Acetaldehyde ignition temperature

The next aldehyde is acetaldehyde, a colorless liquid with a pungent taste and a fruity odor. Its molecular formula is CH,CHO. It has a flash point of -40°F, an ignition temperature of 340°F, and is toxic by inhalation. Acetaldehyde is used in die manufacture of many other chemicals. Other important aldehydes are propionaldehyde, butyraldehyde, and acrolein. 

Acetaldehyde (ethanal, CH3CH=0, melting point-123.5°C, boiling point 20.1°C, density 0.7780, flashpoint -38°C, ignition temperature 165°C) is a colorless, odorous liquid. 

For the most reactive substances (such as acetaldehyde or diethyl ether in equimolar proportions with oxygen) the minimum ignition temperature is at about 480-500 K as the pressure approaches 100 kPa in normal laboratory experiments (typically vessels of up to 0.5 dm ). The apex of the... 

Catalysts such as iron oxides cause isomeriza tion of the ethylene oxide to acetaldehyde with the evolution of heat. The acetaldehyde has a much lower autoignition temperature in air than does ethylene oxide, and the two effects may lead to hot-spot ignition (190,191). 

A mixture of acetaldehyde/air of a concentration of 30-60% combusts when it is in contact with substances that are heated at 176°C. The mixture with oxygen of concentration of 60-80% combusts at 105°C. If the object is metallic and furthermore corroded, the ignition can become spontaneous even at ambient temperature. The same goes for corroded aluminium pipes where the AIT reaches 130°C, if vapour concentration is 55-57%. The AIT is also sensitive to the size and shape of the containers that contain acetaldehyde vapour. 

These materials are very easily autoxidised and often have a low autoignition temperature. It is reported that many of the less volatile liquid aldehydes will eventually inflame if left exposed to air on an absorbent surface. The mechanism is undoubtedly similar to that giving rise to easy ignition in the air-oxidation of acetaldehyde and propionaldehyde initial formation of a peroxy-acid which catalyses the further oxidation[l]. Autoignition temperatures of lower aldehydes are much reduced by pressure, but appear to depend little on oxygen content. The effect is worst in the presence of free liquid, in which initial oxidation appears to occur, possibly catalysed by iron, followed by ignition of the vapour phase [2], An acetaldehyde/rust mix exploded at room temperature on increasing the air pressure to 7 bar. 

Our first example of a chain reaction, the decomposition of acetaldehyde to methane and CO, is endothermic so the reactor tends to cool as reaction proceeds. However, the oxidation of H2 is exothermic by 57 kcal/molc of H2, and the oxidation of CH4 to CO2 and H2O is exothermic by 192 kcal/mole of CH4. Thus, as these reactions proceed, heat is released and the temperature tends to increase (strongly ). Thus thermal ignition is very important in most combustion processes. 

During the slow oxidation of triethylamine, one of the products, diethylamine, appears to inhibit reactions leading to its own formation (9). Moreover, acetaldehyde is formed in the presence of oxygen and is stable at temperatures at which it is normally oxidized readily. This result was ascribed to inhibition of acetaldehyde by both the reactant (triethylamine) and the principal nitrogenous products (diethylamine and ethylamine). These findings preceded several detailed studies of the effect of aliphatic amines on the slow oxidation and the ignition of... 

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