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The control of anthropogenic carbon dioxide (CO2) emissions is one of the most challenging environmental issues facing industrialized countries because of its implications to atmospheric CO2 levels and climatic change. Burning of fossil fuels is responsible for the majority of these CO2 emissions and, therefore, there is significant interest in developing technologies that will reduce CO2 emissions. The membrane-based separation processes are not only cost effective and environmentally friendly, but also with many novel polymeric materials available, offer much more versatility and simplicity in customized system designs. The ability to selectively pass one component in a mixture while rejecting others describes the perfect separation device. We have synthesized a set of poly(urethane-imide)-POSS (PUI) by the simple condensation reaction of isocyanate terminated polyurethane (PU) prepolymer and anhydride terminated polyimide (PI) prepolymer. The PUIs were characterized by TGA, SEM, and AFM analyses. Thermal stability of the PU was found to increase by the introduction of imide component. Gas permeation measurements were studied for O2, N2, and CO2 gases by employing different pressures using constant volume/variable pressure apparatus.
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1 23
Clean Technologies and
Environmental Policy
Focusing on Technology Research,
Innovation, Demonstration, Insights
and Policy Issues for Sustainable
ISSN 1618-954X
Clean Techn Environ Policy
DOI 10.1007/s10098-012-0500-7
Cost effective poly(urethane-imide)-POSS
membranes for environmental and energy-
related processes
D.Gnanasekaran & B.S.R.Reddy
1 23
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Cost effective poly(urethane-imide)-POSS membranes
for environmental and energy-related processes
D. Gnanasekaran B. S. R. Reddy
Received: 19 February 2012 / Accepted: 31 May 2012
ÓSpringer-Verlag 2012
Abstract The control of anthropogenic carbon dioxide
) emissions is one of the most challenging environ-
mental issues facing industrialized countries because of its
implications to atmospheric CO
levels and climatic
change. Burning of fossil fuels is responsible for the
majority of these CO
emissions and, therefore, there is
significant interest in developing technologies that will
reduce CO
emissions. The membrane-based separation
processes are not only cost effective and environmentally
friendly, but also with many novel polymeric materials
available, offer much more versatility and simplicity in
customized system designs. The ability to selectively pass
one component in a mixture while rejecting others
describes the perfect separation device. We have synthe-
sized a set of poly(urethane-imide)-POSS (PUI) by the
simple condensation reaction of isocyanate terminated
polyurethane (PU) prepolymer and anhydride terminated
polyimide (PI) prepolymer. The PUIs were characterized
by TGA, SEM, and AFM analyses. Thermal stability of the
PU was found to increase by the introduction of imide
component. Gas permeation measurements were studied
for O
, and CO
gases by employing different pressures
using constant volume/variable pressure apparatus.
Keywords Poly(urethane-imide)-POSS Membranes
Environmental Carbon dioxide
Global warming has been identified as one of the world’s
major environmental issues that need to be taken into
consideration on a global level. The global warming is
caused by the emission of greenhouse gases and most of
the component is carbon dioxide (CO
). The emissions of
have been dramatically increased for the last 50 years
and yet continually increasing each year (Powell and Qiao
2006). This leads to an increasing CO
level in the atmo-
sphere which in turn, causes the global temperature to rise.
There are several points within stationary energy produc-
tion where CO
is produced and then emitted into the
atmosphere, such as in the production of natural gas from
an underground reservoir and in the production of synthesis
gas using fossil fuels and flue gas from electricity power
stations that are from direct combustion of fossil fuels
(Jung et al. 2004). Usually, CO
is the most abundant
contaminant in a typical natural gas feed, with some large
reservoirs containing over 50 % CO
. Carbon dioxide
emitted inevitably from the combustion of fossil fuels, has
attracted increasing attention because of its potential
impact on global climate change. With the rapidly
increasing interest in CO
separation to mitigate global
warming, separation of gases using polymeric membranes
will remain an active research area and the literature will
continue to grow as new discoveries are made in the art.
This article focuses on the most recent polymeric
membrane designs, mainly nano-incorporated membranes
as shown in Fig. 1and facilitated transport membranes,
which provide improved CO
separation over the previous
polymeric designs. There are five possible mechanisms
for membrane separation (Paul and Yampolskii 1994;
Fritzsche and Kurz 1990) such as knudson diffusion,
molecular sieving, solution-diffusion separation, surface
D. Gnanasekaran B. S. R. Reddy (&)
Industrial Chemistry Laboratory, Central Leather Research
Institute (Council of Scientific & Industrial Research),
Chennai 600 020, India
Clean Techn Environ Policy
DOI 10.1007/s10098-012-0500-7
Author's personal copy
diffusion, and capillary condensation. Molecular sieving
and solution diffusion are the main mechanisms for nearly
all gas-separating membranes. Knudson separation is based
on gas molecules passing through membrane pores small
enough to prevent bulk diffusion.
