THE VAPOR PHASE POLYMERIZATION OF ETHYLENE ON AN ORGANOTITANIUM CATALYTIC SURFACE

1963 ◽  
Vol 41 (5) ◽  
pp. 1265-1275 ◽  
Author(s):  
F. H. C. Edgecombe
Keyword(s):  
Gas Phase ◽  
Constant Pressure ◽  
Solid Catalyst ◽  
Analogue Computer ◽  
First Order ◽  
Titanium Compound ◽  
Volume State ◽  
Rate Of Polymerization ◽  
Order Case ◽  
Vapor Phase Polymerization

The polymerization of ethylene has been studied in the gas phase on a solid catalyst formed by the reaction of an organotitanium vapor with a solid crystalline titanium compound deposited on the walls of a reaction vessel.The rate of polymerization of ethylene was found to be, initially, of first order but as the reaction proceeded departure from the first-order case was observed.Experiments conducted under the condition of constant pressure as well as the usual constant-volume state enabled us, with the aid of an analogue computer, to devise a mathematical model which explained the experimental results in an unique fashion.A measure of the rate constant for catalyst decay was also obtained as well as the activation energy for the overall propagation step in the polymerization of ethylene.

The initiation of styrene polymerization by phenyl titanium tri iso propoxide and titanous tri iso propoxide

1960 ◽  
Vol 254 (1278) ◽  
pp. 408-424 ◽  
Keyword(s):  
Free Radicals ◽  
Rate Constant ◽  
Radical Reaction ◽  
Kinetic Scheme ◽  
Free Radical Reaction ◽  
Styrene Polymerization ◽  
Initiation Rate ◽  
First Order ◽  
Titanium Compound ◽  
Rate Of Polymerization

The polymerization of styrene initiated by phenyl titanium tri iso propoxide has been found to be a free-radical reaction in the region 15 to 50 °C. The photosensitized decomposition of this compound is a first-order reaction yielding free radicals and titanous triisopropoxide. In absence of illumination the presence of titanous triisopropoxide is also necessary to initiate polymerization. The overall rate of polymerization has been found to be expressed by an equation of the form R p = k p k i 1/2 / k i 1/2 [ M ] 3/2 [ Ti ] 1/2 , where the rate constants have their usual significance and [ Ti ] is the concentration of either phenyl titanium triisopropoxide or titanous triisopropoxide, whichever is present in smaller concentration. A kinetic scheme has been presented in which initiation is effected by reaction of monomer with a 1:1 complex of three- and four-valent titanium . The initiation rate constant k i has been evaluated as 7·7 ± 0·2 x 10 -7 mole/l, s, and is constant over the temperature range studied. Titanous tri iso propoxide also undergoes a termination reaction with free radicals resulting in a four-valent titanium compound. The rate constant for this reaction has been evaluated as 4·0 x 10 6 exp [ — (2·8 kcal/mole)/ RT ] mole 1. -1 s -1 .

scholarly journals Perturbation Solution for One-Dimensional Flow to a Constant-Pressure Boundary in a Stress-Sensitive Reservoir

2021 ◽  
Author(s):  
Amarjot Singh Bhullar ◽  
Gospel Ezekiel Stewart ◽  
Robert W. Zimmerman
Keyword(s):  
Approximate Solution ◽  
Pore Pressure ◽  
Constant Pressure ◽  
Initial Permeability ◽  
Order Perturbation ◽  
Zeroth Order ◽  
One Dimensional ◽  
First Order ◽  
Outflow Boundary ◽  
Perturbation Solutions

