Highly efficient separation of benzene+cyclohexane mixtures by extraction combined extractive distillation using imidazolium-based dicationic ionic liquids

Benzene(BEN)and cyclohexane(CYH),which have very close boiling points and a binary azeotrope,are the most difficult binary components in the separation of aromatic and non-aromatic hydrocarbons.This study further explored the separation mechanism and industrial application prospects of BEN+CYH mixtures separated by a dicationic ionic liquid(DIL)[C_(5)(MIM)_(2)][NTf_(2)]_(2) based on experimental research.The calculation results of the Conductor-like Screening model Segment Activity Coefficient(COSMO-SAC)model show that selectivity and solvent capacity of the DIL are significantly improved.The effects of different anions and cations on the micro-structure distribution and diffusion behavior of BEN+CYH system were investigated by quantum chemistry(QC)calculations and molecular dynamics(MD)simulations.The results indicate that the anion[NTf_(2)]_(2)has low polarity,uniform charge distribution,and a dual role of hydrogen bonding andπ-πbonding,and the cation[C_(5)(MIM)_(2)]^(2+) has stronger interaction with BEN and higher selectivity than conventional cations.The liquid-liquid extraction and extractive distillation(LLE-ED)process using an optimized 65 mol/mol DIL+35 mol/mol H_(2)O mixed solution as the extractant was proposed,which solved the problem of low product purity in the LLE process and high energy consumption in the ED process.Under the best operating conditions,the purity of CYH product was 99.9%,the purity of BEN product was 99.6%,the recovery rate of BEN reached 99.9%,and the recovery rate of DIL reached 99.9%.The heat-integrated LLE-ED process reduced total annual cost by 21.6%,and reduced CO_(2) emissions by 48.0%,which has broad industrial application prospects.

Synthesis, characterization and tribological evaluation of novel1,4-diazabicyclo[2.2.2]octane based dicationic ionic liquids as efficient antiwear lubricant additives

Ionic liquids have developed and been applied in lubricant field since 2001. Nevertheless, it is little known about novel dicationic ionic liquids for tribology applications in the past several years. In this paper, a sequence of novel dicationic ionic liquids based on 1,4-diazabicyclo[2.2.2]octane cations(DABCO) and different anions have been designed and identified. The structures of ILs were confirmed by Fourier transform infrared(FTIR) spectra, multinuclear(~1H,^(13)C,^(11)B,^(31)P and ^(19)F) magnetic resonance and mass spectrometry. The effects of anion type on thermal properties, wettability, kinematic viscosity and tribological properties were studied. It is found that all of these dicationic ionic liquids as additives exhibit excellent anti-wear and friction-reducing properties in PEG synthetic base oil under boundary lubrication conditions for steel-to-steel contact, which offers great potential for the highly efficient lubricant additives. Simultaneously, novel 1,4-diazabicyclo[2.2.2]octane cation offers an exceptional chance for the research and development of dicationic ionic liquids in various applications.

Physicochemical and tribological properties of gemini-type halogen-free dicationic ionic liquids

A series of new halogen-free dicationic ionic liquids(ILs)with different alkyl chain lengths were prepared,and the relationship between the alkyl chain length,physicochemical and tribological properties of ILs,and their role as neat lubricant for steel–steel friction pairs,was investigated.Evaluation of stability during hydrolysis and copper strip corrosion test results show that synthetic ILs are stable and not corrosive to metal contacts,due to the halogen-free anions.The friction and wear test results indicate that ILs with long alkyl chains have excellent friction-reducing and anti-wear properties,especially at high temperatures.Based on the surface three-dimensional(3D)profiles,electrical contact resistance,scanning electron microscopy(SEM),energy dispersive X-ray spectroscopy(EDS),and the X-ray photoelectron spectrometry(XPS)analysis of the worn surfaces of steel discs,we can conclude that the efficiency of ILs is due to the formation of high quality tribofilms that consist of both tribochemical reaction and ordered absorption films.

