In liquid-liquid dispersion systems, the dynamic change of the interfacial properties between the two immiscible liquids plays an important role in both the emulsification process and emulsion stabilization. In this paper, experimentally measured dynamic interfacial tensions of 1-chlorobutane in the aqueous solutions of various random copolymers of polyvinyl acetate and polyvinyl alcohol (PVAA) are presented. Theoretical analyses on these results suggest that the adsorption of the polymer molecules is controlled neither by the bulk diffusion process nor the activation energy barrier for the adsorption but the conformation of polymer molecules. Based on the concept of critical concentration of condensation for polymer adsorption, as well as the observation that the rate at which the dynamic interfacial tension changes does not correlate to the PVAA’s ability to stabilize a single drop, it is postulated that the main stabilization mechanism for the PVAAs is by steric hindrance, not the Gibbs–Marangoni effect offered by the small molecule surfactants.
Recent development of super-conducting materials at high temperature has got enabled to use a super-conducting magnet of 5–10 Tesla and various new phenomena have been reported. In the present report, convection is considered for air containing oxygen whose magnetic susceptibility is exceptionally large among gases. Air is filled in a cubic enclosure whose one vertical wall is kept at a higher temperature and an opposing wall is cooled at a lower temperature and other four walls are thermally insulated in the presence of a gradient magnetic field produced by a one-turn coil located above the enclosure. A numerical model including the magnetizing force and the gravitational force was developed and numerical computations were carried out for the parameters, Pr = 0.71, Ra = 105–106, γ = 0–10 to represent the strength of magnetic field versus the gravitational potential. For example, at Ra = 105 the average Nusselt number 4.476 at γ = 0 (with no magnetic field) increased to 5.160 at γ = 10. This system was further studied on the effect of inclination with respect to a horizontal axis at the bottom of the hot wall. With an application of a magnetic field, the conduction state heated from above at an inclination angle of 1.5π radians was found to change to a convection state. Flow visualization experiments were further carried out for the same size of a cubic box attached at an outlet of a bore of a super-conducting magnet of 10T with 100 mm diameter. The magnetic field induced the convection for the system heated from above and cooled from below. The computed flow mode agreed well with the experimental one to support the computed results favorably.
As the catalyst for the oxidative decomposition of trichloroethylene (TCE) in air, series of Ru-promoted CrOx/Al2O3 were prepared and studied. The catalysts were characterized using temperature programmed reduction (TPR), temperature programmed desorption of ammonia (NH3-TPD), X-ray diffraction (XRD) and X-ray photoelectron spectroscopy (XPS). The Ru-promoted effects were determined in the respects of the initial catalytic activity, the rate of catalyst deactivation, and the product concentrations of CO and Cl2 under dry or wet air conditions. The presence of a small amount of Ru as much as 0.4 wt% in a CrOx/Al2O3 catalyst turned out to promote the catalytic activity and improve the catalytic reaction performance. The Ru(0.4)Cr(9.6) catalyst was characterized to have better reducibility at lower temperature and higher fraction of more active Cr(VI) species over the catalyst surface. This Ru-promoted catalyst proved to be much less subject to the deactivation during the reaction and to produce less concentration of CO than the Cr(10). Such performance improvements of the Ru(0.4)Cr(9.6) catalyst was thought to attribute to its enhanced oxidation activity originated from the well dispersed coexisting Ru-oxide species, possibly being directly involved in the reaction as active centers activating molecular oxygen, and subsequently, facilitating the supply of activated oxygen to the reaction system.
Methanol was synthesized by the partial oxidation of methane with various oxide catalysts. The reaction was carried out using a pyrex-lined fixed bed reactor at 723–753 K and 20–46 bar, while changing the flow rate and feed gas ratios. The adsorption and desorption characteristics of oxygen were examined with an O2-TPD experiment. Bi-Cs-Mg-Cu-Mo catalyst was found to be the most suitable for methanol synthesis. It appeared that a catalyst that can easily provide lattice oxygen is more suitable for methanol synthesis. The methane conversion and methanol selectivity increased with the temperature. The methane conversion increased with the oxygen concentration, while the methanol selectivity decreased with an increasing oxygen concentration. The feed flow rate did not exhibit any significant effects on methane conversion and methanol selectivity.
