Electrochemical properties of novel organodisulfide poly 1,2-bis(thiophen-3-ylmethyl)disulfane as cathode material for secondary lithium batteries

We successfully synthesized a new organodisulfide poly 1,2-bis(thiophen-3-ylmethyl)disulfane by a facile preparation method. The types of the chemical groups of poly-3-thienylthiophene were characterized by Fourier transform infrared spectroscopy (FTIR). The electrochemical properties of S–S bonds redox behavior in the organodisulfides were investigated in CH₃CN/0.1 M [Bu₄N] [PF₆] solution. The separation of the anodic and cathodic peak potentials for poly 1,2-bis(thiophen-3-ylmethyl)disulfane is 180 mV. The results indicated that poly 1,2-bis(thiophen-3-ylmethyl)disulfane has an excellent electrochemical reversibility. The average specific capacity of 230 mAh g⁻¹ for poly-3-thienylthiophene is about 2 times higher than that of LiCoO₂.     

An improvement of the hydrogen permeability of C/Al2O3 membranes by palladium deposition into the pores

The development of compact hydrogen separator based on membrane technology is of key importance for hydrogen energy utilization, and the Pd-modified carbon membranes with enhanced hydrogen permeability were investigated in this work. The C/Al₂O₃ membranes were prepared by coating and carbonization of polyfurfuryl alcohol, then the palladium was introduced through impregnation–precipitation and colloid impregnation methods with a PdCl₂/HCl solution and a Pd(OH)₂ colloid as the palladium resources, and the reduction was carried out with a N₂H₄ solution. The resulting Pd/C/Al₂O₃ membranes were characterized by means of SEM, EDX, XRD, XPS and TEM, and their permeation performances were tested with H₂, CO₂, N₂ and CH₄ at 25 °C. Compared with the colloid impregnation method, the impregnation–precipitation is more effective in deposition of palladium clusters inside of the carbon layer, and this kind of Pd/C/Al₂O₃ membranes exhibits excellent hydrogen permeability and permselectivity. Best hydrogen permeance, 1.9 × 10⁻⁷ mol/m² s Pa, is observed at Pd/C = 0.1 wt/wt, and the corresponding H₂/N₂, H₂/CO₂ and H₂/CH₄ permselectivities are 275, 15 and 317, respectively.     

Enhanced water splitting through different substituted cobalt-salophen electrocatalysts

Synthesis of stable catalysts for water splitting is important for the renewable and clean energy production. Here, water oxidation activities of cobalt (II) complexes CoL¹-CoL³ (1–3) with salophen type ligands (N,N′-bis(salicylidene)-4-chloro-1,2-phenylendiamine (H₂L¹), N,N′-bis(salicylidene)-4-bromo-1,2-phenylendiamine (H₂L²) and N,N′-bis(salicylidene)-4-nitro-1,2-phenylendiamine (H₂L³)) are studied by electrochemical techniques, FE-SEM images and XRD patterns. Linear sweep voltammetry studies indicate that 2 and 3 have superior activities and only require the overpotential of 316 and 247 mV vs. RHE at current density of 10 mA/cm² with Tafel slopes of 75 and 50 mVdec^?1 at pH = 11. Experiments show relationships between the stability of the complexes and their catalytic activity. It is revealed that substituents on ligands affect the catalytic behaviors. Experiments show that in the presence of 2 and 3, the complexed cobalt ions are likely candidates as molecular catalysts for water oxidation. It is speculated that the O–O bond formation occurs by oxidizing the active center of cobalt complexes.     

