Separation of Anthracene from Crude Anthracene Using Gas Antisolvent Recrystallization

Abstract

Pure anthracene is mostly used for conversion to anthraquinone, an intermediate for the synthesis of very powerful vat dyestuffs. A coal tar distillate, crude anthracene, which contains 30% anthracene, 25% phenanthrane, 15% carbazole, and other impurities, was used as the model mixture. In this study, 90% by weight purity anthracene was obtained using gas antisolvent (GAS) recrystallization. The GAS process induces the separation of solids by introducing an antisolvent, carbon dioxide (or the supercritical fluid), into acetone which was used as the liquid solvent. The dissolution of the compressed gas into the solute-laden solution selectively lowers the solubilities of solid solutes and salts them out. The results showed that high purity anthracene was obtained at a high feed concentration and high pressure conditions. The separation factor of anthracene versus phenanthrene is close to 30.07.     

Optimization of solvent crystallization process in obtaining high purity anthracene and carbazole from crude anthracene

Solvent crystallization is the main method used for preparing anthracene and carbazole from the crude anthracene. The key to the optimization of this method is improving the solubility selectivity of the solvent by means of solvent modulating and process optimization. In this study, the solubility of anthracene, phenanthrene, and carbazole in xylene, dimethylformamide (DMF), DMF with amine/amide, isopropanolamine, and chlorobenzene is examined and the solid‐liquid ternary anthracene–carbazole–DMF/(DMF+19.96% isopropanolamine) system phase diagram is determined and applied in the solvent crystallization process. The results showed that the solubility selectivity of xylene increases with increased temperature. Also, selectivity increases with an increase of the amount of isopropanolamine in the mixture of DMF and isopropanolamine, while decreases with increased temperature. Through multiple washings of crude anthracene with xylene, DMF+19.96% isopropanolamine, and chlorobenzene, it was possible to obtain anthracene and carbazole of purity higher than 98 wt %. © 2013 American Institute of Chemical Engineers AIChE J, 60: 275–281, 2014     

Separation of Campesterol and β‐Sitosterol from a Sterol Mixture

Abstract

By solvent crystallization using diethyl ether as the solvent on sterol mixture, brassicasterol and stigmasterol that contains a side chain with double bond were separated from campesterol and β‐sitosterol with a saturated side chain. The total campesterol and β‐sitosterol content in the liquid phase was more than 97% with a recovery of 12%. Multistage crystallization using acetone as the solvent could increase the recovery of campesterol and β‐sitosterol to 30%. By employing zeolite selective adsorption on the campesterol and β‐sitosterol fraction, β‐sitosterol can be recovered in the liquid phase with a purity of 95.2% and a recovery of 3% (overall recovery 1%). After desorbing in ethanol, campesterol adsorbed on the zeolite can be recovered with a purity of 95.4% and a recovery of 3.7% (overall recovery 1.6%).     

异丙醇-环己烷萃取精馏过程模拟与优化

利用化工流程模拟软件Aspen Plus对异丙醇-环己烷共沸物系的双塔连续萃取精馏过程进行了模拟计算与优化。首先根据溶剂相似相溶原理,先初选出糠醛和硝基苯作为备选溶剂,再通过汽液平衡试验及ChemCAD模拟筛选,确定糠醛为最适宜溶剂,选择NRTL模型作为物性方法,使用RadFrac模块进行模拟计算,并利用灵敏度分析模块对各工艺参数进行优化。结果表明,最适宜工艺方案为：萃取精馏塔理论塔板数为30,原料在第26块板进料,溶剂在第12块板进料,物质的量回流比为1.8,溶剂质量比为3∶1;溶剂回收塔理论板数为15,进料位置在第10块板,物质的量回流比为1.0。分离效果可达到环己烷质量分数为99.74%,异丙醇质量分数为99.61%。模拟和优化结果为分离过程的优化操作和设计提供了依据。     

Experimental Conditions for HPLC Analysis of Ethoxylated Alkyl Phenol Surfactants in Microemulsion Systems. Part II. Gradient Mode for Extended EON Range as Found in the Analysis of Oligomer Fractionation

Abstract

The different oligomers of ethoxylated nonylphenols present in commercial surfactants can be separated by HPLC. While low ethylene oxide number (EON) species may be separated by isocratic HPLC on silica, intermediate EONs require gradient elution HPLC. The separation of higher oligomers can be carried out with an intermediate polarity column of the NH₂ type and a solvent gradient. The suggested experimental conditions allow a satisfactory single run separation of a complex mixture with EONs ranging from 1 to 25 by using a linear gradient from 100% less polar solvent (n-heptane—chloroform—methanol 90/5/5) to its mixture with up to 20% of a more polar solvent made of chloroform—methanol (50/50). This method is used to analyze the EON distribution resulting from the mixing of different commercial surfactants. When two surfactants with very different EON distributions are mixed to produce a formulation scan, the occurrence of three-phase behavior at the optimum formulation of the surfactant—oil—water system is found to correlate with the absence of a gap in the overall EON distribution. Both the fractionation of low EON species into the oil phase and the fractionation of high EON oligomers into the water phase result in a depletion of the microemulsion phase.     

