Surface chemistry, structure, and reactivity
of multi-component spinel nanoparticles

@article{berger2024,

title = {Cu-doped perovskite-type oxides: A structural deep dive and examination of their exsolution behaviour influenced by B-site doping},

author = {Tobias Berger and Hedda Drexler and Thomas Ruh and Lorenz Lindenthal and Florian Schrenk and Johannes Bock and Raffael Rameshan and Karin Föttinger and Johanna Irrgeher and Christoph Rameshan},

doi = {10.1016/j.cattod.2024.114787},

year  = {2024},

date = {2024-07-01},

urldate = {2024-07-01},

journal = {Catalysis Today},

volume = {437},

number = {114787},

abstract = {Perovskite-type oxides have gained significant attention in the scientific community due to their unique properties and potential applications. Their ability to exsolve reducible B-site cations (e.g. Co, Ni, Cu) combined with their flexibility regarding A-site and B-site composition allows for the tailoring of novel catalytic materials. This study focuses on B-site doped perovskite-type oxides with a general formula of Nd_{0.6}Ca_{0.4}Fe_{1-x}Cu_{x}O_{3} and Pr_{0.6}Ca_{0.4}Fe_{1-x}Cu_{x}O_{3} (x = 0.0, 0.03, 0.05, 0.10) for potential use as a catalyst for Methanol Steam Reforming via the exsolution of catalytically active Cu nanoparticles. The atomic and electronic structure, morphology, and exsolution behaviour of these materials were investigated experimentally and with density functional theory, with a specific emphasis on the impact of B-site doping with varying Cu content as well as choice of A-site element. Both parameters influenced the crystal structure, surface area, and morphology of the materials. The exsolution behaviour of the materials was observed using in-situ XRD at DESY beamline P02.1 at PETRA III, with nanoparticles forming after reductive treatments on the host oxide surface. The quantity and size of the nanoparticles were found to be adjustable by selecting the A-site ion, doping content at the B-site, and the choice of reducing agent. Materials with higher Cu content on the B-site exhibited facilitated exsolution. Furthermore, exsolution was promoted with Nd as the A-site element compared to Pr. In conclusion, the controlled exsolution of Cu nanoparticles introduces Cu-doped perovskite-type oxides as promising candidates for developing novel catalytic systems. The findings underscore the importance of fine-tuning the oxide composition (A-site element, amount of B-site dopant) to achieve tailored exsolution of nanoparticles, which is crucial for rational material design. By leveraging this knowledge, catalysts with finely tuned properties can be created for specific applications and operational environments.},

keywords = {P10},

pubstate = {published},

tppubtype = {article}

}

@article{Latschka2023,

title = {Influence of hot liquid flowing water on Zeolite Y stability},

author = {Markus Latschka and Björn Wellscheid and Raffael Rameshan and Tobias Schöberl and Johannes Essmeister and Gernot Pacholik and Francesco Valentini and Laura Balta and Andreas Limbeck and Hanspeter Kählig and Karin Föttinger},

doi = {10.1016/j.micromeso.2023.112557},

year  = {2023},

date = {2023-04-15},

urldate = {2023-04-15},

journal = {Microporous and Mesoporous Materials},

volume = {354},

number = {112557},

abstract = {Zeolite Y is used in a wide field of catalysis because of its high surface area and strong acidity. Since flowing water is present in many catalytic liquid phase reactions, its impact was investigated. For that, the zeolite Y was treated with water at 200 °C and 42 bar in a flow reactor. The resulting characterization showed strong structural changes at high water flows. The typical zeolite structure was almost completely lost, but an amorphous phase similar to the faujasite framework was formed. Due to this, the characteristic micropores were destroyed (d = 0.7 nm, volume was reduced from 0.18 to 0.01 cm³/g) and small mesopores were created (d = 2–3 nm, volume was increased from 0.25 to 0.51 cm³/g). As a result, the specific surface area was not greatly reduced and was still at around 250 m²/g. In addition, the amount of octahedrally coordinated EFAl increased from 54 to 70% and a γ-Al_{2}O_{3} as well as a kaolinite phase was observed. The formed tetrahedrally coordinated EFAl is responsible for EFAl-OH groups, which are strong Brønsted acid sites. In general, the total acid sites of the zeolite Y were not strongly reduced and the ratio of Lewis to Brønsted acid sites slightly increased from 70:30% to 80:20%. For all Al species, the oxygen coordination was strongly distorted. After water treatment, on Si a large number of coordinated OSi and OAl groups were substituted with OH groups. The ratio of Si to Al decreased from 1 to 0.7, because Si was dissolved out of the zeolite by the water. On the surface, it was vice versa, there the Si accumulated (the Si/Al ratio increased from 0.2 to 0.8), presumably as silica gel.},

keywords = {P10},

pubstate = {published},

tppubtype = {article}

}

@article{TAMPIERI2022121889,

title = {Catalytic aldol condensation of bio-derived furanic aldehydes and acetone: Challenges and opportunities},

author = {Alberto Tampieri and Karin Föttinger and Noelia Barrabés and Francesc Medina},

url = {https://doi.org/10.1016/j.apcatb.2022.121889

https://www.sciencedirect.com/science/article/pii/S092633732200830X},

doi = {10.1016/j.apcatb.2022.121889},

year  = {2022},

date = {2022-08-24},

urldate = {2022-08-24},

journal = {Applied Catalysis B: Environmental},

volume = {319},

number = {121889},

abstract = {Bio-derived furfural and 5-hydroxymethylfurfural can be combined with acetone to yield aldol condensation products that may serve as biofuel and polymer precursors. We have explored different catalytic systems to obtain and purify each product in the most efficient way. The results of the catalytic tests of the cross-condensations and of the self-condensation of acetone allowed the comparison of the different reactivity of the two aldehydes. Online and in situ/operando ATR-IR was used to monitor the reaction over time and to study the interaction of the reaction species with the solid catalyst, especially the formation of deactivating organic matter that covers the surface, which is a major issue in heterogeneous condensation processes. In situ NMR was used to study the ongoing reaction, assessing its stereoselectivity, and to study the behavior of deuterated species in the catalytic system. Finally, the preparation of C14, a hetero-double-condensation product, was also explored.},

keywords = {P10},

pubstate = {published},

tppubtype = {article}

}