper introduces in detail the research status about the combination of scCO2 and particles to guide industrial production from three aspects. For the performance of transporting particles by scCO2 in the two-phase flow system of scCO2 and particles, the effect of scCO2 flow rate, physical properties of scCO2 and particles as well as the transporting type are reviewed. As to the heat transfer performance from particles to scCO2, the influence of scCO2 and particles flow rate, physical properties of scCO2 and particles as well as the contact style between scCO2 and particles are presented and discussed. For the mass transfer kinetics model between scCO2 and particles of the supercritical extraction, the governing equations and application occasions of different models are presented. Furthermore, the combination or comparison of various mass transfer kinetics models for the accuracy of predicting extraction performance comparisons among above models are conducted. The full text is mainly based on the theoretical aspect and part on experimental aspect which shows the use of carbon dioxide combined with particles to guide industrial production from the above special point of view
... A complete SFE model should include two submodels: the "external" macroscale model, which describes the transfer processes at the level of the extractor apparatus containing the packed bed, and the "internal" microscale model, which presents the kinetics of oil extraction from a single particle of the layer. The first is usually formulated [16][17][18] as a model of a plug flow apparatus [19] in the assumption that the solution moves along the column with spatially uniform velocity and negligible backwards mixing. It is important to take into account the polydispersity of the ground raw material sample [6,20,21]. ...
... The microscale model is determined by the internal, cellular structure of plant materials. Various models that take into account the effect of the internal structure on the extraction dynamics were proposed in the literature [6,17,20,23,[37][38][39][40]. The resistance to the oil mass transfer is usually associated with the cell membranes that confines the cell with stored substances, and with the cell walls surrounded by the intercellular space, which together play the role of transport channels. ...
... At the same time, the bidisperse structure of a packed bed explains various extraction effects within the framework of the SC approach, in particular, the prolonged initial high-rate extraction stage of SFE, followed by the rapid decrease of the outlet solute concentration. 14,17 2. MODEL FORMULATION 2.1. Mass Transfer in the Plant Material. ...
... The SC model of a packed bed with a bidisperse particle size distribution, {(a 1 ; f 1 ), (a 2 ; 1 − f 1 )}, allows us to reproduce the SFE kinetics in more detail and with higher accuracy, 19,39 in particular, to study the complex nature of diffusive and convective/dispersive interactions on the particle-and pore-scale levels of the mass-transfer phenomena. The proposed model (20)−(23) for bidisperse beds is equivalent 10 to the Broken-and-Intact Cells (BIC) approach, 17 with the volume fraction f 1 of dust particles effectively substituting for the broken cells. The SFE conditions in this case are fully described by four independent dimensionless numbers: η 1 , η 2 , δ ax (a 1 ), and f 1 . ...
Successful development of an industrial-scale process for supercritical fluid extraction (SFE) of oil from ground plant material requires detailed analysis of the effects associated with the solute transport in porous media. In the present paper, a case of the raw material with high initial oil content is considered, and the influence of the axial flow dispersion on the extraction dynamics is analyzed numerically and analytically. The typical one-dimensional convection−dispersion mass-transfer model on the extractor-scale level is revisited, and the widely accepted shrinking core model is used to describe the solute diffusion on the particle-scale level. The SFE description also accounts for the polydispersity of the ground material. The set of dimensionless parameters required for complete analysis of different extraction regimes is defined. The influence of the axial flow dispersion on the extraction kinetics manifests itself mainly via polydispersity of the ground raw material, despite being insignificant in typical SFE implementations.
... In order to ensure high extraction efficiencies and to obtain high quality and purified extractions (Chemat et al. 2019;Yousefi et al. 2019), the design and the optimization strategies are critical. In particular, with SF extractions, the aim is on the reduction Fig. 7.1 Overview of the supercritical carbon dioxide (SF-CO 2 ) extraction process of biomolecules (Grosso et al. 2010;Sovová 2012;Huang et al. 2012;da Silva et al. 2016;Shukla et al. 2019;Yousefi et al. 2019) Perrut et al. (1997) Mass transfer modelling of apricot kernel oil extraction with supercritical carbon dioxide Özkal et al. (2005) Mathematical modelling of supercritical CO 2 extraction of volatile oils from aromatic plants Grosso et al. (2010) Prediction of isoflavone extraction from soybean meal using supercritical carbon dioxide with cosolvents Kumhom et al. 2011 Theoretical models for supercritical fluid extraction Huang et al. (2012) Kinetic study of the supercritical CO 2 extraction of different plants from the Lamiaceae family Fornari et al. (2012b) Modeling the supercritical fluid extraction of essential oils from plant materials Sovová (2012) Effects of high water content and drying pre-treatment on supercritical CO 2 extraction from Dunaliella salina microalgae: Experiments and modelling Mouahid et al. (2016) Modeling of the kinetics of supercritical fluid extraction of lipids from microalgae with emphasis on extract desorption Sovová et al. (2016) Supercritical carbon dioxide extraction of Calendula officinalis: Kinetic modeling and scaling up study López-Padilla et al. (2017) Modeling of the kinetics of supercritical fluid extraction of lipids from microalgae with emphasis on extract desorption Sovová et al. (2016) Broken-and-intact cell model for supercritical fluid extraction: Its origin and limits Sovová (2017) Supercritical carbon dioxide extraction of pomegranate (Punica granatum L.) seed oil: Kinetic modelling and solubility evaluation Natolino and Da Porto (2019) New developments in the modelling of carotenoids extraction from microalgae with supercritical CO 2 Sovová and Stateva (2019) Extraction of vetiver (Chrysopogon zizanioides) root oil by supercritical CO 2 , pressurized-liquid, and ultrasound-assisted methods and modelling of supercritical extraction kinetics Evaluation of the effects of temperature and pressure on the extraction of eugenol from clove (Syzygium aromaticum) leaves using supercritical CO 2 Frohlich et al. (2019) of extraction time, amount of solvent, energy usage, costs, waste produced and the environmental impact (Chemat et al. 2019;Yousefi et al. 2019). Figure 7.1 presents a summary of the various components of the SC-CO 2 extraction process of biomolecules. ...
