Cyano-containing ionic liquids for the extraction of aromatic hydrocarbons from an aromatic/aliphatic mixture

Ionic liquids can replace conventional solvents in aromatic/aliphatic extractions, if they have higher aromatic distribution coef- ficients and higher or similar aromatic/aliphatic selectivities. Also physical properties, such as density and viscosity, must be taken into account if a solvent is applied in an industrial extraction process. Cyano-containing ionic liquids have a lower den- sity than the benchmark solvent sulfolane and a higher viscosity. Sulfolane is from a hydrodynamic point of view a better sol- vent than ionic liquids for the aromatic/aliphatic extraction. The most suitable ionic liquids for the extraction of aromatic hy- drocarbons from a mixture of aromatic and aliphatic hydrocarbons are [bmim]C(CN)3, [3-mebupy]N(CN)2, [3-mebupy]C(CN)3, [3-mebupy]B(CN)4 and [mebupyrr]B(CN)4. They have factors of 1.2-2.3 higher mass-based distribution coefficients than sul- folane and a similar or higher, up to a factor of 1.9 higher, aromatic/aliphatic selectivity than sulfolane. The IL [3-mebupy]N(CN)2 is a better extractant for the separation of toluene from a mixture of toluene/n-heptane in a pilot plant Ro- tating Disc Contactor (RDC) than sulfolane.     

Control of various morphological changes of poly(meth)acrylate microspheres and their swelling degrees by SPG emulsification

Crosslinked poly(meth)acrylate polymers with a variety of morphologies were synthesized with two steps. In the first step, a microporous glass membrane (Shirasu Porous Glass, SPG) was employed to prepare uniform emulsion droplets by applying an adequate pressure to the monomer phase, which was composed of the ADVN initiator, solvent of toluene or heptane or their mixture, and a mixture of (meth)acrylate monomers. The droplets were formed continuously through the membrane and suspended in the aqueous solution, which contained a PVA‐127 suspending agent, SLS emulsifier, and NaNO₂ inhibitor to suppress the nucleation of secondary particles. SPG pore sizes of 0.90, 5.25, and 9.25 μm were used. Then the emulsion droplets were polymerized at 343 K with a rotation rate 160 rpm for 24 h. The (meth)acrylate monomers 2‐ethylhexyl acrylate (2‐EHA), 2‐ethylhexyl methacrylate (2‐EHMA), cyclohexyl acrylate (CHA), methyl methacrylate (MMA), lauryl acrylate (LA), and lauryl methacrylate (LMA) were used in this research. The influences of the ratios of the monomer and crosslinking agent EGDMA, the amount of diluents, the monomer type on the polymer particle morphology, the swelling degree, and the polymer particle size were investigated. It was found that an increase in the concentrations of EGDMA and heptane resulted in higher coarse porous spheres and smaller polymer particle sizes. A coefficient with a variation close to 10%, or a standard deviation of about 4, was obtained. The capacity of these spheres as solvent absorption materials was examined. The highest swelling degrees of heptane and toluene were obtained when LA was employed as the monomer with 30% (by weight) of EGDMA and 70% (by weight) of heptane as an inert solvent. The highest capacity of the solvent absorption was obtained when using a polymer particle size of 4.81 μm, as prepared by SPG pore size 0.9 μm. The polymer particles were able to absorb aliphatic hydrocarbon solvents, aromatic hydrocarbon solvents, and a mix of aliphatic hydrocarbon solvents and aromatic hydrocarbon solvents, such as toluene and heptane. The capacity of solvent absorption for the aromatic hydrocarbon solvents was higher than for the aliphatic hydrocarbon solvents. In addition, the particles did not rupture or collapse after absorption in solvents. © 2000 John Wiley & Sons, Inc. J Polym Sci A: Polym Chem 38: 4038–4056, 2000     

Poly(aryl ether) Dendrons with Monopyrrolotetrathiafulvalene Unit‐Based Organogels exhibiting Gel‐Induced Enhanced Emission (GIEE)

