硅酸盐学报

甲烷干重整(DRM)反应是一种将甲烷和二氧化碳转化为合成气的重要技术，具有显著的环保和经济效益。然而，DRM反应面临二氧化碳成本高等问题，本工作提出了一种基于高温混合导体二氧化碳渗透膜(MOCC膜)反应器的新型技术路线，可利用工业气源捕集的二氧化碳原位与DRM反应耦合生成合成气，实现了二氧化碳的捕集与资源化利用及甲烷的高效转化。膜反应器采用氧化钐掺杂的氧化铈多孔骨架复合锂钠二元共晶碳酸盐双相膜，负载LaNi_1–xCu_xO_3–δ钙钛矿型催化剂。850℃、负载LaNi_0.8Cu_0.2O_3–δ催化剂时，针对模拟烟气和模拟碳基固体氧化物燃料电池(SOFC)阳极尾气2种气源，甲烷转化率分别达到97.31%和95.51%，二氧化碳转化率分别达到98.34%和78.49%，一氧化碳的生成速率分别为2.39 mL·cm^–2·min^–1和2.93 mL·cm^–2·min^–1，氢气的生成速率分别为1.44 m L·cm^–2·min^–1和1.38 m L·cm^–2·min^–1。长期稳定性测试表明，该膜反应器在60 h内性能无明显衰减，展现出良好的应用前景。本工作为二氧化碳捕集与甲烷高效转化提供了新的技术路径，对实现“双碳”目标具有重要意义。

Introduction Methane as a significant energy and chemical raw material boasts higher energy density,lower pollution,and abundant reserves,compared to coal or petroleum.The reforming of methane to syngas is one of the key technologies for its clean and efficient utilization.The produced syngas can be applied in hydrogen production,chemical synthesis,combustion,and as fuel gas for solid oxide fuel cells(SOFC).The chemical energy in the fuel gas can be directly converted into electrical energy when produced syngas used as SOFC fuel gas,serving as an important pathway for the clean and efficient utilization of carbon-based fuels.The dry reforming of methane(DRM) is a promising technology that converts methane and carbon dioxide into syngas(i.e.,CO and H₂),offering notable environmental and economic benefits.However,the DRM reaction is confronted with some challenges like high CO₂costs and propensity for carbon deposition.This paper was to propose a technological approach based on a mixed-conductive CO₂permeable membrane reactor(i.e.,MOCC membrane) to realize the efficient conversion of CH4 and the capture and resourceful utilization of CO₂.The membrane reactor used a dual-phase membrane composed of samarium-doped ceria(SDC) and lithium-sodium eutectic carbonate(MC) when loaded with the LaNi_0.8Cu_0.2O_3-δ(LNC) catalyst,significantly enhancing the CO₂permeation flux and the catalytic performance of the DRM reaction.Methods A dual-phase MOCC membrane composed of samarium-doped ceria(SDC) and lithium-sodium binary eutectic carbonate(Li_0.52Na_0.48)₂CO₃ was fabricated.The SDC porous matrix was synthesized via coprecipitation and subsequent impregnation with molten carbonate to form a dense structure.A Cu-doped LaNiO₃ perovskite catalyst(LaNi_0.8Cu_0.2O_3-δ) was prepared by a coprecipitation method and loaded onto the membrane reactor.The membrane s CO₂ permeation flux was evaluated under simulated flue gas and SOFC anode exhaust conditions.The catalytic performance,including CH₄ conversion,H₂/CO production rates,and stability,was systematically tested at 650-850℃.The samples were characterized by X-ray diffraction(XRD),scanning electron microscopy(SEM),and gas chromatography,respectively.Results and discussion The catalytic performance of LaNi_1-xCu_xO_3-δ(LNC) catalysts with varying Cu doping levels(x=0,0.2,0.4,0.6) is systematically evaluated in a fixed-bed reactor for methane dry reforming(DRM).At 850℃,LaNi_0.8Cu_0.2O_3-δ catalyst exhibits the maximum CH₄ conversion rate(i.e.,99.8%) and CO₂ conversion rate(i.e.,98.4%),along with optimal H₂ and CO production rates of 1.36 and 1.50 mL·min^-1,respectively.In contrast,undoped LaNiO₃ catalyst shows inferior activity(i.e.,CH₄ conversion:～85%),highlighting the critical role of Cu doping in enhancing catalytic performance.The improved activity is attributed to Cu incorporation promoting oxygen vacancy formation and lattice oxygen mobility,suppressing carbon deposition and enhanced reaction kinetics.Note that the excessive Cu