High-Pressure Distributed Ethanol
Reforming
Background
Liquid
ethanol, a bioderived renewable fuel, is attractive for its high energy density
and ease of transport. Hydrogen produced by ethanol reforming must be purified
and compressed to appropriate storage and dispensing pressures. Compressing
hydrogen, however, is energy intensive and can consume a significant proportion
of the fuel’s heating value. One promising option for producing pressurized
hydrogen from ethanol is to perform the ethanol steam reforming reaction at high
pressure.
Challenges, however, accompany pressurized reforming. Calculations of
thermodynamic equilibrium predict that high-temperature reforming will lead to
lower hydrogen and higher methane yields. Also possible is an increased tendency
for the formation of coke deposits, which interfere with catalyst performance.
Argonne’s Research
Argonne researchers are investigating ways to overcome the challenges of
high-pressure ethanol reforming. To identify suitable conditions, they are
examining preferred catalysts, higher temperatures and the steam-to-carbon molar
ratio, and hydrogen separating membranes.
Accomplishments to date include:
- The design and fabrication of a palladium-alloy membrane reactor and
apparatus to study the effectiveness of hydrogen extraction on the kinetics
and hydrogen yield during the steam reforming of ethanol at high pressure.
- The measurement of the hydrogen transported across a membrane to
establish the hydrogen flux as a function of temperature and pressure
differential.
- The initiation of catalytic reaction studies and mathematical modeling
of the reactor being set up to extract global kinetic parameters.
Because injecting liquid feeds into a pressurized reactor requires very
little energy, it is advantageous to conduct the hydrogen production step
(reforming) in a pressurized reactor, thereby producing hydrogen at high
pressure and reducing the energy lost in compressing the hydrogen. Producing
hydrogen at high pressure would also offer flexibility in the selection of
hydrogen purification/separation technologies. More-compact systems (for greater
reactivity) and higher driving forces for pressure-based separation and
purification systems are additional expected advantages.
If the initial results from the pressurized reforming in a membrane reactor
are promising, the concept may be demonstrated at the pilot scale in
collaboration with industrial partners. Successful high-pressure distributed
ethanol reforming will expand hydrogen production options and help develop
capabilities critical for progress toward reduced reliance on fossil fuels.
This work is funded by the Hydrogen, Fuel Cells and Infrastructure
Technologies Program of the DOE Office of Energy Efficiency and Renewable
Energy.
Contact
Shabbir Ahmed
ahmeds@anl.gov |