A series of poly(aryl ether) dendrons with a monopyrrolo‐tetrathiafulvalene unit linked through an acyl hydrazone linkage were designed and synthesized as low molecular mass organogelators (LMOGs). Two of the dendrons could gelate the aromatic solvents and some solvent mixtures, but the others could not gel all solvents tested except for n‐pentanol. A subtle change on the molecular structure produces a great influence on the gelation behavior. Note that the dendrons could form the stable gel in the DMSO/water mixture without thermal treatment and could also form the binary gel with fullerene (C₆₀) in toluene. The formed gels undergo a reversible gel–sol phase transition upon exposure to external stimuli, such as temperature and chemical oxidation/reduction. A number of experiments (SEM, FTIR spectroscopy, ¹H NMR spectroscopy, and UV/Vis absorption spectroscopy, and XRD) revealed that these dendritic molecules self‐assembled into elastically interpenetrating one‐dimensional fibrillar aggregates and maintain rectangular molecular‐packing mode in organogels. The hydrogen bonding, π–π, and donor–acceptor interactions were found to be the main driving forces for formation of the gels. Moreover, the gel system exhibited gel‐induced enhanced emission (GIEE) property in the visible region in spite of the absence of a conventional fluorophore unit and the fluorescence was effectively quenched by introduction of C₆₀.     

Charge‐Transfer Complex Formation in Gelation: The Role of Solvent Molecules with Different Electron‐Donating Capacities

A naphthalenediimide (NDI)‐based synthetic peptide molecule forms gels in a particular solvent mixture (chloroform/aromatic hydrocarbon, 4:1) through charge‐transfer (CT) complex formation; this is evident from the corresponding absorbance and fluorescence spectra at room temperature. Various aromatic hydrocarbon based solvents, including benzene, toluene, xylene (ortho, meta and para) and mesitylene, have been used for the formation of the CT complex. The role of different solvent molecules with varying electron‐donation capacities in the formation of CT complexes has been established through spectroscopic and computational studies.     

Studies on organogelation of self assembling bis urea type low molecular weight molecules

A novel class of toluene based bis urea compounds carrying linear fatty acid units and semicarbazide linkages has been synthesised. The compounds were exhibiting thermoreversible gelation at concentrations below 10 mg/mL in common organic solvents, both aliphatic and aromatic. The effect of the chain length variation of fatty acid units on gelation properties like gelation concentration, gelation time and gel melting temperatures were studied. Choosing a particular gelator of fixed chain length and a specific solvent, the effect of the concentration on the gelation properties were studied. The thermal studies using DSC revealed the presence of phase transitions corresponding to the premelting and melting of the gels during the heating cycle. The morphology of the xerogels studied using SEM revealed a three dimensional network structure while the WAXS studies showed no crystallinity in the xerogels. IR spectra of the gels (solvent subtracted) and solutions in the corresponding solvent showed that a high degree of inter-molecular H bonding exists and absorptions corresponding to NH stretching shifted to lower wave numbers. Thus simple bisurea type of compounds exhibiting gelation ability in a wide range of solvents can be used for making functional gels for various applications.     

Electron density matching as a guide to surfactant design

The effectiveness at reducing interfacial tension between water and different organic solvents was studied, with 14 structurally different dichain sulfosuccinate surfactants. Variations in chemical structure ranged from linear/branched alkyl tail groups, to phenyl-tipped tail units, to partially and fully fluorinated tails. The solvents n-heptane, toluene, and perfluoroheptane were used as example oil phases. Interfacial activity was measured in terms of a reduced interfacial tension scale, R(IFT), based on the value in the presence of surfactants compared to that for the pure solvent-water interface. Overall surfactant chain structure was determined to be the key factor affecting R(IFT). Furthermore, a strong correlation was observed between R(IFT) and the electron density rho(e) of the different surfactants: with any given oil, the most effective surfactants have rho(e) values closest to that for the solvent. For example, phenyl-tipped surfactants were shown to be comparatively more effective at the interface with an aromatic solvent (toluene) than with an aliphatic n-alkane (heptane). Furthermore, fluorination of the tail groups decreased effectiveness at the hydrocarbon/water interface, which was substantially increased at the fluorocarbon/water interface: this too followed the electron density-matching pattern. The importance of chain-tip chemical structure was also noted, with regard to the introduction of phenyl, CF3-, and H-CF2- terminal moieties. For branched alkyl-tailed surfactants, it was found that effectiveness could be linked to an empirical "branching factor". The significance of the electron density matching of organic solvent and surfactant for the prediction of interfacial activities is highlighted, and this concept may prove useful for the future design of new high-efficiency surfactants.     

