GAS-Phase Decomposition Kinetics of MOVPE Precursors in a Counterflow Jet Reactor

MRS Proceedings ◽

10.1557/proc-282-157 ◽

1992 ◽

Vol 282 ◽

Cited By ~ 1

Author(s):

S. A. Safvi ◽

T. J. Mountziaris

Keyword(s):

Activation Energy ◽

Thermal Decomposition ◽

Gas Phase ◽

Experimental System ◽

Operating Conditions ◽

Tertiary Butyl ◽

Carrier Gas ◽

Hydride Elimination ◽

Counterflow Jet Reactor ◽

Stagnation Plane

ABSTRACTA new reactor for studying the purely homogeneous thermal decomposition of organometallic precursors used in the Metalorganic Vapor Phase Epitaxy (MOVPE) of semiconductors is presented. The idea is based on the use of a counterflow jet configuration with one jet being heated and the other unheated. The heated jet contains pure carrier gas (typically hydrogen or nitrogen), while the unheated jet contains vapors of an organometallic species diluted in the same carrier gas. Under appropriate operating conditions, decomposition of the organometallic species takes place near the stagnation plane where the hot jet collides with the cool jet. Since the reactions occur in the gas phase and away from hot walls, purely homogeneous kinetics can be obtained. Such a counterflow jet reactor was designed for studying the thermal decomposition of tertiary-butyl-arsine (TBA), t-C4H9AsH2, a very promising precursor for MOVPE of GaAs films. Two-dimensional finite element simulations of transport phenomena and kinetics have been used to identify optimal operating conditions. An experimental system was constructed and capillary-sampled mass spectroscopy at the stagnation plane was used to study the thermal decomposition of TBA in nitrogen at a total pressure of 252 Torr. Gas-chromatography of the effluent gas stream was employed for positive identification of the hydrocarbon byproducts. The results indicate the existence of two major decomposition routes: (1) A low activation energy pathway producing isobutane AsH, and (2) a higher activation energy, β-hydride elimination pathway producing isobutene and arsine.

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The thermal decomposition of cyclobutane-1,2-dione

Canadian Journal of Chemistry ◽

10.1139/v85-488 ◽

1985 ◽

Vol 63 (11) ◽

pp. 2945-2948 ◽

Cited By ~ 6

Author(s):

J.-R. Cao ◽

R. A. Back

Keyword(s):

Activation Energy ◽

Thermal Decomposition ◽

Vapor Pressure ◽

Gas Phase ◽

Rate Constant ◽

Surface Reaction ◽

Order Rate Constant ◽

Reaction Vessel ◽

Arrhenius Parameters ◽

First Order

The thermal decomposition of cyclobutane-1,2-dione has been studied in the gas phase at temperatures from 120 to 250 °C and pressures from 0.2 to 1.5 Torr. Products were C2H4 + 2CO, apparently formed in a simple unimolecular process. The first-order rate constant was strongly pressure dependent, and values of k∞ were obtained by extrapolation of plots of 1/k vs. 1/p to1/p = 0. Experiments in a packed reaction vessel showed that the reaction was enhanced by surface at the lower temperatures. Arrhenius parameters for k∞, corrected for surface reaction, were log A (s−1) = 15.07(±0.3) and E = 39.3(±2) kcal/mol. This activation energy seems too low for a biradical mechanism, and it is suggested that the decomposition is probably a concerted process. The vapor pressure of solid cyclobutane-1,2-dione was measured at temperatures from 22 to 62 °C and a heat of sublimation of 13.1 kcal/mol was estimated.

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Catalytic influence of certain foreign gases on the thermal decomposition of di-tertiary butyl peroxide

Proceedings of the Royal Society of London Series A - Mathematical and Physical Sciences ◽

10.1098/rspa.1959.0014 ◽

1959 ◽

Vol 249 (1257) ◽

pp. 173-179 ◽

Cited By ~ 3

Keyword(s):

Activation Energy ◽

Thermal Decomposition ◽

Carbon Tetrachloride ◽

Rate Constant ◽

Tertiary Butyl ◽

Extended Theory ◽

Uncatalyzed Reaction ◽

Butyl Peroxide ◽

Limiting Value ◽

Induced Reaction

Silicon tetrafluoride accelerates the decomposition of di-tertiary butyl peroxide, the rate constant k n,x for a given pressure, n , of the peroxide rising with the fluoride pressure, x , to a limiting value k n ,∞ . This value is different for different values of n . The activation energy of the induced reaction is 27 ± 1 kcal compared with 37 kcal for the uncatalyzed reaction. The products are little different from those of the normal decomposition except that the ratio of methane to ethane is slightly increased. The order of effectiveness of fluorides is SiF 4 > SF 6 > CF 4 , the inverse order of the ease with which they should release fluorine atoms. Carbon tetrachloride causes acceleration comparable with that caused by the silicon fluoride with a much more drastic shift in the product ratios. The mechanism of these actions is discussed in relation to the extended theory of unimolecular reactions.

