Oxydation lente du cétène en phase gazeuse. II. Réaction à "basses températures"

1971 ◽  
Vol 49 (2) ◽  
pp. 303-306 ◽  
Author(s):  
Pierre Michaud ◽  
Cyrias Oueixet
Keyword(s):  
Carbon Dioxide ◽  
Carbon Monoxide ◽  
Low Temperature ◽  
Reaction Scheme ◽  
Phase Gazeuse ◽  
Temperature Range ◽  
Slow Combustion ◽  
Methyl Hydroperoxide

The slow combustion of ketene was investigated in the low-temperature range 280–350 °C. It differs from the reaction at higher temperatures chiefly by the presence of peroxides (mostly hydroperoxides) and the absence of methane. The main products: formaldehyde, carbon monoxide, water, and carbon dioxide are the same in both cases. A reaction scheme is proposed, which involves degenerate branching through the decomposition of methyl hydroperoxide: CH3OOH = CH3O• + •OH.

The slow combustion of cyclo propane - II. Analytical results and mechanism

1953 ◽  
Vol 220 (1141) ◽  
pp. 266-277 ◽  
Keyword(s):  
Carbon Dioxide ◽  
Carbon Monoxide ◽  
Maximum Rate ◽  
Surface Effect ◽  
Reaction Scheme ◽  
Maximum Pressure ◽  
Elementary Reactions ◽  
Analytical Results ◽  
Slow Combustion ◽  
Initial Oxygen

The stable products of the reaction between oxygen and cyclopropane are carbon monoxide and water with small amounts of carbon dioxide, methane and hydrogen. The only organic intermediate formed is formaldehyde, the pressure of which during an experiment rose to a maximum at the time of the maximum rate. This maximum pressure was proportional to the initial cyclopropane pressure and independent of the initial oxygen pressure unless that was very low. Addition of formaldehyde initially reduced the induction period but had little effect on the maximum rate. The initial addition of water slightly catalyzed the reaction, but this was a surface effect. A detailed reaction scheme, which explains the kinetic and analytical results, is proposed, and the various elementary reactions composing it discussed. It is suggested that formaldehyde was formed by means of the production and decomposition of cyclopropylperoxyl (C 3 H 5 O 2 ) radicals and was responsible for the delayed branching (McEwan & Tipper 1953); and that the reaction chains involved OH and HO 2 radicals, termination having occurred by reaction of the latter on the walls.

scholarly journals The Formation of the Oxides of Carbon by the Pyrolysis of Tobacco

1975 ◽  
Vol 8 (1) ◽  
Author(s):  
R. R. Baker
Keyword(s):  
Carbon Dioxide ◽  
Carbon Monoxide ◽  
High Temperature ◽  
Low Temperature ◽  
Heating Rate ◽  
Temperature Region ◽  
High Temperature Region ◽  
Heating Rates ◽  
Carbon Oxides ◽  
Decomposition Reactions

AbstractFlue-cured Virginia tobacco has been heated in nitrogen and nitrogen/oxygen mixtures under flow conditions, and the rate of formation of carbon monoxide and carbon dioxide has been determined as a function of temperature, heating rate, and proportion of oxygen in the gas. When the tobacco is heated in nitrogen at heating rates comparable to those in a smouldering cigarette, 27 % of the carbon content of the tobacco is converted to carbon oxides. Both carbon oxides show two distinct formation regions: a low-temperature region (about 100°-450°C), and a high-temperature region (about 550°-900°C). These temperature limits are almost identical to those predicted from studies on the combustion coal of a cigarette burning in air. When tobacco, or the carbonaceous residue remaining after the pyrolysis experiments, is heated in nitrogen / oxygen mixtures, the total amount of carbon converted to carbon monoxide and carbon dioxide is independent of heating rate, but the relative proportions of the two oxides are strongly dependent on heating rate. At the lower heating rate, proportionally less carbon monoxide, and more carbon dioxide, is produced. Under oxidation conditions, about 70 % of both carbon oxides formed in the low-temperature region (100°-450°C) are produced by tobacco decomposition reactions, whereas in the high-temperature region about 10-20 % of the carbon monoxide, and 2-9 % of the carbon dioxide, are produced by tobacco decomposition.

