A Generalized Correlation for Predicting Saturated Liquid Densities of Mixtures

A generalized correlation for saturated liquid densities of pure compounds, based on the Guggenheim equation, has been extended for applications to mixtures. The method employs a mole-average acentric factor and scaling volume, and a weighted average critical temperature for the mixture. The method was tested on twenty-four binary and two ternary systems comprising hydrocarbons and non-hydrocarbons. Overall average absolute deviation in predicted densities is less than two percent for a total of 1,096 data points.     

Fractional destraction of coal-derived materials

The use of supercritical fluids to fractionate coal-derived distillate and residuum in a manner analogous to conventional fractional distillation is reported. Fractionation based upon volatility is observed when a fluid density gradient is established in the unit to promote reflux.     

Sonocrystallization and crystallization with gassing of adipic acid

Sonocrystallization is widely used to control nucleation and, therewith, improve the product quality. For this purpose, power ultrasound is turned on within the metastable zone during the crystallization process. But the mechanism by which power ultrasound induces nucleation is still unclear. Efforts have been made to identify the mechanism. It is assumed that nucleation is induced due to the bubble surface provided acting itself as nucleation center so that the mechanism seems to be a heterogeneous one. To prove this assumption, gassing has been investigated to induce nucleation during batch cooling crystallization. The gas bubbles are just expanding not collapsing. This study focuses on the investigation of the crystallization behavior of adipic acid during sonocrystallization and, furthermore, during the crystallization with gassing. During sonocrystallization experiments the insonation period, the ultrasonic frequency and the initial supersaturation ratio were varied. The results show that the metastable-zone width can be reduced and the crystal-size distribution, which turns out to be bimodal, can be narrowed the longer the insonation period and the higher the initial supersaturation ratio is. The crystals formed were identified as agglomerates, whereas the agglomeration can be reduced by power ultrasound. The gassing experiments demonstrated that the crystallization behavior of adipic acid can be affected similar to the application of power ultrasound. It can be concluded that gassing is an alternative to power ultrasound.     

Functionalised multi‐walled carbon nanotubes for epoxy nanocomposites with improved performance

BACKGROUND: Carbon nanotubes (CNTs) are fast becoming key components in the production of high‐strength composite materials. Two methods to prepare nanocomposites by covalent bonding between an epoxy matrix and functionalised CNTs that acted as cross‐linkers during polymerisation were investigated. RESULTS: In the standard method, 1 wt% functionalised CNTs was dispersed in epoxy, hardener was added and the composite was cured. In the masterbatch approach, 1 wt% functionalised CNTs was mixed with epoxy in the presence of triethylamine accelerator, then cured. This yielded partially cured epoxy; additional hardener was required to achieve complete curing. Improvements were observed in storage modulus (E′), flexural modulus (E_B), wear resistance and hardness. Thermal stability did not change appreciably for samples prepared by either the standard or masterbatch methods. Variations in the results obtained as a function of preparation method, functionalised CNTs and hardener used are discussed. CONCLUSION: Epoxy nanocomposites having improved mechanical properties were obtained by incorporating functionalised CNTs. Better interaction between the epoxy and CNT was achieved using the masterbatch method; this was attributed to covalent bonding between the CNTs and epoxy. However, optimisation of the CNTs, accelerator and hardener used in composite preparation is required to obtain improved physical properties. Copyright © 2009 Society of Chemical Industry     

Estimation of pressure effect on binary azeotropic compositions

An explicit method for expressing the temperature dependence of liquid activity coefficients is applied to the estimation of the pressure effect on binary azeotropic compositions. The method is based on the assumption that at fixed composition the partial molal heat of mixing is a linear function of temperature. As a consequence the logarithm of the activity coefficient is expressed in the form (a+b/T+c log T). The estimated results for three systems tested agree well with the reported experimental values, the agreement being better than that obtained with the available methods in the literature.     

AN ASSESSMENT OF EXPERIMENTAL TECHNIQUES FOR THE MEASUREMENT OF BUBBLE SIZE IN A BUBBLE SLURRY REACTOR AS APPLIED TO INDIRECT COAL LIQUEFACTION

The proper design and control of an indirect coal liquefaction process plant require an accurate knowledge of bubble sizes and size distribution. Of particular importance regarding proper design is the understanding of the complicated dependence of bubble dynamics on bubble column geometry, and of the nature of the solid-liquid phases. The nature of the products and their relative proportions, on the other hand, are seriously influenced by the bubbling characteristics of the reactor because the mass transfer behavior and mixing are dependent on the bubble size and velocity distributions. This report reviews experimental techniques that have been employed to measure bubble sizes in multiphase reactors. The methods, which fall in three different categories, namely, the photographic method, the optical probe, and the electrical conductivity (resistivity) probe, are described in a historical sequence; and in each case, their unique features and design details are discussed. A general methodology of data analysis in each category is given, together with a state-of-the-art technology assessment and, finally, relative merits and demerits of the methods.     

Additive excess free energy models for predicting gas solubilities in mixed solvents

New data are reported for the solubility of hydrogen in the solvent binaries: acetone-isopropanol, acetone-cyclohexane, and acetone benzene at 25°C and one atmosphere pressure. Models for predicting mixed solvent Henry's law constants which utilize solvent vapor-liquid equilibrium data are reviewed, and a new model based on the van Laar equation is proposed. The new data and selected data from the literature are used to evaluate the models. For the six systems tested, the proposed model gives the best results, with the assumption of ideality (Krischevsky equation) being nearly as good.     

A blue light emitting perylene derivative with improved solubility and aggregation control: Synthesis,characterisation and optical limiting properties

We report the synthesis and characterisation of 3,4,9,10-tetra-(12-alkoxycarbonyl)-perylene, a blue emitting organic material with controlled aggregation and improved solubility. The dye has a UV–Vis maximum absorption peak at 472 nm. Room temperature photoluminescence reveal a blue emission peak at 489 nm. Thermo gravimetric analysis (TGA) performed in air show the product to be thermally stable up to 300 °C. Dynamic scanning calorimetry (DSC) did not show a liquid crystalline phase normally present in 3,4,9,10-tetra-(n-alkoxycarbonyl)-perylenes for 2 ? n ? 9 where n is the number of carbon atoms in the alkyl chain. Atomic force microscopy (AFM) and scanning electron microscopy (SEM) were employed for aggregation studies of the dye showing that molecular stacking is not favoured. The Tauc relation applied to the UV–Vis absorbance cut-off wavelength at 500 nm was used to evaluate the optical band gap of the material as 3.81 eV and an exciton binding energy of 1.2 eV. Open-aperture Z-scan proved the molecule to be nonlinear optically active with an optical limiting extinction coefficient of 3.0 × 10^?10 cm W^?1. Experimental evidence shows that the optical limiting ability is attributed to nonlinear scattering.