Oxygen and ferric ions were used as electron scavengers in the photocatalytic degradation of a pyrimidine derivative (2-isopropyl-6-methyl-4-pyrimidinol, IMP) in order to elucidate the difference in activity with respect to the crystal structure. Commercial catalyst P-25 was used as-purchased (P-25) and as-calcined at 800°C (calcined P-25). The main crystal structure of P-25 was anatase and that of calcined P-25 was rutile. When oxygen was employed as an electron scavenger, IMP was decomposed easily over P-25 whereas very slowly over calcined P-25. On the contrary, calcined P-25 showed better activity than P-25 when using ferric ion as an electron scavenger. It suggests that rutile can also have good photocatalytic activity under a certain condition. The formation rate of ferrous ions, which are converted from ferric ions along with the reaction, decreased over P-25 with reaction time, but it remained constant over calcined P-25. The result was explained in terms of the adsorption ability of ferrous ions on the catalyst. The CO2 formation rate was slower with the addition of ferrous ion in the degradation of IMP, and anatase adsorbed more ferrous ions than rutile. Ceria impregnation on P-25 lowered the conduction band position to be more positive according to electron energy. Ceria-impregnated P-25 lost its photocatalytic activity in the case of using oxygen as an electron scavenger. However, it showed the same activity as P-25 when ferric ions replaced oxygen. The results proposed that the conduction band position is mainly responsible for the different activities of the crystal structures.
Porous particles of oxides of transitional metals, such as copper, nickel, cobalt, iron, manganese, and chromium, were prepared in single and binary mixtures by the freeze-drying process to serve as combustion catalysts. Aqueous metal sulfate solutions of the above metals were utilized as raw material for freeze-drying. Spherical drops of the solutions were instantly frozen in a cooled bath. The frozen particles were dried in a vacuum chamber. These were then calcined into particles of single and double oxides, as well as oxide mixtures. The open porosity within the freeze-dried particles induced by sublimation of ice crystals was retained during calcination and the subsequent firing. Methane/air was combusted in an adiabatic tubular reactor in the presence of the porous oxide particles to determine the particles’ catalytic activity. The feed gas equivalence ratio and residence time were kept constant while methane conversions were measured as a function of gas temperature. The activity of the catalysts was assessed based on the temperature during the surface-kinetics-controlled regime. Among the catalysts examined, the strongest were binary oxides of cobalt and nickel.
Steam reforming of methanol, CH3OH + H2O → 3H2 + CO2, was carried out over Cu/ZnO and various supported group 8–10 metal catalysts. Over Cu/ZnO catalysts prepared by a coprecipitation method, the steam reforming of methanol occurs with high selectivity regardless of composition of the catalyst and structure of the precursor (aurichalcite, malachite, hydrozincite or their mixture). The Cu/ZnO catalysts prepared from the aurichalcite precursor are more active than those prepared from other precursors. By contrast, over supported group 8–10 metal catalysts, such as supported Pd, Pt, Co, Ni, Rh, Ir and Ru catalysts, hydrogen and carbon monoxide are predominantly produced by decomposition of methanol, CH3OH → 2H2 + CO. The selectivity for the steam reforming is lower than those over Cu/ZnO catalysts. However, the selectivity for the steam reforming is markedly improved upon the previous reduction of Pd/ZnO, Pd/Ga2O3, and Pd/In2O3 at higher temperatures. Upon addition of Zn to the supported Pd catalysts, the selectivity for the steam reforming and the rate of hydrogen formation are markedly increased. Over Zn modified Pd/CeO2 catalyst, the selectivity attains to 99.0%, being comparable to Cu/ZnO catalysts. Combined results with temperature programmed reduction, XRD, XPS and AES measurements revealed that PdZn alloy was formed by the previous reduction of Pd/ZnO or Zn modified Pd/CeO2 catalyst. Catalytic functions of Pd are greatly modified upon the formation of PdZn alloys.
We have been studying the reduction of carbonyl compounds by using heterogeneous catalysts in the liquid phase. The reducing reagents were simple primary or secondary alcohols, e.g. 2-propanol. The supported Sn and Zr oxides catalysts were active and selective for the reduction of crotonaldehyde (C4-unsaturated aldehyde: CH3CH=CHCHO) to crotyl alcohol (the corresponding unsaturated alcohol: CH3CH=CHCH2OH) with 2-propanol or 2-butanol as a reducing reagent. The reaction proceeded via hydrogen transfer from alcohol to carbonyl compounds. The reagent, 2-propanol, was converted to only acetone, which could be regenerated by a simple hydrogenation reaction over a conventional metallic catalyst. Silica and MCM-41 supports were superior to TiO2 and Al2O3 for the reaction. This suggests that the surface of porous support should be inert for the hydrogen transfer reaction. The reduction of the Sn catalysts in H2 was necessary for the reaction. The Sn and Zr oxide catalysts were available to the selective reduction of cinnamaldehyde, acrolein, leaf aldehyde, and acetophenone. The corresponding alcohols were selectively formed over the supported Sn and Zr oxide catalysts. The hydrogen transfer reaction will provide various unsaturated alcohols in high selectivity without toxic reducing agents. These results indicate that the hydrogen transfer reaction is one of the Green Sustainable Processes for the production of various alcohols.
