The liquid–liquid phase equilibria for the hexane+polydisperse polyethylene (PE) systems were measured at 473 K and at feed PE weight fractions ranging from 0.075 to 0.20. An apparatus was developed for the measurement, which consisted of a variable-volume optical cell and two sampling tubes for correcting both the top (hexane-rich) and bottom (PE-rich) phases. The PE weight fraction of the hexane-rich phase decreased with decreases in the feed weight fraction of PE and the phase equilibrium pressure. On the other hand, that of the PE-rich phase increased as the feed PE weight fraction and pressure decreased. Furthermore, the experimental data were compared with the predicted results obtained using the Sanchez–Lacombe equation of state. The predicted results approximately reproduced the experimental results for the PE weight fractions of the hexane-rich phase. Although some deviations were found in the experimental results of the PE-rich phase, the predicted phase equilibrium lines qualitatively reproduced the experimental results, which showed that the PE weight fraction increased with decreases in the feed PE weight fraction and pressure. Moreover, both the experimental and the predicted results also indicated that the influences of the feed PE weight fraction on the weight average molecular weight and on the polydispersity index of PE in the PE-rich phase were larger than those in the hexane-rich phase at low pressure.
Plugging leaks and controlling winds are the most effective approaches for preventing coal/oxygen-compounded reactions and spontaneous combustion of coal. Inorganic solidified foam (ISF) is an effective material for preventing spontaneous coal combustion, and the mixer used in formulating ISF is important for improving the homogeneity and expansion ratio. In order to prepare an ISF with a good performance, a novel mixer was designed for mixing aqueous foam with composite slurry. The mixer had a hollow spiral structure that reduced the breakdown of the aqueous foam and increased the foam slurry contact area. We analyzed the mixing mechanism and the process by which the composite slurry particles combined with the aqueous foam to form ISF. We found that there was an optimal relationship between the rotational speed of the mixer, homogeneity, and expansion ratio. The performance of the mixer was investigated experimentally using various rotational speeds and aqueous foam flow ratios. Experimental performance testing and evaluation showed that for different aqueous foam flow ratios, and for the rotational speeds of 100 rpm or 150 rpm, the relative standard deviation of the pore area was minimal and exhibited good homogeneity. Simultaneously, the value of the expansion ratio reached a maximum, and the breakage of aqueous foam was minimal. The results of this experiment provide the basis for coal mine field applications for ISF.
In order to investigate the flow behavior of pressure letdown in dense-phase pneumatic conveying at high pressure, experiments using pulverized coal were carried out at a conveying facility with pressures up to 3.0 MPa. The effects of the pressure letdown structure, operation parameter and particle size on the flow characteristics of the pressure letdown were studied. Empirical correlation of pressure drop through the pressure letdown was derived using the Barth additional theory and experimental results. The results show that the solid loading ratio and gas velocity have a stronger effect on the pressure drop through the pressure letdown. The flow characteristics of gas–solid two-phase flow across the different sections of the pressure letdown were characterized and examined. Pressure drops rise with increasing particle size or pipe diameter ratio at similar operating parameters. The empirical model of the pressure drop through the pressure letdown was derived and the predicted values agree well with experimental results, with relative deviations less than ±10%. The flow characteristics of the pressure letdown offer the theoretical support for design, control and operation of dense-phase pneumatic conveying at high pressure.
The characteristics of microbubble generation were investigated experimentally at pressures up to 6 MPa under methane–water bubbly flows driven by a submersed centrifugal pump in a closed flow loop. The focused beam reflectance measurement was utilized for in-situ microbubble sizing at the pump downstream. The influence of system pressure was evaluated for turbulent shear rates between 4.5×103 and 23×103 s−1 at 298 K and a void fraction of 0.016. The microbubble number density was found to increase significantly with increasing pressure; whereas, the median bubble size fell within the magnitude of the Kolmogoroff microscale. The transient size distribution functions indicated that turbulent shear coalescence plays a significant role at high shear rate above 104 s−1. It was also suggested that the jetting pump flow at higher pressures could enhance microbubble stability.
In this study, the correlation between surface vanadium species and reactive lattice oxygen in the selective catalytic reduction of NOx by NH3 was investigated. The properties of the V/TiO2 catalysts were investigated using physicochemical measurements, including Brunauer–Emmett–Teller surface area, temperature programmed reduction with hydrogen, Raman spectroscopy, and UV–visible diffuse reflectance spectroscopy. V/TiO2 catalysts were prepared using the wet impregnation method by supporting 2 wt% vanadium on TiO2 thermally treated at various calcination temperatures. Lattice oxygen participating in the reaction was found to be most abundant in 2V/TiO2-600, prepared from TiO2 calcined at 600°C. An increase in reactive lattice oxygen, resulting from an increase in the proportion of polymeric distorted tetrahedral structure existing on the surface of the catalyst, improved the catalyst efficiency. A polymeric distorted tetrahedral structure is referred to as a bridged bond (V–O–V). In addition, greater SO2 resistance was related to a higher polymeric VOx ratio. Thus, the bridged bond (V–O–V) provides the lattice oxygen participating in the reaction.
