共查询到20条相似文献,搜索用时 15 毫秒
1.
《International Journal of Hydrogen Energy》2022,47(96):40787-40802
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/N2, H2/CO2, 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. 相似文献
2.
《International Journal of Hydrogen Energy》2020,45(12):7401-7411
Hydrogen purification using palladium (Pd) membrane technology has been seen as a potential solution for producing pure hydrogen form hydrogen-rich gas. Compared to traditional practices of operating the permeate side of the membrane at atmospheric pressure, in this study, a vacuum is applied. The effects of various vacuum degrees applied to the permeate side of the Pd membrane are investigated and compared to the results under normal operation without a vacuum. The feed gas used for experiments consists of a mixture of hydrogen (70 vol%) and nitrogen (30 vol%). Three membrane operating temperatures (320, 350, and 380 °C), four pressure differences (2, 3, 4, and 5 atm) across the membrane, and four vacuum degrees (−15, −30, −45, and −53 kPa) applied to the permeate side are considered. For the three operating temperatures, the best improvements in the performance of hydrogen permeation are at 320 and 350 °C when a −53 kPa vacuum is applied, resulting in 79.4% and 79.1% improvements, respectively, compared to normal operations. Increasing temperatures leads to an increase in H2 permeation both with and without a vacuum; however, best performances of H2 permeation are observed in cases without a vacuum. 相似文献
3.
《International Journal of Hydrogen Energy》2022,47(100):42266-42279
This study uses a palladium membrane to separate hydrogen from an H2/CO2 (90/10 vol%) gas mixture. Three different operating parameters of temperature (320–380 °C), total pressure difference (2–3.5 atm), and vacuum degree (15–49 kPa) on hydrogen are taken into account, and the experiments are designed utilizing a central composite design (CCD). Analysis of variance (ANOVA) is also used to analyze the importance and suitability of the operating factors. Both the H2 flux and CO2 (impurity) concentration on the permeate side are the targets in this study. The ANOVA results indicate that the influences of the three factors on the H2 flux follow the order of vacuum degree, temperature, and total pressure difference. However, for CO2 transport across the membrane, the parameters rank as total pressure difference > vacuum degree > temperature. The predictions of the maximum H2 flux and minimum CO2 concentration by the response surface methodology are close to those by experiments. The maximum H2 flux is 0.2163 mol s?1 m?2, occurring at 380 °C, 3.5 atm total pressure difference, and 49 kPa vacuum degree. Meanwhile, the minimum CO2 concentration in the permeate stream is t 643.58 ppm with the operations of 320 °C, 2 atm total pressure difference, and 15 kPa vacuum degree. The operation with a vacuum can significantly intensify H2 permeation, but it also facilitates CO2 diffusion across the Pd membrane. Therefore, a compromise between the H2 flux and the impurity in the treated gas should be taken into account, depending on the requirement of the gas product. 相似文献
4.
Wei-Hsin Chen Ming-Hsien Hsia Yu-Li Lin Yen-Hsun Chi Chang-Chung Yang 《International Journal of Hydrogen Energy》2013
Hydrogen separation from H2–N2 gas mixtures by means of high-permeance Pd membranes is an appropriate route to gain pure hydrogen for fuel cell applications. To figure out the mass transfer phenomena of H2 in membrane tubes, H2 permeation and recovery characteristics of two high-permeance Pd membranes are investigated. Four important factors influencing H2 permeation, namely, the H2 pressure difference, H2 concentration, the flow rate at the exit of the retentate side, and membrane temperature, are taken into account. The experimental results suggest that decreasing H2 concentration, flow rate, and temperature reduce the permeances of the membranes and H2 recovery, even though the H2 pressure difference is identical. The dimensionless permeance, a permeance ratio between H2–N2 gas mixture and pure H2 as feed gases, is used to evaluate the extent of concentration polarization. Within the investigated ranges of the four factors, the dimensionless permeances of the two membranes are in the ranges of 0.022–0.206 and 0.042–0.359, respectively, revealing that the concentration polarization diminishes the permeance of the membranes down to the level within two orders of magnitude. Nevertheless, over 46% of H2 is recovered. 相似文献
5.
