Supercritical Acetone Research Articles

A feasible approach for the treatment of waste computer casing plastic using subcritical to supercritical acetone: Statistical modelling and optimization

Electronic waste (e-waste) usage has increased tremendously with the rapid evolution of technologies. The accumulated e-waste has now emerged as one of the crucial concerns regarding environmental pollution and human health. Recycling e-waste is commonly focused on metal recovery; nevertheless, a significant fraction of plastics (20–30%) are in e-waste. There is an indispensable need to focus on e-waste plastic recycling in an effective way, which has been mostly overlooked to date. An environmentally safe and efficient study is conducted using subcritical to supercritical acetone (SCA) to degrade the real waste computer casing plastics (WCCP) in the central composite design (CCD) of response surface methodology (RSM) to achieve the maximum oil yield of the product. The experiment parameters were varied in the temperature span of 150–300 °C, residence time between 30 and 120 min, solid/liquid ratio between 0.02 and 0.05 (g/ml), and NaOH amount from 0 to 0.5 g. Adding NaOH into the acetone helps to achieve efficient degradation and debromination efficiency. The study emphasized the attributes of oils and solid products recovered from the SCA-treated WCCP. The characterization of feed and formed products is performed with different characterization techniques such as TGA, CHNS, ICP-MS, FTIR, GC-MS, Bomb calorimeter, XRF, and FESEM. The highest oil yield achieved is 87.89% from the SCA process at 300 °C, in 120min, 0.05 S/L ratio, and 0.5 g of NaOH. GC-MS results disclose that the liquid product (oil) comprises single- and duplicate-ringed aromatic and oxygen-containing compounds. Isophorone is the significant component of the liquid product obtained. Furthermore, SCA's possible polymer degradation mechanistic route, bromine distribution, economic feasibility, and environmental aspect were also explored. This present work represents an environmentally friendly and promising approach for recycling the plastic fraction of e-waste and recovering valuable chemicals from WCCP.

Toad egg-like bismuth nanoparticles encapsulated in an N-doped carbon microrod via supercritical acetone as anodes in lithium-ion batteries

A toad egg-inspired structure comprising bismuth (Bi) nanoparticles (NPs) contained in a carbon microrod shell (Bi@C) was synthesized via the one-pot supercritical acetone (scAct) route and subsequent carbonization. During the formation of Bi NPs in scAct in the presence of nitric acid, a few decomposed acetone molecules acted as carbon sources, which generated an albumen-like N-doped carbon microrod with an average shell thickness of 38 nm and were embedded with yolk-like Bi NPs having size in the range of 30–200 nm. The densely packed Bi NPs inside the carbon micron shell resulted in a high Bi loading of 78 wt%. When utilized for Li storage, the Bi@C delivered a high reversible capacity of 337 mAh g−1 after 70 cycles at 0.05 A g−1, long-term cyclability of 0.04 decay per cycle for 1000 cycles at 1 A g−1, and high volumetric energy density of 870 mAh cm−3. The use of a mixed ether- and ester-based electrolyte in the Bi@C cell reduced the resistivity and increased the capacitive contribution, thereby resulting in a better high-rate performance and long-term stability than those obtained using conventional ester-based electrolytes.

One-pot synthesis of Bi-reduced graphene oxide composite using supercritical acetone as anode for Na-ion batteries

A high-energy–density Bi-reduced graphene oxide (Bi-RGO) composite was synthesized using the quick one-pot supercritical acetone (scACT) method. The unique deoxygenation properties and ultrafast particle formation in scACT led to the simultaneous reduction of graphene oxide to reduced graphene oxide (RGO) and the formation of heterogeneously nucleated, nanosized Bi particles 10–20 nm in size that were tightly anchored to the basal plane of RGO and homogeneously nucleated, large Bi particles 250–950 nm in size. When tested as the anode of Na-ion batteries, the Bi-RGO composite delivered the high reversible capacity of 200 mAh g−1 at 50 mA g−1 and the high volumetric capacity of 60 Ah L−1. In situ X-ray diffraction analysis revealed that the two-step alloying–dealloying Bi → NaBi → hexagonal Na3Bi or cubic Na3Bi reactions depended on the Bi particle size.

