In situ studies of oxygen transport mechanisms in Ag/SrFeO 3− δ materials for chemical looping catalysis

Strontium ferrite (SrFeO3−δ) impregnated with a noble metal (e.g. Ag) has been applied to catalyse selective oxidation reactions in a chemical looping mode, such as in ethylene epoxidation or ethanol dehydrogenation. The metal oxide donates oxygen to the reaction at the Ag catalyst, and then is re-oxidised in air in a separate step, however the mechanisms of oxygen transport are poorly understood. Here, we investigated the transport of oxygen within Ag/SrFeO3−δ materials in situ to determine the mechanisms by which Ag improves the redox activity of SrFeO3−δ. X-ray diffraction under 5 vol% H2 showed that the Ag nanoparticles decreased the temperature required for phase transformation from perovskite to brownmillerite structure, SrFeO2.5, from c. 500 °C for bare SrFeO3−δ to c. 300 °C for Ag/SrFeO3−δ. Near-ambient pressure X-ray photoelectron spectroscopy (NAP-XPS) and Raman spectroscopy showed that Ag–Ox surface intermediates enhance the release and uptake of oxygen, confirming that Ag takes an active role in the reduction of Ag/SrFeO3−δ

Evolution and Determinants of Rent Burdens in Germany

The affordability of housing has become a major topic of discussion in Germany among both social scientists and the public at large. Using data from the German Socio-Economic Panel (SOEP), we provide rent-income ratios over more than two decades and show how they change with households' disposable needs-adjusted income. We find a substantial increase in the ratios over the 1990s. In the decade that followed, they remained relatively constant. Moreover we find that rent-income ratios decrease in income at a decreasing rate, suggesting that rising square-meter prices put particular financial pressure on low-income households. Our analysis also indicates economies of scale from shared living space for multi-member households

Assessing progress in monitoring and implementing the EU biodiversity strategy for 2030

The aim of this science for policy report is twofold. First, it presents the state of play and the next steps in developing a monitoring framework for the EU Biodiversity Strategy for 2030 (EU BDS). Second, it provides an overview of progress made in implementing the EU BDS to date, as well as an assessment of the likelihood of reaching its targets by 2030. It mobilises various data sources – the official EU BDS and other policy-relevant progress monitoring tools, scientific literature and expert opinions – to provide a state of play of key achievements and remaining gaps in both monitoring and implementing the EU BDS as we approach its mid-term mark. Almost half of the actions are completed; the remaining half are mostly in progress, and a few are delayed. Indicators are published to track progress towards more than 40 % of the EU BDS targets and, with the notable exception of those on the state of biodiversity, the EU is showing progress in the right direction towards most of the evaluated targets; however, the pace of progress needs to accelerate massively to reach the 2030 targets. Further effort and engagement with the scientific community is needed to fill the remaining monitoring gaps, while a better implementation of the environmental policies would be necessary to meet the maximum of targets by 2030

How does the oxidation and reduction time affect the chemical looping epoxidation of ethylene?

AbstractThe chemical looping epoxidation (CLE) of ethylene was performed over an Ag catalyst supported on strontium ferrite perovskite (SrFeO3-δ). CLE consists of a reduction step in ethylene where oxygen is transferred from the support to the Ag catalyst to form ethylene oxide (EO), and a separate regeneration step, in which the support is reoxidised in air. The effect of altering the reduction and oxidation times was investigated, analysing changes in the conversion of ethylene and selectivity to EO. Experiments were conducted at 270 °C in a packed bed of Ag(15 wt.%)/SrFeO3-δ with a gas hourly space velocity of 9600 h−1 and a total operation time &gt; 40 h. When the time of the reduction step was increased from 1 to 3 min, selectivity to EO only decreased by 0.4%, demonstrating that CLE can run with prolonged reduction times while maintaining high selectivity. Increased duration of the reoxidation step resulted in both selectivity and conversion increasing, but when varying the oxidation time from 10 to 15 min, the overall improvement in the performance was minimal; thus, CLE can feasibly operate at shortened oxidation times. By increasing the pressure during the oxidation step to 2.5 bar, the duration of the reoxidation step was further shortened to 5 min without impacting the CLE performance. With 1.5 min reduction and 5 min reoxidation steps, a CLE installation producing EO in a pseudo-steady manner would require 4 packed bed reactors operating in parallel. The role of Ag2O in the CLE process was also investigated, demonstrating that the oxide was not selective towards EO.</jats:p