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Modern H2-based energy storage and conversion devices require a polymer electrolyte membrane (PEM) fuel cell–based integrated power system with synergistic heat integration. The key issue in integrated power systems is developing a PEM that can operate at 200–300 °C. However, currently used phosphoric-acid-based high-temperature PEM fuel cells limited stability at higher operating temperatures. Herein, we introduce a cerium hydrogen phosphate (CeHP) PEM that conducts protons above 200 °C through a self-assembled network (SAN). The SAN-CeHP-PBI reached maximum power densities of 2.4 W cm-2 and operate stably for over 7000 minute without any voltage decay at 250 ℃ under H2/O2 and anhydrous conditions. The developed fuel cell can be combined with an external hydrogen generator that uses a liquid hydrogen carrier such as N-ethylcarbazole and methanol as fuel, thus achieving a high energy efficiency. The thermal stability and fuel flexibility of these SAN-CeHP-PBI demonstrate potential for commercial applications.

Public transit vehicles such as buses operate within shared transportation networks subject to dynamic conditions and disruptions such as traffic congestion. The operational delays caused by these ...

Adsorption equilibria and kinetics of CO2, CO, and N2 on carbon molecular sieves (CMSs) were measured by a gravimetric method at temperatures of 298, 308, and 318 K and pressures up to 10 bar. The validity of the experimental isotherms and kinetics was confirmed by comparing with experimental results from an additional volumetric method. Experimental adsorption isotherms were well correlated with a temperature-dependent Sips model and the results were compared with the Langmuir and Sips models. The order of the adsorbed amounts and isosteric heats of adsorption were CO2 > CO ≥ N2 and their heats of adsorption changed from vertical interactions to lateral interactions with an increase in loading amount. The adsorbed amounts and heats of adsorption were lower for the CMSs than those of activated carbon, which has higher surface area and pore size. The microporous diffusional time constants (Dμ/r2) of CO and N2 could be obtained from an isothermal kinetic model, while a non-isothermal kinetic model was required for CO2 due to its higher heat of adsorption and adsorption rate. In addition, the variation in Dμ/r2 with surface coverage were well correlated by the Darken relation combined with Sips isotherm model, and a steep variation was observed from a surface coverage of 0.2 in all the components. The adsorption rate was highly affected by the electrical properties of the adsorbate rather than kinetic diameters. The order of adsorption rate was CO2 ≫ CO > N2, while the order of the activation energies in the Arrhenius equation was opposite. The validity of obtained equilibria and kinetics results was confirmed by comparing the experimental breakthrough curves and dynamic simulation results in a CMS bed.

We report the fabrication and catalytic performance evaluation of highly active and stable nickel (Ni)-based structured catalysts for ammonia dehydrogenation with nearly complete conversion using nonprecious metal catalysts. Low-temperature chemical alloying (LTCA) followed by selective aluminum (Al) dealloying was utilized to synthesize foam-type structured catalysts ready for implementation in commercial-scale catalytic reactors. The crystalline phases of Ni-Al alloy (NiAl

The equilibria and kinetics of CO2, N2, and H2O on KOH-treated activated carbon (KOH-AC) were evaluated. The isotherms for the pure components were correlated with the Langmuir, dual-site Langmuir,...

Efficient fleet configuration is a critical problem for air carrier management. This study is primarily concerned with empirical aircraft operating costs and examines the optimal fleet adapted to numerous flight routes longer than 1000 nautical miles. An aircraft-specific operating cost model is derived to estimate market average direct operating costs (DOC) of 22 aircraft types operated by 22 US airlines. It is used as a base in a fleet configuration optimization model to figure out the variability of optimal fleets for segment markets of varying sizes and lengths as well as in response to the dynamics of market circumstances. While recognizing the superior fuel burn performance of narrow-body aircraft such as Boeing 737 and Airbus A320 series, we find operating cost efficiency of wide-body aircraft (B777 and A330 series) due to the economies of scale in the non-fuel operating costs associated with aircraft size. There is a possible reduction of DOC by substituting the wide-body aircraft for smaller ones that are dominant in the current US domestic markets. And the cost efficiency of the wide-body fleet is more robust in dense and longer distance markets (particularly longer than 2000NM), especially considering fuel price fluctuations. Finally, the optimal fleet analysis with empirical traffic data suggests a mixed-size aircraft fleet, configured with narrow- and wide-body aircraft, as an alternative for a wide range of segment markets that vary in size and length.

