SUPERCRITICAL FLUID EXTRACTION.pptx

SUPERCRITICAL FLUID EXTRACTION

1. SUPERCRITICAL FLUID EXTRACTION 1

2. CONTENTS INTRODUCTION SUPERCRITICAL FLUID (SCF) PROPERTIES OF SCF SUPERCRITICAL FLUID EXTRACTION (SFE) PROCESSES INSTRUMENTATION &EXTRACTION PROCESSES EQUIPMENT DEVELOPMENT ADVANTAGES DISADVANTAGES APPLICATIONS CONCLUSION 2

3. INTRODUCTION In the last century, an increasing interest has been paid to supercritical fluids as alternate solvents for the extraction of natural bioactive molecules from plants. The main reason for the interest in supercritical fluid extraction (SFE ) was the possibility of carrying out extractions at temperature near to ambient, thus preventing the substance of interest from incurring in thermal denaturation. 1980s the fundamentals of this new extraction process were already understood, but the design criteria for large-scale application of SFE were still missing. After twenty years of research and development, SFE is currently a well-established unit operation for extraction and separation. It can profitably be applied in the extraction of medicinal and aromatic plants (MAPs). 3

4. SUPERCRITICAL FLUID What is supercritical fluid? A fluid is termed as supercritical fluid when the temperature & pressure are higher than the corresponding critical values . Above the critical temperature there is no phase transition. Its physical & chemical properties are between those of pure liquid & gas. The diffusivity of SF is much higher than for a liquid . SUPERCRITICAL FLUID readily penetrates porous & fibrous solids & also has good catalytic properties. 4

5. The critical temperature is the temperature above with a distinct liquid phase cannot exist, regardless of pressure. The vapor pressure of a substance at its critical temperature is its critical pressure. Carbon dioxide is known to be the most stable and an excellent solvent compound. 5

6. PROPERTIES OF SCF liquid-like density gas-like viscosity less surface tension Low heat of vaporization High diffusivity E.g. carbon dioxide Critical temperature=31.1 Critical pressure=73.8 bar / 72.83 atm/1070.37 psi 6

7. Reasons for using co2 as solvent: Easily attains the supercritical state it is non-toxic and non-flammable inexpensive According to CHARSTIL The possibility of using SF as extraction Solvent depends on their density (1) Where, S= solute solubility ρ = solvent density a ,b,c are correlation parameter When a fluid approaches the critical conditions, its density gets closer to liquid state 7 Disappearance of phase boundary (meniscus) on heating from below critical point (top left) to above critical conditions (bottom right) S= ρ a exp ( b/ T+c )

8. SOLUTE SOLUBILITY Density of SF increases with pressure i.e. more solvent molecules per unit volume Pressure packs the solvent molecule closer and facilitate the entrapment of more solute molecule Solubility of solutes depends on parameters a,b,c In case of co2 the solubility of solute of interest of medicinal and aromatic plants applications is at best in range of 1 to 1000 by weight this is because co2 is a poor solvent even at supercritical conditions only for non-polar substances as it does not dissolves polar solvent . it is good solvent only for low molecular weight solutes. 8

9. Fugacity coefficient According to the iso-fugacity criterion applied to the substance to be extracted, Between the two phases at equilibrium (the condensed one – either solid or Liquid – and the supercritical one), we have: Yi =psat/p Ei (2) Ei = ϕ i o,v exp vs/l P – psat (3) ϕ i v RT Where y i is the mole fraction of i in the supercritical phase, ϕi o,v and ϕ i v are The fugacity coefficients of i in the standard state and in the mixture, respectively, At the process conditions, p sat is the solute saturation (or sublimation) Partial pressure (i.e. The component volatility), and v s/l is the molar volume Of the condensed phase (either solid or liquid). T is the absolute temperature And R is the universal gas constant 9

10. . E i is the so-called enhancement Factor, which accounts for the increasing solubility due to system nonidealities with respect of the ideal behaviour From Eq. 1 or Eqs . 2-3, the solubility is only one of two fundamental pieces of information that must be known in order to assess the feasibility of an SFE process for MAPs. The second one is selectivity, which is defined as the ratio of the solubility of the substance i of interest with respect to a reference substance j : α ij =si/ sj (4) Co2 is rather non-selective: when it is able to dissolve a group of similar substances (For example, in terms of carbon atoms), all of them are extracted to a similar extent, provided they have similar polarities . Therefore, it can be stated that co2 alone is not as selective as a good and pure solvent. It is also noteworthy that CO2 capacity and selectivity may be improved by using an organic solvent as the entrainer, also called the co-solvent , with the function of modifying chemical interactions between CO2 and the substance to be dissolved in it. 10

11. SFE PROCESSES Principle Feed material comes in contact with SCF the volatile substances present will partition into supercritical phase. After the dissolution of soluble material the SCF containing dissolved substances is removed from feed material . The extract is separated from SCF by means of temp&/ pressure change. The SCF is recycled. Theory Extraction of soluble solutes from solid matrix takes place by three mechanisms 1. swelling of solid phase by solvent accompanied by extraction of entrapped solute 2. reactive extraction where insoluble solutes interacts with solvent 11

12. 3. based on interactions 12 If there is no interaction between solute & solid phase Process is simple dissolution of solute in a solvent that does not dissolve solid matrix b. If there is extraction then the process is desorption.