A dicationic,podand-like,ionic liquid water system accelerated copper-catalyzed azide-alkyne click reaction

In this work,an effective,task specific,dicationic,podand-like ionic liquid was synthesized and applied to improve the capability features of click reaction.Moreover,to broaden the scope and decreasing the serious limitations of preparation methods of organic azides,a simple green procedure for the preparation of alkyl azides,the fundamental starting materials in click reactions,from alcohols under solvent-free conditions and microwave irradiation has been reported,for the first time.

Dication-accelerated anion transport inside micropores for the rapid decontamination of pertechnetate

Over 70%of the treated contaminated water at the Fukushima Daiichi Nuclear Power Station contains radionuclides beyond the regulatory standard for discharge that need to be re-purified.Technetium-99(^(99)Tc),mainly in the form of pertechnetate Tc(VII)O_(4)^(-),is one of the main sources of long-term radiotoxicity that jeopardizes the environment and human health.Herein,we used a series of dicationic pyridinium(DCP)derivative groups(–Py^(+)C_(n)H_(2n)N^(+)Me_(3),n=2,3,and 5)to modify commercial Reillex 425 resins containing tertiary pyridyl groups to improve the adsorption performance of rhenium(Re,an analog of radioactive Tc)and Tc.As the quaternary pyridinium and ammonium sites in one DCP group can adsorb ReO_(4)^(-) simultaneously,DCP-modified Reillex 425(Reillex-Cn)exhibited high maximum adsorption capacities for Re under neutral conditions.Adsorption capacities reached 344.8,416.7,and 588.2 mg g^(-)1 for Reillex 425-C2,Reillex 425-C3,and Reillex 425-C5,respectively.Intraparticle diffusion of ReO_(4)^(-)/TcO_(4)^(-) in Reillex 425-Cn was verified to be the rate-limiting step of adsorption.However,adsorption can be adjusted by the length of the alkyl spacers between the two positively charged N sites in DCP.–Py^(+)C_(2)H_(4)N^(+)Me_(3) significantly enhanced intraparticle diffusion compared to–Py^(+)C_(5)H_(10)N^(+)Me_(3).The two positive sites in–Py^(+)C_(2)H_(4)N^(+)Me_(3) would be laterally distributed,leading to a smaller steric hindrance for ReO_(4)–/TcO_(4)^(-) transport inside the microporous channels.Meanwhile,the longer alkyl spacers in–Py^(+)C_(5)H_(10)N^(+)Me_(3) formed hydrophobic microphases,repulsing the hydrated ReO_(4)–/TcO_(4)^(-) anions.Thus,the adsorptions of both ReO_(4)^(-) and TcO_(4)^(-) on Reillex 425-C2 were faster than those on Reillex 425-C5.Moreover,Reillex 425-Cn exhibited an exothermic nature,good selectivity,excellent reusability,and strong salinity tolerance.This study provides a simple strategy to enhance the Tc removal performance of adsorbents containing abundant micropores,which implies enormous environmental and economic benefits.

Observation of CO2^++ dication in the dayside Martian upper atmosphere

Doubly charged positive ions(dications)are an important component of planetary ionospheres because of the large energy required for their formation.Observations of these ions are exceptionally difficult due to their low abundances;until now,only atomic dications have been detected.The Neutral Gas and Ion Mass Spectrometer(NGIMS)measurements made on board the recent Mars Atmosphere and Volatile Evolution mission provide the first opportunity for decisive detection of molecular dications,CO2^++in this case,in a planetary upper atmosphere.The NGIMS data reveal a dayside averaged CO2^++distribution declining steadily from 5.6 cm^−3 at 160 km to below 1 cm^−3 above 200 km.The dominant CO2^++production mechanisms are double photoionization of CO2 below 190 km and single photoionization of CO2^+at higher altitudes;CO2++destruction is dominated by natural dissociation,but reactions with atmospheric CO2 and O become important below 160 km.Simplified photochemical model calculations are carried out and reasonably reproduce the data at low altitudes within a factor of 2 but underestimate the data at high altitudes by a factor of 4.Finally,we report a much stronger solar control of the CO2^++density than of the CO2+density.