This study comprehensively investigates hydrogen production from green ammonia reforming, including synthesis of catalysts, reactor development, process integration, and techno-economic analysis. In-house developed Ru/La–Al2O3 pellet catalyst having perovskite structure showed high catalytic activity of 2827 h−1 at 450 °C and stability over 6700 h at 550 °C, exceeding the performance of the majority of powder catalysts reported in the literature. A scalable 12-faceted reactor adopting the as-produced catalyst was designed to enhance heat transfer, producing over 66 L min−1 of hydrogen with state-of-the-art ammonia reforming efficiency of 83.6 %. Near-zero CO2 emission of hydrogen extraction from green ammonia was demonstrated by-product gas recirculation as a combustion heat source. A techno-economic assessment was conducted for system scales from 10 kW to 10 MW, demonstrating the effect of reduced minimum hydrogen selling prices from 7.03 USD kg−1 at small modular scales to 3.98 USD kg−1 at larger industrial scales. Sensitivity analyses indicate that hydrogen selling prices may reduce even further (up to 50 %). The suggested hydrogen production route from green NH3 demonstrates superior CO2 reduction ranging from 78 % to 95 % in kg CO2 (kg H2)−1 compared to biomass gasification and steam methane reforming. These findings can be used as a basis for following economic and policy studies to further validate the effectiveness of the suggested system and process for H2 production from NH3.

Integrated gasification combined cycle (IGCC) plants that are also capable of CO2 capture have received significant attention as the next generation of coal-based power plants for the co-production of H2 and electrical power. Accordingly, for a cost-effective and environmentally friendly poly-generation IGCC process, efficient techniques need to be developed to recover H2 from the syngas of an IGCC plant with carbon capture. In this study, an eight-layered bed pressure swing adsorption (PSA) process using activated carbon and zeolite simultaneously was developed to produce high purity H2 from the H2-rich syngas of an IGCC plant. As a first step, the separation performance was compared between four-and eight-layered bed PSA processes. The eight-layered bed PSA process led to higher recovery of H2 at the condition of a similar H2 purity owing to a greater number of pressure equalization steps in the operational step configuration. It is noteworthy that the productivity could be greatly improved as the purge gas was replaced from the product gas to residual gas in a bed. When the adsorption bed was purged by using the residual gas after the first pressure equalization step, recovery improved by about 3 ∼ 6 % at the condition of 99.99+ mol% H2 purity in comparison with the product-purge PSA configuration. On the other hand, the highest H2 recovery that could be obtained for the requirement of 99.99 mol% H2 purity, was ∼ 89.7 % from the eight-layered bed H2 PSA process when the purge gas was provided from the residual gas of the adsorption bed after the last depressurization pressure equalization step. However, as the concentration of CO in the desired H2 product was higher in the PSA configuration when using residual gas compared to the product gas, the operational configuration of PSA needed to be decided by the desired H2 purity and impurity constraints for application. Furthermore, the tail gas from the PSA contained 45–66 mol% of H2 and CO, depending on the applied PSA configurations, and could be used to drive a gas turbine without any loss of the syngas, even though the recompression energy loss required evaluation.

Ammonia (NH3) has been proposed as a viable hydrogen (H2) carrier, but high reaction temperature and endothermic nature of NH3 decomposition require an efficient reaction system to maximize useable energy from NH3. Adoption of carbon-free heat sources and efficient heat transfer to the reaction bed are crucial for sustainable H2 release. Herein, the autothermal recirculating reactor (ARR) concept with the fractional utilization of the reformate H2 as a clean combustion fuel is proposed and experimentally investigated. Additionally, BN-coated Cu as a composite reactor material is developed for heat transfer enhancement of high-temperature H2 release reaction in a thermally-coupled NH3 decomposition and H2 combustion system. Coating performance against chemical degradation of Cu has been tested and confirmed. High NH3 conversion of >99.6% and reforming efficiency of 70.95%, even with high fraction of heat loss owing to small scale validation, show feasibility of the as-proposed reformer. Operation of the suggested system is envisaged with self-sustained heat supply for production of 84 W of electrical power. Also, the as-proposed reactor concept and material are suggested to serve in other endothermic H2 release reactions from various H2 carriers (methane, methanol, LOHC, etc) for potential application in power generation as well as high-purity H2 production.

