Cyclohexane Solution Research Articles

Development of AgCl/poly(MMA-co-AM) hybrid pervaporation membranes containing AgCl nanoparticles through synthesis of ionic liquid microemulsions

AgCl nanoparticles were synthesized in a water-in-oil microemulsion using the ionic liquid 1-dodecyl-3-methyl imidazoium chloride (C12mimCl) as the surfactant and methyl methacrylate–acrylamide (MMA–AM) mixture as the oil phase. An aqueous AgNO3 solution was added to the microemulsion as the source of Ag+ ions. Subsequently, AgCl/poly(MMA-co-AM) hybrid membranes were prepared by in situ microemulsion polymerization, and applied for pervaporation of mixtures of benzene and cyclohexane. The effects of C12mimCl (CC12mimCl) and AgNO3 (CAgNO3) concentrations on the formation and morphology of AgCl nanoparticles were studied. The structure of AgCl/poly(MMA-co-AM) hybrid membranes was examined and analyzed with SEM and XRD. The swelling–sorption behavior of AgCl/poly(MMA-co-AM) hybrid membranes in the benzene and cyclohexane solutions, and their separation ability were measured. The AgCl nanoparticles that were formed in the ionic liquid-based microemulsion were found to be spherical with a mean diameter of 20nm within a narrow size range. The number of AgCl nanoparticles increased with increasing CC12mimCl, and the mean diameter of the AgCl nanoparticles increased with increasing CAgNO3. The AgCl/poly(MMA-co-AM) hybrid membranes were found to have a core–shell structure with AgCl as the core and poly(MMA-co-AM) as the shell. The AgCl nanoparticles were uniformly dispersed in the poly(MMA-co-AM) matrix. The AgCl/poly(MMA-co-AM) hybrid membranes displayed the characteristics of preferentially selective sorption–swelling benzene and demonstrated better pervaporation performance than that of the membrane without nanoparticles in separating the benzene/cyclohexane mixture.

Application of genetic algorithm in calculation of the phase behavior of binary and ternary polymer solutions

A genetic algorithm as an optimization procedure has been developed to predict the phase behavior of polymer solutions. The phase equilibrium diagrams of binary and ternary polymer solutions have been determined using the appropriate form of Flory–Huggins free-energy function for polymer solutions. A concentration and temperature dependent form of the interaction parameter has been used to reflect the effect of temperature and polymer properties in the free-energy form. The proposed genetic algorithm is applied to compare the phase behavior results of some typical polymer solutions with the results of the classical determination methods and then applied to some conventional ternary polymer solutions as polymer–solvent–nonsolvent systems. The proposed algorithm use a set of individual states as the initial chromosomes and uses the general rules as crossover, mutation, and with use of a fractional objective function determines the binodal points or the phase diagram boundaries of polymer solutions. The properties of an industrially relevant polymer solution, a polystyrene–cyclohexane solution, have been used to emphasize on the industrial application of the proposed algorithm. The algorithm has been used to predict the phase behavior of the two polymer–solvent–nonsolvent systems as polystyrene-butanone-methanol and polystyrene-butanone-propanol at three different temperatures and results show good agreement with the experimental observations. The algorithm also has the capability to predict both the concentration-independent and concentration-dependent interaction parameters among the different components. The genetic algorithm is an easy-to-use, state-of-art, and very fast optimization tool, and has very strong capability to solve nonlinear systems in chemical and polymer engineering topics.

