The kinetics and mechanism of the chloride-chlorate reaction

The kinetics of the reaction have been studied at 25°C. in strong acid solution; the effects of acidity, chloride, chlorate and chlorine are reported. A mechanism is postulated to interpret the peculiar features of this reaction as well as the stoichiometry and some of the kinetics of the parallel reaction The mechanism involves HClO₂ and HOCl as intermediates General rate expressions are derived for the formation of chlorine dioxide and chlorine, and the individual rate constants are calculated. An expression is obtained for the relationship between the ratio of chlorine dioxide to chlorine produced and the ratio of chlorate to chloride.     

Spin coating behavior of polyimide precursor solutions

Experimental data confirm the utility of the following simple equation in predicting the spin coating behavior of polyimide precursor solutions: in which .     

Catalytic oxidation of benzene to maleic anhydride in a continuous stirred tank reactor

The kinetics of the vapor phase oxidation of benzene has been studied over an industrial catalyst in a continuous stirred tank reactor in the temperature range from 280 to 430°C and at atmospheric pressure. The products obtained are maleic anhydride, carbon oxides and water. The rate of the overall reaction (disappearance of benzene) is represented by the following expression based upon a steady state adsorption model The rate of formation of maleic anhydride is correlated by the equation which allows for a homogeneous depletion of maleic anhydride. The rate constants k_B, k_O, k_2(g) were found to follow Arrhenius behavior.      

Transferts thermiques entre un serpentin et des fluides newtoniens ou non—newtoniens agités par une turbine à pales inclinées dans une cuve

The present work deals with the heat transfer from a hélicoïdal worm to newtonian or non-newtonian liquids, which and stirred by a 4 pitched blade-turbine in a cylindrical tank. The effective viscosity of the pseudoplastic liquids is determined by the Metzner-Otto model combined with the Ellis rheological equation. The heat transfer in the newtonian fluids in a turbulent system is most precisely represented by the following equations: (a) (b) In the case of non-newtonian fluids and of downward pumping, the following equation enables to obtain a very precise evaluation of the heat-transfer coefficient in a transitional flow.      

Struktur und eigenschaften von ABS-polymeren II.. Grenzviskositäts-molekulargewichtsbeziehungen für azeotrope styrol/acrylnitril-copolymerisate

Limiting viscosity numbers of azeotropic copolymers of styrene and acrylonitrile were measured in dimethylformamide (DMF) and in methyl ethyl ketone (MEK). Their weight average molecular weights (10⁴ g/mole ? M_w ? 10⁶ g/mole) were determined by light scattering. The viscosity – molecular weight relationships obtained, are for DMF and for MEK The number average molecular weights were determined by osmotic pressure measurements, and now molecular weight heterogenities were calculated. The homogenity in composition was investigated by light scattering measurements in different solvents. In addition the viscosity-molecular weight relationship for polystyrene in DMF was determined and compared with the relationship for the azeotropic poly (styrene-co-acrylonitriles) and for polyacrylonitrile: On account of the results a possibility is shown for calculating molecular weights of poly (styrene-co-acrylonitrile) of any composition from limiting viscosity numbers and the acrylonitrile contents.     

Some aspects of liquid-solid fluidized beds

Hydrodynamic characteristics of randomly packed fluidized beds were investigated using particles of different sizes and densities fluidized with water. The minimum fluidization velocity was found to be independent of the initial bed height. The minimum fluidization velocity was found to be Bed expansion followed the Richardson Zaki relationship and the exponent 'n' has been correlated as:      

Elutriation characteristics of solids from liquid fluidized bed systems Part I: Onset of elutriation

Experimental data for the minimum elutriation velocity u_me of solids for 134 different systems have been correlated by The ranges of the different groups investigated were as follows: For all of the experiments, the fluidizing liquid was water and the tube had an inside diameter of 4.92 cm. The standard deviation for the above correlation is 21.6 per cent.     