... Natolino and Da Porto (2019) have applied kinetic (BIC model) and solubility (Chrastil model) modelling for the SC-CO 2 extraction of pomegranate seed oil from Punica granatum L. The "shrinking core model" was applied for the isoflavone extraction (SC-CO 2 and methanol) from soybean meal by Kumhom et al. (2011) and investigated the axial dispersion coefficient, effective diffusivity, solubility and the film "mass transfer coefficient", of which the film "mass transfer coefficient" and the solubility were found to be the most significant. Sovová (2012Sovová ( , 2017, Sovová et al. (2016) and Sovová and Stateva (2019) have described the modelling of the SF extraction process for essential oils, lipids and carotenoids, which have been readily adapted to represent extraction curves. Optimization targets (Fig. 7.1) are based on varying mainly the pressure, temperature and the flow rate of the SC-CO 2 . ...
The Amazon is an ecological system that comprises a considerable part of South America and that presents a great biodiversity of plants and fruits. Most of them have bioactive compounds, such as polyphenols and carotenoids, that are associated with the reduced risk of development of various chronic and degenerative diseases. To obtain such substances, the supercritical fluid extraction stands out among other extraction methods due to environmental concerns, since this technology uses green solvents such as carbon dioxide (CO2), water (H2O), and ethanol (EtOH). In this way, the objective of this work was to present the main solvents used in pressurized solvent extraction, as well as the main bioactive compounds obtained in such processes, and their consequent biological applications.
... In order to ensure high extraction efficiencies and to obtain high quality and purified extractions (Chemat et al. 2019;Yousefi et al. 2019), the design and the optimization strategies are critical. In particular, with SF extractions, the aim is on the reduction Fig. 7.1 Overview of the supercritical carbon dioxide (SF-CO 2 ) extraction process of biomolecules (Grosso et al. 2010;Sovová 2012;Huang et al. 2012;da Silva et al. 2016;Shukla et al. 2019;Yousefi et al. 2019) Perrut et al. (1997) Mass transfer modelling of apricot kernel oil extraction with supercritical carbon dioxide Özkal et al. (2005) Mathematical modelling of supercritical CO 2 extraction of volatile oils from aromatic plants Grosso et al. (2010) Prediction of isoflavone extraction from soybean meal using supercritical carbon dioxide with cosolvents Kumhom et al. 2011 Theoretical models for supercritical fluid extraction Huang et al. (2012) Kinetic study of the supercritical CO 2 extraction of different plants from the Lamiaceae family Fornari et al. (2012b) Modeling the supercritical fluid extraction of essential oils from plant materials Sovová (2012) Effects of high water content and drying pre-treatment on supercritical CO 2 extraction from Dunaliella salina microalgae: Experiments and modelling Mouahid et al. (2016) Modeling of the kinetics of supercritical fluid extraction of lipids from microalgae with emphasis on extract desorption Sovová et al. (2016) Supercritical carbon dioxide extraction of Calendula officinalis: Kinetic modeling and scaling up study López-Padilla et al. (2017) Modeling of the kinetics of supercritical fluid extraction of lipids from microalgae with emphasis on extract desorption Sovová et al. (2016) Broken-and-intact cell model for supercritical fluid extraction: Its origin and limits Sovová (2017) Supercritical carbon dioxide extraction of pomegranate (Punica granatum L.) seed oil: Kinetic modelling and solubility evaluation Natolino and Da Porto (2019) New developments in the modelling of carotenoids extraction from microalgae with supercritical CO 2 Sovová and Stateva (2019) Extraction of vetiver (Chrysopogon zizanioides) root oil by supercritical CO 2 , pressurized-liquid, and ultrasound-assisted methods and modelling of supercritical extraction kinetics Evaluation of the effects of temperature and pressure on the extraction of eugenol from clove (Syzygium aromaticum) leaves using supercritical CO 2 Frohlich et al. (2019) of extraction time, amount of solvent, energy usage, costs, waste produced and the environmental impact (Chemat et al. 2019;Yousefi et al. 2019). Figure 7.1 presents a summary of the various components of the SC-CO 2 extraction process of biomolecules. ...
... Natolino and Da Porto (2019) have applied kinetic (BIC model) and solubility (Chrastil model) modelling for the SC-CO 2 extraction of pomegranate seed oil from Punica granatum L. The "shrinking core model" was applied for the isoflavone extraction (SC-CO 2 and methanol) from soybean meal by Kumhom et al. (2011) and investigated the axial dispersion coefficient, effective diffusivity, solubility and the film "mass transfer coefficient", of which the film "mass transfer coefficient" and the solubility were found to be the most significant. Sovová (2012Sovová ( , 2017, Sovová et al. (2016) and Sovová and Stateva (2019) have described the modelling of the SF extraction process for essential oils, lipids and carotenoids, which have been readily adapted to represent extraction curves. Optimization targets (Fig. 7.1) are based on varying mainly the pressure, temperature and the flow rate of the SC-CO 2 . ...
