Supercritical Ethanol Research Articles

Effect of thermal treatment process on the structure of C/SiO2 composite aerogels

Abstract Carbon/silica composite (C/SiO2) aerogels were synthesized by using tetraethyl orthosilicate, 3-aminopropyltriethoxysilane, trimethylchlorosilane, resorcinol as the silicon and carbon sources, and ethanol as solvent, via the sol–gel process followed by supercritical ethanol drying and thermal treatment. The influence of thermal treatment process on the structure of C/SiO2 composite aerogels was analyzed mainly and measured by Fourier transform infrared spectrometer, X-ray diffraction and nitrogen adsorption–desorption analysis. The results showed that the optimum thermal treatment temperature of C/SiO2 composite aerogels was 1,300°C. With the increase in the thermal treatment time, the linear shrinkage of the composite aerogels increased gradually, and the pore volume, average pore diameter and specific surface area of the composite aerogels increased first and then decreased.

Catalytic Wood Fractionation into Chemicals in Supercritical Ethanol and n-Heptane: Potential and Limitations

Direct selective wood fractionation into chemicals is an approach that has attracted recent attention. The application of sub- and supercritical (SC) alcohols to fractionate wood into solid cellulose and liquefy phenolic monomers is a process now widely known as “lignin first”. It is justified to study the potential of other SC organic solvents of variable polarities. Herein, we compare the abilities of SC ethanol and SC n-heptane to fractionate pine wood near their critical point. While near-critical ethanol has more affinity for lignin fraction, we show that near-critical n-heptane has preference for carbohydrate deconstruction. If SC ethanol favors biooil formation which contains important ethyl/ethoxy groups, the alkane greatly favors solid carbon products. The impact of addition of heterogeneous catalysts (acid, basic and Cu-based catalysts) on wood fractionation and light chemicals formation was investigated deeply in SC ethanol. In SC ethanol, catalysts favor light liquid products such as esters at the expense of biooil with a total oxygenates yield of 33 wt% relative to carbohydrates over β zeolite. However, we show that depending on the catalysts’ nature, wood components fractionation was completely changed, and this is particularly true with solid acid catalysts which promote cellulose deconstruction and the formation of solid carbon products. It is proposed that liquid products’ accumulation in the autoclave, in particular water, is at the origin of the wood fractionation changes which preclude its control by the choice of the SC organic solvent and conditions. Moreover, all the catalysts underwent severe leaching, which also contributed to the wood component fractionation changes.

Efficient liquefaction of Kraft lignin over N-doped carbon supported size-controlled MoC nanoparticles in supercritical ethanol

It is a great challenge to cleave CO bonds in lignin during liquefaction of Kraft lignin into fuels as the bond is characterized by high energy, and the complex composition of lignin oil makes it difficult to separate and purify monomers. Hence, there is an urgent need for highly selective catalysts that can help in the cleavage of these high-energy bonds. We aimed to develop effective and inexpensive catalysts for the synthesis of guaiacol compounds. Liquefaction of Kraft lignin was achieved by using a novel N-doped carbon-supported MoC nanoparticle catalyst (MoC-x@NC, x = 0.5, 1, and 1.5). 77.58 wt% of guaiacol compounds was present in 41.5 wt% of lignin oil after liquefaction of lignin. 2-phenoxy-1-phenylethanol was used as model compound to confirm the efficient CO bond-breaking properties of MoC-x@NC. Additionally, it was observed that high-valence molybdenum and metal phosphate on the surface of catalysts promoted the conversion of benzene alcohols to phenols which further enhanced the content of the guaiacol compounds. N-doped graphitic carbon substrate helps in the alkylation of guaiacol into 4-alkyl guaiacol in the presence of alkyl fragments in ethanol.

Selective catalytic depolymerization of lignin to guaiacols over Mo-Mn/sepiolite in supercritical ethanol

