FR2918292A1 - Extracting natural products from plant sources using supercritical fluid, includes causing rapid, cyclic pressure variations to increase extraction yield - Google Patents

Abstract

A method for increasing the yield in the extraction of natural products (I) from plant sources (A), using a supercritical fluid (SCF) as solvent (optionally together with a cosolvent) in a thermostatted, hermetically sealed operating vessel, involves causing rapid, cyclic pressure variations in the SCF to promote the extraction of (I). A method for increasing the yield in the extraction of natural products (I) from plant sources (A) using a supercritical fluid (SCF) as solvent involves (a) filling a thermostatted, hermetically sealed vessel containing (A) with the SCF (optionally together with a cosolvent), (b) causing rapid, cyclic pressure variations in the SCF to promote the extraction of (I), (c) transferring the (I)-loaded SCF (after a specific number of cycles) into a depressurizing vessel, (d) depressurizing so that the SCF is gasified and (I) are precipitated, (e) recovering (I) and recycling the SCF and (f) repeating the process until the required amount of (I) has been recovered.

Description

The present invention relates to a novel method for:

  to improve the extraction efficiency of extraction systems using supercritical fluids (FSC), as solvents, in the industries extracting natural active substances from their plant supports 2) and to reduce their working pressure, significantly.

  These so-called supercritical fluids (FSCs) include all fluids that have a Critical Point, of which the best known, with their critical temperature Tc, are: CO2 (carbon dioxide) (Tc 304 K); N2O (nitrogen oxide) (Tc 309.5K); CH4 (methane) (Tc 190.6K), H2O (water) (Tc 647.1 K); NH3 (ammonia) (T, 405.4 K); C2H5OH (ethanol) (Tc 516.1K); C2H6 (ethane) (T 305.3K); Xe (xenon) (T 289.7K); C2H4 (ethylene) (Tc 282.3K); nC3H8 (n-propane) (Tc 369.8K); N2 (nitrogen) (Tc 126.2K); SF6 (sulfur tetrafluoride) (Tc 318.7K); According to the present invention, said new process consists in applying periodic variations, for short periods, to the working pressure to the assembly formed by said supercritical fluid (FSC) + said plant supports, being processed. This process allows an increase in the extraction yields and a significant decrease in said working pressure of said supercritical fluid (FSC). Description of drawings and illustrations. Figure 1 shows the phase diagram of Carbon Dioxide CO2 with the phase change curves that separate the different phases of CO2: a) solid state of the liquid state by the melting or solidification curve b) solid state of the gaseous state by the sublimation curve c) liquid state of the gaseous state by the vaporization or liquefaction curve.

  There is also the critical point C of CO2, where the vaporization curve disappears. This Critical Point C of CO2 is characterized by its Critical Temperature Te = 31 C (304K) and its Critical Pressure Pe = 7.3 MPa = 73 bar. There is also the Super Critical range, corresponding to temperatures above 31 ° C where, whatever the pressure applied, the CO2 only has one phase called supercritical CO2. This Super Critical Domain is the scope of this patent.

  FIG. 2 shows the curve of variation of the specific mass of supercritical CO2, ie its density, as a function of its internal pressure around its Critical point C. It can be seen that this curve is of the biphasic type with a low branch. pressures corresponding to the pressure zone of between 50 bar and 110 bar and a high pressure branch for pressures greater than 200 bar and a transition zone of between 110 bar and 200 bar.

  The low pressure branch shows that the density of supercritical CO2 is very highly compressible and in the high pressure branch, this density is practically insensitive to increases in applied pressure, which is incompressible.

  FIG. 3 is deduced from FIG. 2 and shows the variations of the Mass Volume of Supercritical CO2 as a function of pressure at 313.3 K. It shows an accentuation of the existence of the two branches of the representative curve of the effects of pressure on supercritical CO2. When this increases, the mass volume of Supercritical CO2 decreases. Here we have an empirical law for varying the pressure in a supercritical fluid (F'SC) by varying the volume of a hermetically sealed enclosure, fully filled with a fixed amount of said FSC. This seems to be a convenient way of varying the pressure applied to an FSC, within a certain pressure range, if necessary.

  Figure 4 shows the solubility of NAPHTHALENE, often considered as a model solute, in supercritical CO2, itself, considered as a model supercritical fluid (FSC), depending on the pressure thereof. The curve has, on the ordinate, the dissolved molar fraction of Naphthalene and, on the abscissa, the pressure applied to supercritical CO2. It can be seen that: a) the dissolved mole fraction of the naphthalene in the supercritical solvent CO2 increases with the pressure applied to this solvent. b) This shows that this pressure applied to this supercritical CO2 solvent makes it possible to dissolve Naphthalene more efficiently. C) the representative curve of this dissolved molar fraction of the naphthalene in supercritical CO2 solvent as a function of the internal pressure of the latter, is biphasic type, with a low pressure branch and a high pressure branch. d) We will see that the dissolution of Naphthalene is more effective in the low pressure branch than in the high pressure branch. We will see that this behavior affects the extraction efficiency of solutes by supercritical fluids (FSC), used as solvents. d) We also note that the limiting solubility of the naphthalene in the supercritical CO2 solvent (or the ultimate dissolving power thereof) is not very high with a limited dissolved mole fraction of 0.018. This requires, in such systems, to use very high static working pressure, up to 400 bar, to have a good extraction yield.

  Figure 5 is deduced from Figure 2, Figure 3 and Figure 4 and Table 2 shows the variation of the amount Q (g) of naphthalene dissolved in 1kg of supercritical CO2 solvent, as a function of pressure, at 313.3 K It is bi-phasic as in Figure 2 and Figure 4. The maximum value of Q (g) is relatively low, 54g in 1 kg of supercritical CO2 solvent. Figure 6 shows 2 leaves of Ifs, obtained using super critical CO2 (Temp = 70 C, pressure = 150 bar) with and without co-solvent. The co-solvent, here, is ethanol. The extract of Ifs obtained without co-solvent is clear whereas that obtained with co-solvent is dark green. They do not have the same compositions. In other words, the co-solvent gives selectivity to extraction by supercritical CO2.

