Liu Honglai

Non-equilibrium thermodynamics analysis and its application in interfacial mass transfer

Interfacial transfer plays an important role in multi-phase chemical processes. However, it is difficult to describe the complex interfacial transport behavior by the traditional mass transfer model. In this paper, we describe an interfacial mass transfer model based on linear non-equilibrium thermodynamics for the analysis of the rate of interfacial transport. The interfacial transfer process rate J depends on the interface mass transfer coefficient K, interfacial area A and chemical potential gradient Δµ at the interface. Potassium compounds were selected as model systems. A model based on linear non-equilibrium thermodynamics was established in order to describe and predict the transport rate at the solid-solution interface. Together with accurate experimental kinetic data for potassium ions obtained using ion-selective electrodes, a general model which can be used to describe the dissolution rate was established and used to analyze ways of improving the process rate.

Surfactant Adsorption onto Interfaces: Measuring the Surface Excess in Time

We propose a direct method to measure the equilibrium and dynamic surface properties of surfactant solutions with very low critical micellar concentrations (CMC) using a pendant drop tensiometer. We studied solutions of the nonionic surfactant hexaethylene glycol monododecyl ether (C(12)E(6)) and of the ionic surfactant hexadecyl trimethyl ammonium bromide (CTAB) with concentrated sodium bromide (NaBr). The variation of the surface tension as a function of surface concentration is obtained easily without the need for complex models and compares well with the result obtained using the Gibbs adsorption equation. The time-dependent surface concentration of each surfactant was also measured, and the adsorption process was found to be diffusion-controlled. The diffusion coefficients of the two surfactants can be extracted from the data and were found in very good agreement with literature values, further validating the method.

CO 2 capture through halogen bonding: A theoretical perspective

Halogen bonding interactions between several halogenated ion pairs and CO2 molecules have been investigated by means of density functional theory calculations. To account for the influence of solvent environment, the implicit polarized continuum model was also employed. The bromide and iodide cations of ionic liquids (ILs) under study can interact with CO2 molecules via X…O interactions, which become much stronger in strength than those in the complexes of iodo-perfluorobenzenes, very effective halogen bond donors, with CO2 molecules. Such interactions, albeit somewhat weaker in strength, are also observed between halogenated ion pairs and CO2 molecules. Thus, the solubility of CO2 may be improved when using halogenated ILs, as a result of the formation of X…O halogen bonds. Under solvent effects, the strength of the interactions tends to be weakened to some degree, with a concomitant elongation of intermolecular distances. The results presented here would be very useful in the design and synthesis of novel and potent ILs for CO2 physical absorption.

Electronic Absorption Spectra of Meso -Substituted Porphyrins and Their Zinc Derivatives

Meso-substituted porphyrin derivatives have demonstrated great potential as sensing materials for toxic gas detection.In this paper,density functional theory(DFT)and its time-dependent DFT approach(TD-DFT)were employed to investigate the ultraviolet-visible(UV-Vis)or the near-ultraviolet-visible(near-UV-Vis)absorption spectra of meso-tetra(o-nitrophenyl/o-aminophenyl)porphyrins(NO 2 PP,NH 2 PP)and their corresponding zinc derivatives,NO 2 ZnPP and NH 2 ZnPP.The geometry optimizations for these four molecules were obtained from two different exchange-correlation functionals,the generalized-gradient approximation functional PBE(Perdew-Burke-Ernzerhof)and the hybrid functional B3LYP(Becke,three-parameter,Lee-Yang-Parr).The excitation energies and oscillation strengths were obtained from TD-DFT calculations.Calculations show that the optical absorptions are associated with numerous electronic transitions.In addition,the PBE-predicted wavelengths of the B and Q bands are more consistent with experiment than those predicted by B3LYP.The B band of NO 2-substituted derivative exhibits a bathochromic shift different from that of NH 2-containing material,also consistent with experimental results.In addition,at the PBE/6-31G(d)level of theory,the calculated energies of the lowest triplet excited states of NO 2 PP,NH 2 PP,NO 2 ZnPP,and NH 2 ZnPP are 1.426,1.469,1.608,and 1.581 eV,respectively.

One-Step Synthesis of Metal-Doped Mesoporous MCM-41 Materials and Their Application in Esterification Catalysis

Metals (Fe, Ti, Zr) were doped into mesoporous MCM-41 by a one-step method using cetyltriethylammonium bromide (CTAB) micelles with micellar solubilized metallocenes as templates. X- ray diffraction (XRD) and N2 adsorption-desorption isotherms show that after metallocene doping, M- MCM-41(T ) materials still preserved the ordered hexagonal structure and high BET surface area. Inductively coupled plasma atomic emission spectrometry (ICP-AES) indicated that the mass fractions of the metals in the corresponding samples are: 1.71% Fe in Fe-MCM-41(400), 0.95% Ti in Ti-MCM-41(550) and 0.81% Zr in Zr-MCM-41(550). All the M-MCM-41(T) materials showed a particular high catalysis effect for the esterification of acetic acid and n-butanol. The TOF of Fe-MCM-41(400) and Zr-MCM-41(550) were 55643 g·h - 1 ·g - 1 and 125320 g·h - 1 ·g - 1 , respectively, which is much higher than that of the corresponding pure metallocenes.Metals(Fe,Ti,Zr) were doped into mesoporous MCM-41 by a one-step method using cetyltriethylammonium bromide(CTAB) micelles with micellar solubilized metallocenes as templates.X-ray diffraction(XRD) and N2 adsorption-desorption isotherms show that after metallocene doping,M-MCM-41(T) materials still preserved the ordered hexagonal structure and high BET surface area.Inductively coupled plasma atomic emission spectrometry(ICP-AES) indicated that the mass fractions of the metals in the corresponding samples are:1.71% Fe in Fe-MCM-41(400),0.95% Ti in Ti-MCM-41(550) and 0.81% Zr in Zr-MCM-41(550).All the M-MCM-41(T) materials showed a particular high catalysis effect for the esterification of acetic acid and n-butanol.The TOF of Fe-MCM-41(400) and Zr-MCM-41(550) were 55643 g·h-1·g-1 and 125320 g·h-1·g-1,respectively,which is much higher than that of the corresponding pure metallocenes.

