The Effect of Co Incorporation on the CO Oxidation Activity of LaFe1−xCoxO3 Perovskites

Perovskite oxides are versatile materials due to their wide variety of compositions of- fering promising catalytic properties, especially in oxidation reactions. In the presented study, LaFe1−xCoxO3 perovskites were synthesized by hydroxycarbonate precursor co-precipitation and thermal decomposition thereof. Precursor and calcined materials were studied by scanning electron microscopy (SEM), attenuated total reflection Fourier transform infrared spectroscopy (ATR-FTIR), thermogravimetric analysis (TG), and X-ray powder diffraction (XRD). The calcined catalysts were in addition studied by transmission electron microscopy (TEM) and N2 physisorption. The obtained perovskites were applied as catalysts in transient CO oxidation, and in operando studies of CO oxidation in diffuse reflectance infrared Fourier transform spectroscopy (DRIFTS). A pronounced increase in activity was already observed by incorporating 5% cobalt into the structure, which contin- ued, though not linearly, at higher loadings. This could be most likely due to the enhanced redox properties as inferred by H2-temperature programmed reduction (H2-TPR). Catalysts with higher Co contents showing higher activities suffered less from surface deactivation related to carbonate poisoning. Despite the similarity in the crystalline structures upon Co incorporation, we observed a different promotion or suppression of various carbonate-related bands, which could indicate different surface properties of the catalysts, subsequently resulting in the observed non-linear CO oxidation activity trend at higher Co contents

Dynamics of Reactive Oxygen Species on Cobalt-Containing Spinel Oxides in Cyclic CO Oxidation

Reactive oxygen species (ROS) are considered to be responsible for the high catalytic activity of transition metal oxides like Co3-xFexO4 in oxidation reactions, but the detailed influences of catalyst composition and morphology on the formation of these reactive oxygen species are not fully understood. In the presented study, Co3O4 spinels of different mesostructures, i.e., particle size, crystallinity, and specific surface area, are characterized by powder X-ray diffraction, scanning electron microscopy, and physisorption. The materials were tested in CO oxidation performed in consecutive runs and compared to a Co3-xFexO4 composition series with a similar mesostructure to study the effects of catalyst morphology and composition on ROS formation. In the first run, the CO conversion was observed to be dominated by the exposed surface area for the pure Co-spinels, while a negative effect of Fe content in the spinels was seen. In the following oxidation run, a U-shaped conversion curve was observed for materials with high surface area, which indicated the in situ formation of ROS on those materials that were responsible for the new activity at low temperature. This activation was not stable at the higher reaction temperature but was confirmed after temperature-programmed oxidation (TPO). However, no activation after the first run was observed for low-surface-area and highly crystalline materials, and the lowest surface-area material was not even activated after TPO. Among the catalyst series studied here, a correlation of small particle size and large surface area with the ability for ROS formation is presented, and the benefit of a nanoscaled catalyst is discussed. Despite the generally negative effect of Fe, the highest relative activation was observed at intermediate Fe contents suggesting that Fe may be involved in ROS formation

A perspective on heterogeneous catalysts for the selective oxidation of alcohols

Selective oxidation of higher alcohols using heterogeneous catalysts is an important reaction in the synthesis of fine chemicals with added value. Though the process for primary alcohol oxidation is industrially established, there is still a lack of fundamental understanding considering the complexity of the catalysts and their dynamics under reaction conditions, especially when higher alcohols and liquid-phase reaction media are involved. Additionally, new materials should be developed offering higher activity, selectivity, and stability. This can be achieved by unraveling the structure–performance correlations of these catalysts under reaction conditions. In this regard, researchers are encouraged to develop more advanced characterization techniques to address the complex interplay between the solid surface, the dissolved reactants, and the solvent. In this mini-review, we report some of the most important approaches taken in the field and give a perspective on how to tackle the complex challenges for different approaches in alcohol oxidation while providing insight into the remaining challenges

Einblicke in die Säure-Base-Eigenschaften von modifizierten mehrwandigen Kohlenstoffnanoröhren

