The rapid development of catalytic membrane reactors requires
materials with a higher
permeability and a better mechanical stability than the current thick
membranes. Pd-based
composite membranes supported on porous stainless steel offer such an
alternative. However,
commercially available porous stainless steel materials have to be
further worked to reduce the
surface pore sizes and ensure the formation of thin Pd films in an
impervious form. In this
work, a shot peening treatment was performed on the surface of a porous
stainless steel to modify
its surface pore size. Substrates with effectively reduced surface
pore sizes were obtained under
mild peening conditions. The permeation behavior of the substrates
was examined using argon
as the permeation gas. Impervious thin palladium films were
deposited on the modified porous
substrate surface by electroless plating. Hydrogen permeability
through the resulting membranes was found to be comparable to that of pure palladium sheets,
while the permeation flux
was significantly enhanced due to the use of the thin Pd
membrane.
Furfural
is a versatile platform and multipurpose chemical that
can be produced with no carbon efficiency loss from pentose sugars
present in prehydrolysate streams. Existing processes for the production
of furfural are typically energy-intensive with limitations to recover
value-added molecules and byproducts such as lignin and acetic acid.
In this work, we demonstrate a novel integrated biorefinery process
for furfural production with significant sustainability improvements
to current production pathways. Higher conversion efficiency for C5 sugars into furfural is achieved with a novel reactor for
producing and recovering furfural in the vapor phase that has been
validated at the laboratory scale. Low molecular weight and sulfur-free
lignin is also recovered while minimizing energy consumption by employing
membrane filtration. Synergy was observed when lignin recovery is
performed prior to furfural production. On the basis of experimental
results, the scalability of the process for valorizing 3200 metric
tonne/day of prehydrolysate solutions that is typically combusted
in kraft dissolving pulp mills was evaluated. For a furfural production
capacity of 36 tonne/day, a process configuration that stands out
among four proposed alternatives was identified and designed. Significant
heat energy savings (99.5%) for driving the process was achieved through
a heat exchanger network design for internal heat recovery, which
resulted in an energy intensity of 0.47 GJ/tonne, corresponding to
1% of the energy intensity for conventional processes. The technoeconomic
assessment confirmed that even the least performing process is profitable,
robust, and capital-efficient as indicated by metrics such as the
internal rate of return (IRR) ranging from 30% to 46%, resistance
to market uncertainty (RTMU) between 0.9 and 4.3 $/$, as well as return
on capital employed (ROCE) between 49% and 91%.
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