Meerwein–Ponndorf–Verley–Oppenauer Non-catalytic Reaction of Monoterpenoids in Supercritical Fluids

Abstract—The Meerwein–Ponndorf–Verley–Oppenauer non-catalytic reaction of cyclic monoterpenic ketones and alcohols (menthone, camphor, menthol, and borneol) was studied under supercritical conditions. It has been showed that the ketones can be reduced in supercritical isopropanol with high selectivity (89–98%) without any catalyst or base. At the same time, the conversion of menthone was 63% at 350°C, and that of camphor was 11% at 300°C for 5 h reaction. The conversions of menthol and borneol in the reverse dehydrogenation reaction in supercritical acetone were 34 and 22%, respectively, and the selectivities were 95 and 88%. Thermal dehydration is a main side reaction for all the reactions.

Transformation of graphene oxide in supercritical media

Graphene oxide (GO) synthesized according to the modified Hummers method was reduced by supercritical isopropyl alcohol (SCI), supercritical acetone (SCA), and supercritical water (SCW). Methods free of toxic reducing agents were developed for the graphene production. The composition, morphology, and structure of synthesized graphene were determined using CHN analysis, XRD, Raman spectroscopy, and scanning electron microscopy. The best results were acquired in the case of GO reduction in SCA and SCI at high parameters.

Recycling fiber-reinforced plastic using supercritical acetone

Carbon-fiber-reinforced plastic (CFRP) can be difficult to recycle owing to the presence of thermosetting plastics such as epoxy resin. Therefore, it is important to develop more efficient methods for recycling CFRP. Herein, we investigated the chemical recycling of CFRP containing an epoxy matrix resin via a process involving superheated and supercritical acetone. The decomposition efficiency of the epoxy resin in the CFRP at 2–14 MPa and 350 °C increased with increasing reaction time over the first 60 min, but then decreased over longer reaction times because the decomposition products carbonized. Furthermore, the decomposition efficiency increased with increasing reaction pressure and acetone density, to a maximum of 95.6% at 350 °C, 60 min, and a density of 4.35 mol/L (14 MPa). The decomposition rate of the epoxy resin in CFRP using superheated and supercritical acetone is rationalized by a surface-reaction and shrinking-core model, with large negative activation volumes.

Effects of liquefaction parameters of cellulose in supercritical solvents of methanol, ethanol and acetone on products yield and compositions

Cellulose extracted from cornstalk was liquefied in supercritical organic solvents at different liquefaction parameters. Different organic solvents (methanol, ethanol and acetone) were used to disintegrate cellulose at different temperatures (240, 260, 280, 300 and 320 °C), reaction time (0, 30, 60, 90 and 120 min) and solvents dosage (0, 80, 120, 160 and 200 mL). The results showed that similar liquefaction characteristics of cellulose were observed in three different solvents. The larger bio-oil yield and smaller residue yield obtained from cellulose liquefaction in solvents were achieved under the suitable conditions (320 °C, 160 mL, 60–90 min), respectively. And the type of solvents was the main effect to the distribution of the composition of bio-oil. The dominant constituents of bio-oil that were produced in supercritical methanol was hydrocarbon, and ketones and esters were mainly produced in supercritical ethanol, whereas ketones compounds were primarily derived in supercritical acetone.

Sustainability assessment of solvolysis using supercritical fluids for carbon fiber reinforced polymers waste management

This research aims to quantify cradle-to-gate (C2G) energy intensities, environmental, and human health burdens associated with production of one functional unit (FU) of 17 candidate supercritical fluids (SCFs) commonly proposed for depolymerizing thermoset resins contained in carbon fiber reinforced polymer (CFRP) waste. The environmental and human health burdens are calculated using TRACI 2.1 methodology. Seventeen Aspen HYSYS simulation cases and their associated GaBi product system models are developed and used to quantify energy intensities and mid-point impact categories associated with C2G production of these SCFs. A numerical example is provided to demonstrate that increasing solvolysis reaction temperature and pressure to improve thermoset resin removal efficiency also leads to SCF production energy penalty and associated increase of environmental footprint and human health burdens. The quantification results show that supercritical (SC) 1-propanol has the highest C2G production energy intensity (68.68–69.45 MJ/kg) followed by SC acetone (65.29–66.80 MJ/kg). Supercritical water (SCW) has the lowest C2G production energy intensity (9.5 MJ/kg) and lowest environmental footprint. Supercritical binary mixtures of pure solvents and water are not only more effective in reclaiming CF from CFRP waste, but also have lower C2G production energy intensities and cause lesser environmental and human health burdens compared to use of only pure solvent in their SC states. One of the core insights of this sustainability assessment highlights the need for discovering greener SCFs compared to the currently proposed ones in order to close the CFRP life cycle loop in a sustainable manner.