Kohlenstoffnanoröhren (CNTs) werden aufgrund ihrer hohen spezifischen Oberfläche, ihrer einzigartigen geometrischen und elektronischen Struktur und der hohen chemischen Sta- bilität als vielversprechende Materialien zur Anwendung in der heterogenen Katalyse diskutiert. Struktur und intrinsische Eigenschaften ihrer Oberfläche können zudem durch Einbau von Defekten, insbesondere durch Funktionalisierung mit Heteroatomen, gesteuert werden. Durch verschiedenartige Funktionalisierungen lassen sich saure oder basische Zen- tren auf der Oberfläche generieren, wodurch CNTs als heterogene Säure-Base-Katalysatoren eingesetzt werden können, aber auch als Trägermaterial z.B. für katalytisch aktive Metalle, da durch gezielte Modifizierung der CNT-Oberfläche Metall-Träger-Wechselwirkungen bee- influsst werden können und damit veränderte katalytische Eigenschaften zu erwarten sind. Um Struktur-Aktivitäts-Korrelationen aufstellen zu können, bedarf es sowohl geeigneter Präparationen zum Erhalt möglichst homogen funktionalisierter Oberflächen als auch belastbarer Methoden zu deren Strukturaufklärung. Die komplexe, stark von den Syn- theseparametern abhängige Oberflächenchemie der CNTs, erfordert dazu die gleichzeitige Anwendung komplementärer Charakterisierungsmethoden. Ziel dieser Arbeit war der Einbau von S-, N- und P-haltigen funktionellen Gruppen auf mehrwandigen CNTs, um gezielt Oberflächen mit sauren und basischen Zentren zu generieren. Die Art, Menge und thermische Stabilität der funktionellen Gruppen wurde vorwiegend mittels TPD, XPS, Mikrokalorimetrie und Elementaranalyse aufgeklärt. Die Säure-Base-Eigenschaften der Oberflächen wurden komplementär sowohl mittels pH-Titration in wässriger Phase als auch durch die sauer- bzw. basisch katalysierte Umsetzung von 2-Propanol in der Gasphase als sensitive Sondenreaktion bestimmt. TPO gab Aufschluss über den Einfluss der Heteroatome auf die oxidative Beständigkeit der CNTs. Zunächst gelang die Seitenwandfunktionalisierung der CNTs mit Sulfonsäuregruppen mit Hilfe einer Diazotierung von Sulfanilsäure in o-Dichlorbenzol und Wasser. TPD- Experimente bestätigen eine thermische Stabilität der Gruppen bis 250 °C. Sowohl die pH-Titration als auch eine hohe Propylenselektivität in der Umsetzung von 2-Propanol beweisen die sauren Oberflächeneigenschaften. Eine Desaktivierung kann bei Durchführung der Reaktion unterhalb von 200 °C vermieden werden. Die Menge an sauren Zentren korreliert hierbei mit der Konzentration an S in den Proben und es konnte herausgestellt werden, dass das Lösungsmittel Wasser gegenüber o-Dichlorbenzol einen höheren S-Einbau begünstigt. Die Darstellung N-funktionalisierter CNTs gelang mittels Aminierung in 50% NH3/Ar- Atmosphäre von O-funktionalisierten CNTs bei verschiedenen Temperaturen. TPD- und XPS-Analysen ergaben die Anwesenheit von vorwiegend Imiden und Lactamen nach Behandlung bei 300 °C und pyrrolischen N nach Funktionalisierung bei 500 °C. Eine Aminierung bei 700 °C führt gezielt zu überwiegend pyridinischen N. Während der N- Gehalt mit zunehmender Behandlungstemperatur leicht sinkt, steigt die Basizität der Oberflächen drastisch an, was weniger durch die Menge als vielmehr durch die Art der funktionellen Gruppen bestimmt wird. Die bei 700 °C funktionalisierten CNTs erreichten nahezu Totalselektivität bezüglich Aceton in der Umsetzung von 2-Propanol. Innerhalb einer Periode von 12 h ist die Aktivität stabil, solange die Temperatur weniger als 250 °C beträgt. Die basischen CNTs wiesen eine mit dem Ausgangsmaterial vergleichbare oxidative Beständigkeit auf. Die Modifikation mit P wurde durch Aktivierung mit H3PO4 im Temperaturbereich zwischen 400 und 700 °C erreicht. P wird hierbei in Form von Phosphaten kovalent an die CNTs gebunden wie anhand der CO-Bildung bei Temperaturen jenseits von 750 °C während der TPD nachgewiesen werden konnte. Die Ergebnisse der pH-Titration und die annähernde Totalselektivität zu Propylen in der Umsetzung von 2-Propanol bewiesen die sauren Eigenschaften der Oberfläche. Die hydrolyseempfindlichen Spezies zeigen ein stabiles Verhalten während der Reaktion bis zu einer Temperatur von 200°C. Mikrokalorimetrische Untersuchungen zeigten die Anwesenheit von zwei homogeneverteilten und energetisch äquivalenten Sauren-Zentren. Im Gegensatz zur Funktionalisierung mit anderen Heteroatomen konnte die oxidative Stabilität signifikant verbessert werden. Zusammenfassend wurden in dieser Arbeit mehrwandige CNTs erfolgreich mit S-, N- und P-basierten Gruppen funktionalisiert, wobei systematisch der Einfluss verschiedener Syntheseparameter auf die resultierenden Säure-Base-Eigenschaften untersucht wurde. Die komplementäre Anwendung von spektroskopischen, titrimetrischen und kalorimetrischen Methoden sowie Reaktivitätsstudien erlaubten qualitative und quantitative Aussagen über die Natur und Eigenschaften der verschiedenen funktionellen Gruppen auf der CNT- Oberfläche. Dieser