Pyrolysis of acetylene in sonolytic cavitation bubbles in aqueous solution
- Hahn-Meitner-Institut Berlin GmbH (West Germany)
Water was irradiated with 1 MHz ultrasound (about 2 W/cm{sup 2}) under mixtures of argon and acetylene of various compositions. A few experiments were performed using deuterated acetylene. Acetylene is rapidly consumed, the maximum rate occurring at a solution concentration of C{sub 2}H{sub 2} of 2 {times} 10{sup {minus}3} M. The products are H{sub 2}, CO, CH{sub 4}, a great number of hydrocarbons containing two to about eight C atoms, formic and acetic acids, formaldehyde and acetaldehyde, and insoluble soot. Some larger product molecules are benzene, isomers of benzene, phenylacetylene, styrene, and naphthalene. The products are similar to the ones observed in the pyrolysis and combustion of acetylene. The relative abundancies of the products change with acetylene concentration, which is in part attributed to the varying temperature of the adiabatically compressed cavitation bubbles. All products are initially formed proportional to the irradiation time, even at times in the 10-s range. Volatile products are, however, consumed in longer irradiations. It is concluded that all products are formed in single cavitation events and not by stepwise formation and subsequent sonolysis of intermediate compounds in different cavitation bubbles. A mechanism is proposed according to which water vapor decomposition is the main primary process at low C{sub 2}H{sub 2} concentration, the OH radical and H and O atoms formed attacking acetylene molecules. At higher C{sub 2}H{sub 2} concentrations, the direct pyrolysis of acetylene is the principal primary process, C{sub 4}H{sub 2} and C{sub 4}H{sub 4} being formed as the most important precursors of the higher C atom number products. Among the latter, even C atom numbers are more abundant than odd numbers. Small soot molecules form a colloid absorbing uniformly at all wavelengths in the UV/vis region, and larger molecules mainly scatter light.
- OSTI ID:
- 6712758
- Journal Information:
- Journal of Physical Chemistry; (USA), Vol. 94:1; ISSN 0022-3654
- Country of Publication:
- United States
- Language:
- English
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Related Subjects
ORGANIC
PHYSICAL AND ANALYTICAL CHEMISTRY
ACETYLENE
PYROLYSIS
AQUEOUS SOLUTIONS
ARGON
CALCULATION METHODS
CARBON MONOXIDE
DATA ANALYSIS
EXPERIMENTAL DATA
HYDROGEN
MEASURING INSTRUMENTS
MEASURING METHODS
MECHANICS
METHANE
ULTRASONIC WAVES
ALKANES
ALKYNES
CARBON COMPOUNDS
CARBON OXIDES
CHALCOGENIDES
CHEMICAL REACTIONS
DATA
DECOMPOSITION
DISPERSIONS
ELEMENTS
FLUIDS
GASES
HYDROCARBONS
INFORMATION
MIXTURES
NONMETALS
NUMERICAL DATA
ORGANIC COMPOUNDS
OXIDES
OXYGEN COMPOUNDS
RARE GASES
SOLUTIONS
SOUND WAVES
THERMOCHEMICAL PROCESSES
400200* - Inorganic
Organic
& Physical Chemistry
400800 - Combustion
Pyrolysis
& High-Temperature Chemistry