超临界二氧化碳染色技术研究进展

概述了超临界二氧化碳染色技术的染色机理,对不同染料的染色工艺条件的研究情况做了分析。阐述了染料研究和混合染料拼色研究的进展情况。对超临界二氧化碳的染色热力学和动力学性研究情况做了论述,对染料在超临界二氧化碳中的溶解度、染料在纤维与超临界CO2间的分配规律、染料在纤维中的扩散行为做了分析论述。对染色设备的国内外进展情况做了分析论述。指出了超临界二氧化碳染色技术产业化应用应解决的关键问题是增强染料的溶解和在纤维中的扩散,以及高压操作下大容积染色釜的研制。     

Synthesis of reactive disperse dyes containing halogenated acetamide group for dyeing cotton fabric in supercritical carbon dioxide

A series of reactive disperse dyes incorporating halogenated acetamide group were synthesized and applied to dye cotton fabric in supercritical carbon dioxide (scCO₂). Dyeing experiments were conducted in scCO₂ with dye concentration of 0.5% owf (% on weight of cotton fabric), varying from 80 to 120 °C, for 1–3 h at a constant pressure of 200 bar. The results showed that the color strength of dyed cotton fabric increased favorably when increasing temperature and time. The color characteristics were studied as well in terms of the reflectance spectra. And the color fastness to washing and rubbing were also reasonably good.     

Polymerization of acrylonitrile in supercritical carbon dioxide

A series of fluorinated diblock copolymers, consisting of styrene (St)-acrylonitrile (AN) copolymer [poly(St-co-AN)] and poly-2-[(perfluorononenyl)oxy]ethyl methacrylate, with various compositions as well as with different molecular weights were synthesized by atom transfer radical polymerization and characterized. Dispersion polymerization of acrylonitrile in supercritical carbon dioxide (scCO₂) at 30 MPa and at 65 °C with this kind of amphiphilic block copolymer as a stabilizer and 2,2′-azobisisobutyronitrile as an initiator was investigated. The experimental results indicated that, in the presence of a small amount of poly(St-co-AN) (5 wt% to AN), spherical particles of polyacrylonitrile (PAN) were prepared with small diameter and narrow polydispersity (d_n = 153 nm, d_w/d_n = 1.12), resulting from the high stabilizing efficiency of this fluorinated block copolymer. Furthermore, the polymerization of AN in scCO₂ under different initial pressures especially under low pressure (<14 MPa) was studied. When the polymerization was carried out around the critical pressure of CO₂ (7.7-7.8 MPa), the PANs with high molecular weight (M_ν ≈ 130,000-194,000) were synthesized at high monomer conversion (>90%) no matter whether the stabilizer was added, compared to those synthesized by dispersion polymerization at 30 MPa. It was also found that the crystallinity of PAN synthesized at 7.7-7.8 MPa was somewhat higher than that synthesized at 30 MPa, while its crystallite size did not change.     

聚对苯二甲酸丁二酯纤维在超临界二氧化碳介质中的染色研究

用超临界二氧化碳作介质，在40～120℃，10～30MPa条件下使用分散染料对聚对苯二甲酸丁二酯(PBT)纤维进行染色试验，并测定了3种分散染料在超临界二氧化碳介质中的溶解度。研究了染色温度、压力、时间及染料结构对染料上染量的影响，考察了染料溶解度与染料上染量的关系。试验表明，在80℃，20MPa下，染色30min，PBT纤维能得到良好的染色效果，上染量达4．01mg/g(分散红60)、2．43mg／g(分散黄23)、11．19mg/g(分散蓝79)。     

Analysis on the dyeing of polypropylene fibers in supercritical carbon dioxide

Polypropylene fibers were dyed in supercritical carbon dioxide system and the results were compared with those of fiber dyed in water system. Dye uptake value calculated by a UV spectrum indicated that polypropylene fiber dyeing was much better in carbon dioxide than in water. Optical microscopical analysis showed that dye molecules had diffused thoroughly into fiber in CO₂ because of the excellent compatibility between the dye and the CO₂. X-ray and birefrigence analysis demonstrated that plastification caused by the implementation of CO₂ made molecular chain more mobile and led to an increase in the dyeing of polypropylene fibers. Moreover a mechanical test and DSC analysis indicated that the fiber structure was not damaged when the fabric was dyed at 100 °C. Hence dyeing polypropylene using CO₂ as a transport medium was very feasible and worthy of further development.     

