钙钛矿锚定纳米氧化铈及其化学链干重整性能

Perovsokite-anchored ceria for chemical looping dry reforming

化学链甲烷干重整(CL-DRM)可同时利用二氧化碳和甲烷两种温室气体,将其转化为可用于费托合成的合成气。采用溶胶凝胶法及浸渍法制备了一系列(Ni/CeO_(2))/ABO_(3)(钙钛矿型)氧载体,探究Ni/CeO_(2)负载对钙钛矿储氧性能的影响,揭示Ni/CeO_(2)负载量对La_(0.8)Sr_(0.2)FeO_(3)钙钛矿氧载体催化活性作用规律,进一步研究氧载体的化学链循环稳定性。结果发现,CeO_(2)与载体La_(0.8)Sr_(0.2)FeO_(3)相互作用有利于钙钛矿形成氧空位,从而增强其氧迁移能力。Ni/CeO_(2)的负载提高了氧载体的储氧性能,增强反应活性,降低了反应初始温度,但过高的负载量将导致甲烷裂解形成积碳。当Ni/CeO_(2)负载量为质量分数20%时,甲烷转化率高达82%,H_(2)/CO物质的量比为2.1,在30次氧化还原循环后结果稳定,表现出优异的氧化还原循环稳定性。此外,CeO_(2)粒径可显著影响金属Ni分散度。CeO_(2)粒径的减小增强了与金属Ni界面相互作用,提升了氧载体的反应活性,减少甲烷裂解。通过CeO_(2)粒径调控使氧载体的CH_(4)转化率达87%以上,CO选择性达90%以上,H_(2)/CO物质的量比为2.18,接近2.0的理想值。利用钙钛矿锚定活性物种制备复合氧载体的策略为实现化学链干重整的高性能提供了一条有效途径,高活性和高稳定性的复合金属氧化物氧载体的制备为相关领域储氧催化材料制备提供了参考借鉴。

Chemical looping dry reforming of methane(CL-DRM)is a process simultaneously utilizing two greenhouse gases,carbon dioxide,and methane,and converting them into syngas that can be used for Fischer-Tropsch synthesis.A series of(Ni/CeO_(2))/ABO_(3)(Perovskite-type)composite oxygen carriers were prepared by sol-gel and impregnation methods and the effects of Ni/CeO_(2) loading on the oxygen storage performance of perovsokite were investigated.The effects of different Ni/CeO_(2) loadings on the activity of La_(0.8)Sr_(0.2) FeO_(3) perovskites were explored and the cycling stability of the oxygen carriers was analyzed.It was found that the interaction of CeO_(2) with the carrier La_(0.8)Sr_(0.2) FeO_(3) favors the formation of oxygen vacancies in perovsokite,which enhances their oxygen mobility.The loading of Ni/CeO_(2) improved the oxygen storage performance of the oxygen carrier,lowering the initial reaction temperature and enhancing the reaction activity,however,a high loading would lead to methane cracking to form carbon deposits.The(Ni/CeO_(2))/La_(0.8)Sr_(0.2) FeO_(3) composite oxygen carrier reached 82%methane conversion with a 2.1 H_(2)/CO molar ratio when the Ni/CeO_(2) loading was 20%.Furthermore,the catalyst remained stable after 30 cycles and showed excellent cycling stability performance.In addition,CeO_(2) particle size can significantly affect the dispersion of the Ni phase.The reduction of CeO_(2) particle size enhances interfacial interaction with metal Ni,improves oxygen carrier reactivity,and reduces methane cracking.Modulating CeO_(2) particle size enabled the oxygen carrier to achieve over 87%CH_(4) conversion,over 90%CO selectivity,and a H_(2)/CO ratio of 2.18,close to the ideal value of 2.0.The strategy of preparing composite oxygen carriers with perovsokite-anchored active species offers an effective approach for high performance in chemical looping dry reforming.Additionally,the preparation of highly active and stable composite metal oxide oxygen carriers serves as a reference for oxygen storage catalytic materials in related fields.