Xi:Irritant;61546-01-8Relevant articles and documents
Phase transitions in higher-melting imidazolium-based ionic liquids: Experiments and advanced data analysis
?anji, Maja,Bendová, Magdalena,Bogdanov, Milen G.,Wagner, Zdeněk,Zdol?ek, Nikola,Quirion, Fran?ois,Jandová, Věra,Vrbka
, (2019)
As thermal energy storage becomes an increasingly important topic, good knowledge of properties of phase-change materials (PCM) is essential. Among other properties, a good PCM should show a large enthalpy of melting, reproducible melting/solidification cycles, and long-term thermal stability. Temperatures and enthalpies of fusion should be determined at a possibly large range of conditions to allow for a critical evaluation of the experimental data and assessment of the material application potential. In this work, imidazolium-based ionic liquids (ILs) with long alkyl chain substituents 1-hexadecyl-3-methylimidazolium chloride and 1-hexadecyl-3-methyl-imidazolium saccharinate were studied in view of their possible use as phase-change materials. Differential scanning calorimetry (DSC) and the heat-leak modulus (HLM) methods were used to determine the temperatures and the enthalpies of phase transitions in the studied ILs, enabling us to study the influence of the heating and cooling rates on the measured properties. Enthalpies of fusion near to or larger than 100 J·g?1 were found in the studied ionic liquids, making them promising candidates for thermal energy storage. Peaks corresponding to possible liquid crystalline phases in the DSC traces of 1-hexadecyl-3-methylimidazolium saccharinate were observed, pointing to more complex phase behaviour of the studied ionic liquids. Finally, to critically evaluate the experimental data measured in this work, methods based on mathematical gnostics were used. Repeatability of measurements and the degree of mutual agreement between the methods used in this work could thus be determined.
Templating and phase behaviour of the long chain ionic liquid C 16mimCl
Kaper, Helena,Smarsly, Bernd
, p. 1455 - 1471 (2006)
In the light of recent studies about the favourable sol-gel templating behaviour of the long chain ionic liquids (ILs) 1-hexadecyl-3-methylimidazolium chloride and -bromide (C16mimCl and C16mimBr) the phase behaviour of these ILs is investigated in detail and compared to common surfactants such as hexadecyltrimethylammonium chloride and -bromide (CTAC and CTAB). Specially developed small angle X-ray scattering (SAXS) evaluation approaches confirm a lamellar double-layer structure for crystalline C 16mimCl of the ABACAB type. Presumably, the orientation of the head groups repeats in every second head group layer. Therefore, the imidazolium head group exhibits long range interactions on packing and templating, in contrast to the ammonium head group. The lyotropic phase behaviour is investigated via SAXS, isothermal titration calorimetry (ITC) and surface tension measurements. Interestingly, the phase diagrams of C16mimCl and CTAC are quite different, especially at higher concentration of surfactant: instead of a gel phase in the phase diagram of CTAC, a lamellar-hexagonal two phase region as well as a pure lamellar phase is found in the phase diagram of C 16mimCl. The critical micellar concentration (cmc) and enthalpy of micellization (ΔmicH) show that the cmc for imidazolium based surfactants is slightly lower and ΔmicH is more exothermic than for the ammonium type surfactants. These results are able to account for the specialties observed in the sol-gel templating behavior. by Oldenbourg Wissenschaftsverlag.
