Absorption of NO in Aqueous NaClO2/Na2CO3 Solutions

The absorption rates of NO into aqueous solutions of NaClO₂ blended with Na₂CO₃ were investigated in a stirred reactor. The experimental results showed that the reaction rate could be expressed as . An equation for a second‐order reaction rate constant between NO and NaClO₂, k_mn = 5.79 · 10¹⁵ exp(–5557.26/T), was obtained. The addition of Na₂CO₃ into the solution of NaClO₂ decreased the reaction rate constant. The optimal absorption conditions involved a NO concentration of 540 ppm, NaClO₂ concentration of 50 mol m^–3, Na₂CO₃ concentration of 10 mol m^–3, temperature of 333 K and O₂ concentration of 4 %, which were determined by an orthogonal experiment. Under these optimal conditions, it was possible for the absorption rate to reach up to 1.9271 · 10^–5 mol/(s m²).     

The effect of temperature on limiting current density and mass transfer in electrodialysis

This study focuses on a high-temperature operation in electrodialysis of salt solutions and studies the effect of temperature on limiting current density and mass transfer. Experiments were conducted under various conditions of temperature (T), varying from 15 to 90°C; of dialysate concentration (C_d), varying from 5 × 10^?3 to 3 × 10^?2M ; and of dialysate velocity (u_d), varying from 0.206 to 2.44 cm s^?1. A least squares fitting of the experimental data on limiting current density (I_lim) yields an Arrhenius equation as follows: The molar flux N? (mol cm^?2 s^?1), initial concentration (C₀; M ) and temperature (T; °C) were found to have the following relationship: N?/C₀ is slightly increased with increasing temperature ranging from 25 to 70°C.     

Predicting the compressive properties of rigid urethane foam

The classic equation¹ in use throughout the urethane industry to predict the compressive properties of rigid foams is ((1)) The value of K and a need to be determined experimentally for each foam system at a given temperature. By evaluating the compressive properties of 14 different rigid urethane foams, a was defined as 1.75 for all materials at all test temperatures. General equations for predicting the foam's compressive properties over a temperature range of ?65° to 325°F (?54° to 204°C) were then developed. These general equations appear to be reasonably accurate in predicting the compressive properties of any rigid urethane at any temperature up to the foam's softening point. The equations are of the form shown above with K being a function of temperature only. Finally, the K term was defined as a function of temperature. The equations developed for predicting the compressive strength and modulus of the rigid urethane foams are: ((2)) for T equal to or greater than 77°F (25°C), and ((3)) for T equal to or greater than ?65°F (?54°C), where the compressive strength and modulus are in pounds per square inch and density is pounds per cubic foot. These equations are valid up to the softening point of the foam.     

Permeation of organic vapors through polymer in the condensation region

Permeability coefficients have been measured for normal butane, isobutane, isobutylene, and butene-1 in Zendel Copolymer-I at temperatures between 30° and 70°C and at penetrant pressures p₁ up to 5.5 atm. The permeability coefficients of these organic vapors show behavior analogous to that observed for C₃ and C₂ hydrocarbons as detailed in our earlier work; i.e., near the condensation point of the penetrant, P increases as the temperature is decreased. Isothermal plots of log P versus p₁ in that region are generally linear and can be represented by empirical relations of the form where P₀ is a constant. The slope a is a function of temperature: where a₀ is a constant and b has the same value for the four hydrocarbons investigated.     

