Axial mixing of liquid in a turbulent-bed contactor

The axial dispersion of liquid in a 12-in. turbulent-bed contactor has been investigated for three packing sizes: ½-in., 1-in. and 1½-in. The gas and liquid flow rates were varied from 500 to 2700 lb./(hr.)(sq. ft.) and from 1500 to 11,000 lb./(hr.)(sq. ft.) respectively. The transient response technique using KCl solution as the tracer was employed for this purpose. The experimentally determined residence-time distribution curves were interpreted by means of a one-dimensional dispersion model. The axial dispersion coefficient, D_L, was found to increase with increasing gas flow rate, liquid flow rate, or packing size. In terms of Peclet number (N_Pe = ū d_p/D_L), the present data showed that N_Pe was dependent on Reynolds number (N, = d_p ū ρ/μ), Gallileo number (N_Ga = d_p³ ρ³ g/μ²), and reduced gas mass velocity (Δ = (G-G_mf)/G_mf), but the ratio of the Peclet number for a turbulent contactor to the Peclet number for a fixed-bed contactor, N_Pe/N_Peo, depended only on Δ, and the diameter ratio d_p/d_t. A correlation of N_Pe/N_Peθo with Δ and d_p/d_t is presented.     

Polymerization of organic compounds in an electrodeless glow discharge. XI. Pressure in glow discharge

The pressure of a steady-state flow of monomer, p₀, changes to a new steady-state flow pressure, p_g, in glow discharge. The value of p_g is dependent on the flow rate of monomer, the pumping-out rate of the vacuum system for the product gas (which is hydrogen in many cases of plasma polymerization of hydrocarbons), and the characteristic hydrogen yield of a monomer associated with plasma polymerization. The relationships between these factors were established and examined for plasma polymerizations of acetylene, ethylene, and acrylonitrile.     

Tuning the Structural,Electronic, and Magnetic Properties of Strontium Titanate Through Atomic Design: A Comparison Between Oxygen Vacancies and Nitrogen Doping

The structural, electronic, and magnetic properties of seven sets of SrTiO_2.75 (oxygen vacancies) and SrTiO_2.75N_0.25 (nitrogen doping) models were investigated by the first principles calculations based on density functional theory. Our results indicated that oxygen vacancies tended to align in a chain sandwiched with Ti atoms, whereas doped nitrogen atoms (substituting oxygen atoms in SrTiO₃) preferred other arrangements rather than a chain. In addition, under stable arrangement, SrTiO_2.75 showed no magnetism, whereas magnetic moments appeared in other meta‐stable SrTiO_2.75 configurations as well as in SrTiO_2.75N_0.25, which is attributed to the Ti 3d orbitals and nitrogen p orbitals, respectively. Our results suggest a possible route for tuning magnetic and electronic properties of SrTiO₃ by atomic design.     

Influence of geometry on gas holdups in a reversed flow jet loop reactor

The effects of ratio of draft tube to reactor diameter (D_d/D), liquid nozzle diameter (d_N), aeration tube diameter (d_G) and immersion height of the two-fluid nozzle into the draft tube (H_N) on overall and annulus gas holdups for the air-water system were evaluated experimentally in a reversed flow jet loop reactor over wide ranges of gas and liquid flow rates. Both the gas holdups increased with increasing gas and liquid flow rates and with decreasing d_N and H_N. The influence of d_G on gas holdups is found to vary with gas flow rates. Correlations are proposed to predict gas holdups.     

Experimental Studies on Suspension of Solid Particles in a Low‐Shear Stirred Vessel

A low‐shear stirred vessel was explored. Experimental studies on the suspension of solid particles in solid‐liquid and gas‐solid‐liquid systems were conducted to examine the performance of this new reactor. The method based on the power number curve was modified to determine the critical impeller speeds required for just complete off‐bottom suspension of solids under non‐gassed (N_js) and gassed conditions (N_jsg) in this reactor, and a PC‐6A fiber‐optic probe for the measurement of solid distribution was used to complementarily validate this method. A more homogeneous flow field was gained with a draft tube installed, so that the standard deviations of average shear rate and maximal shear rate are reduced. The modified power consumption method can determine N_js and N_jsg, and the values of N_js with a draft tube are much lower than those without it. N_jsg increases slightly with increasing gas flow rate, and N_jsg with a higher solid weight fraction is larger in this lower‐shear reactor.     