《International Journal of Hydrogen Energy》2022,47(100):42280-42292
In this study, the separation of hydrogen from gas mixtures using a palladium membrane coupled with a vacuum environment on the permeate side was studied experimentally. The gas mixtures composed of H2, N2, and CO2 were used as the feed. Hydrogen permeation fluxes were measured with membrane operating temperature in the range of 320–380 °C, pressures on the retentate side in the range of 2–5 atm, and vacuum pressures on the permeate side in the range of 15–51 kPa. The Taguchi method was used to design the operating conditions for the experiments based on an orthogonal array. Using the measured H2 permeation fluxes from the Taguchi approach, the stepwise regression analysis was also employed for establishing the prediction models of H2 permeation flux, followed by the analysis of variance (ANOVA) to identify the significance and suitability of operating conditions. Based on both the Taguchi approach and ANOVA, the H2 permeation flux was mostly affected by the gas mixture composition, followed by the retentate side pressure, the vacuum degree, and the membrane temperature. The predicted optimal operating conditions were the gas mixture with 75% H2 and 25% N2, the membrane temperature of 320 °C, the retentate side pressure of 5 atm, and the vacuum degree of 51 kPa. Under these conditions, the H2 permeation flux was 0.185 mol s?1 m?2. A second-order normalized regression model with a relative error of less than 7% was obtained based on the measured H2 permeation flux. 相似文献
6.
José Antonio Calles Raúl SanzDavid Alique Laura Furones 《International Journal of Hydrogen Energy》2014
This work comprises a study of hydrogen separation with a composite Pd-YSZ-PSS membrane from mixtures of H2, N2, CO and CO2, typical of a water gas shift reactor. The Pd layer is extended over a tubular porous stainless steel support (PSS) with an intermediate layer of yttria-stabilized-zirconia (YSZ). YSZ and Pd layers were incorporated over the PSS using Atmospheric Plasma Spraying and Electroless Plating techniques, respectively. The Pd and YSZ thickness values are 13.8 and 100 μm, respectively, and the Pd layer is fully dense. Permeation measurements with pure, binary and ternary gases at different temperatures (350–450 °C), trans-membrane pressures (0–2.5 bar) and gas composition have been carried out. Moreover, thermal stability of the membrane was also checked by repeating permeation measurements after several cycles of heating and cooling the system. Membrane hydrogen permeances were calculated using Sieverts' law, obtaining values in the range of 4·10−5–4·10−4 mol m−2 s−1 Pa−0.5. The activation energy of the permeance was also calculated using Arrhenius' equation, obtaining a value of 16.4 kJ/mol. In spite of hydrogen selectivity being 100% for all experiments, the hydrogen permeability was affected by the composition of feed gas. Thus, a significant depletion in H2 permeate flux was observed when other gases were in the mixture, especially CO, being also more or less significant depending on gas composition. 相似文献
7.
Erhu Yan Haoran Huang Ruonan Min Ping Zhao R. Devesh K. Misra Pengru Huang Fen Xu Lixian Sun 《International Journal of Hydrogen Energy》2018,43(31):14466-14477
Effect of Pd overlayer and mixed gases on hydrogen permeation of Pd/Nb30Hf35Co35/Pd composite membranes was investigated. The diameter of Pd particle increases with increasing sputtering power. With this change, the membrane shows a signification reduction in hydrogen permeability/or flux, but its durability and stability increases significantly, which can be mainly attributed to a decrease in hydrogen solubility coefficient. In addition, H2S impurity in mixed gases can greatly degrade membrane performance, especially the hydrogen permeability, whereas the Ar impurity content has less effect in the temperature range of 523–673 K. Lowering of permeability caused by the change of gas purity can be attributed to a decrease in hydrogen solubility, which is closely related to the stronger adsorption of H2S molecules to the Pd overlayer of the membrane. Thus, it is concluded that aside from the optimum design for composition of Nb-based hydrogen permeable alloy to improve their permeability, the control of Pd overlayer film on membrane surface and gas purity in the feed gas is important. 相似文献
8.
