The permeability and stability of Sm0.7Sr0.3CoO3−δ (SSCO) regarding the special requirements for carbon capture and storage (CCS) application were investigated. Pure CO2 was used as the sweep gas at 900 °C, leading to that the oxygen permeation flux decreases by about 34 %. Several cycles of changing the sweep gas between helium and CO2 indicate the good reversibility of this degradation. Both carbonate formation and adsorption of CO2 on the membrane surface are responsible for the degradation of the membrane performance. The better CO2 resistance results from the substitution of Sm for Sr due to the higher acidity of Sm2O3 (1.278) than that of SrO (0.978) and a discontinuous layer of carbonate.

•We develop a novel and efficient tubular oxygen-permeable membrane reactor.•A cylindrical Ni-based monolithic catalyst around the membrane tube was used.•A conventional Ni-based catalyst-bed at the downstream was coupled.•The novel reactor was applied onto the partial oxidation of CH4 in COG.•Long-term operation test was conducted.Dense BaCo0.7Fe0.2Nb0.1O3−δ (BCFNO) membrane tubes were prepared by slip casting and readily brazed to 310S stainless steel supports using a silver-based alloy. A novel tubular membrane reactor was constructed by placing a cylindrical Ni-based monolithic catalyst coaxially around the tubular membrane and a conventional Ni-based catalyst-bed apart from the membrane tube. The novel membrane reactor was successfully applied to partial oxidation of CH4 in coke oven gas (COG). At 850 °C, 94% of CH4 conversion, 93% of H2 and as high as 11.3 cm3 cm−2 min−1 of oxygen permeation flux were obtained. The experimental H2 and CO selectivity and CH4 conversion were close to the thermodynamically predicated ones. There was a good match in the coefficient of thermal expansion (CTE) among BCFNO membrane, Ag-based alloy and 310S metal support. Long-term operation test results indicate that the novel tubular BCFNO membrane reactor exhibited not only high activity but also good stability for the partial oxidation of CH4 in COG to syngas.

The effect of Nb doping on the oxygen permeation and stability of SrCo0.8Fe0.2O3−δ (SCFO) was investigated comprehensively. Cubic perovskite phase was formed in SrCo0.7Fe0.2Nb0.1O3−δ (SCFNO). The SCFNO with a thickness of 1 mm had a high level of oxygen permeation flux of 1.4 ml·min−1·cm−2 at 850 °C under air/He gradient. The bulk diffusion is the rate-limiting step in overall oxygen permeation mechanism for SCFNO when the thickness is higher than 1.0 mm. The partial substitution of Nb for Co suppresses the transition of oxygen vacancies order/disorder proven by DSC measurement and enhances the phase stability under low oxygen partial pressure. During long-term tests under low oxygen pressure, the SCFNO exhibites structural stability and stable oxygen permeation. It is proved that substitution of Nb for Co is an effective way to improve the properties of SCFO.

Perovskite-type oxygen-permeable membrane reactors of BaCo0.7Fe0.2Nb0.1O3−δ (BCFNO) packed with Ru-based catalyst had high oxygen permeability and could be used for hydrogen production by partial oxidation of methane in coke oven gas (COG). At 1173 K, 94% of methane conversion, 85% of H2 selectivity, 107% of CO selectivity, and as high as 15.4 mL·cm−2·min−1 of oxygen permeation flux were obtained. The BCFNO membrane itself had poor catalytic activity to partial oxidation of CH4 in COG. During continuous operation for 70 h at 1173 K, no degradation of the membrane reaction performance was observed. XRD and SEM characterization also demonstrated that the BCFNO membrane reactor exhibited good stability in partial oxidation of methane in COG.