High temperature H2/CO2 separation using cobalt oxide silica membranes

In this work high quality cobalt oxide silica membranes were synthesized on alumina supports using a sol–gel, dip coating method. The membranes were subsequently connected into a steel module using a graphite based proprietary sealing method. The sealed membranes were tested for single gas permeance of He, H₂, N₂ and CO₂ at temperatures up to 600 °C and feed pressures up to 600 kPa. Pressure tests confirmed that the sealing system was effective as no gas leaks were observed during testing. A H₂ permeance of 1.9 × 10⁻⁷ mol m⁻² s⁻¹ Pa⁻¹ was measured in conjunction with a H₂/CO₂ permselectivity of more than 1500, suggesting that the membranes had a very narrow pore size distribution and an average pore diameter of approximately 3 Å. The high temperature testing demonstrated that the incorporation of cobalt oxide into the silica matrix produced a structure with a higher thermal stability, able to resist thermally induced densification up to at least 600 °C. Furthermore, the membranes were tested for H₂/CO₂ binary feed mixtures between 400 and 600 °C. At these conditions, the reverse of the water gas shift reaction occurred, inadvertently generating CO and water which increased as a function of CO₂ feed concentration. The purity of H₂ in the permeate stream significantly decreased for CO₂ feed concentrations in excess of 50 vol%. However, the gas mixtures (H₂, CO₂, CO and water) had a more profound effect on the H₂ permeate flow rates which significantly decreased, almost exponentially as the CO₂ feed concentration increased.     

The effect of non-uniform temperature on the sorption-enhanced steam methane reforming in a tubular fixed-bed reactor

The effect of non-uniform temperature on the sorption-enhanced steam methane reforming (SE-SMR) in a tubular fixed-bed reactor with a constant wall temperature of 600 °C is investigated numerically by an experimentally verified unsteady two-dimensional model. The reactor uses Ni/Al₂O₃ as the reforming catalyst and CaO as the sorbent. The reaction of SMR is enhanced by removing the CO₂ through the reaction of CaO + CO₂ → CaCO₃ based on the Le Chatelier's principle. A non-uniform temperature distribution instead of a uniform temperature in the reactor appears due to the rapid endothermic reaction of SMR followed by an exothermic reaction of CO₂ sorption. For a small weight hourly space velocity (WHSV) of 0.67 h^?1 before the CO₂ breakthrough, both a low and a high temperature regions exist simultaneously in the catalyst/sorbent bed, and their sizes are enlarged and the temperature distribution is more non-uniform for a larger tube diameter (D). Both the CH₄ conversion and the H₂ molar fraction are slightly increased with the increase of D. Based on the parameters adopted in this work, the CH₄ conversion, the H₂ and CO molar fractions at D = 60 mm are 84.6%, 94.4%, and 0.63%, respectively. After CO₂ breakthrough, the reaction of SMR dominates, and the reactor performance is remarkably reduced due to low reactor temperature.For a higher value of WHSV (4.03 h^?1) before CO₂ breakthrough, both the reaction times for SMR and CO₂ sorption become much shorter. The size of low temperature region becomes larger, and the high temperature region inside the catalyst/sorbent bed doesn't exist for D ≥ 30 mm. The maximum temperature difference inside the catalyst/sorbent bed is greater than 67 °C. Both the CH₄ conversion and H₂ molar fraction are slightly decreased with the increase of D. However, this phenomenon is qualitatively opposite to that for small WHSV of 0.67 h^?1. The CH₄ conversion and H₂ molar fraction at D = 60 mm are 52.6% and 78.7%, respectively, which are much lower than those for WHSV = 0.67 h^?1.     

N,N-bis(sulfopropyl)aminyl-4-phenyl polysulfone and O,O′-bis(sulfopropyl)resorcinol-5-yl-4-phenyl polysulfone composite membrane for proton exchange membrane fuel cells