Supercritical fluid extraction (SFE) with CO2 is a valuable alternative technique in which organic solvents are used in a series of laboratories and different industrial processes. In early research, water was used as the common solvent for the extraction process, but recently CO2 has received much attention as a supercritical fluid at different industrial levels. The industry zones, especially the rubber industries, prefer to use SFE with CO2 because this combination offers many advantages such as sample recovery, maintenance of purity factor, high selectivity in products, and a very short processing time, around 10–60 min. SFE with CO2 is very effective for reducing product contamination and improving environmental safety. CO2 as a solvent when used widely in various industrial processes and with SFE does not produce any emissions harmful to the environment. SFE technologies are used in different industrial applications that have shown substantial development in recent years. In this chapter, the role of SFE in rubber industries, and the importance of the rubber industry in Malaysia, with potential SFE applications, are summarized as possible future directions in research, especially for new investigators working in this area.
... In order to ensure high extraction efficiencies and to obtain high quality and purified extractions (Chemat et al. 2019;Yousefi et al. 2019), the design and the optimization strategies are critical. In particular, with SF extractions, the aim is on the reduction Fig. 7.1 Overview of the supercritical carbon dioxide (SF-CO 2 ) extraction process of biomolecules (Grosso et al. 2010;Sovová 2012;Huang et al. 2012;da Silva et al. 2016;Shukla et al. 2019;Yousefi et al. 2019) Perrut et al. (1997) Mass transfer modelling of apricot kernel oil extraction with supercritical carbon dioxide Özkal et al. (2005) Mathematical modelling of supercritical CO 2 extraction of volatile oils from aromatic plants Grosso et al. (2010) Prediction of isoflavone extraction from soybean meal using supercritical carbon dioxide with cosolvents Kumhom et al. 2011 Theoretical models for supercritical fluid extraction Huang et al. (2012) Kinetic study of the supercritical CO 2 extraction of different plants from the Lamiaceae family Fornari et al. (2012b) Modeling the supercritical fluid extraction of essential oils from plant materials Sovová (2012) Effects of high water content and drying pre-treatment on supercritical CO 2 extraction from Dunaliella salina microalgae: Experiments and modelling Mouahid et al. (2016) Modeling of the kinetics of supercritical fluid extraction of lipids from microalgae with emphasis on extract desorption Sovová et al. (2016) Supercritical carbon dioxide extraction of Calendula officinalis: Kinetic modeling and scaling up study López-Padilla et al. (2017) Modeling of the kinetics of supercritical fluid extraction of lipids from microalgae with emphasis on extract desorption Sovová et al. (2016) Broken-and-intact cell model for supercritical fluid extraction: Its origin and limits Sovová (2017) Supercritical carbon dioxide extraction of pomegranate (Punica granatum L.) seed oil: Kinetic modelling and solubility evaluation Natolino and Da Porto (2019) New developments in the modelling of carotenoids extraction from microalgae with supercritical CO 2 Sovová and Stateva (2019) Extraction of vetiver (Chrysopogon zizanioides) root oil by supercritical CO 2 , pressurized-liquid, and ultrasound-assisted methods and modelling of supercritical extraction kinetics Evaluation of the effects of temperature and pressure on the extraction of eugenol from clove (Syzygium aromaticum) leaves using supercritical CO 2 Frohlich et al. (2019) of extraction time, amount of solvent, energy usage, costs, waste produced and the environmental impact (Chemat et al. 2019;Yousefi et al. 2019). Figure 7.1 presents a summary of the various components of the SC-CO 2 extraction process of biomolecules. ...
... Natolino and Da Porto (2019) have applied kinetic (BIC model) and solubility (Chrastil model) modelling for the SC-CO 2 extraction of pomegranate seed oil from Punica granatum L. The "shrinking core model" was applied for the isoflavone extraction (SC-CO 2 and methanol) from soybean meal by Kumhom et al. (2011) and investigated the axial dispersion coefficient, effective diffusivity, solubility and the film "mass transfer coefficient", of which the film "mass transfer coefficient" and the solubility were found to be the most significant. Sovová (2012Sovová ( , 2017, Sovová et al. (2016) and Sovová and Stateva (2019) have described the modelling of the SF extraction process for essential oils, lipids and carotenoids, which have been readily adapted to represent extraction curves. Optimization targets (Fig. 7.1) are based on varying mainly the pressure, temperature and the flow rate of the SC-CO 2 . ...
Phenolic compounds are a group of compounds varying from complex polymerized compounds to simple phenols. They mainly contain hydroxybenzoic acids and hydroxycinnamic acids based on their type of structure. These compounds have been stated to show miscellaneous health benefits including anti-allergic, anti-cancer, anti-inflammatory, and anti-microbial activity. These health-related benefits make it important to develop techniques for their efficient extraction and quantification minimizing reduction in potency and retaining their functional value. Supercritical fluid extraction (SFE) is one of such processes offering advantages with respect to extraction time, solvent consumption, extraction yields, and reproducibility. This chapter provides the insight about the phenolic compounds and their extraction from various plant by-products by SFE.
... This was because the BICM described the situation where some of the extract was present on the outer surfaces of the particles or in cells that were broken, and part of the extract remains more deeply within pores or inside cells that were intact. 22,26 Other models used to describe the extraction kinetics for SFE process include the hot sphere diffusion model, shrinking core model, as well as theoretical models such as the diffusion layer model, desorption model, and portioning coefficient model. 22 The aim of this paper was to study the SFE of patchouli oil using a preparative-scale setup with CO 2 recycler, evaluating important variables for scale-up development, including the particle size range, pressure, and temperature. ...
... The BICM proposed by Sovová 26 has been the most adopted approach in SFE comprehensive modeling. It is devoted to matrices submitted to milling in which two distinct domains are left to be extracted: cells with broken walls and intact cells. ...