Effect of supercritical organic solvent on structural and optical properties of cerium doped zinc oxide aerogel nanoparticles

Cerium doped zinc oxide (2 at. %) aerogels were synthesized in supercritical methanol and different supercritical mixture solvents (methanol-acetone and methanol-ethanol). The as-elaborated samples were analyzed without any additional heat or chemical treatments by means of X-ray diffraction (XRD), scanning electron microscopy (SEM), Fourier transform infrared spectroscopy (FTIR), optical absorption, photoluminescence (PL) and TGA techniques. The XRD results show that drying in solvents mixture enhances the crystalline quality and acts as a compression agent by exerting stress on the lattice parameters. SEM images demonstrate that the agglomeration rate of aerogel particles decreases when solvents mixture is used. TGA measurements showed the high purity of the samples. FTIR results showed a shift of ZnO bond indicating that supercritical solvent influences the number of CeOZn bonds at the surface of the crystallites. UV–vis characterization demonstrates that a band-to-band transition (3.34eV) is observed only in the spectrum of the aerogel synthesized in supercritical acetone. The photoluminescence (PL) spectra exhibited different optical properties of the aerogels in violet-blue-green wavelengths region (350–530nm). A blue-green emission located at 485nm is observed only in methanol and acetone. The intensity of this band is sensitive to the supercritical organic solvent.

Degradation of carbon fiber-reinforced polymer using supercritical fluids

The degradation capability of the different supercritical fluids on carbon fiber-reinforced polymer (CFRP) was analyzed based on the impact of reaction temperature and time on degradation rate; the chain scission reaction of cross-linked network in CFRP occurred in supercritical fluid was investigated based on the analysis of liquid phase products; and the recycled carbon fiber under supercritical n-butanol and n-propanol were characterized. The results indicated that supercritical n-butanol had the excellent degradation capability on CFRP, followed by supercritical acetone. The degradation capability of supercritical ethanol and n-propanol on CFRP had little difference in temperature ranged from 280 °C to 340 °C, while supercritical n-propanol was superior to ethanol under the temperature ranged from 340 °C to 360 °C. The supercritical methanol and isopropanol were disadvantageous to CFRP degradation. The liquid phase products were main the benzene derivatives and phenol derivatives by the scission of C-C, C-O and -O- bond in linear chain segment, as well as that of C-N bond in cross-linked segment of epoxy resin cure system. In comparison with the original carbon fiber, the content of N, O and Si from the recycled carbon fiber surface decreased, while the content of C increased, and the tension strength can retain above 98 % of that of the original carbon fiber.

Optimized process for recovery of glass- and carbon fibers with retained mechanical properties by means of near- and supercritical fluids

Degradation of hybrid fiber composites using near-critical water or supercritical acetone has been investigated in this study. Process parameters such as temperature (T=260–300°C), pressure (p=60–300bar) and composite/solvent (c/s=0.29–2.1g/mL) ratio were varied to determine the effect on the resin degradation efficiency and the quality of the recovered glass and carbon fibers. Supercritical acetone at 260°C, 60bar and a c/s ratio up to 2.1g/mL could achieve nearly complete degradation of the resin. The glass fibers were recovered with up to 89% retained tensile strength compared to the virgin glass fibers. The use of near-critical water reduced the tensile strength of the glass fibers by up to 65%, whereas the carbon fibers were recovered with retained tensile strength compared to the virgin carbon fibers using water or acetone.

Catalytic liquefaction of Spirogyra gratiana transeau alga with supercritical solvents

ABSTRACTSpirogyra gratiana transeau alga was liquefied in organic solvents with and without catalyst in a cylindrical reactor at temperatures of 493, 513, and 533 K under supercritical conditions. The liquefied compounds were extracted with diethyl ether and benzene using an extraction procedure. The product yields in supercritical methanol, ethanol, and acetone were found to be 15.5, 23.7, and 34.4% at 533 K, respectively. The highest conversion to liquid products was obtained in supercritical ethanol with 10% sodium hydroxide as catalyst at the same temperature in the catalytic runs. Main chemical compounds present in the liquid product obtained in acetone without catalyst at 533 K were analyzed and characterized by gas chromatography-mass spectrometry (GC-MS).