The influence of co-existing gases on the hydrogen permeation was studied through a Pd-coated V89.8Cr10Y0.2 alloy membrane. Preliminary hydrogen permeation experiments have been confirmed that hydrogen flux was 6.26 ml/min/cm2 for a Pd-coated V89.8Cr10Y0.2 alloy membrane (thick: 0.5 mm) using pure hydrogen as feed gas. Also, the hydrogen permeation flux decreased with decrease of hydrogen partial pressure at constant pressure when H2/CO2 and H2/CO2/H2S mixture applied as feed gas respectively and permeation fluxes were satisfied with Sievert's law in different feed conditions. It was found from XRD and SEM results after permeation test that the Pd-coated V89.8Cr10Y0.2 alloy membrane had good stability and durability for various mixture feeding conditions. 相似文献
9.
《International Journal of Hydrogen Energy》2022,47(54):22819-22831
The hydrogen (H2) diffusion through palladium (Pd) and Pd–copper (Cu) membranes was numerically investigated by developing a two-dimensional computational fluid dynamics model for predicting the performance of H2 separation. The momentum and mass transport phenomena in the laminar flow conditions were solved at different operating conditions in a vertical cylindrical-type reactor. The effect of feed-gap distance, H2 concentration, and reactor heating temperature on the H2 permeation processes were simulated and compared for both Pd-based membranes. The concentration, velocity, and convective and diffusion mass transfer flux distributions were analyzed using the designed model. The H2 concentration was proportional to the feed-gap distance/cross-sectional area. The smaller the feed-gap distance, the greater the probability of a H2 molecule being adsorbed by the membrane surface and the ionization energy increasing, leading to further H2 dissociation through the Pd-based membranes. It was found that the diffusion flux of all feed concentrations was substantially decreased 50 s after the start of the permeation process. Moreover, the diffusion flux of the Pd–Cu40% membrane was relatively larger than that of the pure Pd membrane under the same operating conditions. The distributions of the convective flux, diffusion mass transfer flux, and concentration of the Pd–Cu40% membrane were substantially increased up to 350 °C, then fell to a lower value at higher temperatures. The simulation results were validated with the experimental results, with analysis indicating a good agreement with the experimental results under the same operating conditions. It can be concluded that the simulation modeling for Pd-based membranes was able to predict the optimum operating conditions at high H2 diffusion rates. 相似文献
10.
Andrés Mahecha-Botero Tony BoydAli Gulamhusein John R. Grace C. Jim Lim Yoshinori ShirasakiHideto Kurokawa Isamu Yasuda 《International Journal of Hydrogen Energy》2011,36(17):10727-10736
A fluidized-bed membrane reformer was operated in two independent laboratories to map various operating conditions, to investigate the effects of changing the composition of the natural gas feed stream and to verify earlier experimental trials. Two feed natural gases were tested, containing either 95.5 or 90.1 mol% of methane (3.6 or 9.9 mol% of other gaseous higher hydrocarbons). Experimental tests investigated the influence of total membrane area, reactor pressure, permeate pressure and natural gas feed rates. A permeate-H2-to reactor natural gas feed molar ratio >2.3 was achieved with six two-sided membrane panels under steam reforming conditions and a pressure differential across the membranes of 785 kPa. The total cumulative reforming time reached 395 h, while hydrogen purity exceeded 99.99% during all tests. 相似文献
11.
《International Journal of Hydrogen Energy》2020,45(43):22990-23005
Here we proposed the decreasing in the roughness of asymmetric alumina (Al2O3) hollow fibers by the deposition of a thin graphene oxide (GO) layer. GO coated substrates were then used for palladium (Pd) depositions and the composite membranes were evaluated for hydrogen permeation and hydrogen/nitrogen selectivity. Dip coating of alumina substrates for 45, 75 and 120 s under vacuum reduced the surface mean roughness from 112.6 to 94.0, 87.1 and 62.9 nm, respectively. However, the thicker GO layer (deposited for 120 s) caused membrane peel off from the substrate after Pd deposition. A single Pd layer was properly deposited on the GO coated substrates for 45 s with superior hydrogen permeance of 24 × 10−7 mol s−1m−2 Pa−1 at 450 °C and infinite hydrogen/nitrogen selectivity. Activation energy for hydrogen permeation through the Al2O3/GO/Pd composite membrane was of 43 kJ mol−1, evidencing predominance of surface rate-limiting mechanisms in hydrogen transport through the submicron-thick Pd membrane. 相似文献
12.