TiO2 nanoparticle assisted solid phase photocatalytic degradation of polythene film: A mechanistic investigation

The solid-phase photocatalytic degradation of low density polyethylene (LDPE) with sol–gel synthesized TiO2 nanoparticles as photocatalyst was investigated under ultraviolet (UV) irradiation in ambient air conditions. TiO2 nanoparticles were synthesized by optimizing various parameters and the TiO2 nanoparticles were dispersed in LDPE using cyclohexane solution. This TiO2–PE nanocomposite was made in the form of thin films of 40μm size by facile solution casting method and studied photodegradation of these films. A comparative study on the photodegradation of two different sized TiO2 incorporated LDPE under UV radiation was carried out. Polyethylene film incorporated with TiO2 nanoparticles of size 50nm showed higher degradation rate under UV radiation. Partial oxidation was confirmed from the IR spectrum of the TiO2 incorporated polyethylene film after radiation exposure. SEM analysis and AFM nanoindentation measurements confirm the degradation. A possible mechanism of TiO2 assisted degradation of the polyethylene matrix has also been proposed.

Hydration States of Poly(N-isopropylacrylamide) and Poly(N,N-diethylacrylamide) and Their Monomer Units in Aqueous Solutions with Lower Critical Solution Temperatures Studied by Infrared Spectroscopy

The coil-to-globule transition of poly(N-isopropylacrylamide) (PNiPA) and poly(N,N-diethylacrylamide) (PdEA) in aqueous solutions has recently received substantial interest in its drastic change in the hydration state from a hydrated random coil to a hydrophobic globule for practical applications: drug delivery and tissue engineering. In this report, the hydration states of PNiPA and PdEA in aqueous solutions were investigated by IR spectroscopy in the amide I, N–H and C–H stretching band regions as compared with those of their repeat units, N-isopropylpropionamide (NiPP) and N,N-diethylpropylacrylamide (dEP) in aqueous and cyclohexane solutions in combined with their phase diagrams. The IR spectral changes in the amide I and C–H stretching band regions of N-alkylamides and N,N-dialkylamides including NiPP and dEP in aqueous solutions with varying concentration was characteristic due to different amide–amide interaction; the amide–amide interaction for N-alkylamide (C═O···H–N hydrogen bond) is stronger than that for N,N-dialkylamide (dipolar interaction). It is found that almost all amide groups of PNiPA in aqueous solution forms the intramolecular C═O···H–N hydrogen bond even in the coil state and that the amide group of PNiPA is less hydrated than that of PdEA in spite of the similar degree of hydration to alkyl groups. The IR spectral changes in the amide I and C–H stretching band regions of PNiPA and PdEA in aqueous solutions with heat are ascribed to the dehydration of the amide and alkyl groups from the coil state to the globule one.

An improved Stöber method towards uniform and monodisperse Fe3O4@C nanospheres

Significant progress has recently been made in the synthesis of Fe3O4@C nanospheres with uniform, monodisperse and tunable carbon shells. Fe3O4@C nanospheres were obtained by directly carbonizing Fe3O4@polymer which was synthesized by a versatile and economical Stober method with resorcinol and formaldehyde as precursors. The synthesis conditions in the formation of Fe3O4@polymer were systematically investigated. It was found that the yield of the Fe3O4@polymer is highly influenced by the concentration of ammonium hydroxide, and the monodispersity is mainly affected by the concentration of ammonium hydroxide and the citrate group sites outside the surfaces of the Fe3O4 nanospheres. Interestingly, carbonization of Fe3O4@polymer at high temperature makes the grain sizes of Fe3O4 in Fe3O4@C samples larger than those in the Fe3O4 sample, which makes the saturation magnetization value for the Fe3O4@C samples higher than those of common obtained materials. The adsorption performance of Fe3O4@C for anthracene was tested both in water and in cyclohexane solution; it shows fast adsorption rates (about 1 h to reach equilibrium in water and 3 h in cyclohexane solution) and high adsorption capacities (31.5 mg g−1 in water and 2 mg g−1 in cyclohexane solution), which are ascribed to its high uniformity and monodispersity. These make Fe3O4@C an ideal adsorption and enrichment material, especially for polycyclic aromatic hydrocarbons in water and in organic solvents.