Carbon aerogels modified with graphene oxide, graphene and CNT as symetric supercapacitor electrodes

Highly porous carbon aerogels with carbon structures additives may be attractive materials for energy storage devices. Traditional resorcinol–formaldehyde-based carbon aerogels modified with graphene, graphene oxide and CNT were compared with respect to their morphology and capacitive properties as electric double layer capacitors. Materials were prepared using drying in supercritical acetone instead of commonly used carbon dioxide. Acetone was not only used for solvent exchange but was also expelled medium at supercritical conditions. This allowed to limit materials shrinkage and enhance specific capacity that in case of CNT-modified carbon aerogel was as high as 326 F/g i.e. more than 4 times bigger than for parent carbon aerogel. The specific surface area increased from 123 to 629 m2/g. Enhancement of the specific capacity was also found for gels modified with graphene and graphene oxide. The reason of such a behavior was a difference in structure and pore size distribution of additives.

Recycling of carbon fiber reinforced plastic containing amine-cured epoxy resin using supercritical and subcritical fluids

Chemical recycling of carbon fiber reinforced plastic (CFRP) containing an amine-cured epoxy as the matrix resin was investigated with a process using supercritical alcohols or ketones as solvents. Amine-cured epoxy resin was decomposed by a supercritical solvent (methanol, 1-propanol, 2-propanol, 1-butanol, 2-butanol, tert-butanol, acetone, or methyl ethyl ketone) at 320°C in the reaction time range 6–120min. The decomposition rate depended on the solvent, and super- and subcritical acetone were ultimately selected as optimal for rapidly degrading the matrix resin. The decomposition rate of the epoxy resin using supercritical acetone was expressed by a surface reaction and shrinking core model. The recovered carbon fibers from the CFRP retained the shape of the plain fabric sheets and their tensile strength reduction was negligible.

Kinetics of Isophorone Synthesis via Self‐Condensation of Supercritical Acetone

AbstractA kinetic study on isophorone synthesis via self‐condensation of supercritical acetone catalyzed by aqueous KOH in a tubular flow reactor was conducted. The intention was to improve the isophorone selectivity, with the main approach to reduce the by‐products higher‐boiling than isophorone. A higher isophorone selectivity was obtained with increased reaction temperature. The structures of main products were determined by gas chromatography‐mass spectrometry and nuclear magnetic resonance analysis. The key reaction pathways and a corresponding kinetic model were proposed. The fitted apparent activation energies indicated the reason of isophorone selectivity improvement in that high temperature favors reversion of reversible by‐products.

Supercritical liquefaction of common reed (Phragmites australis) with alkali catalysts

ABSTRACTMilled Phragmites australis was liquefied in organic solvents with and without catalyst in a cylindrical reactor at temperatures of 533, 553, and 573 K under supercritical conditions. The liquefied compounds were extracted with diethyl ether and benzene using an extraction procedure. The product yields without catalyst in supercritical methanol, ethanol, and acetone were found to be 55.4%, 64.4%, and 73.5% at 573 K respectively. The highest conversion to liquid products was obtained in supercritical acetone with 10% sodium hydroxide as catalyst at the same temperature in the catalytic runs. Main chemical compounds present in the liquid products obtained in ethanol without catalyst and acetone with sodium hydroxide catalyst at 573 K were analyzed and characterized by gas chromatography–mass spectrometry (GC-MS).

Reductive Depolymerization of Kraft and Organosolv Lignin in Supercritical Acetone for Chemicals and Materials

AbstractKraft and organosolv lignin (KL and OL) were depolymerised efficiently in supercritical acetone in the presence of various hydrogenation catalysts (supported metal, e.g., Ni, Ru, Mo, W) and 100 bar hydrogen in the temperature range of 250–350 °C. Under the optimal conditions with Ru/C or FHUDS‐2 catalysts at 350 °C for 1 h, the yield of depolymerised Kraft lignin (DKL) or depolymerised organosolv lignin (DOL) was over 95 wt %. The weight average molecular weight of the lignin was reduced significantly from 10 200 (for KL) to 1020 g mol−1 (DKL) and from 2600 (OL) to 900 g mol−1 (DOL). The oxygen and sulfur contents of Kraft lignin were reduced by 24 and 96 %, respectively. The reductive depolymerisation treatment also decreased the amount of aliphatic hydroxyl groups and increased the amount of aromatic hydroxyl groups in the depolymerised lignin products.