Understanding separation behavior in an adsorption bed is crucial for well-designed adsorption processes. Since adsorption phenomena depend on temperature, thermal parameters, such as the internal heat transfer (hi), isosteric heat of adsorption (Qst) and axial thermal conductivity of the bed (Kw), can affect the adsorption dynamics and performance of the bed. In this study, the effects of these thermal parameters on the adsorption dynamics and breakthrough curves were analyzed with the experimental results using integrated gasification combined cycle gas from the carbon capture process (IGCC gas; H2:CO:N2:CO2:Ar = 88:3:6:2:1 mol%) as a purification gas and blast furnace gas (BFG; H2:CO:N2:CO2 = 20:0.1:44.5:35.4 mol%) as a bulk separation gas. The results were then compared with the isothermal and adiabatic results. Considering the variation of the internal heat transfer coefficient and isosteric heat of adsorption along with the propagation of gas in the bed, the temperature profiles inside the bed could be predicted better than in the case using constant values. The axial thermal conductivity of the bed significantly affected the temperature profiles as the temperature excursion was sharp. In the prediction of breakthrough curves, these variable thermal parameters could be replaced by suitable constant values estimated from experimental and theoretical approaches when well-fitted isotherm parameters were applied considering the partial pressure of each component in the feed.

The sorption equilibria and kinetics of CO2, N2, and H2O on polyethyleneimine (PEI)-impregnated silica (PEI–silica) were studied to determine CO2 capture by temperature-swing adsorption (TSA). The experimental isotherms of CO2 were correlated well by the dual-site Langmuir (DSL) model while those of H2O were well-predicted by the Brunauer–Emmett–Teller (BET) model. The amounts of the components adsorbed at equilibrium were in the order of q H 2 O > q C O 2 ≫ q N 2 . The isosteric heat of adsorption (Qst) of CO2 on PEI–silica changed from 70 to 55 kJ/mol along the sorption amount. The highly enhanced adsorption affinity of PEI–silica for CO2 resulted in chemisorption, while the adsorptions of H2O and N2 exhibited typical physisorption. PEI–silica exhibited higher selectivity than KOH-treated activated carbon (KOH–AC) for the simulated flue gases, i.e., the mixture of CO2 and N2. Although PEI–silica became hydrophobic, the H2O molecules were expected to affect the CO2 capture process because of their high adsorption amount and rate. The variation in the non-isothermal kinetic behavior of CO2 caused by pressure differed from that of H2O because of the difference between chemisorption and physisorption. PEI–silica exhibited a high CO2-sorption capacity of 2.3 mmol/g (pure CO2 at 70 °C) with a high sorption rate (>90% of saturation within 1 min). Compared with the cyclic test that employs desorption in hot N2, the working capacity decreased more when the desorption was conducted in hot CO2 flow.

Herein, we report the use of a MgCeOx-supported Cu (MgCuCe) catalyst with a unique bead structure to augment the water-gas shift (WGS) reaction. The MgCuCe catalyst exhibited an exceptionally high reaction rate of 83 μmol g−1 s‒1 at 300 °C, compared with that without MgO (30 μmol g−1 s‒1). Very few studies have focused on MgO-supported catalysts owing to the reports on the inferior activity of MgO. However, this paper reports unprecedented enhancements by introducing MgO and illustrates the WGS reaction mechanism: (1) numerous defects promoted water dissociation and subsequent associative mechanism; (2) the labile oxygen in MgO participated in redox mechanisms. The hydrogen production cost realized due to the use of the MgCuCe was 0.63 USD/kg H2, which is lower than that achieved by using commercial and CeO2-supported catalysts. This study paves the way for exploiting earth-abundant MgO in developing efficient catalysts and contributes to reducing H2 production costs.

The demand for clean energy sources has made H2 recovery from various lean hydrogen mixtures increasingly attractive. In this study, parallel and series pressure swing adsorption (PSA) processes were investigated experimentally and theoretically, and > 99% pure H2 was produced from a lean hydrogen mixture (H2:CO:N2:CO2 = 19.9:0.1:44.6:35.4 mol%) at 10 bar. A mathematical model for a PSA process using activated carbon and zeolite 13X was simultaneously validated with results from breakthrough experiments and a parallel two-bed PSA process. The parallel two-bed PSA process using a layered bed (lower bed: activated carbon, upper bed: zeolite 13X) experimentally produced H2 with a purity of 94.6–98.3% and a recovery of 33.5–63.2%; CO was not detected in the H2 product. In the parallel four-bed PSA process, the H2 recovery was drastically increased to 77.3% due to an additional pressure equalization step, but the increase in H2 purity was minute. The series PSA process, which was divided into the bulk separator and the purifier, was theoretically studied under various operating conditions. The series three- and four-bed PSA processes could produce H2 with over > 99% purity and a recovery of 62.478% and 82.643%, respectively, due to the additional pressure equalization step and the utilization of blowdown gas. The parallel four-bed PSA process showed the highest H2 productivity (33.58 molH2 kgads−1 day−1), while the series four-bed PSA process achieved an H2 productivity of 23.96 molH2 kgads−1 day−1 with > 99% H2 purity.