Kinetics of carbon dioxide absorption in aqueous solutions of diisopropanolamine

A bubble column absorber was used to investigate kinetics of the reaction between carbon dioxide and aqueous solutions of diisopropanolamine (DIPA), by means of gas absorption experiments. These were conducted in the temperature range of 20 to 40°C, with DIPA concentrations from 5 to 500 mol/m³, and CO₂ partial pressures between 5 and 101 kPa. A model based on the Danckwerts' surface reneval theory was used to analyze the experimental results and to determine the rate constant. The obtained data support the assumption of a second-order overall reaction, with the rate constants being well correlated by the Arrhenius equation:      

Kinetics of ion exchange in monodisperse resin

Ion-exchange kinetics within a conventional strong base resin, Dowexl-8X®, and a resin with uniform particle size, Dowex® Monosphere® Tough Gel® TG550A®, were investigated using neutron activation analysis and radio-tracer techniques. The kinetics of ion exchange were measured in a batch and in a “shallow-bed” flow system. The experimental data were compared with the results of model computations. The diffusivities of several anions within TG550A and Dowexl-8X were deduced. It was found that at 25°C Br^-, Cl^-, OH^-, and Na⁺ diffuse within TG550A with the diffusion coefficients = 6.0 × 10^-7 cm²/s, = 1.2 × 10^-6 cm²/s, = 7.0 × 10^-8 cm²/s, and = 5 × 10^-7 cm²/s. Diffusion of anions within a conventional resin, Dowexl®, was slower: = 3.5 × 10^-7 cm²/s, = 6 × 10^-7 cm²/s, = 2.7 × 10^-8 cm²/s, and = 5 × 10^-7 cm²/s. A higher rate of ion diffusion and the bead-size uniformity may make monodisperse Dowex Monosphere Tough Gel TG550A resin attractive for analytical applications. The difference in properties between conventional and monodisperse resins is not sufficient to affect the large volume applications of resins. © 1997 John Wiley & Sons, Inc. J Appl Polm Sci 65:1271–1283, 1997     

Influence of Stabilizer Concentration on Transport Behavior and Thermopower of CNT‐Filled Latex‐Based Composites

The influence of the stabilizer/SWNT ratio on the transport behavior of latex‐based polymer nanocomposites is examined in an effort to improve electrical conductivity while maintaining or improving the Seebeck coefficient (i.e., thermopower). Results show that phonon and electron transport are significantly affected by tube/tube junctions, and the carrier transport across the junctions can be manipulated by altering the stabilizer concentration. Electrical conductivity of composites containing 10 wt.‐% SWNT nearly doubles, becoming greater than 900 S · m^?1, by changing the SWNT:GA ratio from 1:3 to 10:1, while thermal conductivity and Seebeck coefficient remain relatively constant (near 0.25 W · m‐K^?1 and 40 µV · K^?1, respectively).

     

Local Turbulent Energy Dissipation Rate in an Agitated Vessel: Experimental and Turbulence Scaling

The hydrodynamics and the flow field in an agitated vessel were measured using 2-D time resolved particle image velocimetry (2-D TR PIV). The experiments were carried out in fully baffled cylindrical flat bottom vessels 300 and 400 mm in inner diameter. The 300 mm inner diameter tank was agitated by a Rushton turbine 100 mm in diameter, and the 400 mm inner diameter tank was agitated by a Rushton turbine 133 mm in diameter. Three liquids of different viscosities were used as the agitated liquid: (i) distilled water (ν = 9.35 × 10^–7 m²/s), (ii) a 28 vol % aqueous solution of glycol (ν = 2 × 10^–6 m²/s), and (iii) a 43 vol % aqueous solution of glycol (ν = 3 × 10^–6 m²/s). The velocity fields were measured at an impeller rotation speed in the range from 300 to 850 rpm, which covers the Reynolds number range from 50000 to 189000. This means that fullydeveloped turbulent flow was reached. The experiments were performed to investigate the applicability of the following relations: ε* = ε/(u⁴/ν) = const, vK/u = const, Λ/ηK = const, τ_Λ/τ_K = const, ε* = ε/((Nd)4/ν) = const, Λ/d ∝ Re^–1, ηK/d ∝ Re^–1, vK/(Nd) = const, Nτ_Λ ∝ R^–1, Nτ_K ∝ Re^–1, and ε/(Nq) ∝ Re. These formulas were theoretically derived in our previous work, using turbulence theory, in particular, using turbulence spectrum analysis. The correctness of the proposed relations is investigated by statistical hypothesis testing.     

