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Incensole is a macrocyclic diterpene naturally existing in the frankincense extracted from the trees of the genus Boswellia and possesses a wide spectrum of promising bioactivities. This study discusses for the first time the optimization of supercritical CO 2 extracting incensole-enriched oil from the frankincense of Boswellia papyrifera tree. The extraction parameters of temperature, pressure, and extraction time were optimized to obtain the maximum extraction yield and incensole content simultaneously using response surface methodology (RSM) and box-Behnken design, and the compounds extracted under optimal conditions were analyzed. Under the optimal conditions of a pressure of 23.0 MPa, a temperature of 40.0 °C, and an extraction period of 3.3 h, the incensole-enriched oil yield achieved 25.0%, in which incensole content of 40.5 wt% was observed and its recovery was 59.8%. The results indicate that the supercritical CO 2 extraction technique can be applied to extract incensole-enriched oil from frankincense. [Display omitted] • First-time optimization of scCO 2 extracting incensole-enriched oil from frankincense. • Optimization of oil yield and incensole content simultaneously via RSM. • Incensole recovery of 59.8% with a yield of 25.0% and incensole content of 40.5 wt%. • Characterization of compounds in supercritical CO 2 extracts from frankincense. [ABSTRACT FROM AUTHOR]

In this work, selectively extracting oleoresin from the Boswellia papyrifera frankincense resin was studied by sub- and supercritical CO 2 processes. GS-MS analysis was applied to identify the constituents of extracts. Sequential sub- and supercritical CO 2 extraction were carried out in four stages corresponding to the pressure of 10 MPa, 15 MPa, 20 MPa, and 25 MPa at fixed temperatures of 25 ℃ and 40 ℃, respectively. The obtained oleoresins were transparent with faint yellow and the yield was 23.8% and 25.1% for sub-, and supercritical extraction, respectively. Twenty-one compounds with a relative peak area of over 1% were identified. Essential oils, alcohols, hydrocarbons, diterpenes, diterpenoids, and triterpenoids are the main chemical classes, among which the relative peak area of incensole was the highest, reaching 36% in the corresponding fraction of extracts, followed by incensole acetate with relative peak area of 17–20%. These results would benefit the depth developing applications of Boswellia papyrifera frankincense resin. [Display omitted] • The frankincense resin components were extracted via subCO 2 and scCO 2 extraction. • Incensole-rich fractions were recovered by multistep CO 2 extraction. • Extraction yield raised with longer extraction time and higher pressure. • SubCO 2 showed a faster extraction speed than scCO 2. [ABSTRACT FROM AUTHOR]

Enriching natural 10 g/100 g β-carotene concentrate further is both meaningful and challenging issue. In this paper, a two-step technique has been reported to boost the concentration of natural β-carotene. Supercritical carbon dioxide (SC-CO 2 ) was utilized to preconcentrate 10 g/100 g β-carotene made from crude palm oil followed with a solvent extraction. In the first step, the β-carotene concentration was preconcentrated to 16.7 g/100 g from 10 g/100 g when pretreating conditions were as follows: extraction temperature 60 °C, extraction pressure 20 MPa, extraction time 3 h, and CO 2 flow rate 22 kg/h, In the second step, the β-carotene was boosted to 58.7 g/100 g from 16.7 g/100 g when the ratio of the preconcentrated sample and n-hexane solvent was 4:200 (g:mL), and the processing temperature was −5 °C. This is attributed to that SC-CO 2 was able selectively to remove the impurities such as oil fraction. Removing impurities enable further purification of the beta-carotene with hexane extraction. The pretreatment of removing oil fraction using supercritical (SC-CO 2 ) plays a vital role in the enrichment of β-carotene from 10 g/100 g β-carotene concentrates to higher content. [ABSTRACT FROM AUTHOR]

