Wumanjiang Eli

Solvent-free esterification catalyzed by surfactant-combined catalysts at room temperature

Solvent-free esterifications of various carboxylic acids and alcohols can be catalyzed by surfactant-combined catalysts dodecylbenzene sulfonic acid (DBSA) and copper dodecylbenzene sulfonate (CDBS) in moderate to excellent yield at room temperature. The esterification method has two notable advantages: first, there is no need for any solvent, even water, and secondly, no need for energy, the reaction can proceed smoothly at room temperature.

Production of 5-hydroxymethylfurfural from fructose by a thermo-regulated and recyclable Brønsted acidic ionic liquid catalyst

In this work, a thermo-regulated recyclable catalytic system using ionic liquid [HO2CMMIm]Cl as the catalyst and isopropanol as the solvent has been demonstrated to be effective for the dehydration of fructose to synthesize 5-hydroxymethylfurfural (HMF). The solubility of [HO2CMMIm]Cl ionic liquid in isopropanol is temperature-dependent, being miscible with isopropanol at a temperature range suitable for fructose dehydration (e.g., above 80 °C) while not soluble at lower temperatures such as room temperature. Temperature-responsive solubilization/precipitation of [HO2CMMIm]Cl in isopropanol renders the acidic ionic liquid an appealing thermo-regulated phase-switchable catalyst. Furthermore, the effects of various parameters including catalyst loading, fructose concentration, reaction time and temperature on the catalytic performance of fructose dehydration have been studied systematically. Under optimized reaction conditions, up to 91.2 mol% HMF yield could be obtained. Additionally, when the ionic liquid catalyst precipitated out after the reaction, the solvent can be simply decanted and [HO2CMMIm]Cl could be directly reused for the next run with freshly added solvent and substrate. It was found that [HO2CMMIm]Cl could be reused at least five times without considerable loss of activity. Furthermore, a kinetic analysis was carried out, indicating the activation energy for the reaction to be 62.1 kJ mol−1. This catalytic system can be envisioned to find applications in a wide range of acid-catalyzed reactions with facile, thermo-regulated catalyst recovery features.

Study on the Polarity of bmimPF6/Tween80/toluene Microemulsion Characterized by UV-Visible Spectroscopy

With the aid of nonionic surfactant Tween80, the ionic liquid 1-butyl-3-methylimidazolium hexafluorophosphate (bmimPF6) forms nonaqueous microemulsions with toluene. The phase diagram of the ternary system was prepared at 25°C. It was demonstrated that there were a single-phase region and a two-phase region in the ternary phase diagram. The single-phase region could be further divided into toluene-in-bmimPF6, bicontinuous and bmimPF6-in-toluene microemulsion regions by electrical conductivity. And by the use of methyl orange as an absorption probe, the polarity of the bmimPF6-in-toluene microemulsion was probed by UV-vis spectroscopy. A relatively constant polarity of the microemulsion droplets is obtained in the bmimPF6 microemulsion.

Determination of Association Constants of Cyclodextrin-Nonionic Surfactant Inclusion Complexes by a Partition Coefficient Method

The partition behavior of isotopic labeled nonionic surfactants between carbon tetrachloride and an aqueous solution containing β-cyclodextrin (β-CD) was studied with a liquid scintillation counting technique. The association constants of the inclusion complexes were determined at different temperatures. It was found that the nonionic surfactants form 1 : 1 inclusion complexes with β-CD. The results demonstrated that the smaller the HLB values of the nonionic surfactants, the greater the association constants with β-CD, and that for the same surfactant the association constant is higher at lower temperatures.

The Association of Triton X Surfactants with β-Cyclodextrin. An Isothermal Titration Calorimetry Study

The association with β-cyclodextrinof a series of Triton X surfactants with differentethylene oxide (EO) chain lengths was studied byisothermal titration calorimetry at 298.15 K. Theresults agree with a 1:1 association model.Association constants and changes in Gibbs freeenergies, enthalpies and entropies were derived forthe association process. Association of thesesurfactants with β-cyclodextrin have favorableenthalpy changes and unfavorable entropy changes. Theshorter the EO chain of the surfactant, the greaterthe association constant with β-cyclodextrin.