Abstract Most analyses of fluid flow in porous media are conducted under the assumption that the permeability is constant. In some “stress-sensitive” rock formations, however, the variation of permeability with pore fluid pressure is sufficiently large that it needs to be accounted for in the analysis. Accounting for the variation of permeability with pore pressure renders the pressure diffusion equation nonlinear and not amenable to exact analytical solutions. In this paper, the regular perturbation approach is used to develop an approximate solution to the problem of flow to a linear constant-pressure boundary, in a formation whose permeability varies exponentially with pore pressure. The perturbation parameter αD is defined to be the natural logarithm of the ratio of the initial permeability to the permeability at the outflow boundary. The zeroth-order and first-order perturbation solutions are computed, from which the flux at the outflow boundary is found. An effective permeability is then determined such that, when inserted into the analytical solution for the mathematically linear problem, it yields a flux that is exact to at least first order in αD. When compared to numerical solutions of the problem, the result has 5% accuracy out to values of αD of about 2—a much larger range of accuracy than is usually achieved in similar problems. Finally, an explanation is given of why the change of variables proposed by Kikani and Pedrosa, which leads to highly accurate zeroth-order perturbation solutions in radial flow problems, does not yield an accurate result for one-dimensional flow. Article Highlights Approximate solution for flow to a constant-pressure boundary in a porous medium whose permeability varies exponentially with pressure. The predicted flowrate is accurate to within 5% for a wide range of permeability variations. If permeability at boundary is 30% less than initial permeability, flowrate will be 10% less than predicted by constant-permeability model.

Catalysis by hydrogen halides in the gas phase. XIX. 2,3-Dimethylbutan-2-ol and hydrogen bromide

1968 ◽  
Vol 21 (10) ◽  
pp. 2385 ◽  
Author(s):  
RL Johnson ◽  
VR Stimson
Keyword(s):  
Gas Phase ◽  
Arrhenius Equation ◽  
Hydrogen Bromide ◽  
Phase Decomposition ◽  
Hydrogen Halides ◽  
First Order

The gas-phase decomposition of 2,3-dimethylbutan-2-ol into 2,3-dimethylbut-1-ene, 2,3-dimethylbut-2-ene, and water, catalysed by hydrogen bromide at 303-400�, is described. The rate is first-order in each reactant and the Arrhenius equation k2 = 1011.88 exp(-26490/RT) sec-l ml mole-1 is followed. The olefins appear to be in their equilibrium proportions. The effects of substitutions in the alcohol at Cα and Cβ on the rate are discussed.

scholarly journals Rapid compressions in a captive bubble apparatus are isothermal

2003 ◽  
Vol 95 (5) ◽  
pp. 1896-1900
Author(s):  
Wenfei Yan ◽  
Stephen B. Hall
Keyword(s):  
Hydrostatic Pressure ◽  
Gas Phase ◽  
Pulmonary Surfactant ◽  
First Order ◽  
First Order Kinetics ◽  
Gas Phase Molecules ◽  
Actual Change ◽  
Phase Temperature ◽  
Two Phases ◽  
Interfacial Films

Captive bubbles are commonly used to determine how interfacial films of pulmonary surfactant respond to changes in surface area, achieved by varying hydrostatic pressure. Although assumed to be isothermal, the gas phase temperature (Tg) would increase by >100°C during compression from 1 to 3 atm if the process were adiabatic. To determine the actual change in temperature, we monitored pressure (P) and volume (V) during compressions lasting <1 s for bubbles with and without interfacial films and used P · V to evaluate Tg. P · V fell during and after the rapid compressions, consistent with reductions in n, the moles of gas phase molecules, because of increasing solubility in the subphase at higher P. As expected for a process with first-order kinetics, during 1 h after the rapid compression P · V decreased along a simple exponential curve. The temporal variation of n moles of gas was determined from P · V >10 min after the compression when the two phases should be isothermal. Back extrapolation of n then allowed calculation of Tg from P · V immediately after the compression. Our results indicate that for bubbles with or without interfacial films compressed to >3 atm within 1 s, the change in Tg is <2°C.

