A Film Boiling Study of Ethanol Pyrolysis

This
paper reports a study of ethanol pyrolysis (C2H5OH, EtOH) by film boiling at temperatures ranging from 600
to 1500 K. The reactor space is created in a self-assembled manner
by first bringing EtOH to a boil on the surface of a horizontal tube
submerged in a pool of EtOH and then increasing the power to the tube
in steps to force transitioning the boiling regimes through nucleate
boiling, the critical heat flux state, and finally film boiling. EtOH
pyrolysis is found to yield hydrogen in the highest concentration
followed by ethylene (C2H4), methane (CH4), and carbon monoxide (CO) in approximately equal proportions.
Ethane (C2H6) and carbon dioxide (CO) concentrations
were several orders of magnitude lower. The abundance of hydrogen
was conjectured to be due to the absence of chemical inhibitors in
the system. Reactions to explain formation of the product gases are
suggested based on the chain nature of EtOH decomposition. Liquid
sampling showed the presence of refluxed water along with acetaldehyde
(CH3CHO) and trace quantities of formaldehyde (CH2O) and ethyl acetate (CH3COOC2H5). Evidence of heterogeneous surface reactions is postulated for
tube temperatures below about 1000 K. The results are consistent with
more conventional reactor designs, which establishes the potential
for film boiling to serve as a simple and useful chemical processing
technology.