  Figure 7 is deduced from Figure 2 and Figure 5. It shows the amount of dissolved Naphthalene in the mass volume of supercritical CO2. The curve shows the amount of Naphthalene dissolved in a kilo of Compressed Supercritical CO2. The variable parameter 30 that is not shown in this figure is the pressure applied to said supercritical CO2. Its increase causes a decrease in the mass volume of supercritical CO2 which dissolves a larger quantity of Naphthalene.

  Figure 8 shows a principle assembly, according to this patent, for separating active ingredients from their plant supports, applying the principles of extraction 4 described in this patent. It distinguishes the main elements allowing the operation of the extraction system, according to this patent. 1) The work area with: a) its biomass feed system, b) its stressed FSC feed system. c) its exhaust system for said Super Critical Fluid loaded with active ingredients, extracted from the treated plants, to the expansion chamber. 2) The said expansion chamber with its system for recovering the gaseous fluid after expansion. 3) The FSC recycling chamber containing, its recovery system of said gaseous fluid, its recycling to replenish said working chamber.

  Figure 9 shows an example of an extraction system, according to the patent, using a periodic device AQUARESE. We distinguish between: (1) AQUARESE periodic device, (2) oil-CO2 separator, (3) reaction chamber (20 liters), (4) entry and exit of yew powder, (5) CO2 input (50 bar ) passes through a heater (40 C), (P) fluid pressure measurement in the chamber, (6) cosolvent inlet, (7) enclosure heating (40 C), (8) fine filters (?), (9) Taxol-rich extract, recycling of cosolvent (11) and CO2 (12) after passage through a heat exchanger

  I) INTRODUCTION: The extraction systems of the natural active substances contained in plants, using, as a solvent, supercritical CO2, with or without the addition of co-solvents, are quite well known and used, at least on the scale pilot, in the extractive industries for cosmetology, agri-food and pharmacy. We have seen that other supercritical fluids are usable and used. These extraction systems require the use of very high static pressures, 400 bar and beyond, which is not without drawbacks and without dangers.

  In this patent, we propose a new process allowing to bring to these systems: a) an improvement of their extraction yields b) accompanied by a significant reduction of the working pressure. It is essentially a matter of applying a periodic variation, of very short periods, of the working pressure of the supercritical CO2 solvent. We propose, then, an easy method allowing to cause fast variations of the said working pressure of the said Super Critical Fluid.

  II) CRITICAL AND SUPERCRITICAL CARBON DIOXIDE. Figure 1 shows the CO2 carbon dioxide phase diagram which is considered the typical fluid for these applications. It can be seen that it exists in Solid, Liquid and Gaseous form depending on its temperature and pressure. This diagram (established at constant volume) also shows the phase change curves which separate these different phases of CO2: a) solid state of the liquid state by the melting or solidification curve b) solid state of the gaseous state by the sublimation curve. c) liquid state of the gaseous state by the vaporization or liquefaction curve. There is also the critical point C of CO2, where the vaporization curve disappears. This Critical Point C of CO2 is characterized by its Critical Temperature Tc = 31 C (304K) and its Critical Pressure Pe = 7.3 MPa = 73 bar (1 bar = 0.1 MPa = 105 Pa). For temperatures higher than Tc, we enter the Super Critical domain where the CO2 has only one phase which is the supercritical phase and this CO2 is then called supercritical CO2. This area is shown in gray in Figure 1. This is also the scope of this patent (beyond the isotemperature 313 K = 40 C.). A supercritical fluid is, therefore, a true homogeneous fluid. In particular, it must be remembered that the external pressure applied to the supercritical fluid is integrally transmitted to all the elements that are embedded therein. Therefore, we consider that the applied pressure is, also, the internal pressure of said supercritical fluid. The description above of the CO2 states is valid for all other fluids having a critical point C, mentioned above. Table 1, below, gives the comparative values of the specific mass, the viscosity and the diffusion coefficient, of a fluid in its 3 states, liquid, supercritical and gaseous: supercritical liquid gas 1000 100-800 1 103 Table 1: Compared values of specific gravity (p), viscosity (a) and mass diffusion coefficient (D) for different states of a fluid. These values show that the supercritical fluids have: (1) a lower specific gravity than in the liquid state and much stronger than in the gaseous state (2) a lower viscosity than in the liquid state and stronger that in the gaseous state, in other words, the supercritical fluid is much more fluid than the normal liquid. (3) a higher diffusion coefficient than in the liquid state. We will see that the characteristics of supercritical fluids are strongly dependent on the pressure applied to them, or its internal pressure, as defined above. Figure 2 provides an illustration. It shows the variation curve of the specific mass of supercritical CO2, ie its density, as a function of its internal pressure. It can be seen that this curve is of the biphasic type with a low pressure branch corresponding to the pressure zone comprised between 50 bars and 110 bars and a high pressure branch for pressures greater than 200 bars and a transition zone of between 11 bars. and 200 bars. The low pressure branch shows that the density of supercritical CO2 is very highly compressible and in the high pressure branch, this density is practically insensitive to the pressures of the applied pressure, incompressible donation. p (kg.m 3) a (Pa. $) D (m2.si) 7 Figure 3 deduced from Figure 2 shows the curve presenting the variation of the mass volume of supercritical CO2 as a function of its internal pressure, at T = 313.3 K. It can be seen that the volume of a kg of supercritical CO2 decreases when it is subjected to compression, from a value of 10 liters under a pressure of 50 bars to a value of 1.35 liters under a pressure of 139 bars according to Table 2, below. It shows an accentuation of the existence of the 2 branches of the curve representative of the effects of pressure on supercritical CO2:. the existence of a low pressure branch corresponding to the zone between 50 bars and 100 bars, where the supercritical CO2 is a compressible fluid. . the existence of a high pressure branch corresponding to the zone of pressures greater than 120 bar, the supercritical CO2 solvent is very incompressible. It is necessary, then, to make great efforts to reduce the volume of said supercritical CO2. In particular, the working conditions according to this branch will pose major technical problems for extraction systems using supercritical CO2. This is the case corresponding to the low pressure branch.