POLYMÉRISATION PAR LES RAYONS-X DU CHLORURE DE VINYLE À L'ÉTAT DE VAPEUR

1963 ◽  
Vol 41 (6) ◽  
pp. 1578-1587 ◽  
Author(s):  
Jan A. Herman ◽  
Pierre M. Hupin
Keyword(s):  
Activation Energy ◽  
Gas Phase ◽  
Average Molecular Weight ◽  
Negative Temperature ◽  
Solid Polymer ◽  
X Rays ◽  
Kcal Mole ◽  
Rate Of Polymerization ◽  
G Value ◽  
Termination Process

The polymerization of vinyl chloride in the gas phase by X rays gives a solid polymer of 1140 average molecular weight. The G value of monomer disappearance varies from 100 to 400 and depends on pressure and temperature. From the measure of the rate of polymerization it was possible to deduce the activation energy of the chain propagation steps: 2.5 kcal/mole, and that of the hindered termination process: 7.4 kcal/mole. The negative temperature co-efficient of the polymerization is explained by the importance of this hindered termination process.

The thermal decompositions of carbamates. I. Ethyl N-Methyl-N-phenylcarbamate

1971 ◽  
Vol 24 (12) ◽  
pp. 2541 ◽  
Author(s):  
NJ Daly ◽  
F Ziolkowski
Keyword(s):  
Carbon Dioxide ◽  
Gas Phase ◽  
Rate Constants ◽  
Volume Ratio ◽  
Reaction Vessel ◽  
First Order ◽  
Order Rate

Ethyl N-methyl-N-phenylcarbamate decomposes in the gas phase over the range 329-380� to give N-methylaniline, carbon dioxide, and ethylene. The reaction is quantitative, and is first order in the carbamate. First-order rate constants are described by the equation ������������������� k1 = 1012.44 exp(-45,380/RT) (s-1) and are unaffected by the addition of cyclohexene or by increase in the surface to volume ratio of the reaction vessel. The reaction is considered to be unimolecular and likely to proceed by means of a mechanism of the type represented by the pyrolyses of acetates, xanthates, and carbonates.

Kinetics of NO2 air space absorption in isolated rat lungs

1992 ◽  
Vol 73 (5) ◽  
pp. 1939-1945 ◽  
Author(s):  
E. M. Postlethwait ◽  
S. D. Langford ◽  
A. Bidani
Keyword(s):  
Steady State ◽  
Tidal Volume ◽  
Gas Phase ◽  
Initial Rate ◽  
Quasi Steady State ◽  
Closed Chamber ◽  
First Order ◽  
First Order Kinetics ◽  
Rat Lungs ◽  
Kinetics Of

We previously showed, during quasi-steady-state exposures, that the rate of inhaled NO2 uptake displays reaction-mediated characteristics (J. Appl. Physiol. 68: 594–603, 1990). In vitro kinetic studies of pulmonary epithelial lining fluid (ELF) demonstrated that NO2 interfacial transfer into ELF exhibits first-order kinetics with respect to NO2, attains [NO2]-dependent rate saturation, and is aqueous substrate dependent (J. Appl. Physiol. 71: 1502–1510, 1991). We have extended these observations by evaluating the kinetics of NO2 gas phase disappearance in isolated ventilating rat lungs. Transient exposures (2–3/lung at 25 degrees C) employed rebreathing (NO2-air) from a non-compliant continuously stirred closed chamber. We observed that 1) NO2 uptake rate is independent of exposure period, 2) NO2 gas phase disappearance exhibited first-order kinetics [initial rate (r*) saturation occurred when [NO2] > 11 ppm], 3) the mean effective rate constant (k*) for NO2 gas phase disappearance ([NO2] < or = 11 ppm, tidal volume = 2.3 ml, functional residual capacity = 4 ml, ventilation frequency = 50/min) was 83 +/- 5 ml/min, 4) with [NO2] < or = 11 ppm, k* and r* were proportional to tidal volume, and 5) NO2 fractional uptakes were constant across [NO2] (< or = 11 ppm) and tidal volumes but exceeded quasi-steady-state observations. Preliminary data indicate that this divergence may be related to the inspired PCO2. These results suggest that NO2 reactive uptake within rebreathing isolated lungs follows first-order kinetics and displays initial rate saturation, similar to isolated ELF.(ABSTRACT TRUNCATED AT 250 WORDS)

The Role of Starting Potential in the Kinetics of Chemical Reactions under Electrodeless Discharge

1970 ◽  
Vol 25 (11) ◽  
pp. 1772
Author(s):  
T.S.R Ao ◽  
A. Patil
Keyword(s):  
Gas Phase ◽  
Chemical Reactions ◽  
Electric Discharge ◽  
Specific Rate ◽  
Gas Phase Reactions ◽  
Electrodeless Discharge ◽  
First Order ◽  
Kinetics Of

Abstract It has been shown that in kinetically first order gas phase reactions occuring under electric discharge, such as the decomposition of N2O, the application, at various initial pressures, of the same multiple of the respective starting potential ensures that the reaction occurs at the same specific rate.