Solubility of thymol in supercritical carbon dioxide and its impregnation on cotton gauze

Through this study, an attempt has been made to evaluate the solubility of thymol in supercritical carbon dioxide as well to investigate a prospect of its impregnation on cotton gauze on laboratory scale. Solubility of thymol in supercritical carbon dioxide was determined at temperatures of 35 °C, 40 °C and 50 °C, and pressures ranging from 7.8 to 25 MPa (CO₂ density range 335.89–849.60 kg/m³) using a static method. The solubility data were correlated using semi-empirical equations introduced by Chrastil, Adachi and Lu and del Valle and Aguilera. Taking into account obtained results, temperature of 35 °C and pressure of 15.5 MPa were selected as operating conditions for the impregnation process. Impregnation of cotton gauze with thymol was performed in a cell using carbon dioxide as a solvent. Kinetics of the process was determined and modeled. Masses of thymol on cotton gauzes after 2 h and 24 h of impregnation were 11% and 19.6%, respectively. FT-IR analysis confirmed the presence of thymol on the surface of the cotton fibers. The impregnated gauze provided strong antimicrobial activity against tested strains of Escherichia coli, Staphylococcus aureus, Bacillus subtilis, Enterococcus faecalis and Candida albicans.     

Acetylation of plant cellulose fiber in supercritical carbon dioxide

Natural cellulosic ramie fiber was acetylated using supercritical carbon dioxide (sc-CO₂) as a reaction medium. The structure and properties of the acetylated fibers were investigated using infrared spectroscopy, scanning electron microscopy, X-ray diffraction (including synchrotron microbeam X-ray diffraction), nano-Raman scattering, and a tensile test. The acetylation reaction proceeded without using an organic solvent, and it reached to the core part of the fiber within a short period while maintaining the fiber morphology. The crystallites of cellulose triacetate II and cellulose coexist in the fiber. The acetylated fiber with an average degree of substitution of 1.9 showed high modulus (34.5 GPa) and high strength (763 MPa), which are the highest values for cellulose diacetate so far reported to date.     

Effect of supercritical carbon dioxide on polystyrene extrusion

A study on the extrusion of polystyrene was carried out using supercritical carbon dioxide (scCO₂) as foaming agent. scCO₂ modifies the rheological properties of the material in the barrel of the extruder and acts as a blowing agent during the relaxation at the passage through the die. For experiments, a single-screw extruder was modified to be able to inject scCO₂ within the extruded material. The effect of operating parameters on material porosity was studied. Samples were characterized by using water-pycnometry, mercury-porosimetry and scanning electron microscopy. Polystyrene with expansion rate about 15–25% was manufactured. A rapid cooling just downstream the die is important to solidify the structure. The die temperature allows the control of the porosity structure. CO₂ concentration shows no significant influence.     

Solubility of chlorpheniramine maleate in supercritical carbon dioxide

Solubility of chlorpheniramine maleate in supercritical carbon dioxide at different temperatures (308–338 K) and pressures (160–400 bar) is measured using static method coupled with gravimetric method. The measured solubility data demonstrated that the solubility of chlorpheniramine maleate was changed between 1.54 × 10⁻⁵ and 4.26 × 10⁻⁴ based on the mole fraction as the temperature and pressure are changed. The general trend of measured solubility data shows a direct effect of pressure and temperature on the solubility of chlorpheniramine maleate. Finally, the obtained solubilities correlated using four semi-empirical density-based correlations including Mendez Santiago–Teja (MST), Kumar and Johnston (KJ), Bartle et al., and Chrastil models. Although the results of modeling showed that the KJ model leads to the average absolute relative deviation percent (AARD %) of 8.1% which is the lowest AARD %, deviation of other utilized correlations are rather the same.     

A significant approach to dye cotton in supercritical carbon dioxide with fluorotriazine reactive dyes

A series of fluorotriazine reactive dyes have been synthesized and applied to dye cotton in supercritical carbon dioxide (scCO₂) with good dyeing results. The pieces of cotton to be dyed were previously presoaked in a protic solvent and cosolvents were applied during dyeing. The colour strength of the dyeings was evaluated by K/S measurements. The K/S values achieved on cotton dyed were up to 35.8 ± 4.2. Even after the cotton was subjected to a Shoxlet extraction at 358 K for 1 h, a maximum K/S value of 20.2 ± 1.8 was measured. The percentage of dye molecules chemically fixed to the cotton was on average 85%. The excellent reactivity of fluorotriazines allowed a reduction of 3 h on the dyeing time. It is noticeable that a dye concentration of 10% on weight of the fibre (owf) can be applied to dye cotton with fluorotriazines, since no damage of the cotton fibres occurred, as observed for the chlorotriazines at this high dye concentration.Dyes with fluorotriazine as reactive group were found to be the most preferable dyes for dyeing cotton in scCO₂, as they were able to exceed the limitation of the reaction with the cotton.     