Patchouli oil is a high‐value essential oil used in cosmetic, food, and pharmaceutical industries. In this work, supercritical fluid extraction of patchouli oil with various operating process parameters (pressure, temperature, flow rate, and particle size) were studied and the results were modeled using the broken and intact cell model (BICM). From the experimental studies, it was found that the extraction rate was improved at higher pressures and flow rates, where the mass transfer resistances in the liquid and solid phase were decreased; however, the increase in temperature had an inverse effect on extraction rate and mass transfer. In the case of particle size, a moderate size of 0.3 to 0.6 mm gave the optimal extraction rate. The BICM predictions showed good agreements with experimental data and gave valuable insights regarding the mass transfer mechanism of the extraction process, including mass transfer coefficients and extraction periods governed by convection and diffusion.
... The kinetic experimental data of curves for the oils extracted from the edible insects (ZM and TM) using pressurized n-propane were described by the model proposed by Sovová [39,40]. The model considers two distinct structures in the matrices: easily accessible solute (external mass transfer) and difficult to access solute inside the matrices (mass transfer by intraparticle diffusion). ...
The profiles of oils extracted from insects have drawn attention recently in several studies because of their nutritional quality. The objective of this study was to determine how extraction using pressurized n-propane affects the composition, oxidative stability, and health indices of oils from two species of edible insect larvae, Zophobas morio (ZM) and Tenebrio molitor (TM), compared to Soxhlet extraction carried out with hexane as the solvent. The Sovová mathematical model satisfactorily represented the kinetic extraction curves. The yields obtained with n-propane were lower than those obtained with hexane via Soxhlet extraction; however, n-propane extraction required less time and resulted in oils with good oxidative stability. The extracted oils possessed intermediate characteristics between those from animals and vegetables, thereby representing an alternative source of oils and fats.
... The FER period is predominantly controlled by diffusive processes. After the oil has been removed from the open cells, a slower extraction occurs owing to the low permeability of the cell walls [49,50]. ...
In this study, oil was extracted from various types of defective coffee beans using pressurized fluids. After extraction using solvents, the residual biomass was used as a raw material in a pyrolysis process to obtain bio-oil. Palmitic and linoleic fatty acids were the predominant components of the obtained oils. When n-propane was used for pressurized extraction, the yield of coffee bean oil and the phytosterols and tocopherol content increased. The highest levels were found in oil extracted from green coffee. Increasing the solvent flow rates improved the yield of the extracted oil, while increasing the temperature had the opposite effect. Higher temperatures and pressure resulted in higher levels of phytosterols. Low extraction temperatures resulted in an oil with a higher tocopherol content. The main product of biomass pyrolysis was a bio-oil rich in caffeine and phenolic compounds. This is an effective strategy for the clean and sustainable production of bio-oil.
... ANOVA was used to analyze the OEC for run MV20 and to determine significantly different extraction zones (Table S4) according to present understanding of extraction kinetics [42]. In Zone I (< 30 min), there was a constant extraction rate (Table S4), while in Zone II (30-90 min), there was a falling extraction rate (Table S4). ...
Virgin coconut oil (VCO) was used as co-extractant with supercritical carbon dioxide (scCO2) extraction for obtaining xanthones from mangosteen pericarp (MP) without organic co-solvents. In each experiment, 120 g of dried MP that had median particle sizes of 0.85 mm was used. Extraction of MP with 40% VCO co-extractant using scCO2 (1.08 kg/h) for 420 min at 430 bar and 70 oC gave α-mangostin (32.2 mg/g), γ-mangostin (7.2 mg/g), xanthones (28.2 mg/g) in extract and an extraction yield of 31%. The role of VCO is that it promotes dissolution of xanthones and mass transfer into the scCO2 phase as elucidated with the Pardo-Castaño model. The Lentz equation was generalized in terms of (P, T, %VCO, ρCO2) to correlate all extraction curve data to within 7.4% and to estimate extraction yield crossover regions. Xanthones can be separated from mangosteen pericarp with VCO and scCO2 extraction without organic co-solvents.
... The broken and intact cell model, proposed by Sovova et, al. [13][14][15], has been the most adopted approach in SFE modelling and is devoted to matrices submitted to milling in which two distinct structures are left to be extracted: cells with broken walls and intact cells [16]. The assumption is that the extraction kinetics from broken cell is faster than that from intact cells, since cell walls introduce an additional mass transfer resistance. ...
... For PLE, the CER period provides a yield (8.51 %) more than three times the FER yield (of 2.59 %) and more than 6 times the DC yield of 1.36 %. According to Sovová [45], the high CER yield is due to easily accessible solute, from broken cell, resulting in the convection as the dominant transport phenomena. ...
Large-scale pressurized liquid extraction (PLE) data are scarce in literature, exposing the lack of information to support industrial projects. In this study, using Sida rhombifolia, the Sovová's model, developed for supercritical fluid extraction (SFE), was applied to describe PLE process, demonstrating good representation of experimental PLE data. A computational code, MatLab Simulation Extraction Models (MSEM), developed for SFE, was adapted to represent PLE mass transfer phenomena, and was able to adequately represent PLE in small and large scales. The performance was evaluated by process yield and extract quality (total phenolic content and antioxidant activity), and the results compared to Soxhlet method. The scale-up criteria consisted of constant geometric and mass transfer parameters between scales, provided statistically equivalent data. The results suggest a large-scale industrial application of a low environmental impact method, with reduced costs and high recovery of bio-based extracts, for application as ingredient for food, medicine or packaging material.
... It can be observed that the kinetic profile of the experiments fitted with the previously developed models [37,38]. Sovová [39] separated 3 stages of the SFE kinetics curves; all of them may be clearly seen in Fig. 3. The extraction rate was high in the beginning of SFE-CO 2 (stage of constant extraction rate); 68% of the yield was reached during 15 min. ...