Margot A. Llosa Tanco Jose A. Medrano Valentina Cechetto Fausto Gallucci David A. Pacheco Tanaka 《International Journal of Hydrogen Energy》2021,46(37):19758-19767
One alternative for the storage and transport of hydrogen is blending a low amount of hydrogen (up to 15 or 20%) into existing natural gas grids. When demanded, hydrogen can be then separated, close to the end users using membranes. In this work, composite alumina carbon molecular sieves membranes (Al-CMSM) supported on tubular porous alumina have been prepared and characterized. Single gas permeation studies showed that the H2/CH4 separation properties at 30 °C are well above the Robeson limit of polymeric membranes. H2 permeation studies of the H2–CH4 mixture gases, containing 5–20% of H2 show that the H2 purity depends on the H2 content in the feed and the operating temperature. In the best scenario investigated in this work, for samples containing 10% of H2 with an inlet pressure of 7.5 bar and permeated pressure of 0.01 bar at 30 °C, the H2 purity obtained was 99.4%. 相似文献
13.
Da Hye Kim Seong Young Kong Geun-Hyuk Lee Chang Won Yoon Hyung Chul Ham Jonghee Han Kwang Ho Song Dirk Henkensmeier Sun Hee Choi 《International Journal of Hydrogen Energy》2017,42(36):22915-22924
For pure hydrogen separation, palladium was deposited on surface-treated polybenzimidazole (PBI-HFA, 4,4′-(hexafluroisopropylidene)bis(benzoic acid)) via the vacuum electroless plating technique (VELP). Since the hydrophobic characteristics of the polymer surface restrict strong adhesion of Pd on it and cause the peel-off of Pd film, various surface treatments have been employed. To increase the number of Pd anchoring sites on the PBI-HFA surface, mechanical abrasion (polishing) was applied, and to increase the hydrophilicity of the PBI-HFA surface, wet-chemical and O2 plasma treatment (dry etching) were used. The thickness and effective permeating area of the deposited Pd films on the PBI-HFA membranes were estimated to be in the range of 160–340 nm and 8.3 cm2, respectively. Among the tested membranes, membranes with Pd layers deposited on O2 plasma treated PBI-HFA surfaces had the most uniform microstructure and the least number of defects compared to the other membranes. Gas permeation experiments were performed as a function of temperature and pressure. The gases used in the permeation measurements were H2, N2, CO2, and CO (99.9% purity). A Pd-O230 m membrane, fabricated by O2 plasma surface treatment during 30 min, exhibited superior gas separation performance (H2 permeability of 275.5 Barrer), and proved to be impermeable to carbon monoxide. Enhancement of H2 permselectivity of Pd/PBI-HFA composite membrane treated by O2 plasma shows promising hydrogen separation membrane. 相似文献
14.
Zhiwen Zhu Litao Yan Haowei Liu Wenping Sun Qingping Zhang Wei Liu 《International Journal of Hydrogen Energy》2012
In this work, highly doped ceria with lanthanum, La0.5Ce0.5O2−δ (LDC), are developed as hydrogen separation membrane material. LDC presents a mixed electronic and protonic conductivity in reducing atmosphere and good stability in moist CO2 environment. LDC separation membranes with asymmetrical structure are fabricated by a cost-saving co-pressing method, using NiO + LDC + corn starch mixture as substrate and LDC as top membrane layer. Hydrogen permeation properties are systemically studied, including the influence of operating temperature, hydrogen partial pressure in feed stream and water vapor in both sides of the membrane on hydrogen permeating fluxes. Hydrogen permeability increases as the increasing of temperature and hydrogen partial pressure in feed gas. Using 20% H2/N2 (with 3% of H2O) as feed gas and dry high purity argon as sweep gas, an acceptable flux of 2.6 × 10−8 mol cm−2 s−1 is achieved at 900 °C. The existing of water in both sides of membrane has significant effect on hydrogen permeation and the corresponding reasons are analyzed and discussed. 相似文献
15.