Dipeptide-based low-molecular-weight efficient organogelators and their application in water purification

The development of new low-molecular-weight gelators for organic solvents is motivated by several potential applications of gels as advanced functional materials. In the present study, we developed simple dipeptide-based organogelators with a minimum gelation concentration (MGC) of 6-0.15 %, w/v in aromatic solvents. The organogelators were synthesized using different L-amino acids with nonpolar aliphatic/aromatic residues and by varying alkyl-chain length (C-12 to C-16). The self-aggregation behavior of these thermoreversible organogels was investigated through several spectroscopic and microscopic techniques. A balanced participation of the hydrogen bonding and van der Waals interactions is crucial for efficient organogelation, which can be largely modulated by the structural modification at the hydrogen-bonding unit as well as by varying the alkyl-chain length in both sides of the hydrophilic residue. Interestingly, these organogelators could selectively gelate aromatic solvents from their mixtures with water. Furthermore, the xerogels prepared from the organogels showed a striking property of adsorbing dyes such as crystal violet, rhodamine 6G from water. This dye-adsorption ability of gelators can be utilized in water purification by removing toxic dyes from wastewater.     

Swelling behaviors of poly(dodecyl methacrylate-co-methyl eugenol) and poly(dodecyl methacrylate-co-methyl chavicol) gels in essential oil components

Poly(dodecylmethacrylate-co-methyleugenol) P(DDMA-co-Meu) and poly(dodecylmethacrylate-co-methylchavicol) P(DDMA-co-Mch) gels were synthesized in ethanol using free radical cross-linking polymerization method at 60 °C for 24 h in the presence of azobisisobutyronitrile (AIBN) and triethylene glycol dimethacrylate (TEGDMA) as initiator and cross-linker, respectively. Scanning electron microscopy (SEM) and Fourier transform infrared spectroscopy (FTIR) were used to characterize the gels. These gels were used to investigate swelling behaviors in linalool and methyl eugenol, in essential oil mixture of phenyl propanoid and terpenoid, and also in various solvents. While the equilibrium swelling values (ESV) of both gels were higher in linalool than in methyl eugenol, the result was vice versa in the case of essential oil mixture. ESVs of both gels were also obtained in various solvents with different functional groups and the highest ESV of both gels were obtained in toluene, and the lowest ESV of P(DDMA-co-Meu) and P(DDMA-co-Mch) was in methanol and in ethylene glycol, respectively. While P(DDMA-co-Meu) is sensitive to carbon number change in alcohol, P(DDMA-co-Mch) is less sensitive. In the case of esters, increase of carbon number in functional group causes a more significant change in ESV than an increase of carbon number in aliphatic chain. Experimental results were correlated by the first-order and second-order models. The second-order model was more suitable than the other. While P(DDMA-co-Meu) gel swelled in linalool exhibits a Fickian diffusion character, the diffusion mechanism of the gel in methyl eugenol is a non-Fickian one. In the case of P(DDMA-co-Mch), the result is vice versa.     

Thermal decompostion of dicyclopentadienyltitanium(IV) diaryl and dibenzyl compounds

The thermal decomposition of compounds of the type Cp₂TiR₂ (Cp = cyclopentadienyl, R = aryl or benzyl) in the solid state and in various solvents has been studied. In the solid state and in aromatic and aliphatic hydrocarbon solvents the compounds decompose with quantitative formation of RH and a Ti-containing residue which has lost the Cp₂Ti structure. Experiments with deuterated compounds and solvents showed that decomposition proceeds via intramolecular abstraction of a hydrogen atom either from a cyclopentadienyl ring or from the other coordinated group R. Results of insertion reactions with tolane confirm these two reaction pathways. In tetrahydrofuran and tetrachloromethane, decomposition proceeds in a more complex way, with participation of the solvent.     