Oxydation lente du cétène en phase gazeuse. I. Réaction à "hautes températures"

1971 ◽  
Vol 49 (2) ◽  
pp. 294-302 ◽  
Author(s):  
Pierre Michaud ◽  
Cyrias Ouellet
Keyword(s):  
Carbon Dioxide ◽  
Carbon Monoxide ◽  
Gas Phase ◽  
Static Method ◽  
Chain Reaction ◽  
Slow Combustion ◽  
Temperature Ranges ◽  
Higher Temperature ◽  
A Chain ◽  
Two Temperature

The slow combustion of ketene in the gas phase was studied by the static method in a 30 × 4 cm Vycor cylinder between 280 and 500 °C at pressures above 20 mm Hg. Extending the work of Barnard and Kirschner, we have established the existence of two types of slow combustion of ketene corresponding to two temperature ranges. In this first paper, we describe the kinetic and analytical results obtained in the higher temperature range (380–500 °C). The reaction is autocatalytic and shows a low temperature coefficient corresponding to a few kilocalories per mole. The main products are carbon monoxide, formaldehyde, water, and carbon dioxide. No ethylene was detected. We suggest a chain reaction in which formaldehyde is the intermediate responsible for degenerate branching:[Formula: see text]

The slow combustion of cyclo pentane - II. Analytical results and mechanism

1958 ◽  
Vol 246 (1244) ◽  
pp. 64-77 ◽  
Keyword(s):  
Carbon Dioxide ◽  
Gas Phase ◽  
Maximum Rate ◽  
Pressure Change ◽  
Reaction Scheme ◽  
Elementary Reactions ◽  
Slow Combustion ◽  
Initial Oxygen ◽  
Increasing Temperature ◽  
True Measure

The products of the oxidation of cyclo pentane in the gas phase at around 400 °C in an uncoated vessel were water, carbon monoxide and carbon dioxide with smaller amounts of hydrogen, methane, ethylene, propylene, cyclo pentane, formaldehyde, higher aldehydes (mainly acetaldehyde) and acids. It was confirmed that the pressure change was true measure of the extent of reaction. The pressures of higher aldehydes and unsaturates rose to a maximum at about the time of the maximum rate, and the variation of these maximum pressures with initial oxygen and cyclo pentane pressures was investigated. Addition of formaldehyde initially had little effect on the reaction, but addition of higher aldehydes reduced the induction period and increased the maximum rate. The CO/CO 2 ratio increased with increasing temperature and cyclo pentane pressure and was much greater with the boric-acid-coated vessel. Also using this vessel peroxidic material was detected in the products. Higher aldehydes were probably the substances responsible for delayed branching. The various elementary reactions which may have occurred in the system are discussed and a reaction scheme which can explain the products and to some extent the kinetic results is proposed. Cyclo pentylperoxy (C 5 H 9 O 2 ) radicals were probably important both in propagating and terminating the chains.

scholarly journals The law of distribution in the case in which one of the phases possesses mechanical rigidity: Adsorption and occlusion

1906 ◽  
Vol 78 (521) ◽  
pp. 9-22 ◽  
Keyword(s):  
Carbon Dioxide ◽  
Carbon Monoxide ◽  
Low Temperature ◽  
Active Substance ◽  
Chemical Combination ◽  
Two Phases ◽  
Pass Through ◽  
Active Change ◽  
Previous Existence

The term “occlusion” has been applied somewhat indiscriminately to denote the state in which a gas exists in a solid, by which it has been absorbed, or from which it is evolved on heating, and no doubt the term includes phenomena of a totally different character. Similarly, the term “adsorption” is commonly used to differentiate between simple cases of solution and the removal of substances from solutions by solids in contact with them. It is the object of this paper to point out similarities which exist between certain cases, which may be included in these two groups, and to make some suggestions as to the classification of the phenomena. In the first place we may dispose of certain instances in which solids evolve gases when they are heated, the change being irreversible. In 1898 I succeeded in showing that the evolution of such gases as hydrogen and carbon monoxide from minerals on heating did not require the assumption of their previous existence in the minerals at all; hence, there was no need to introduce the term occlusion to explain it. I proved that the gases were produced by the interaction of water vapour and carbon dioxide with such substances as ferrous oxide, the change being followed quantitatively. Later, I put forward an explanation of the evolution of helium from minerals, in which it cannot be supposed to be present in a state of chemical combination. Ramsay and Soddy had shown that helium was one of the products of radio-active change, and had suggested that its presence in the minerals was due to the decay of some radio-active substance which they had formerly contained. This explanation did not, however, account for the retention of the gas in the mineral, and the clue to the solution of this part of the problem was given by Jaquerod’s discovery that helium would pass through the walls of a quartz bulb at a comparatively low temperature, though this material is quite impermeable to it in the cold. It follows that the gas may be present in the mineral in a state of supersaturation, and may remain in that state for an indefinite time, if the temperature is moderately low. When, however, the mineral is heated, the gas can diffuse freely through it, and there is a tendency to establish equilibrium between the two phases.