A promising method for recovery of oil and potent antioxidant extracts from Pistacia khinjuk Stocks seeds

Increasing demand of chemical raw materials in the areas of energy production, nutrition, health etc. has led the researchers to find out new biomass sources and more efficient extraction strategies. In this study, one of these biomass sources, ground Pistacia khinjuk Stocks seed, was subjected to Soxhlet, static pressurized hot solvent and supercritical fluid extractions using n-hexane, acetone and methanol.Static supercritical acetone extraction conducted at 290°C exhibited the highest oil yield, with a value of 47.66±0.06%. Although static pressurized hot n-hexane extraction conducted at 120°C resulted in a 42.31±0.55% oil yield, the oil quality was better due to the lower processing temperature. Pressurized hot methanol and traditional extractions were found to be ineffective. Hence, static pressurized hot n-hexane extraction was proposed as an alternative to previous techniques.P. khinjuk oil consists mainly of 56.6% oleic acid and, in total, 83.9% unsaturated fatty acids, which makes it an important nutritional additive.Total phenolic contents of the delipidated methanolic extracts ranged between 0.15±0.05 and 2.24±0.23g gallic acid equivalent per 100g air dried sample. All extracts, except for supercritical methanol, exhibited antioxidant activity at moderate levels when compared to BHT and Trolox.

Evaluation of Eremurus spectabilis for production of bio-oils with supercritical solvents

Eremurus spectabilis samples were liquefied in organic solvents (methanol, ethanol and acetone) with (sodium hydroxide and ferric chloride) and without catalyst in a cylindrical reactor at temperatures of 270, 290 and 310°C under supercritical conditions. The effects of liquefaction parameters such as temperature, catalyst and solvent on product yields were investigated. The liquid products were extracted with diethyl ether and benzene using an extraction procedure. The product yields in supercritical methanol, ethanol and acetone were found to as 41.6%, 53.8% and 64.3% in the non-catalytic runs at 310°C, respectively. The highest conversion was obtained in supercritical acetone in the presence of ferric chloride (10%) at same temperature in the catalytic runs. The produced liquids in acetone were analyzed and characterized by elemental, Fourier transform infrared spectroscopy (FT-IR), gas chromatography–mass spectrometry (GC–MS). The liquid products (bio-oils) obtained with acetone contained various types of components including aromatics, nitrogenated and oxygenated compounds. As the bio-oils obtained exhibit high heat values, E. spectabilis is presented as a potential feedstock candidate for production of bio-fuels or valuable chemicals.

Non-catalytic liquefaction of microalgae in sub-and supercritical acetone

Abstract In the present study, a microalga ( Chlorella pyrenoidosa ) was treated in sub/supercritical acetone in the absence of catalyst by using a high pressure bath reactor. Influence of process variables such as temperature (varied from 170 to 350 °C), acetone/microalga ratio (varied from 2/2.5 to 16/2.5), and time (varied from 5 to 120 min) on the yields of product factions and properties of biocrude has been studied. Temperature was the most influential factor affecting the products yield and properties of the biocrude, and the highest biocrude yield of 60.1 wt.% was achieved at 290 °C. Addition of acetone not only promoted the conversion of microalga but also favored the biocrude yield due to the incorporation of acetone into the biocrude. Furthermore, liquefaction of microalga in acetone made the conversion milder that than of in water. The biocrude was less viscous than that of oil produced from hydrothermal liquefaction under otherwise identical reaction conditions. The biocrudes, which contained significant carbon and hydrogen than that of the original algal biomass, had higher heating values ranging from 28.7 to 37.1 MJ/kg. The most abundant compounds for the biocrude are unsaturated fatty acids (9,12,15-octadecatrienoic acid) and hydrocarbons (2-hexadecene, 3,7,11,15-tetramethyl-). CO 2 was the dominant component in the gaseous products under all experimental conditions. Deoxygenation and denitrogenation are necessary if one to expect to produce transportation fuels from this kind of biocrude.