Heat transfer to agitated non-newtonian fluids

Heat transmission to agitated non-Newtonian liquids in a jacketed vessel has been studied. Heat transfer tests were conducted under unsteady-state conditions with pseudo-plastic solutions (behavior index range: 0.343 to 0.633). For a generalized Reynolds number ranging from 100 to 5000, two correlations were found: The use of a generalized Sieder and Tate number resulted in an equation combining both heating and cooling data with a somewhat higher mean deviation (19.3%):      

Direct contact heat transfer between two immiscible liquids during vaporisation

A cine-photographic technique was used to study the evaporation of single droplets of furan, cyclopentane and isopentane rising in water. Measurements were possible over a range from zero to 10% evaporation. The best correlation of the data for the three systems over the measurable range of parameters was: All the data was fitted by this equation to within ± 20%. A second correlation with a slightly larger variance because of the manner in which the density ratio term varies with % evaporation, was recommended for extrapolation to higher percentage evaporations.     

Studies on graft copolymerization of methyl methacrylate onto poly(vinyl chloride)

The grafting of methyl methacrylate on suspension-grade poly(vinyl chloride) in the presence of lauroyl peroxide has been studied. The reaction was carried out in a water suspension of the starting PVC polymer swollen with the monomer. The influence of reaction temperature, T, starting monomer/polymer ratio, M/P, and initiator concentration, I, in the monomer on the grafting efficiency of both polymers present in the system was found to be well described by the following linear regression equations: and      

A modified correlation to predict the minimum velocity required to elutriate solids from a liquid-fluidized bed

The consideration of sphericity of solids for the prediction of u_me gives rise to some improvement of the correlation proposed earlier by the author. In the absence of wall-effect, the following correlation is obtained: which gives a standard deviation of ± 16.3% for 138 different experiments as against ± 21.6% for 134 runs by the correlation reported earlier. The ranges of the various groups are      

Prediction of steady-state dispersion height in the disengaging section of an extraction column from batch settling data

The decay of a dense dispersion formed under calm conditions is given by Experiments in a batch vessel with different liquid-liquid systems and initial drop diameters show that the dimensionless constant K is equal to 26,000. This agrees with the value previously determined from the variation in steady-state dispersion height with throughput in spray columns, the analogous equation being The results can thus be used to predict the height of the dispersion formed in the disengaging section of extraction columns.     

Drainage in thin planar non-newtonian fluid films

Equations for the radial and linear drainage of non-Newtonian fluids in horizontal and inclined films are presented. For a power law fluid with index m, the variation in dimensionless film thickness Δ with dimensionless time T is given by: where Δ and T are appropriately defined for drainage in radial horizontal and linear inclined films. The corresponding approximate expression for a Bingham plastic fluid is: in which A is the minimum film thickness defined appropriately at the asymptotic limits when Δ » A and Δ ? A.     

Momentum and heat transfer characteristics of liquid-liquid dispersions in turbulent flow

The momentum and heat transfer characteristics of unstable, liquid-liquid dispersions flowing turbulently in a circular tube were investigated. Two mineral oils, a light oil with viscosity of 15 centipoise, and a heavy oil with viscosity of 200 centipoise were used as the dispersed phase while the continuous phase was tap water. At room temperature only, the relative fluidity of the dispersion follows the relation At Reynolds numbers above 60,000 the heat transfer coefficients of all dispersions studied follow the relation where the Prandtl number is that of the continuous phase and the Reynolds number is based upon the viscosity of the dispersion. All properties are evaluated at the film temperature.     

A corresponding states treatment of saturated density,surface tension and capillary constant of cryogenic liquids and refrigerants

Using a new set of energy (kT) and length (σ) parameters, a corresponding states treatment is applied to the calculation of some thermophysical properties in a generalised non-dimensional form. The saturated density is well represented by the following equation: for all the liquids studied here. The surface tension correlations are $ \gamma _r^* = 2.055\left({1.219 - T_r^*} \right)^{1.240} $ for cryogenic fluids and hydrocarbons and $ \gamma _r^* = 2.322\left({1.228 - T_r^* } \right)^{1.244}$ for refrigerants. An interpretation of the index in the density equation and the constants in the surface tension equations is given. Using these correlations, an equation is also proposed for the capillary constant.     

A one-point intrinsic viscosity method for polyethylene and polypropylene

A statistical analysis of dilute solution viscosity data for a wide range of polyethylene and polypropylene samples in Decalin at 135°C has shown that the Martin equation fits the experimental data better than the Huggins equation at higher values of [η]c. A grand average k of 0.139 is applicable to both polymers. Based upon this, tables have been calculated permitting the ready determination of [η] from a single relative viscosity measurement at a known concentration. The Martin equation has been put into a universal form, permitting [η] to be calculated from a measured η_sp if k and c are known. Graphs relating η_sp to [η] are included for use of the Martin equation over wide ranges of both k and c. It was found that the Solomon and Ciuta equation fits the experimental polyethylene and polypropylene data, and the reasons for this are discussed.     