Cross-linking polymerization of acrylic acid in supercritical carbon dioxide

Cross-linking polymerization of acrylic acid in supercritical carbon dioxide (scCO₂) was studied in a batch reactor at 50 °C and 207 bar with either triallyl pentaerythritol ether or tetraallyl pentaerythritol ether as the cross-linker and with 2,2′-azobis(2,4-dimethyl-valeronitrile) as the free radical initiator. All polymers were white, dry, fine powders. Scanning electron microscopy showed that the morphology of the polymer particles was not affected by cross-linking. As the cross-linker concentration was increased, the polymer glass transition temperature first decreased, then increased. Water-soluble and water-insoluble polymers were synthesized by adjusting the cross-linker concentration. Viscosity measurements showed that the polymer thickening effect strongly depended on the degree of cross-linking. Finally, cross-linking polymerization of acrylic acid in scCO₂ was carried out in a continuous stirred tank reactor. The use of cross-linker decreased the monomer conversion in this system.     

Experimental investigation and modeling of the solubility of carvedilol in supercritical carbon dioxide

This study was aimed to measure the solubility of carvedilol in the temperature and pressure ranges of 308⿿338 K and 160 bar to 400 bar, respectively. In this direction, a homemade high pressure visual equilibrium cell was used to measure the solubility of carvedilol using a static method coupled with gravimetric technique. The results revealed that the carvedilol solubility was ranged between 1.12 ÿ 10^⿿5 and 5.01 ÿ 10^⿿3 based on the mole fraction (mole of carvedilol/mole of carvedilol + mole of CO₂) in this study as the temperature and pressure was changed. Finally, the results were correlated using four density-based semi-empirical correlations including Chrastil, Mendez⿿Santiago⿿Teja (MST), Bartle et al., and Kumar and Johnston (K-J) models. Results revealed that although the K-J model leads to the lowest average absolute relative deviation percent (AARD %) of 6.27%, but it could not be considered as the most accurate correlation since all the used four correlations introduces AARD % of about 6⿿10% which may be in the same range as the experimental error.     

超临界CO2萃取丁香挥发油的实验研究

采用正交实验法对超临界CO2萃取丁香挥发油的条件进行了研究。考察了萃取温度、压力、CO2流量等因素在不同水平下对丁香挥发油提取率的影响。得到了超临界C02萃取丁香挥发油的最佳实验条件：萃取压力30MPa、温度40℃、CO2流量40kg／h和萃取时间80min,得率为20．62％。与水蒸气蒸馏法比较,超临界CO2萃取的收率高,萃取时间短。     

Group A particle fluidization in supercritical carbon dioxide: Effect of operating conditions on fluidization efficiency

An experimental study was carried out to determine the fluidization behavior of group A glass bead beds under supercritical conditions. The fluidization state was followed experimentally by pressure drop measurements. Particle fluidization was obtained with carbon dioxide conditions far from the critical point, whereas near this point gas channeling should occur. Particle aggregation can be attributed to increased interparticle forces under these conditions.     

Drying of agar gels using supercritical carbon dioxide

The use of supercritical carbon dioxide (scCO₂) for the removal of water from agar gels has been investigated and compared to air and freeze drying. Experiments were conducted to evaluate how gel formulation (with and without sucrose) and drying conditions (with and without ethanol as a co-solvent, flow rate and depressurisation rate) affected the microstructure of the gels dried using scCO₂. X-ray micro-computed tomography (X-ray micro-CT) was used to determine the voidage (% open pore space) of the dried structures, which can be used to indicate the extent of drying-induced structural collapse (in general, the lower the voidage, the greater the collapse). For formulations containing sucrose, which displayed the best structural retention, voidage was found to increase in the order: air drying (4% voidage) < supercritical drying with pure CO₂ (48%) < supercritical drying with ethanol-modified CO₂ (68%) < freeze drying (76%). The relatively high voidage of samples dried in the presence of ethanol, was due in part to foaming of the gels, hypothesised to result from an interaction between the agar and ethanol, rather than an effect of the supercritical fluid. CO₂ flow rate (1 vs. 3 l/min) during supercritical drying and depressurisation rate (0.4 vs. 1.6 MPa/min) had no effect on the dried microstructure.     