The Near-ultraviolet Absorption Spectrum of Diimide in Liquid Ammonia and its Decomposition between −65 and −38 °C

1974 ◽  
Vol 52 (13) ◽  
pp. 2513-2515 ◽  
Author(s):  
R. A. Back ◽  
C. Willis
Keyword(s):  
Absorption Spectrum ◽  
Gas Phase ◽  
Room Temperature ◽  
Liquid Ammonia ◽  
Vibrational Structure ◽  
Ultraviolet Absorption ◽  
Ultraviolet Absorption Spectrum ◽  
First Order ◽  
Rapid Decomposition ◽  
Near Ultraviolet

The near-ultraviolet absorption spectrum of diimide in liquid ammonia at −50 °C is shifted about 500 Å to the red compared with the gas-phase spectrum, with λmax = 4000 Å. The spectrum is also broadened and the vibrational structure largely obscured. It is suggested that hydrogen bonding is responsible for these changes.Diimide is much more stable in liquid ammonia between −65 and −38 °C than in the gas phase at room temperature. A first-order decay is observed with Arrhenius parameters of A = 1.9 × 103 s−1 and E = 6.6 kcal/mol; this is always preceded by a more rapid, higher-order initial decay which may be related to the rapid decomposition observed during vaporization.

The gas-phase photochemistry and thermal decomposition of glyoxylic acid

1985 ◽  
Vol 63 (2) ◽  
pp. 542-548 ◽  
Author(s):  
R. A. Back ◽  
S. Yamamoto
Keyword(s):  
Thermal Decomposition ◽  
Carbon Monoxide ◽  
Absorption Spectrum ◽  
Gas Phase ◽  
Singlet State ◽  
Glyoxylic Acid ◽  
Static System ◽  
First Order ◽  
Increasing Temperature ◽  
Homogeneous Formation

The photolysis of glyoxylic acid vapour has been studied at five wavelengths, 382, 366, 346, 275, and 239 nm, and pressures from about 1 to 6 Torr, at a temperature of 355 K. Major products were CO2 and CH2O, initially formed in almost equal amounts, while minor products were CO and H2. Except at 382 nm, the system was complicated by the rapid secondary photolysis of CH2O. Three primary processes are suggested, each involving internal H-atom transfer followed by dissociation.The absorption spectrum is reported and shows the three distinct absorption systems. A finely-structured spectrum from about 320 to 400 nm is attributed to a transition to the first excited π* ← n+ singlet state; a more diffuse absorption ranging from about 290 nm to a maximum at 239 nm is assigned to the π* ← n− state, while a much stronger absorption beginning below 230 nm is attributed to the π* ← π transition. Product ratios vary with wavelength and depend on which excited state is involved.The thermal decomposition was studied briefly in a static system at temperatures from 470 to 710 K and pressures from 0.4 to 8 Torr. Major products were again CO2 and CH2O, but the latter was always less than stoichiometric. First-order rate constants for the apparently homogeneous formation of CO2 are described by Arrhenius parameters log A (s−1) = 7.80 and E = 30.8 kcal/mol. Carbon monoxide and H2 were minor products, and the CO/CO2 ratio increased with increasing temperature and showed some surface enhancement at lower temperatures. The SF6-sensitized thermal decomposition of glyoxylic acid, induced by a pulsed CO2 laser, was briefly studied, with temperatures estimated to be in the 1100–1600 K range, and the CO/CO2 ratio increased with increasing temperature, continuing the trend observed in the static system.

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