The present study investigates a solid acid catalyst synthesized using single walled-carbon nanohorns dispersed with Fe nanoparticles. It was found that this catalyst exhibited a high acid site concentration of 3.6 mmol/g, which was about twice that of the largest record of nanotube-based solid acid catalyst. A two-step process was employed in the catalyst preparation, comprising an acid impregnation step using sulfuric acid, followed by a calcination step in air was performed. This work focused on investigating the influence of the temperature in the calcination step, which could affect the morphology, the activity, and the magnetic property of the catalyst. X-Ray diffraction analysis suggested that the catalysts prepared here with the high acid site concentration included nanoparticles of Fe and Fe3O4 because the Fe nanoparticles in the catalyst could be partially oxidized in the calcination step, while the carbonaceous part of the catalyst became porous to increase the specific surface area. Although this oxidation caused an obvious reduction in the magnetic susceptibility of the catalyst, the catalyst was able to be magnetically recovered. It was found that the above mentioned high acid site concentration could be achieved by employing the optimum calcination temperature (400°C).
A method to prepare monodisperse solid fat microspheres using microfluidic techniques is demonstrated. Monodisperse molten fat droplets are generated in a capillary microfluidic device heated above the melting point of the fat, and subsequently solidified by cooling. This process offers highly monodisperse solid fat microspheres with a coefficient of variation of less than 1.5% without the addition of an emulsifier. The monodisperse solid fat microspheres are potentially useful as food materials and microcapsules in delivery systems.
Recently, a peptide mixture (Pep) obtained as a casein hydrolysate was found to be effective for enhancing the water solubility or water dispersibility for poorly water-soluble drugs. In the present study, complexation of Pep with ionic and nonionic drugs indomethacin (Indo), ibuprofen (Ibu), and prednisolone (Pre) was studied. The water solubility of complexes containing Indo and Ibu, both of which have a dissociable carboxylic group, increased with increasing pH. In contrast, the water solubility of a complex containing Pre, which does not contain dissociable groups, was almost independent of pH. As all three complexes were permeable through an ultrafiltration membrane with a molecular-weight cutoff 10,000 gmol−1, the complexes were present not as colloidal materials but relatively small species in aqueous media. Moreover, Indo, Ibu, and Pre were complexed with twelve peptide fractions, which were derived from Pep by combining ammonium sulfate precipitation with ultrafiltration. Water solubility of the drugs increased with all Pep-derived fractions, suggesting that various peptides interact with the drugs.
Production of hydrogen, being an environmentally friendly energy source, has gained a lot of attention in recent years. The scope of the present research is to investigate the production of hydrogen with the help of methane’s catalytic decomposition. The iron-based catalysts, calcined at different temperatures (300–800°C), supported over different kinds of support materials such as magnesia and titania, are examined by catalytic decomposition of methane for the production of hydrogen. The catalysts were prepared by incorporating different methods, including impregnation and co-precipitation. The catalytic activity results revealed that, for both impregnated and co-precipitated catalysts, the calcination temperature of 500°C performed relatively better. For co-precipitated catalysts, Fe–Mg-CP catalyst gives higher CH4 conversion and H2 yield as compared to Fe–Mg-Imp catalyst. Conversely, all titanium supported catalysts exhibited less activity as well as deactivation. Among magnesia supported catalysts, the Fe–Mg-CP catalyst presented the best activity (about 65% conversion) for the time period of 3 h on the stream. The study revealed the inappropriateness of TiO2 support for Fe catalysts in the catalytic methane decomposition. The formation of carbon nanotubes over both impregnated and co-precipitated catalysts was evidenced from morphological analysis. The fresh and spent catalysts were characterized using different techniques such as BET, H2-TPR, O2-TPO, XRD, TGA, FESEM and TEM.
The dimensionless extinction constants, Ke, of soot produced from a small laminar flame burning ultra low sulfur diesel (ULSD) and soy methyl ester (B100) biodiesel fuel were measured in the visible (632.8 nm) and near infrared (1,064 nm) wavelengths. Experiments were performed at atmospheric pressure using a transmission cell reciprocal nephelometer (TCRN) in which simultaneous gravimetric sampling and light extinction techniques (GSLE) were employed. For the diesel soot, the average value of the Ke at 632.8 nm was 11.1 whereas that of the Ke for biodiesel was 11.8 at the same wavelength. As the wavelength increased up to 1,064 nm, the average Ke for diesel and biodiesel soot was found to reduce to 10.5 and 9.4, respectively. In an effort to quantitatively explain the variations in Ke (influenced by fuel type and wavelength), analysis of the influence of scattering, beam shielding, and nanostructure was performed through the measurements of soot physical and fractal properties and soot nanostructure properties. It was found that diesel soot was more closely aligned to graphitic properties, compared to biodiesel soot influencing the absorption component of dimensionless light extinction constant. Results also revealed that the influence of scattering was not a negligible component of extinction at 632.8 nm. However the influence of scattering decreases with wavelength from 632.8 to 1,064 nm, lowering the measured Ke values. The beam shield effects were observed to be an important mechanism that reduces the Ke for diesel soot at 632.8 nm and become weaker as the wavelength increases to 1,064 nm.