Separation is based on the difference in the mean path of
the gas molecules due to collisions with the pore walls
which is related to the kinetic diameter (Table 1). Pores
within the membrane are of a carefully controlled size
relative to the kinetic diameter of the gas molecules. This
allows diffusion of smaller gases at a much faster rate than
larger gas molecules. In this case, the CO
, selectivity is
greater than unity, as CO
has a smaller kinetic diameter
than N
. Surface diffusion is the migration of adsorbed
gases along the pore walls of porous membranes (Hill
1956; Hwang and Kammermeyer 1975). Polymeric mem-
branes are generally non-porous, and therefore gas per-
meation through them is described by the solution-
diffusion mechanism as shown in Fig. 2(Paul and Yam-
polskii 1994; Ganapathi-Desai and Sikdar 2000). This is
based on the solubility of specific gases within the mem-
brane and their diffusion through the dense membrane
matrix. Hence, separation is not just diffusion dependent
but also reliant on the physical–chemical interaction
between the various gas species and the polymer which
determines the amount of gas that can accumulate in the
membrane polymeric matrix. The ability to selectively pass
one component in a mixture while rejecting others
describes the perfect separation device. While no mem-
brane system truly behaves this way, membrane gas sepa-
ration do have a number of advantages over conventional
processes and a number of reviews examining their benefits
exist (Stern 1994; Powell and Qiao 2006; Maiser 1998;
Koros 2002; Baker 2002). In particular, this article has
focused on advances in polymeric membrane design for
improved CO
Materials and methods
The Cy-POSS was synthesized in our laboratory as explained
in our previous work (Gnanasekaran et al. 2011). Hexam-
ethylene diisocyanate (Merk, 95 %) was used as received,
poly(dimethylsiloxane) bis(hydroxylalkyl) as terminated
=5,600) (Aldrich, 99 %), and 4,40-(hexafluoroisopro-
pylidene) dipthalicdianhydride (Aldrich, 99 %) was purified
by sublimation under vacuum. Dibutyltin dilarurate
(Aldrich, 95 %), and tetrahydrofuran (Rankem) was distilled
using calcium hydride and sodium metal. All other chemi-
cals were analytical grade and used as received.
Si-NMR spectra of the samples were recorded on Jeol
ECA-500 NMR spectrometer at 99 MHz. The thermal
stabilities of the prepared membranes were determined
using Perkin-Elmer TGA-7 and TGA Q50-TA thermal
analyzers. The thermogravimetric analysis (TGA) curves
were recorded using 10–15 mg of samples at a heating rate
of 5 °C min
under nitrogen atmosphere.
The scanning electron microscopy (SEM) pictures were
taken on the flat surface and cross sections of the hybrid
membranes. Surface morphology of hybrid membranes
was studied using a Nanoscope III atomic force microscopy
(AFM) instrument and imaging was done in contact mode
Fig. 1 Structure of nanomaterial (POSS)
Table 1 Kinetic diameters of penetrants
Gas Lennard–Jones
diameter (A
diameter (A
He 2.57 2.60
2.91 2.89
3.61 3.64
3.43 3.46
3.82 3.80
3.99 3.30
D. Gnanasekaran, B. S. R. Reddy
Author's personal copy
at room temperature in air. In these studies, we have used
the commercial tip of Si
provided by Digital Instru-
ments. Cantilever length is 200 lm with a spring constant
of 0.12 Nm
Permeation measurements
The permeation properties of poly(urethane-imide)-POSS
(PUI) membranes were determined utilizing a constant
pressure/variable volume apparatus. The upstream pressure
was varied between 1 and 4 atm, whereas the downstream
pressure was the atmospheric pressure. Gas flow rates were
measured with a soap-film bubble flow meter. The tem-
perature was maintained at 30 °C(±1°C). Before each
experiment, both the upstream and downstream sides of
permeation cell were purged with penetrant gas.
Results and discussion
Si Solid-state CP/MAS NMR spectroscopy
The solid-state
Si NMR spectrum of the PUI hybrids
provides much more information about the type of Si units
present in the hybrids and the spectrum of PUI-20 is shown
in Fig. 3. The silicon atom corresponding to the Si–OH
shift disappeared in the CyPOSS-incorporated hybrids,
confirming that all the Si–OH groups were reacted with the
isocyanate groups. The urethane-connected Si atom showed
a signal at -65.5 ppm which was merged with T
silicon atom present in the ring structure. This confirms the
formation of urethane linkages with silicon atom present in
the POSS molecules. The resonance signal at -20.2 ppm
was the characteristic signal representing Si atom present in
the PDMS backbone. The peak at 10.1 ppm corresponds to
the terminal Si atom (Si(CH
) attached to the PDMS
chain and the CyPOSS molecule. From the spectral studies,
it was found that both the PDMS and CyPOSS retain their
cage structure even after hybridization.
The thermal stability of the PUI membranes was measured
by TGA at a heating rate of 10 °C min
as shown in Fig. 4.
Polyurethane (PU) exhibited 50 % weight loss at 443 °C.