Catalysts of Ni/Mg(Al)O promoted with lanthanum and cerium were tested in a BaCo0.7Fe0.2Nb0.1O3-δ (BCFNO) membrane reactor by catalytic partial oxidation of simulated hot coke oven gas (COG) with toluene as a model tar compound under atmospheric pressure. Analysis of the catalysts suggested that the hydrotalcite precursor after thermal treatment lead to a good dispersion of nickel forming the solid solution NiO−MgO and spinel (Ni,Mg)Al2O4. The promoted catalysts had higher oxygen permeation flux, better catalytic activity, and better resistance to carbon formation, which will be promising catalysts in the catalytic partial oxidation reforming of hot COG.

Hydrogen production from simulated hot coke oven gas (HCOG) was investigated in a BaCo0.7Fe0.2Nb0.1O3−δ (BCFNO) membrane reactor combined with a Ni/Mg(Al)O catalyst by the partial oxidation with toluene as a model tar compound under atmospheric pressure. The reaction results indicated that toluene was completely converted to H2 and CO in the catalytic reforming of the simulated HCOG in the temperature range from 825 to 875 °C. Both thermodynamically predicated values and experimental data showed that the selective oxidation of toluene took precedence over that of CH4 in the reforming reaction. At optimized reaction conditions, the dense oxygen-permeable membrane has an oxygen permeation flux around 12.3 mL cm−2 min−1, and a CH4 conversion of 86%, a CO2 conversion of 99%, a H2 yield of 88%, and a CO yield of 87% have been achieved. When the toluene and methane were reformed, the amount of H2 in the reaction effluent gas was about 2 times more than that of original H2 in simulated HCOG. The results reveal that it is feasible for hydrogen production from HCOG by reforming hydrocarbon compounds in a ceramic oxygen-permeable membrane reactor.

The total conductivity, oxygen sorption property, oxygen permeability and stability of pure perovskite-type oxide BaCo0.7Fe0.2Nb0.1O3−δ (BCFNO) in real operating conditions were investigated. Its total conductivity was measured to be 3.6 S·cm−1 at 600°C. Though the total conductivity of the BCFNO membrane is much smaller than that of the Ba0.5Sr0.5Co0.8Fe0.2O3−δ (BSCFO) membrane, the oxygen permeability of the BCFNO membrane is similar to that of the BSCFO membrane. SEM observation and EDX analysis of the BCFNO and BSCFO membranes indicated that no segregation of metal ions was found for the used BCFNO membrane while the original perovskite phase of BSCFO decomposed under the experimental condition. The experimental results of oxygen permeability and stability were consistent with the analysis on the oxygen sorption property of perovskites.

To maximize hydrogen production from coke oven gas (COG), partial oxidation of methane in COG was studied thermodynamically and experimentally. Thermodynamic analysis indicates that an optimal hydrogen yield of 1.04–1.10 mole per mole of the consumed COG can be achieved when the initial ratio of O2 and CH4 is 0.57–0.46 in a temperature range of 800–900 °C, and the corresponding amplification of original hydrogen in COG reaches 1.8–1.9 times. The amplification of original hydrogen was carried out in a BaCo0.7Fe0.2Nb0.1O3−δ (BCFNO) membrane reactor, and the hydrogen yield in the lab scale was about 80% more than that of original H2 in model COG. In a large hydrogen content in COG, the ceramic membrane reactors made from perovskite mixed-conducting oxygen-permeable materials must have higher stability to withstand the harsh reduction condition.

A gas-tight BaCo0.7Fe0.2Nb0.1O3-δ (BCFNO) tubular membrane was fabricated by hot pressure casting. And a membrane reactor with BCFNO tubular membrane and Ag-based sealant was readily constructed and applied to partial oxidation of CH4 in coke oven gas. At 875 °C, 95% of methane conversion, 91% of H2 and as high as 10 ml·cm−2 ·min−1 of oxygen permeation flux were obtained. There was a good match in the coefficient of thermal expansion between Ag-based alloy and BCFNO membrane materials. The tubular BCFNO membrane reactor packed with Ni-based catalysts exhibited not only high activity but also good stability in hydrogen-enriched coke oven gas (COG) atmosphere.