Stepwise Stability Constants of Trivalent La,Ce, Pr,and Sm Complexes of Isopropylmercaptan

The complexation of La³⁺, Ce³⁺, Pr³⁺ and Sm³⁺ ions with isopropylmercaptan has been studied by potentiometric and conductometric titration techniques in aqueous – 10% ethanolic (V/V) medium . Title metal ions form 1:1, 1:2 and 1:3 complexes in the pH range 6.0–8.0 with considerable overlapping. Their log K_stab. values are determined at 15°, 25° and 35°C at ionic strength μ = 0.1 M (NaClO₄) by applying Calvin and Melchior's extension of Bjerrum method. The values of thermodynamic parameters ΔG, ΔH and ΔS have been calculated at 25°C with the help of an isobar and Gibb's Helmholtz equation. The trend in the stability constant values of the metal-complexes has been found to be .     

Sulphoxidation of methyl radicals

The reaction of sulphur dioxide-oxygen mixtures with methyl radicals, generated by the photolysis of azomethane at Λ 3400 Å, has been studied in the temperature range 50–150° in an attempt to evaluate some of the basic reactions involved in the sulphoxidation of free radicals and hydrocarbons. Addition of sulphur dioxide to a mixture of methyl radicals and oxygen leads, unexpectedly, to an initially increased consumption of oxygen. A rate constant has been determined for the reaction: a value of 1·7 × 10¹⁶ mole^?2 cm⁶ sec^?1 being obtained. Using this value, the rate constant for the reaction: has been estimated to be ～ 7·8 × 10⁷ mole^?1 cm³ sec^?1. Comparison of the reactions of acetyl and methylsulphonyl radicals with oxygen and with radicals in dicates that in both cases acetyl radicals are much more reactive by ～ 10³ times.     

Vapour pressure and vapourisation enthalpy of pyridine N‐oxide

The vapour pressure of pyridine N‐oxide was measured using a boiling point method at different temperatures from 389.02 to 546.33 K and the constants of the Antoine equation for the substance were determined. The vapourisation enthalpy of pyridine N‐oxide at the normal boiling point is calculated to be 58.8 ± 1.8 kJ mol^?1. Based on Othmer's method, the standard enthalpy of vapourisation is estimated to be 66.6 ± 0.1 kJ mol^?1 by using pyridine as the reference substance. Furthermore, Watson equation is employed to verify the reliability of and the results demonstrate that the value of is acceptable. © 2011 Canadian Society for Chemical Engineering     

Differential scanning calorimetry analysis of thermoset cure kinetics: Phenolic resole resin

The Differential Scanning Calorimetry (DSC) trace for a commercial phenolic resole resin shows two distinct peaks. Assuming that these represent two independent cure reactions results in a kinetic model of the form: with κ_i = κ_io exp(-B_i/T). The Arrhenius parameters were estimated from a plot of ln(β/T) versus 1/T_p. The parameters, p, n₁, and n₂ were obtained by writing the DSC response predicted by the equation above in terms of a function which contains temperature as the only variable. with $ \theta _i = \left({1/\beta} \right)\int_{T_0}^T {\kappa _i dT \le r_i} $ dT ? r_i and r_i = 1/(1-n_i). Fitting this equation to the DSC response measured at a scan rate of 4°C/min obtains p ≈ 0.66; n₁ ≈ 0.55; n₂ ≈ 2.2; B₁ ≈ 8285; B₂ ≈ 7480; κ₁ ≈ 1. 12 × 10⁸ s^?1; κ₂ ≈ 0.99 × 10⁶ S^?1.     