Enhanced crystallization of bisphenol-A polycarbonate by nano-scale clays in the presence of supercritical carbon dioxide

The crystallization behavior of bisphenol-A polycarbonate (PC) and PC/clay nanocomposites were studied in the presence of supercritical carbon dioxide (SCCO₂) using DSC, WAXD and AFM. In the absence of SCCO₂, nano-scale clay itself does not change the crystallization behavior of PC under our experimental conditions. In the presence of SCCO₂, clay appears to be an efficient nucleating agent and enhances the crystallization of PC. The addition of clay reduces the induction time of crystallization and increases the crystallization rate. The increase in crystallinity with clay depends on the crystallization time. When the crystallization time is sufficient, PC and PC/clay composites tend to have similar crystallinity in the range of 26%. Two melting temperatures are observed during the DSC heating scan, and are mainly associated with the melting of both secondary and primary crystals. Results show that the clay influences the primary crystallization process more than the secondary crystallization process.     

Solubility of cyproheptadine in supercritical carbon dioxide; experimental and modeling approaches

Solubility of solute in supercritical fluids at different pressures and temperatures is one of the most important parameters necessary for design of any supercritical fluid-based processes. Among different supercritical fluids, carbon dioxide is one of the most widely used solvents due to its useful and green characteristics. In this work, with the assist of supercritical carbon dioxide as the solvent, solubility of cyproheptadine in different temperatures (308–338 K) and pressures (160–400 bar) are measured using static method. The obtained results demonstrated that solubility of cyproheptadine ranged between 3.35 × 10⁻⁵ and 3.09 × 10⁻³ based on mole fraction. A closer examination of measured solubility data show that not only solubility of cyproheptadine increases by increasing pressure but also experiences a cross over pressure about 200 bar. At last, the measured solubility data are correlated using four widely used density based correlations namely Mendez Santiago–Teja (MST), Kumar and Johnston (KJ), Bartle et al., and Chrastil models. The obtained results demonstrated that the best correlative capability was observed for KJ model leads to the average absolute relative deviation percent (AARD %) of 6.3%.     

Reactive extraction of succinic acid using supercritical carbon dioxide

Reactive extraction using supercritical carbon dioxide (scCO₂) and tri-n-octylamine (TOA) was evaluated as a separation method of succinic acid from an aqueous solution. The reactive extraction of succinic acid was performed at varying initial acid concentrations in aqueous solution (0.07–0.45 mol?dm^?3), temperature (35–65°C) and pressure (8–16 MPa). The succinic acid separation was conducted in both batch mode and semi-continuous mode. The highest reactive extraction efficiency of approx. 62% was obtained for the process conducted in semi-continuous mode at 35°C and 16 MPa for the initial acid concentrations in aqueous phase of 0.39 mol?dm^?3.     

Catalyst retention in continuous flow with supercritical carbon dioxide

This review discusses the retention of organometallic catalysts in continuous flow processes utilizing supercritical carbon dioxide. Due to its innovative properties, supercritical carbon dioxide offers interesting possibilities for process intensification. As a result of safety and cost considerations, processes that use supercritical carbon dioxide are preferably done in continuous flow, as they require a pressure upwards of 74 bar. Many of the reactions that benefit from the application of supercritical carbon dioxide also involve the use of a homogeneous catalyst however, requiring efforts to recycle the catalyst when these are applied in continuous flow. Alternatively, the catalyst may be retained in the reactor by modifying the process or catalyst, such as by catalyst immobilization, membrane separation, or biphasic processing exploiting the properties of supercritical carbon dioxide. Each of these methods is discussed, including their advantages and drawbacks. Also discussed are milli- and micro-flow processes and their possibilities for integrated catalyst retention and handling supercritical carbon dioxide.     

二氧化碳超临界萃取乙基香兰素粗制品的研究

采用二氧化碳超临界萃取乙基香兰素粗品,研究萃取压力、萃取温度、萃取时间、流体流量等工艺条件对萃取效率和产品质量的影响.得出最佳工艺条件,采用萃取压力25～30 MPa,萃取温度55～60℃,流体流量5 L/h,萃取5～6 h,萃取效率可以达到95％,可以得到质量分数大于95％的乙基香兰素产品.