Composite metallic membranes comprising Pd coated on group 5 elements such as V, Nb, and Ta are actively explored as a promising material for hydrogen permeable membrane. However, such composite membranes are known to suffer from performance degradations owing to excessive surface fouling due to inter-diffusion between Pd and group 5 elements at high temperatures. In this study, mechanically stable Pd/Ta composite membranes are fabricated, and their H2 permeation flux degradation rates and mechanism of membrane degradation are investigated. Fabricated membranes had full coverage of Pd on Ta surface, with less than 5 wt% of impurities. H2 permeation rates of Pd/Ta membrane samples with different Pd and Ta thicknesses are evaluated at temperatures from 450 °C to 650 °C for a prolonged period of 20–100 h. Over the tested period, degradation in H2 permeation rate was 5% or higher, with temperature being a dominant factor. SEM, TEM, and XRD analyses of the surface and cross-sectional morphology, compositions, and crystallinity reveal that the main degradation mechanism of the composite membrane is the inter-diffusion between Pd and Ta leading to the formation of intermetallic compounds as well as morphology change of the catalytic layer. By evaluating the exponential factor in Sievert’s equation over the degradation period, it was found that the diffusion mechanism does not change over time, confirming that the bulk diffusion mechanism is affected by the inter-diffusion. H2 flux degradation was less prominent at lower temperatures with thicker Pd catalytic layers.

This paper is primarily concerned with the accessibility of airports located in small and geographically isolated communities. Specifically, it carries out a sensitivity analysis to derive rates of change for the parameters of a spatial interaction model applied to empirical air passenger trip data, and interprets the results focusing on the local airports subsidized by the Essential Air Service program. An empirical trip based accessibility measure is developed for individual airports in the contiguous US air transportation system. The measure enables us to capture the distinctive roles of small airports, which primarily function as regional associates of nearby cities and entrances for long-haul trips via major hub(s) to continental-scale connections. We observe the geographic and temporal variability of accessibility among airports, regarding the external factors including the dynamics of air carriers’ routing schemes, as well as global and local circumstances. Their impacts on passenger journey lengths are substantial at the local airports due to the few available connections. This issue has received less attention in existing subsidy program assessments. Furthermore, we explore the geographic distribution of non-subsidized local airports showing similar accessibility conditions. This paper enhances prior development by showing that the rates of change in accessibility scores are largely stable over recent national air passenger data.

Summary Hub-and-spoke networking is a key feature of current aviation markets in which hubs, as connecting points, function to consolidate and redistribute flows. This indicates that observation of traffic on a segment does not necessarily convey information about the origin to destination routing of passenger journeys because of the unavoidable detours in the system. This paper examines the heterogeneity of the flow composition in domestic and international US markets, which in turn allows us to observe the variation of operations across major hubs. A modified Route Flow Estimator for origin–destination synthesis (or origin–destination matrix estimation) is designed to decompose the segment traffic into itinerary-based passenger trips. Several public and commercial databases, which are easily accessible, are exploited (and reconciled) for the model in order to (i) generate possible trip itineraries using those segment markets, and (ii) link data-driven operational conditions with the underlying segment flows. The results are validated with US domestic trip observations and empirical knowledge related to the air transportation system. Then, the variability of the hub operations is examined based on sensitivity tests using the model parameters. From the resolution of itinerary-based estimates, we observe that major airports' hub operations are spatially uneven, particularly with respect to domestic and international connecting passengers. Copyright © 2017 John Wiley & Sons, Ltd.