wissensbasierte Ansatz führte mit Erfolg zur Darstellung wohldefinierter, nachweislich vielversprechender Säure-Base-Katalysatoren.Carbon nanotubes (CNTs) are regarded as promising materials in the field of heterogeneous catalysis due to their high specific surface area, unique geometric and electronic structure as well as their chemical stability. In addition, the structure and intrinsic surface properties can be influenced by incorporation of defects and, certainly, via chemical modification with heteroatoms. Various functionalization techniques allow the generation of acid or basic sites, thus enabling the possibility of employing CNTs either as heterogeneous acid-base catalysts or as a support for catalytic active phases. Metal-support-interactions can be influenced through specific functionalization of the CNT surface, which in turn are expected to have an impact on the resulting catalytic properties. In order to establish structure-activity correlations, it is essential to find suitable preparation routines that lead to homogeneously functionalized surfaces, whose structure may be elucidated employing reliable techniques. In addition, the complex surface chemistry of CNTs, whose state strongly depends on the synthesis parameters, requires the application of complementary characterization techniques. The aim of this work was the incorporation of S-, N-, and P-containing functional groups onto multiwall CNTs in order to purposefully generate surfaces with acid and basic centers. The nature, amount, and thermal stability of the functional groups were determined with the aid of TPD, XPS, microcalorimetry, and elemental analysis. Surface acid-base properties were elucidated by complementary techniques, namely pH titrations in aqueous phase and the catalytic transformation of 2-propanol performed in the gas-phase. TPO experiments provided information on the influence of heteroatoms on the oxidative resistance of CNTs. First of all, a sidewall functionalization of CNTs with sulfonic acid groups was achieved through diazotization of sulfanilic acid in ODCB and water. TPD experiments confirm a thermal stability of the surface species up to 250 °C. Potentiometric pH titration results and a high propylene selectivity in the course of the transformation of 2-propanol confirm the acidic surface properties. A deactivation can be prevented by performing the reaction at temperatures below 200 °C. The amount of acid sites correlates with the S-content in the samples. In addition, the incorporation of sulfur could be enhanced when using water as a solvent instead of ODCB. The synthesis of N-doped CNTs was accomplished by amination of O-containing CNTs at different temperatures in a 50 % NH3/Ar atmosphere. TPD and XPS analyses showed that imides and lactams are predominantly present after treatment at 300 °C, while pyrrolic-N is preferentially formed upon functionalization at 500 °C. Amination at 700 °C mainly yields pyridinic-N species. Whereas the N-content slightly drops with rising treatment temperature, the surface basicity is drastically increased, which is determined by the nature rather than the amount of functional groups. The CNTs modified at 700 °C almost achieved total selectivity towards acetone in the transformation of 2-propanol. The activity is stable within a period of 12 h, at least for reaction temperatures below 250 °C. The basic CNTs exhibit an oxidative resistance comparable to that of the pristine material. The modification with P was carried out through chemical activation with H3PO4 in the temperature range between 400 and 700 °C. P in form of phosphate species is hereby covalently attached to the CNTs as evidenced by CO formation at temperatures beyond 750 °C during TPD experiments. Results derived from potentiometric pH titrations and the approximately total selectivity towards propylene in the transformation of 2- propanol confirm the acidic surface properties. The hydrolysis-sensitive species exhibit a stable behaviour during reaction to a temperature of around 200 °C. Microcalorimetric measurements further confirmed the presence of two homogeneously distributed and energetic equivalent acid sites. In contrast to the functionalization with other heteroatoms, it was possible to significantly enhance the oxidative stability. In summary, in this work multiwall CNTs were a successfully functionalized with S-, N-, and P-containing groups, whereby the influence of different synthesis parameters on the resulting acid-base properties was systematically investigated. The complementary employment of spectroscopic, titrimetric, and calorimetric methods as well as reactivity measurements allowed drawing conclusions on a qualitative and quantitative basis about the nature and properties of different functional groups present on the CNT surface. This knowledge based approach led to a successful synthesis of promising acid-base catalysts