With the increase in PI content, the decomposition tem-
perature of the poly(urethane-imide) membrane increased
from 443 to 492 °C at 50 % weight loss. Compared to PU,
poly(urethane-imide) membranes exhibited better thermal
stabilities due to the presence of the heterocyclic imide
groups without phase separation in poly(urethane-imide)
(Park et al. 2006). In general, imide rings are considered to
be the most stable units among these linking groups. But,
urethane groups must be the most labile units and will
decompose first to start the initial thermal degradation.
Assuming different stabilities of the urethane and the imide
units, the first stage of weight loss might be attributed to the
early degradation of the urethane linkages. The reason for
Fig. 2 The gas separation
PUI for environmental and energy-related processes
Author's personal copy
these results could be that the more thermally sensitive PU
moiety began to decompose before PI moiety was degraded.
The pure PI with a tighter and more rigid coherence between
chains possess a good thermal stability, whereas PUI sam-
ples having a relatively increased amount of hard segment,
in the case of PUI-10 to PUI-20, had less chain coherence
because of fewer imides in the backbone chains.
The cross-sectional view of PU and PUI-10 hybrids is
shown in Fig. 5. All the PUI films show a microphase
separation of urethane hard segments and a micro/nano
level spheroidical aggregation of POSS-rich domains. The
aggregation of POSS molecules increases with increase in
the imide content. This may be due to the highly hydro-
phobic nature of POSS group. The cross-sectional view of
both the hybrids confirms the absence of formation of
microcracks or voids in the hybrid membranes. The cross-
sectional view of hybrid membranes demonstrated that the
microphase separation and POSS aggregation were not
only formed on the surface of the membranes, but also
formed throughout the hybrids. The type of aggregation
and the microphase separation of PUI hybrids were quite
different from the PU or PUI-10 hybrids.
The surface morphology and roughness of the formed PU
and PUI hybrid membranes were investigated by AFM. The
membranes PUI-10, PUI-20, and PUI-30 showed a rough
Fig. 3 Solid-state
Si NMR spectrum of PUI-20
Fig. 4 TGA curves of PUI membranes
Fig. 5 Cross-sectional view of SEM images of PU and PUI-10 membranes
D. Gnanasekaran, B. S. R. Reddy
Author's personal copy
surface for the composite and the formation of a less
homogeneous surface compared to the PU membranes. The
surface topography, three-dimensional topographical image
and the phase images are given in Fig. 6. The extent of
projection of one phase and the surface roughness also
increased with increase in the PI content. Therefore, this
could be attributed to the existence of non-compatible
phases. It has been reported in the literature (Viville et al.
2001) that phase separation could cause surface roughness.
A similar correlation of surface roughness to the phase
separation has been reported for tetramethyl bisphenol A
polycarbonate and polystyrene blends (Cabral et al. 2001).
This further confirmed that the imide content increased the
roughness of the surface morphology.
Pressure and imide content dependency of permeability
of PUI hybrid membranes
The permeability and permselectivity values were deter-
mined from pure gas measurements of PUI membranes at
30 °C under various pressures (1–4 atm). Here, we have
studied the effect of various amounts of imide and feed
pressure on the gas transport properties. The permeability
of various types of PUI hybrids are given in Table 2.A
minimal change in N
and O
permeability with penetrant
pressure was observed for a pressure range of 1–4 atm. The
graphical analysis of this data of permeability versus
pressure showed a slight increase for N
and O
gases. In
the case of CO
, it was quite different from other two
gases, such as N
and O
. This may be due to two factors:
(i) More condensable nature of CO
gas. The increase in
pressure increases the adsorption of CO
gas on the surface
of the membrane and thereby diffusion of CO
gas was
more due to more condensable nature of CO
gas compared
to that of N
and O
gases. (ii) The plasticization effect of
gas on the polymer membrane matrices. Reports have
shown that CO
gas molecule plasticizes the polymeric
membranes when there was increase in the pressure and
time (Duthie et al. 2007; Bos et al. 1998; Huang and Lai
For gases such as N
and O
, the permeability slightly
increases in the case of membranes having higher imide
content at higher pressures. This may be due to the intro-
duction of imide and POSS groups and this increases the
chain stiffness which in turn reduces the intrasegmental
mobility. This limits the degree of chain packing by
increasing the chain gap and serving as molecular spacers
and chain stiffeners in the polymer. The other factor that
may contribute to the higher permeability of the membrane
with 20 % of imide content was due to the lower degree of
Fig. 6 AFM image of PUI membranes
Table 2 Permeability properties of PUI membranes
Sample 1 Bar 2 Bar 3 Bar 4 Bar
PU 290 183 1,610 315 201 1,653 322 218 1,801 341 222 1,913
PUI-10 301 205 1,722 327 221 1,791 341 228 1,911 364 234 2,033
PUI-20 322 218 1,801 358 231 1,894 364 241 2,001 408 258 2,178
PUI for environmental and energy-related processes
Author's personal copy
crosslinking. The decrease of the crosslinking degree usu-
ally results in an increase of membrane permeability since
the existence of a crosslinking network restricts the mobility
of the molecular chains. The aggregation of urethane/imide
groups would also have some effect on the gas permeabili-
ties of the membranes. Literature on PUs (Damian et al.