Lignin catalytic depolymerization (LCD) into liquid fuels and aromatic chemicals in supercritical ethanol systems is one of the most effective strategies for efficient utilization of biomass resources. In this study, a series of sepiolite (SEP) supported Mo-Mn catalysts with different Mn/Mo ratios were prepared and applied to LCD. Experimental results for lignin and 2-phenoxy-1-phenyl ethanol (PP) confirmed that Mo/Mn species promoted the breakage of β-O-4 bonds, Mn additive effectively inhibited the alkylation of intermediates, and Mn/Mo ratios distinctly affected the yields of lignin oil (LO) and guaiacols. All as-prepared Mn-Mo/SEP catalysts achieved approximately 100 % conversions of lignin and PP. Various characterization results demonstrated that Mn/Mo ratios could regulate the particle sizes of metal oxides as well as the concentration of oxygen vacancies (OV) and surface acidic sites. In 3Mn1Mo/SEP, the appropriate interaction among SEP, Mn and Mo species reduced the particle sizes of metal oxides and rendered the crystalline phase structure in a relatively complex state, which undoubtedly generated massive steps/corners on its surface and then enhanced the hydrogenation reaction. Furthermore, the 3Mn1Mo/SEP contained many OV and suitable distribution of Lewis and Brønsted acid sites, which facilitated the adsorption of oxygen-containing intermediates and further hydrogenation and deoxygenation. Therefore, 3Mn1Mo/SEP achieved 45.7 % of LO yield with an HHV of 32.31 MJ/Kg and the highest selectivity to phenols (85.61 %) and yield of guaiacols (308.9 mg/g lignin). In addition, the plausible reaction network for LCD was proposed based on the results of experiments and characterizations.

Construction of the novel polyimide/Bi2MoO6-OVs p-n type heterojunction aerogel photocatalysts to enhance the photodegradation on organic pollutants driven by the internal electric field

To photodegrade the organic pollution, the Polyimide/Bi 2 MoO 6 -OVs p-n type aerogel heterojunction photocatalysts with rich pore structure and large surface area were synthesized by chemical amide reaction and supercritical ethanol drying technique successfully. The introduction of oxygen vacancies can be beneficial to the activation of molecular oxygen, which can inhibit photo-generated charge recombination to improve photocatalytic efficiency. Furthermore, the formation of Mo-N chemical bond between the coordination of N atoms of heptazine units and Mo atoms of Bi 2 MoO 6 is confirmed by structure analysis. And the ability of the heterojunction photocatalyst to degrade RhB is improved significantly, which is due to photogenerated electron-hole pairs can be quickly separated under the internal electric field within the space charge region under visible light. Simultaneously, the SEM images show the flocculent PI polymer is coated on the surface of flower-like Bi 2 MoO 6 -OVs microsphere, which can expand the light absorption range and enlarge the surface area. This work provides an innovative perspective to construct polymer aerogel with inorganic materials heterojunction photocatalyst with superior photocatalytic activity. • The introduction of oxygen vacancies to Bi 2 MoO 6 is beneficial to the activation of molecular oxygen. • The flocculent PI polymer coated on the surface of flower-like Bi 2 MoO 6 -OVs microsphere is prepared. • The Mo-N chemical bond formation, rich pore structure and large surface area improve photodegradation efficiency.

Purification of Artepillin C (ARC) with Anticancer Activities from Supercritical CO2-Ethanol Extracts of Brazilian Green Propolis by Using Adsorption Column Chromatography

Phenolic compounds with varying phenolic structures are present in both terrestrial and marine organisms. Artepillin C (ARC) is a prenylated phenolic compound produced specifically in Brazilian green propolis. Earlier studies have demonstrated the potential of ARC as a dietary supplement for cancer prevention due to its ability to suppress tumor growth and metastasis. Here we report the development of an effective adsorption chromatography combined with supercritical CO2 extraction for the massive purification of ARC. A mixture of supercritical CO2 and ethanol extract of Brazilian green propolis was passed through a stainless chromatographic column packed with protruding metals at 4,000 psi and 50 °C to remove wax from the column’s base. ARC mixed with flavonoids collected from the top of the column was applied to another stainless column filled with silica gel under similar working conditions. After flavonoids were removed, strongly adsorbed ARC at the top portion of the column was collected by ethanol elution. The purity of ARC isolated using this method was between 90% and 95%, as indicated by HPLC chromatograms. Purified ARC strongly inhibited cancer cell division based on its cytotoxic effects on HCT116 human colon cancer cells, resulting in a significantly increased distribution of cells in the S phase. ARC also blocks the motility of HCT116 cells, indicating its ability to suppress tumor metastasis. The developed chromatographic purification protocol can be used to isolate prenylated phenolic compounds from marine organisms.

Supercritical CO2 with co-solvent extraction of blackberry (Rubus spp. Xavante cultivar) seeds

Blackberry seed extracts (BSEs) were obtained by extraction using supercritical CO2 and ethanol as co-solvent. Conditions of 70 °C and 25 MPa provided the best results: 24.05 wt% of yield, total phenolic content of 3856 mg GAE 100 g−1, and 12,948, 12,996 and 14,243 µmol TE 100 g−1 for the assays ABTS, DPPH and FRAP, respectively. The nutritional lipid indices were PUFA/SFA ratio of 9.60, hypocholesterolemic/hypercholesterolemic ratio of 16.23, atherogenicity 0.06 and thrombogenicity 0.17. The main phenolic compounds were rutin and protocatechuic acid. The thermo-oxidative decomposition of the extract started at 196.25 °C and storage at − 29.52 °C. Rancimat analysis showed that the extract has a protective effect against the oxidation of soybean oil. These results indicate good potential for the application of this extract as an antioxidant.

