Zusammenfassung
Catalytic partial oxidation experiments with n-octane, 2,2,4-trimethylpentane
(i-octane), and an n-octane:i-octane (1:1) mixture were performed
on 80 and 45 ppi Rh-coated alpha-alumina foam supports at 2, 4,
and 6 SLPM total flow rate in order to explore the effects of chemical
structure for single components and binary mixtures on fuel reactivity
and product distribution. When reacted as single components, the
conversion of i-octane is greater than n-octane at C/O>1.1 (both
fuel conversions are 100% for C/O). However, when reacted in an equimolar
mixture, the conversion of n-octane is greater than i-octane. All
three fuels give high selectivity to syngas (H2 and CO) on 80 ppi
supports for C/O. For C/O>1, n-octane produces high selectivity to
ethylene while i-octane makes i-butylene and almost no ethylene.
The fuel mixture produces these species proportional to the mole
fractions of n-octane and i-octane within the reacting mixture. Increasing
the support pore diameter decreases the selectivity to syngas and
increases H2O and olefin selectivity.The reforming of all three fuels
is modeled using detailed chemistry by decoupling the heterogeneous
and homogeneous chemistry in a two-zone plug flow model. Detailed
homogeneous reaction mechanisms with several thousand elementary
reactions steps and several hundred species are used to simulate
experimentally observed olefin selectivities for all three fuels
on 80 and 45 ppi monoliths at 2, 4, and 6 SLPM quite well. These
results support the hypothesis that a majority of the observed olefins
are made through gas-phase chemistry.
Nutzer