Controlled synthesis of uniform silver nanowires with high aspect ratios in aqueous solutions of gemini surfactant

A simple solution-phase approach has been demonstrated for the large-scale synthesis of silver nanowires with diameters in the range of 15–25 nm, and lengths usually in the range of tens of micrometers. In the presence of gemini surfactant 1,3-bis(cetyldimethylammonium) propane dibromide (16-3-16), the growth of silver could be directed into a highly anisotropic mode to form uniform nanowires with aspect ratios up to about 2,000. X-ray photoelectron spectroscopy (XPS), transmission electron microscopy (TEM), energy-dispersive X-ray (EDX), X-ray powder diffraction (XRD), electron diffraction (ED), and UV-vis absorption spectroscopy, were used to characterize the as-prepared silver nanowires, indicating the formation of a highly pure phase, good crystallinity, as well as a uniform diameter.

Morphologies of diblock copolymer confined in a slit with patterned surfaces studied by dissipative particle dynamics

Diblock copolymers with ordered mesophase structures have been used as templates for nano-fabrication. Unfortunately, the ordered structure only exists at micromete rscale areas, which precludes its use in many advanced applications. To overcome this disadvantage, the diblock copolymer confined in a restricted system with a patterned surface is proved to be an effective means to prohibit the formation of defects and obtain perfect ordered domains. In this work, the morphologies of a thin film of diblock copolymer confined between patterned and neutral surfaces were studied by dissipative particle dynamics. It is shown that the morphology of the symmetric diblock copolymer is affected by the ratio of the pattern period on the surface to the lamellar period of the symmetric diblock copolymer and by the repulsion parameters between blocks and wall particles. To eliminate the defects in the lamellar phase, the pattern period on the surface must match the lamellar period. The difference in the interface energy of different compartments of the pattern should increase with increasing film thickness. The pattern period on the surface has a scaling relationship with the chain length, which is the same as that between the lamellar period and the chain length. The lamellar period is also affected by the polydispersity of the symmetric diblock copolymer. The total period is the average of the period of each component multiplied by the weight of its volume ratio. The morphologies of asymmetric diblock copolymers are also affected by the pattern on the surface, especially when the matching period of the asymmetric diblock copolymer is equal to the pattern period, which is approximately equal to the lamellar period of a symmetric diblock copolymer with the same chain length.

Effect of Catalysts on the Morphologies of Carbon Materials Synthesized by an Emulsion Templating Method

An oil in water(O/W) emulsion with a resorcinol and formaldehyde(R+F) water solution as the external phase and liquid paraffin as the internal phase together with Span 80/Tween 80 as emulsifiers was obtained.Carbon materials were prepared by polymerization of the emulsion,followed by carbonization for template removal.The effect of catalysts on the morphologies of the carbon materials was investigated.The results indicate that the resultant representative carbons are a type of porous carbon foam and possess pore walls and pores of 1-2 μm in size when NaOH is used as a catalyst.However,monolithic carbon materials consisting of microspheres or intertwinded wormlike particles were prepared using ammonia as an alternative catalyst.The diameters of these microspheres or particles were mainly around 1-2 μm and these dimensions are similar to the pore sizes of the carbon foams.We find that ammonia causes the initial O/W emulsion system to experience a phase inversion toward a W/O high internal phase emulsion.A mechanism involving intermolecular H-bond interactions and cohesive energy theory is proposed to explain the catalyst-induced phase inversion phenomenon as well as the formation of carbon materials with different morphologies.

Effect of steady shear on multi-axial texture of symmetric diblock copolymers

The effect of steady shear on multi-axial texture of symmetric diblock copolymer was investigated by using dynamic density functional theory. Through modifying the periodic boundary condition, the parallel-transverse biaxial texture and perpendicular-parallel-transverse triaxial texture have been observed. In the formation of the multi-axial texture, there are two critical velocities uper-par* and upar-tra*, at which the transition between the perpendicular and the parallel lamellar morphology, and the transition between the parallel and the transverse lamellar morphology occur, respectively. The two critical velocities increase as the interaction parameter increases, but they almost remain constant at different shear rates. Furthermore, the rotation from the transverse lamellae to the parallel lamellae induced by the shear strain, and the increase of lamellar spacings of the three lamellae after removing the shear, have also been observed by the time evolution of the morphologies. These phenomena are consistent with experimental work.