Normal stresses in flow of polyvinyl chloride plastisols

In the steady state flow of many liquids, such as polymer solutions and melts, the first normal stress difference, N₁ = σ₁₁ ? σ₂₂, is positive. However, with liquid crystal systems and some colloidal suspensions, negative values of N₁ were reported in literature. In our past work with a commercial polyvinyl chloride plastisol, negative values were observed. During the steady state flow, the plastisol undergoes stress‐induced phase separation into an immobilized layer and a mobile phase. The concentration difference between the two phases gives a rise to an osmotic pressure difference, Δπ, which is countered by a normal stress, N, generated by the flow. Because N is balanced with Δπ, N cannot be observed directly. In this work, N is identified as an isotropic and N₁, directional. The disturbance among rotating particles in the mobile phase produces two effects; one is an increase of pressure, which is N; the other, N₁ is associated with a small volume increase, which is directed towards the opening of the rheometer. The directional expansion is caused by the shear‐stress gradient in the liquid between the rotating particles. © 2006 Wiley Periodicals, Inc. J Appl Polym Sci 103: 2769–2775, 2007     

Preparation of polydimethylsiloxane nanolatices by emulsion polymerization in a water–aminoethanol system

Stable and translucent polydimethylsiloxane nanolatices in a water–aminoethanol (AE) system were prepared by the emulsion polymerization of octamethylcyclotetrasiloxane (D₄) with nonionic polyoxyethylene alcohol ethers and polyoxyethylene aryl ether as surfactants and with KOH as an initiator. The effects of the AE concentration on the emulsion polymerization rate (R_p) of D₄ and the physical properties of the resultant nanolatices were investigated. Increasing the AE concentration in the reaction mixture dramatically increased the emulsion R_p value of D₄, and the kinetics of the D₄ emulsion polymerization in this system were consistent with the Morgan–Kaler theory of microemulsion polymerization. When the AE concentration in the emulsion increased, the transparency value of the resultant emulsion increased, and the size of the droplets in the resultant nanolatices decreased. In addition, the molecular weight of the polysiloxane in the resultant emulsion also increased with the increase in the AE concentration in the reaction mixture. A nanolatex prepared by the emulsion polymerization of 0.98M D₄ with 185 g/L AE had a transparency value of 80.9% and a mean diameter of 59.5 nm. The morphology of polysiloxane nanolatices cured with (N,N‐diethylaminomethyl)‐triethoxysilane was observed with transmission electron microscopy, and the size of the globular particles was consistent with that obtained by dynamic light scattering. © 2005 Wiley Periodicals, Inc. J Appl Polym Sci 98: 347–352, 2005     

Polymerization of styrene in an electrodeless glow discharge

The polymerization (polymer deposition) rate of styrene in an electrodeless glow discharge from styrene vapor and a mixture of styrene vapor and gas (H₂, He, A, and N₂) was investigated. The rate of polymerization, R, was found to be independent of the discharge power. The rate of polymerization of the pure monomer was found to be proportional to the square of monomer pressure p_M. The addition of gas increased the rate of polymerization depending upon the partial pressure of the gas, p_x, and R can be generally expressed by R = a[p_M]²{1 + b[p_x]}. The value of b is dependent of the type of gas and follows the order of N₂, > A > He > H₂. The distribution of polymer deposition was found to be nearly independent of the partial pressure of the gas and of the discharge power with N₂ and H₂ as plasma gas; however, with He and A, the distribution is highly dependent on the partial pressure of the gas and on the discharge power. The study strongly suggests that polymerization occurs in the vapor phase and that the growing polymer radicals deposit on the surface of the discharge vessel, yielding highly crosslinked polymer deposition.     