Thermodynamic description of liquid–liquid equilibria in systems 1-ethyl-3-methylimidazolium ethylsulfate + C7-hydrocarbons by polymer-solution models

In the present paper, liquid–liquid equilibrium in binary systems containing the ionic liquid 1-ethyl-3-methylimidazolium ethylsulfate is studied. It was suggested in papers published by other authors that 1-ethyl-3-methylimidazolium ethylsulfate could potentially be a suitable solvent for extracting aromatic compounds from mixtures containing aliphatic hydrocarbons, such as naphtha cracker feeds. To be able to assess the selectivity of 1-ethyl-3-methylimidazolium ethylsulfate towards aliphatic, cyclic, and aromatic hydrocarbons, mutual solubilities of the ionic liquid and n-heptane, methylcyclohexane, and toluene were measured by the volumetric method. To evaluate quantitatively the quality of the experimental data and their agreement with available literature values, a correlation by two polymer-solution models, the modified Flory–Huggins equation proposed by De Sousa and Rebelo and the thermodynamic lattice model proposed by Qin and Prausnitz was carried out, the model parameters being optimized by a gnostic regression method.     

Ultraviolet grafting of methacrylic acid and acrylic acid on high‐density polyethylene in different solvents and the wettability of grafted high‐density polyethylene. I. Grafting

Methacrylic acid (MAA) and acrylic acid (AA) were grafted onto high‐density polyethylene (PE) with UV initiation and a range of solvents. With acetone as the solvent, MAA was more easily grafted onto PE when the photoinitiator benzophenone was precoated on PE than when it was dissolved in the monomer solution. The grafting was faster in aliphatic solvents than in polar solvents or a UV‐adsorbing aromatic solvent (toluene). Acetone itself could initiate the photografting of both MAA and AA onto PE when it was mixed with water. The extent of grafting of MAA onto PE showed a maximum when there was about 40% acetone in the mixture. For AA, when the acetone/water concentration was 10%, the extent of grafting increased rapidly with the irradiation time. At higher acetone concentrations, the extent of grafting was low. Atomic force microscopy images showed that the surface topography of PE grafted with MAA in acetone/water was quite different from that obtained when the grafting was performed in other organic solvents. © 2003 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 42: 253–262, 2004     

Swelling of <Emphasis Type="Italic">N</Emphasis>-vinylcaprolactam-dodecyl methacrylate gel in {heptane + toluene} mixtures

A copolymer gel has been synthesized from N-vinylcaprolactam and dodecyl methacrylate in ethanol using the free radical cross-linking polymerization method. Characterizations of the gel were performed by scanning electron microscopy (SEM), Fourier transform infrared spectroscopy (FTIR), and thermal gravimetric analysis (TGA) techniques. Swelling behavior of the gel was investigated in heptane, toluene, and their binary mixtures with different compositions. Swelling value in toluene is higher than that in heptane and swelling value increases with the increasing initial content of toluene in the binary mixture with heptane. The swelling values are correlated by the first- and second-order differential equations, and the best model correlating the experimental results is a second-order one. Diffusion coefficients have also been calculated for heptane and toluene at each concentration by power-law and first-order equations. While the diffusion mechanism of the gel in heptane is a Fickian one, the gel swelled in toluene exhibits a non-Fickian character. Diffusion mechanisms of the gels in binary mixtures are much more complicated. Because of the higher swelling degree in toluene compared to that in heptane, selectivity of the gel in different {heptane + toluene} mixtures with selectivity close to 1 has also been taken into consideration.     