Hydrodynamics of supercritical ethanol fluid-particles fluidization using low density ratio kinetic theory of granular flow

Hydrodynamics of sub- and super-critical ethanol fluid and particles were simulated using a low density ratio kinetic theory of granular flow in fluidized beds. The coexistence of a wave-like flow near the bottom and chunk-like flow at the upper part was observed in subcritical ethanol fluidized beds. During the fluidization of supercritical ethanol fluid-particle mixtures, aggregate-like structures of particles were found with increasing ethanol fluid temperatures and decreasing ethanol fluid pressures in supercritical ethanol fluidized beds. The simulated fluidization states identified reasonably with predictions using three different dimensionless numbers and stability function according to kinematic wave and dynamic wave velocities. The predicted bed expansion heights agreed with experimental data in supercritical carbon dioxide fluidized beds.

Industrial application of SiO2 aerogel prepared by supercritical ethanol (SCE) drying technique as cold and heat insulation materials

Industrial application of SiO2 aerogel prepared by supercritical ethanol (SCE) drying technique as cold and heat insulation materials

A recyclable anhydrous cotton dyeing technology with low energy consumption and excellent dyeing effects by mixing supercritical carbon dioxide, ethanol, and dimethyl sulfoxide

Traditional cotton water dyeing has a considerable ecological impact because of the use of water, but the available anhydrous cotton dyeing technologies cannot balance low recyclable energy consumption and excellent dyeing effects. In this study, a recyclable anhydrous cotton dyeing technology was designed and implemented by mixing supercritical carbon dioxide, dimethyl sulfoxide, and ethanol for the first time. Compared to the existing anhydrous cotton dyeing technologies, the novel technology could simultaneously obtain low recyclable energy consumption and excellent dyeing effects, such as dye penetration, washing and crocking fastness, levelness, color depth control and color matching. The dye fixations of reactive dyes in the novel technology are 5.1%–26.4% higher than those in traditional water dyeing. Meanwhile, the energy consumption of the novel technology is only 70% of that of traditional water dyeing, and the comprehensive cost of materials and energy of the novel technology is only 56% of that of traditional water dyeing. It is a new green option with low energy consumption for cotton dyeing.

Supercritical ethanol liquefaction of rice husk to bio-fuel over modified graphene oxide

An increase in the energy system used promote new renewable source produced to improve human well-being quality. The objective of this work is to study the supercritical ethanol liquefaction reaction using rice husk as a feedstock and graphene oxide as catalyst. Characterization of the catalyst was conducted using thermal gravimetry analysis technique and N2 Sorption. Results revealed that graphene oxide treated with 1.5 M sulfuric acid solution gave the largest surface area of 110.5 m2/g. This research promised to optimize bio-fuel production using Box–Behnken method with 15 experimental data. The significant of the 3 parameters (catalyst amount, temperature and reaction time) was demonstrated using the ANOVA method. These statistical data were employed to illustrate contour data and response surface. A polynomial equation was also derived from the experimental data and used to valid with calculated data from the equation. Optimization was discussed in term of yield and operating cost. Optimum conditions were of 51.8% bio-fuel yield were derived from supercritical ethanol liquefaction at reaction time of 298 °C, 60 min reaction time, and 3.4 grams of SO4(1.5)/GO catalyst. Bio-fuel derived the optimum condition gave a high heating value as high as 30.15 MJ/kg, which is in the range of transportation fuel.

Ultra High-Performance Supercritical Fluid Chromatography for the Quantitation of Diterpene Resin Acids in Norway Spruce Samples.