Oxidative conversion of thiourea and N-substituted thioureas into formamidine disulfides with acidified chloramine-T: a kinetic and mechanistic approach

The kinetics of oxidation of thiourea and N-substituted thioureas namely: N-methylthiourea, N-allylthiourea N-phenylthiourea and N-tolylthiourea to the corresponding formamidine disulfides by sodium N-chloro-p-toluenesulfonamide or chloramine-T (CAT) in the presence of HClO₄ has been investigated at 278 K. The reactions follow identical kinetics for all thioureas, being first order each with respect to [CAT]_o, [Thiourea]_o and [H⁺]. Ionic strength of the medium and addition of p-toluenesulfonamide or halide ions have negligible influence on the rate. The solvent isotope effect has been studied using D₂O in the case of the oxidation of thiourea. Decrease in the dielectric constant of the medium by adding methanol decreases the rate. The reactions were studied at different temperatures, and the composite activation parameters have been computed. An isokinetic relationship was observed with β=314 K, indicating that enthalpy factors control the reaction rate. Under comparable experimental conditions, the rate of oxidation of thioureas increases in the order: N-allylthiourea>N-phenylthiourea>N-methylthiourea>thiourea>N-tolylthiourea. A mechanism involving the interaction of conjugate acid (CH₃C₆H₄SO₂NHCl) and substrate giving an intermediate complex, in a slow step, has been suggested. The derived rate law is in agreement with the observed kinetics.     

Effective Two-Stage Estimation for a Linear Function of High-Dimensional Gaussian Means

We consider fixed-size estimation for a linear function of mean vectors from π _i : N _p (μ _i , Σ _i ), i = 1,…, k. The goal of inference is to construct a fixed-span confidence region with required accuracy. We find a new sample-size formulation and propose a two-stage estimation methodology to give the fixed-span confidence region satisfying the probability requirement approximately. We show that the proposed methodology greatly reduces the sample size to enjoy the asymptotic first-order consistency when the dimensionality p is extremely high. With the help of simulation studies, we show that the proposed methodology is still efficient even when p is moderate. We give an actual example to illustrate how it should be done by using the proposed methodology in the inference.     

The relationship between Bray's P1, modified NaHCO3, New Mehlich and NH4F. HF extractants for P in savannah soils of western Nigeria

Sixty surface (0–15 cm) soil samples and 20 field sites with different cropping histories were selected from the major soil types of the western Nigeria basement complex savannah. Available P was evaluated with six different extractants, namely Bray's P₁, 0.1N AHDF (pH 4.1–4.3), 0.1N AHDF (pH 5.0), 0.05N AHDF (pH 7.0), New Mehlich and modified Olsen's 0.5M NaHCO₃ (pH 8.5).The highest amount of P was extracted by 0.1N AHDF (pH 4.1–4.3), while 0.05N AHDF (pH 7.0) extracted the lowest. In the greenhouse, the New Mehlich extractant had the best correlation with P uptake (r = 0.95,p < 0.001), which was not different from Bray's P₁, 0.1N (pH 4.1–4.3), 0.1N AHDF (pH 5.0) and modified 0.5M NaHCO₃ extractants. Field experiments in the various locations showed a significant correlation between relative maize yield and soil tests. The 0.5M NaHCO₃ had the highest correlation (r = 0.70,p < 0.01) while 0.1N AHDF (pH 4.1–4.3) had the lowest (r = 0.53,p < 0.05).All extractants seem to extract the same forms of P. Although Fe-P contributes the highest amount of active P extracted with the Chang and Jackson procedure, its utilization by the crop seems to be relatively lower than the other P forms. The 0.1N AHDF (pH 4.1–4.3) extracted 38% of this active P form while Bray's P₁, New Mehlich, 0.1N AHDF (pH 5.0), modified 0.5M NaHCO₃ and 0.05N AHDF (pH 7.0) extracted 29, 27, 22, 21 and 7% respectively. It is therefore concluded that any of the following four extractants, namely New Mehlich, 0.5M NaHCO₃, 0.1N AHDF (pH 5.0) and Bray's P₁, could be adopted for routine soil testing for P in the savannah zone of western Nigeria.     