Ring-Opening Reaction of Hexamethylcyclotrisiloxane with Tetrachlorosilane and Isomerization of the Product

A molecular complex of triphenylphosphine oxide and tetrachlorosilane (II) in a solvent mixture that contains 90% toluene and 10% acetonitrile acts as a catalyst to open the cyclic siloxane oligomer, hexamethylcyclotrisiloxane (I). The primary product is the linear oligomer 1,1,1,7-tetrachlorohexamethyltetrasiloxane (III). III can be converted quantitatively to the structural isomer, 1,3,3,7-tetrachlorohexamethyltetrasiloxane (IV), in the same catalyst–solvent mixture either by stirring at room temperature for 12 h or by heating at 90°C for about 1 h. In both reactions, the disappearance of the reactants and the formation of the products can be followed by glc. Products III and IV are characterized by elemental analysis, molecular mass, infrared spectra, and ¹H- and ²⁹Si-NMR spectra. III and IV can be transformed into their fluorinated derivatives, VI and VII, respectively, by stirring for several days in a toluene slurry of KSiF₆. The ¹⁹F-NMR spectra of VI and VII are consistent with the proposed isomeric structures.     

PURIFICATION OF HYDROCHLORIC ACID BY ISOOCTANE EXTRACTION

ABSTRACT

Removal of organic compounds from hydrocloric acid can be performed by a solvent extraction process followed by a solvent regeneration step by adsorption with sepiolite. The extraction study includes the analysis of the influence of the operating conditions, the determination of the solute distribution coefficient for isooctane and the effect of temperature on the extraction. The adsorption isotherms were calculated to check the technical viability of the method. The obtained efficiency of extraction is close to 90 wt%, whereas that of the solvent regeneration recovery is over 67 wt%     

A New Type of Continuous Countercurrent Extraction: An Extractor with Two Continuous Phases

Abstract

A continuous countercurrent extractor in which both solvent phases move as continuous streams was constructed and studied. Fibrous strands, e.g., cotton-rayon yarn, were utilized as “wall-less” tubings for the hydrophilic solvent (heavy phase) and the light phase mov d in a countercurrent manner through the annular spaces of the column. With the model system, caffeine-water-ethyl acetate, the highest efficiency demonstrated was HETS = 1.1 in. A mixture of caffeine and nicotinamide (β = 4) can be separated to a purity of 4000:1 or higher in the solvent system of ethyl acetate: water by the use of a specially designed feed stage located at the middle of the column. A colorful demonstration of this process utilized two dyes, Sudan black B (purple) and p-phenylazophenol (yellow) in the solvent system of toluene:n-hexane (1:3) vs methanol: water (4:1). The extractor is free of emulsion problems as demonstrated by the inclusion of Tween 80 in the heavy phase of the ethyl acetate-water system. The extractor can be run unattended indefinitely.     

Efficient Extraction of Fuel Oil Hydrocarbons from Wood

Abstract

Sequential cold (room temperature) extraction from aged contaminated wood samples (southern yellow pine) with acetone followed by n‐pentane (upon a 3–4 days of sample incubation with each solvent) yielded more than 90% analyte recovery for both ambient (natural moisture content) and water‐submerged wood, significantly exceeding the recoveries obtained with one‐step extraction using single solvents and/or their mixtures. By contrast, a much faster ultrasound/Soxhlet extraction led to a virtually complete analyte recovery while using a 1∶1 mixture of these two solvents. Evidence obtained indicates that a possible role for the first solvent, acetone (in addition to collection of loose analyte), is the removal of an aqueous barrier surrounding the strongly adsorbed hydrocarbon, thus enabling its extraction by the second (non‐polar) solvent. For larger analyte concentrations (>60 mg n‐hexadecane/g wood), the high‐affinity binding sites became saturated (yielding 5–10 mg unrecovered analyte/g wood), and then a single solvent was sufficient for a near‐quantitative extraction.     

Solvent extraction of granular cottonseed cake

Advantages of the Rotocel system for cottonseed cake extraction may be summarized in the following manner:

1. Economical conversion to solvent extraction is possible by utilizing existing or reconditioned screw-press equipment.
2. Conditioner and flaking rolls are not required for this process.
3. The electrical power requirements for the cake preparation and extraction are less than the power reduction when converting from straight pressing to a prepress operation. This results in a net savings in power consumption.
4. Vapor scrubbers used in conventional plants are not required in this process.
5. Efficient extraction at low solvent ratios keeps the steam requirement of this process to a minimum.
6. Low residual oil in extracted meal accomplished by this process yields a maximum product value per ton of seed.
7. The low temperature vapor desolventizer eliminates discolorization and protein degradation of the cake granules during the desolventizing step.