It is highly desirable to develop industrially scalable methods to produce defect-free graphene to meet the requirement of graphene from lab to commercial applications. In this paper, a ball-milling in series with a shear-mixing exfoliation technique in supercritical CO 2 was developed. Graphite was pretreated by ball-milling in supercritical CO 2 , and the exfoliated sheets with smaller lateral sizes and numerous crevices on their edges were elutriated into a shear-mixing vessel by supercritical CO 2 simultaneously to inhibit over crushing. Whereafter, the freshly exfoliated sheets with crevices were further exfoliated into few-layer graphene without aggregation. 90% of the obtained graphene was less than five layers, and the processing capacity of 40 g for one batch increased 40–100 times compared with the previously reported method. The electrical conductivity of 3.25 × 105 S/m of the flexible graphene film on PVDF substrate demonstrates the excellent electrical performance of the obtained graphene. [Display omitted] • Continuous graphene exfoliation system via ball-milling and shear-mixing in SC-CO 2. • SC-CO 2 ball-milling pretreatment producing numerous crevices on graphite edges. • CO 2 elutriation separation inhibits over crushing and promoting exfoliation. • High-quality graphene was produced continuously with a single batch output of 40 g. • Obtained graphene showed excellent electrical conductivity of 3.25 × 105 S/m. [ABSTRACT FROM AUTHOR]

• Supercritical CO 2 elutriation coupled with the membrane was used to sort the AgNWs. • Almost 100 % purity of AgNWs were obtained from the initially synthesized mixture. • AgNWs-based TCEs displayed a transmittance of 99.6 %, with a low haze of 0.56 %. • The flexible electrode shows well-bending performance. Silver nanowires (AgNWs) are promising materials to fabricate flexible transparent conductive electrodes (TCEs) widely used in next-generation electronic devices. However, the impurity silver particles generated during synthesis severely deteriorated the optical transmission of AgNWs meshes. Isolating AgNWs from its reacted mixture is a vexing and challenging issue but highly desirable. In this work, a facile approach of using supercritical carbon dioxide elutriation coupled with a membrane was developed to purify the AgNWs from its synthesized mixture. Almost 100 % of purified AgNWs with the yield of 56 % was obtained, from which the AgNWs-based electrodes with excellent flexibility, conductivity, and transparency were fabricated. The AgNWs-based TCEs displayed a transmittance of 99.6 % with the haze of 0.56 % at the sheet resistance of 248 Ω·sq−1 or transmittance of 96.7 % with the haze of 1.36 % at the sheet resistance of 32.5 Ω·sq−1. The sheet resistance remained almost constant after bending in 1000 cycles. [ABSTRACT FROM AUTHOR]

Exfoliation of graphite has become a popular top-down method of producing graphene. However, it is still a challenging issue to prepare purified graphene because the exfoliated graphene was usually mixed with the un-exfoliated graphite. In this work, we investigated the isolation of the graphene and graphite by using supercritical CO 2 through Computational Fluid Dynamics (CFD) simulation and experimental. The Eulerian multiphase and standard k–ε turbulence models for CFD simulation were used to explore the influences of the pressure and the velocity of supercritical CO 2 , the geometry of the separation column, and the feeding amount of the mixture on the distribution of the graphene and graphite in the column. The isolation experiments were carried out based on the CFD simulation results, and the isolated graphene was characterized by Raman spectroscopy, X-ray diffraction, atomic force microscopy, and transmission electron microscopy. The results indicate that the purified graphene sheets can be obtained by supercritical CO 2 elutriation approach and the optimal experimental conditions were consistent with that obtained by CFD simulation. The graphene was isolated with graphite completely when the volume fraction of the mixture of the graphene and graphite was <20%, the pressure and the flow rate of supercritical CO 2 were 8 MPa and 0.2 m/s, respectively. The obtained graphene sheets mainly consisted of 3–5 layers. The CFD simulation is helpful in scale-up production of purified graphene by supercritical CO 2 elutriation technique. Unlabelled Image • The graphene in the mixture of the graphene and graphite was isolated by supercritical CO 2 elutriation technique. • The influences of process parameters on separation were investigated by CFD simulation and experiment. • The CFD simulation results were consistent with that obtained by experiment. • The purified graphene sheets consisted of 3–5 layers were obtained. [ABSTRACT FROM AUTHOR]