Polymerization Reactions under high Pressure. I. Some Experiments with Isoprene and Butyraldehyde

1930 ◽  
Vol 3 (3) ◽  
pp. 472-482
Author(s):  
J. B. Conant ◽  
C. O. Tongberg
Keyword(s):  
High Pressure ◽  
Room Temperature ◽  
High Pressures ◽  
Order Reaction ◽  
Pressure Coefficients ◽  
First Order ◽  
Rate Of Polymerization ◽  
Energy Relationships ◽  
Temperature And Pressure ◽  
Autocatalytic Effect

Abstract 1. The rate of polymerization of isoprene under high pressures has been studied. The reaction is subject to positive catalysis by peroxides and negative catalysis by hydroquinone. Although the reaction is of a high order, the rate is approximately in accord with a first order reaction presumably because of an autocatalytic effect. The temperature and pressure coefficients of the rate have been estimated. The solubility and elasticity of the product depend on the extent to which the isoprene has been polymerized; when the polymerization is practically complete at room temperature at 12,000 atm. the product is very insoluble 2. The action of high pressures on n-butyraldehyde produces a solid only slightly soluble in organic solvents. It reverts to n-butyraldehyde rapidly. It is suggested that this polymer is similar to the well-known polymers of formaldehyde but that the energy relationships are such that the polymer is stable only at high pressures.

THE KINETICS OF THE DECOMPOSITION REACTIONS OF THE LOWER PARAFFINS: I. n-BUTANE

1938 ◽  
Vol 16b (5) ◽  
pp. 176-193 ◽  
Author(s):  
E. W. R. Steacie ◽  
I. E. Puddington
Keyword(s):  
Reaction Rate ◽  
High Pressures ◽  
The Other ◽  
First Order ◽  
Decomposition Reactions ◽  
Temperature And Pressure ◽  
Products Of Reaction ◽  
Kinetics Of ◽  
Good Agreement ◽  
Mechanism Of The Reaction

The kinetics of the thermal decomposition of n-butane has been investigated at pressures from 5 to 60 cm. and temperatures from 513 to 572 °C. The initial first order rate constants at high pressures are given by[Formula: see text]The results are in good agreement with the work of Frey and Hepp, but differ greatly from that of Paul and Marek. The reaction rate falls off strongly with diminishing pressure; this is rather surprising for a molecule as complex as butane. The first order constants in a given run fall rapidly as the reaction progresses. The last two facts suggest that chain processes may be involved.A large number of analyses of the products of reaction have been made at various pressures, temperatures, and stages of the reaction, the method being that of low-temperature fractional distillation. The products are virtually independent of temperature and pressure over the range investigated. The initial products, obtained by extrapolation to zero decomposition, are:—H2, 2.9; CH4, 33.9; C3H6, 33.9; C2H4, 15.2; C2H6, 14.1%. The mechanism of the reaction is discussed, and the results are compared with those of the other paraffin decompositions.

The formation of O2(a1Δg) in homogeneous and heterogeneous atom recombination

1986 ◽  
Vol 64 (12) ◽  
pp. 1614-1620 ◽  
Author(s):  
A. A. Ali ◽  
E. A. Ogryzlo ◽  
Y. Q. Shen ◽  
P. T. Wassell
Keyword(s):  
Kinetic Study ◽  
Gas Phase ◽  
Molecular Oxygen ◽  
Rate Constant ◽  
Room Temperature ◽  
High Efficiency ◽  
Flow System ◽  
Order Reaction ◽  
Third Order ◽  
First Order

The recombination of oxygen atoms has been studied in a discharge flow system at room temperature. The yield of O2(a1Δg) in the recombination on Pyrex has been found to be 0.08 (±0.02). In the gas phase, O2(a) was found to be formed in a process that is second order in [O] and first order in [N2]. The rate constant for this third-order reaction was found to be 3.4 (±0.4) × 10−34 cm6∙molecule−2∙s−1, representing a yield of 0.07 (±0.02). In the presence of molecular oxygen, the rate of production of O2(a) was found to increase. A kinetic study of this effect led to the conclusion that collisions of molecular oxygen with an unidentified precursor can produce O2(a) with high efficiency.

HYDROLYSIS AND POLYMERIZATION OF CYCLIC DIMETHYLETHYLENE OXALATES

1951 ◽  
Vol 29 (11) ◽  
pp. 970-973 ◽  
Author(s):  
L. G. Ripley ◽  
R. W. Watson
Keyword(s):  
Elevated Temperature ◽  
Optical Activity ◽  
Vacuum Distillation ◽  
Room Temperature ◽  
Order Reaction ◽  
Membered Ring ◽  
Melting Points ◽  
Monobasic Acid ◽  
First Order ◽  
Marked Stability

Macrocrystalline cyclic oxalates (2,3-dimethyl-5-6-p-dioxanediones) were prepared by vacuum distillation of the polymeric mixture formed on heating ethyl oxalate, and 1, 2-dimethylethylene glycol with an ester-interchange catalyst. Monomeric dimethylethylene oxalate polymerizes less readily than propylene oxalate, and only at an elevated temperature in the presence of a catalyst. Dimethyl substitution therefore confers marked stability on the six-membered ring. Hydrolysis reaches 50% completion almost instantaneously, followed by a slow first order reaction resulting in complete cleavage of the monobasic acid in about one month at room temperature. Hydrolysis constants for the levo- and meso- oxalates are 0.069 and 0.076 days−1 respectively. The crystalline monomers do not possess sharp melting points and represent stereoisomeric mixtures which display optical activity in solution.