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Reactions with half-lives of several years

Australian Journal of Chemistry ◽

10.1071/ch9640406 ◽

1964 ◽

Vol 17 (4) ◽

pp. 406 ◽

Cited By ~ 8

Author(s):

GA Bottomley ◽

GL Nyberg

Keyword(s):

Activation Energy ◽

Thermal Decomposition ◽

Gas Phase ◽

Virial Coefficient ◽

Energy Equation ◽

Second Virial Coefficient ◽

First Order ◽

First Order Kinetics ◽

Reciprocal Temperature ◽

Temperature Activation

The gas-phase thermal decomposition of dimethyldiazirine, (CH3)2CN2, at very slow rates has been investigated using precision gas-volumetric techniques previously applied to second virial coefficient studies. At 50-70� the first-order kinetics correspond to half-lives about 0.3-3.0 years. The present results, together with data obtained by other workers using conventional apparatus at 124-174�, fit a single log rate-reciprocal temperature activation energy equation.

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THE THERMAL DECOMPOSITION OF METHYL HYDROPEROXIDE

Canadian Journal of Chemistry ◽

10.1139/v65-301 ◽

1965 ◽

Vol 43 (8) ◽

pp. 2236-2242 ◽

Cited By ~ 14

Author(s):

Alexander D. Kirk

Keyword(s):

Activation Energy ◽

Thermal Decomposition ◽

Gas Phase ◽

Rate Constants ◽

Dimethyl Phthalate ◽

Kcal Mole ◽

First Order ◽

Methyl Hydroperoxide ◽

Expected Values ◽

Homogeneous Decomposition

The thermal decomposition of methyl hydroperoxide has been studied in solution and in the gas phase. The decomposition was found to be partly heterogeneous in solution in dimethyl phthalate and no reliable rate constants were obtained. Use of the toluene carrier method for the gas phase work enabled measurement of the rate constant for the homogeneous decomposition. The first order rate constants obtained range from 0.19 s−1 at 292 °C to 1.5 s−1 at 378 °C, leading to log A, 11± 2, and activation energy, 32 ± 5 kcal/mole. These results are compared with the expected values of log A, 13–14, and activation energy, 42 kcal/mole. The significance of these findings is discussed.

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THE GAS PHASE REACTION OF METHYL RADICALS WITH HEXAFLUOROACETONE

Canadian Journal of Chemistry ◽

10.1139/v57-162 ◽

1957 ◽

Vol 35 (10) ◽

pp. 1216-1224 ◽

Cited By ~ 6

Author(s):

G. O. Pritchard ◽

E. W. R. Steacie

Keyword(s):

Activation Energy ◽

Thermal Decomposition ◽

Gas Phase ◽

Steric Factor ◽

Phase Reaction ◽

Methyl Radicals ◽

Kcal Mole ◽

Gas Phase Reaction

The photolytic and thermal decomposition of azomethane in the presence of hexafluoroacetone produces small amounts of fluorinated products, mainly fluoroform. The mechanism of this and related reactions is discussed. It is concluded that the proposed reaction.[Formula: see text]has an activation energy of about 6 kcal./mole, with a steric factor of about 10−5.

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Modelling of Gas-Phase and Surface Kinetics in Movpe of GaAs and AlxGal-xAs

MRS Proceedings ◽

10.1557/proc-204-219 ◽

1990 ◽

Vol 204 ◽

Cited By ~ 2

Author(s):

T.J. Mountziaris ◽

N.K. Ingle ◽

S. Kalyanasundaram

Keyword(s):