In‐Line Monitoring and Control of Conversion and Weight‐Average Molecular Weight of Polyurethanes in Solution Step‐Growth Polymerization Based on Near Infrared Spectroscopy and Torquemetry

Summary: It is well known that the weight‐average molecular weight ( ) is strictly dependent on conversion in step‐growth polymerizations performed in batch and that the is very sensitive to impurities and molar imbalance. This makes the work of controlling a non trivial job. In this paper a new methodology is introduced for in‐line monitoring and control of conversion and of polyurethanes produced in solution step‐growth polymerizations, based on near‐infrared spectroscopy (NIRS) and torquemetry. A calibration model based on the PLS method is obtained and validated for monomer conversion, while the weight‐average molecular weight is monitored indirectly with the relative shear signal provided by the agitator. Control procedures are then proposed and implemented experimentally to avoid gelation and allow for maximization of . The proposed monitoring and control procedures can also be applied to other step growth polymerizations.

Proposed control scheme.     

The apparent rate constant model for kinetics of radical chain copolymerization: Chemical-controlled process

In this article the kinetics of chemical-controlled radical-chain copolymerization have been reduced to pseudohomopolymerization kinetics by introducing the apparent rate constants, The methods for the determinations of the values of the apparent rate constants, mode of termination, and the methods for the calculation of molecular weights and distributions are proposed. The data required for these determinations and calculations are simply obtained by the usual steady-state method. According to the traditional kinetics along with the definitions of the apparent rate constants, these apparent rate constants as functions of traditional rate constants, monomer compositions, and copolymer compositions are derived. Further utilizing the theoretical expressions obtained, we show that the apparent rate constants are the general rate constants for both radical chain homo- and copolymerizations. The bulk radical copolymerizations of methyl methacrylate and styrene at various monomer feed compositions at 60°C are used to test the proposed model. The empirical apparent rate constants obtained are described well, by the following expressions, and and the mode of termination on the combination termination is where K and K denote the apparent rate constants of propagation and termination, respectively. The term f₁(= 1 ? f₂) stands for the mole fraction of styrene in the monomer solution fed. F₁ is the copolymer composition produced at f₁. β is the mode of termination.     

Adiabatic polymerization of acrylamide using a persulfate–bisulfite redox couple

The temperature rise during the adiabatic polymerization of acrylamide in water has been used to characterize the kinetic parameters. Based on initial rate data, the following equation is obtained: where concentrations of monomer, persulfate, and bisulfite are in mole/kg, T is in K, and t is in min. The order with respect to monomer is confirmed by an analysis of the entire temperature–time record during polymerization. The persulfate–bisulfite couple was studied also in the absence of monomer. Concentrations were measured by UV absorbance and by permanganate titration. The reaction can be represented by: where concentrations are in mole/liter, T is in K, and t is in min.     

A one-point intrinsic viscosity method for hydroxyethylcellulose,hydroxypropylcellulose, and sodium carboxymethylcellulose

Statistical analysis of viscosity measurements on dilute solutions of hydroxyethylcellulose (HEC), hydroxypropylcellulose (HPC), and sodium carboxymethylcellulose (CMC) in the solvents water, 50/50 (v/v) water/ethanol, and 0.1M NaCl, respectively, demonstrated that the Martin equation, fits experimental data better than the Huggins equation, An average Martin k of 0.191 is applicable to a variety of HEC and HPC samples, including fractionated and unfractionated experimental and commercial preparations covering a wide range of substitution. In the case of a similar variety of CMC samples, an average k of 0.161 is characteristic. Based on these k values and using the Martin equation in the form tables were developed which permit direct reading of [η] values corresponding to single η_rel measurements at concentrations of 0.05, 0.10, 0.20, or 0.50 g/dl. Intrinsic viscosities obtained in this fashion differ from those determined by the usual dilution multipoint technique on the same samples by an average of but 2%, at an estimated time saving of 50% or more. This degree of variation is no greater than that expected in routine measurements on duplicate solutions.