Novel functionalized polysulfone with high local density of sulfonic acid groups, N,N-bis(sulfopropyl)aminyl-4-phenyl polysulfone or O,O′-bis(sulfopropyl)resorcinol-5-yl-4-phenyl polysulfone (PSF-X-C₃H₆SO₃H, X = N or O) are synthesized. These polymers are synthesized by bromination of polysulfone followed by Suzuki cross-coupling reaction to graft the aminophenyl groups and the dimethoxyphenyl groups onto the polymeric backbone, followed by introduction of the sulfopropyl groups via sultone ring-opening reaction. In addition, the composite membrane of PSF-O-C₃H₆SO₃H and PSF-N-C₃H₆SO₃H is also synthesized for comparison. The maximum proton conductivity of composite PSF-O-C₃H₆SO₃H and PSF-N-C₃H₆SO₃H reaches 46.66 mS cm⁻¹ at 95 °C and 90% RH, higher than PSF-O-C₃H₆SO₃H (42.06 mS cm⁻¹) and PSF-N-C₃H₆SO₃H (38.76 mS cm⁻¹). Meanwhile, the composite exhibits compromised water uptake and swelling ratio, and low methanol permeability. The excellent overall performance of the composite is attributed to phase-separation between the hydrophilic and the hydrophobic subphases, and the hydrogen-bonding network developed in the hydrophilic subphases.     

Mercury(II)-complex with 5-methyl-1,3,4-thiadiazole-2-thiol: kinetic studies of hydrogen storage

Mixed ligand mercury(II) complexes of 2-meracpto-5-methyl-1,3,4-thiazdiazole (HmtzS) and phosphines or diamines having the general formulae [Hg(mtsZ)₂(diphos)] {diphos = 1,2-bis(diphenylphosphino)ethane (dppe), 1,3-bis(diphenylphosphino)propane (dppp), 1,4-bis(diphenylphosphino)butane (dppe), 1,1′-bis(diphenylphosphino)ferrocene (dppf)}, [Hg(mtsZ)₂(PPh₃)₂] and [Hg(mtsZ)₂(diamine)] {diamine = bipyridyl (Bipy) or 1,10-phenthroline (Phen), were successfully synthesized by simple mixing method. The complexes were characterized by elemental analysis, molar conductivity, IR and NMR (¹H, ¹³C and ³¹P) spectroscopic methods. The mtzS^? ligand was coordinated through the sulfur atom of thiol group, whereas the diphosphine or diamine ligands bonded as bidentate chelating ligand to afford tetrahedral environment around the Hg(II) ions. Moreover, the complex [Hg(mtsZ)₂] was used in order to study its ability to store hydrogen. The results of hydrogen isotherm at different temperatures prove that [Hg(mtsZ)₂] was able to store 0.8 wt% at a pressure of 80 bar 77 K. Furthermore, the kinetic study of hydrogen storage was studied and the kinetic study was carried out using the Langmuir. Moreover, the adsorption kinetic results revealed that hydrogen storage in [Hg(mtsZ)₂] follow the pseudo-second-order model with coefficient regression equal to 0.99.     

Composite Ni–Ba(Zr0.1Ce0.7Y0.2)O3 membrane for hydrogen separation

Composite membranes consisting of Ni metal and Ba(Zr_0.1Ce_0.7Y_0.2)O₃ (or Ni–BZCY7) have been developed for separation of hydrogen from gas mixtures to replace Ni–BCY20 (Ni–BaCe_0.8Y_0.2O₃), which has poor stability in CO₂ and H₂O-containing atmosphere. Hydrogen fluxes through these cermet membranes were measured as a function of temperature, membrane thickness, and partial pressure of hydrogen in various atmospheres. Results indicated that the Ni–BZCY7 membrane is chemically stable and display high hydrogen permeability. A maximum flux of 0.805 cm³ min⁻¹ cm² was obtained for a dense cermet membrane of 266-μm-thick at 900 °C using 100% H₂ as the feed gas and 100 ppm H₂/N₂ as the sweep gas. The stable performance of Ni–BZCY7 cermet membrane during exposure to a wet gas containing 30% CO₂ for about 80 h indicated that it is promising for practical applications.     