1997; Yoshino et al. 2000; Yang et al. 2004; Lee et al. 2004)
reports that the increase of phase separation between hard
and soft segments leads to the increase in gas permeability
(Fig. 7). The combination of these functional groups (imide,
POSS, and PDMS) and aggregation of urethane and imide
groups contribute to an increase in permeability. But, per-
meability increases in the case of CO
with higher pressures.
For PU, the increase in the permeability value from 290 to
341 Barrer for O
, from 183 to 222 Barrer for N
, and from
1,610 to 1,913 Barrer for CO
were observed. In the case of
PUI-10, the permeability values for O
, and CO
increased from 301 to 364 Barrer, from 205 to 234 Barrer,
and from 1,722 to 2,033 Barrer, respectively. The increase in
the permeability values for O
, and CO
gases from 322
to 408 Barrer, from 218 to 258 Barrer, and from 1,801 to
2,178 Barrer, respectively, for PUI-20.
Selectivity of the PUI membranes
The O
and CO
gas pair selectivities of membranes
under different pressures (1–4 atm) were measured. The
gas pair selectivities of PU, PUI-10, and PUI-20
membranes were found to be in the range of 1.47–1.53,
1.49–1.51, and 1.50–1.55 for CO
, and 8.12–8.30,
8.36–8.79, and 8.33–8.81, respectively. The O
gas pair
selectivity of PU membrane was lower than the other PU
hybrid membranes. For the POSS and the imide-incorpo-
rated membranes, gas pair selectivities increased with
increase in pressure. The incorporation of nonporous inor-
ganic nanoparticles either remains unaltered or decreases
with improved permeabilities as reported in literature (Nunes
et al. 1999; Rios-Dominguez et al. 2006). We have observed
surprisingly that the gas pair selectivities increased with
increase in pressure. The POSS cage molecules in the
membrane matrix leads to less control of sieving small gases
such as N
and O
mainly due to nanogaps created by POSS.
The selectivities of CO
gas pair for PUI-20 of urethane/
imide POSS membranes increases with increase in pressure.
The increase in imide content also leads to an increase in the
The surface morphology and thermal properties of PUI
membranes were characterized using SEM, AFM, and TGA,
and those properties were corroborated well with the per-
meation measurements. The effect of POSS nanoparticle,
rigid imide, and mixed soft segment on gas transport prop-
erties were studied in detail. Separation of CO
is an
emerging technology used to reduce the impact of fossil fuel
combustion. Chemists can play an important role in the
development of this technology and one such major role is
the development of novel polymeric materials for the CO
selectivity. The CO
and N
gas transport properties of a
number of polymeric membranes have been discussed. The
PUI polymers offer very high permeabilities and modest
selectivities, which have lead to excellent gas transport
properties. The gas transport studies of the membranes
confirm that the POSS molecules aid the permeation of
penetrant molecules. The permeation data in this work is to
study the complete transport studies. We do hope that the
complete gas transport study will give a clear idea about the
transport behavior in the urethane/imide POSS membranes.
Acknowledgments D. Gnanasekaran thanks Department of Science
and Technology, New Delhi (No. SR/S1/PC- 33/2006) for the Junior
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PUI for environmental and energy-related processes
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... Zeolite extrudate has an average pore diameter of 3.57-7.81 nm (35.7-78.1 Å), and the kinematic diameter of oxygenate containing in bio-oil was 4-7 Å [45,46]. Therefore, chemical reactions within the internal pore occur due to the pore size of zeolite extrudate relative to the kinematic diameters of oxygenate in bio-oil, which implies there was no significant mass transfer limitation. ...
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Catalytic pyrolysis of palm fronds using zeolite extrudates having different topology (MFI, BEA, and FAU) and SiO2/Al2O3 ratio (1.22–1.86) has been investigated in a fixed bed reactor at 500 °C with catalyst-to-feed ratio (C/F) of 0.16 g/g in comparison with non-catalytic pyrolysis. The gas and bio-oil products of catalytic pyrolysis were correlated to the zeolite topology and acidity. The presence of zeolite extrudate during palm fronds pyrolysis decreased the bio-oil yield while at the same time increasing the gas yield compared to non-catalytic pyrolysis implying simultaneous conversion of bio-oil pyrolysis products into gas-phase products. The bio-oil analysis revealed the presence of furan and aromatics which were absent in the non-catalytic process. Gas-phase product analysis detected a significant increase in CO and CO2 yield implying catalytic pyrolysis promoted decarbonylation and decarboxylation. Among the zeolite extrudates, MFI and BEA-1 were more effective for the deoxygenation reaction at a low C/F ratio (0.16 g/g) because they produced gas containing higher hydrocarbons than FAU and BEA-2.
... †). 36 thus the design of tailored pores regarding the mean path of guest gas molecules and their collisions with the pore aperture remain the most promising gas separation technique. IRHs (6 and 7) pore sizes and shapes, their permanent porosity, and nitrogen-rich surfaces support their preferential CO 2 capture. ...