Ke Zhang Sabina K. Gade Øyvind HatlevikJ. Douglas Way 《International Journal of Hydrogen Energy》2012,37(1):583-593
Hydrogen permeation measurements were performed at 300 °C for 25-μm cold-rolled Pd-Ag 25 wt% membranes before and after air oxidation at the same temperature as permeation. The air oxidation resulted in enhanced H2 permeation through the membrane, as well as a roughening of the surface with the formation of surface grains and defects. The protruding grains can be leveled off by exposure to H2 but the surface defects cannot. These microstructure changes are only on the membrane surfaces and do not create transmembrane defects that would allow permeation for gas species other than H2. The H2 permeability of the oxidized membrane increased by 25-90% compared to that of the as-received film at the same permeation condition, and the membranes retained perfect H2 selectivity over N2. The percent improvement of H2 permeability decreases with increasing H2 feed pressure. A new sorption kinetics hypothesis is proposed to elucidate the increase in H2 permeability of Pd-Ag membranes caused by oxidation. H2 solubility and sorption rate results were presented to test the new hypothesis. It is found that air oxidation does not change the H2 solubility in Pd-Ag membranes, but enhances the H2 sorption kinetics significantly. The extent of kinetics enhancement also decreases with increasing H2 pressures. The much faster sorption equilibrium implies higher effective H2 diffusivity at the Pd-Ag membrane surface for the oxidized sample and a higher transfer rate of atomic hydrogen from surface/sub-surface to the membrane bulk that contributes to the increase of H2 permeability observed in experiments. 相似文献
16.
Rajesh Kumar Shivani Shisodia Manoj Kumar Kamlendra Awasthi 《International Journal of Hydrogen Energy》2018,43(47):21690-21698
The hydrogen-based economy is one of the possible approaches toward to eliminate the problem of global warming, which are increases because of the gathering of greenhouse gases. Palladium (Pd) is well-known material having a strong affinity to the hydrogen absorbing property and thus appropriate material to embed in the membrane for the improvement of selective permeation of hydrogen gas. In present work, we have functionalized polycarbonate (PC) membranes with the help of UV irradiation to embed the Pd nanoparticles in pores as well as on the surface of the PC membrane. Use of Pd Nanoparticles is helpful to enhance the H2 selectivity over other gases (CO2, N2, etc.). Also, the UV based modification of membrane increases the attachment of Pd Nanoparticles. Further to enhance the Pd nanoparticles attachment, we used PVP binder with Pd nanoparticles solution. Gas permeability measurements of functionalized PC membranes have been carried out, and better selectivity of hydrogen has been found in the functionalized and Pd nanoparticle binded membrane. PC membrane with 48 h UV irradiated and Pd NPs with PVP have been found to have maximum selectivity and permeability for H2 gas. All the samples being characterized by scanning electron microscopy (SEM), Fourier-transform infrared spectroscopy (FTIR), Raman spectroscopy and UV–Vis spectroscopy for their morphological and structural investigation. 相似文献
17.
《International Journal of Hydrogen Energy》2019,44(31):16698-16706
A hydrogen-selective and hydrothermally stable membrane composed of silica-zirconia layer deposited on a modified alumina sub layer was successfully prepared. The composite membrane was used for hydrogen purification from synthesis gas in steam methane reforming process. Silica-zirconia layer was synthesized using the CVD method at 923K and atmospheric pressure while the alumina base layer was prepared via sol-gel procedure. DLS, XRD, SEM/EDX, and BET characterization techniques were used to prove that γ-alumina base and silica-zirconia layer are fabricated successfully. Using the composite membrane, hydrogen selectivity toward other gases has improved significantly. Moreover, H2/CH4, H2/CO, and H2/CO2 selectivity have been increased from 700, 350 and 70 in 5 h CVD synthesized membrane to 1600, 750 and 570 for 12 h CVD synthesized membrane respectively. The synthesized Silica-Zirconia membrane successfully altered gases permeability tendency order from H2 > CH4 > CO2 > CO to H2 > CO2 > CO > CH4 which leads to better separation of the product from methane feed. Finally, hydrothermal stability test demonstrated that permeability loss in silica-zirconia CVD coated membrane for H2 is 45.7% after 48 h, while for silica CVD coated on the modified alumina approaches 92.5%. 相似文献
18.