13. instrumentation 13

14. components FLUID SOURCE ( tank of carbon dioxide) SYRINGE PUMP (pressure of 400 atm/709.27 bar/ 10 287.16 psi ) Valve to control the flow of critical fluid Exit valve Flow restrictor (depressurizes the scf) Collection device 14

15. EXTRACTION FEED VALVE SFE VESSEL PUMP 15 SCF COLLECTION VESSEL

16. PROCEDURE 1. The feed (containing solute)indicated by A comes in contact with supercritical co2 at suitable temperature & pressure. 2. COMPONENT A is selectively extracted & is recovered from supercritical solution by increasing temperature , product is recovered from separation section & supercritical fluid is recycled. Separation is achieved by two ways: 16 Temperature is constant Pressure is constant In this case product separation is achieved by depressurization & mechanical energy has to be provide to raise co2 pressure. In this case the temperature is increased & circulation of solvent can be done.

17. SEPERATION OBTAINED BY TEMPERATURE CHANGE 17

18. SEPERATION OBTAINED BY PRESSURE CHANGE 18

19. Multiple extractor, single separator scheme 19

20. Extraction yield Amount of substance of interest extracted with respect to total amount initially contained in the solid is plotted against extraction time. 20

21. EQUIPMENT DEVELOPMENT In order to design and develop an SFE process for MAPs with CO2 (possibly assisted by ethanol or water as entrainer), we need to know and optimize: The solubility of the substance of interest The selectivity of this substance with respect to others that are extracted simultaneously The extraction profiles The way to separate the substance of interest from the total extract 21

22. Basic requirements in terms of equipment are: A liquid CO2 storage tank A pump for liquid CO2 A cooler to prevent CO2 from evaporating in the pump A heat exchanger to control the temperature of CO2 entering the extractor An extraction vessel A heat exchanger to control the CO2 plus solute mixture entering the separator A separation vessel 22

23. SFE PROCESS DESIGN 23

24. SFE of MAPs is mostly an extraction operation from solid materials, which is carried out in batch or semi batch mode. Therefore, extraction vessels need to be pressurized, depressurized, opened, filled, and closed again several times per day. In order to ensure fast and safe operation procedures and reliable seals, gaskets like O-rings are useful and closure devices have been specifically designed. 24

25. ADAVANTAGES 1. Environmental improvement and reduced product contamination SFE is an alternative to liquid extraction using solvents such as hexane or dichloromethane. There will always be some residual solvent left in the extract and matrix, and there is always some level of environmental contamination from their use. In contrast, carbon dioxide is easy to remove simply by reducing the pressure, leaving almost no trace. 2. Selectivity The properties of a supercritical fluid can be altered by varying the pressure and temperature, allowing selective extraction . 25

26. 3. Speed Extraction is a diffusion -based process, with the solvent required to diffuse into the matrix, and the extracted material to diffuse out of the matrix into the solvent. Diffusivities are much faster in supercritical fluids than in liquids, and therefore extraction can occur faster. Both the higher diffusivity and lower viscosity significantly increase the speed of the extraction 26

27. DISADVANTAGES The requirement for high pressures increases the cost compared to conventional liquid extraction, so SFE will only be used where there are significant advantages. Carbon dioxide itself is non-polar, and has somewhat limited dissolving power, so cannot always be used as a solvent on its own, particularly for polar solutes. 27

28. APPLICATIONS A large number of MAPs has been considered for possible extraction by supercritical CO2. The most recent developments suitable to have industrial relevance are listed below. 28

29. RECRYSTALLIZATION OF PHARMACEUTICALS Separation of oils, flavours& medicinal components Removal of impurities from chemical products Fractionation &purification of polymers Supercritical fluid extraction has also been applied to environmental remediation such as the extraction of PCBs and other organics from water and soil. 29

30. CONCLUSION Low operating temperature preserves all natural properties of products & organic solvent free products are obtained The obvious unappealing aspect of dealing with supercritical fluids is the relatively high-pressure conditions that must be used. However, this problem has been circumvented by the use of flow reactors Hence, one can no longer claim that reactions in supercritical fluids are either too dangerous and/or expensive to carry out. Improvements in both areas have allowed the improvement of present technology. 30

31. THANK YOU 31