Enhancing co‐production of H₂ and syngas via water splitting and POM on surface‐modified oxygen permeable membranes

Abstract

In this paper, we report a detailed study on co-production of H 2 and syngas on La 0.9 Ca 0.1 FeO 3-δ (LCF-91) membranes via water splitting and partial oxidation of methane (POM), respectively. A permeation model shows that the surface reaction on the sweep side is the rate limiting step for this process on a 0.9 mm-thick dense membrane at 990 o C. Hence, sweep side surface modifications such as adding a porous layer and nickel catalysts were applied; the hydrogen production rate from water thermolysis is enhanced by two orders of magnitude to 0.37 μmol/cm 2 •s compared with the results on the unmodified membrane. At the sweep side exit, syngas (H 2 /CO = 2) is produced and negligible solid carbon is found. Yet near the membrane surface on the sweep side, methane can decompose into solid carbon and hydrogen at the surface, or it may be oxidized into CO and CO 2 , depending on the oxygen permeation flux.

Hydrogen‐assisted Carbon Dioxide Thermochemical Reduction on La0.9Ca0.1FeO3−δ Membranes: A Kinetics Study

“…A button‐cell membrane reactor with axis‐symmetric reverse flow was used to study CO 2 dissociation with various reactive sweep gases (Figure ). The detailed construction and use of the reactor can be found in our previous work . Temperature is monitored by K‐type thermocouples and controlled by a PID controller, whereas the gas species are examined using two gas chromatographs (490 Micro GC and Shimadzu GC2014) with TCD detectors.…”

“…This oxygen incorporation reaction is similar to those for O 2 or H 2 O incorporation in LCF‐91 materials.…”

“…Alternatives can use a non‐reactive sweep gas or a vacuum pump on the sweep side. Previous studies have shown the intensification of water splitting and partial oxidation of methane on an LCF‐91 membrane, and confirmed that the former can be enhanced by a methane partial‐oxidation reaction on the sweep side (the formation of syngas with H 2 /CO=2) . In this study, carbon monoxide is first used as the reactive sweep gas (by design) to quantify the oxygen transport kinetics, in other words, the forward reaction CO 2 →CO+0.5 O 2 on the feed side surface and the reverse of the same reaction on the sweep side surface.…”

“…As a result, the slope of J decreases as shown in Figure a. Similar trends were observed using water is the oxygen source, whereby fluxes flatten out at higher fuel concentrations …”

“…Examining the surface reaction kinetics and the oxygen transport process can help identify the limiting steps and facilitate the development of this CO 2 thermochemical reduction technology. Flux models have been developed for oxygen separation and water splitting on an oxygen‐permeable membrane . Our paper represents one of the first attempts to model CO 2 thermochemical reduction supported by an isothermal membrane reactor, and the results presented herein successfully describe the trends observed in the experiments and shows directions for flux improvement.…”