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采用SrFe0.6Cu0.3Ti0.1O3?δ混合导体透氧膜组装成膜催化反应器,进行甲烷部分氧化制合成气反应,考察了反应温度、空速、催化剂粒径等条件的影响,并分析了反应气氛引起的透氧膜结构变化情况。结果表明,在膜反应器内,催化反应与透氧过程存在相互制约和相互促进的关系。在膜反应器内进行甲烷部分氧化反应后,透氧膜的两侧表面均发生蚀刻现象,结晶度显著降低,反应侧蚀刻现象较为严重,膜表面形成了疏松的多孔层,反应气氛使膜表面晶体结构发生了较大改变,Sr容易从钙钛矿结构中析出并与CO2结合形成SrCO3,Sr的析出导致组成不平衡,促进了钙钛矿结构分解及其他物相的产生。 相似文献
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为开发稳定性和透氧量俱佳并适用于甲烷部分氧化反应(POM)的透氧膜材料,采用溶胶凝胶工艺合成了具有纯相钙钛矿结构的BaCe0.1Co0.4Fe0.5O3-δ混合导体陶瓷材料。POM操作结果表明:BaCe0.1Co0.4Fe0.5O3-δ膜反应器透氧量高于同类材料,875℃时透氧量达到了8.9 mL/(cm2.m in)。在1 000 h寿命实验中,膜反应器各项反应指标没有出现任何衰减,反应性能稳定,甲烷转化率和CO的选择性都在97%以上。SEM表征表明,反应后膜片表面微观结构的变化虽然不可避免,但是其仍然保持比较完整的结构。因此,该材料良好的透氧量和稳定性说明其具有较好的应用前景。 相似文献
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引 言钙钛矿型致密透氧膜在高温下具有氧离子、电子混合导电性 .当膜两侧存在氧分压梯度时 ,高压侧的氧在膜表面经化学吸附解离成氧离子、电子 ,于膜主体内扩散至另一侧 ,并重新结合、脱附至低氧压体系 .将致密透氧膜反应器用于甲烷部分氧化制合成气反应为天然气利用开辟了一条崭新的路径 ,近年来受到普遍关注 .该过程集空分与反应于一体 ,降低了大量的操作成本 ,通过膜壁控制氧气的进料有效控制了反应进程 .提高膜的透氧量 ,解决还原性气氛下膜的稳定性等问题 ,是该过程实现工业化的关键 .Balachandrand[1] 、Tsai[2 ] … 相似文献
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Dense membrane with the composition of SrFe0.6Cu0.3Ti0.1O3-δ (SFCTO) was prepared by solid state reaction method. Oxygen permeation flux through this membrane was investigated at operating temperature ranging from 750℃ to 950℃ and different oxygen partial pressure. XRD measurements indicated that the compound was able to form single-phased perovskite structure in which part of Fe was replaced by Cu and Ti. The oxygen desorption and the reducibility of SFCTO powder were characterized by thermogravimetric analysis and temperature programmed reduction analysis, respectively. It was found that SFCTO had good structure stability under low oxygen pressure at high temperature. The addition of Ti increased the reduction temperature of Cu and Fe. Performance tests showed that the oxygen permeation flux through a 1.5mm thick SFCTO membrane was 0.35-0.96ml·min1·cm-2 under air/helium oxygen partial pressure gradient with activation energy of 53.2kJ·mol-1. The methane conversion of 85%, CO selectivity of 90% and comparatively higher oxygen permeation flux of 5ml·min-1·cm2 were achieved at 850℃, when a SFCTO membrane reactor loaded with Ni-Ce/Al2O3 catalyst was applied for the partial oxidation of methane to syngas. 相似文献
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Dense planar Ba0.15Ce0.85FeO3−δ (BCF1585) membrane reactors were investigated to produce syngas from methane. Firstly, the membrane itself catalytic activity
to methane was investigated using a blank BCF1585 without any catalysts. Then a LiLaNi/γ-Al2O3 catalyst was packed on the BCF1585 membrane surface to test the synergetic effects of the membrane and catalyst. It was found
that the membrane itself has a poor catalytic activity to methane. The main products are CO2 and C2, and methane conversion is low due to the low oxygen permeation flux. However, after the catalyst was packed on the membrane
surface, both methane conversion and oxygen permeation flux were greatly improved by the synergetic effect between the membrane
and catalyst. Carbon monoxide selectivity reached at 96% with methane conversion of up to 96%. The oxygen permeation flux
reached at 3.0 mL/cm2 min at 850 °C for a 1.5 mm disk membrane and can effectively be increased by reducing the thickness of the membranes. After
operation for 140 h at 850 °C, the used membrane was examined with SEM and EDXS. The results revealed that the decomposition
of the membrane materials could not be avoided under such conditions. Oxygen partial pressure gradient across the membranes
is suggested as a critical factor to accelerate the kinetic decomposition of the materials. 相似文献
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Design of mixed conducting ceramic membranes/reactors for the partial oxidation of methane to syngas
The performance of mixed conducting ceramic membrane reactors for the partial oxidation of methane (POM) to syngas has been analyzed through a two‐dimensional mathematical model, in which the material balance, the heat balance and the momentum balance for both the shell and the tube phase are taken into account. The modeling results indicate that the membrane reactors have many advantages over the conventional fixed bed reactors such as the higher CO selectivity and yield, the lower heating point and the lower pressure drop as well. When the methane feed is converted completely into product in the membrane reactors, temperature flying can take place, which may be restrained by increasing the feed flow rate or by lowering the operation temperature. The reaction capacity of the membrane reactor is mainly determined by the oxygen permeation rate rather than by the POM reaction rate on the catalyst. In order to improve the membrane reactor performance, reduction of mass transfer resistance in the catalyst bed is necessary. Using the smaller membrane tubes is an effective way to achieve a higher reaction capacity, but the pressure drop is a severe problem to be faced. The methane feed velocity for the operation of mixed conducting membrane reactors should be carefully regulated so as to obtain the maximum syngas yield, which can be estimated from their oxygen permeability. The mathematical model and the kinetic parameters have been validated by comparing modeling results with the experimental data for the La0.6Sr0.4Co0.2Fe0.8O3‐α (LSCF) membrane reactor. © 2009 American Institute of Chemical Engineers AIChE J, 2009 相似文献
