Near-critical Propane Research Articles

Extraction of cannabinoids from hemp (Cannabis sativa L.) using high pressure solvents: An overview of different processing options

Hemp varieties of Cannabis Sativa L. contain low levels of Δ9-tetrahydrocannabinol (THC) and can be used to produce therapeutic extracts rich in cannabidiol (CBD). In this work, extracts containing up to 449 mg/g CBD were obtained from New Zealand industrial hemp varieties by extraction of flower buds with supercritical CO2. The composition of the extracts and the influence of different processing parameters (extraction pressure up to 1300 bar, use of ethanol co-solvent, decarboxylation of feed) were determined. The apparent solubility of the extract in CO2 at different pressures was measured. Extractions using near-critical propane and dimethyl-ether were also performed. Total extraction yields reached 12.0 wt% with CO2 and 8.2 wt% with propane, whereas total cannabinoid yield ranged from 51 to 100 % with CO2 and from 74 to 99 wt% with propane. Addition of 5 % ethanol co-solvent enhances the extraction of cannabinoid acid forms, as does an increase in extraction pressure.

How enzymes can remain active and stable in a compressed gas? New insights into the conformational stability of Candida antarctica lipase B in near-critical propane

Although it has been known that many of the enzymes may be instable in harsh conditions of supercritical CO2, recent experimental studies argued that the enzymes are active and stable in near-critical propane with same pressure and temperature condition. But there are no clear reasons at the molecular level for the activity and stability of the enzymes in such condition. Moreover, it is difficult to experimentally monitor the microstructure and dynamics of the enzyme in a supercritical fluid in situ. In this study the enzyme microenvironment in near-critical propane is investigated using molecular dynamic simulation. For comparison with other solvent models the enzyme was also simulated in water, hexane and supercritical CO2. We examined the overall structural properties of Candida antarctica lipase B in these four solvents and found that in supercritical CO2 there are high structural deviations from native form while in near-critical propane deviations are low and very close to those of in the mild aqueous solution and even are lower than those of in hexane. α-Helix and β-sheet contents of the enzyme remain intact in near-critical propane. These theoretical results are in agreement with experimental evidences of the stability and activity of the enzyme in near-critical propane. Moreover, it was found that the activity of the enzyme in near-critical propane can be related to the water partitioning on the surface of the enzyme. The results of this study not only confirm the reported experimental findings about enzyme stability and activity in near-critical propane, but also shed light on the structural situation of the enzyme in this condition. To the best of our knowledge, this is the first molecular dynamic simulation of a protein in a non-CO2-based compressed gas.

Decompression-Induced Encapsulation of Core-philic Solutes by Block Copolymer Micelles in Compressible Solutions: Polystyrene and Polystyrene-block-polybutadiene in Near-Critical Propane

Pressure-tuned propane capacity and selectivity for polystyrene-block-polybutadiene allows for random molecular solutions at high pressures, micellar solutions at moderate pressures, and bulk phase...

Nanostructure of Solid Precipitates Obtained by Expansion of Polystyrene-block-Polybutadiene Solutions in Near Critical Propane: Block Ratio and Micellar Solution Effects

In contrast to incompressible liquid solutions, compressible near-critical solutions of block copolymers allow for controlling rapid structure transformations with pressure alone. For example, when dissolved in near-critical propane, polystyrene-block-polybutadiene can form a random molecular solution at high pressures, a micellar solution at moderate pressures, and a solvent-free precipitate at low pressures. In contrast to the unstructured virgin copolymer, such a propane-treated precipitate rapidly self assembles toward structures characteristic of equilibrated block copolymers, such as lamellae, spheres or cylinders, which depend on the block ratio rather than on the decompression rate or temperature, at least within the rate and temperature ranges investigated in this work. At lower temperatures, however, say below 40 °C, glass transition of the styrene-butadiene diblocks can inhibit independent structure formation while crystallization of their hydrogenated-butadiene analogs can preserve the micellar-solution structure.

Effect of phase behavior in the hydrogenation of triglycerides under supercritical and near-critical propane

Sunflower oil was hydrogenated in a stirred-batch unit, using supercritical and near-critical propane as solvent, and Pd/γ-Al 2O 3 catalyst. The effect of the phase behavior on the reaction performance is analyzed. The transition from homogeneous to heterogeneous conditions showed no effect on the activity and selectivity of the reaction. These results point to an unrestricted availability of hydrogen at the catalyst surface. A comparison is made between fluid–solid mass transfer coefficients in stirred-batch and continuous fixed-bed reactors.