Kinetics and mechanism of the thermal decomposition of potassium persulphate ions in aqueous solutions at 50°C in the presence of nitrogen gas and methacrylonitrile monomer

The initial rate of persulphate (I) decomposition at 50°C in the presence of nitrogen and methacrylonitrile (MAN) in an unbuffered aqueous solution (pH 4–7) may be written as: in the concentration ranges of persulphate (I) (0.25–2.50) × 10^?2 (m/dm³) and of (MAN) 0.18–0.36 (m/dm³). During the reaction, a white substance (polymethacrylonitrile) separates out in the colloidal state or in the precipitate form from the medium depending on the ionic strength of the medium. The pH of the medium was found to decrease rapidly and continuously with time in the absence of methacrylonitrile, but it decreased slowly and continuously with time in the presence of the monomer, MAN. If an additional quantity of MAN is injected late in a run, the rate of persulphate decomposition is further accelerated in a given run. However, the rate of persulphate decomposition is found to decrease continuously in the presence of MAN with time, i.e., as the monomer is converted to polymer. It is suggested that MAN accelerates the decomposition of persulphate ions, due to the following reactions in the aqueous phase: and where (M_j^˙)w is a-water soluble oligomeric or polymeric (j = 1–10) free radical. The estimated values of k₅ and k₁₀ are 1.05 × 10^?5 and 1.14 × 10³ (in dm³/m/s), respectively.     

Functional characterization of a thermostable methionine adenosyltransferase from <Emphasis Type="Italic">Thermus thermophilus</Emphasis> HB27

MATTt (a thermostable methionine adenosyltransferase from Thermus thermophilus HB27) was overexpressed in Escherchia coli and purified using Ni-NTA affinity column. The enzymatic activity of MATTt was investigated in a temperature range from 30 °C to 90 °C, showing that MATTt exhibited a high enzymatic activity and good thermostability at 80 °C. Circular dichroism spectra reveals that MATTt contains high portion of β-sheet structures contributing to the thermostability of MATTt. The kinetic parameter, K _m is 4.19 mmol/L and 1.2 mmol/L for ATP and methionine, respectively. MATTt exhibits the highest enzymatic activity at pH 8. Cobalt (Co²⁺) and zinc ion (Zn²⁺) enhances remarkably the activity of MATTt compared to the magnesium ion (Mg²⁺). All these results indicated that the thermostable MATTt has great potential for industry applications.

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SINGLE-LAYER DRYING BEHAVIOR OF MEXICAN TEA LEAVES (CHENOPODIUM AMBROSIOIDES) IN A CONVECTIVE SOLAR DRYER AND MATHEMATICAL MODELING

Single-layer solar drying experiments were conducted for Mexican tea leaves (Chenopodium ambrosioides) grown in Marrakech. An indirect forced convection solar dryer was used in drying the Mexican tea leaves at different conditions such as ambient air temperature (21° to 35°C), drying air temperature (45° to 60°C) with relative humidity (29 to 53%), airflow rate (0.0277 to 0.0556 m ³/s), and solar radiation (150–920 W/m²). The experimental drying curves showed only a falling rate period. In order to select the suitable form of drying curves, 14 mathematical models were applied to the experimental data and compared according to their statistical parameters. The main factor in controlling the drying rate was found to be the temperature. The drying rate equation was determined empirically from the characteristic drying curve. The diffusion coefficient of the Chenopodium ambrosioides leaves was estimated and varied between 1.0209 × 10^?9 and 1.0440 × 10^?8 m ²·s^?1.The activation energy was found to be 89.1486 kJ·mol^?1.     

Density and viscosity of ammonium nitrate,ammonium nitrate–potassium chloride and ammonium nitrate—ammonium phosphate melts

The results of density and viscosity measurements are given for ammonium nitrate and the salt mixtures ammonium nitrate—potassium chloride and ammonium nitrate-ammonium dihydrogen phosphate. The latter system is complicated because of the formation of non-ortho phosphates and the results obtained refer to the equilibrium mixture obtained after heating for 3 h at 180°c. After this treatment, about 40% of the phosphate was converted to non-ortho forms. The density of ammonium nitrate is given by: for values of t between 170°c and 190°c. Similar relationships can be deduced for the solutions. The viscosity of ammonium nitrate, in centipoises, is given approximately by: for values of T between 443° and 453° k. Similar relationships hold for the nitrate—phosphate solutions.     