C,C′-Bis(benzodiazaborolyl)dicarba-closo-dodecaboranes: Synthesis, structures, photophysics and electrochemistry

Six new C,C'-bis(benzodiazaborolyl)dicarba-closo-dodecaboranes, 1,A-R2-1,A-C2B10H10, where R represents the group 2-(1,3-Et2-1,3,2-N2BC6H4) or 2-(1,3-Ph2-1,3,2-N2BC6H4) and A is 2, 7 or 12, were synthesized from o-, m-, and p-dicarbadodecaboranes (carboranes) by lithiation and subsequent treatment with the respective 2-bromo-1,3,2-benzodiazaboroles. UV-visible and fluorescence spectra of all carboranes display low energy charge transfer emissions. While such emissions with Stokes shifts between 17,330 and 21,290 cm(-1) are typical for C,C'-bis(aryl)-ortho-carboranes, the observed low-energy emissions with Stokes shifts between 8320 and 15,170 cm(-1) for the meta- and para-isomers are unusual as high-energy emissions are typical for meta- and para-dicarbadodecaboranes. Fluorescence quantum yields (φF) for the novel 1,7- and 1,12-bis(benzodiazaborolyl)-carboranes depend on the substituents at the nitrogen atoms of the heterocycle. Thus, the para-carborane with N-ethyl substituents 1,12-(1',3'-Et2-1',3',2'-N2BC6H4)2-1,12-C2B10H10 has a φF value of 41% in cyclohexane solution and only of 9% in the solid state, whereas the analogous 1,12-(1',3'-Ph2-1',3',2'-N2BC6H4)2-1,12-C2B10H10 shows quantum yields of 3% in cyclohexane solution and 72% in the solid state. X-ray crystallographic, computational and cyclic voltammetry studies for these carboranes are also presented.

Comparing molecular photofragmentation dynamics in the gas and liquid phases

This article explores the extent to which insights gleaned from detailed studies of molecular photodissociations in the gas phase (i.e. under isolated molecule conditions) can inform our understanding of the corresponding photofragmentation processes in solution. Systems selected for comparison include a thiophenol (p-methylthiophenol), a thioanisole (p-methylthioanisole) and phenol, in vacuum and in cyclohexane solution. UV excitation in the gas phase results in RX-Y (X = O, S; Y = H, CH3) bond fission in all cases, but over timescales that vary by ~4 orders of magnitude - all of which behaviours can be rationalised on the basis of the relevant bound and dissociative excited state potential energy surfaces (PESs) accessed by UV photoexcitation, and of the conical intersections that facilitate radiationless transfer between these PESs. Time-resolved UV pump-broadband UV/visible probe and/or UV pump-broadband IR probe studies of the corresponding systems in cyclohexane solution reveal additional processes that are unique to the condensed phase. Thus, for example, the data clearly reveal evidence of (i) vibrational relaxation of the photoexcited molecules prior to their dissociation and of the radical fragments formed upon X-Y bond fission, and (ii) geminate recombination of the RX and Y products (leading to reformation of the ground state parent and/or isomeric adducts). Nonetheless, the data also show that, in each case, the characteristics (and the timescale) of the initial bond fission process that occurs under isolated molecule conditions are barely changed by the presence of a weakly interacting solvent like cyclohexane. These condensed phase studies are then extended to an ether analogue of phenol (allyl phenyl ether), wherein UV photo-induced RO-allyl bond fission constitutes the first step of a photo-Claisen rearrangement.

Synthesis of Ag@SiO2 hybrid nanoparticles templated by a Triton X-100)/1-hexanol/cyclohexane/H2O water-in-oil microemulsion