Stability of proteinase form Carica papaya latex in dense gases

Proteinase from Carica papaya latex was tested on its thermal stability at atmospheric pressure and in supercritical carbon dioxide, near-critical propane and dimethyl-ether. In supercritical carbon dioxide at 300 bar thermal activation of the examined proteinase was improved in the comparison to atmospheric pressure. In propane and dimethyl-ether (300 bar) activity of the examined proteinase decreased. Influence of compression/expansion cycles on residual activity of the same proteinase in supercritical carbon dioxide (300 bar and 50 °C) was studied, as well. Different ways of transition from supercritical to low-pressure-state were used which affected residual activity of the proteinase. Addition of water in the system increased activity of proteinase from C. papaya, which was incubated in supercritical carbon dioxide for 24 h. Optimum amount of water was found to be between 0.5 and 0.7 g/L.

Stability of proteinase form Carica papaya latex in dense gases

Proteinase from Carica papaya latex was tested on its thermal stability at atmospheric pressure and in supercritical carbon dioxide, near-critical propane and dimethyl-ether. In supercritical carbon dioxide at 300 bar thermal activation of the examined proteinase was improved in the comparison to atmospheric pressure. In propane and dimethyl-ether (300 bar) activity of the examined proteinase decreased. Influence of compression/expansion cycles on residual activity of the same proteinase in supercritical carbon dioxide (300 bar and 50 °C) was studied, as well. Different ways of transition from supercritical to low-pressure-state were used which affected residual activity of the proteinase. Addition of water in the system increased activity of proteinase from C. papaya, which was incubated in supercritical carbon dioxide for 24 h. Optimum amount of water was found to be between 0.5 and 0.7 g/L.

Hydrolases in supercritical CO2 and their use in a high-pressure membrane reactor.

The thermal stability and activity of enzymes in supercritical carbon dioxide (SC CO(2)) and near-critical propane were studied at a pressure of 300 bar in the temperature range 20-90 degrees C. Proteinase from Carica papaya was incubated in microaqueous SC CO(2) at atmospheric pressure in a nonaqueous system. Lipase stability in an aqueous medium at atmospheric pressure and in SC CO(2) as well as near-critical propane at 100 bar and 40 degrees C was studied. In order to investigate the impact of solvent on lipases, these were chosen from different sources: Pseudomonas fluorescences, Rhizpous javanicus, Rhizopus niveus and porcine pancreas. On the basis of our previous study on lipase activities in dense gases, a high-pressure continuous flat-shape membrane reactor was designed. The hydrolysis of sunflower oil in SC CO(2) was performed as a model reaction in this reactor. The reaction was catalyzed by the lipase preparation Lipolase 100T and was performed at 50 degrees C and 200 bar.

Solvation dynamics in a microemulsion in near-critical propane

Solvation dynamics of coumarin 343 (C343) is studied in AOT microemulsion in near-critical propane. It is observed that the solvation dynamics for a water pool of w 0=15 at 10 MPa pressure is described by bimodal behavior having a short component of 215 ps (47%) and a long component of 14 ns (53%). These components are similar to those detected for other probes in microemulsions at 0.1 MPa pressure. This indicates that the water pool is unaffected by pressure. The slow dynamics is ascribed to the restricted mobility of the water molecules confined within the pool.

High‐pressure enzymatic hydrolysis of oil

The hydrolysis of sunflower and soybean oil, catalyzed by two enzymes, non-immobilized Candida rugosa and immobilized Candida antarctica lipase, was performed at atmospheric and high-pressure. The results showed that at atmospheric pressure between 40 °C and 60 °C initial reaction rates were influenced by the temperature variation, as expected. Due to favorable physico-chemical properties of dense gases as reaction media, hydrolysis of soybean oil was performed in non-conventional solvents: in supercritical (SC) CO 2 and near-critical propane. In SC CO 2 the activity of non-immobilized Candida rugosa lipase decreased while the reaction rates of hydrolysis catalyzed by immobilized Candida antarctica lipase were 1.5-fold higher than at atmospheric pressure. However, the reaction rates for the hydrolyses catalyzed by both lipases, were much higher in propane than at atmospheric pressure.

Determination of hydrodynamic radius of AOT reverse micelles prepared in near-critical propane

The fluorescence polarization technique has been applied to determine the hydrodynamic radii of water/AOT/near-critical propane micelles ranging in water to AOT molar ratio ( W 0) from 1 to 11 at a pressure of 15 MPa and a temperature of 310 K. The effect of pressure on hydrodynamic radius has also been investigated in the pressure range of 12–38 MPa for micelles of W 0=6 and W 0=9 at 310 K. 3,4,9,10-perylene sodium tetracarboxylate, solubilized within the aqueous core of the reverse micelles, was used as a fluorescent probe. The results show that the hydrodynamic radius increased significantly with increasing W 0 value, but remained almost unchanged with increasing pressure.

