KINETIC STUDY OF THE ISOMERIZATION OF n-BUTENES ON CHROMIA–ALUMINA

1962 ◽  
Vol 40 (11) ◽  
pp. 2130-2139 ◽  
Author(s):  
Y. Amenomiya ◽  
R. J. Cvetanović
Keyword(s):  
Kinetic Study ◽  
Rate Equation ◽  
Pressure Range ◽  
Experimental Results ◽  
Alumina Catalyst ◽  
Adsorbed Species ◽  
Temperature Range ◽  
Rate Determining Step

Mutual interconversions of the three n-butenes on a chromia–alumina catalyst have been studied in a temperature range between 210 and 260 °C and in a pressure range from about 10 to about 100 mm. Dependence of initial rates on the initial pressures of the reactants was determined experimentally. The initial rates of isomerization could be, in each case, expressed empirically by a rate equation conforming to the Langmuir–Hinshelwood formula. It was possible to explain the experimental results by assuming the existence of three different adsorbed species for the three n-butene isomers and their surface interconversions as the rate-determining step.

Kinetic Study of the Pyrolysis of Formaldehyde

1972 ◽  
Vol 50 (7) ◽  
pp. 992-998 ◽  
Author(s):  
C. J. Chen ◽  
D. J. McKenney
Keyword(s):  
Activation Energy ◽  
Thermal Decomposition ◽  
Carbon Monoxide ◽  
Kinetic Study ◽  
Pressure Range ◽  
Heterogeneous Reaction ◽  
Experimental Results ◽  
Arrhenius Parameters ◽  
Rate Laws ◽  
Kinetics Of

Kinetics of the thermal decomposition of pure formaldehyde were studied over a temperature range of 466–516 °C and a pressure range of ~ 50–160 Torr. Arrhenius parameters and rate laws were determined for carbon monoxide, hydrogen and methanol as follows:[Formula: see text]A mechanism is postulated which is qualitatively consistent with the experimental results but the activation energy for reaction 1[Formula: see text]is ~15 kcal/mol lower than predicted from recent thermochemical data, suggesting the possibility of a heterogeneous reaction.

scholarly journals Über die Kinetik der Wasserstoffpermeation durch Nickel

1967 ◽  
Vol 22 (10) ◽  
pp. 1581-1586 ◽  
Author(s):  
W. Fischer
Keyword(s):  
Steady State ◽  
Time Lag ◽  
Permeation Rate ◽  
Experimental Results ◽  
Nickel Surface ◽  
Temperature Range ◽  
Rate Determining Step ◽  
Stationary Conditions ◽  
Limits Of Error ◽  
Diffusion Of Hydrogen

The permeation rate of hydrogen through nickel foils of various thicknesses (6,7 μ≦ d≦ 1,83 mm) has been measured in the temperature range 423°K ≦ T ≦ 1000°K. The permeation rate P [Mol H2· cm-1·s-1] under stationary conditions is inversely proportional to the thickness of the foil over the whole temperature range. The experimental results are fitted by the relationP= (7,22·10-7/d) · exp (-52 400/RT).Diffusion contants D [cm2· s -1] have been determined by means of the time lag method and have been calculated from steady state permeation rates and from hydrogen solubility data. The results are in accordance within the limits of error.It is concluded that the rate determining step for the permeation is diffusion of hydrogen in nickel. Surface reactions are very fast.

The Chemistry of Vulcanization. VIII. Role of Zinc Butyrate in the Reaction of Diphenylmethane, Sulfur and 2-Benzothiazolyl Disulfide

1961 ◽  
Vol 34 (2) ◽  
pp. 648-657
Author(s):  
Haruko Fukuda ◽  
Jitsuo Tsurugi
Keyword(s):  
Zinc Oxide ◽  
Reaction Mechanism ◽  
Butyric Acid ◽  
Rate Equation ◽  
Experimental Results ◽  
Zinc Salt ◽  
Elementary Sulfur ◽  
Rate Determining Step

