Tuning the dimensionality of layered Srn+1Tin-xNixO3n+1 perovskite structures for improved activity in syngas generation

Interest in perovskite type oxides is growing due to their versatile catalytic applications. A series of Ruddlesden-Popper (RP) type layered perovskite oxides Srn+xTin-xNixO3n+1 were prepared and evaluated for their catalytic activity in steam reforming, CO2 reforming and bi-reforming of methane. These materials, prepared through citrate gel method were characterized to understand their structure and Ni reducibility. Substitution of Ni in RP phases was established through refinement of XRD powder pattern. During methane reforming, the catalytic activity increased with the order of RP phase of SrTi1-xNixO3-delta (n = infinity). TPR results show variation in Ni reducibility with the order of RP phase, while TPD-O-2 study helped to estimate oxygen vacancies. These vacancies seem to influence catalytic activity during methane reforming. Transient pulse experiments show that CO2 dissociates over oxygen vacancies to give CO and oxygen, with later replenishing lattice oxygen in SrTi0.8Ni0.2O3-delta (n = infinity) phases. Highly labile oxygen vacancies generated in the bulk of SrTi0.8Ni0.2O3-delta must be migrating to the surface, helping in the removal of coke formed. Characterization of catalysts after reaction helped in better understanding of coke precursors. (C) 2018 Elsevier Inc. All rights reserved.