The gaseous oxidation of acetone - II. The low-temperature reaction

1964 ◽  
Vol 279 (1377) ◽  
pp. 248-259 ◽  
Keyword(s):  
Low Temperature ◽  
Temperature Region ◽  
Low Temperatures ◽  
Peroxy Radical ◽  
Reaction Scheme ◽  
Methyl Radical ◽  
High Temperature Region ◽  
Region I ◽  
Methyl Hydroperoxide ◽  
Kinetics Of

The kinetics of the oxidation of acetone in the 'low-temperature’ region (i. e. below 320°C) have been carefully investigated. In contrast to the high-temperature region, the products include no methane, but appreciable quantities of methyl hydroperoxide as well as water, carbon monoxide and dioxide. A reaction scheme is suggested which involves degenerate chain branching by the homo­geneous decomposition of methyl hydroperoxide. The transition from the low-temperature mechanism to that prevailing at high tempera­tures is due to the changing importance of the alternative reactions of the methyl radical. At low temperatures, the formation of methyl hydroperoxide is favoured CH 3 + O 2 + M = CH 3 O 2 + M , CH 3 O 2 + R H = CH 3 O 2 H + R , whereas at high temperatures the methyl peroxy radical is too unstable to abstract hydro­gen and instead the reaction yields formaldehyde CH 3 + O 2 = HCHO + OH.

THE REACTIONS OF METHYLENE RADICALS WITH ACETALDEHYDE AND PROPIONALDEHYDE

1965 ◽  
Vol 43 (1) ◽  
pp. 106-118 ◽  
Author(s):  
M. H. Back
Keyword(s):  
Carbon Dioxide ◽  
Carbon Monoxide ◽  
Methyl Ethyl Ketone ◽  
Propylene Oxide ◽  
Methyl Ethyl ◽  
Temperature Range ◽  
Low Pressures

The reactions of methylene radicals with acetaldehyde and propionaldehyde have been studied over the temperature range 48–118 °C and over a range of pressures of aldehyde and carbon dioxide. From acetaldehyde, the main products were carbon monoxide, methane, ethane, and acetone, with small amounts of ethylene at low pressures of acetaldehyde. With carbon dioxide present, small amounts of propylene oxide were formed, but propionaldehyde was not observed. The main products from the reaction with propionaldehyde were carbon monoxide, methane, ethane, and ethylene, with small amounts of methyl ethyl ketone, butene oxide, and isobutyraldehyde. The relation of the results to the relative rates and mode of attack of methylene on the various bonds is discussed.

Low-temperature partial oxidation of ethanol on Ni/ZnO catalyst

2019 ◽  
pp. 27-36
Author(s):  
N. V. Lapin ◽  
V. V. Grinko ◽  
V. S. Bezhok ◽  
A. F. Vyatkin
Keyword(s):  
Carbon Dioxide ◽  
Carbon Monoxide ◽  
Zinc Oxide ◽  
Nickel Catalyst ◽  
Partial Oxidation ◽  
Methane Content ◽  
Metallic Nickel ◽  
Molar Ratio ◽  
Temperature Range ◽  
Oxidation Of Ethanol

The paper investigates the partial oxidation of ethanol process in a quartz microreactor at atmospheric pressure in the temperature range 300–450 °C on a nickel catalyst (20 wt%) deposited on zinc oxide. Rectified ethanol (an azeotropic mixture of 95.6 wt.% ethanol and 4.4 wt.% water) is fed into the reactor at a rate of 0.4–1.3 g / hour by a peristaltic pump, first into the evaporator, and then as a gas phase into the reactor. Air is used as a source of oxygen which is supplied by an air pump to the reactor and its flow is controlled by a rotameter so that the oxygen-ethanol molar ratio varied between 0.45 and 2.0. The nickel catalyst is prepared by impregnating industrial zinc oxide powder with nickel nitrate, followed by calcination and reduction of nickel oxide to metallic nickel. Analysis of gaseous products is performed on a Tsvet-500 gas chromatograph. The detector is a katharometer.A catalyst Ni/ZnO developed earlier is shown to have high efficiency in the partial oxidation of ethanol at low temperatures. The main products of this process are hydrogen, methane, carbon monoxide and dioxide. With an increase in the oxygen-ethanol molar ratio, the hydrogen content in the products of the process decreases (from 60 to 25 vol.%), carbon dioxide, on the contrary, increases (26 to 65 vol.%). The hydrogen yield is 1 mol per 1 mol of ethanol at a temperature of 450 °C.Carbon monoxide is observed with a low ratio of oxygen-ethanol (up to 0.85). With a higher ratio, carbon monoxide is absent in the entire temperature range studied. The conversion of ethanol proceeds intensively and already at a temperature of 450 °C ethanol is converted almost completely. A high methane content (20–30% vol.%) in reforming products indicates that the initial stage of the process is the oxidation of ethanol followed by decomposition of the resulting acetaldehyde into methane and carbon monoxide.The insignificant water content in the supply mixture leads to an almost complete absence of a shift reaction. Carbon monoxide is then oxidized with oxygen to carbon dioxide. The reduced methane content in comparison with the process of water-steam ethanol reforming can be explained by its partial oxidation to carbon dioxide, which explains the high content of the latter in reforming products. 

Sign in / Sign up

Export Citation Format

Share Document