Tandem hydroformylation and hydrogenation of dicyclopentadiene by Co3O4 supported gold nanoparticles

A co-precipitation method was used to prepare a series of Co3O4 supported gold nanoparticles (Au/Co3O4), which were subsequently evaluated on their performance for “one-pot” synthesis of tricyclodecanedimethylol (TDDMO) from dicyclopentadiene (DCPD). Characterization methods including FTIR, XPS and TG-DTA were performed on the Au/Co3O4 catalyst during the course of reaction to reveal that three distinct stages of catalysis occurred while the catalyst possessed different physiochemical properties. The “one-pot” synthesis of TDDMO was successfully realized with selectivity over 90% under relatively mild reaction conditions of 140–150 °C reaction temperature and 7–9 MPa pressure. Experimental data suggested that the catalytically active species might be a Co(CO)x(PPh)y complex where the presence of gold can assist the in situ reduction of Co3O4 to metallic cobalt under reaction conditions, thereby increasing the number of active sites. Another role of Au was proposed as facilitating hydrogenation of an in situ formed intermediate aldehyde, diformyltricyclodecanes (DFTD), to produce the final product TDDMO.

Hydroesterification of styrene derivatives catalyzed by an acidic resin supporting palladium complexes

Pd–TPPTS–OTPPTS (denoted as Pd–P–OP, where TPPTS was the sodium salt of tri(m-sulfophenyl)phosphine and OTPPTS was the oxidized form of TPPTS) complexes supported on acidic resins (denoted as Pd–P–OP/resin) were prepared and employed as versatile heterogeneous catalysts for the hydroesterification of vinyl-aromatics with alcohols. The catalysts were characterized by the methods of FT-IR, XPS, N2 physisorption, XRD, TGA, SEM and 31P NMR. According to the 31P NMR results, there was a weak coordination between OTPPTS and the Pd sites. Consequently, OTPPTS was a weak ligand to the Pd sites and thus dissociated easily, acting as a protective agent of the vacant coordination site of the Pd metal sites, which allowed the substrates more access to the metal sites. In the hydroesterification of styrene, the distribution of the branched and linear esters was remarkably impacted by adding an appropriate amount of OTPPTS and the acidic resin supports. A high yield and excellent selectivity towards the branched ester were obtained when OTPPTS and TPPTS were used in equimolar amounts under optimized reaction conditions. The generality and recyclability of the catalyst for the hydroesterification of vinyl-aromatics were also examined. In addition, the poisoning and hot filtration tests indicated that Pd(0) acted as the active species in a truly heterogeneous way. A Pd–hydride mechanism was proposed for the hydroesterification over the Pd–P–OP/LSI-600 catalyst.

KI Dispersed onto MCM-41 as Catalytic Sites for the Cycloaddition of Cyclic Carbonates from Epoxides and CO2

Supported KI/MCM-41 catalysts were prepared by the incipient wetness impregnation method and characterized by XRD, SEM, TEM, and N2 adsorption–desorption techniques. It was confirmed that KI on MCM-41 are small in size and even in dispersion. KI/MCM-41 catalyst with a 35% loading of KI has given excellent catalytic activity and stability in the synthesis of various carbonates. The catalyst was easily recovered and could be reused at four times without much loss of activity. In addition, the reaction mechanism was discussed on the basis of the experimental results.

Effects of Alkali Halide Salts on Hydrocarboxylation of Styrene Catalyzed by Water-Soluble Palladium Phosphine Complexes

Hydrocarboxylation of styrene catalyzed by water-soluble Pd-TPPTS complexes was investigated. The reaction conditions, including reaction pressure, temperature, time and etc. have a significant influence on the catalytic performance. It was found that the yield of total acids and the selectivity towards 3-phenylpropionic acid were enhanced by adding a suitable amount of alkali metal halide salts. In addition, the reaction mechanism and the role of alkali metal halide salts in the reaction were discussed on the basis of the characterization of 1H NMR and 31P NMR.Graphical Abstract

Quadruply Hydrogen Bonding Modules-Versatile Building Blocks for Polymeric Material Design-Beyond Entanglements

Hydrogen bonding facilitated self-assembly is an appealing strategy for constructing advanced molecular architecture. Arrays of quadruply hydrogen-bonding (QHB) modules are especially appealing due to the reason that it features extremely strong yet reversible and dynamic interactions. This review focus on the design and development of polymeric materials utilizing QHB arrays such as 2-ureido- 4[1H]-pyrimidone (UPy), butylurea of guanosine (UG), deazapterin (DeAP), 2,7-diamido-1,8-naphthyridine (DAN) and 7-deazaguanine urea (DeUG). Investigating QHB interaction at molecular level and evaluate the physical and chemical properties of the resulting material in solution and bulk are discussed. Specific examples highlighted in this review demonstrate how QHB modules are used and incorporated into polymer matrix to yield stimuli-responsive functionalized polymer. It is discussed how QHB modules providing extra interactions which are responsive under mechanical stress. The interactions associated with QHB modules could be effective adhesion promoters and source of energy dissipater and can facilitate development of functional polymers and smart materials such as stimuli-responsive polymers, novel interpenetrating polymers, polymer blends and fiber/particle reinforced polymer nano-composite.