Pyrolysis of a mixture of trifluoromethane (CHF3, R23) and tetrafluoroethylene (CF2=CF2, TFE) to produce hexafluoropropylene (CF3CF=CF2, HFP) was investigated by the computer simulation and the pyrolysis. Experiments were carried out at the temperature ranges of 700–1000°C, molar ratios of R23/TFE = 0.1–5.0 and contact times of 0.01–14.00 s. Product distributions for the pyrolysis of R23/TFE were estimated by the computer simulation and were confirmed by pyrolysis experiment. HFP and TFE were mainly produced with a small amount of by-products such as perfluoroisobutylene ((CF3)2C=CF2, PFiB), CF3CCCF3, C2F3H, CF3CHCF2 and CF3CF2CFCF2. It was proposed as a reaction mechanism that HFP might be produced from R23 through the following consecutive reaction: CHF3 → CF2=CF2 → C4F8 → CF3CF=CF2 → (CF3)2C=CF2, and that perfluoroisobutylene, the most harmful by-product, might be predominately formed by a reaction mechanism involving HFP and carbene [:CF2]. It was found that optimum conditions of the pyrolysis of R23/TFE mixtures experimentally determined were the molar ratio of R23/TFE = 1–4, the reaction temperature of 850–900°C and the residence time of 0.5–2 seconds. The reaction temperature could be controlled by carefully utilizing the heat balance between an endothermic pyrolysis of R23 and an exothermic dimerization of TFE.
Water near the critical temperature has been focused as a novel reaction medium. We observed that nylon 6 can be easily depolymerized in sub- or supercritical water to produce ε-caprolactam in our previous work. This indicates that the cyclodehydration reaction proceeds in water near the critical temperature. In this work, we investigated synthesis of 2-aminocaprolactam from L-lysine by cyclodehydration in subcritical water. The reaction was carried out in a batch reactor (5.4 ml in volume) in a temperature range from 573 to 633 K. The reaction time was changed from 5 to 60 min to obtain kinetic data of the reaction. The reaction products were analysed by using LC-MS and HPLC (mobile phase: 0.01 N NaOH solution). As the reaction time increased, the reaction product coloured yellow more deeply. At higher temperature, an yellow or green coloured oil phase was observed. In the products, 2-aminocaprolactam was identified by LC-MS. Lysine was cyclodehydralyzed to 2-aminocaprolactam and then further reacted to by-products in subcritical water. Lysine was completely reacted in 30 min at 633 K. The highest yield of 2-aminocaprolactam was 51% in 20 min at 603 K. For a longer reaction, the yield of 2-aminocaprolactam decreased due to secondary reaction. Subcritical water was found to be an excellent reaction medium for cyclodehydration.
The addition of liquid disperser in the packed bed supposing a biofilter was proposed to reduce the liquid channeling flow. Particles with different diameters and wettabilities were used as the immobilizing particle and the liquid disperser. The two-dimensional distribution of the liquid flow rate was measured by using a liquid collector consisting of 144 cups. The effect of addition of liquid disperser was evaluated by means of the standard deviation of the liquid flow distribution. The liquid channeling flow was much suppressed in the bed added with the liquid disperser than in the bed packed only with immobilizing particles. It is found that the hydrophobic liquid disperser is more suitable for the uniform distribution of the liquid flow.
Preparation and characterization of weather resistant silicone/acrylic resin coatings were investigated. In order to prepare the weather resistant resin coatings, a silicone/acrylic resin (KLD) was first prepared by an addition polymerization reaction of monomers, including n-butyl acrylate, methyl methacrylate, n-butyl methacrylate, and 3-methacryloxypropyl-trimethoxysilane (MPTS). In the preparation of the silicone/acrylic resin, Tg of the acrylic copolymer was fixed at 40°C and the contents of MPTS were varied to be 10, 20, and 30 wt%. The weather resistant silicone/acrylic resin coatings were then prepared by blending the synthesized silicone/acrylic resin and TiO2. The viscosity of the synthesized resin decreased with the content of MPTS, whereas the thermal stability at high temperature increased. The prepared coatings exhibited excellent adhesion to various substrates, and various physical properties of the coatings were satisfactory. The weatherability of the coatings was tested by three ways: outdoor exposure test, Sunshine Weather-Ometer (WOM), and Q-ultraviolet (QUV) accelerated weatherability tester. The gloss retention, yellowness index difference, color difference, and lightness index difference were improved at high MPTS concentration. The coatings containing 30 wt% MPTS have especially good weather resistant properties.