Rowanberry (Sorbus aucuparia L.) pomace was consecutively extracted with supercritical carbon dioxide (SFE-CO2) and pressurized solvents (PLE) of increasing polarity (acetone, ethanol and water). SFE-CO2 parameters were optimized using central composite design (CCD) and response surface methodology (RSM) in order to obtain the highest lipophilic extract yield. The highest extract yield (4.80%) was obtained at 45 MPa pressure, 60 °C temperature and 180 min extraction time. The changes in SFE-CO2 parameters substantially influenced carotenoids content in the extracts; the recovery of total carotenoids was up to 49.7% of the amount determined by hexane extraction. Linoleic (59%), oleic (27%) and palmitic (9%) fatty acids were dominating in the extracted oil. PLE of SFE-CO2 residue yielded polyphenol-rich extracts (the total extraction yield was 33.1%) with strong antioxidant capacity. Rowanberry pomace should be regarded as a potential source of functional ingredients for food and other relevant uses.
... It should be noted, that although RSM suggested concrete set of optimal parameters for the highest yield, it may be observed that at 25 MPa and 50 • C almost similar yield (10.65 %), although statistically lower, was obtained. Modelling of extraction kinetics was beyond the scope of this study; however, extraction curve may be shortly commented based on the previously developed models [29,30]. It may be observed that cranberry pomace extraction curve consists of initial straight line and a transition to reaching a plateau at 30 min extraction point. ...
In this study, cranberry pomace was consecutively fractionated by supercritical carbon dioxide (SC−CO2) and pressurized liquid (PLE) extraction for the recovery of lipophilic and polyphenolic fractions. Process parameters were optimized by response surface methodology (RSM), ethanol (EtOH) and water were used in PLE. The highest yield (11.10 ± 0.15 %) in supercritical fluid extraction (SFE) was obtained at 42.4 MPa pressure, 53 °C temperature and 158 min. Linoleic (36.58 %), linolenic (32.44 %), oleic (21.79 %) and palmitic (4.36 %) acids were the major fatty acids in the oil. PLE-EtOH at optimal conditions (83 °C, 3 × 15 min) recovered 55.89 % of soluble material while PLE-H2O (130 °C, 3 × 10 min) of the residue added 6.5 % of extract. PLE-H2O extract was the strongest antioxidant, however PLE-EtOH recovered the major part of polyphenolics. PLE-EtOH effectively recovered anthocyanins and procyanidins. Peonidin-3-galactoside was the major anthocyanin, followed by peonidin-3-arabinoside. The results create a platform for’ zero waste’ processing of cranberry pomace at the industrial scale.
... However, extraction kinetics data (Fig. 3) indicates that in practice SFE-CO 2 at these conditions should not exceed 45 min, offering 98% of the total lipophilic fraction yield. This study did not aim at modeling of extraction kinetics, however, extraction curve may be explained based on the previously developed broken-and-intact cell model [45,46]. It may be observed that extraction curve (Fig. 3) consists of initial straight line and a change to the smooth curve within 15-35 min extraction. ...
Supercritical carbon dioxide extraction (SFE-CO2) was employed and its parameters (pressure, temperature, time) were optimized in order to recover valuable non-polar constituents from elderberry juice processing by-products (pomace). Several other commonly applied hexane-utilizing fractionation techniques, namely pressurized liquid (PLE), ultrasound-assisted (UAE), Soxhlet and conventional solid-liquid (SLE, maceration) extractions, were used for comparison purposes. Under optimal SFE-CO2 conditions (53 °C, 35 MPa, 45 min), 14.05 g of the lipophilic fraction was recovered from 100 g of pomace, containing health beneficial polyunsaturated linoleic (42.0%) and α-linolenic (34.1%) fatty acids. In terms of extraction yields and time, the efficiency of SFE-CO2 was generally higher as compared to conventional Soxhlet and SLE, but lower than PLE and UAE. The cyanogenic glycoside sambunigrin content in elderberry pomace, all lipophilic extracts and extraction residues was very low (6.7–76.6 ng/100 g pomace) as compared to the EFSA’s acute reference dose for HCN (20 μg/kg BW). Generally, a small portion of antioxidants was recovered from elderberry pomace after lipophilic fractionation either with supercritical CO2 or hexane (TPC: 1.5–4.7 mg GAE/g, TEAC: 0.3–11.6 mg TE/g) and defatted elderberry pomace residues retained a considerable amount (>60%) of these bioactives.
... Parameter k x a 0 Fluid phase mass transfer coefficient, 1/s k s a 0 Solid phase mass transfer coefficient, 1/s k p Volumetric partition coefficient l Characteristic length (particle volume/particle surface), for spherical particle (r/3) Void fraction Parameter related to particle geometry (spherical = 3/5, cylindrical = 1/2, slabs = 1/3) Solvent density, kg/m 3 s Solid density, kg/m 3 Dimensionless time oped based on a set of hypothesis related to heat and mass transfer phenomenon, shape and size of particle, solute-solid interaction and complexity of distribution of solute inside the raw material. Based on these assumptions, mathematical models can be classified as: broken and intact cell (BIC) model (Sovova, 1994;Sovova et al., 1994;Sovova, 2005Sovova, , 2017, desorption-diffusion-dissolution (DDD) model (Tezel et al., 2000), shrinking core model Goto et al., 1996), empirical model (Naik et al., 1989), etc. ...