In the context of porous coordination materials toward CO2 capture and separation, two new metal-organic frameworks termed IRH-6 and IRH-7 were synthesized with square and rhombic microchannel pores, respectively. These materials exhibit high CO2 uptakes of 2.67 mol/kg (IRH-6) and 2.78 mol/kg (IRH-7) at 100 kPa and 298 K. Grand Canonical Monte Carlo simulation demonstrated strong non-covalent interactions between the quadripolar CO2 molecules and these nitrogen-rich frameworks. CO2/CH4 (50:50), CO2/N2 (15:85), and CO2/H2 (15:85) gas mixtures were investigated by the ideal adsorbed solution theory and show excellent CO2 selectivity at ambient conditions for both porous materials. Particularly, a remarkable increase in the CO2 selectivity to 102 (IRH-7) over 31 (IRH-6) was observed for the CO2/CH4 binary mixture, which highlights the effect of pore aperture modification on the preferential CO2 uptake over other conventional gases.
... The ability to selectively remove one component in a mixture while rejecting others describes the perfect separation device [7]. Various materials and methods are being developed for capture and storage, and in some cases, conversion, to mitigate the effect of global warming. ...
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In this article, we studied two different types of polyhedral oligomeric silsesquioxanes (POSS®) functionalized nanoparticles as additives for nanocomposite membranes for CO2 separation. One with amidine functionalization (Amidino POSS®) and the second with amine and lactamide groups functionalization (Lactamide POSS®). Composite membranes were produced by casting a polyvinyl alcohol (PVA) layer, containing either amidine or lactamide functionalized POSS® nanoparticles, on a polysulfone (PSf) porous support. FTIR characterization shows a good compatibility between the nanoparticles and the polymer. Differential scanning calorimetry (DSC) and the dynamic mechanical analysis (DMA) show an increment of the crystalline regions. Both the degree of crystallinity (Xc) and the alpha star transition, associated with the slippage between crystallites, increase with the content of nanoparticles in the PVA selective layer. These crystalline regions were affected by the conformation of the polymer chains, decreasing the gas separation performance. Moreover, lactamide POSS® shows a higher interaction with PVA, inducing lower values in the CO2 flux. We have concluded that the interaction of the POSS® nanoparticles increased the crystallinity of the composite membranes, thereby playing an important role in the gas separation performance. Moreover, these nanocomposite membranes did not show separation according to a facilitated transport mechanism as expected, based on their functionalized amino-groups, thus, solution-diffusion was the main mechanism responsible for the transport phenomena.
Control and reduction of the amount of carbon-dioxide have emerged as one of the main tasks and problems in various fields of industry and production. Therefore, various techniques for treatment of wasteWaste gases have been developed. Membrane technology for flue gas treatmentFlue gas treatment emerged as one of the most promising processes for this purpose. Membrane procedures with different types of membranes have huge advantages in comparison with conventional methods. Treatment of gases with various amounts of carbon-dioxides was tested. Different types of membranes are discussed in this paper, their advantages and disadvantages are described, and some basic properties and mechanism of work are presented. Basic types of membranes (polymeric, carbon, and inorganic) were described. Within each category, properties can be bit fine-tuned by using two different materials of the same type for the synthesis. As a separate category, mixed matrix membraneMixed-matrix membranes that combines good properties of polymer matrix and inorganic dispersed phase have shown better properties in comparison to any other category of membrane is described. Main disadvantages of any type of membranes are sensitivity to heating and cooling cycles and fouling by condensable components, mainly water.