Gas Phase Activation of Methane Molecule with Lead Benzene Dication Complex Ion, [Pb(Benzene)₂]²⁺

Motivated by the search for ways of a more efficient usage of the ubiquitous, and unexploited resources of methane, recent progress in the gas-phase activation of methane by metal dication complex ion is discussed. The gas phase theoretical and experimental analysis on [Pb(Benzene)2]2+ was conducted. The [Pb(Benzene)2]2+ complex ions were prepared using a combination of the pick-up technique and high energy electron impact, and then held in a cold ion trap. Excitation with tuneable UV radiation resulted in the formation of [Pb(Benzene)2(H2O)]2+, [Pb(Benzene)2(H2O)2]2+, [Pb(Benzene)]+, Pb+ and Benzene+ ions when the experimental results were analysed. The two optimised geometries of [Pb(Benzene)2]2+ namely the C2V eclipse and C2 staggered were observed. Methane activation of [Pb(Benzene)2]2+ complex ion yielded [Pb(Benzene)2(Me)]2+. [Pb(Benzene)2(H2O)(Me)2]2+,? [Pb(Benzene)2(H2O)(Me)]2+, [PbBenzene(Me)3]2+ and [Pb(Benzene)(Me)]2+. The PEC calculated binding energy of methane to lead benzene dication complex ion was approximately 25.45% higher than the value recorded on DFT calculation. This difference was due to the charge differences on the lead metal centre. While the actual calculated charge on the Pb metal in the optimised geometry was 1.68 the charge of +2 on the Pb metal was considered in the PEC calculation.

Synchrotron radiation VUV double photoionization of some small molecules

The VUV double photoionizations of small molecules （NO, CO, CO2, CS2, OSC and NH3） were investigated with photoionization mass spectroscopy using synchrotron radiation. The double ionization energies of molecules were determined with photoionization efficiency spectroscopy. The total energies of these molecules and their parent dications （NO^2＋,CO^2＋,CO2^2＋, CS2^2＋, OSC^2＋and NH^2＋） were calculated using the Gaussian O3 program and Gaussian 2 （NO^2＋, CO^2＋, CO2^2＋,CS2^2＋,OSC^2＋ and NH3^2＋） were calculated using the Gaussian 03 program and Gaussian 2 calculations. Then, the adiabatic double ionization energies of the molecules were predicated by using high accuracy energy mode. The experimental double ionization energies of these small molecules were all in reasonable agreement with their respective calculated adiabatic double ionization energies. The mechanisms of double photoionization of these molecules were discussed based on a comparison of our experimental results with those predicted theoretically. The equilibrium geometries and harmonic vibrational frequencies of molecules and their parent dications were calculated by using the MP2 （full） method. The differences in configurations between these molecules and their parent dications were also discussed on the basis of theoretical calculations.

A Novel Method for Synthesis of 2,3,4-Trisubstituted Furans

Intermolecular addition-cyclization of 1, 3-dicarbonyl compounds with arylbromo- allenes in K2CO3 mediated condition afforded 2, 3, 4-trisubstituted furans in good yield.