Developing cross-linked poly(ethylene oxide) membrane by the novel reaction system for H2 purification

In this study, a ‘green” method has been discovered by utilizing the amino functional poly(ethylene oxide) (PEO) and epoxy functional PEO with low molecular weights to synthesis cross-linked membranes for enhancing H₂ purification and CO₂ capture performance by retarding the crystallinity of semi-crystalline polymer of PEO. The cross-linking reaction can happen simply by mixing two materials without using any solvent. The reaction has been characterized by Fourier transform infrared-attenuated total reflectance (FTIR-ATR), X-ray photoelectron spectroscopy (XPS), solid-state ¹³C nuclear magnetic resonance (NMR) and the gel content test. Furthermore, X-ray diffraction (XRD) and differential scanning calorimeter (DSC) confirm the amorphous structure of cross-linked PEO membranes, which should benefit the gas transport. The gas transport properties and the plasticizing phenomenon of CO₂ have been examined in detail. Interestingly, the investigation on CO₂ plasticization phenomenon reveals that the cross-linked PEO membrane should be plasticized immediately after the pressure load. The pressure dependence of CO₂ permeability in the pressure range from 0.25 atm to 30 atm can be separated into two stages based on the permeability increment although the CO₂ permeability continuously increases with the loading pressure. The gas transport results illustrate that CO₂ has much larger permeability than that of any tested gas (including H₂, N₂ and CH₄) attributing to the CO₂-philic characteristic of ethylene oxide (EO) groups in the cross-linked PEO membrane. The good permeability and selectivity make the developed PEO membrane promising for H₂ purification and CO₂ capture applications.     

Fabrication and characterization of poly(phenylene oxide)/SBA-15/carbon molecule sieve multilayer mixed matrix membrane for gas separation

A novel multilayer mixed matrix membrane (MMM), consisting of poly(phenylene oxide) (PPO), large-pore mesoporous silica molecular sieve zeolite SBA-15, and a carbon molecular sieve (CMS)/Al₂O₃ substrate, was successfully fabricated using the procedure outlined in this paper. The membranes were cast by spin coating and exposed to different gases for the purpose of determining and comparing the permeability and selectivity of PPO/SBA-15 membranes to H₂, CO₂, N₂, and CH₄. PPO/SBA-15/CMS/Al₂O₃ MMMs with different loading weights of zeolite SBA-15 were also studied. This new class of PPO/SBA-15/CMS/Al₂O₃ multilayer MMMs showed higher levels of gas permeability compared to PPO/SBA-15 membranes. The permselectivity of H₂/N₂ and H₂/CH₄ combinations increased remarkably, with values at 38.9 and 50.9, respectively, at 10 wt% zeolite loading. Field emission scanning electron microscopy results showed that the interface between the polymer and the zeolite in MMMs was better at a 10 wt% loading than other loading levels. The increments of the glass transition temperature of MMMs with zeolite confirm that zeolite causes polymer chains to become rigid.     

Computational evaluation of 2D metal-organic frameworks with TMX4-centers (X = O,S and Se) for CO2 electroreduction

Electrochemical CO₂ reduction into value-added fuels and chemicals is regarded as a highly efficient way to achieve a carbon neutral cycle. Recently, two-dimensional metal-organic frameworks (2D MOFs) have attracted much attention in CO₂ reduction reaction (CO₂RR). Herein, we employed density functional theory (DFT) to study the catalytic performance of 48 kinds of the π-d conjugated 2D layered MOFs, i.e., TM-BHX, composed of transition metal ions and multidentate organic ligands, such as benzenehexaol (BHO), benzenehexathiol (BHT) and benzenehexaselenolate (BHS), for CO₂RR. By investigating the thermodynamic stability and electrochemical stability, conductivity and the free energy change of the first hydrogenation step (CO₂ + H⁺ + e^? → 1COOH or CO₂ + H⁺ + e^? → 1HCOO), nine TM-BHX were selected from 48 MOFs, including TM-BHT (TM = Cr, Fe, Co, Ru, Rh, Ir) and TM-BHS (TM = Ru, Rh, Ir). Possible reaction pathways of CO₂ reduction into C1 products were explored to determine the CO₂RR mechanism. Our results showed that among 9 candidates, Cr-, Fe-, Co-BHT, and Ir–BHS not only exhibit high activity with low limiting potential (?0.30, ?0.29, 0, and ?0.49 V, respectively), but also have high CO₂RR selectivity with the positive value of U_L(CO₂) – U_L(H₂), so they are promising CO₂RR electrocatalysts. This work provides a new kind of 2D MOFs as efficient CO₂RR electrocatalysts for experimental research.     