Imidazolium-based ionic liquids for asphaltene dispersion; experimental and computational studies
El-hoshoudy,Ghanem,Desouky
, (2021)
Heavy and bituminous crude oils containing asphaltene are expected to compensate for the decline of conventional oil production in the upcoming days. Asphaltene precipitation is detrimental to petroleum processing owing to blockage of the wellbores and formation of tough emulsions that diminishes the recovered oil amount. As a result, the petroleum industry resorts to asphaltene dispersants to overcome these challenges. In this regard, ionic liquids (ILs) can be utilized as a green chemistry alternative to the surfactants to prevent asphaltene aggregation in the petroleum feed stream. Ionic liquids are environmental, recyclable, and non-corrosive candidates, which destabilize or breakdown water in oil (W/O) or oil in water (O/W) emulsions through dispersing or replacing asphaltene molecules at the interface. Also, ionic liquids containing long alkyl chains can be effective asphaltene dispersants owing to the formation of hydrogen bonding and π-π? interactions with asphaltene aggregates. In this work, different ILs salts and their modified Lewis-acid structure were synthesized by mixing iron (III) chloride with different halogenated alkyl imidazolium salts with yield% of 73.56, 72.9, and 71.12% respectively. The thermogravimetric analysis indicates the thermal stability of the synthesized ILs to 463 °C. The critical micelle concentration (CMC) and interfacial tension (IFT) were investigated at simulated reservoir conditions of high-pressure high temperature (HPHT). ILs exhibited CMC values at 1000, 800, and 600 ppm, while IFT values lie in the range of 3–8 mN/m at 298 K. ILs efficiency as asphaltene dispersants were assessed experimentally through viscometric and spectroscopic methods using 1000 ppm of asphaltene extract. The viscometric method displays asphaltene onset precipitation at 65% n-heptane after the addition of [(-C4H9-IL) FeCl4?] dispersant, while spectroscopic method asphaltene onset precipitation at 55, 60 and 75% after the addition of [(-CH3-IL) FeCl4?], [(-C2H5-IL) FeCl4?] and [(-C4H9-IL) FeCl4?], respectively. Molecular dynamics (MD) simulation was carried out to investigate the compatibility of ionic liquids as a function of asphaltene and crude oil molecules. The asphaltene molecules modeled as a continental model involves a dominant polyaromatic nucleus linked to peripheral substituted side chains. The computational results are in great compliance with the experimental ones.
Tetrafluoroborate salts as site-selective promoters for sol-gel synthesis of mesoporous silica
Okabe, Akihiro,Fukushima, Takanori,Ariga, Katsuhiko,Niki, Makiko,Aida, Takuzo
, p. 9013 - 9016 (2004)
Tetrafluoroborate ion (BF4-) serves as a powerful and better-behaved promoter than fluoride ion (F-) for hydrolytic condensation of alkoxysilanes, such as tetraethoxy orthosilicate, in aqueous media containing amphiphiles with onium ion headgroups as templates, affording thermally and hydrothermally stable mesoporous silica. According to 19F NMR spectral profiles, BF4- is localized on a positive-charged micellar surface, thereby allowing a site-selective growth of the silica framework. The resulting porous silica has an ordered hexagonal structure with a well-developed and thick silicate wall. Even without calcination, the condensation with BF4- as the promoter progresses to a large extent to furnish a [Si-(OSi-)4]/([HOSi(OSi-) 3] + [(HO)2Si(OSi-)2]) ratio of 6.2, which is greater than that of mesoporous silica formed without BF4- before (1.5) and even after calcination (3.5) to promote thermal condensation in the solid state.
Multifunctional amphiphilic ionic liquid pathway to create water-based magnetic fluids and magnetically-driven mesoporous silica
Shen, Jing,He, Wen,Wang, Tongwen
, p. 3504 - 3513 (2019/02/12)
Amphiphilic ionic liquids, 1-alkyl-3-methylimidazolium chloride (CnmimCl with n = 10, 12, 14, 16) were firstly used as modifiers to construct a self-assembly bilayer on the surface of iron oxide nanoparticles for generation of highly stable, water-based magnetic fluids. Subsequently, a magnet-driven mesoporous silica was synthesized by in situ self-assembly in the bilayer CnmimCl-stabilized magnetic fluid using the C16mimCl as template and tetraethylorthosilicate (TEOS) as silicon source via a hydrothermal synthesis and following calcination procedure. A systematic study was carried out addressing the influence of the alkyl chain length of CnmimCl in the primary and secondary layers on the stability of magnetic fluids. The characterization of TEM, XRD, VSM, electrophoresis experiments, TGA and DTA showed that stable water-based magnetic fluids can be synthesized based on the assembly of the well-defined bilayer-CnmimCl structure with long-chain C16mimCl as secondary layer on the magnetite (Fe3O4) nanoparticles. The results of small and wide-angle XRD, TEM, VSM, and N2 absorption experiments indicated that the nano-scale magnetic Fe3O4 particles were inlayed into hexagonal p6mm mesoporous silica (MCM-41 type) framework. Importantly, it was found that the obtained Fe3O4/MCM-41 was an appropriate adsorbent for the adsorption of rhodamine B and methylene blue from their aqueous solution. In addition, the adsorbent could be separated and reclaimed fleetly from the solution under external magnetic field.