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Dense membrane with the composition of SrFe0.6Cu0.3Ti0.1O3-δ (SFCTO) was prepared by solid state reaction method. Oxygen permeation flux through this membrane was investigated at operating temperature ranging from 750℃ to 950℃ and different oxygen partial pressure. XRD measurements indicated that the compound was able to form single-phased perovskite structure in which part of Fe was replaced by Cu and Ti. The oxygen desorption and the reducibility of SFCTO powder were characterized by thermogravimetric analysis and temperature programmed reduction analysis, respectively. It was found that SFCTO had good structure stability under low oxygen pressure at high temperature. The addition of Ti increased the reduction temperature of Cu and Fe. Performance tests showed that the oxygen permeation flux through a 1.5 mm thick SFCTO membrane was 0.35-0.96 ml·min ^-1·cm^-2 under air/helium oxygen partial pressure gradient with activation energy of 53.2 kJ·mol^-1. The methane conversion of 85%, CO selectivity of 90% and comparatively higher oxygen permeation flux of 5 ml·min^-1·cm^- 2 were achieved at 850℃, when a SFCTO membrane reactor loaded with Ni-Ce/Al2O3 catalyst was applied for the partial oxidation of methane to syngas. 相似文献
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考察LiLaNiO_x/γ—Al_2O_3催化剂对甲烷加压[(0.2~1.0)MPa]部分氧化制合成气反应的催化性能。结果表明,LiLaNiO_x/γ—Al_2O_3催化剂具有优良的甲烷部分氧化催化性能,在850℃和1.0 MPa条件下,甲烷转化率和CO选择性分别达76.2%和82.5%。在100 h连续实验中,反应活性及选择性保持不变,显示出较高的催化稳定性。采用XRD、XPS和TG—DTA方法对反应前后催化剂的晶体结构、表面性能以及抗积炭性能进行表征,结果表明,LiLaNiO_x/γ-Al_2O_3催化剂具有较高的结构稳定性和抗积炭性能。 相似文献
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Jun Tang Yanying Wei Lingyi Zhou Zhong Li Haihui Wang 《American Institute of Chemical Engineers》2012,58(8):2473-2478
A novel K2NiF4‐type oxide based on (Pr0.9La0.1)2(Ni0.74Cu0.21Ga0.05)O4+δ (PLNCG) dense mixed conducting ceramic membrane was successfully prepared through a sol–gel route. The oxygen permeation flux through the membrane swept by pure CO2 was comparative to that swept by He. The oxygen permeation and the stability of PLNCG under pure CO2 were investigated in detail. A membrane with a thickness of 0.8 mm was steadily operated for 230 h with a constant oxygen permeation flux of 0.32 mL/(min cm2) at 975°C using pure CO2 as sweep gas. X‐ray diffraction shows that PLNCG can maintain its fluorite phase, and no carbonates were observed, even when it was exposed to pure CO2 for a long time. © 2011 American Institute of Chemical Engineers AIChE J, 58: 2473–2478, 2012 相似文献
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S. Pei M. S. Kleefisch T. P. Kobylinski J. Faber C. A. Udovich V. Zhang-McCoy B. Dabrowski U. Balachandran R. L. Mieville R. B. Poeppel 《Catalysis Letters》1994,30(1-4):201-212
In the course of generating synthesis gas (H2, CO) from methane, we have observed two types of fractures occurring on the Sr(Co, Fe)Ox-type oxygen membrane reactors. The first type occurred shortly after the reaction started and the second type often occurred days after the reaction. To determine the causes of these fractures, we have examined the starting material and fractured membranes using a combination of X-ray diffraction and thermogravimetric analyses. We found that the first type of fracture was the consequence of an oxygen gradient in the membrane, pointing from the reaction side to the air side. This causes a lattice mismatch inside the membrane, leading to fracture. The second type of fracture, however, was the result of a chemical decomposition. We found that the Sr(Co, Fe)Ox-type membrane had been reduced to SrCO3, and elemental Co and Fe by the synthesis gas generated in the reaction. The decomposition causes enormous expansion leading to a large crack along the axis of tube. 相似文献
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Haihui Wang Armin Feldhoff Jürgen Caro Thomas Schiestel Steffen Werth 《American Institute of Chemical Engineers》2009,55(10):2657-2664
A BaCoxFeyZrzO3?δ (BCFZ) perovskite hollow fiber membrane was used to construct reactors for the partial oxidation of methane (POM) to syngas. The performance of the BCFZ fibers in the POM was studied (i) without any catalyst, (ii) with catalyst‐coated fibers, and (iii) with catalyst packed around the fibers. In addition to the performance in the POM, the stability of the BCFZ hollow fiber membranes was investigated for the different catalyst arrangements. Best stability of the BCFZ hollow fiber membrane reactor in the POM could be obtained if the reforming catalyst is placed behind the oxygen permeation zone. It was found that a direct contact of the catalyst and the fiber must be avoided which could be achieved by coating the fiber with a gold film. © 2009 American Institute of Chemical Engineers AIChE J, 2009 相似文献