Micropolarity of sodium bis(2-ethylhexyl) sulfosuccinate reverse micelles prepared in supercritical ethane and near-critical propane

The micropolarity of sodium bis(2-ethylhexyl) sulfosuccinate (AOT) reverse micelles prepared in supercritical ethane and near-critical propane has been determined in terms of a solvent polarity parameter, ET(30) values, by using absorption probes, 1-ethyl-4-methoxycarbonyl pyridinium iodide and 2,6-diphenyl-4-(2,4,6-triphenylpyridinio)-phenolate as a functions of pressure and the molar ratio of water to AOT, W0, at a constant temperature of 310 K. The micropolarity comparable to that of ethanol was observed for reverse micelles containing water of W0 = 2. The micropolarity increased with the water content and became independent of pressure after the system changed to a one-phase reverse micelle solution. For a given W0 value, no difference in the micropolarity was noticed in the micelles prepared in ethane and propane. Phase behaviour investigations have revealed that complete dissolution of 50 mM AOT occurred at 20 MPa in supercritical ethane, while a much lower pressure of 1 MPa was required in near-critical propane. The amount of water solubilized in reverse micelles formed in supercritical ethane was relatively low, reaching a W0 value of 7 at 36 MPa. In contrast, the amount of water solubilized in near-critical propane reverse micelles was W0 = 11 at a much lower pressure of 6 MPa. A higher pressure was required to solubilize larger amount of water in reverse micelles prepared in both ethane and propane.

Near-critical separation of aqueous azeotropic mixtures: process synthesis and optimization

The near critical extraction of alcohols from aqueous solutions is addressed, combining reliable thermodynamic models with robust simulation and optimization methods. Based on the process key phase equilibrium properties, a methodology for process optimization is proposed and illustrated for the extraction of ethanol using near-critical propane as solvent. Several process schemes are evaluated: (i) conventional heating, (ii) vapor recompression, and (iii) feed preconcentration. The optimal schemes and conditions for this separation problem are obtained. The process constraints are determined and removed through structural modifications of the process. The effect of the process constraints on economics and operating conditions is analyzed. The methodology results in a general process flowsheet for the near-critical separation of aqueous azeotropic mixtures.

Phase behaviour of the binary system propane and tristearin

This study reports on experimental data of binary mixtures of near-critical propane with tristearin (SSS). The measurements were carried out in a temperature region from 300 K up to 460 K and pressures up to 16 MPa were applied. Various two- and three-phase equilibria, including those in the presence of solid tristearin, have been determined. This study was part of an investigation to test the possibility of describing the phase behaviour of propane with edible oils and fats in terms of a limited number of ‘key-binaries’. As an additional feature, this research also contributes to our knowledge of extraction and/or fractionation of edible oils and fats, using propane as the near-critical solvent.

Phase Behavior of Lecithin–Water Mixtures inn-Hexane and Near-Critical Propane: Influence of Cosurfactants Caprylic Acid and 1-Butanol

The phase behavior of mixtures of water and lecithin in near-critical propane andn-hexane was studied as a function of the overall water concentrationcoverall(water) with and without added cosurfactant. Six different equilibria were identified inn-hexane with increasingcoverall(water) in the absence of cosurfactant, whereas only two different equilibria were observed in the presence of one mole of caprylic acid per mole lecithin. Using near-critical propane as the continuous phase solvent, the phase behavior could be varied as a function of pressure. Cloud-point pressures were determined with and without caprylic acid. An unusual behavior was found for the cloud-point pressure as a function ofcoverall(water). In the absence of cosurfactant, the formation of a highly viscous organogel was observed at low overall water concentrations. This gel formation was reversible and pressure dependent.