Kinetic model of poly(vinyl butyral) (PVB)/glass ceramic/silver thermal degradation was built using thermogravimetry (TG) data and an artificial neural network (ANN) algorithm. An experimental design method with different material compositions was utilized to demonstrate the effects of the polymer binder burnout with the glass ceramic and Ag. The reaction parameters of PVB thermal oxidative degradation affected by glass ceramic and Ag were obtained by analyzing TG data with a decomposition kinetic equation. From the kinetic analysis, the activation energy (Ea) values of thermal degradation of PVB and the PVB composites are found quite different. In addition, the analysis revealed that PVB thermal degradation is much affected by the existence of the glass ceramic and Ag. The ANN modeling approach was introduced to construct the overall relationships between the different compositions (input) and the estimated kinetic parameters (output). The built ANN model can represent the kinetics of PVB thermal oxidative degradation with respect to the material composition. From this ANN model, the lower Ea appears in the lower composition of PVB and Ag but higher composition of glass ceramic situation.
High impact polystyrene has been a typical thermoplastic to improve the impact strength and toughness of polystyrene. One of the main factors affecting these properties is the particle size and size distribution of the rubber phase. The rubber-phase particle size is related to the prepolymerization time that is determined by the phase inversion between polystyrene and rubber phases. However, the phase inversion in highly viscous oil-in-oil emulsions proceeds with a transitional fashion, not a catastrophic inversion. It has been tried to elucidate this inversion point by using viscosity, conversion and conductivity measurement techniques. They are used to find the point of phase inversion, indicative of the end of phase inversion, but they cannot produce its progression consecutively. In this study, a laser light scattering technique is utilized to characterize the evolution of the rubber particle size distribution depending on reaction time as well as to find the point of phase inversion. The progression of phase inversion during polymerization is monitored by this technique, which in turn is used to establish the proper prepolymerization time. Comparisons, limitations, and applications are dealt with.
Nanoparticle synthesis is part of an emerging field in nanotechnology. Applications take advantage of the high surface area and confinement effects, which lead to nanostructures with properties different from those of conventional materials. The main focus of this work was on nanoparticle synthesis by the use of microemulsions. Change in nanoparticle size due to change in salinity concentration and type of microemulsion was explored. Titanium dioxide was prepared by a precipitation technique in which TiCl4 was solubilized in the microemulsion system of n-heptane/water/NaCl/sodium bis(2-ethylhexyl) sulfosuccinate (AOT) and reacted with NH4OH at a controlled temperature of 30°C. The results showed that different types of microemulsions produced titanium dioxides with different characteristics including different particle sizes. Increasing NaCl concentration strongly influenced the micellar size in both o/w and bicontinuous microemulsions, but it has only a slight effect in w/o microemulsions. Increasing TiCl4 concentration decreased micellar size in all types of microemulsions. The TiO2 obtained from an o/w microemulsion had a surface area and particle size similar to those of the commercial titanium dioxide, P25. For a bicontinuous microemulsion, titanium dioxide product was polydisperse with various particle sizes. Titanium dioxide synthesized in w/o microemulsions was smallest in particle size and highest in specific surface area. The particles were highly crystalline and only anatase phase was obtained in high salt concentrations.
Biodegradable microcapsules entrapping activated carbon impregnated with fenitrotion (MEP), which is used as a pesticide, were prepared by means of the solvent evaporation method in a (solid/oil/water) complex emulsion system. Biodegradable poly-ε-caprolactone (PCL) was used as a wall material. Effects of the preparation conditions, such as the concentrations of PCL and MEP and the weight fraction of activated carbon on the capsule morphology, entrapment efficiency, and release profile of MEP, were investigated. Microcapsules were successfully prepared at relatively large quantities of PCL and activated carbon for MEP. The average diameter of the microcapsules increased with an increase in the concentrations of PCL and MEP and the weight fraction of activated carbon in the organic phase. The entrapment fraction of MEP into the microcapsules was over almost 90% at all preparation conditions and high content of MEP in the microcapsules was achieved. MEP encapsulated in the microcapsules was released to water until the MEP concentration in water reached its saturation concentration. The release rate of MEP decreased with an increase in the PCL concentration and the weight fraction of the activated carbon. Thus, the release profile of MEP could be controlled by adjusting the preparation conditions of the microcapsules.
Interaction forces between solid particles and air bubbles during flotation are of significant academic and practical importance. An atomic force microscope (AFM) probe technique was used to measure the interaction forces between an air bubble and a hydrophobic/hydrophilic spherical particle. In the case of hydrophobic spheres, strong attraction between the surfaces, leading to the rupture of the intervening water film and the attachment of the particle to the air bubble was observed. In the case of hydrophilic spheres, the rupture of the intervening water film and the attachment of the particle to the air bubble did not take place. In each case, however, the repulsive interaction force during approach prior to attachment was dependent on the speed of the bubble (the piezoelectric translator) indicating that the hydrodynamic interaction between the bubble and the particle at short separation distances is significant. The force analysis together with the deformation of the gas–liquid interface during the interaction is described, which gives a more detailed description of the bubble–particle interaction. The outcome of this research increases our understanding of the flotation separation process.