The present study described the experimentation and modeling of supercritical CO2 extraction (SCE) process for papaya seed oil. Experiments were performed at various ranges of SCE parameters; temperature (303.15–368.15) K, pressure (15–35) MPa, solvent flow rate (5–25) g/min, particle size (0.2–1.4) mm and co-solvent (ethanol) flow rate as (0–20)% of CO2 flow rate. Obtained oil was analyzed through gas chromatography to estimate fatty acid concentrations. Effects of SCE parameters were investigated on the extraction yield and oleic acid concentration of papaya seed oil through central composite design. Further, two mathematical models (PM-1 and PM-2) were developed based on desorption–diffusion–dissolution (PM-1) and broken and intact cell (PM-2) mechanisms. These models were validated with the experimental data of papaya seed oil and further compared with the existing models. PM-1 proposed an equilibrium relation while assuming saturation of solvent and solute at interphase, which was successfully validated with the experimental data in the AARD range from 0.40% to 32.48%. PM-2 reduced the three zones of extraction curves to two and better fitted the experimental data of papaya seed in the AARD range from 0.45% to 35.62%. Model parameters of PM-2 were optimized through genetic algorithm.
... In the present work, the RSM-COM methodology will be applied to the SFE of E. globulus bark, for which a standard design matrix with experimental data is required. Hence, experimental results were collected from the literature, and phenomenological modeling using the Broken plus Intact Cells (BIC) approach [5,[27][28][29] was applied to the available kinetic curves in order to simulate the missing ones. To the best of our knowledge, it is the first time the whole procedure is implemented. ...
This work addresses economic and process aspects of the supercritical fluid extraction (SFE) of Eucalyptus globulus bark at industrial scale. Broken plus intact cells (BIC) model was applied to existing data and new SFE curves were simulated. Then, statistical optimization was performed with Response Surface Methodology (RSM) involving of 5 factors (pressure, temperature, cosolvent content, solvent flow rate and extraction time), and four responses: Total Yield (ηTotal), Productivity, Cost of Manufacturing (COM) and Process Energy. The design and simulation of the industrial process (Aspen Plus® software) was performed including the employment of cosolvent in the system. The best COM scored 28.1 € kgextract⁻¹, where ηTotal was 0.84-0.96 wt.%, Productivity reached 311–362 tonextractyear⁻¹, and Process Energy scored 1.46– 2.10 GJ kgextract⁻¹. These results underline that SFE provides an extended margin for trade-offs, and arguments towards the integration of SFE technology to biorefine the bark of E. globulus in pulp mills.
... In previous work, the scaling of calendula SFE was studied (L opez-Padilla et al., 2017). Nine OECs were obtained using the extraction cells of different size available in NOVALINDUS Platform (Table 1) and were represented using the Broken and Intact Cell (BIC) model (Sovova, 2017;Sovov a, 1994). With the purpose of developing a scaling correlation applicable among NOVALINDUS facilities, the regressed BIC mass transfer coefficients in the supercritical fluid phase ðk YA Þ were correlated with the CO 2 flow rate ðQ Þ. ...
The supercritical fluid extraction (SFE) of vegetal raw materials is a large field of research, innovation and entrepreneurial developments. Optimization of process conditions is usually accomplished in analytical or laboratory scale equipment. Although SFE scaling is essential to attain industrial applications, studies in the literature are scarce. In this work, the kinetic behavior of 19 overall extraction curves (OEC's), obtained by the authors in previous works using NOVALINDUS Platform SFE facilities, and a set of 39 OEC's published by other authors, were considered all together to study SFE scaling. A general trend between the solvent flow rate and Barton kinetic constant was obtained for all extraction curves included in the data base, which comprise 10 different plant materials, temperatures in the range 298–333 K, pressures of 10–30 MPa, extractor volumes from 50 to 5200 cm³, particle diameters from 250 to 1400 μm and bed porosity in the range 0.59–0.97.
A new method of seed oil extraction from X. Sorbifolia was developed using a two-stage process with supercritical CO2 (SC-CO2) and CO2-expanded ethanol (CXE). The BIC model was employed to optimize the extraction process. During the SC-CO2 extraction stage, the CLSM imaging showed rapid release of EAO from the broken cells at the edge of the particles with an oil yield of 74.11% after 4 h. The follow-up CXE extraction at 10 MPa, 333 K, and 1.5 kg/h, with a CO2 molar fraction of 0.5 resulted in 68% broken cells by SEM imaging, and obtained 18.42% of remaining HAO, with a total oil yield of 92.53%. The whole process was completed in 60% less time compared to the Soxhlet method. Lipid composition analysis found a small amount of fatty acid ethyl ester in CXE oil and a higher content of functional fatty acid nervonic acid at 4.12%.
The objective of the present work was to optimize the operating conditions (P, T cosolvent %) and to study the scale-up and the feasibility of the supercritical fluid extraction (SFE) process for polyphenols from grape pomace, the main solid byproduct of the wine industry. Pilot-scale equipment (1 L extraction vessel) was used to study the scale-up prediction for extraction vessels of 50, 100, 500, and 1000 L capacity. The adopted scale-up criteria consisted of maintaining and keeping constant the solvent mass-to-feed mass ratio and the bed geometry dimension. The results indicated an excellent predictive level obtained by Sovová's model and success of the adopted scale-up criteria. At industrial scale, yields were close to 2.3 gGAE/100 gDM, a value obtained using the pilot-scale equipment. High concentrations of high-added-value phenols such as cis-resveratrol glucoside, cis-coutaric acid, trans-p-coumaric acid, quercetin, and proanthocyanidins were found in the extract. An economic evaluation of the process indicated the feasibility of an industrial SFE plant with a capacity of 500 L for producing in 60 min an extract with an expected phenolics' concentration of approximately 133 gGAE/kg extract at an estimated 67€ /kgextract cost of manufacturing. Notably, all values are better than those currently reported in the literature.