Dissolution of ferritic stainless steel scrap in hydrochloric acid

The dissolution of a ferritic stainless steel (15.44% Cr, 0.39% Mn, 0.12% C) in hydrochloric acid has been investigated from the point of view of large scale processing. Over the range of experimental conditions employed, the rate of dissolution at 80.5°C can be represented by the equation: where [MCl₂] is the total molar concentration of divalent metal chlorides in the acid solution. The rate of dissolution is not influenced by the degree of agitation. The apparent activation energy is 21.6 K. cal. mole^?1.     

Thermal decomposition of potassium persulfate in aqueous solution at 50°C in an inert atmosphere of nitrogen in the presence of acrylonitrile monomer

The rate of thermal decomposition of persulfate in aqueous solution in the presence of acrylonitrile (AN) monomer (M) and of nitrogen, may be written as: in the concentration range of persulfate (1.8 to 18.0) ×10^-3, and of monomer (M), 0.30 to 1.20, mol dm^-3. It was observed that the pH of the solution containing persulfate and monomer did not alter during polymerization if the monomer concentrations were close to its solubility under the experimental conditions. Conductance of the aqueous solutions of persulfate and monomer was found to decrease during the reactions. In an unbuffered aqueous solution containing only persulfate, however, the pH was found to decrease continuously at 50°C with time, while the conductance of the solution was found to increase. The monomer (AN) had no effect on the glass electrodes of the pH meter in aqueous solutions, and also on the electrodes of the conductivity cell. It has been suggested that the secondary or induced decompositions of persulfate were due to the following elementary reactions: where (M_j^· radicals (j = 1 to 10) are water-soluble oligomeric or polymeric free radicals. k_x and k_y at 50°C have been estimated as 1.70 X 10^-5 and 5.08 × 10³ dm³ mol^-1 s^-1, respectively. By measuring pH of freshly prepared persulfate solutions at 25°C, it is suggested that 0.05–0.30% of persulfate reacts molecularly with water (i.e., hydrolysis), as soon as it (10^-3 to 10^-2 mol dm^-3) is added to distilled water (pH 7.0). This hydrolysis was found to be stopped in dilute sulfuric acid solution (pH 3–4).     

Kinetics of the vapour phase oxidation of ethyl alcohol on vanadium pentoxide catalyst

The kinetics of V₂O₅-catalysed vapour phase oxidation of ethyl alcohol were studied with the help of a differential fixed-bed flow reactor. The partial pressures of alcohol, oxygen and water were varied in the ranges: 6–10 × 10^–3 atm, 1–10 % × 10^–1 atm, and 0–169 × 10^–3 atm respectively in the temperature range 228–264 °C. The rate equation: deduced by the assumptions of the steady-state redox mechanism, was found to conform to the experimental results. The energies of activation for the partial reactions, namely reduction and oxidation of the catalyst, were found to be 18.9 and 11.8 kcal/mol. The influence of different products was also studied in detail.     

Effect of tris(bathophenanthroline)iron(III) on the polymerization of styrene

The polymerization of styrene at 60°C initiated by 2,2′-azobisisobutyronitrile (AIBN) was studied in N,N-dimethylformamide (DMF) in the presence of tris-(bathophenanthroline)iron(III) complex, [Fe(bathophen)₃]³⁺. The complex was prepared in situ by mixing hexakis(N,N-dimethylformamide)iron(III) perchlorate with bathophen-anthroline (systematic IUPAC nomenclature: 4,7-diphenyl-1,10-phenanthroline) in the molar ratio of 1 : 3. The equilibrium constant for was 3.12×10³ L³ mol⁻³. The transfer constant for bathophenanthroline was found to be 0.38 ± 0.01 for the styrene/DMF system at 60°C. Mean velocity constant at 60°C for interaction of polystyryl radical with [Fe(bathophen)₃]³⁺ was 3.73× 10⁴ L mol⁻¹ s⁻¹. © 1996 John Wiley & Sons, Inc.