We propose a novel technique for the simultaneous isolation and concentration of a target solute from a multicomponent mixture using a continuous rotating annular chromatograph with double-stage partial recycling of the effluent. In this technique, the target solute is first completely isolated from the multicomponent mixture by a partial recycling method in which the effluents of incomplete separation are recycled to the inlet adjacent to that of the raw feed mixture. Next, the isolated solute is re-recycled to the inlet of the region unused for isolation. In order to concentrate the isolated solute, a second eluent removing the solute from the chromatographic packing to the external liquid phase and making the elution band narrower is supplied to the inlet at a larger angle than that of the re-recycled solute. The technique was applied to the simultaneous isolation and concentration of valine from a ternary mixture of amino acids, glutamic acid, valine and leucine. The numerical calculation based on a mass transport model was used to determine the optimum arrangement of the recycling channels and their corresponding nozzles for isolation and concentration of the target solute. The double-stage partial recycling method allowed the target solute, valine, to be completely isolated and concentrated from the initial concentration of 0.1 mol/m3 to 0.233 mol/m3.
The specific rate of absorption of CO2 into 2-amino-2-methyl-l-propanol (AMP) + diethanolamine (DEA) + water was investigated at 30, 35, and 40°C using a laboratory wetted-wall column. Eight systems of which 1.0 and 1.5 kmol·m–3 AMP mixed with various DEA concentrations (0.1, 0.2, 0.3, and 0.4 kmol·m–3) were studied. The physical properties such as the densities, viscosities, solubilities and diffusivities of N2O in selected amine systems were also measured. The N2O analogy was applied to estimate the solubilities and diffusivities of CO2 in amine systems. Based on the pseudo-first-order for the CO2 absorption, the overall pseudo first-order reaction rate constants were determined from the kinetic measurements. The addition of small amounts of DEA to AMP results in a significant enhancement of CO2 absorption rates. A hybrid reaction rate model, a second-order reaction for CO2/AMP and a zwitterion mechanism for CO2/DEA was used to model the kinetic data. The overall absolute percentage deviation for the calculation of the apparent rate constant kapp is about 7.2% for the kinetics data measured. The model is satisfactory to represent CO2 absorption rates in aqueous AMP + DEA systems.
An applicable use of thermosensitive porous gel for dewatering of organic slurry was investigated. The gel was synthesized with N-isopropylacrylamide (NIPAm) as monomer and N-,N′-methylenebisacrylamide (MBAA) as cross-linker. The porous gel was obtained by simple radical polymerization at higher temperature than the LCST (Lower Critical Solution Temperature) of the N-isopropylacrylamide polymer. At such a high temperature, phase separation occurs with the progress of polymerization, and a porous structure is formed. The porous gel swells and shrinks about 100 times faster than non-porous gel. The porous structure develops with an increasing concentration of the cross-linker. In this research, the plate-like porous gel with a support was prepared to improve the mechanical strength of the porous gel. A stainless steel net was used to support the porous gel. The effect of the support on the swelling properties of the gel was examined, and the dewatering of organic slurry by using such a plate-like porous gel was examined. The plate-like gel with the support swelled anisotropically. The gel with the support was strong enough to use repeatedly for dewatering the organic slurry. The water content of the slurry decreased from 91 to 60%, and the water-absorbing rate increased by increasing the concentration of cross-linker used to prepare the gel. The dewatered cake was easily removed from the plate-like gel surface. The repeated dewatering did not much influence the dewatering rate of the gel within 50 times of recycling.
To remove pollutant Volatile Organic Compounds (VOC), a new type of Pressure Swing Adsorption (PSA) is proposed. VOC is enriched up to a high degree by an enriching reflux policy in which the enriched gas is returned to a high-pressure column as saturated vapor for further adsorption. The excess VOC is then condensed by compression to recover liquid VOC without further treatment. Experiments were carried out for a model system of ethanol vapor and activated carbon. The result was interpreted in terms of the mass exchange efficiency and the effectiveness factor of removal.
Acanthopanax senticosus called Siberian Ginseng has not only a medical benefit for tonic, lumbago, neuralgia and palsy, but also an active operation on metabolism. In this work, the A. senticosus was purchased from Korea Siberian Ginseng Association. The ethanol extract from the powder of the trunk of A. senticosus was partitioned with water and hexane. The resulting solution was purified on a preparative column (3.9 × 300 mm, 15 μm, Lichrospher 100RP-18). The mobile phase composition for isolating acanthoside-D from extract was water/acetonitrile/methanol, 80/14/6%(v/v). The flow rate of mobile phase was 1 ml/min and the UV wavelength was fixed at 210 nm. The fraction containing acanthoside-D was collected and concentrated about one hundred times by a rotary evaporator. From the chromatogram, the impurities were almost eliminated and only pure acanthoside-D was obtained. Finally on a preparative column (3.9 × 300 mm, 15 μm, Lichrospher 100RP-18) with the same mobile phase composition, the allowable maximum injection volume increased to 500 μl.