doping(x≥0.4) leads to reduced activity due to the partial blockage of active sites and structural instability,underscoring the importance of balanced Cu substitution.The dual-phase mixed oxygen and carbonate ionic conductor(MOCC) membrane,composed of SDC and lithium-sodium eutectic carbonate(Li_0.52Na_0.48)₂CO₃,has robust CO₂ permeation capabilities.Under non-reactive conditions,the CO₂ flux increases from 0.27 to 0.90 mL·cm^-2·min^-1 as the temperature increases from 650 to 850 ℃,with an activation energy of 51.93 kJ·mol^-1,indicating a thermally driven permeation mechanism.When coupled with DRM,the CO₂ flux surges to 1.52 mL·cm^-2·min^-1 at 850℃,driven by the enhanced CO₂ partial pressure gradient resulting from continuous CO₂ consumption in the reaction.This synergy between CO₂ capture and conversion significantly outperformes conventional fixed-bed reactors,where CO₂ utilization is limited by equilibrium constraints.In the integrated membrane reactor loaded with LaNi_0.8Cu_0.2O_3-δ,the exceptional DRM performance is achieved under simulated flue gas 60% N_2-40% CO₂) and SOFC anode exhaust(i.e.,40% CO₂,2% H₂,2% CO) conditions.At 850℃,CH₄ conversions reach 97.31% and 95.51%,respectively,with CO and H₂ production rates of 2.39 and 1.44 mL·cm^-2·min^-1(flue gas) and 2.93 and1.38 mL·cm^-2·min^-1(SOFC exhaust).The H₂/CO ratio(i.e.,～0.6-0.7) deviates slightly from the stoichiometric value of 1,likely due to the reverse water-gas shift(RWGS) reaction at elevated temperatures.The results of long-term stability tests at 825℃ for 60 h reveal no significant degradation in CH₄ conversion(i.e.,～97%) or syngas production rates,indicating the system's robustness.The analysis of SEM images and XRD patterns indicate the absence of carbon deposits and preserved catalyst phase structure,thus validating the anti-coking properties of the Cu-doped perovskite and the membrane's thermal stability.Compared to the existing studies,this work develops a membrane reactor technology via achieving higher CO₂ permeation fluxes and catalytic efficiencies.LaNi_0.8Cu_0.2O_3-δ catalyst has a higher activity with a prolonged stability.Furthermore,the dual-phase membrane's unique ion-conduction mechanism circumventes the trade-off between selectivity and permeability in conventional membranes,offering a scalable solution for industrial CO₂ capture and utilization.These results indicate a potential of integrating advanced perovskite catalysts with MOCC membranes to achieve efficient,stable,and economically viable DRM systems.Conclusions This work presented a breakthrough in coupling CO₂ capture with DRM using a MOCC membrane reactor.When loaded with LaNi_0.8Cu_0.2O_3-δ catalyst,the membrane reactor could enhance the CO₂ permeation flux and the catalytic performance of the DRM reaction.At 850℃,employing the LaNi_0.8Cu_0.2O_3-δ catalyst,methane conversion rates achieved were 97.31% and 95.51%for simulated flue gas and SOFC anode off-gas,respectively.Correspondingly,CO₂ conversion rates were 98.34% and 78.49%,while the production rates of CO were 2.39 and 2.93 mL·cm^-2·min^-1,and those of hydrogen were 1.44 and 1.38 mL·cm^-2·min^-1,respectively.The results of long-term stability tests indicated that the membrane reactor had a stable performance for over 60 h,demonstrating promising application prospects.The technology could reduce CO₂ emissions and convert waste gases into valuable syngas,aligning with global carbon-neutral goals.A future research could focus on scaling up the reactor and optimizing operational parameters for broader implementation.