Picea abies (L.) H. Karst. (Pinaceae) is native to Northern, Central and Eastern Europe. The fast-growing tree reaches up to 50 m in height, has modest nutritional requirements and depends on sufficient water supply. The conifer, commonly called Norway spruce, produces exudates which are traditionally used to treat skin wounds in Northern European countries. Major bioactive constituents of the conifer oleoresin are diterpene resin acids (DRAs) of the abietane and the pimarane type. To assure consistent pharmaceutical quality of Norway spruce balm and commercial products thereof, an analytical method for the quantitation of DRAs is the prerequisite. However, high structural similarity among DRAs and their poor UV absorption makes chromatographic separation and detection challenging: Conventional liquid chromatography systems often fail to achieve sufficient separation, moreover, they are not sustainable. Gas chromatography on the other hand requires time-consuming derivatization prior to unacceptably long analyses (>60 min). These drawbacks prompted the development of the first validated supercritical fluid-based protocol for the separation and quantitation of eight DRAs, i.e., pimaric acid (1), sandaracopimaric acid (2), palustric acid (3), isopimaric acid (4), levopimaric acid (5), abietic acid (6), dehydroabietic acid (7), and neoabietic acid (8). By using an ultra high-performance supercritical fluid chromatography (UHPSFC) device hyphenated to a quadrupole mass detector, the DRAs were separated in less than 20 min on a Torus 2-Picolylamin (2-PIC) column (3.0 mm × 100 mm; 1.7 µm particle size) applying supercritical CO2 and ethanol as mobile phase. Regarding selectivity, accuracy (recovery rates: 87–108%), intermediate precision (between 6.6 and 11.1%), and linearity (R2 ≥ 0.99; linear between 0.75 μg/ml and 2.5 mg/ml), results were obtained in line with ICH guidelines. The lowest limit of detection (LOD) was at 0.75 μg/ml (7) and the lowest limit of quantitation (LOQ) at 2 μg/ml (8). As application examples, 22 Norway spruce balm samples and five commercial products were analyzed. The here presented protocol not only simplifies and shortens the analytical workflow, but also reduces the amount of organic solvent waste by about two thirds compared to conventional liquid chromatographic set-ups. These advantages qualify this fast and efficient method as an ideal tool for an environmentally friendly quality control of traditionally used wound-healing Norway spruce balm products.

Production of biodiesel with supercritical ethanol: Compromise between safety and costs

Biodiesel can be produced by using supercritical alcohols as reactants. Among the main advantages of such approach is that the mass transfer between the alcohol and the oils is considerably enhanced, and the reaction is not affected by the presence of free fatty acids in the raw materials. Nevertheless, the high pressure and temperature under which the reactions occur may cause safety concerns, making difficult the application of such processes on an industrial scale. In this work, the risks of the supercritical processes are assessed using indexes. Moreover, strategies are proposed to minimize the risk in such processes by selecting the optimal layout and the safeguards configuration. The analysis is performed for three production scales to assess its effect on process safety. The results indicate that layout optimization with safety criteria can improve safety in all production scales, reducing the risk of a catastrophic accident without significantly increasing costs. Additionally, it has been observed that increasing the production scale does not imply an important variation of the emissions of carbon dioxide per unit mass of product.

New Catalysts for Biodiesel Production under Supercritical Conditions of Alcohols: A Comprehensive Review

AbstractNowadays, due to detrimental carbon dioxide emissions and dwindling non‐renewable fossil energy from crude oil, biodiesel from green sources such as vegetable oils, animal fats, waste oils and microbial oils have been described as a promising non‐fossil fuel, renewable, sustainable, clean, and biodegradable. So far, transesterification is the most superior process for converting green resources into biodiesel by reacting with alcohol in the presence of a catalyst. This process is influenced by some considerations such as alcohol to oil molar ratio, reaction temperature, reaction pressure, reaction time and specifically the amount of catalyst, which greatly affect the reaction performance and the biodiesel production. In depth, this review will discuss novel catalysts for biodiesel production under supercritical methanol and ethanol conditions by reviewing published articles related to this field to date.

Catalytic conversion of Kraft lignin into platform chemicals in supercritical ethanol over a Mo(OCH2CH3)x/NaCl catalyst

A Mo(OCH2CH3)x/NaCl catalyst showed high efficiency in supercritical ethanol without adding H2 in the conversion of Kraft lignin to chemicals, including C6 alcohols, C8-C10 esters, benzyl alcohols and arenes. Control experiments were done with MoCl5, NaOC2H5 and the physical mixture of them. The Mo(OCH2CH3)x/NaCl catalyst exhibited superior activity among the samples examined. The overall yield increased as the reaction temperature increased from 260° to 300°C. The yield of aromatic compounds achieved 303 mg/g lignin over the Mo(OCH2CH3)x/NaCl catalyst at 300 °C for 6 h. MoCl5 and NaOC2H5 forms Mo(OCH2CH3)x in the catalyst preparation, which behaves as the active species in Kraft lignin conversion. The primary aromatics formed from the catalytic lignin depolymerization steps may undergo secondary reactions to form the final products.