Effect of solvent on the gelation properties of a metallo-organic polymer of [Fe(II) (4-octadecyl-1,2,4-triazole)3(ClO4)2]n

In this contribution we report on the preparation of thermally responsive supramolecular gels obtained through self-assembling of metallo-organic polymers of lipophilic Fe(II) complexes of 1,2,4-triazole functionalized with octadecyl chains ([Fe(II) (4-octadecyl-1,2,4-triazole)₃(ClO₄)₂]_n) in three organic solvents: toluene, cis-decalin and trans-decalin. A gel phase is formed in these solvents by cooling the homogeneous complex solutions below a well-defined temperature, the so-called gelation threshold. These gels are reversible as they form homogeneous solutions upon heating above the melting temperature. The systems have been characterized for their thermal and viscoelastic properties through differential scanning calorimetry and rheological experiments, respectively. The effect of the solvent type and concentration on the gelation behaviour of the metallo-organic polymer has been analysed. The results obtained point to structural differences and different gelation mechanisms for the gels prepared in different solvents and they also suggest the possibility to control the spin-crossover transition temperature associated to the sol-gel transition.     

Noncovalent Macromolecular Architectures of Oligo(p-phenylenevinylene)s (OPVs): Role of End Functional Groups on the Gelation of Organic Solvents

Summary: Self-assembly of a few OPV derivatives having different end functional groups to aggregates, fibrous networks and organogels are discussed. OPV1 and OPV2 functionalized with ester moieties form gels in nonpolar hydrocarbon solvents whereas OPV3 with carboxylic acid groups form gel from THF and dichloromethane. OPV4 with dicyano moieties form aggregates but could not gelate solvents. AFM and TEM studies revealed considerable difference in the morphology of the self-assembled structures of OPV1-4 . From the optical, morphological and gelation data it is concluded that the nature of the end functional groups strongly influences upon the self-assembly and gelation properties of OPVs.     

Crosslinked Polystyrene Beads Modified with Sulfonyl Groups and Their Application in Aromatic/Aliphatic Hydrocarbons Separation

The separation of aromatic hydrocarbons from aromatic/aliphatic mixtures was investigated with cross- linked polystyrene（CPS） beads modified with sulfonyl groups. Three sulfonating agents, i.e. benzenesulfonyl chlo- ride（BsCl）, 4-toluene sulfonyl chloride（TsC1） and methanesulfonyl chloride（MsC1） were used to prepare sulfonyl CPS beads by Friedel-Crafts reaction. The CPS beads modified with BsC1 exhibited higher sulfonation rate than those modified with MsC1 and TsCI and obtained optimum selectivity in the experiments of toluene/n-heptane separation. Further separation tests with various other aromatic/aliphatic mixtures were carried out at an initial aromatic concen- tration of 13%（mass fraction） with the results showing that the modified beads have preferential selectivity for aro- matic hydrocarbons in all aromatic/aliphatic mixtures, and especially a separation factor of 8.21 and a swelling ratio of 30% for toluene/cyclohexane system. The thermal stability and regeneration test indicate that the used polystyrene beads can be recovered through heat-drying and reused effectively.     

Chiral bis(amino alcohol)oxalamide gelators-gelation properties and supramolecular organization: racemate versus pure enantiomer gelation

Four new chiral bis(amino alcohol)oxalamides (1-4: amino alcohol=leucinol, valinol, phenylglycinol, and phenylalaninol, respectively) have been prepared as low-molecular-weight organic gelators. Their gelation properties towards various organic solvents and mixtures were determined and these were then compared to related bis(amino acid) oxalamide gelators. Spectroscopic (FTIR, (1)H NMR) and X-ray diffraction studies revealed that the primary organization motif of (S,S)-1 and racemate 1 (rac-1) in lipophilic solvents involved the formation of inverse bilayers. The X-ray crystal structure of (S,S)-1 also shows this type of bilayer organization. The crystal structure of rac-2 reveals meso bilayers of hydrogen-bonded aggregates. Within the bilayers formed, the gelator molecules are connected by cooperative hydrogen bonding between oxalamide units and OH groups, while the interbilayer interactions are realized through lipophilic interactions between the iBu groups of leucinol. Oxalamide meso-1 lacks any gelation ability and crystallizes in monolayers. In dichloromethane rac-1 forms an unstable gel; this is prone to crystallization as a result of the formation of symmetrical meso bilayers. In contrast, in aromatic solvents rac-1 forms stable gels; this indicates that enantiomeric bilayers are formed. Oxalamide rac-1 is capable of gelling a volume of toluene three times larger than (S,S)-1. A tranmission electron microscopy investigation of rac-1 and (S,S)-1 toluene gels reveals the presence of thinner fibers in the former gel, and, hence, a more compact network that is capable of immobilizing a larger volume of the solvent. The self-assembly of these types of gelator molecules into bilayers and subsequent formation of fibrous aggregates can be explained by considering the strength and direction of aggregate forces (supramolecular vectors) in three-dimensional space.     