A low-pressure plasma surface treatment of polymeric powders was carried out in a circulating fluidized bed (CFB) reactor (10 mm-I.D. × 800 mm-high) with CF4 glow discharge. The effects of solid circulation rate, treatment time and radio frequency (rf) power of plasma on fluorination of high-density polyethylene (HDPE) powders have been determined. X-ray photoelectron spectroscopy (XPS) and the contact angle measurements were made to characterize the surfaces of powders. Solid holdup in the CFB plasma reactor mainly governs the stability of plasma glow and the surface property of the powders. Surface of HDPE powders is fluorinated into CHF-CH2, CHF-CHF and CF2 groups. The extent of fluorination increases up to 54% with the treatment time and rf power. The atomic percent of surface fluorine content increases with the composite parameters [(W/FM)t] and [(W/FM)t]/m down to 2,500 GJ·s/kg-gas and 19.8 GJ·s/kg-solid, respectively, thereafter it remains constant.
This paper aims to show a novel yield stress-zeta potential technique for determining the critical zeta potential of α-Al2O3 and ZrO2 dispersions at the flocculated-dispersed state transition and a mean for determining the Hamaker constant of oxides in water via the critical zeta potential. The critical zeta potential is a measure of the particle repulsive potential that exactly counters the van der Waals potential in the flocculated state. At fixed ionic strength the critical zeta potential is indirectly a measure of the strength of the (strongest) van der Waals interaction and hence it can be used to determine the Hamaker constant, an important material property and parameter of the van der Waals equation. Yield stress and zeta potential of dispersions were determined as a function of pH and the subsequent pairing of the yield stress and zeta potential data were made at the same surface chemistry condition. The critical zeta potential was determined from the linear relationship between yield stress and zeta potential square formulated using the DLVO theory. The critical zeta potential was found to be 25 ± 5 mV for the range of ZrO2 dispersions and 35 ± 5 mV for α-Al2O3 dispersions. This means that the van der Waals attractive force interacting between α-Al2O3 particles is twice as strong as that between ZrO2 particles in the flocculated state. Similarly the Hamaker constant of α-Al2O3 in water is twice as large.
This article deals with an experimental observation of the longitudinal vortex pairs being formed intermittently in the stagnant region of an impinging jet from a viewpoint of selective enhancement of jet impingement heat transfer. A two-dimensional submerged water jet issuing from a convergent slot nozzle was made to impinge normally on a solid flat plate. Intermittent generation of the vortex pairs visualized by using a hydrogen bubble technique was recorded by a high-speed video camera. Large-scale turbulent structures were also observed in the stagnant region of an impinging jet with a Laser Doppler Velocimeter. A statistical analysis with conditional sampling was applied to extract each event of vortex-pair generation from the time-series of LDV velocity data as well as the time-series video images of visualized flow patterns. It has been found that the frequency of vortex-pair generation increases with nozzle-to-plate distance up to 6 nozzle widths. This tendency is coincident with that of the enhancement effect of jet impingement heat transfer depending on the jet development distance. It can be conjectured that those longitudinal vortex pairs appear owing to the wave instability of the shear vortex core filaments in the shear layer of the approaching jet.
The flow fluctuation characterization device (FFCD) consists of two small vessels each open at the top and having an orifice at its lower end. The vessels are mounted one above the other, with the lower vessel attached to a load cell or other means for continuously weighing its contents. The material under scrutiny is admitted to the upper vessel, flows into the lower vessel, and exits via the orifice in its lower end. The orifice in the lower vessel is smaller than that in the upper vessel so the flow is choked at this point and the lower, weighed, vessel is kept full of the test material. It has been found experimentally that the load cell output fluctuates with time, and is sensitive to the physical properties of the test material such as particle size and size distribution, the presence of small quantities of fines, and the relative proportions of the species in a mixture. This paper considers cases where the differences in the physical properties in batches of test material are small, and discusses the application of signal-analysis techniques to the time series produced by the FFCD, to establish with confidence that the samples can be considered to be different. Signal-analysis techniques including spectral analysis and attractor reconstruction are critically evaluated.
Reactive distillation is a favourable alternative to conventional series of reaction-separation processes. It can reduce both operating costs as well as capital investments. However, its control is challenging due to its complex dynamics resulting from its integrated functionality of reaction and separation. Linear, e.g. PID, control with fixed parameters has been shown not to be satisfactory to handle its high nonlinearity. It needs to be re-tuned adequately over a wide range of operating conditions. In this work, the application of two adaptive PI control strategies, e.g. non-linear PI (NPI) and model gain-scheduling (MGS), is investigated for an ETBE reactive distillation column. Their control performance to handle the nonlinearity and reduce the unwanted variability is discussed. The simulation results show that the proposed control strategies outperform a standard PI controller in both set-point tracking and disturbance rejection.
