Trubkové La0.7Ca0.3Fe0.85Co0.15O3-d perovskitové membrany, Část II: Výkon a stabilita

Tubular La0.7Ca0.3Fe0.85Co0.15O3-d Perovskite Membranes, Part II: Performance and Stability

journal article - other

en

Oxygen permeability through the tubular La0.7Ca0.3Fe0.85Co0.15O3-d perovskite membrane prepared by thermoplastic extrusion was measured in the temperature range from 800 to 1040 degC in air/argon gradient and compared with oxygen permeability of planar membranes prepared by injection molding and cold isostatic pressing. Oxygen flux through the perovskite membranes was controlled by bulk diffusion of oxygen and was not limited by surface exchange reactions. The oxygen flux through perovskite membranes normalized to 1 mm wall thickness at 900 degC was 0.064 micromol cm-2 s-1. The activation energy of oxygen diffusion was 128 kJ mol-1. The tubular membrane was tested in a reactor for partial oxidation of methane for more than 1900 hours. The oxygen flux decreased gradually during the test from 1.5 to 1 micromol cm-2 s-1. The methane conversion could be adjusted to 83-88%, with the CO selectivity in the same range. After the test a degradation of the perovskite structure of the membrane was observed. A possible mechanism for the phase degradation and segregation was proposed.

Kyslíková propustnost trubkové La0.7Ca0.3Fe0.85Co0.15O3-d perovskitové membrány připravené termoplastickým vytlačováním byla měřena v teplotním rozsahu od 800 do 1040 degC v gradientu vzduch/argon a srovnána s kyslíkovou propustností rovinných membrán připravených injekčním vstřikováním a isostatickým lisováním za studena. Kyslíkový tok přes perovskitové membrány byl řízen objemovou difůzí a nebyl limitován povrchovými výměnnými reakcemi. Kyslíkový tok přes perovskitovou membránu normalizovanou na tloušťku stěny 1mm při 900 degC byl 0,064 micromol cm-2 s-1. Aktivační energie kyslíkové difůze byla 128 kJ mol-1. Trubková membrána byla testována v reaktoru pro částečnou oxidaci metanu po dobu více než 1900 hodin. Kyslíkový tok klesal v průběhu testu z 1,5 na 1 micromol cm-2 s-1. Konverze metanu mohla být upravena na 83-88%, s CO selektivitou ve stejném rozsahu. Po testu byla pozorována degradace perovskitové struktury membrány. Byl navržen možný mechanismus fázové degradace a segregace.

Oxygen permeability through the tubular La0.7Ca0.3Fe0.85Co0.15O3-d perovskite membrane prepared by thermoplastic extrusion was measured in the temperature range from 800 to 1040 degC in air/argon gradient and compared with oxygen permeability of planar membranes prepared by injection molding and cold isostatic pressing. Oxygen flux through the perovskite membranes was controlled by bulk diffusion of oxygen and was not limited by surface exchange reactions. The oxygen flux through perovskite membranes normalized to 1 mm wall thickness at 900 degC was 0.064 micromol cm-2 s-1. The activation energy of oxygen diffusion was 128 kJ mol-1. The tubular membrane was tested in a reactor for partial oxidation of methane for more than 1900 hours. The oxygen flux decreased gradually during the test from 1.5 to 1 micromol cm-2 s-1. The methane conversion could be adjusted to 83-88%, with the CO selectivity in the same range. After the test a degradation of the perovskite structure of the membrane was observed. A possible mechanism for the phase degradation and segregation was proposed.

perovskite, membrane, structure, degradation

2006

01.01.2006

The American Ceramic Society

0002-7820

Journal of the American Ceramic Society

89

3

955–959

5