Physico-chemical analysis of semi-crystalline PEEK in aliphatic and aromatic solvents

Polyether ether ketone (PEEK) is a semi-crystalline thermoplastic polymer having excellent mechanical and thermal properties. Exposure of this polymer to aliphatic and aromatic solvents can lead to degradation or swelling of the polymeric material. The present work described the plasticization and stability analysis of semi-crystalline PEEK under different aromatic and aliphatic solvent environment. A variety of solvents (acetone, benzene, benzyl alcohol, chloroform, methanol, and toluene), based on their Hildebrand’s Solubility Parameter, were chosen for investigation. The physico-chemical characteristics of virgin and treated polymeric samples were investigated using Gas Chromatography–Mass Spectrometry (GC–MS), Thermogravimetric Analysis (TGA), Differential Scanning Calorimetry (DSC), and Fourier Transform Infrared Spectroscopy (FTIR) techniques. The results indicated that the solvent exposure did not significantly affect the thermal behavior and chemical structure of the polymer. However, it seems that certain components of the polymer were leached into the solvent phase as revealed by the GC–MS analysis. The present study identified PEEK as a potentially suitable polymer for the applications where high resistance to aliphatic and aromatic solvents is needed.     

Phase equilibria study of the (N-octylisoquinolinium thiocyanate ionic liquid + aliphatic and aromatic hydrocarbon,or thiophene) binary systems

Binary liquid + liquid phase equilibria for 8 systems containing N-octylisoquinolinium thiocyanate, [C₈iQuin][SCN] and aliphatic hydrocarbon (n-hexane, n-heptane), cyclohexane, aromatic hydrocarbon (benzene, toluene, ethylbenzene, n-propylbenzene) and thiophene have been determined using dynamic method. The experiment was carried out from room temperature to the boiling-point of the solvent at atmospheric pressure. For the tested binary systems the mutual immiscibility with an upper critical solution temperature (UCST) for {IL + aliphatic hydrocarbon, or thiophene} were observed. The immiscibility gap with lower critical solution temperature (LCST) for the {IL + aromatic hydrocarbon} were determined. The parameters of the LLE correlation equation for the tested binary systems have been derived using NRTL equation. The phase equilibria diagrams presented in this paper are compared with literature data for the corresponding ionic liquids with N-alkylisoquinolinium, or N-alkylquinolinium cation and with thiocyanate – based ionic liquids. The influence of the ionic liquid structure on mutual solubility with aliphatic and aromatic hydrocarbons and thiophene is discussed.     

Nonstoichiometric gelation of cyclodextrins and included planar guests

A generic family of low molecular weight binary gels comprising beta-cyclodextrin (beta-CD) and one of a large variety of polyaromatic hydrocarbons (PAHs) in dimethylformamide (DMF), pyridine, and other polar solvents is described. The system is rather general and robust. It tolerates large changes in each of the major ingredients without losing gelation ability. alpha- and gamma-CD, and negatively or positively modified beta-CD (e.g., sulfate-, phosphate-, or amine-tethered beta-CD) as well as methylated beta-CD are all effective gelators. The cogelators encompass a similarly large variety of compounds characterized by the ability to form an ovular inclusion complex with the CD molecules and a capability to stack outside the CD cap to give long-range order far from the CD cap. Despite the low ratio between the CD and the cogelators, we show that most of the CD molecules are retained in the liquid phase and do not participate directly in the actual construction of the gel network. In fact, most of the sulfated and phosphated beta-CDs can be cleaned off the gel structure by electrophoresis, leaving an intact gel porous structure. The nonstoichiometric nature of the gel is underscored by the fact that one molecule of beta-CD can combine with as few as three molecules of chrysene or as many as 450 molecules of chrysene to gelate an additional 35,000-40,000 molecules of the solvent.