Improvement of hydrogen-separating performance by on-stream catalytic cracking of silane over hollow fiber MFI zeolite membrane

MFI zeolite membranes were synthesized on porous α-alumina hollow fibers by in-situ hydrothermal synthesis. The membranes were further modified for H₂ separation by on-stream catalytic cracking deposition of methyldiethoxysilane (MDES) in the zeolitic pores. The separation performance of the modified membranes was characterized by separation of H₂/CO₂ gas mixture at 500 °C. Activation of MFI zeolite membranes by air at 500 °C was found to promote catalytic cracking deposition of silane in the zeolitic pores effectively, which resulted in significant improvement of H₂-separating performance. The H₂/CO₂ separation factor of 45.6 with H₂ permeance of 1.0 × 10⁻⁸ mol m⁻² s⁻¹ Pa⁻¹ was obtained at 500 °C for a modified hollow fiber MFI zeolite membrane. The as-made membranes showed good thermochemical stability for the separation of H₂/CO₂ gas mixture containing H₂O and H₂S, respectively.     

Hydrogen separation and purification with poly (4-methyl-1-pentyne)/MIL 53 mixed matrix membrane based on reverse selectivity

The effect of MIL 53 (Al) metal organic framework on gas transport properties of poly (4-methyl-1-pentyne) (PMP) was determined based on reverse selectivity. Mixed matrix membranes (MMMs) were fabricated considering various weight percent of MIL 53 particles. The reverse MMMs permselectivities were evaluated through measurement of pure CO₂ and H₂ permeation together with calculation of CO₂/H₂ selectivity. The PMP/MIL 53 (Al) MMMs exhibited privileged CO₂/H₂ permselectivity in comparison with the neat PMP. In addition, CO₂ solubility coefficient was significantly increased with increasing the MIL 53 loading, while the H₂ solubility coefficient was almost remained unchanged. Moreover with increasing the feed pressure the permeability of CO₂ and CO₂/H₂ selectivity were dramatically enhanced, especially at higher filler loadings. Therefore, it was observed that the reverse selectivity of MMMs was enhanced so that the Robeson upper bound was overcome. The best yielding membranes (PMP/30 wt.% MIL 53) represented the CO₂ permeability and CO₂/H₂ selectivity of 377.24 barrer and 24.91 for pure gas experiments respectively.     

Co(III) carboxamide complexes as electrocatalysts for water splitting

Water splitting is a promising approach for storing intermittent renewable energies, such as sunlight in the clean chemical bonds as a hydrogen fuel. Two water-soluble octahedral cobalt (III) complexes, [Co(bpb)(OAc)(H₂O)], 1, (bpb^2? = N,N′-bis[(2-pyridine carboxamide)-1,2-benzene] dianion) and [Co(cbpb)(OAc)(H₂O)], 2, (cbpb^2? = N,N′-bis[(2-pyridine carboxamide)-4-chloro-1,2-benzene] dianion) were synthesised and characterised by CHN elemental analysis, UV–Vis, FT-IR and single-crystal X-ray diffraction techniques. The two carboxamide ligands had been prepared in the ionic liquid TBAB as an environmentally benign reaction medium. The electrocatalytic water splitting activity of 1 and 2 showed that both complexes are highly active for the water splitting in aqueous solutions. Turn Over Frequency (TOF) values were, for 1 and 2 respectively, 527 and 490 mol of hydrogen in each mole of catalyst per hour at an overpotential of 738 mV (pH = 7.0). Such a performance can be ascribed to the flat ligands, the electroactivity of the metal centre and carboxamide ligands and the ability of losing the axial ligands around the metal-ion centre during the reduction process which provide different reduction pathways for an HER process.     