A water-in-oil microemulsion was prepared by using nonionic surfactant Triton X-100, 1-hexanol, cyclohexane and AgNO3 aqueous solution with a concentration of 0.2 mol L−1. Successive addition of sodium borohydride (NaBH4), ammonium hydroxide (NH3·H2O) and tetraethyl orthosilicate (TEOS) to this microemulsion leads to the formation of hierarchically-organized Ag@SiO2 hybrid nanoparticles with Ag nanocrystals randomly distributed inside amorphous SiO2, as proved by transmission electron microscopy (TEM) and high-resolution electron microscopy (HRTEM) observations. In many cases, H2 gas bubbles, which were produced during the reduction of Ag+, were found to influence the structures of Ag nanocrystals. The morphologies of the hybrid nanoparticles and the H2-induced cavities can be easily tuned by the molar ratio of AgNO3 to NaBH4 and the volume ratio of AgNO3 aqueous solution to TEOS. Embedded in amorphous SiO2, the Ag nanoparticles are highly stable, while the unprotected Ag nanocrystals underwent fast aggregation. The inner Ag nanocrystals have dominant (111) planes and are optically active, as shown by X-ray powder diffraction (XRD) and UV-vis measurement, respectively. These properties make these Ag@SiO2 hybrid nanoparticles fascinating candidates for a variety of applications in catalysis and life science.

Facile synthesis of spherical nanoparticles with a silica shell and multiple Au nanodots as the core

Highly spherical nanoparticles with a core comprising multiple gold (Au) nanodots and a silica shell (multi-Au@SiO2 NPs) were successfully synthesized through a reverse (water-in-oil) microemulsion-based method. The microemulsion was prepared by mixing a surfactant (Brij35), cyclohexane, n-hexanol, and aqueous HAuCl4 solution. Multiple Au nanodots with a maximum diameter of ∼5 nm could be encapsulated within a silica matrix during the growth process. The size of the multi-Au@SiO2 NPs and the number of Au nanodots doped could be controlled by varying the water-to-Brij35 ratio and the amount of the precursor of cationic gold ions. This is a novel and simple synthetic approach for generating hybrid Au–silica nanomaterials by encapsulating multiple Au nanoparticles within a silica matrix.

On the Primary Reaction Pathways in the Photochemistry of Nitro-Polycyclic Aromatic Hydrocarbons

The primary reaction pathways in the photochemistry of nitro-polycyclic aromatic hydrocarbons under specific laboratory conditions are briefly summarized. In addition, photochemical data is presented for 2-nitronaphthalene, 1-nitronaphthalene, and 2-methyl-1-nitronaphthalene in cyclohexane and acetonitrile solutions under aerobic and anaerobic conditions. It is shown that molecular oxygen significantly reduces the photodegradation quantum yield of 1-nitronaphthalene and 2-methyl-1-nitronaphthalene by 63% and 81%, respectively, whereas 2-nitronaphthalene is photoinert in both solvents under aerobic and anaerobic conditions. In addition, it is proposed that recombination of the aryl and nitrogen (IV) dioxide geminate radical pair within the solvent cage or internal conversion of an initially formed intramolecular charge transfer state may play an important role in the fraction of excited molecules that returns to the ground state in 1-nitronaphthalene and 2-methyl-1-nitronaphthalene. Scavenging of radical species by molecular oxygen and the generation of singlet oxygen in high yield are proposed to contribute to the photochemistry of these nitro-naphthalene derivatives in solution.

Synthesis, structure and adsorption of coordination polymers constructed from 3,3′,5,5′-azobenzenetetracarboxylic acid and Zn ions