Gas Phase ◽

Kinetic Models ◽

Operating Conditions ◽

Surface Kinetics ◽

Tertiary Butyl ◽

Gaas Films ◽

Flow Heat ◽

Chemical Reaction Mechanisms ◽

Trimethyl Gallium ◽

Trimethyl Aluminum

ABSTRACTWe present detailed chemical reaction mechanisms that describe the deposition of GaAs films from tertiary-butyl-arsine (TBA) and trimethyl-gallium (TMG) as well as the deposition of AlxGa1-xAs (0≤x≤1) films from trimethyl-aluminum (TMAl), TMG and arsine during metalorganic vapor phase epitaxy (MOVPE). The kinetic models include both gas-phase and surface reactions, whose rates are used to predict production or consumption of the participating species as well as the growth rate of the film. Two-dimensional simulations of flow, heat and mass transfer in horizontal MOVPE reactors have been coupled with the kinetic models to provide a realistic picture of the process. The predicted growth rates at different operating conditions as well as the predicted incorporation ratio, x, of Al in the AlxGal-xAs films are in good agreement with experimental observations.

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The Thermal Decomposition of Tertiary Butyl Chloride in the Presence of Sulphur Hexafluoride

Australian Journal of Chemistry ◽

10.1071/ch9620437 ◽

1962 ◽

Vol 15 (3) ◽

pp. 437 ◽

Cited By ~ 8

Author(s):

RL Failes ◽

VR Stimson

Keyword(s):

Thermal Decomposition ◽

Gas Phase ◽

Simple Theory ◽

Triplet States ◽

Phase Decomposition ◽

Butyl Chloride ◽

Sulphur Hexafluoride ◽

Tertiary Butyl

No acceleration of the gas-phase decomposition of tertiary butyl chloride at 284-309 �C occurs in the presence of sulphur hexafluoride. This behaviour contrasts with that of a variety of unimolecular decompositions probably occurring via triplet states where an extension of the simple theory of activation has been found necessary.

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Tagasaste, leucaena and paulownia: three industrial crops for energy and hemicelluloses production

Biotechnology for Biofuels ◽

10.1186/s13068-021-01930-0 ◽

2021 ◽

Vol 14 (1) ◽

Author(s):

Alberto Palma ◽

Javier Mauricio Loaiza ◽

Manuel J. Díaz ◽

Juan Carlos García ◽

Inmaculada Giráldez ◽

...

Keyword(s):

Activation Energy ◽

Acid Hydrolysis ◽

Energy Production ◽

Combustion Process ◽

Operating Conditions ◽

Raw Material ◽

Energy Of Combustion ◽

Increasing Temperature ◽

Hydrolysis Of ◽

Chamaecytisus Proliferus

Abstract Background Burning fast-growing trees for energy production can be an effective alternative to coal combustion. Thus, lignocellulosic material, which can be used to obtain chemicals with a high added value, is highly abundant, easily renewed and usually inexpensive. In this work, hemicellulose extraction by acid hydrolysis of plant biomass from three different crops (Chamaecytisus proliferus, Leucaena diversifolia and Paulownia trihybrid) was modelled and the resulting solid residues were used for energy production. Results The influence of the nature of the lignocellulosic raw material and the operating conditions used to extract the hemicellulose fraction on the heat capacity and activation energy of the subsequent combustion process was examined. The heat power and the activation energy of the combustion process were found to depend markedly on the hemicellulose content of the raw material. Thus, a low content in hemicelluloses resulted in a lower increased energy yield after acid hydrolysis stage. The process was also influenced by the operating conditions of the acid hydrolysis treatment, which increased the gross calorific value (GCV) of the solid residue by 0.6–9.7% relative to the starting material. In addition, the activation energy of combustion of the acid hydrolysis residues from Chamaecytisus proliferus (Tagasaste) and Paulownia trihybrid (Paulownia) was considerably lower than that for the starting materials, the difference increasing with increasing degree of conversion as well as with increasing temperature and acid concentration in the acid hydrolysis. The activation energy of combustion of the solid residues from acid hydrolysis of tagasaste and paulownia decreased markedly with increasing degree of conversion, and also with increasing temperature and acid concentration in the acid hydrolysis treatment. No similar trend was observed in Leucaena diversifolia (Leucaena) owing to its low content in hemicelluloses. Conclusions Acid hydrolysis of tagasaste, leucaena and paulownia provided a valorizable liquor containing a large amount of hemicelluloses and a solid residue with an increased heat power amenable to efficient valorization by combustion. There are many potential applications of the hemicelluloses-rich and lignin-rich fraction, for example as multi-components of bio-based feedstocks for 3D printing, for energy and other value-added chemicals.

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