2 research outputs found
Catalytic Partial Oxidation of Iso-octane over Rh/α-Al<sub>2</sub>O<sub>3</sub> in an Adiabatic Reactor: An Experimental and Modeling Study
Catalytic partial oxidation (CPO)
of hydrocarbons represents an
interesting technology for hydrogen production on mobile systems.
We investigated the CPO of 2,2,4-trimethyl pentane (iso-octane), chosen
as surrogate for gasoline. CPO experiments were carried out in a laboratory
scale autothermal reformer with honeycomb monolith catalysts (2% Rh/α-Al<sub>2</sub>O<sub>3</sub>), equipped with probes for spatially resolved
measurements of temperature and concentration. The iso-octane CPO
process follows a reaction pathway which mainly consists of the exothermic
combustion reaction and the endothermic steam reforming. The chemical
reaction is very fast, and sharp gradients of temperature and concentration
establish at the catalyst inlet. Similarly to the CPO of light hydrocarbons,
the consecutive reaction mechanism results in the formation of a hot
spot of temperature at the catalyst inlet. However, compared to light
hydrocarbons, this phenomenology is specifically emphasized in the
case of iso-octane, because of the higher overall exothermicity and
the lower diffusion rate, which limits the steam reforming reaction
rate. The reactor design strategy previously suggested in the CPO
of methane, based on the enlargement of the channel opening to selectively
limit the rate of oxygen consumption, does not work for the CPO of
iso-octane where the consumption of the fuel is also considerably
limited by mass transfer
Sustainable Hydrogen Production via Sorption Enhanced Reforming of Complex Biorefinery Side Streams in a Fixed Bed Adiabatic Reactor
In this work, sorption
enhanced steam reforming is explored as
a potential solution for the valorization of gaseous streams recovered
from biorefinery hydrogenation processes. The hydrogen content of
such streams limits the hydrocarbon conversion in conventional steam
reforming due to thermodynamic and kinetic constraints. A previously
developed 1D dynamic heterogeneous model of an adiabatic reactor was
thus applied to evaluate the effect of H2 dilution on the
performance indicators of the sorption enhanced reforming process.
The mathematical model analysis highlights that despite of CO2 capture by the sorbent favorably modifies the thermodynamics
of syngas production, H2 dilution worsens the performance
of the sorption enhanced reforming of model H2/CH4 streams with respect to pure CH4. Results show a drop
of 17% for CH4 conversion and a reduction of 15.4% of the
captured CO2 on passing from pure methane to a H2/CH4 feed with a 40/60 molar ratio. However, on increasing
the heat capacity of the bed, by replacing part of the sorbent with
an inert heat carrier, better performances are calculated for the
H2/CH4 feed matching the pure CH4 case. The presence of C2+ hydrocarbons is assessed as well and the
results show a significant improvement in the reformer’s performance;
in the case of a stream composed of H2/CH4/C3H8 with a molar ratio 40/45/15, the total hydrocarbon
conversion grows to 92.8%, CO2 capture ratio to 82.6%,
and H2 purity to 95.6%. The positive effect is associated
with thermal factors that promote the reaction kinetics. Thus, the
suitability of the sorption enhanced reforming technology to H2-rich and C-poor streams is strictly composition dependent;
by cofeeding of C2+ hydrocarbons, the process turns into a remarkable
solution for converting gaseous streams in pure H2