Due to the recent diversification of consumer demands for products, batch processes are viewed as a promising process employed in such circumstances. To discover serious conflicts and deadlocks that incur various trouble shooting, in this study, we have proposed a simulation-based approach through viewing the batch processes as a discrete event system. It is realized by converting systematically a sequential function chart to a timed colored Petri net model so that we can carry out appropriate analyses through taking a multi-item production and time dependent behavior into account. In its modeling, we introduced a hierarchical structure for integrating conveniently a family of similar models and for dealing with complexity in real world applications. Through discovery of various conflicts and bottlenecks, we can take proper actions for improvement in operation procedures and equipment requirement in the batch processes. Finally, to confirm effectiveness, we provide a case study associated with a two-step polymer process, and conclude with notification on the special advantages of the proposed approach.
This paper presents a new systematic procedure to help process designers synthesizing a separation process that is economically efficient and environmentally sustainable. The proposed methodology is a hybrid method consisting of algorithmic and heuristic processing of symbolic and numeric data. The heuristic approach, applying experience-based rules and thermodynamic insights for selection of separation operations, is used to reduce the complexity and size of synthesis search space. The algorithmic approach using mathematical modeling is then used to formulate and solve the remaining problem. All environmental impacts are evaluated through all input and output of process and product life cycles. All criteria are simultaneously considered, and the multi-criteria optimization problem, which is formulated using existing computer-aided molecular design and selection tools, and computer-aided process design and analysis techniques, is solved to construct a trade-off set. The constructed trade-off set is then further analyzed to select a promising solution. The proposed methodology is implemented using available software tools. Application of developed methodology is illustrated in a case study. We investigate process for phenol recovery from wastewater. This process is used in phenolic-resin manufacturing. The developed methodology can select solutions that are minimal environmental impacts at a desired economic performance.
The removal of bisphenol A from aqueous solutions was examined using a culture broth of Coprinus cinereus as a source of peroxidase. Bisphenol A was efficiently removed by a polymerization and precipitation method catalyzed by peroxidase. The removal efficiency was optimal between pH 9–10 and at 40°C, and at a molar ratio of H2O2 to bisphenol A of about 2.0. To remove 100 mg/L bisphenol A, 3 U/mL peroxidase was required at pH 10 and 40°C, and 5 U/mL at pH 7 and 25°C. The acute toxicity of the bisphenol A solution, which was estimated using a bioluminescence method, decreased with the peroxidase treatment and became almost zero when the removal efficiency became 100%. Also, the estrogenic activity decreased due to the treatment.
The extraction of dehulled ground palm kernel using supercritical carbon dioxide (SC-CO2) as a solvent at a temperature of 40°C and pressures range from 34.5 to 48.3 MPa was studied. At 48.3 MPa and 40°C the solubility of oil was about 21.1 g/100 g carbon dioxide, however maintaining constant temperature of 40°C the solubility of oil increased with pressure. The fatty acid composition of oil extracted varied with fraction time. The first fraction had 52.2 percent lauric acid content. The lauric acid content decreased to 34.3 percent in the third fraction with an increase to more than 40 percent fatty acid with 16 carbons or more. The breakdown was 0.1 percent palmitic acid (C16), 8.9 percent stearic acid (C18:0), 20 percent oleic acid (C18:1) and 4 percent linoleic acid (C18:2). Blending of palm oil (PO), palm kernel oil (PKO), stearic acid (C18:0) and oleic acid (C18:1) at different ratios were carried out to obtain blends as cocoa butter replacers (CBR) fat. The lauric and myristic acids were reduced to 9.03 and 4.44 percent in the CBE blend, although there are no lauric and a trace of myristic acid in CB. The percentages of other fatty acids in CBE were found to correlate well to the CB except C18:0 which was only 16.15 percent. The slip melting point (SMP) increased with the increase in C18:0. The value of SMP was found to be 36.1°C for the CBE blend whereas for the CB it is 35°C. The iodine value for the CBE blend was found 38.3 where as for CB it is 36. The solid fat content (SFC) of CBE at 20, 35 and 37.5°C was found to be 59.3, 8.5 and 0 percent, respectively. Whereas, the SFC values of CB are 72, 11 and 0 percent, respectively. Although the percent of the C18:0 in the CBE was lower than the commercial CB but it did not affect to the SMP and SFC.
