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题名: Impact of support mass flow resistance on low-temperature H-2 permeation characteristics of a Pd95Ag5/Al2O3 composite membrane
作者: Zeng, Gaofeng1;  Goldbach, Andreas1;  Xu, Hengyong1
关键词: PdAg membrane ;  alpha/beta Hydride phase transition ;  Temperature cycling ;  H-2 release ;  Support transport resistance
刊名: JOURNAL OF MEMBRANE SCIENCE
发表日期: 2009-01-20
DOI: 10.1016/j.memsci.2008.11.001
卷: 326, 期:2, 页:681-687
收录类别: SCI
文章类型: Article
WOS标题词: Science & Technology ;  Technology ;  Physical Sciences
类目[WOS]: Engineering, Chemical ;  Polymer Science
研究领域[WOS]: Engineering ;  Polymer Science
英文摘要: The permeation behavior of a 2.0 mu m thick Pd95Ag5/ceramic composite membrane was investigated between 403 K and 823 K. Above 460 K H-2 fluxes can be represented by an Arrhenius law with J(H2) = 1.6 +/- 0.1 Mol m(-2) s(-1) exp [-9.0 +/- 0.2 kJ mol(-1)/RT] at Delta P-H2 = 100 kPa with the initial ideal H-2/N-2 selectivity exceeding 4700 at 823 K. A discontinuity occurred in the H-2 flux between 455 K and 420 K due to the opening of the miscibility gap in the Pd95Ag5Hx phase diagram and the appearance of the beta Pd95Ag5 hydride phase. Below 420K H-2 fluxes can be represented by another Arrhenius law with J(H2) = 1.7 +/- 0.2 Mol m(-2) s(-1) exp [-7.2 +/- 0.3 kJ mol(-1) /RT] at Delta P-H2 = 100 kPa. Activation energies are consistent with diffusion limited H2 transport both above and below the permeation discontinuity. A gradual shift towards linear pressure dependence with decreasing temperature is attributed to an increasing impact of the mass flow resistance of the 2 mm thick ceramic support on the H-2 permeation rates at low temperatures. A steeper increase of the pressure exponent n upon appearance of the beta Pd95Ag5 hydride is associated with the lower hydrogen activity in this phase. The membrane exhibited good stability during 20 temperature cycles between 473 K and 673 K in H-2 atmosphere and 3 cycles down to room temperature in N-2, resulting only in a slight increase of the N-2 leak rate from 0.44 x 10(-3) Mol m(-2) s(-1) to 0.54 x 10(-3) Mol m(-2) s(-1) at 673 K and Delta P-N2 = 100 kPa. Monitoring of H-2 on the permeate side after switching from H-2 feed to N-2 purge streams showed that between 5 h at 673 K and 9 h at 523 K were required for a complete release of H-2 from the composite membrane. Analysis of the emitted H-2 volumes showed that the H-2 release on the permeate side was limited largely by the mass flow resistance of the porous ceramic support. H-2 released on the membrane feed side exceeded that on the permeate side by 1-2 orders of magnitude and originated mainly from the stainless steel reactor shell. As a consequence the hydrogen content of supported Pd and PdAg layers could remain above the threshold for embrittlement after switching to inert atmospheres if not sufficient time is allowed for H-2 release before cooling. (C) 2008 Elsevier B.V. All rights reserved.
关键词[WOS]: PALLADIUM MEMBRANE ;  HYDROGEN ;  THIN ;  SEPARATION ;  DIFFUSION ;  TRANSPORT ;  BEHAVIOR ;  ALLOYS
语种: 英语
WOS记录号: WOS:000263006500052
Citation statistics: 
内容类型: 期刊论文
URI标识: http://cas-ir.dicp.ac.cn/handle/321008/141554
Appears in Collections:中国科学院大连化学物理研究所_期刊论文

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作者单位: 1.Chinese Acad Sci, Dalian Inst Chem Phys, Dalian 116023, Peoples R China

Recommended Citation:
Zeng, Gaofeng,Goldbach, Andreas,Xu, Hengyong. Impact of support mass flow resistance on low-temperature H-2 permeation characteristics of a Pd95Ag5/Al2O3 composite membrane[J]. JOURNAL OF MEMBRANE SCIENCE,2009,326(2):681-687.
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