3,3′,5,5′-Azobenzenetetracarboxylic acid (H4abtc) was synthesized by reduction of 5-nitroisophthalic acid in basic aqueous/ethanol solution in the presence of Zn powder. Three novel coordination polymers {[Zn2(η6-ao2btc)(η2-2,2′-bpy)2(H2O)2]·2H2O}1n (1), {[Zn2(η8-aobtc)(η2-phen)(H2O)]·DMF}3n (2), and {(Hap)2[Zn3(η9-aobtc)2]·2H2O}3n (3) (2,2′-bpy = 2,2′-bipyridine, phen = 1,10-phenanthroline, ap = 4-aminopyridine, ao2btc4− and aobtc4− are two oxidized forms of H4abtc ligand) were prepared under hydrothermal conditions. The structures of 1–3 were characterized by single-crystal X-ray diffraction. Complex 1 is a 1D chain polymer, while 2 and 3 are porous 3D metal–organic frameworks with a cavity size of 9 A diameter and 7 × 15 A rectangular cavities, respectively. In 1, ao2btc4− links four mononuclear ZnO6 chromophores. Ligand aobtc4− in 2 links four dinuclear Zn2(CO2)4(H2O)N2, while aobtc4− in 3 bridges four trinuclear Zn3(CO2)8. From a topology point of view, ao2btc4− or aobtc4− are all 4-connected linkers in 1–3, while the mononuclear ZnO6 in 1, dinuclear Zn2(CO2)4(H2O)N2 in 2 and trinuclear Zn3(CO2)8 in 3 are 2, 4 and 8 connected nodes, respectively. Zn(II) in complex 2 can be replaced by Cu(II), Ni(II) and Co(II) with simultaneous loss of crystallinity. The metal ion exchange rate decrease in the order Co(II) < Ni(II) < Cu(II). 2 can encapsulate iodine (I2) in cyclohexane solution to form 2⊃0.1I2. The encapsulated I2 can be released completely in ethanol. The Hap+ in 3 can be replaced by methylene blue in aqueous solution to form 3⊃0.1methylene blue. The insignificant replacement is an indication that the guest molecule in the cavity channel is immobile, which prevents further substitution. With a bis-oxo group in the azo moiety, the framework of 1 is so unstable that it will decompose at ∼150 °C with simultaneous release of NO. Complexes 2 and 3 are stable at 330 °C. IR and fluorescence spectra were also discussed.

Improved hollow fiber supported liquid–liquid–liquid membrane microextraction for speciation of inorganic and organic mercury by capillary electrophoresis

An improved hollow fiber supported liquid–liquid–liquid membrane microextraction (HF-LLLMME) method is described for the simultaneous extraction of inorganic and organic mercury species with high efficiency prior to speciation analysis by capillary electrophoresis. The HF-LLLMME was developed by filling cyclohexane and L-cysteine aqueous solution in the pores of the hollow fiber wall and its lumen as organic liquid membrane and acceptor phase, respectively. Inorganic mercury (Hg2+), methylmercury (MeHg), ethylmercury (EtHg) and phenylmercury (PhHg) firstly formed hydrophobic complexes with 1-(2-pyridylazo)-2-naphthol in donor solutions, wherein the hollow fiber was immersed. The complexes were then extracted into the organic liquid membrane and further transferred into the lumen of the hollow fiber to form hydrophilic complexes with L-cysteine. The factors affecting the extraction efficiency were carefully investigated. With the consumption of 50 mL of sample solution, the enrichment factor was 103, 265, 511 and 683 for Hg2+, MeHg, EtHg and PhHg, respectively. The limits of detection were in the range of 0.07–1.0 ng mL−1 (as Hg) with precisions (RSDs, n = 6) ranging from 1.7 to 4.4%. The proposed method was validated by analyzing a certified reference material (DORM-2, dogfish-muscle) and an environmental water sample with satisfactory results.

13C NMR relaxation and computational study of anisole and derivatives in the solution state

13C NMR spin–lattice relaxation times and nuclear Overhauser effects were measured at several temperatures for the methoxyl methyl carbon and the phenyl ring carbons in neat samples and in dilute cyclohexane solution for anisole, 4‐methylanisole, and 4‐chloroanisole. Similar measurements were made for 2‐methylanisole, 2‐methyl‐4‐bromoanisole, and 2,4,6‐trimethylanisole in dilute cyclohexane solution. Density functional theory (DFT) computations were performed on anisole, 4‐chloroanisole and 2,4,6‐trimethylanisole to obtain the minimum energy structures and the potential energy barriers to the internal rotations of the methoxyl group. The shortest distance between a methoxyl methyl hydrogen and the ortho hydrogen in anisole is 1.920 Å. The DFT results point to steric interactions that arise thereof as the principal source of the energy barriers to the internal rotation of the methyl or of the methoxyl group. The carbon relaxation data are consistent with the existence of noncovalent intermolecular interaction, especially π − π stacking interaction. The nuclear magnetic resonance and DFT results are discussed with reference to the rotational characteristics of the methoxyl methyl and the anisotropy in the reorientational motion of anisole and its derivatives in dilute cyclohexane solution. Copyright © 2012 John Wiley &amp; Sons, Ltd.