Freezing is a common method of food preservations. Maintenance of physical integrity and quality of food product is always an issue for long-distance transportation. A relatively novel freezing method, cryogenic freezing involves rapid formation of a thin frozen crust on the surface of food material, which can serve as a protective layer to reduce the degree of contamination from surroundings such as salt diffusion from the saline solution used in the subsequent freezing process. Cryogenic freezing also minimizes degradation of food material by avoiding moisture loss, a serious problem usually associated with other conventional freezing methods. The physical integrity of the food product can also be improved. The reduction of total freezing time is the other advantage of this freezing method. In this work, beef was selected as a sample material due to its potential practical application and was examined for the reduction of salt uptake from the saline solution used in freezing and the reduction in the overall freezing period. All experimental parameters were kept constant except for the cryogenic freezing time. The results show a significant improvement in the prevention of salt diffusion and some shortening of the total freezing time, which makes this freezing technology feasible for meat processing.
Synthesis of γ-linolenic acid (GLA) from linoleic acid (LA) is less than 10% in the human body. GLA is changed into di-homo-γ-linolenic acid (DHGLA), a prostaglandin 1 (PGE1) precursor. PGE1 has anti-inflammatory and anti-thrombotic properties. Due to these facts, supplements of GLA in a diet can alleviate the resulting health problems as platelet aggregation, arthritis and spleen constriction/dilation. Borage (Borago officinalis) seed has a high oil content (30% d.w.b.), which is the richest source of γ-linolenic acid (GLA), with 24% GLA. Cold pressing borage oil extraction, does not harm the final product quality, but its yield (about 77%) is lower than 100% yield of traditional oil extraction processes by solvent application. However, according to fibre composition (cellulose, 29% and 5.6% of pectin), it is possible to increase oil extraction yield, using enzymes with pectinases and cellulases activities prior to the pressing stage. In this work, press extraction of borage seed oil was evaluated using an enzymatic pretreatment. Nine commercial enzymes were studied individually and combined. Hydrolysis was performed at pre-selected conditions. Extraction yield was determined measuring the press-cake residual oil by the Soxhlet method. Best results have been obtained by Celluclast-Olivex (1:1) enzyme mixture (cellulase – pectinase), 84% extraction yield with 0.5% d.b. enzyme-substrate ratio. It is concluded that a preliminary enhancement of 8% oil recovery by enzymatic process is relevant due to borage oil’s high commercial value.
The study presented in this paper is focused on processing squid wastes by using sub-critical water extraction and hydrolysis to produce valuable substances. Using a small-scale batch reactor (9.0 cm3), squid entrails were treated with sub- and supercritical water without oxidants. Reaction conditions involved temperatures of 443–673 K, pressures 0.792–30.0 MPa, and reaction times 1–50 minutes. Fat and oil were extracted into sub-critical water very efficiently, and soluble proteins, organic acids, and amino acids were produced in the aqueous phase by a hydrolysis reaction. Even in the short reaction time of 5 min, more than 99% of solid were converted to those products in the temperature, which was higher than 550 K. Results showed a maximum total yield of sixteen amino acids of 0.1031 kg/kg dry entrails at 473 K (5 min), and a maximum total yield of seven organic acids of 0.055 kg/kg dry entrails at 553 K (40 min). Also the oil extracted with hexane included useful fatty acids. Our experimental results indicated that the sub-critical water treatment method is very efficient for converting waste squid entrails to valuable materials as resources for many other industries.
The ultrasonic airlift reactor is proposed for the treatment of wastewater including some soil particles in addition to the refractory materials. The reactor is a bubble column with a draft tube and with an ultrasonic oscillator attached at the bottom of the column. The particles are spherical silica and alumina. The concentration and diameter of particle, the gas velocity and draft tube diameter are changed, and the decomposition conversion is examined. As particle concentration becomes higher, the decomposition conversion decreases. The decrement in decomposition conversion is affected by the particle material. With increasing gas velocity and draft tube diameter, the decomposition conversion increases. The increment in gas holdup can compensate the decrement in decomposition performance with particle addition.
This paper proposes a novel decision making procedure based on multiobjective optimization programming (MOOP) to find the investment priority to reduce plant accidents. The new method rank the accident scenarios in order among many possible accident scenarios in a plant to decide the invest priority as considering safety and cost simultaneously. The method is explained by taking an example, which includes 30 accident scenario data (Kim et al., 2001) consisting of accident consequence, accident frequency, safety activity cost, and non-operating time. In this example, four goals are considered: (1) minimization of total safety activity cost, (2) minimization of total accident consequence, (3) minimization of the number of accident scenarios for unreasonable frequency, and (4) minimization of non-operating time. To analyze this optimization problem in terms of process safety and cost, this study obtained the noninferior solution curve (Pareto curve) by using the Goal programming (GP) methods. We found the ideal compromise solution set based on the Pareto curve. This result assists the business decision maker to select the best compromise in improving process safety as well as reducing investment cost.