The model of broken and intact cells was used to fit the experimental data, and it was proved to be able to describe the extraction process of tea seed oil. The extraction rate, observed through the overall extraction curves (OEC), resulted in being faster the higher the pressure whereas the temperature had less influence on the extraction kinetics. The volume mass transfer coefficients in the fluid phase (kfa0) and solid phase (ksas) were used as fitting parameters. The maximum average deviation between measured and calculated oil yield was 4.1%. Mass transfer coefficients in the fluid phase and solid phase varied between 2.40·10⁻² – 2.75·10⁻² s⁻¹ and 4.32·10⁻⁵– 6.90·10⁻⁵ s⁻¹, respectively. The outcomes of work showed the highest extraction yield (50.03±0.68% w/w) obtained at 300 bar and 40°C. Tea seed oil extracted using SC-CO2 presented higher antioxidant capacity and lower UV indices than oil extracted with n-hexane.
Supercritical fluid applications have become one of the most critical and innovative methods to be applied in Green Chemistry. In particular, with the great interest in Natural Products Chemistry that has developed in recent years due to the potential applications of biomolecules, extraction methods, which are both sensitive to the target molecule and the environment, are increasingly becoming more popular. Biomolecules such as lipids, essential oils, oleoresins, polyphenols, carotenoids, flavonoids, tocopherols, sterols and polysaccharides have various potential applications in the food industry, cosmetics and medicine. Research is focussed on the optimization of extraction parameters for obtaining high extraction yields of target molecules in short time and under mild conditions, including the development of mathematical models to describe the extraction process for improvement and development of scale-ups.
Conjugated fatty acids (CFAs) have received a deal of attention due to the increasing understanding of their beneficial physiological effects, especially the anti-cancer effects and metabolism-regulation activities. However, the production of CFAs is generally difficult. Several challenges are the low CFAs content in natural sources, the difficulty to chemically synthesize target CFA isomers in high purity, and the sensitive characteristics of CFAs. In this article, the current technologies to produce CFAs, including physical, chemical, and biotechnical approaches were summarized, with a focus on the conjugated linoleic acids (CLAs) and conjugated linolenic acids (CLNAs) which are the most common investigated CFAs. CFAs usually demonstrate stronger physiological effects than other non-conjugated fatty acids; however, they are more sensitive to heat and oxidation. Consequently, the quality control throughout the entire production process of CFAs is significant. Special attention was given to the micro- or nano-encapsulation which presented as an emerging technique to improve the bioavailability and storage stability of CFAs. The current applications of CFAs and the potential research directions were also discussed.
Experimental and modelling investigations of supercritical fluid CO 2 extraction (SC-CO 2 )of pomegranate seed oil (PSO)were performed at 240, 280 and 320 bar, and 40, 50 and 60 °C with CO 2 flow rate of 8 kg/h. A retrograde solubility behaviour was found at 50 °C and 280 bar. The model of broken and intact cells developed by Sovová adequately described SC-CO 2 processes (AARD% 0.2497-1.1691). It was demonstrated that the extraction of type A was the most suited to apply. The solubility of PSO in SC-CO 2 was estimated and modelled by Chrastil model (AARD% 0.1910-1.1821). The highest value of the oil solubility was obtained at 320 bar and 60 °C. PSO extracted by SC-CO 2 was found high-quality, evaluated in terms of antioxidant activity, and richer of punicic acid as compared to Soxhlet extracted oil.
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, optimisation, and application of green benign processes. Supercritical fluid extraction is a typical example of a novel technology for the ecologically compatible production of natural substances of high industrial potential from renewable resources such as vegetable matrices that finds extended industrial application. The present review is devoted to the stage of development of supercritical fluid extraction from vegetable material in the last 20 years. Without the ambition to be exhaustive, it offers an extended, in comparison with previous reviews, enumeration of extracted plant materials, discusses the mathematical modelling of the process, and advocates a choice for the appropriate model that is based on characteristic times of individual extraction steps. Finally, the attention is focussed on the elements of a thermodynamic modelling framework designed to predict and model robustly and efficiently the complex phase equilibria of the systems solute + supercritical fluid.
New model for supercritical fluid extraction (SFE) of natural products is presented. Like other models based on the concept of broken and intact cells, it is particularly suited to fit experimental data as it almost independently simulates two extraction periods, the first one governed by phase equilibrium and the second one governed by internal diffusion in particles. Its new feature is a detailed description of the first extraction period where different types of phase equilibrium and solvent flow patterns are taken into account. A simplified approximate form of the model is used to analyse its properties and to estimate its parameters. The number of model parameters is, in dependence on the complexity of the extraction process, 1–3 for phase equilibrium, 2–3 for mass transfer and 1 for flow pattern. The model is versatile, but, as a consequence, more data are necessary than a single extraction curve to determine its parameters in the first period. The evaluation of model parameters from extraction curves is shown on data sets from literature.
Oil from crushed almond seeds was extracted with supercritical CO2 at 350 bar and 40°C. Almond particles of three different mean sizes were tested. Extraction of the smaller particles was performed at two different solvent flow rates. Oil yields were obtained with asymptotic values at large extraction times that were close to the values obtained by Soxhlet extraction. An extraction model based on the physical evidence of broken and intact oil cells has been developed. It accounts for a former equilibrium regime and a latter finite mass transfer regime. All model parameters except the internal mass transfer coefficient and the oil concentration at solvent saturation have been determined with independent experiments. The model solution was calculated with a finite difference numerical technique. A good agreement was obtained between model curves and the experimental data for an internal mass transfer coefficient of 7.5×10-9m/s. Solute concentration profiles within the extractor were evaluated with our model.