  III) INDUSTRIAL USE OF CRITIC AND SUPER CRITIC FLUIDS AS NEUTRAL SOLVENTS FOR THE EXTRACTION OF ORGANIC COMPOUNDS.

  A) Power of dissolution of organic compounds of supercritical fluids. The following publications: 1) Fundamentals of Supercritical Fluids, Oxford Science Publications, 1998, 210p by T. Clifford, 2) Polymer Synthesis and Processing Using Supercritical CO2, J. Mater. Science, 10, 2000, 207-234 by A. Cooper 3) Diffusion and mass transfer in supercritical fluids, AIChE J., 32 (12), 1986, 2034-2046), PG I) ebenedetti, RC Reid, 30 allow to understand how a supercritical fluid (FSC) can be used as a solvent to dissolve large organic molecules.

  B) Use of supercritical CO2 as a solvent. Figure 4 shows that supercritical CO2 is a solvent for extraction of the organic molecule Naphthalene Cio 118. It also shows that the solubility of Naphthalene in supercritical CO2 is a function of the pressure prevailing in this supercritical fluid. The naphthalene is mixed and incorporated with other solid components which are insoluble in supercritical CO2 to form, with these, a solid matrix. It involves extracting it by using supercritical CO2 as a solvent. In such an operation, the solid matrix is dried and ground to a fine powder, of the order of 200 m of grain diameter. This powder is then immersed in a supercritical CO2 solvent bath for the extraction of Naphthalene.

  The ordinate of FIG. 4 shows the dissolved molar fraction of the naphthalene (Clo H8, M = 128 g) in supercritical CO2 and the abscissa has the pressure applied to the latter, that is to say its internal pressure. This dissolved molar fraction of the naphthalene in the supercritical CO2 solution is the number obtained by dividing the number of Moles of dissolved Naphthalene in the supercritical CO2 solvent by the total number of (Moles of supercritical CO2 + dissolved Moles of Naphthalene). As these numbers have low values, 18 / 1,000 for the largest, we consider that the number of Moles of NAPHTHALENE dissolved in the solution is negligible compared to that of the Moles of supercritical CO2. Thus, the dissolved molar fraction is the ratio of the number of dissolved Moles of Naphthalene divided by the number of Moles of supercritical CO2 Table 2, below, is deduced from Figure 2 and Figure 3. Pressure (bars) 50 73 84 100 117 139 150 200 250 300 400 Mass spec 100 225 390 625 700 740 770 817 858 880 930 CO2 (g / 1) N col (1W / / q 2.3 5.11 8.9 14.2 15.9 16.82 17.5 18.57 19.5 20 21.14 V mol. (1 / Mole) 43.5 19.57 11.24 7 6.29 5.95 5.71 5.39 5.13 5.00 4.73 F. dissolved (* 10- 0.8 4.7 12.2 13.5 15.1 15.8 17.9 18.1 18.2 3) Dissolved clona - __ 41.83 173.24 214.65 254 276.5 332.40 353 364 ( m.Moles / liter 4.1 CO2) dissolved clone - .53g / 1 {535g / l} {22.17g / 1} {27.45g11} {3251g / l} {35.40g / I} {4252g / 1} {45.18g / 1} {46.6g / I} (g / liter of CO2) Mass volume 10 4.5 2.56 1.6 1.43 1.35 1.30 1.22 1.17 1.14 1.08 supercritical CO2 erg) Total ions 239 13.70 35.47 39.25 43.89 46 51.87 52.86 53.12 dissolved (g) Table 2 Table 2 gives the read values: 9 of the Pressure internal supercritical CO2,. its specific mass in (g / 1),. of the number N of Moles per liter. dissolved molar fraction F of naphthalene. the number of Moles of Naphthalene C1OH8 dissolved in 1 liter of supercritical CO2,. the calculated amount, in g / l, of dissolved naphthalene in the supercritical CO2 solvent, of the mass volume of the supercritical CO2 solvent,. of the total amount, in g, of dissolved naphthalene in 1 liter of supercritical CO2, Figure 5 shows the amount of naphthalene dissolved in one kilogram of supercritical CO2 solvent. We can see that: the solubility of the naphthalene is not total in the supercritical CO2 solvent and the amount of naphthalene dissolved in one kilogram of the supercritical CO2 solvent increases as the internal pressure of the latter increases. Thus, for a working pressure of 73 bar, this amount is 2.39 g while for 117 bar, it is 39.25 g and 53.12 g for 300 bar. Therefore, in order to be able to dissolve a large quantity of naphthalene in the supercritical CO2 solvent, in other words to have a good extraction yield with this system, it is necessary to use very high static working pressures, up to 400 bar. which is complicated, expensive to perform and dangerous to operate. . However, the maximum amount of Naphthalene dissolved in a Mole of the supercritical CO2 solvent is not large and is 53.12 g. As a result, industrial extraction systems for active substances contained in vegetable matrices, using as solvent, supercritical CO2, are functional but are not without drawbacks because of the high pressures used. These systems can be improved. This is the purpose of Part V). The description above is valid in the case of using other supercritical fluids for the extraction of other active substances contained in vegetable matrices. The improvements that will be made to systems using supercritical CO2 will be adaptable to systems using other supercritical fluids.

  C) Selectivity of supercritical solvents. The publication of J.M.H. Levelt-Sengers, U.K. Deiters, U. Klask, P. Swidersky, G.M. Schneider, Int. J. Thermophysics, 14 (4), 1993, 893-922) makes it possible to understand how co-solvents can exalt selectivity in an extraction system using supercritical fluids.