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Green' hydrogen has the attention of many as a possibly large part of the renewable energy transition-as a substitute fuel for natural gas (~98% methane), for vehicular transport, and also for long duration energy storage. But what is 'green' hydrogen, really? Here, we try to assess some of its key elements and issues. DEFINITION: 'green' hydrogen is made in an electrolyzer (reverse battery) by using electrons (e-) from renewable electricity (e.g., from wind turbines and solar panels) to split water (H 2 O) into molecules of hydrogen (H 2) and oxygen (O 2): At Anode: 2 H 2 O → O 2 + 4H + + 4e-At Cathode: 4H + + 4e-→ 2H 2 MAIN ADVANTAGES: Transportable; provides higher energy density than batteries; doesn't produce CO 2 or other (net) greenhouse gases (GHGs) when burned or used in fuel cells. MAIN DISADVANTAGES: Highly flammable; when piped, it leaks through the tiniest cracks; diffuses through plastics; is a strong, indirect GHG. Weight, complexity, and cost of storage often negate most or all of its high energy density advantage, save perhaps at oceanic shipping or utility scales. For energy storage, H 2 is currently expensive and features low round-trip energy efficiency (RTE-from and back to electricity). However, the latter disadvantage might soon be overcome. So, first we assess what that may imply. Assessing one Potentially Large Technical Advance in 'Green' Hydrogen Production For example, a recent article in the respected, peer-reviewed journal Nature, Communications claims at least 95% energy efficiency for its capillary-based electrolyzer. I.e., a basic problem with electrolyzers is bubbling that impedes access to the electrodes. But with this new process, "... water is supplied to hydrogen-and oxygen-evolving electrodes via capillary-induced transport along a porous inter-electrode separator, leading to inherently bubble-free operation at the electrodes." (1) If so, as the initial, well-informed commenter put it, this would be the most significant technical advance in electrolytic hydrogen in the past century. Yet, the same commenter also wondered whether this improved process requires less voltage because KOH (potassium hydroxide), rather than H 2 O, is being stripped of hydrogen. Thus, confirming studies and longer term data are needed to show that the proposed mechanism is correct and that such laboratory results are scalable to gigawatts over a 30 to 40 year plant life cycle. Such data should be forthcoming from a pilot plant study. Still, if we assume the above process works as claimed and is scalable, and also assume (via advanced waste heat recovery methods) an 80% efficient hydrogen fuel cell with ~10% piping losses, then a 95% efficient, hydrogen electrolyzer might potentially yield 68% RTE (0.8 x (1.0-0.1) x 0.95 = 0.68), as opposed to the current maximum RTE for hydrogen energy storage of ~46%. (2) If so, this may cut the levelized cost of storage (LCOS) by more than a third. Yet, such a significant advance may still leave hydrogen storage more costly than liquified air energy storage (LAES) is now, let alone in the foreseeable future. I.e., it seems a tall order, but some forecasters claim that the cost of 'green' hydrogen as a combustible
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Biomass‐derived bio‐oil is a renewable liquid fuel that contains a high amount of oxygen with a low calorific value. Hydrodeoxygenation (HDO), as one of the methods to increase the calorific value of bio‐oil, was conducted in an autoclave‐type reactor at 250 °C with an initial H2 pressure of 20 bar for 4 h using Ru/C and Pd/C catalysts with a metal precursor loading of 1, 3, and 5 wt.%. The HDO reaction using Ru(5 %)/C had a higher degree of deoxygenation (47 %). A higher yield (78 wt.%) of the oil phase was produced after the reaction using Pd(3 %)/C. The HDO reaction using Ru(5 %)/C and Pd(3 %)/C catalysts could increase the calorific value of bio‐oil from 23.3 to 29.8 and 28.5 MJ/kg, respectively. HDO of palm kernel shells derived bio‐oil over Ru/C and Pd/C catalysts with a metal precursor loading of 1, 3, and 5 wt.% could decrease 12,8% of oxygen content and reach 29.76 MJ/kg of calorific value in the oil phase. The yield of the oil phase reached 78 %. Both catalyst types have higher catalytic activity for deoxygenation than hydrogenation, with the degree of deoxygenation (DOD) varying between 38–47 %.
This chapter contains sections titled: Introduction Experimental Results and Discussion Conclusions
The environmental pollution, toxicity, and rising cost of conventional lubricants lead to renewed awareness in the improvement of environmentally friendly bio-lubricants. Due to the negative impact (low biodegradability and more toxicity of mineral and synthetic) on the environment, there has been a stable increase in the demand for biodegradable and eco-friendly bio-lubricants. Perhaps, mineral oils pollute the atmospheric air, soil, and drinking water and disturb people’s life and plants to a greater level. However, the major problem leads to the exhaustion of the world’s crude oil, increasing crude oil prices, and problems connected to preservation have brought about renewing or reusing awareness in the use of biodegradable lubricants. Definitely, oils of natural ester are capable as a base stock for environmentally friendly bio-lubricants due to its lubricity, biodegradation capability, viscosity vs. temperature characteristics, low evaporation capacity, etc. The chapter covers the biodegradable mechanism, toxicity ration, and eco-friendly natures of natural esters of vegetable oils.
Development of new and improvement of the existing materials for carbon dioxide (CO2) capture is an urgent and significant goal for emission reduction. We hereby report synthesis of hybrid urethane-imide-based poly-ILs (HPILs) and their CO2 capture capacities. The synthesized HPILs were characterized by FTIR, NMR, DSC, TGA, DMTA, AFM. CO2 physisorption and reusability were assessed by the pressure-decay technique at a few conditions. Density functional theory calculations were used to identify binding energies between CO2 and each center of HPILs. Cations of HPILs play an important role in CO2 physisorption. The impact of the silane content was found to be relatively insignificant. Weakly coordinating cations foster better CO2 sorption. The best performances were obtained for the tetrabutylammonium-based HPILs (33.1mg/g in HPIL 02 TBA and 31.7 mg/g in HPIL-06-TBA at 303.15 K and 0.82 bar). HPIL 02-TBA possesses the highest CO2 sorption capacity out of all reported poly(ionic liquids) thus far and exhibits interesting thermal stability and competitive mechanical properties. Application of HPIL 02-TBA will lead to more robust CO2 capturing setups.