Abstract Diphenylmethane (DPM) which contains α-methylenic hydrogen has been used as a model of rubber hydrocarbon, and reactions involving DPM, sulfur and thiazole type accelerators in the absence of zinc oxide or soap were reported in previous papers. These papers reported that 2-mercaptobenzothiazole (MBT), 2-benzothiazolyl disulfide (MBTS) and zinc salt of 2-mercaptobenzothiazole (ZMBT) generate the same radical, i.e., 2-benzothiazolesulfenyl which has the accelerating effect. This radical opens the ring of elementary sulfur and thus accelerates vulcanization since the spontaneous splitting of the sulfur ring molecule to a biradical was found to be the rate determining step in the reaction of DPM with sulfur alone. Processes by which accelerators generate this radical differ from each other owing to the types of accelerators, that is, mercaptan, disulfide and zinc mercaptide type. The previous paper reported the reaction involving DPM, sulfur and MBT in the presence of zinc butyrate. According to this, MBT first reacts with zinc butyrate to form butyric acid and ZMBT, the latter then generating the effective benzothiazole-sulfenyl radical. Thus, even in the presence of zinc soap, the essential mechanism of acceleration is the same as in the absence of zinc soap, though the process and rate for forming benzothiazolesulfenyl radical are different in the absence of zinc soap. In the present paper the reaction of DPM, sulfur and MBTS in the presence of zinc butyrate are reported. The reaction mechanism will be deduced from the experimental results obtained here and from conclusions obtained in the previous papers. The rate equation for MBTS consumption and equation for the accelerating efficiency for this accelerator are derived from the mechanism. The theoretical equations were examined by experiments.

The pyrolysis of monosilane

1966 ◽  
Vol 293 (1435) ◽  
pp. 543-561 ◽  
Keyword(s):  
Thermal Decomposition ◽  
Kinetic Study ◽  
Pressure Range ◽  
Initial Pressure ◽  
Product Formation ◽  
Reaction Vessel ◽  
Silicon Hydride ◽  
Temperature Range ◽  
Gaseous Products ◽  
Kinetic Features

A detailed analytical and kinetic study of the thermal decomposition of monosilane in the temperature range 375 to 430 °C and the initial pressure range 35 to 230 mmHg has been conducted. The gaseous products in the very early stages of the reaction are hydrogen, disilane and trisilane. In addition, later in the reaction a solid silicon hydride is formed, its composition varying as the reaction progresses. The kinetic features of product formation during the first 3 % of decomposition have been studied in detail, while those relating to higher extents of decomposition have been investigated less fully. The reaction is accelerated by the addition of certain foreign gases, but is unaffected by packing of the reaction vessel. A tentative mechanism involving the species silene, SiH 2 , is proposed.

Dynamic Viscosity of Compressed Water to 10 Kilobar and Steam to 1500°C

1969 ◽  
Vol 11 (2) ◽  
pp. 189-205 ◽  
Author(s):  
E. A. Bruges ◽  
M. R. Gibson
Keyword(s):  
Gaseous Phase ◽  
Dynamic Viscosity ◽  
Low Temperatures ◽  
Pressure Range ◽  
Low Pressure ◽  
Temperature Range ◽  
Inversion Temperature ◽  
Pressure Steam ◽  
Correlating Equations ◽  
First Time

Equations specifying the dynamic viscosity of compressed water and steam are presented. In the temperature range 0-100cC the location of the inversion locus (mu) is defined for the first time with some precision. The low pressure steam results are re-correlated and a higher inversion temperature is indicated than that previously accepted. From 100 to 600°C values of viscosity are derived up to 3·5 kilobar and between 600 and 1500°C up to 1 kilobar. All the original observations in the gaseous phase have been corrected to a consistent set of densities and deviation plots for all the new correlations are given. Although the equations give values within the tolerances of the International Skeleton Table it is clear that the range and tolerances of the latter could with some advantage be revised to give twice the existing temperature range and over 10 times the existing pressure range at low temperatures. A list of the observations used and their deviations from the correlating equations is available as a separate publication.

scholarly journals A Digital Improvement—Trimming a Digital Temperature Sensor with EEPROM Reprogrammable Fuses

Sensors ◽  
2021 ◽  
Vol 21 (5) ◽  
pp. 1700
Author(s):  
Anca Mihaela Vasile (Dragan) ◽  
Alina Negut ◽  
Adrian Tache ◽  
Gheorghe Brezeanu
Keyword(s):  
Standard Deviation ◽  
Power Supply ◽  
Temperature Sensor ◽  
Experimental Results ◽  
Temperature Error ◽  
Thermal Sensor ◽  
Memory Cells ◽  
Temperature Range ◽  
Read Only Memory ◽  
Digital Temperature Sensor

An EEPROM (electrically erasable programmable read-only memory) reprogrammable fuse for trimming a digital temperature sensor is designed in a 0.18-µm CMOS EEPROM. The fuse uses EEPROM memory cells, which allow multiple programming cycles by modifying the stored data on the digital trim codes applied to the thermal sensor. By reprogramming the fuse, the temperature sensor can be adjusted with an increased trim variation in order to achieve higher accuracy. Experimental results for the trimmed digital sensor showed a +1.5/−1.0 ℃ inaccuracy in the temperature range of −20 to 125 ℃ for 25 trimmed DTS samples at 1.8 V by one-point calibration. Furthermore, an average mean of 0.40 ℃ and a standard deviation of 0.70 ℃ temperature error were obtained in the same temperature range for power supply voltages from 1.7 to 1.9 V. Thus, the digital sensor exhibits similar performances for the entire power supply range of 1.7 to 3.6 V.