  Figure 6 illustrates this 2nd property. It shows, indeed, 2 extracts of yew leaves, obtained using supercritical CO2 (T = 70 C and P = 150 bar) with and without cosolvent. It can be seen that the extract obtained without co-solvent is practically transparent while that obtained using Ethanol as co-solvent is dark green. They do not contain, therefore, not the same products. In other words, depending on the composition of the supercritical fluid solution, active substances in different concentrations are extracted from the same plant supports. This justifies that it is necessary, in each case, to have a specific laboratory study carried out to determine the optimal parameters.

  In summary, supercritical fluids are solvents used in industrial systems for extracting active substances contained in plant matrices. Co-solvents added to supercritical fluids exalt the selectivity of these extraction systems. These systems require the use of high working pressures, up to 400 bar to obtain attractive yields.

  V) NEW EXTRACTION PROCESS USING COMPRESSION-DECOMPRESSION CYCLES OF THE WORKING PRESSURE OF SUPERCRITICAL CO2. A) A detailed study of Figure 4, Table 2 and Figure 5. We note that: 1) The curve of Figure 4 showing the molar fraction of dissolved naphthalene in the supercritical CO2 solvent, as a function of the pressure the latter is of the biphasic type, with a low pressure branch, between 70 bar and 110 bar, strongly increasing as a function of the internal pressures of supercritical CO2, a high pressure branch, more flat for pressures greater than 180 bars. and a transition zone between 110 and 180 bar. According to Table 2 and Figure 5: 35. for the low pressure branch, the dissolved amount of Naphthalene per mole of supercritical CO2 is 2.39 g at 73 bar and 39.25 g at 117 bar. Specifically, a difference of 44 bars = 117bars -73bars, allowed this system to dissolve 36.86 g of Naphthalene in 1 kilo of supercritical CO2. . for the High pressure branch, at 200 bar, the dissolved quantity is 51.87 g and for pressures greater than 300 bar, it is 53.12 g. In this case, it takes a difference of 100 bar to dissolve 1.25 g of Naphthalene in 1 kilo of supercritical CO2. Since these dissolved quantities will be recovered at the end of the operation, they therefore constitute the quantities of Naphthalene extracted by the system. The extraction efficiency of a system using the supercritical CO2 solvent shows, therefore, a greater efficiency in the operating conditions corresponding to the low pressure branch than in those of the high pressure branch. Indeed, the latter provides only a contribution equivalent to (1.25 / 53.12), less than 2.4%, of that corresponding to the conditions of the low pressure branch. It should be kept in mind that the operating conditions in the low pressure branch have material advantages, already mentioned, above.

  b) Compression of the bath "Supercritical CO2 solid matrix" 20 To go further, we will analyze the mechanisms of operation of the bath "CO2 supercritical - ~ - solid matrix containing Naphthalene", enclosed in a work enclosure, which allowed to obtain the results shown in Figures 4 and 5. We highlight the following remarkable points of this bath: 1) In this bath in equilibrium, under a certain pressure, the naphthalene is present in 2 states or 2 forms: Naphthalene dissolves in supercritical CO2 and undissolved naphthalene in supercritical CO2. For simplicity, the first is called Naphthalene D (for Dissout) and the second called Naphthalene ND (for Non Dissolved). 2) Naphthalene D molecules are chemically identical to those of Naphthalene ND because there is no formation of chemical combinations between the molecules of said supercritical CO2 and the naphthalene molecules, in these two states. So no loss of chemical identity of Naphthalene in this bath. 3) Naphthalene NI) is mixed in a solid, finely milled matrix, and the Naphthalene ND molecules are bonded together and bonded to the other insoluble materials of the solid matrix to form a structured solid. They are considered bound by different types of complex bonds, more or less strong. 4) Naphthalene D molecules are not bonded to each other and are dispersed, by thermal diffusion, homogeneously in the mass of supercritical CO2 molecules and bound to them by weak or very weak bonds. They are considered free in the supercritical CO2 solvent. 5) At a given value of the said internal pressure exerted on the set "supercritical CO2 + Naphthalene", the number of said Naphthalene D molecules is limited and is given by the representative curves of Figures 4 and 5. This curve represents an empirical law of the equilibrium between supercritical CO2 and Naphthalene. We can calculate the amount of Naphthalene D as a function of internal supercritical CO2 pressures using Table 2). 6) Thus at 73 bar, in a kilo of supercritical CO2, there is 2.39 g of Naphthalene D, consisting of free molecules, and not linked to each other or to anything. 7) Similarly, in a kilogram of supercritical CO2, for a said working pressure of 117 bars, there is 39.25 g of Naphthalene D, consisting of free molecules, and not bonded to each other or to anything. 8) In other words, an increase in said internal pressure of supercritical CO2, ie a compression thereof, from 73 bar to 117 bar, causes, in one kilo of supercritical CO2, the creation of 39.25 g ù 2 , 39g = 36.89g of Naphthalene D, consisting of new free molecules in supercritical CO2. The question is to know the origin of these new free Naphthalene molecules in supercritical CO2. Since there are no external inputs of naphthalene, the answer is that these can come only from naphthalene ND molecules which were either bound together or bound to the solid matrix by the said bonding forces providing the cohesion of this said solid matrix. Indeed, a compression exerted on the set "supercritical CO2 + Naphthalene", up to 117 bar, will produce several effects: a) It induces pressure forces that cause an influx of supercritical CO2 30 to the internal environment of the particles powder of said solid matrix, penetrating, with force, everywhere and breaking a number of said complex bonds between said solid matrix and naphthalene ND molecules and releasing them. b) It increases the solubility of Naphthalene, a manifestation of the presence of the number of liberated Naphthalene molecules. This number increases with the intensity of the compression. Under the action of thermal diffusion reported in the Table, these 13 released molecules will be distributed throughout the mass of supercritical CO2 molecules. They form new molecules of the Naphthalene D type and will enrich the supercritical CO2 in free Naphtalene molecules of the Naphthalene D type.