Die Kinetik des Zerfalls von tert. Butylperoxypivalat bei hohen Drücken und Temperaturen / The Kinetics of the Decomposition of tert.Butylperoxypivalate up to High Pressures and Temperatures

1981 ◽  
Vol 36 (12) ◽  
pp. 1371-1377 ◽  
Author(s):  
M. Buback ◽  
H. Lendle
Keyword(s):  
Activation Energy ◽  
High Pressure ◽  
High Pressures ◽  
Activation Volume ◽  
Rate Law ◽  
First Order ◽  
Order Rate ◽  
High Pressures And Temperatures ◽  
Kinetics Of

AbstractThe decomposition of tert. butylperoxypivalate dissolved in n-heptane has been measured ir-spectroscopically in optical high-pressure cells up to 2000 bar at temperatures between 65 °C and 105 °C. The reaction follows a first order rate law with an activation energy Ea = 122.3 ±3.0 kJ · mol-1 and an activation volume ⊿V≠ = 1.6 ± 1.0 cm3 mol-1 .

Influence of the molecular structures on the high-pressure and low-temperature phase transitions of plastic crystals

2003 ◽  
Vol 59 (1) ◽  
pp. 60-71 ◽  
Author(s):  
Markus Wunschel ◽  
Robert E. Dinnebier ◽  
Stefan Carlson ◽  
Piotr Bernatowicz ◽  
Sander van Smaalen
Keyword(s):  
High Pressure ◽  
Phase Transitions ◽  
Low Temperature ◽  
Room Temperature ◽  
Close Packing ◽  
Molecular Structures ◽  
Temperature Phase ◽  
Plastic Crystals ◽  
First Order ◽  
First Order Phase

The crystal structures of tert-butyl-tris(trimethylsilyl)silane, Si[C(CH_3)_3]_1[Si(CH_3)_3]_3 (Bu1), and di-tert-butyl-bis(trimethylsilyl)silane, Si[C(CH_3)_3]_2[Si(CH_3)_3]_2 (Bu2), at room temperature and at 105 K have been determined by X-ray powder diffraction; the high-pressure behavior for pressures between 0 and 5 GPa is reported. The room-temperature structures have cubic Fm\bar{3}m symmetry (Z = 4) with a = 13.2645 (2) Å, V = 2333.87 (4) Å3 for Bu1 and a = 12.9673 (1) Å, V = 2180.46 (3) Å3 for Bu2. The molecules are arranged in a cubic close packing (c.c.p.) and exhibit at least 48-fold orientational disorder. Upon cooling both compounds undergo a first-order phase transition at temperatures T_c = 230 (5) K (Bu1) and T_c = 250 (5) K (Bu2) into monoclinic structures with space group P2_1/n. The structures at 105 K have a = 17.317 (1), b = 15.598 (1), c = 16.385 (1) Å, \gamma = 109.477 (4)°, V = 4172.7 (8) Å3 and Z = 8 for Bu1and a = 17.0089 (9), b = 15.3159 (8), c = 15.9325 (8) Å, \gamma = 110.343 (3)°, V = 3891.7 (5) Å3 and Z = 8 for Bu2. The severe disorder of the room-temperature phase is significantly decreased and only a two- or threefold rotational disorder of the molecules remains at 105 K. First-order phase transitions have been observed at pressures of 0.13–0.28 GPa for Bu1 and 0.20–0.24 GPa for Bu2. The high-pressure structures are isostructural to the low-temperature structures. The pressure dependencies of the unit-cell volumes were fitted with Vinet equations of state and the bulk moduli were obtained. At still higher pressures further anomalies in the pressure dependencies of the lattice parameters were observed. These anomalies are explained as additional disorder–order phase transitions.

Studies of the Vulcanization of High Elastic Polymers. V. Vulcanization of Natural Rubber by Tetramethylthiuram Monosulfide and Sulfur

1956 ◽  
Vol 29 (1) ◽  
pp. 48-62 ◽  
Author(s):  
Walter Scheele ◽  
Georg Bielstein
Keyword(s):  
Natural Rubber ◽  
Temperature Dependence ◽  
Order Reaction ◽  
Experimental Results ◽  
First Order Reaction ◽  
First Order ◽  
Temperature Range ◽  
Quantitative Formation ◽  
Energy Relationships