Työhyvinvointi palvelutalon henkilöstön kokemana

Tämän opinnäytetyön tarkoitus oli selvittää palvelutalon hoitajien työhyvinvointia heidän kokemanaan. Tavoite oli tuottaa tietoa hoitajien työhyvinvoinnista. Opinnäytetyötä voidaan hyödyntää työhyvinvoinnin kehittämisessä kyseisessä työpaikassa. Tutkimusmenetelmänä käytettiin laadullista tutkimusta. Tutkimustieto kerättiin avoimella kyselylomakkeella, johon hoitajat vastasivat essee muodossa. Kyselylomakkeet saatekirjeineen vietiin paikan päälle. Kaikkiaan kyselylomakkeita jaettiin 11 kpl, josta saatiin takaisin 9 kpl. Vastausprosentti työpaikalla oli siis 81.8 %. Tutkimuksen tuloksista voidaan havaita, että hoitotyö kyseisen yksikön työntekijöiden kokemana on kuormittavaa työtä. Hyvä ja avoin työyhteisö tukee työhyvinvointia toimipaikassa. Haasteellisena koettiin työnmäärä ja ristiriitaiset kokemukset esimiestyöstä.The purpose of this thesis was to investigate service home nurses’ wellbeing at work from their perspective. The aim of this thesis was generate empirical information about the nurses’ well-being at work. The results of this thesis can be used when developing the nurses’ wellbeing in the workplace in question. The research method used in the thesis was qualitative. The data was collected with an open questionnaire in which the nurses submitted their answers in an essay form. The questionnaires with their covering letters were taken to the service home. A total of eleven questionnaires were distributed and nine were returned. Hence, the return percentage was 81, 8 %. Based on the results of the study, it could be seen that nursing in the unit in question was stressful work. A good and open work community supports wellbeing at work. According to the nurses, the challenges in their work were related to their workload and to their conflicting experiences of the work of their superiors

Monitoring Catalytic 2-Propanol Oxidation over Co3O4 Nanowires via In Situ Photoluminescence Spectroscopy

Spectroscopic methods enabling real-time monitoring of dynamic surface processes are a prerequisite for identifying how a catalyst triggers a chemical reaction. We present an in situ photoluminescence spectroscopy approach for probing the thermo-catalytic 2-propanol oxidation over mesostructured Co3O4 nanowires. Under oxidative conditions, a distinct blue emission at ~420 nm is detected that increases with temperature up to 280 °C, with an intermediate maximum at 150 °C. Catalytic data gained under comparable conditions show that this course of photoluminescence intensity precisely follows the conversion of 2-propanol and the production of acetone. The blue emission is assigned to the radiative recombination of unbound acetone molecules, the n - π* transition of which is selectively excited by a wavelength of 270 nm. These findings open a pathway for studying thermo-catalytic processes via in situ photoluminescence spectroscopy thereby gaining information about the performance of the catalyst and the formation of intermediate products

Highly loaded bimetallic iron-cobalt catalysts for hydrogen release from ammonia

Abstract Ammonia is a storage molecule for hydrogen, which can be released by catalytic decomposition. Inexpensive iron catalysts suffer from a low activity due to a too strong iron-nitrogen binding energy compared to more active metals such as ruthenium. Here, we show that this limitation can be overcome by combining iron with cobalt resulting in a Fe-Co bimetallic catalyst. Theoretical calculations confirm a lower metal-nitrogen binding energy for the bimetallic catalyst resulting in higher activity. Operando spectroscopy reveals that the role of cobalt in the bimetallic catalyst is to suppress the bulk-nitridation of iron and to stabilize this active state. Such catalysts are obtained from Mg(Fe,Co)2O4 spinel pre-catalysts with variable Fe:Co ratios by facile co-precipitation, calcination and reduction. The resulting Fe-Co/MgO catalysts, characterized by an extraordinary high metal loading reaching 74 wt.%, combine the advantages of a ruthenium-like electronic structure with a bulk catalyst-like microstructure typical for base metal catalysts

High-Temperature Stable Ni Nanoparticles for the Dry Reforming of Methane

Dry reforming of methane (DRM) has been studied for many years as an attractive option to produce synthesis gas. However, catalyst deactivation by coking over nonprecious-metal catalysts still remains unresolved. Here, we study the influence of structural and compositional properties of nickel catalysts on the catalytic performance and coking propensity in the DRM. A series of bulk catalysts with different Ni contents was synthesized by calcination of hydrotalcite-like precursors Ni_<i>x</i>Mg_{0.67–<i>x</i>}Al_0.33(OH)₂(CO₃)_0.17·<i>m</i>H₂O prepared by constant-pH coprecipitation. The obtained Ni/MgAl oxide catalysts contain Ni nanoparticles with diameters between 7 and 20 nm. High-resolution transmission electron microscopy (HR-TEM) revealed a nickel aluminate overgrowth on the Ni particles, which could be confirmed by Fourier transform infrared (FTIR) spectroscopy. In particular, catalysts with low Ni contents (5 mol %) exhibit predominantly oxidic surfaces dominated by Ni²⁺ and additionally some isolated Ni⁰ sites. These properties, which are determined by the overgrowth, effectively diminish the formation of coke during the DRM, while the activity is preserved. A large (TEM) and dynamic (microcalorimetry) metallic Ni surface at high Ni contents (50 mol %) causes significant coke formation during the DRM