The adsorption equilibria and kinetics of CO 2 , CO, N 2 , CH 4 , Ar and H 2 on zeolite 13X were measured via the volumetric method at 293, 308 and 323 K and up to 1.0 MPa. Adsorption isotherms and the heat of adsorption were analyzed over a full range of pressures. Each experimental isotherm was correlated with Langmuir, Sips and temperature-dependent Sips models, with the deviations for each model being evaluated. The Sips model showed a smaller degree of deviation from the experimental data than the Langmuir model. The isosteric heat of adsorption sequence was H 2 4 ≒ N 2 2 along with surface loading. The experimental uptake curves were correlated with a non-isothermal kinetic model because the adsorption kinetics was controlled via heat generation and transfer. Adsorption rates of the gases on zeolite 13X were affected by the isosteric heat of adsorption, heat transfer rate and adsorption affinity. At the same temperature and pressure, the sequence of reciprocal of the effective diffusional time constant ( D / R P 2 ) revealed the following sequence: CH 4 ≒ N 2 2 , showing pressure and temperature dependency. While the diffusion rates of CO and N 2 were controlled via micropore diffusion, CO 2 and CH 4 were significantly affected by macropore diffusion due to high heat transfer resistance. Compared to experimental results between the powder and pellet forms of zeolite 13X, the zeolite pellet binders led to a reduction in adsorption capacity and heat of adsorption. However, the difference in adsorption kinetics was relatively minute.

The adsorption equilibria of water vapor on zeolite 3A, zeolite 13X, and dealuminated Y zeolite (DAY) were measured using a volumetric method. Equilibrium experiments were conducted at 293.15, 303.15, and 313.15 K and at relative pressure (P/Ps) up to 0.95. Experimental data were correlated using Aranovich–Donohue and Frenkel–Halsey–Hill models, using Langmuir, Toth, UNILAN, and Sips isotherms.

Biphenyl-based eutectic mixture (BPDM, 35 wt% Biphenyl, and 65 wt% Diphenylmethane) has gained attraction as a strong candidate for liquid organic hydrogen carriers (LOHC) particularly due to the high hydrogen capacity (6.9 wt%). To take full advantage of its capacity, facile and high-extent dehydrogenation with reversibility is the key, where the appropriate selection of supports in heterogeneous catalysts plays a crucial role. Herein, the effect of the properties of commercial Al2O3 pellets in the dehydrogenation reaction of a hydrogenated biphenyl-based mixture (H12-BPDM) over Pt/Al2O3 catalysts is investigated. H2 production rate, 10 h performance tests, and product composition from the dehydrogenation of H12-BPDM are evaluated with the in-house catalytic screening tests using continuous fixed-bed reactors. Catalyst characterization and product analysis suggest that pore size distributions and corresponding surface properties of Al2O3 supports can lead to different dehydrogenation reaction characteristics of H12-BPDM. This study provides a rationale for the proper support selection for efficient utilization of BPDM as a LOHC.

For catalytic reactions involving H2 extraction, the membrane reactor is an attractive option for enhancing the equilibrium and kinetics while eliminating excessive purification steps. In this study, a steam carrier adopted composite membrane reactor system is developed to produce pure H2 (>99.99%) from ammonia with high H2 productivity (>0.35 mol-H2 gcat−1 h−1) and ammonia conversion (>99%) at a significantly reduced operating temperature ( 91%) while replacing conventionally utilized noble carrier gases that require additional gas separation processes. The steam carrier presents similar membrane reactor performance to that of noble gases, and the water reservoir used for steam generation acts as an ammonia buffer via scrubbing effects. Finally, electricity generation is demonstrated using a commercial fuel cell along with process simulation, substantiating potential of the proposed membrane system in practical applications for H2 production from ammonia and on-site power generation.

As one of hydrogen purification techniques, membrane separation has a significant potential to directly obtain high-purity hydrogen from the mixed gas produced from various catalytic reactions. Specifically, dense metallic membranes exhibit several advantages including good mechanical strength under pressurized conditions, thermal stability, and high hydrogen selectivity. Conventionally, their permeation behavior is predicted from a numerical model known as the Sievert's law, which describes diffusion of hydrogen atoms through a metal layer. This study questions the validity of previous permeability trends of the Pd/BCC composite membranes and reveals the importance of surface reactions that significantly affect the permeation behavior of such membranes. A new permeation model developed, considering both the surface reactions at the catalytic layers and bulk diffusion through the metal layers, exhibits good correlation with the experimental permeation characteristics of the Pd/BCC composite membranes. Moreover, the diffusivity coefficients of BCC metals as a function of temperature is determined with higher accuracy than those reported in previous studies having temperature range inconsistency between hydrogen solubility and diffusivity. The experimental data along with the proposed model successfully accounts for the unique permeation characteristics of BCC metal membranes coated with catalytic layers and advances fundamental understanding of the permeation characteristics of the composite membrane, thereby accelerating the adoption and application of the composite membrane permeation model.