Abstract The vulcanization of natural rubber (pale crepe) by tetramethylthiuram monosulfide and sulfur (1 mole monosulfide per gram-atom of sulfur) has been studied in the temperature range from 90° to 150° C. The following results were obtained : 1. During vulcanization, the concentration of the thiuram monosulfide and also of the sulfur decreases. 2. In accordance with a first-order reaction, about 66 mole-per cent of zinc dithiocarbamate is formed (calculated on the amount of thiuram monosulfide added). Thus the same relationships were found as in vulcanization with thiuram disulfides. 3. The vulcanization of rubber with thiuram monosulfide and sulfur is, therefore, nothing else than vulcanization by thiuram disulfide, whose quantitative formation precedes the actual vulcanization reaction. 4. In no stage of vulcanization could thiuram disulfide be detected with certainty in the extracts of the vulcanizates. It must be assumed, therefore, that it reacts with the rubber instantly after it is formed. 5. The velocity constants derived for the dithiocarbamate formation at the various temperatures both from the experimental results and from the graphical presentations have been given, and their temperature dependence has been discussed. At lower temperatures, the influence of the prior interaction of the monosulfide with sulfur makes its influence on the energy relationships felt. 6. It is once more emphasized that in thiuram vulcanization it cannot be a question of a vulcanization with sulfur. In this connection we take a decided stand also with regard to the results of the more recent investigations of Craig and his coworkers.

Mechanism of Modified Sponge Iron Deoxygenization and its Application for High Pressure Boiler Feed Water

2012 ◽  
Vol 538-541 ◽  
pp. 2215-2219
Author(s):  
Bo Xu ◽  
Ming Chun Jia ◽  
Jin Feng Men
Keyword(s):  
High Pressure ◽  
Active Sites ◽  
Exchange Resin ◽  
Ion Exchange Resin ◽  
Order Reaction ◽  
Sponge Iron ◽  
Feed Water ◽  
First Order ◽  
Dissolved Iron ◽  
Boiler Feed Water

To promote the deoxygenization efficiency of modified sponge iron deaerator, the deoxygenization mechanism was studied with the aid of kinetics and characterized analysis. The application of modified sponge iron deaerator for high pressure boiler feed water was investigated as well. The results showed that the process of deoxygenization was a first order reaction regarding for active sites decay. The modified sponge iron was able to reduce dissolved oxygen (DO) level from ppm levels down to a few ppb levels and the dissolved iron in outlet can be removed completely by ion exchange resin. Therefore, the application of modified sponge iron deaerator for high pressure boiler feed water was feasible.

Safe and Reliable Temperature and Pressure Measurement for High Pressure Applications

2019 ◽  
Author(s):  
Tony Maupin ◽  
Jennifer Breunig
Keyword(s):  
High Pressure ◽  
Pressure Measurement ◽  
High Pressures ◽  
Fast Response ◽  
Vacuum Brazing ◽  
High Pressure Polyethylene ◽  
Challenging Environment ◽  
Production Techniques ◽  
Temperature And Pressure ◽  
Reliable Temperature

Abstract For high pressure polyethylene applications, reliable temperature and pressure measurement with extremely fast response time, is crucial in order to avoid decomposition. Furthermore instrumentation must withstand not only the high pressures and temperatures, but also the vibration present in such a challenging environment. The requirements of temperature and pressure instrumentation include high quality mineral insulated cable, production techniques such as vacuum brazing and thin film sputtering as well as testing facilities. With this information, operators will be able to select high pressure thermocouples and pressure transmitters which are specifically designed for their application.

scholarly journals Twinning and Pseudosymmetry at High Pressures

2014 ◽  
Vol 70 (a1) ◽  
pp. C260-C260 ◽  
Author(s):  
Karen Friese ◽  
Andrzej Grzechnik
Keyword(s):  
High Pressure ◽  
Phase Transitions ◽  
Single Crystal ◽  
High Pressures ◽  
Rotational Symmetry ◽  
Type I ◽  
Experimental Conditions ◽  
First Order ◽  
Volume Fractions ◽  
First Order Phase

Twinning is a common known problem in the study of crystal structures from single-crystal data and often related to a high degree of pseudosymmetry of the structure with respect to a higher symmetrical parent one. With the rising popularity of in situ single-crystal diffraction studies under high pressure, the occurrence of twinned structures is more and more frequently reported. In this contribution, we review the available information on merohedral and pseudomerohedral twinning as well as pseudosymmetry under high pressures [1]. For twinning by merohedry type I (inversion twinning), a reliable characterization of the twin domains and volume fractions is difficult and largely depends on the experimental conditions, i.e., on the number of measured Friedel pairs and the chosen wavelength. For twinning by merohedry (type II) and for twinning by pseudomerohedry, twin volume fractions could be reliably determined from high-pressure data for several cases. In none of these, a significant influence of hydrostatic pressure on the volume fractions of the individuals was observed. Pressure-induced twinning has also been observed for compounds which undergo first-order phase transitions. It is remarkable that the twinning operation in such cases is related to the loss of rotational symmetry elements of the higher symmetrical polymorph, although the high- and low-pressure phases are not in the group-subgroup relationship. The analysis of pseudosymmetry of several compounds as a function of pressure suggests that this parameter can be used to predict the (in)stability of compounds. In particular, a decrease in pseudosymmetry seems to be strongly correlated with the occurrence of first-order phase transitions in which the crystals break or amorphize.

Sign in / Sign up

Export Citation Format

Share Document