Inhibition Studies on Carbonic Anhydrase Isoforms I,II, IX,and XII with a Series of Sulfaguanidines

Two novel sulfaguanidine series, six N-(N,N′-dialkyl/dibenzyl-carbamimidoyl) benzenesulfonamide derivatives and nine N-(N-alkyl/benzyl-carbamimidoyl) benzenesulfonamide derivatives, were obtained by desulfidative amination of easily accessible dimethyl arylsulfonylcarbonimidodithioates under catalyst- and base-free conditions. The newly synthesized compounds were tested for the inhibition of four different isozymes of human carbonic anhydrase (hCA I, II, IX and XII, EC 4.2.1.1). Both series reported here were inactive against the off-target isozymes hCA I and II (K_i>100 μM). Interestingly, all investigated compounds inhibited both target isozymes hCA IX and XII in the submicromolar to micromolar ranges in which K_i values spanned from 0.168 to 0.921 μM against hCA IX and from 0.335 to 1.451 μM against hCA XII. The results indicated that N-(N-alkyl/benzyl-carbamimidoyl) benzenesulfonamides were slightly more potent inhibitors than N-(N,N′-dialkyl/dibenzyl-carbamimidoyl) benzenesulfonamides. Among the evaluated compounds, N-n-octyl-substituted N-carbamimidoylbenzenesulfonamide showed the most significant activity with a K_i value of 0.168 μM against hCA IX, which was four-fold more selective toward this isozyme versus hCA XII. Again, another derivative from N-(N-alkyl/benzyl-carbamimidoyl) benzenesulfonamide series, N-p-methylbenzyl-substituted N-carbamimidoylbenzenesulfonamide, demonstrated superior inhibitory activity against hCA XII with a K_i value of 0.335 μM.     

Iron‐Catalyzed Oxidative Mono‐ and Bis‐Phosphonation of N,N‐Dialkylanilines

The dehydrogenative α‐phosphonation of substituted N,N‐dialkylanilines by dialkyl H‐phosphonates was achieved under mild conditions by using environmentally benign iron(II) chloride as catalyst and tert‐butyl hydroperoxide as oxidant. The reaction proceeded in the presence of electron‐donating (methoxy, methyl, benzyl) and electron‐withdrawing ring‐substitutents (bromo, carbonyl, carboxyl, m‐nitro) in moderate to good yields. The X‐ray crystal structure of N‐(5,5‐dimethyl‐2‐oxo‐2λ⁵‐[1,3,2]dioxaphosphinan‐2‐yl‐methyl)‐N‐methyl‐p‐toluidine was determined. Bis‐(4‐(dimethylamino)phenyl)methane and bis‐4,4′‐(dimethylamino)benzophenone underwent bisphosphonation selectively by respective monophosphonation at the remote dimethylamino groups. Furthermore, the use of excess dialkyl H‐phosphonate and oxidant allowed us to functionalize both methyl groups of N(CH₃)₂ in N,N‐dimethyl‐p‐toluidine and N,N‐dimethylaminomesidine, respectively, to obtain α,α′‐bisphosphonatoamines in high yield.     

Toughening of aromatic diamine-cured trifunctional epoxy resins by modification with N-phenylmaleimide–styrene copolymers containing pendant p-hydroxyphenyl groups

N-Phenylmaleimide (PMI)–N-(p-hydroxy)phenylmaleimide (HPMI)–styrene (St) terpolymers (HPMS), containing pendant p-hydroxyphenyl (HP) groups, were prepared and used to improve the toughness of triglycidyl aminocresol epoxy resin cured with p,p′-diaminodiphenyl sulfone. HPMS was effective as a modifier for the toughening of the epoxy resin. When using 15 wt % of HPMS (1.0 mol % HP unit, M_w 129,000), the fracture toughness (K_IC) for the modified resin increased 190% with a medium loss of flexural strength. The toughening of epoxies could be attained because of the cocontinuous phase structure of the modified resins. The decrease in flexural strength was suppressed to some extent by introducing a functional group into the modifier. The toughening mechanism was discussed in terms of the morphological behavior of the modified epoxy resin system. © 1995 John Wiley & Sons, Inc.     