  Thus, a compression applied to the set "supercritical CO2 + solid matrix containing Naphthalene" causes a transformation of a number of molecules of Naphthalene ND into Naphthalene D molecules. 9) In other words, compression applied to supercritical CO2 causes the creation of new free Naphthalene D Naphthalene molecules and the corresponding destruction of Naphthalene ND-related naphthalene molecules. This analysis gives the basis of the phenomenon of extraction of the Naphthalene molecules by the supercritical CO2 solvent. This point is important.

  c) Decompression of the "supercritical CO2 solid matrix" bath 15 Now let us ask the following question: What happens if, starting from a state of equilibrium of the whole "supercritical CO2 + Naphthalene", submitted to a pressure of 117 bar, it decreases the said pressure up to 73 bar, in other words, we submit this set to decompression ?. Decompression of the whole "supercritical CO2 + naphthalene", up to 73 bar, will produce several following effects: a) induce the onset of decompression forces, acting in the opposite direction of compression, causing a decrease in the density of supercritical CO2 causing reflux of the supercritical fluid and drainage of the Naphthalene D molecules to the external medium of the powder particles, said solid matrix. B) cause a decrease in the solubility of Naphthalene, according to Figure 4, Figure 5. In other words, the amount of Naphthalene D molecules must decrease to resume its initial value, lower. More precisely, in a kilo of supercritical CO2, this quantity must fall from the value of 39.25 g to the value of 2.39 g. Thus, there are too many free Naphthalene molecules in the supercritical CO2 medium, in the new equilibrium state. Specifically, there is 36.89 grams of excess Naphthalene D in each kilo of supercritical CO2. The solution "Supercritical CO2 + Naphthalene D" becomes a supersaturated solution of Naphthalene D. Since there is no mechanism for the transformation of these Naphthalene D molecules into Naphthalene ND, Naphthalene D molecules will form Naphthalene precipitates in the supercritical CO2 bath, until the number of Naphthalene D molecules corresponds to the equilibrium value, for the pressure of 73 bar, defined by the curve representing the empirical law presented by FIGS. 4 and 5 Since the precipitated naphthalene molecules have lost the cohesive bonds which joined them together and to the solid matrix, these naphthalene D precipitates in the supercritical CO2 do not reform the starting solid matrix. So, the decompression operation of the solution "Supercritical CO2 + Naphthalene" causes the transformation of Naphthalene D molecules into a new species that we can call Naphthalene P, for precipitated Naphthalene.

  It should also be noted that Naphthalene D, Naphthalene ND and Naphthalene P are all chemically identical. To summarize, we subjected the solution "Supercritical CO2 + Naphthalene" to a compression-decompression operation and the analysis, above, makes it possible to present the following balance: a) in the initial equilibrium state, at 73 bar Starting from each kilogram of the solution "Supercritical CO2 + Naphthalene" contains 2 types of populations of Naphthalene molecules: Naphthalene D (2.39 g) and Naphthalene ND (depending on the amount of solid Naphthalene initially operator). b) After the said compression up to the value of 117 bars, each kilogram of supercritical CO2 contains Naphthalene in two forms: Naphthalene D (39.25 g) and Naphthalene ND (depending on the amount of solid naphthalene initially the operator minus 36.86 g). c) After decompression to the final equilibrium state, from the arrival at 73 bar, each kilo of the solution "Supercritical CO2 + Naphthalene" contains 3 types of populations of Naphthalene molecules: Naphthalene D ( 2.39 g), Naphthalene ND (depending on the amount of solid naphthalene initially set by the operator minus 36.86 g) and the precipitated Naphthalene which we call Naphthalene P (36.86 g). The total mass of Naphthalene in the said bath has not changed because there are no external contributions of Naphthalene in the working chamber. d) Compressive-decompression cycles of the bath "Supercritical CO2 + Naphthalene". We can say that, after a compression cycle decompression of the kilogram of supercritical CO2, Naphthalene ND lost material (36,86g of Naphthalene). In other words, this compression - decompression cycle applied to one kilogram of supercritical CO2 allowed the extraction of Naphthalene from the solid matrix.