Highly selective high-silica SSZ-13 zeolite membranes for H2 production from syngas

A highly CO₂-selective high-silica SSZ-13 zeolite membrane was used for H₂ production by separating CO₂ from syngas (CO₂/H₂ mixture). High-silica SSZ-13 zeolite membranes were fabricated using outside asymmetric alumina tubes by secondary growth of ball-milled SSZ-13 seeds. The composition of membrane gel and synthesis time were modified. The Si/Al ratio in framework of the membrane was as high as 42 when SiO₂/Al₂O₃ ratio of the gel increased to 140. The effects of test parameters such as pressure drop, temperature, feed flow rate and concentration on membrane performance were investigated. The test pressure drop was up to 2 MPa. The ultra-high CO₂/H₂ selectivity of 161 with excellent CO₂ permeances of ~6.3 × 10⁻⁷ mol/(m² s Pa) (=3760 GPU) were observed for the best membrane at 243 K and pressure drop of 0.2 MPa. Carbon dioxide permeance through high-silica SSZ-13 zeolite membrane was 4.2 × 10⁻⁷ mol/(m² s Pa) (=2500 GPU) at 298 K and pressure drop of 2.0 MPa, and the CO₂/H₂ selectivity was 17.4. The current high-silica SSZ-13 zeolite membranes exceeded the upper bound of polymeric membranes and other inorganic membranes in CO₂/H₂ plots and owned great potentials for H₂ production from syngas.     

The property of hydrogen separation from CO2 mixture using Pd-based membranes for carbon capture and storage (CCS)

This study investigates the module configuration for upscaling CO₂ capture capacity to a bench-scale in hydrogen selective Pd-based composite membranes. In order to confirm effective upscaling, four plate-type membranes of two inch diameter were stacked in a newly designed plate-and-frame type module, reaching a total membrane surface area of 6.64 × 10⁻³ m² (66.4 cm²). A pure gas test carried out using H₂ and He confirmed that there were no effects of module configuration in gas permeation behavior, indicating that the upscale of the separation capacity by numbering-up of membranes using our module design was successful. The CO₂ enrichment test was conducted using a 40%CO₂ + 60%H₂ mixture (i.e. a similar composition for the coal gasifier after both the shift reaction and H₂O removal), under high feed pressure and flow rate, i.e. 600–2100 kPa and 0.48–0.72 N m³ h⁻¹. The mixture gas test confirmed that the bench-scale membrane module could enrich 40% of the CO₂ at a feed flow rate of 0.48 N m³ h⁻¹ up to 93% with a hydrogen recovery ratio of >90% at 673 K and a total feed pressure of 2100 kPa, i.e. ∼4 times CO₂ enrichment capacity of one membrane.     

Impact of vacuum operation on hydrogen permeation through a palladium membrane tube

Palladium (Pd) membranes are characterized by their high permselectivity to hydrogen and easy operation, and are promising devises for separating hydrogen from hydrogen-rich gases. The membranes are normally operated with atmospheric pressure at the permeate side. Instead of this common operation, hydrogen permeation through a Pd membrane under vacuum operation at the permeate side is investigated and compared with that under normal operation. In this study, two membrane operating temperatures (320 and 380 °C), four H₂ partial pressure differences (2, 3, 4, and 5 atm) across the membrane, and four feed gases are considered. The results suggest that the vacuum operation can efficiently intensify the H₂ permeation rate. The improvement in H₂ permeation rate due to the vacuum operation can be increased up to 136%. The positive effect of the vacuum operation is especially pronounced when the gas mixtures are used as the feed gases, stemming from the effective attenuation of the concentration polarization. An increase in membrane temperature raises the H₂ permeation rate, but its influence in enhancing the H₂ permeation rate with the vacuum operation is not as significant as that without the vacuum one. It is found that the retardation effect of impurities on the mass transfer is always ranked as CO > CO₂ > N₂, regardless of with/without vacuum operation.     