The adsorption uptake curves of CO2, CO, N2 and CH4 on zeolite LiX and activated carbon were measured using a volumetric method at 293, 308 and 323 K and pressure up to 100 kPa. The experimental uptake curves were correlated with a non-isothermal kinetic model because the adsorption kinetics was controlled by heat generation and transfer, and an isothermal model showed large deviation from experimental uptake. The adsorption rates of the gases on zeolite LiX and activated carbon were affected by the isosteric heat of adsorption, heat transfer rate and adsorption affinity. At the same pressure and temperature, the sequence of effective diffusion time constants was CO2 ≪ CO

Mesoporous MgO·KNO 3 composites were developed using an aerogel method for CO 2 sorption in the intermediate temperature range of 250–400 °C. The effects of MgO/KNO 3 molar ratio, calcination method and sorption temperature on CO 2 sorption rate and capacity were evaluated using a thermogravimetric analyzer. The composite prepared at a MgO/KNO 3 molar ratio of 1:0.2 with a four-step calcination had the high CO 2 sorption capacity of 13.9 wt% at 325 °C and 120 min, showing about 70% of the total sorption capacity within 10 min and about 7 times higher sorption capacity than pure MgO. In addition, the developed MgO·KNO 3 composite showed higher sorption capacity than other MgO composites promoted by alkali metal salts (K 2 CO 3 , KOH, NaNO 3 , Na 2 CO 3 , Na 2 HPO 4 , LiNO 3 and Li 2 CO 3 ). The sorption rate of CO 2 on a MgO·KNO 3 composite during the initial 30 min was on the order of 10 − 4 /s. Sorption working capacity was evaluated by 12 cyclic tests at 325 and 375 °C for sorption (20 min) and 450 °C for regeneration (30 min). Sorption working capacity was higher at 325 °C than at 375 °C, but MgO/KNO 3 was highly stable at 375 °C, showing 90 wt% of the first cycle.

Aircraft fuel consumption is a very large component of airline costs. Fuel burn is also very important because it is highly correlated with emissions and contributes directly to transport externalities. This paper calibrates fuel burn in kilos per seat per nautical mile for aircraft using the EMEP/EEA aircraft inventory database. We then employ the model with OAG flight schedule data to evaluate fuel burn by flight routes and aircraft types at a global scale. The paper shows comparative fuel use among different distance based markets as well as among a variety of routes in the long-haul market. The results show geographical heterogeneity of fuel burn rates among a variety of routes, while controlling for seat configuration and stage distance. The paper finds that stage lengths centered on 1500–2000 NM have the lowest fuel burn rates under current technology, fleet composition, and seat configuration. These findings, together with comments on the viability of long range flights provide better understandings not only for the carbon taxation debates but also for operational efficiency of current aviation markets. The lower rates for moderate distance flights seems to favor networks without extreme links, and supports the use of a hub connection scheme.

The adsorption isotherms of CO2, CO, N2, CH4, Ar, and H2 on activated carbon and zeolite LiX were measured using a volumetric method. Equilibrium experiments were conducted at 293, 308, and 323 K and pressures up to 1.0 MPa. The adsorption isotherm and heat of adsorption were analyzed for two pressure regions of experimental data: pressures up to 0.1 MPa and up to 1.0 MPa. Each experimental isotherm was correlated by the Langmuir, Sips, Toth and temperature dependent Sips isotherm models, and the deviation of each model was evaluated. The Sips and Toth models showed smaller deviation from the experimental data of adsorbents than the Langmuir model. Isosteric heats of adsorption were calculated by the temperature dependent Sips model and are presented along with surface loading. From deviation analysis, it is recommended that the isotherm in the proper pressure range be used to appropriately design adsorptive processes.

Solid poly(acrylamide) (PAAm) composite membranes containing silver ions have been investigated for olefin/paraffin separation. The propylene permeance increased significantly for a solid PAAm/AgBF 4 composite membrane with increasing loading amount of silver ions. Silver ions in solid PAAm form reversible complexes with propylene, resulting in the facilitated transport of propylene. The propylene selectivity of 100 over propane was obtained when the mole ratio of silver ions to acrylamide unit was 1. This high separation performance would be obtained predominantly because of the high loading of the propylene carrier, silver ions. PAAm-graft/AgBF 4 composite membranes were prepared in order to improve the gas permeance. Introduction of PAAm grafts on a polysulfone microporous membrane surface was confirmed by FT-IR spectroscopy. The propylene permeance was increased through the PAAm-graft/AgBF 4 membranes compared to that through of the PAAm/AgBF 4 composite membranes, indicating the formation of ultra-thin top layer.