Rotational Reorientation Dynamics of Aerosol-OT Reverse Micelles Formed in Nearcritical Propane

The rotational reorientation kinetics of two fluorescent solutes (rhodamine 6G, R6G, and rhodamine 101, R101) have been determined in sodium bis(2-ethylhexyl) sulfosuccinate (Aerosol-OT, AOT) reverse micelles formed in liquid and nearcritical propane. We show that the amount of water loading ([water]/[AOT], R), continuous phase density, and temperature all influence the solute rotational dynamics. In all cases, the decay of anisotropy data (i.e., frequency-dependent differential polarized phase angle and polarized modulation ratio) are well-described by a bi-exponential decay law. We find that the faster rotational correlation times are similar to but slightly less than the values predicted for an individual AOT reverse micelle rotating in propane. The recovered rotational correlation times range from 200 to 500 ps depending on experimental conditions. This faster rotational process is explained in terms of lateral diffusion of the fluorophore along the water/headgroup interfacial region within the reverse micelle. The recovered values for the slower rotational correlation times range from 7 to 18 ns. These larger rotational reorientation times are assigned to varying micelle-micelle (i.e., tail-tail) interactions in the low-density, highly compressible fluid region. We also quantify the contribution of the reverse micellar “aggregate” to the total decay of anisotropy.

Extraction of Bioactive Sesquiterpene Lactones from Magnolia grandiflora Using Supercritical Carbon Dioxide and Near-Critical Propane

The bioactive sesquiterpene lactones parthenolide and costunolide, as well as the tricyclic sesquiterpene cyclocolorenone, were extracted from the leaves of Magnolia grandiflora by supercritical extraction with carbon dioxide and by near-critical extraction with propane. Parthenolide, costunolide, and cyclocolorenone in the extracts were identified by 1 H NMR and quantified by HPLC. Results indicate that supercritical carbon dioxide selectively removed parthenolide, costunolide, and cyclocolorenone when compared to standard liquid dichloromethane or near-critical propane extraction. HPLC traces show that the carbon dioxide extract is virtually clean of any chlorophyll or fatty material peaks which hinder isolation of these chemicals

Probing the internal dynamics of reverse micelles formed in highly compressible solvents: aerosol-OT in near-critical propane

ADVERTISEMENT RETURN TO ISSUEPREVArticleNEXTProbing the internal dynamics of reverse micelles formed in highly compressible solvents: aerosol-OT in near-critical propaneJing Zhang and Frank V. BrightCite this: J. Phys. Chem. 1992, 96, 22, 9068–9073Publication Date (Print):October 1, 1992Publication History Published online1 May 2002Published inissue 1 October 1992https://doi.org/10.1021/j100201a070RIGHTS & PERMISSIONSArticle Views74Altmetric-Citations21LEARN ABOUT THESE METRICSArticle Views are the COUNTER-compliant sum of full text article downloads since November 2008 (both PDF and HTML) across all institutions and individuals. These metrics are regularly updated to reflect usage leading up to the last few days.Citations are the number of other articles citing this article, calculated by Crossref and updated daily. Find more information about Crossref citation counts.The Altmetric Attention Score is a quantitative measure of the attention that a research article has received online. Clicking on the donut icon will load a page at altmetric.com with additional details about the score and the social media presence for the given article. Find more information on the Altmetric Attention Score and how the score is calculated. Share Add toView InAdd Full Text with ReferenceAdd Description ExportRISCitationCitation and abstractCitation and referencesMore Options Share onFacebookTwitterWechatLinked InReddit PDF (728 KB) Get e-Alerts

Fractionation of high density polyethylene in propane by isothermal pressure profiling and isobaric temperature profiling

High density polyethylene was fractionated with respect to molecular weight and dissolution temperature in supercritical and near-critical propane. Isothermal pressure profiling in the liquid (polymer)-super-critical fluid regime resulted in 14 fractions with narrow polydispersity. The liquid-crystal phase separation technique of Pennings was extended from organic solvents to compressed propane for fractionation with respect to dissolution temperature and therefore crystallizability in the semicrystalline solid-supercritical fluid regime by isobaric temperature profiling above the second critical endpoint pressure. The influence of molecular weight, crystalline content, and mass transfer limitations is discussed. The authors believe this is the first time a crystal phase fractionation has been reported in supercritical fluids. The process is suggested as an alternative to temperature rising elution fractionation (TREF) developed to fractionate linear low density polyethylene on the basis of short chain branching.

FT-IR investigation of the partitioning of sodium bis(2-ethylhexyl) sulfosuccinate between an aqueous and a propane phase

The partitioning of the surfactant sodium bis(2-ethylhexyl) sulfosuccinate (AOT) from a buffered aqueous phase into a near-critical propane phase was investigated by using Fourier transform infrared spectroscopy. The partitioning of AOT is shown to be dependent upon the fluid pressure as well as upon the molar water-to-surfactant ratio, W. The uptake of water into the propane microemulsion phase coincides with the partitioning of AOT. The phase behavior of this system appears to be controlled by the attractive interactions between droplets in the microemulsion phase, as well as from limitations upon the curvature of the interfacial surfactant layer. Potential application of these systems for separations are discussed.