D. Sanz-Villanueva D. Alique A.J. Vizcaíno R. Sanz J.A. Calles 《International Journal of Hydrogen Energy》2021,46(38):20198-20212
Thermal and mechanical resistances of palladium composite membranes prepared by Electroless Pore-Plating (ELP-PP) and containing SBA-15 as intermediate layer were improved by doping the silica material with Pd nuclei before its incorporation on the composite membrane. Textural properties of synthesized SBA-15 materials (both raw and doped ones) were analyzed by XRD, N2 adsorption-desorption at 77 K and TEM, while the main properties of the composite membrane were determined by SEM and gravimetric analyses. Moreover, membrane permeation tests were also carried out with pure gases, hydrogen and nitrogen, and binary mixtures of them at temperature of 400 °C and pressure driving forces in the range of 0.5–2.5 bar. The use of bare SBA-15 intermediate layer leads to the appearance of cracks on the Pd layer during permeation experiments at high temperature. In contrast, the use of Pd-doped SBA-15 particles avoids this problem, thus improving both thermal and mechanical resistances of the composite ELP-PP Pd-membrane. Following this preparation method, an estimated Pd thickness of 7.1 μm was obtained, reaching a hydrogen permeance of 3.81·10?4 mol s?1 m?2 Pa?0.5 and ensuring an ideal H2/N2 separation factor higher than 2550 at 400 °C. 相似文献
19.
《International Journal of Hydrogen Energy》2020,45(12):7488-7496
Palladium membranes used for hydrogen separation seemingly develop cavities filled with hydrogen, i.e. hydrogen bubbles, along the grain boundaries. These bubbles may represent initial stages of pinhole formation that lead to unselective leakage and compromise the long-term stability of the membranes. Alloying with Ag improves the permeability of Pd, but whether these H2 bubbles form in Pd-Ag membranes remained unknown. In this work, the microstructure of a Pd77Ag23 membrane was characterized by electron microscopy after H2 permeation testing for 50 days at 15 bar at temperatures up to 450 °C. The results show that Ag does not prevent bubbles from emerging along high-angle grain boundaries, but reduces the number of potential nucleation sites for cavity formation by supressing the development of dislocation networks when H-saturated Pd is cycled through the miscibility gap. Both magnetron-sputtered and electroless plated membranes are afflicted by H2 bubbles, thus their formation seems determined by intrinsic properties of the material independent of the fabrication technique. The qualitative discussion enables to point directions for enhancement of membrane stability. 相似文献
20.
J.E. Ramírez-Morales E. Tapia-Venegas N. Nemestóthy P. Bakonyi K. Bélafi-Bakó G. Ruiz-Filippi 《International Journal of Hydrogen Energy》2013
The ability of (dimethyl siloxane) (PDMS) and SAPO 34 membrane modules to separate a H2/CO2 gas mixture was investigated in a continuous permeation system in order to decide if they were suitable to be coupled to a biological hydrogen production process. Permeation studies were carried out at relatively low feed pressures ranging from 110 to 180 kPa. The separation ability of SAPO 34 membrane module appeared to be overestimated since the effect concentration polarization phenomena was not taken into consideration in the permeation parameter estimation. On the other hand, the PDMS membrane was the most suitable to separate the binary gas mixture. This membrane reached a maximum CO2/H2 separation selectivity of 6.1 at 120 kPa of feed pressure. The pressure dependence of CO2 and H2 permeability was not considerable and only an apparent slight decrease was observed for CO2 and H2. The mean values of permeability coefficients for CO2 and H2 were 3285 ± 160 and 569 ± 65 Barrer, respectively. The operational feed pressure found to be more adequate to operate initially the PDMS membrane module coupled to the fermentation system was 180 kPa, at 296 K. In these conditions it was possible to achieve an acceptable CO2/H2 separation selectivity of 5.8 and a sufficient recovery of the CO2 in the permeate stream. 相似文献