This chapter describes the gas barrier and dielectric properties of nanostructure polymer blends. More particularly, it relates to the incorporation of nanostructured fillers such as polyhedral oligomeric silsesquioxane (POSS) and layered silicate clays in a polymer matrix. The resulting nanostructured polymers show improved gas barrier and dielectric properties. Such properties are useful in the production of lightweight transportation bodies in the automotive industry, high-performance in the packaging industry. The dispersion of nanoparticles into a fully intercalated state is dependent on the properties of the nanoparticles and the polymer matrix. The properties of ethylene-vinyl acetate (EVA) and polyamides, nanostructured blends of EVA, nanostructured polyamide blends and POSS-blended nanostructured polymer are discussed in detail.
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The synthesis and characterization of N-propyl-POSS-7-oxanorbornene-5,6-dicarboximide (NPONDI) and N-3-(tri-fluoromethyl)phenyl-7-oxanorbornene-5,6-dicarboximide (TFNDI) was reported. The synthesis of the POSS-based (co)polymers were accomplished by ring opening metathesis polymerization (ROMP). The monomers and polymers were characterized using FT-IR, 1 H-, 13 C-, 29 Si-NMR, and GPC techniques. Thermal properties of TFNDI-NPONDI copolymers were evaluated by differential scanning calorimetry (DSC) and thermogravimetric analysis (TGA). Transmission electron microscopic (TEM) analysis of optically transparent and flexible copolymer films revealed the presence of 50 nm-sized POSS agglomerates. Atomic force microscopy analysis of the film surface exhibited a modest increase in surface roughness of TFNDI-NPONDI copolymers as compared with homopoly[N-3(trifluoromethyl)phenyl-7-oxanorbornene-5,6-dicarboximide] (HTFNDI). The POSS incorporated polymers such as 1NPONDI, 2NPONDI, and 3NPONDI increased the hydrophobicity as compared with HTFNDI. This was measured by static contact angle analysis. The study focussed on the dispersion, surface morphology, and the microstructure of POSS in TFNDI-NPONDI copolymer as determined by scanning electron microscopy (SEM).
Poly(ethylene oxide)-segmented polyurethanes (PEO-PUs) and polyamides (PEO-PAs) were prepared, and their morphology and CO2/N2 separation properties were investigated in comparison with those of PEO-segmented polyimides (PEO-PIs). The contents of the hard and soft segments in the soft and hard domains, WHS and WSH, respectively, were estimated from glass-transition temperatures with the Fox equation. The phase separation of the PEO domains depended on the kind of hard-segment polymer; that is, WHS was in the order PU > PA ≫ PI for a PEO block length (n) of 45–52. The larger WHS of PUs and PAs was due to hydrogen bonding between the oxygen of PEO and the NH group of urethane or amide. The CO2/N2 separation properties depended on the kind of hard-segment polymer. Compared with PEO-PIs, PEO-PUs and PEO-PA had much smaller CO2 permeabilities because of much smaller CO2 diffusion coefficients and somewhat smaller CO2 solubilities. PEO-PUs also had a somewhat smaller permselectivity because of a smaller solubility selectivity. This was due to the larger WHS of PEO-PUs and PEO-PAs, that is, a greater contamination of PEO domains with hard urethane and amide units. For PEO-PIs, with a decrease in n to 23 and 9, WHS became large and CO2 permeability decreased significantly, but the permselectivity was still at a high level of more than 50 at 35 °C. © 2000 John Wiley & Sons, Inc. J Polym Sci B: Polym Phys 38: 1707–1715, 2000
We report the first observation of bulk spinodal decomposition in polymer blends using atomic force microscopy (AFM). The fracture of a phase-separated thick film of tetramethyl bisphenol A polycarbonate (TMPC) and polystyrene (PS) is shown to induce a surface roughness that is resolvable by AFM. The resulting topography reproduces the spinodal morphology and is analyzed quantitatively. We investigate simultaneously the surfaces and bulk of the TMPC/PS films, a blend known to exhibit surface-directed spinodal decomposition. The structure factors obtained from a 2D-FFT of “bulk” AFM images and from time-resolved light scattering (LS) do not coincidethis is discussed in terms of the 2D (AFM) and 3D (LS) analysis involved. We finally compute general expressions relating 2D and 3D structure factors for a number of structures relevant to phase separation phenomena.
Copolymers based on styrene and a nanostructured polyhedral oligomeric silsesquioxane, PSPOSS, were synthesized and their gas permeability coefficients, P(i), to O2 and N2 were measured at 2.0265×105Pa (2atm) and 35°C in a standard permeation cell. The syntheses of the copolymers were carried out using styrene and different loads of the macro initiator POSS–TEMPO which was also synthesized in this work. The gas transport results show that the gas permeability coefficients in the PSPOSS polymers increases with the amount of the POSS–TEMPO used in the synthesis, but interestingly, for relatively low concentrations, i.e. up to 10wt.%, the selectivity for the gas pair O2/N2 does not show dramatic losses in the selectivity. The P(O2) for pure PS, which is 21.75145×10−18m2s−1Pa−1 (2.9Barrer) with 5.6O2/N2 selectivity, increases to 37.5025×10−18m2s−1Pa−1 (5.0Barrer) and the selectivity still remains as high as 5.2 for a PSPOSS synthesized with a 10wt.% load of the macro initiator. When the PSPOSS is synthesized with higher loads of the macro initiator, i.e. 20wt.%, there are impressive increases in permeability with decreases in the O2/N2 selectivity. After factorization of the permeability coefficients into the diffusivity and solubility factors, it is observed that having POSS units in the copolymer affect the perm-selectivity of the PS membranes. This effect can be attributed to changes in the gas diffusivity rather than changes in the solubility coefficients for PS synthesized with up to 10wt.% of POSS–TEMPO. Higher loads of the POSS–TEMPO in the PSPOSS membranes increase both the diffusivity and selectivity coefficients.