A Reaction of Thioamides with Zinc Ammoniates Leading to Simple Amidines. Discovery of a New Zwitterionic Monomethylamidine

The reacion of thioamides with the R₁R₂N–ZnCl ammoniates leads to N-mono-, N,N′-di-, N,N-disubstituted, and unsubstituted amidines with high concentrations of amines in absolute ethanol. The efficient direct formation of the N,N′-dimethylamidine can be explained by a greater reactivity of methylamine compared with dimethylamine. Discovery of a new zwitterion (induced by a carbonyl oxygen) suggests that the stabilization in the thymine N-methylamidine is too slight to prevent the subsequent reaction with methylamine.     

Significance of the solubility of hydrocarbon gases in liquids in relation to the intermolecular structure of liquids and the essential pattern of data for all gases

Solubility data expressed as mole ratio, x_RH (moles of RH per mole of liquid S) have been measured for propane and n-butane in a number of type-representative organic liquids, S, at different temperatures, t °C, and pressures, p_RH ≤ 760 mm. These data, and those for methane, ethane and radon, afford support in the development of the essential pattern of data for all gases, A, and all liquids, S. This pattern indicates that the first factor determining the solubility of any gas, A, in any liquid, S, is its tendency to condense to a liquid at the operational temperature, t °C (e.g. 0 °C to 25 °C), shown by its vapour pressure p°_A over liquid A (or its equivalent for a gas above the critical temperature) at t °C. Since p°_A emerges from the b.p. of A at 1 atm, and b.p. data are readily seen in text-books, the b.p. may be taken as an initial index of the first factor. In the N_A–p_A diagram for a given gas A and different liquids, S, at a fixed t °C, N_A being the mole fraction of A, the straight line joining p°_A with p_A = 0 is herein called the reference line, the R-line, of A; it is a real property of A, and it represents the plot of N_A–p_A for a hypothetical liquid, S, having in effect an overall inter-molecular structure equivalent to liquid A, in imagination, A itself. The N_A–p_A plot for another liquid, S, involves a second and a third factor, the second being the intermolecular structure of S, in a dynamic sense, and the third, the inevitable interaction of A with S. These factors are deemed to emerge from changes in electron density, designated for the present as acid-base functions. The spread of x_RH values is indicated by x_PrH = 0.322, x_BuH = 5.25, for di-n-octyl ether; x_PrH = about 0.000042, x_BuH = about 0.000040, for water, for 5 °C and P_RH = 760 mmHg.     

Synthesis and Performance Evaluation of CO2/N2 Switchable Tertiary Amine Gemini Surfactant

A type of switchable tertiary amine Gemini surfactant, N,N′‐di(N,N‐dimethyl propylamine)‐N,N′‐didodecyl ethylenediamine, was synthesized by two substitution reactions with 3‐chloro‐1‐(N,N‐dimethyl) propylamine, bromododecane and ethylene diamine as main raw materials. The structure of the product was characterized by FTIR and ¹H‐NMR. We also investigated the surface tension when CO₂ was bubbled in different concentrations of surfactant solution and the influence of different CO₂ volumes on surface tension under a constant surfactant concentration. Finally the surface tension curve and the related parameters were acquired by surface tension measurements. The experimental results showed that the structure of the synthesized compounds were in conformity with the expected structure of the surfactant, and displayed a better surface activity after bubbling CO₂. The critical micelle concentration (CMC) surface tension at CMC (γ_cmc) pC₂₀ (negative logarithm of the surfactant's molar concentration C₂₀, required to reduce the surface tension by 20 mN/m) surface excess (Γ_max) at air/solution interface and the minimum area per surfactant molecule at the air/solution interface (A_min) were determined. Results indicate that the target product had good surface activity after bubbling CO₂.     