     

Prediction of Optimum Composition of the Mixed Solvent N-Methylpyrrolidone/Ethylene Glycol for the Extraction of Aromatics

Abstract

The optimum composition of mixed solvent which is usually determined experimentally is predicted by a method in which the minimum total energy required for extraction and subsequent solvent recovery by distillation is calculated. The method is demonstrated using N-methylpyrrolidone (NMP) and monoethylene glycol (EG) as mixed solvent for the extraction of benzene from a hexane/benzene mixture. UNIFAC method was used to predict liquid phase equilibria in extraction and liquid-vapor equilibria in distillation. To demonstrate the method flexibility, ethylene glycol was replaced by water as another alternative solvent, and the optimum composition of the new mixed solvent of NMP/water was predicted. However this particular mixed solvent required much higher energy than NMP/EG case.     

Microwave-Vacuum Drying Kinetics of Pharmaceutical Powders

Abstract

The drying kinetics (maximum drying rate, drying constants) and center temperature of selected powder (aspirin, paracetamol, lactose, and maize starch)–solvent (water, ethanol, methanol, and acetone) systems were monitored during microwave-vacuum drying. An experimental microwave-vacuum system (650 W and 2.45 GHz) operated at 61–81 kPa was used. The drying rate profile did not vary with the powder–solvent system; an initial warming-up period was followed by a constant-rate stage and two falling-rate periods. However, the drying kinetics were found to be both powder and solvent dependent, with the drying times for acetone-, ethanol-, and methanol-wetted materials being considerably shorter (up to 89.8%) than those of samples containing water. Although the general form of the temperature profile (short warming-up period, constant-rate stage, and decreasing temperature phase) was similar for all systems, the maximum temperatures varied quite significantly with solvent type, ranging from highest to lowest in the order water-ethanol-methanol-acetone. For most powder–solvent systems, reduced operating pressure facilitated increased drying rates and thus shorter drying times.     

低温煤焦油中正十二烷-甲苯-苯酚的相平衡及分离

低温煤焦油组分的分离对其充分利用具有重要的作用。分别以正十二烷、甲苯和苯酚为模型化合物,采用实验和Aspen Plus模拟两种方法得到了低温煤焦油中脂肪烃-芳烃-酚类三元体系的液液平衡关系,并模拟了N,N-二甲基甲酰胺（DMF）水溶液萃取分离该体系时的典型三元相图。结果表明,Aspen Plus采用UNIF-LL法模拟得到的三元相图与实验测定结果吻合较好。甲苯在正十二烷-甲苯-苯酚体系中作为共溶溶剂,促使三元体系成为均相。根据正十二烷、甲苯和苯酚在DMF中的溶解性差异,结合Hansen溶度参数理论,通过在DMF中添加不同含量的H₂O以调节萃取剂的极性,可使正十二烷和甲苯依次从均相体系中分离。通过对萃取温度、剂油比和萃取剂含水量进行优化,最终在303.15 K,剂油比为1.5时,以DMF对模型油进行单级萃取,可以得到纯度为93.2%的正十二烷;相分离后向萃取相中添加DMF量30%的H₂O,可分离出纯度为93.4%的甲苯。     

Oxygen Production by Pressure Swing Adsorption

Abstract

The specific oxygen production capacity and the oxygen recovery of a pressure swing adsorption (PSA) process for the production of oxygen from ambient air by selective adsorption of nitrogen can be increased by operating the process at a superambient temperature. The higher temperature operation provides more efficient desorption of nitrogen from the adsorbent which more than off-sets the detrimental effects of the lower selectivity and capacity of adsorption of nitrogen from air at the elevated temperature. The concept is demonstrated by evaluating the performance of an eight-step PSA-oxygen process to produce a 90% oxygen product stream at different temperatures. It is shown that 10% higher oxygen production capacity and 14.5% larger oxygen recovery can be obtained by operating the PSA process at 60°C compared to its performance at 30°C. The PSA process and its performance data from a pilot plant are discussed.     