An Ultrafast Vitrification Method for Cell Cryopreservation

2017 ◽  
Vol 140 (1) ◽  
Author(s):  
Fengmin Su ◽  
Nannan Zhao ◽  
Yangbo Deng ◽  
Hongbin Ma
Keyword(s):  
Thin Film ◽  
Cooling Rate ◽  
Experimental Results ◽  
Low Concentration ◽  
Temperature Range ◽  
Thin Film Evaporation ◽  
Film Evaporation ◽  
A Cell ◽  
Cryoprotective Solution ◽  
Ultrafast Cooling

Ultrafast cooling is the key to successful cell vitrification cryopreservation of lower concentration cryoprotective solution. This research develops a cell cryopreservation methodology which utilizes thin film evaporation and achieves vitrification of relatively low concentration cryoprotectant with an ultrafast cooling rate. Experimental results show that the average cooling rate of dimethylsulfoxide (DMSO) cryoprotective solution reaches 150,000 °C/min in a temperature range from 10 °C to −180 °C. The ultrafast cooling rate can remarkably improve the vitrification tendencies of the cryoprotective solution. This methodology opens the possibility for more successful cell vitrification cryopreservation.

Experimental evidence for the need of thermodynamic considerations in modelling of anaerobic environmental bioprocesses

1997 ◽  
Vol 36 (10) ◽  
pp. 109-115 ◽  
Author(s):  
Choon-Yee Hoh ◽  
Ralf Cord-Ruwisch
Keyword(s):  
Free Energy ◽  
Experimental Evidence ◽  
Positive Reaction ◽  
Rate Equation ◽  
Dynamic Equilibrium ◽  
Reaction Rates ◽  
Product Inhibition ◽  
Experimental Results ◽  
Biological Processes ◽  
Laws Of Thermodynamics

For modeling of biological processes that operate close to the dynamic equilibrium (eg. anaerobic processes), it is critical to prevent the prediction of positive reaction rates when the reaction has already reached dynamic equilibrium. Traditional Michaelis-Menten based models were found to violate the laws of thermodynamics as they predicted positive reaction rates for reactions that were endergonic due to high endproduct concentrations. The inclusion of empirical “product inhibition factors” as suggested by previous work could not prevent this problem. This paper compares the predictions of the Michaelis-Menten Model (with and without product inhibition factors) and the Equilibrium Based Model (which has a thermodynamic term introduced into its rate equation) with experimental results of reactions in anaerobic bacterial environments. In contrast to the Michaelis-Menten based models that used traditional inhibition factors, the Equilibrium Based Model correctly predicted the nature and the degree of inhibition due to endproduct accumulation. Moreover, this model also correctly predicted when reaction rates must be zero due to the free energy change of the conversion reaction being zero. With these added advantages, the Equilibrium Based Model thus seemed to provide a scientifically correct and more realistic basis for a variety of models that describe anaerobic biosystems.

An anomaly in the specific heat below 3 °K of copper containing hydrogen

1969 ◽  
Vol 47 (14) ◽  
pp. 1485-1491 ◽  
Author(s):  
Neil Waterhouse
Keyword(s):  
Specific Heat ◽  
Molecular Hydrogen ◽  
Pure Copper ◽  
Solid Hydrogen ◽  
Rotational State ◽  
Experimental Results ◽  
Ortho Hydrogen ◽  
Temperature Range ◽  
A Value ◽  
Heat Curve

The specific heat of copper heated in hydrogen at 1040 °C has been measured over the temperature range 0.4 to 3.0 °K and found to be anomalous. The anomaly occurs in the same temperature range as the solid hydrogen λ anomaly which, in conjunction with evidence of ortho to para conversion of hydrogen in the sample, suggests the presence of molecular hydrogen in the copper. The anomaly reported by Martin for "as-received" American Smelting and Refining Company (ASARCO) 99.999+ % pure copper has been briefly compared with the present results. The form of the anomaly produced by the copper-hydrogen specimen has been compared with Schottky curves using the simplest possible model, that for two level splitting of the degenerate J = 1 rotational state of the ortho-hydrogen molecule.Maintenance of the copper-hydrogen sample at ~20 °K for approximately 1 week removed the "hump" in the specific heat curve. An equation of the form Cp = γT + (464.34/(θ0c)3)T3 was found to fit these experimental results and produced a value for γ which had increased over that for vacuumannealed pure copper by ~2%.

Sign in / Sign up

Export Citation Format

Share Document