  With a kilo of supercritical CO2, the amount extracted from naphthalene, during this cycle, is equal to 36.86 g, that is to say the amount of Naphthalene PA from this new equilibrium state of the whole. Supercritical CO2 + Naphthalene "at 73 bar, apply a new supercritical CO2 compression. The pressure forces induced by this compression will destroy new bonds among those that were not broken during the previous compression and which bind, again, naphthalene ND molecules to the structures of the solid matrix. New molecules of Naphthalene D are released and will enrich the population of Naphthalene D molecules of said bath of "supercritical CO2 + Naphthalene". Of course, the total amount of Naphthalene D follows the empirical law of Figure 5. When this supercritical CO2 working pressure reaches the value of 117 bar, the amount of Naphthalene D in one kilogram of supercritical CO2 is identical to that of the previous compression. On the other hand, this time, we have 2 sources that can supply material to form the new quantity of Naphthalene D. These 2 sources are Naphthalene ND, as previously, and Naphthalene P, itself. A priori, the contribution of each source will depend on the ease with which its naphthalene molecules dissolve in supercritical CO2. All that can be said is that the decrease of Naphthalene ND is less than in the previous case. Under these conditions, a new decompression of the said supercritical CO2 working pressure will cause a new precipitate of Naphthalene D. It is likely that this time, the amount of precipitate in a liter of supercritical CO2 is less than 36.86g . Therefore, because of the contribution of Naphthalene ND, the total amount of Naphthalene precipitated in one kilo of supercritical CO2 will range from 36.86 g to 2 * 36.86 g. The same reasoning makes it possible to predict that after a third compression-vacuum cycle, the total quantity of precipitate in a kilo of supercritical CO2 will be between 36.86 g + 3 * 36.86 g. For the 4th cycle compression of the said working pressure, each new compression-decompression cycle exerted on the supercritical CO2 causes an increase in the precipitated naphthenes extracted by the system. In other words, the number of compression-decompression cycles is a new parameter allowing the increase of the extraction efficiency. It can be understood that, thanks to this new parameter, it is possible to lower the working pressure of the system, which leads to a decrease in the extraction efficiency of each compression-decompression cycle, but, by increasing the number of cycles, it is possible to obtain and exceed the performance of traditional extraction systems working with high static pressures. It should be noted that one can not increase to infinity, the number of cycles to obtain an infinite yield. Indeed, because of the mode of formation of precipitates, described above, it can be understood that when the amount of Naphthalene P becomes important and if the dissolution conditions of the remaining Naphthalene ND, make this dissolution too low in front of the contribution of Naphthalene P, the increase in the number of compression cycles decompression of the said working pressure of supercritical CO2 no longer brings a real increase in the total amount of Naphthalene P, it is better, on the one hand, to stop for evacuate the supercritical CO2 fluid, loaded with Naphthalene D and Naphthalene P, from the working chamber to an expansion chamber, to pass the CO2 in the gaseous state to recover the charge of naphthene deposited. In practice, we will call series, the number of cycles that led to the result above. So after this first series, we introduce new supercritical CO2 into the work area to start a new series. The last round of extraction will be that there is no more Naphthalene to extract. This is the principle of the New Extraction Process using compression-decompression cycles applied to the Working Pressure of supercritical CO2. VI) Device adapted to extraction processes using supercritical CO2. Figure 7 is deduced from Figure 2 and Figure 4. The curve shows the empirical relationship between the dissolved amount of naphthalene in supercritical CO2 and the mass volume of this solvent, at the same pressure. There is a dependence between these two quantities. We can see that if a kilo of supercritical CO2 occupies a volume of 2.56 liters, it dissolves 2.56 * 5, 35 g = 13.70 g of Naphthalene D, to be compared with the case where the working pressure imposes on it to occupy a volume of 1.43 liters, the amount of dissolved naphthene passes to 1.43 * 27.45 = 39.25 g of Naphthalene D, almost 3 times more. While if the working pressure reduces this mass volume to 1.35 L, the amount of Naphthalene D increases to 1.35 * 32.51 g = 43.90 g, which is 3.2 times more. Hence a method that directly uses the data of this Figure 7 to extract Naphthalene: It will consist in using a closed cylindrical enclosure: one side with a solid bottom equipped: 35. valves to allow the introduction and exit of supercritical CO2 and openings for the introduction and removal of substrates carrying naphthalene.

  . on the other side, a sliding bottom to vary the internal volume of said cylinder without loss of supercritical CO2. The assembly must be able to withstand, without leaks or explosions, internal pressures of several hundred bars. Safety valves must not exceed a limit value of the internal pressure of said cylinder. A) Mounting using supercritical CO2 under static pressures.

  The mode of operation of this system is to introduce into said cylinder, the substrates containing Naphthalene to be extracted. The extraction work will consist in performing series, in the following manner: 1st series: a) completely fill said supercritical CO2 cylinder (at 40 C for example) and at a pressure of 50 to 70 bar. b) reduce, as much as possible, the internal volume of said cylinder. c) wait for the eventual thermal equilibrium. This supercritical CO2 is charged with Naphthalene D. d) Opening the outlet valve to send said charged supercritical CO2 to a cooled auxiliary flash tank. e) To establish conditions of temperatures and pressures making it possible to pass the critical point C to this charged supercritical CO2 and to bring it to the state of normal gaseous CO2. f) Aspirating the gas which releases, then, the naphthalene which remains deposited in said auxiliary reservoir. g) Close the communication between the 2 speakers to complete this first series. h) Introduce new supercritical CO2 into this cylinder to initiate a new extraction run. We will stop the series when there is more Naphthalene to extract. This is the operating principle of extraction systems using supercritical CO2 under high static pressures. The methods for obtaining these high static pressures and putting them in contact with the substrates, etc., are technical problems specific to each manufacturer of these systems. B) Mounting adapted to the new periodic cycle compression-decompression process of the supercritical solvent fluid. Now, let us print, if we succeed, a periodic variation of the volume of this cylinder, without leaving the supercritical domain of supercritical CO2.

  A cycle of this periodic variation of the volume of this said enclosure, without leaving the supercritical domain of said supercritical fluid, constitutes a compression-decompression cycle described above. We know that at each cycle, the said supercritical CO2 solvent is enriched with a new quantity of precipitated naphthene.

  A series consists of a number of these compression-depression cycles, without departing from the supercritical conditions of supercritical CO2. At the end of each series, the supercritical CO2 is released from the supercritical domain by sending it into the expansion chamber where it will be cooled and returned to the gaseous state. The precipitated Naphthalene is then deposited and recovered.

  The total quantity of precipitated naphthenes collected per series is dependent on the number of cycles and constitutes the desired extract and collected by series. The important point of this new process is that the number of cycles is not imposed and that one can choose to work in the conditions of the branch Low pressures where the efficiency of the process is the greatest.

  Recall that in the above process, the maximum amount of material extracted depends on the maximum value of the working pressure, which makes it necessary to work under the conditions of the low pressure branch of the empirical curves of Figure 4 or Figure 5 but , too, of the high pressure branch of these curves.

  The advantages of this new process are: 1) The extraction efficiency depends on the number of compression-decompression cycles applied to the supercritical CO2 solvent. 2) We can work at much lower working pressures, so safer for the operators. They can be below 100 bars. 3) One will choose, therefore, to work under the conditions of the low pressure branch of the empirical curve of Figure 4 or Figure 5 where the yield is maximum. 4) The frequency of compression cycles decompression of said working pressure is much faster for the low pressures used. The periods are of the order of a few seconds.

  We have seen that after a certain number of cycles, the amount of precipitate will not increase more than one cycle to the next cycle. We will consider, then, that it is the end of a series. Then, it suffices to pass the supercritical CO2 loaded with the precipitate into an auxiliary chamber where the supercritical CO2 will be returned under conditions where it will change to the state of gaseous CO 2 and the naphthalene will be deposited.