Gas separation by selective permeation through polymer membranes is one of the fastest growing branches of separation technology. Strong interest exists, therefore, in the synthesis of new polymers that exhibit both higher gas permeabilities and selectivities than presently available polymers. Such new polymers, in the form of asymmetric or “composite” membranes, are required in order to improve the economics of extant membrane processes for gas separations and to develop new processes. A considerable amount of information has been available for many years on the permeabilities and selectivities of a large variety of polymers to different gases. However, since most of these polymers were structurally unrelated, syntheses of new polymers for gas separations was based largely on trial and error and previous experience. It is only in recent years that the structure/permeability/selectivity relationships of polymers have become the object of systematic studies. The present review examines the progress made in the understanding of these relationships, with emphasis on selected rubbery and glassy polymers. Some of the most important theoretical models of gas transport in polymers are also reviewed. The potential usefulness of computer simulation techniques for predicting polymer structures that enhance penetrant gas mobility and selectivity is discussed. Finally, conjectures are offered as to possible advances in membrane separations of gaseoous mixtures in the coming decade.
Various polyurethane (PU) and hybrid organic-inorganic networks based on isocyanate chemistry were synthesized using a two-stage method. All the networks were amorphous. For PU membranes the morphology and the permeability coefficients of different gases (H2 ,N 2 ,O 2) were a function of the polarity and the chain length of the soft segment and a function of the composition of the networks. The membranes based on the same soft segment chain length and on the same molar composition were structurally nanoheterogeneous systems for the less polar soft segments (a,v-hydroxy- terminated hydrogenated polybutadiene and a fatty acid oligoester). They were homo- geneous for a polycaprolactone type soft segment. The gas diffusion was appreciably hindered in the case of better miscibility between the soft chains and the hard cross- links. Decreasing the soft segment length decreased the gas permeability coefficient of the network. As the chemical compositions were changed by increasing the soft segment content, an increase in permeability coefficients was observed. The morphology and transport properties of PU networks and hybrid organic-inorganic networks with low inorganic content were compared for the same soft segment content. The similarities observed between the two types of networks led us to conclude that the organic or inorganic nature of the crosslinking agent has no influence on the gas transport proper- ties of these networks. q 1997 John Wiley & Sons, Inc. J Appl Polym Sci 65: 2579-2587, 1997
The role of surface transport in the passage of a gas at low pressure through fine tubes or pores is examined in terms of simple models of mobile and localized adsorption. The amount of surface transport becomes about equal to the amount of gas transport when the tubes or pores have radii of the order of several hundred Angstrom units. The theory predicts that surface transport will have little effect on the pressure gradient across the tube or pores in the absence of a temperature gradient. But the pressure gradient should be increased considerably, as a result of surface transport, over the usual (thermal transpiration) pressure gradient when there is a temperature gradient across the tube or pores.
Phase separation in blends of bisphenol A polycarbonate and poly(methyl methacrylate), PC/PMMA, is investigated on the microscopic scale by means of atomic force microscopy (AFM). This technique allows the visualization of the early stages of phase separation with greater accuracy, relative to optical techniques. In comparison to previous data, the AFM-determined demixion vs composition curve appears to be shifted to lower temperatures. Starting from homogeneous thin films, we then follow the thermally induced spinodal decomposition process of 50/50 blends and characterize the morphological changes as a function of demixion time and annealing temperature. We present a quantitative investigation of the growth of the dispersed phase, based on a statistical power spectral density analysis of the AFM data. The interest of this method is to provide information on the growth mechanism, by establishing the scaling relationships between the topographic roughness (which is due to phase separation), the length scale of observation, and the annealing time. In the present case, the phase separation process appears to follow the Kardar−Parisi−Zhang universality class of growth, in which the density is not a conserved quantity. The corresponding morphology is accordingly marked by a clear topographic discontinuity between the PMMA-rich domains and the PC-rich matrix. We also observe that, at temperatures exceeding 220 °C, the late stages of the spinodal decomposition process are strongly affected by the occurrence of chemical reactions between PC and PMMA, which slow the growth rate of the dispersed phase and the surface roughening.
Gas-selective polymer membranes have long been used in industrial applications. Studies of polymers with well-defined flexible phenyl ether segments such as 1 should contribute to the understanding of the selection mechanism and thus ultimately lead to the synthesis of optimized membrane materials. Various different bridging groups X were used in the studies.