Upgrading pyrolysis oil by catalytic hydrodeoxygenation reaction in supercritical ethanol with different hydrogen sources

The effects of hydrogen sources (hydrogen gas as an ex-situ hydrogen source and formic acid as an in-situ hydrogen source) on upgrading of pyrolysis oil by hydrodeoxygenation (HDO) in supercritical ethanol were comparatively investigated in this study for the first time. Effects of catalysts (5%Ru/C and 10%Ni-6%Mo-5%W/Al2O3), time and temperature on the product yields and quality of upgraded oil were investigated comparatively with different hydrogen sources. An interesting result was obtained, demonstrating that the in-situ hydrogen (formic acid) showed better HDO performance at mild temperatures (260, 300 ℃), while the HDO of pyrolysis oil with ex-situ hydrogen (H2 gas) at higher temperatures (325 or 350 ℃) with respects to degree of deoxygenation and the quality of the produced upgraded oils. HDO of the woody derived pyrolysis oil with total acid number (TAN) of 136.0 mgKOH/g at 350 ℃ for 2 h over Ru/C catalyst with formic acid or hydrogen gas resulted in 74% and 85% degree of de-oxygenation, respectively, producing high quality upgraded oils with TAN of 35.3 mgKOH/g and 50.1 mgKOH/g and HHV of 39.5 MJ/kg and 43.0 MJ/kg, respectively.

Hydrogenolysis of cornstalk lignin in supercritical ethanol over N-doped micro-mesoporous biochar supported Ru catalyst

Biochar is a promising support to prepare metal-based catalysts due to its large surface area and special porous structure. This work proposed a novel Ru-based biochar catalyst by using KCl and melamine as templates to produce micro-mesoporous structure and realize N-doping at the same time. The prepared Ru/NMC catalyst showed a good hydrogenolysis performance of cornstalk lignin in supercritical ethanol. A series of catalyst characterizations were carried out to reveal the effects of micro-mesoporous structure and N-doping on the lignin hydrogenolysis. The micro-mesoporous structure led to a large surface area, which favored the dispersion of metal site and facilitated the mass transfer and diffusion during lignin hydrogenolysis, while the N-doping formed abundant edge N atoms, which promoted the interaction and the electron transfer between the loaded Ru and the support. These two crucial factors synergistically improved the lignin hydrogenolysis, with 31.2 wt% monomer yield at the reaction temperature of 260 °C.

A New solubility model for competing effects of three solvents: Water, ethanol, and supercritical carbon dioxide

ABSTRACT This study aims to develop a new semi-empirical model to fit solute solubility in a mixture of solvents, viz. supercritical carbon dioxide, ethanol, and water, as well as to evaluate the effects of competing solvents on solubility. Therefore, the model was assessed by fitting the published solubility data and comparing it with the established semi-empirical models. The findings revealed that the new model gave the highest coefficient of determination, R2 of 0.96 and had the lowest AARD (i.e., 3.88%), compared to other models. To conclude, the new model is feasible in determining three solvents’ solvation effects in one system.

3D Photonic Crystals: Synthesis and Drying in Supercritical Ethanol

3D Photonic Crystals: Synthesis and Drying in Supercritical Ethanol

Antioxidant properties of lignin extracted from cotton stalks by ethanol solution-assisted liquid hot water before and after adding supercritical CO2

In order to turn waste into treasure, it is very important to study the characteristics of various components in the cotton stalk. This paper studied the changes in cotton stalk lignin yield and antioxidant capacity before and after the addition of CO2 to ethanol solution. To ensure the purity of lignin, liquid hot water (LHW) was used to degrade hemicellulose and pectin. Using response surface methodology, the optimal process conditions at each stage were determined. The best conditions for LHW pretreatment were that the temperature of 210 ℃, solid/water (1/13,w/v), time 32 min, and hemicellulose residual 2.23%. The predicted optimum conditions for ethanol solution (ES) were 220 ℃, 80% of ethanol content, 1 h, and obtained 53.82% lignin in totally. The best predict conditions for the supercritical CO2 ethanol solution (SCES) were 207 ℃，pressure 11 MPa, 40% of ethanol content, 1 h, and the total lignin yield was 75.41%. And the antioxidant capacity of SCES lignin was slightly stronger than ES lignin at the same temperature. The strongest oxidation resistance temperature was 220 ℃, the radical scavenging activities (RSA) of ABTS of SCES lignin was 94.32% higher than ES lignin 2.68%, and the DPPH RSA of SCES lignin was 78.42% higher than ES lignin 1.28%. Besides in the infrared spectrum that SCES lignin lacked the 1660 cm−1 band meant that didn’t occur α-carbonyl substitution reaction in the process. And other properties of lignin were similar between ES and SCES methods.