  VII) Comparison of Naphthalene extraction yields between a system using supercritical CO2 subjected to a high static pressure and a system derived from this patent.

  In order to be able to compare the yield difference between the new process and the processes using supercritical CO2 at high static pressures, let's go back to Table 2 and Figure 5. Let's look at the case of a series of the system using supercritical CO2 at 300 bar. We have seen that the amount of Naphthalene extracted per kilogram of supercritical CO2 at the end of this series is 53.12 g. Let us now examine the case of the new process with compression-decompression cycles between 73 bars and 117 bars. We have seen that the first cycle of variation of the working pressure between 73 bar and 117 bar applied to each kilo of supercritical CO2 allows to extract 36.86 g of Naphthalene, and that, for example,: 20 .after 4 cycles , a few seconds of duration per cycle, it can extract between 36.86 g and 147.44 g of Naphthalene per kilo of supercritical CO2. . after 10 cycles, of a few seconds of duration per cycle, it makes it possible to extract between 36.86 and 368.62 g of Naphthalene per kilogram of supercritical CO2. It can be seen that, potentially, the serial extraction yield of the novel process described in this patent can far exceed that of the conventional process, using supercritical CO2 under high static pressures. It is clear that, in the example described above, the choice of the range of variation of the pressures, between 73 bars and 117 bars, is arbitrary like the number of cycles of a series. With pressure variation ranges of smaller amplitudes, the yield per cycle is lower, but the series yield can be maintained or increased, with a greater number of cycles per series. With low variation amplitudes of the working pressure, the frequency of the compression-decompression cycles can be increased and more easily achieved. This shows the adaptability of the process described in this patent. When the time taken by a system to go up to 300 bar is known, it can be seen that the gain in hourly output for the extraction of the new system can be much higher than for a conventional system using high static pressures. working. The comparison made on the use of model FSC acting on a model solute, above, should be extended to the case of the use of FSCs other than supercritical CO2 for the extraction of active substances contained in substrates. For the pharmaceutical, cosmetics and food industries, besides this gain in hourly output, it is necessary to consider the difference in purchasing costs between equipment capable of supplying high-pressure supercritical fluids and the same equipment that can provide relatively low pressures. ancillary safety equipment, safety measures, The costs of this equipment providing low pressures and ancillary equipment are much lower

  VII) Application of the new process to the extraction of active substances contained in plant substrates. To demonstrate the applicability of the new process to the extraction of substances other than Naphthalene from substrates other than the solid solution Naphthalene, it is sufficient to show the equivalence of behavior and properties between Naphthalene and its solute. on the one hand and said active substances and their plant substrates. If there is equivalence, we believe that the results demonstrated above are transferable. This is the purpose of the part below. Let us see the validity of our hypotheses: a) The said active substances contained in their plant substrates that we want to extract must have been extracted by the processes using static high pressure FSCs. There is, therefore, equivalence with the solute Naphthalene and Naphthalene above and the active substances contained in their plant substrates. b) In dissolved forms in FSC, these active substances fulfill the properties described for Naphthalene D. c) The vegetable substrate, in the form of fine-grained powder, containing the said soluble active substances, is well equivalent to Naphthalene ND, since it retains, more or less strongly, the molecules (or chains of molecules) of the said active substances and does not release them spontaneously in the FSC. (It is better to use fine powder of plant substrates to have a relatively homogeneous medium.) D) When said solid plant substrate is immersed in FSC under pressure, the pressure applied to the FSC is its internal pressure, It will induce pressure forces which will have the following effects: 1) These so-called pressure forces, associated with the low viscosity of the said FSC, will allow the said FSC to penetrate more or less deeply into the internal structures of the said grains. powder of said plant substrate to try to invade more or less completely the internal space of these grains. The penetration will be deeper with each new increase or decrease of the said working pressure. 2) They will neutralize, break, more or less, more or less strong bonds that allow the trapping of said active substances in said plant substrates releasing said active substances from their plant matrices. 3) These released active substances will be subjected to thermal diffusion forces that spread them uniformly in the FSC. We find, thus, the properties described above, of the solute ND. These prerequisites being satisfied, we believe that the description concerning the extraction of Naphthalene by the new process using supercritical CO2, described in this patent, is valid for the extraction of the active ingredients entrapped or contained in vegetable matrices by the new process using supercritical CO2 or other supercritical fluids.

  VIII) Devices adapted to the new extraction process.

  Figure 8 shows the schematic of a mounting of an application of this patent. It includes: a working chamber with airtight chambers for the introduction of the biomass of medicinal plants containing active substances to extract and removal of waste and 25 other plant debris, after extraction. It communicates, on one side, with a chamber or supercritical fluid production system and on the other side with the expansion chamber. Adequate valve systems allow the opening and closing of these communications. A coupled relaxation chamber: 30. at the said work enclosure. . to a system for recovering the gaseous fluid formed, after the expansion of the charged supercritical fluid. This so-called expansion chamber is intended to receive the supercritical fluid loaded with dissolved materials, coming from said working chamber. The said supercritical fluid undergoes expansion and cooling until it passes into the gaseous state. It releases, then, said dissolved active ingredients that will be deposited in this said relaxation chamber. These deposits form the desired raw extract of the treated plants. They will be recovered by a specific system. c) The recycling chamber of the supercritical fluid will aspirate said gaseous fluid formed after said expansion, and ensure its repackaging. This reconditioned gaseous fluid will be mixed with new gas and the whole will be recycled to be brought back to the supercritical fluid state that will be delivered to the piston chamber. D) The piston chamber is a closed cylindrical chamber, with a piston sliding along its axis, so as to vary the volume in the compartment enclosing said supercritical fluid. This has the effect of varying the internal pressure to said supercritical fluid which itself is injected into said working chamber. This will cause a variation of the so-called solubility of said active plant materials of said plant being treated, in said supercritical fluid of said working enclosure, in other words, the dissolving power of said supercritical fluid thus the extraction efficiency of the system. It is clear that all communications between the various speakers of the system are provided with valve systems and other suitable security systems with adequate timings for the system to function in the sense desired by this patent. These mechanical assemblies, electrical, electronic computer can not be described in detail in the present patent. Those skilled in the art will know how to adapt the technical, technological, ... modern know-how to imagine assemblies that work in the direction intended by this patent. Figure 9. shows another schematic representation of the device using, as a periodic pressure stress generator, between 5 MPa (50 bar) and 15 MPa (150 bar) with a period of the order of one second. The method uses a system developed by the company AQUARESE for the flash hooping of mechanical elements for injection engines (1). The stress is communicated to the load to be extracted via an oil-gas separator (2). The gas part consists of CO2. The reactive chamber (3) is a doubled steel ferrule for circulating thermostatic fluid (7) ensuring the temperature control. Two upper and lower flanges allow quick disassembly if needed or replacement of the high and low filters (8). These filters prevent elements 23 of the load from going up in the separator or from going into the extraction channels (9, 10 and following). The filling of the load is done by pumping of powder (4) and the release of waste (4 ') also. The extract rich in active substance is collected in (9). The remainder of the device relates to the fluid and co-solvent recycle portion.