Room-temperature catalytic oxidation of benzo(a)pyrene by Ce-SBA-15 supported active CeSiO4 phase

A series of cerium-incorporated SBA-15 mesoporous materials were prepared through direct hydrothermal synthesis method, which was characterized by PXRD, N2 physisorption and TEM measurements. The low-angle PXRD and N2 physisorption results show the cerium successfully incorporated into the framework of SBA-15. The large angle PXRD results indicate that Ce-SBA-15 mesoporous materials supported CeSiO4 phase was in situ synthesized by adjusting pH to 6 with anhydrous triethylamine, and then calcined in air at 550°C. The room-temperature adsorption behaviors of SBA-15 and Ce-SBA-15 materials for benzo(a)pyrene in cyclohexane solutions were investigated. Interestingly, Ce-SBA-15 materials reveal good catalytic performance for room-temperature oxidation benzo(a)pyrene to corresponding quinone through a radical oxidation mechanism, attributable to in situ forming active CeSiO4 phase which was supported in Ce-SBA-15 material. The benzo(a)pyrene transfer to quinone by CeSiO4 phase leads to higher adsorption capacity owing to higher affinity of quinone with mesoporous channels, as a result, some Ce-SBA-15 materials exhibit higher adsorption capacity for benzo(a)pyrene than SBA-15 material. The radical oxidation mechanism was demonstrated by EPR and the interception effect of a radical scavenger, TEMPO. The quinone-type molecule was identified by photoluminescence, ESI-MS, IR and NMR.

Non-contact detection of chemical warfare simulant triethyl phosphate using PM-IRRAS

Polarization modulation-infrared reflection absorption spectroscopy (PM-IRRAS) was employed to detect the chemical warfare agent (CWA) simulant triethyl phosphate (TEP) on gold, as well as on US military paint, i.e., chemical agent resistant coating (CARC). The targeted CWAs (G and V-series nerve agents) are characterized by phosphoric group vibrations present in the 1200cm−1 region. TEP displays two prominent peaks at 1268cm−1 and 1036cm−1 corresponding to PO and (P)OC vibrations, respectively. A droplet of TEP solution in cyclohexane was deposited on gold and CARC substrates and after solvent evaporation PM-IRRAS spectra were collected in the 1200cm−1 region. The integrated peak area of the PO and (P)OC vibrations was used to construct calibration curves and to determine the experimental limit of detection (LoD). In the case of gold as the substrate the estimated LoD of ∼0.48μg and 1.23μg was obtained for the PO and (P)OC vibrations, respectively. In the case of CARC, a LoD of 24μg was determined. These detection limits are at least 3 orders of magnitude lower than the typical lethal dose of G and V-series nerve agents, demonstrating potential of PM-IRRAS for non-contact detection of these CWAs.

State of adsorption layers of fatty acids on the surfaces of iron, manganese, and copper ferrites

States of adsorbed substances in surface layers arising during the adsorption of oleic, linoleic, and linolenic acids from carbon tetrachloride, heptane, and cyclohexane solutions on the surfaces of iron, manganese, and copper ferrites, are investigated. Adsorption isotherms and two-dimensional state diagrams of surface layers of iron, manganese, and copper ferrites are obtained experimentally. It is shown that the adsorption of fatty acids from solutions in organic solvents proceeds via filling the volume of the ferrites’ porous space with adsorption solutions, while the state of ferrite surface layers changes due to the structural rearrangement of adsorption solutions upon an increase in solute concentration.

