Study of Cu-Zn and Au/TiO2 Catalysts on Anodized Aluminum Monoliths for Hydrogen Generation and Purification

This work reports the preparation of Cu-Zn and Au/TiO2 catalysts on anodized aluminum monoliths(AAM). The structured catalysts were studied for the generation of H2 by methanol steam reforming (MSR) and its purification by preferential oxidation of CO (CO-PrOx). Initially, it was possible to generate a surface with whiskers and larger surface area by hydrothermal treatment of the AAM. Subsequently, the structured catalysts were synthesized by incipient wetness impregnation (IWI) and ydrothermal synthesis (HS). IWI synthesis allowed for the deposition of a larger amount of catalytic material than HS, with very good adhesion. The TiO2-IWI structured catalyst presented a homogeneous catalytic coating, with the presence of agglomerated particles. On theother hand, Cu-Zn-IWI showed good dispersion of the deposited particles with a homogeneous surface coating. EDX analysis corroborated the presence of Ti, Cu and Zn in all the catalytic surfaces. The incorporation of Au over TiO2-IWI structured catalysts was successfully performed by IWI using a colloidal solution of gold nanoparticles.MSR was studied over the developed metallic monoliths functionalized with Cu-Zn by the IWI method. The samples showed promising results in terms of activity, selectivity, and stability. Both diluted and concentrated methanol + water feeds were assayed. Complete methanol conversion was achieved for the diluted feed. Maximum methanol conversions of 55% with 60% H2 yield were measured when the concentrated feed was selected. Promising results were also achieved for the Au-based structured catalysts in the CO-PrOx in an H2- rich atmosphere. Although CO conversions of approximately 60% were achieved, operating with higher catalyst loadings would be recommended to reach the high CO conversions required for PrOx catalysts.Fil: Adrover, María Esperanza. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Bahía Blanca. Planta Piloto de Ingeniería Química. Universidad Nacional del Sur. Planta Piloto de Ingeniería Química; ArgentinaFil: Boldrini, Diego Emmanuel. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Bahía Blanca. Planta Piloto de Ingeniería Química. Universidad Nacional del Sur. Planta Piloto de Ingeniería Química; ArgentinaFil: Jiménez Divins, Nuria. Universidad Politecnica de Catalunya; EspañaFil: Casanovas Hoste, Adria. Universidad Politecnica de Catalunya; EspañaFil: Tonetto, Gabriela Marta. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Bahía Blanca. Planta Piloto de Ingeniería Química. Universidad Nacional del Sur. Planta Piloto de Ingeniería Química; ArgentinaFil: Lopez, Eduardo. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Bahía Blanca. Planta Piloto de Ingeniería Química. Universidad Nacional del Sur. Planta Piloto de Ingeniería Química; ArgentinaFil: Llorca Piqué, Jordi. Universidad Politecnica de Catalunya; Españ

Preparing Phase 4 of the n_TOF/CERN facility

After CERN's Long Shutdown 2, the n_TOF facility infrastructure was largely upgraded. The biggest change is the installation of a new lead spallation target, the performance of which needs to be carefully examined. During Summer 2021, the facility's two flight paths were characterised in terms of neutron beam energy distribution, profile and resolution. In this work, the characterisation of the facility is described and the first results are given

Neutron capture cross section measurement of the heaviest s-process branching 204^{204}Tl and of 203^{203}Tl at CERN n_TOF

