Impact of support mass flow resistance on low-temperature H-2 permeation characteristics of a Pd95Ag5/Al2O3 composite membrane

	Impact of support mass flow resistance on low-temperature H-2 permeation characteristics of a Pd95Ag5/Al2O3 composite membrane
	Zeng, Gaofeng; Goldbach, Andreas; Xu, Hengyong
刊名	journal of membrane science
	2009-01-20
卷号	326 期号:2 页码:681-687
关键词	PdAg membrane alpha/beta Hydride phase transition Temperature cycling H-2 release Support transport resistance
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.
WOS标题词	science & technology ; technology ; physical sciences
类目[WOS]	engineering, chemical ; polymer science
研究领域[WOS]	engineering ; polymer science
关键词[WOS]	palladium membrane ; hydrogen ; thin ; separation ; diffusion ; transport ; behavior ; alloys
收录类别	SCI
语种	英语
WOS记录号	WOS:000263006500052
公开日期	2015-11-17
内容类型	期刊论文
源URL	[http://159.226.238.44/handle/321008/141554]
专题	大连化学物理研究所_中国科学院大连化学物理研究所
作者单位	Chinese Acad Sci, Dalian Inst Chem Phys, Dalian 116023, Peoples R China
推荐引用方式 GB/T 7714	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.
APA	Zeng, Gaofeng,Goldbach, Andreas,&Xu, Hengyong.(2009).Impact of support mass flow resistance on low-temperature H-2 permeation characteristics of a Pd95Ag5/Al2O3 composite membrane.journal of membrane science,326(2),681-687.
MLA	Zeng, Gaofeng,et al."Impact of support mass flow resistance on low-temperature H-2 permeation characteristics of a Pd95Ag5/Al2O3 composite membrane".journal of membrane science 326.2(2009):681-687.