Esterification of acetic acid with n-Butanol using vanadium oxides supported on γ-alumina

Esterification of acetic acid with n-Butanol has been studied in a heterogeneous reaction system using two γ-alumina-supported vanadium oxide catalysts with different V loadings, which were prepared by the impregnation of a precipitated alumina. The alumina support and the supported catalysts were characterized using X-ray diffraction, N₂ adsorption, EDX analysis and NH₃-TPD techniques. The effects of the reaction time, of the molar ratio of the reactants, of the speed of agitation and of the mass fraction of the catalyst on the catalytic properties were studied. In the presence of the supported catalyst containing 10 wt % V₂O₅ (10V-Al₂O₃ sample) the conversion reached 87.7% after 210 min of reaction at 100 °C with an n-Butanol-to-acetic acid mole ratio equal to one. The conversion as well as the total acidity measured by TPD of NH₃ increased in the following order: Al₂O₃ < 5V-Al₂O₃ (5 wt % V₂O₅/Al₂O₃) < 10V-Al₂O₃. In all cases the reaction was completely selective to n-butyl acetate. Nevertheless, a loss in catalytic activity after three reaction cycles with 10 V₂O₅–Al₂O₃ catalyst was observed.     

Hierarchical assembly of a homochiral triple concentric helical system in a novel 3D supramolecular metal-organic framework: synthesis, crystal structure, and SHG properties

The hierarchical assembly of a homochiral triple concentric helical system in a novel 3D metal-organic framework with SHG activity has been observed. The result also provides a better understanding of host-guest chemistry and the process of water transport in biological systems.     

Two inclusion compounds of guanylthiourea and 1,3,5-thiadiazole-5-amido-2-carbamate

In the crystal structure of [(n-C₄H₉)₄N]⁺·[NH₂(C₂N₂S)NHCOO^?]·NH₂CSNC(NH₂)₂ (1), guanylthiourea molecules and 1,3,5-thiadiazole-5-amido-2-carbamate ions are joined together by intermolecular N–H…O, N–H…N, and weak N–H…S hydrogen bonds to generate stacked host layers corresponding to the (110) family of planes, between which the tetra-n-butylammonium guest cations are orderly arranged in a sandwich-like manner. In the crystal structure of [(n-C₃H₇)₄N]⁺·[NH₂(C₂N₂S)NHCOO^?]·NH₂CSNC(NH₂)₂·H₂O (2), the tetrapropyl ammonium cations are stacked within channels each composed of hydrogen bonded ribbons of guanylthiourea molecules, 1,3,5-thiadiazole-5-amido-2-carbamate ions and water molecules.     

Silver-Ethynide Clusters with Oxovanadate Components

Variation of the reaction conditions with AgC??CR (R?=?Ph, ^t Bu), ^t BuPO₃H₂, (Et₄N)VO₃ and AgNO₃ as starting materials afforded three isostructural globular neutral silver(I)-ethynide clusters incorporating the [( ^t BuPO₃)₄V₄O₈]^4? unit as an integral shell component, namely {(NO₃)₂@Ag₁₆(C??CPh)₄[( ^t BuPO₃)₄V₄O₈]₂(DEF)₆(NO₃)₂}, {(NO₃)₂@Ag₁₆(C??C ^t Bu)₄[( ^t BuPO₃)₄V₄O₈]₂(DMF)₆(NO₃)₂}·DMF·2H₂O and {(NO₃)₂@Ag₁₆(C??C ^t Bu)₄[( ^t BuPO₃)₄V₄O₈]₂(DMF)₆(NO₃)₂}·{(NO₃)₂@Ag₁₆(C??C ^t Bu)₄[( ^t BuPO₃)₄V₄O₈]₂(DMF)₄(py)₂(NO₃)₂}·DMF·5H₂O, in which the central cavity of each Ag₁₆ cluster is occupied by two nitrate ions that function as a template. Furthermore, from the reaction of AgC??C ^t Bu with (NH₄)₄[V₂O₄(d,l-citrate)₂]·4H₂O, we isolated a new high-nuclearity silver(I)-ethynide cluster [(VO₄)₂@Ag₃₄(C??C ^t Bu)₂₂(NO₃)₆]·8H₂O that encapsulates a pair of templating orthovanadate ions.     

Developing a Hong Kong based speed correction factor by CPX method

A systematic procedure for developing speed correction factor to adjust measured tyre/road noise is proposed in this paper. The draft ISO/CD 11819-2 on the Close-Proximity method to measure tyre/road noise stipulates that speed correction is needed to convert the tyre/road noise level at the sampling speeds to that at the reference speeds. However, the ISO standard does not mention the exact methodology for developing the speed correction factor development, although it recommends local authorities to develop their own. In this study, the tyre/road noise and speed data over 59 runs on a high speed porous asphalt surface is recorded by our CPX trailer in Hong Kong. The instantaneous noise and speed data are then analysed using this proposed procedure and the set of speed correction factor developed is found to be more stable and repeatable.     

Generation of singlet oxygen with the use of optically excited fullerenes and fullerene-like nanoparticles

Experimental results and a kinetic model of generation of singlet oxygen during the interaction of oxygen molecules with optically pumped (lamp or laser radiation) fullerenes or fullerene-like nanoclusters in solutions, suspensions, and the form of various solid-phase membranes (surfaces) are presented. The experimental data on the photoluminescence of singlet oxygen in solutions of fullerenes are compared with the results of numerical simulation on the basis of the kinetic model with specified constants of photochemical processes. On the basis of the experimental results, it is shown that evaporation of a solution caused by pumping radiation yields long-lived gas-phase singlet oxygen. Release of gas-phase singlet oxygen from solid-phase fullerene-containing membranes (surfaces) is also demonstrated; however, this process is hindered by adsorption of singlet oxygen on the membrane surface. The prospects for creation of a singlet-oxygen generator on the basis of photoexcited fullerene molecules and fullerene-like nanoclusters are discussed.     

Evidence for two-step disordering of the Au(110)−:1 × 2 reconstructed surface

We present the results of a synchrotron X-ray scattering study of the thermal disordering of the Au(110)−1 × 2 reconstructed surface. Observing the temperature dependence of the in-plane superlattice and integral-order surface peaks, as well as the (ll0) specular reflectivity, we find that at T_c = 735 K the 1 × 2 surface undergoes a reversible deconstruction transition characterized by a proliferation of compact antiphase defects with no measurable change in the density of surface steps. This transition is described by critical exponents close to those characterizing a two-dimensional Ising transition. We also find that by 784 K there has been a significant increase in the density of surface steps of the type associated with surface roughening. This suggests that the Au(110) surface disorders in a two-step process, deconstruction followed by roughening, with a difference in the two transition temperatures of less than 50 K.     

Structural Effect on Eu （fod）3－Catalyzed Rearrangement of Allylic Esters

A detail study on the Eu(fod)₃‐catalyzed rearrangement of allylic esters was described. A significant effect of the substituents at the allylic backbone was observed. The migrating tendency of the alkoxyacetates was established in the order of p‐CF₃C₆H₄CH₂OCH₂CO₂ > MeOCH₂CO₂ > PhCH₂OCH₂CO2 > p‐MeOC₆H₄CH₂OCH₂CO₂.