Neutron capture cross sections are fundamental in the study of the slow neutron capture process of nucleosynthesis, also known as the s-process, which produces half of the observed solar system abundances of elements heavier than iron. Some nuclei along the nucleosynthesis chain are unstable, and there the capture process competes with the decay process, creating a split in the nucleosynthesis path. The nuclear properties of some of these radionuclides change with the conditions of the stellar environment, a fact that influences the local abundance pattern. $^{204}$Tl is a very interesting branching point, because it is shielded from any contribution from other nucleosynthesis processes. The result is that both $^{204}$Tl and its stable daughter isotope $^{204}$Pb are only produced by the s-process. Hence, by competing with the beta decay, the capture cross section of $^{204}$Tl crucially determines the final abundance of $^{204}$Pb. A faithful prediction of the solar abundances of s-only isotopes, like $^{204}$Pb, is one of the key accuracy tests for modern stellar nucleosynthesis calculations. However, until the present work, due to the challenges of performing a capture measurement on $^{204}$Tl, there was no experimental data of its cross section. Thus, large uncertainties existed in its capture cross section, which hampered a more accurate and precise knowledge of the predicted s-process production of $^{204}$Pb. By affecting the abundance of $^{204}$Pb, the cross section of $^{204}$Tl(n,$\gamma$) also influences the ratio of abundances $^{205}$Pb/$^{204}$Pb. $^{205}$Pb is also produced only by the s-process, and it is radioactive, with a long half-life of 17.2 My. Therefore, the ratio of abundances of $^{205}$Pb/$^{204}$Pb has the potential to be used as a chronometer of the s-process. In the year 2013, a sample enriched up to a few percent in $^{204}$Tl was produced by neutron irradiation of a $^{203}$Tl seed sample at the high thermal neutron flux nuclear reactor of the ILL, in Grenoble (France). Two years later, the $^{204}$Tl enriched sample was employed to measure, for the first time, the capture cross section of $^{204}$Tl at the n TOF time-of-flight facility at CERN. The measurement was possible thanks to the unique features of this facility, in particular, its high instant neutron flux low background levels. The measurement was performed employing the well-established Pulse Height Weighting Technique (PHWT), which offers a very low neutron sensibility, and low levels of background, compared to other methods like the Total Absorption technique. The main challenges for the $^{204}$Tl measurement were the very high background due to the activity of the sample, the very low amount of material, and the limited knowledge of the geometry of the sample. Such difficulties required the adoption of specific solutions during the measurement and the posterior data analysis. Related to this, several sources of systematic error were evaluated by means of Monte Carlo simulations. The complications with the $^{204}$Tl sample geometry required to apply an in-sample normalization procedure. For this purpose, an ancillary capture measurement on a $^{203}$Tl sample was also performed in the same experimental campaign. As a stable nuclide, most of the sources of systematic error could be kept under control. This allowed for an accurate R-matrix analysis of the most relevant capture levels in the resolved resonance region of $^{203}$Tl, including the first ever measurement under 3 keV of neutron energy. As a result, the present work has contributed, as well, to improve the $^{203}$Tl stellar capture cross section in the 8 to 25 keV neutron energy range. With the improved $^{203}$Tl(n,$\gamma$) cross section, an R-matrix analysis of several $^{204}$Tl resonances was made possible. These results were employed to experimentally constrain the $^{204}$Tl stellar cross section at low energies, and setting additional limits to the stellar cross section predicted by nuclear data evaluations at s-process temperatures

New reaction rates for the destruction of 7Be during big bang nucleosynthesis measured at CERN/n_TOF and their implications on the cosmological lithium problem

New measurements of the 7Be(n,α)4He and 7Be(n,p)7Li reaction cross sections from thermal to keV neutron energies have been recently performed at CERN/n_TOF. Based on the new experimental results, astrophysical reaction rates have been derived for both reactions, including a proper evaluation of their uncertainties in the thermal energy range of interest for big bang nucleosynthesis studies. The new estimate of the 7Be destruction rate, based on these new results, yields a decrease of the predicted cosmological 7Li abundance insufficient to provide a viable solution to the cosmological lithium problem

Status and perspectives of the neutron time-of-flight facility n_TOF at CERN

Since the start of its operation in 2001, based on an idea of Prof. Carlo Rubbia [1], the neutron time of-flight facility of CERN, n_TOF, has become one of the most forefront neutron facilities in the world for wide-energy spectrum neutron cross section measurements. Thanks to the combination of excellent neutron energy resolution and high instantaneous neutron flux available in the two experimental areas, the second of which has been constructed in 2014, n_TOF is providing a wealth of new data on neutron-induced reactions of interest for nuclear astrophysics, advanced nuclear technologies and medical applications. The unique features of the facility will continue to be exploited in the future, to perform challenging new measurements addressing the still open issues and long-standing quests in the field of neutron physics. In this document the main characteristics of the n_TOF facility and their relevance for neutron studies in the different areas of research will be outlined, addressing the possible future contribution of n_TOF in the fields of nuclear astrophysics, nuclear technologies and medical applications. In addition, the future perspectives of the facility will be described including the upgrade of the spallation target, the setup of an imaging installation and the construction of a new irradiation area