Studies on the Recovery of Uranium from Phosphoric Acid Medium Using Synergistic Mixture of 2-Ethyl Hexyl Hydrogen 2-Ethyl Hexyl Phosphonate and Octyl(phenyl)-N,N-diisobutyl Carbamoyl Methyl Phosphine Oxide

Abstract

This paper describes the extraction of uranium from aqueous phosphoric acid medium using 2-ethyl hexyl hydrogen 2-ethyl hexyl phosphonate (PC88A) and octyl (phenyl)-N,N-diisobutylcarbamoylmethylphosphine oxide (CMPO) individually as well as their synergistic mixture in different diluents. The extraction parameters such as variation in concentration of either of the extractants, concentration of H₃PO₄ and uranium in the aqueous phase are investigated to optimize the extraction conditions. Results indicate that the synergistic mixture, 0.9 M PC88A + 0.1 M CMPO in xylene, can be used for the extraction of uranium from the phosphoric acid medium. The loaded uranium from the synergistic organic phase can be stripped using 0.5 M solution of (NH₄)₂CO₃. This synergistic mixture is used to recover uranium from a typical wet process phosphoric acid sample and the recovery is found to be better than 90%.     

Removal of Zinc Ions from Aqueous Chloride Solutions by Solvent Extraction Using Alamine 308

Abstract

A study has been undertaken to develop a solvent extraction system for zinc with Alamine 308 in aqueous chloride medium. The parameters investigated included reagent concentration, acid concentration, pH, aqueous to organic phase ratio, and rate of extraction and stripping. The study shows that zinc can be extracted rapidly and efficiently from aqueous chloride solutions. A number of aqueous stripping reagents removed more than 90% of the zinc from the organic phase with only one equilibration.     

Removal of polycyclic aromatic hydrocarbons from contaminated soil in a two-phase partitioning bioreactor

A two-phase partitioning bioreactor was employed to remediate soil contaminated by a mixture of polycyclic aromatic hydrocarbons consisting of phenanthrene, anthracene, and pyrene. In this study, the transfer of three PAHs into the water-immiscible liquid phase (silicone oil or paraffine oil) from the soil was investigated during the first 24 h. And then, phenanthrene and anthracene were degraded by approximately 90% and 80%, respectively, compared with initial concentration in soil, but pyrene was not degraded during seven days of operation period. In addition, the feasibility of a soil slurry sequencing batch reactor system in terms of continuously operating a two-phase partitioning bioreactor was investigated. Phenanthrene and anthracene were degraded semi-continuously and repeatedly during two operating cycles. Pyrene was still not degraded and was just transferred into the water-immiscible liquid phase considering its solubility.     

Recovery of Chloroform from Effluent with Solvent Extraction–Distillation Process

Abstract

A solvent extraction–distillation process for recovery of chloroform in aqueous effluent was developed. Sutfonated kerosene was used for extraction of chloroform. When the flow ratio of organic phase to aqueous phase is 0.1, the chloroform concentration in the aqueous effluent can be decreased from 10 g/L to about 100 mg/L by 3-stage countercurrent extraction. The distribution ratio of chloroform between sulfonated kerosene and water is about 50. Sodium sulfate in the aqueous effluent will enhance the distribution. A small amount of water was added to the distillation column for stripping chloroform in sulfonated kerosene. RPC was used as a commercial extractor. Scale-up from the data of the pilot test was based on the Karr correlation. Recovery of chloroform was over 90%, and residual kerosene in the aqueous effluent from the extraction was lower than 70 mg/L. It is expected that the technique can be used for the recovery of other organic solvents miscible with kerosene.     

Separation of diethylbenzene isomers by distillative freezing

Due to the close boiling points of the mixed diethylbenzene (DEB) isomers, it is rather complicated to separate them by distillation. A new separation technique, distillative freezing (DF), is successfully applied to separate p-DEB from the diethylbenzene isomers in this study. Basically, the DF process operates at a triple point condition, in which the liquid mixture is simultaneously vaporized and solidified due to the three-phase equilibrium. It results in the formation of pure crystals along with the liquid phase and vapor phase of the mixtures. The process can be continued until the liquid phase is completely eliminated and only the pure solid crystals remain in the feed. A model, whereby the DF process is simulated in a series of equilibrium stage operations, is proposed to direct the DF operation. In the model, each stage is operated under an adiabatic condition at a three-phase equilibrium. The experiments show that, in the p-DEB/m-DEB mixtures, p-DEB can be purified from 80% to 99% through several DF operations with the experimental recovery rate of p-DEB in one DF operation ranging from 58% to 77%. The unique feature of this new separation technique is that no filtration and crystal washing is required after the p-DEB crystals are obtained by DF.     

Modeling of the Chromatographic Solvent Gradient Reversed Phase Purification of a Multicomponent Polypeptide Mixture

Abstract

A model for Calcitonin purification from an industrial peptide mixture using polymer‐based reversed phase columns was developed. Regressed competitive bi‐Langmuir isotherm parameters for pure calcitonin are strong functions of the eluent composition and were correlated to the overall Henry coefficient only. It is shown that, by keeping constant these correlations, the adsorption behavior of impurities can be predicted simply by estimating their Henry coefficient from the raw mixture. The same can be repeated with very good results when changing the stationary phase or the organic solvent in the eluent. In both cases, only the Henry coefficient must be re‐estimated from pulse injections.