Novel dipyrazolopyridine derivatives as deep blue emitters for polymer based organic light emitting diodes

Paper reports synthesis and spectroscopic properties of four newly synthesized dipyrazolo[3,4-b; 3′,4′-e]pyridine (DPP) derivatives. The spectroscopic studies are supplemented by quantum-chemical calculations using DFT/TDDFT/PCM method at the B3LYP/6-31+G(d,p) level of theory. The optical absorption and fluorescence emission processes appear to be weakly dependent on attached side phenyl and/or methyl groups exhibiting in cyclohexane solution the first absorption band (00′ transition) in the region of 386–401nm and the fluorescence band (0′0 transition) in the range of 412–425nm. The electroluminescence devices (OLEDs) with an active PVK layer doped by DPP dyes have been designed. All the devices exhibit deep blue electroluminescence with the emission maximum being rather weakly dependent on the type of the fluorescent dopant. The obtained results demonstrate that a series of newly synthesized DPP dyes may be considered as perspective blue fluorescent emitters for electroluminescent applications.

Fluorescence Spectroscopic and Time-Dependent Density-Functional Theory Studies of Diphenylsilane

We investigated fluorescence and fluorescence excitation of diphenylsilane (DPS) in a solution and molecular beams in combination with the aid of the DFT method. When the molecule was photoexcited at 250 nm in a cyclohexane solution, normal and excimer fluorescences were observed in the ranges of 260-320 and 330-450 nm, respectively. The fluorescence excitation spectrum indicates that the channel leading to the intramolecular excimer formation is not efficient in comparison with the normal fluorescence. Vibrationally resolved fluorescence excitation spectra were measured for the DPS molecules cooled in pulsed supersonic expansion of He in the range 262.2-271.7 nm, in which we can see several electronic excitation spectra exhibiting the electronic band origins. We found that the simulated absorption spectrum based on the time-dependent densityfunctional theory calculations accords well with the absorption spectrum.

Hydrodesulfurization catalyst prepared by urea-matrix combustion method

Co–Mo/γ-Al2O3–TiO2 hydrodesulfurization (HDS) catalyst samples prepared by a urea matrix combustion (UMxC) method, were evaluated in a stainless tubular fixed-bed reactor, with thiophene, benzothiophene and dibenzothiophene in xylene as model feedstocks. The samples were pre-sulfurized using a cyclohexane solution of 3% CS2 and then tested for the HDS reaction. The test results were compared with catalysts prepared by conventional methods involving sequential impregnation (SI) and co-impregnation (CI). The catalysts were characterized using X-ray diffraction (XRD), laser Raman spectroscopy (LRS), high resolution transmission electron microscopy (HRTEM) and N2 physisorption, showing that the UMxC catalyst had higher pore volume and surface area than those prepared by the CI and SI methods. The UMxC method increased metal loading and avoided formation of inert phase, e.g., β-CoMoO4, for the HDS reaction, suggesting that UMxC method is superior to the conventional impregnation techniques. TiO2 promoter made particles on the catalyst surface closer and alleviated the interaction between molybdenum oxide and the support, and facilitated the formation of well-dispersed Co- and Mo-oxo species on catalyst surface, thus resulting in higher HDS catalytic activity than pure γ-Al2O3 support without modifiers. Consequently, the addition of TiO2 obviously improved the HDS conversion of dibenzothiophene.

Toward an Accurate Modeling of Optical Rotation for Solvated Systems: Anharmonic Vibrational Contributions Coupled to the Polarizable Continuum Model.

We present a newly implemented methodology to evaluate vibrational contributions (harmonic and anharmonic) to the optical rotation of solvated systems described by means of the polarizable continuum model (PCM). Proper account of an incomplete solvation regime in the treatment of both the electronic property and the molecular vibrations is considered, as well as the inclusion of cavity field effects. In order to assess the quality of our approach, test calculations on (R)-methyloxirane in various solvents and (S)-N-acetylproline amide in cyclohexane and aqueous solution are presented. The comparison with experimental findings is also shown.