High-flux H2 separation membranes from (Pd/Au)n nanolayers

A novel strategy for the preparation of supported PdAu alloy layers allows the facile and fast fabrication of highly permeable and selective H₂ separation membranes from refractory metals via electroless plating and low-temperature alloying. Homogenous alloying of multiple, separately deposited Pd and Au layers with thickness in the nm range required less than one week at 773 K under atmospheric H₂ as evidenced by X-ray diffraction and H₂ permeation measurements. The H₂ permeation rate JH₂ became stable within a day even, reaching 0.62 mol m⁻² s⁻¹ at 773 K and ΔPH₂ = 100 kPa. The corresponding N₂ leak rate remained constant during a 350 h experiment, resulting in an ideal H₂/N₂ selectivity of 1400 and demonstrating that such membranes tolerate extended operation at that temperature well.     

Hydrogen permeation in a palladium membrane tube: Impacts of outlet and vacuum degree

Palladium (Pd) membranes are a crucial device for separating hydrogen and are usually operated at normal pressure on the permeate side with a single outlet. Instead of these common operating conditions, the difference between using a double outlet and a single outlet is studied. Four different vacuum degrees (15–60 kPa) are applied on the permeate side, and the results are compared with the non-vacuum operations. Situations under the vacuum and the effects of temperatures (300–400 °C) on H₂ permeation are discussed. Finally, the influences of different feed gas mixtures (H₂/N_2, H₂/CO_2, and H₂/CO) on the Pd membrane performance are investigated. The results show that there is no difference in H₂ permeation impact the single outlet and the double outlet on the permeate side. When a vacuum is imposed on the permeate side, the H₂ permeation rate and H₂ recovery are efficiently intensified, that is, when the pressure difference is 9 atm, they increase from 73.21 to 84.51% and from 0.0035378 to 0.0040808 mol?s^?1, respectively. Moreover, the H₂ recovery can be improved to up to 68.44% under a vacuum degree of 60 kPa. At a given Reynolds number, an increase in temperature increases the H₂ permeation rate but lowers its recovery, stemming from more H₂ in the feed gas. This study also investigates the feed gas of H₂/N₂ under a vacuum to provide a useful insight into H₂ production and separation from ammonia, and the results are compared with two different feed gases of H₂/CO₂ and H₂/CO mixtures. The results suggest that the impurities (i.e., N₂, CO₂, and CO) have a negative influence on the Pd membrane, which causes the H₂ permeation rate to decrease, and the effect of N₂ is the least significant compared to the other two.     

Assessment of nitrogen fertilization for the CO2 balance during the production of poplar and rye

This study was designed to consider all nitrogen fertilizer-related effects on crop production and emission of greenhouse gases on loamy sandy soils in Germany over a period of nine years (1999–2007). In order to set up a CO₂ balance for the production of energy crops, different nitrogen pathways were investigated, such as direct N₂O emissions from the soil and indirect emissions related to NO₃ leaching and fertilizer production. Fluxes of N₂O were measured in an experimental field using closed chambers. Poplar (Populus maximowiczii × P. nigra) and rye (Secale cereale L.) as one perennial and one annual crop were fertilized at rates of 0 kg N ha^?1 yr^?1, 75 kg N ha^?1 yr^?1 and 150 kg N ha^?1 yr^?1. The mean N₂O emissions from the soil ranged between 0.5 kg N ha^?1 yr^?1 and 2.5 kg N ha^?1 yr^?1 depending on fertilization rate, crop variety and year. The CO₂ fixed in the biomass of energy crops is reduced by up to 16% if direct N₂O emissions from soil and indirect N₂O emissions from NO₃ leaching and fertilizer production are included. Taking into account the main greenhouse gas emissions, which derive from the production and the use of N fertilizer, the growth of poplar and rye may replace the global warming potential of fossil fuels by up to 17.7 t CO₂ ha^?1 yr^?1 and 12.1 t CO₂ ha^?1 yr^?1, respectively.