In this work, an extraction model capable of predicting the supercritical extraction process of seed oil is presented. The model bridges the ‘broken and intact cells’ and the ‘shrinking-core’ models available in the literature: as the former, the proposed model takes into account the seed structure with the presence of oil-bearing cells; as the latter, it assumes that the particles progressively exhaust their oil content from the outside to the inside, with a core shrinking during the process. The internal mass transport coefficient is described with three alternative models: the discrete and the semi-continuous models are superior to the continuous one which undervalues the same coefficient. By means of a supercritical extraction-column model and utilizing several experimental data of supercritical grape-seed oil extraction, the value of the internal mass transport coefficient of a single layer of oil-bearing cell has been calculated: its value is roughly the same for all the experimental cases analyzed (average value: 5 × 10−8 m/s), verifying the reliability of the proposed model.Graphical abstractIn this work, an extraction model capable of predicting the supercritical extraction process of seed oil is presented. The model takes into account the seed structure: the ground seed particles are considered being composed of concentric shells consisting of oil-bearing cells that progressively exhaust their oil content. The internal mass transport coefficient is described with three alternative models: a discrete, a continuous and a semi-continuous one.Dimensionless overall mass-transfer coefficient versus the exhaustion degree of the particle for the three kinetic local models.
Extraction of oil from crushed sunflower seeds with supercritical CO2 was performed at 280 bar and 40 °C on a laboratory apparatus of 0.15 × 10-3 m3 volume and on a pilot plant of 1.5 × 10-3 m3 volume. CO2 flow rate ranged between 5 and 45 kg h-1. To study the influence of the vegetable matrix on the extraction rate, a re-extraction experiment on the extraction product was also performed on the pilot scale apparatus. A mathematical model of the supercritical extraction process was developed on the basis of the experimental evidence. The equilibrium between the solids and the fluid phase appeared to be the controlling step during the extraction process. A simplified form of a sigmoidal-shaped equilibrium curve was adopted to fit the experimental data in the whole range of CO2 flow rates explored. The meaning of this nonlinear equilibrium relationship was also discussed.
Extraction rates of substances from solid substrates by supercritical gases have been determined for coffee beans and for rape oil seeds. In case of the indestructed coffee beans an unsteady extraction process prevails, which is determined by the transport of caffeine in the solid material. An approximate solution of the differential equations and a steady state approach are applicable to the long time part of the extraction process. In case of the crushed seeds a steady state mass transfer prevails which can be calculated by mass transfer calculations.
During the extraction from milled vegetable material, the easily accessible solute from the cells opened by milling is extracted first, and the slower extraction of the solute protected by the cell walls follows. Mathematical models based on the assumption of plug flow of supercritical solvent through a fixed bed of milled material were published for both extraction periods. A new model with analytical solution was developed on the basis of these models. Extraction parameters can be evaluated by comparison of extraction curves calculated by the model with experimental data.
The model of broken and intact cells has been applied to the experimental results on oil seed supercritical extraction obtained by various authors and on several species of seeds. The results analyzed are related to various extraction apparatus ranging from very low laboratory scale to pilot plants. Moreover, a wide range of operating conditions has been covered, CO2 flow rates ranging between 1.5 and 750 g/min, extraction pressures from 240 to 550 bar, temperatures between 25 and 50°C and particle diameters from 0.25 to 4 mm have been considered. Besides, the experimental results existing in the literature, systematic scanning electron microscope (SEM) analysis have been performed on seed particles belonging to the different seed species studied, thus obtaining data about the microscopic cells that bear the oil that are characteristic of the different seed structures. Operating in this manner the differential mass balances that characterize this kind of models have been supported by microscopic information on seed structure and the number of adjustable parameters in the model has been reduced to only one, the internal mass transfer coefficient (ki). A fair good fitting of all the available experimental results has been obtained using best fit ki values ranging between 2.4×10−7 and 9.2×10−8 m/s and producing a coherent description of the extraction process. Some simulation tests have also been performed that evidenced the role of particle size and of internal mass transfer and of their interaction on the overall performance of the extraction process.
Supercritical CO2 extraction of essential oils is one of the most widely discussed applications in the supercritical fluid literature. Nevertheless, a comprehensive overview of the analytical, processing and modeling aspects has never been attempted. This is partly due to the difficulties involved in isolating essential oils from the other products which supercritical CO2 can dissolve. Moreover, only a limited number of studies provide quantitative data on the parameters governing this process.In this review, solubility data on pure compounds belonging to essential oils are analyzed. Processes proposed to isolate and fractionate essential oils by supercritical CO2 and the corresponding modelling aspects are discussed critically.
The supercritical fluid extraction of oil from milled celery seeds, using CO2 as a solvent, is presented in this study. The effect of the process parameters — pressure and temperature of extraction, particle size of celery seeds and flow rate of CO2 — on the extraction rate was examined in a series of experiments. The results indicated a significant increase in extraction rate with increase of pressure or decrease of the particle size of celery seed. A similar effect was observed with the increase of the solvent flow rate and decrease of temperature. The experimental data were described by an empirical model and two mass balance models: (1) a simplified model, which takes into account only the time dependence of the extract concentration in the two phases and is coupled with various equilibrium relationships, and (2) an extended Lack's model. The correlation results were satisfactory especially for the mass balance models, which account for the double regime — solubility and diffusion controlled regimes — of the extraction.
Grape oil was extracted with carbon dioxide at 280 bar and 40°C. Effect of milling of grape seeds, solvent flow rate and flow direction on the course of extraction was investigated. Mass transfer coefficients in the supercritical and solid phases were evaluated from extraction curves using a plug-flow model. While the assumption of plug flow was confirmed in the experiments with downflow of CO2 through the bed of milled material, the extraction with upflow of CO2 was retarded due to the natural convection. The smaller was the amount of milled seeds in the extractor and the slower was the upward flow, the more pronounced was this effect. A model with parallel plug flows was able to give good representation of the extraction curves measured with upflow.
Kriterien zur Auslegung für die Hochdruckextraktion von Naturstoffen
- E A Lack
E.A. Lack, Kriterien zur Auslegung für die Hochdruckextraktion von
Naturstoffen, TU Graz, Austria, 1985 (Ph.D. thesis).