Inclusion of methylviologen dication in a cadmium tetracyanoplatinate host clathrate showing photochromism and photoluminescence modulation

A cadmium tetracyanoplatinate host clathrate,(MV)[Cd_(2){Pt(CN)_(4)}_(3)]·2(H_(2)O)(1),including a methylviologen dication (MV^(2+)) was synthesized,and the crystal structures,photochromic and photoluminescence properties were investigated.In 1,the alternatively parallel stacking between the MV^(2+)dications as electron acceptors in the channels and the electron donors[Pt1(CN)_(4)]^(2-) units in the host frameworks give a unique donor-acceptor (DA) system.Under UV irradiation,the electron transfer between MV^(2+) and[Pt(CN)_(4)]^(2-) ions generates MV^(·+)radicals with a photochromic behavior from pale-yellow to blue.This process occurs through single-crystal-to-single-crystal (SCSC) transformation and obvious structure variation of viologen cations is successfully observed.Moreover,the spectral overlap between the emission bands of 1 and the absorption around 623 nm for the MV^(·+) radicals leads to a modulation of the photoluminescence.

Construction and Functionalization of Highly Strained N-Doped Zigzag Hydrocarbon Belts

Recent years have witnessed breakthroughs in the study of zigzag hydrocarbon belts.However,the synthesis of heterocycle-containing zigzag molecular belts remains very rare and challenging despite their interesting structures and potential applications in chemistry and materials science.Here,we report the expeditious construction of a highly strained belt[4]arene[4](1,4-dihydropyridine)structure using the fjords-stitching strategy.The synthesis comprised four-fold abnormal m-bromination of four Npivaloylaniline units and Pd_(2)(dba)_(3)/4-Me_(2)NC_(6)H_(4)Pt Bu_(2)-catalyzed intramolecular C-N bond-forming reactions.Subsequent functionalization through Narylations produced a variety of tetraza-embedded octahydrobelt[8]arenes.Further oxidation of p-methoxyphenyl-substituted belt[4]arene[4](1,4-dihydropyridine)with Ag[Al(O^(t)Bu^(F))^(4)]yielded a singlet diradical dication N-doped zigzag belt.

Host-guest complexes of a water soluble cucurbit[6]uril derivative with some dications of 1,ω-alkyldipyridines:~1H NMR and X-ray structures

Interactions between a symmetrical tetramethyl-substituted cucurbit[6]uril (host:TMeQ[6]) and 1,ω-alkylenedipyridine (ω = 2,4,6,8,10) dicationic guests were investigated using 1H NMR spectroscopy and single crystal X-ray crystallography. In these inclusion complexes,combined cavity and portal binding in TMeQ[6] were observed,and the length of the bridged alkylene was found to play an important role not only in balancing the overall hydrophilic/hydrophobic interaction between the host and the guest,but also in defining the structure of the resulting inclusion complexes. For the guest 1,2-ethylenedipyridine (Edpy),TMeQ[6] includes a positively charged pyridine ring of Edpy to form an unsymmetrical inclusion complex; for the guest 1,4-butylenedipyridine (Bdpy),TMeQ[6] includes a positively charged pyridine ring of Bdpy,but the different competitive interactions in and between the related inclusion complexes could lead to a fast exchange between the hosts and guests. For the guests with longer bridge chains,such as 1,6-hexamethylenedipyridine (Hdpy) or 1,8-octylenedipyridine (Odpy),a stable pseudorotaxane inclusion complex is formed by combining the hydrophobic cavity and the outer portal dipoleion interactions. However,for 1,10-decatylenedipyridine (Ddpy),the two TMeQ[6] host molecules include the two end pyridine rings of Ddpy and form a dumbbell inclusion complex.

Para-selective borylation of monosubstituted benzenes using a transient mediator

Herein,we conceptualized a transient mediator approach that has the capability of para-selective C–H functionalization of monosubstituted aromatics.This approach is enabled by in situ generation of a versatile sulfonium salt via highly electrophilic phenoxathiine or thianthrene dication intermediate which can be readily generated from its sulfoxide with trifluoromethanesulfonic anhydride.Preliminary mechanistic study implied that the remarkable para selectivity might be related to the incredible electrophilicity of thianthrene dication intermediate.The versatility of this approach was demonstrated via paraborylation of various monosubstituted simple aromatics combining the sulfonium salt formation with further photocatalyzed transformation.