A preparation method for a high-porosity organic chlorinated polymer as an alternative to poly(vinyl chloride) (PVC) is examined to investigate the possibility of PVC substituted evaluation with the use of 2,3-dichloro-1,3-butadiene (DC) as an alternative to vinyl chloride monomer (VCM). The influence of mixing conditions on the properties of a powder composed of DC polymer was then investigated. As a result, an alternative evaluation of the PVC powder properties without the use of VCM was acquired by the addition of n-heptane. It was found that both the mean particle size and the quantity of plasticizer absorption are exponentially correlated with the power consumption rate per unit volume.
Power consumption in unbaffled and baffled agitated vessels with propeller and pfaudler type impellers is measured over a wide range of Reynolds numbers from laminar to turbulent flow regions. The power correlation for the propeller and pfaudler type impellers is derived from modification of the previously proposed power correlation for a paddle impeller. The calculated correlation values agree well with experimental ones, and the same correlation can be applied to both propeller and pfaudler type impellers.
In this research work, the effect of pulse intensity, flow rate of disperse and continuous phases on volumetric mass transfer coefficients of two phases along the height of pulsed sieve-plate column have been studied. Two chemical systems, toluene–acetone–water and normal butyl acetate-acetone–water, were used. The deviation between experimental and predicted values from equations, which have been proposed by other researchers is considerable. A correlation for predicting enhancement factor of diffusion coefficient of mass transfer coefficients has been achieved and the comparison between experimental data and predicted values are in very good agreement. Finally, the proposed equation is used for calculating height of the column.
Crystallization of uracil (URA) induced by the imprinting effect is observed when a poly(acrylonitrile-co-methacrylic acid) membrane has been prepared in supercritical CO2 using phase-inversion imprinting technology. The URA-imprinted membrane forms flower-like crystals of URA on the surface, but neither a non-imprinted membrane nor the membrane left in the URA aqueous solution shows crystal formation. Effects of organic solvents on the URA-imprinted membrane are examined for the membrane was prepared in supercritical CO2 fluid. Evidence shows that supercritical CO2 media is important for the formation of URA crystals on the imprinted membrane.
The reaction kinetics of the absorption of CO2 into mixed aqueous solutions of piperazine (PZ) and triethanolamine (TEA) are investigated using the wetted wall column at temperatures of 303.2 to 313.2 K. The physical properties such as density and viscosity of the aqueous alkanolamine solutions, and the solubility and diffusivity of the nitrous oxide in aqueous alkanolamine solutions are also measured. The N2O analogy is applied to estimate the solubilities and diffusivities of CO2 in aqueous amine systems. Based on the pseudo-first-order for CO2 absorption, the overall pseudo first-order reaction rate constants were determined from the kinetics measurements. For CO2 absorption into mixed aqueous solutions of PZ and TEA, it is found that the addition of small amounts of PZ to aqueous TEA solutions has a significant effect on the enhancement of the CO2 absorption rate. For the CO2 absorption rate model, a second-order reaction rate model is applied for both reactions of CO2 with PZ and TEA. The overall absolute percentage deviation for the calculation of the apparent rate constant kapp was 4.6% for the kinetics data measured. The model is satisfactory in representing the CO2 absorption into mixed aqueous solutions of PZ and TEA.
The dependence of the oxygen reduction reaction (ORR) activity of Pt/C catalysts used in actual polymer electrolyte fuel cell membrane electrode assemblies (PEFC MEAs) on cell temperature, O2 partial pressure and catalyst loading has been investigated. Based on physical chemistry and electrochemistry points of view, the charge transfer coefficient (α) was demonstrated to vary with potential over a narrow range of 0.5–0.6. The double Tafel slope occurring at potentials above 0.8 V vs. RHE was considered to be caused by the effect of adsorption or reaction of oxygen-containing species sourced by water. As a result, the α was assumed constant at 0.5 irrespective of the potential, and used in the estimation of the ORR activity [A/cm2-Pt]. The ORR activity was observed to increase linearly with increasing temperature. It was also found to be dependent on O2 partial pressure (considered as O2 concentration) until it reached a plateau at an O2 concentration of 40%, and then remained almost constant. This finding implies that in gas-phase PEFC MEAs, adsorption of O2 as a reactant can influence and govern the electrochemical reaction. In addition, the ORR activity is demonstrated to be independent of the Pt/C ratio of the catalyst not only for Pt plate electrodes in liquid-phase systems, but also for MEA electrodes in the gas-phase system of actual single-cell PEFCs. The ORR activity was found to be almost constant at 2.6 × 10–6 A/cm2-Pt at 60°C for Pt/C ratios from 19.3 to 55.8 wt%.
Methods for preparing monodispersed, multilayered silica-Y:Eu-silica core-shell particles and for fabricating their colloidal photonic crystals are proposed. Silica-Y:Eu core-shell particles with a size of 360 nm were synthesized with a homogeneous precipitation method at 80°C in a 50/50 (v/v) water/propanol solution at 0.0009 mol/dm3 Y(NO3)3, 0.0001 mol/dm3 Eu(NO3)3, 0.5 mol/dm3 urea, 1 g/dm3 polyvinylpyrrolidone (PVP) and 0.01 vol% suspension of silica particles with an average size of 330 nm. Succeeding silica-coating of the silica-Y:Eu core-shell particles was performed in ethanol at 10 mmol/dm3 tetraethylorthosilicate, 11 mol/dm3 H2O, 0.5 mol/dm3 ammonia, 5 mmol/dm3 acetic acid, 1 g/dm3 PVP and 0.001 vol% suspension of silica:Eu core-shell particles. Consequently, multilayered silica-Y:Eu-silica core-shell particles with an average size of 460 nm and a coefficient of variation as low as 3.0% could be obtained. Colloidal crystals composed of these particles exhibited both reflection based on Bragg diffraction and luminescence of Y:Eu.
Our work focuses on developing nickel loaded brown coal char as a new catalyst to decompose tar and to enhance quality of product gas delivered from woody biomass pyrolysis at relatively low temperatures of 823 K and 923 K. It is carried out in a two-stage fixed-bed reactor and a lab scale fluidized bed gasifier (FBG) under various conditions. Inside of gasifier is constructed by two beds, the primary one is a fluidized bed with sand, and the second one is a catalyst bed. The catalyst bed is used to evaluate and to compare catalytic activity between the new catalyst and a conventional Ni/Al2O3 catalyst. The new catalyst is prepared by ion exchange method, dried at 380 K in nitrogen for 24 h, and is then calcined at 923 K in nitrogen for 90 min. The temperature as a function of gas yield and the effect of catalysts on gas yield in presence and absence of steam are investigated in this study. The new catalyst has shown high catalytic activity and stable activity and given the high quality of product gas in presence of steam.
Experimental tests of polycyclic aromatic hydrocarbon (PAH) emission characteristics from co-firing of petrochemical sludge with coal were conducted in a pilot-scale circulating fluidized bed (CFB) incinerator with the thermal input of 0.2 MW. Results showed that when the mass mixing ratio increases from 10 to 40%, PAH, especially lower molecular weight (LMW) PAH, emission increases substantially. As combustion temperature or excess air coefficient increases, PAH emission decreases at first and then increases. There is an optimum combustion temperature and excess air coefficient for inhibiting PAHs formation. PAH emission declines significantly when the secondary air fraction is increased from 20 to 50%. The staged combustion technique of circulating fluidized beds may have the advantage of inhibiting the formation of PAHs. Some optimized operation parameters are recommended for incineration of petrochemical sludge with coal in circulating fluidized bed incinerator.