Polymerization in an electrodeless glow discharge. II. Olefinic monomers

The rates of polymer deposition from various olefinic monomers in an electrodeless glow discharge were studied. The previously found empirical relationship (with styrene in part I) between the rate of polymer deposition R, the monomer pressure p_M, and gas pressure p_x in a steady-state flow system (i.e., R = a(p_M)² [1 + b(p_x)], R being nearly independent of the discharge power) was also found with all monomers investigated. (The effect of gas was examined with nitrogen in this study.) However, it was found that the polymer deposition is controlled by the monomer flow rate and R_o (in pure monomer flow) is proportional to the flow rate of monomer F_w (based on the weight); i.e., R_o = kF_w, where k is a characteristic rate constant of the polymerization. Olefinic monomers can be generally classified into two major groups, i.e., type A monomers which predominantly polymerize, and type B monomers which decompose in a glow discharge. Type B monomers have smaller values of a and k compared to type A monomers. The values of a and k for type A monomers both increase with increasing molecular weight of the monomer. The values of k for all monomers investigated are within roughly an order of magnitude, indicating that the reactivity levels of monomers are very similar in a glow discharge polymerization.     

Synthesis and characterization of novel biocidal cyclodextrin inclusion complexes grafted onto polyamide‐6 fabric by a redox method

The synthesis of immobilized β‐cyclodextrin derivatives onto polyamide‐6 fabric is presented. These novel fabrics were prepared by graft‐copolymerization of glycidyl methacrylate (GMA) onto polyamide 6 fabric, using a chemical redox system K₂S₂O₈/CuSO₄·5H₂O, followed by reaction of β‐cyclodextrins (CD) or monochlorotriazinyl (MCT β‐CD) with the GMA epoxy group. Some biocidal guests were complexed into CD cavity including p‐hydroxy benzoic acid, AgNO₃–ethanolamine mixture, iodine, N,N‐diethyltoluamide (DETA), citronella, jasmine, and sweet basil. Characterization of the novel fabrics was done by Fourier transform infrared spectroscopy (IR), electron scanning microscopy (SEM), and thermo gravimetric analysis (TGA). The biocidal activity of the grafted fabrics was tested against five strains of microorganisms. © 2005 Wiley Periodicals, Inc. J Appl Polym Sci 99: 2586–2593, 2006     

Synthesis of methyl methacrylate and N‐aryl itaconimide block copolymers via atom‐transfer radical polymerization

The paper describes the synthesis of block copolymers of methyl methacrylate (MMA) and N‐aryl itaconimides using atom‐transfer radical polymerization (ATRP) via a poly(methyl methacrylate)–Cl/CuBr/bipyridine initiating system or a reverse ATRP AIBN/FeCl₃·6H₂O/PPh₃ initiating system. Poly(methyl methacrylate) (PMMA) macroinitiator, ie with a chlorine chain‐end (PMMA‐Cl), having a predetermined molecular weight (M_n = 1.27 × 10⁴ g mol^?1) and narrow polydispersity index (PDI = 1.29) was prepared using AIBN/FeCl₃·6H₂O/PPh₃, which was then used to polymerize N‐aryl itaconimides. Increase in molecular weight with little effect on polydispersity was observed on polymerization of N‐aryl itaconimides using the PMMA‐Cl/CuBr/Bpy initiating system. Only oligomeric blocks of N‐aryl itaconimides could be incorporated in the PMMA backbone. High molecular weight copolymer with a narrow PDI (1.43) could be prepared using tosyl chloride (TsCl) as an initiator and CuBr/bipyridine as catalyst when a mixture of MMA and N‐(p‐chlorophenyl) itaconimide in the molar ratio of 0.83:0.17 was used. Thermal characterization was performed using differential scanning calorimetry (DSC) and dynamic thermogravimetry. DSC traces of the block copolymers showed two shifts in base‐line in some of the block copolymers; the first transition corresponds to the glass transition temperature of PMMA and second transition corresponds to the glass transition temperature of poly(N‐aryl itaconimides). A copolymer obtained by taking a mixture of monomers ie MMA:N‐(p‐chlorophenyl) itaconimide in the molar ratio of 0.83:0.17 showed a single glass transition temperature. Copyright © 2005 Society of Chemical Industry