IX) Extension of the process.

  Carbon dioxide CO2 is the supercritical solvent most often cited and used for industrial processes thanks to its critical properties, technically, easy to produce. However, depending on the desired objectives, the present process can be envisaged under the same conditions with other supercritical solvents. Table 3 gives the critical properties of the best known. Tc (K) Pc (MPa) PC (kg.m-3) CO2 (carbon dioxide) 304 7.38 MPa 468 N20 (nitrogen oxide) 309.5 7.24 457 CH4 (methane) 190.6 4 , 59 163 H2O (water) 647.1 22.06 322 NH3 (ammonia) 405.4 11.3 235 C2H5OH (ethanol) 516.1 6.39 276 C2H6 (ethane) 305.3 4.88 203 3C2IIa. ethylene) 282.3 5.04 215 nC3H8 (n-propane) 369.8 4.25 217 SF6 (sulfur tetrafluoride) 318.7 3.76 730 N2 (nitrogen) 126.2 3.3898 314 Xe (xenon) 289, Table 5. Values of the critical parameters of different solvents Each of these solvents has a specificity related to its physicochemical properties. Water is an excellent polar solvent in the liquid and apolar state in the supercritical state. It is sometimes used for depollution operations of dangerous organic materials (poisons, chemical weapons ...). It is also used (in the form of various supercritical aqueous solutions) for the synthesis and growth of industrial crystals (quartz). The main difficulty in using water is its high temperature and critical pressure. Xenon and S E6 are two large chemical entities. The first has a high polarizability (4.01 10'24 cm) while the second is not polarizable. The use of these solvents could be advantageously envisaged for extraction operations of substances of very high added value because they are expensive compounds. N20 and alkanes are also good solvents in the supercritical state but require safety precautions for industrial use. ^ ... ^. ^ ... ^^^ ... ^^ .. ^. ^^^. ^ ... uu ^^ ... ^. ^^^^^^^^^. .. ^ 20 25 30 35

Claims (10)

  . 1) A method to improve the extraction efficiency of the processes using a supercritical fluid (SFC), with or without co-solvent, as a solvent, in the extraction industries of natural active substances from their plant supports consists of: a) to enclose, in a hermetically sealed working chamber, said plant supports containing said natural active substances to be extracted, b) to fill said said thermo-working chamber with said supercritical fluid, added or not with a co-solvent. c) to cause rapid and cyclic variations in the pressure of said supercritical fluid, which causes the extraction of said natural active substances contained in said plant supports. d). transferring, after a certain number of cycles, said supercritical fluid loaded with said natural active substances extracted into said plant supports in an expansion chamber. e) triggering said supercritical fluid charged to its gaseous state, thereby releasing said extracted natural active substances which are deposited in said expansion chamber. F) recovering said extracted natural active substances which are deposited in said expansion chamber. g) recovering said fluid released in the gaseous state of said expansion chamber and recycle it into supercritical fluid. h) starting again from point b) until obtaining the estimated quantity of said natural active ingredients.   2) The method according to claim 1, the rapid and cyclic changes in the pressure of said supercritical fluid does not remove it from the supercritical state.   3) The method according to claim 1, the rapid and cyclic changes in the pressure of said supercritical fluid can make it out of the supercritical state. 30   4) The method according to claim 1, wherein said supercritical fluid is CO2 supercritical carbon dioxide.   5) The method according to claim 1, wherein said supercritical fluid is N2O supercritical nitrogen oxide.   6) The method according to claim 1 wherein said supercritical fluid is a fluids having a critical point C such as H2O water, ammonia NH3, EthanolC2H5OH, Ethane C2H6, Ethylene C2H4, n-Propane nC3H8, SF6 sulfur tetrafluoride, N2 nitrogen, Xenon Xe, ..., fluorocarbons such as chlorodifluoromethane.   7) The method according to claim 1 wherein the cosolvent (s) can be selected from the group comprising methanol, methanol, propanol, butanol, acetone, methylene chloride, ethyl acetate.   8) The method according to claim 1 wherein the variations of the pressure of an FSC in a hermetically closed thermo-closed chamber and completely filled with said FSC, are obtained by varying the volume of said enclosure while keeping the same amount of said supercritical fluid.   9) The method according to claim 1 and claim 8, said hermetically closed thermo-closed enclosure, called piston chamber, is a cylindrical chamber closed at both ends and provided with a piston slidable along the axis. This piston separates the internal volume of this piston chamber into 2 hermetically sealed compartments. The internal volume of each of the two compartments can go from a zero value to a maximum value, depending on the position of said piston. One of the two compartments is in communication on the one hand with a source of supercritical fluid and on the other hand with said working chamber. The second compartment can be equipped in the same way and provide the same functions.   10) The method according to claims 1 and 9, the displacement of said piston is periodic, sinusoidal or not, as a function of time.