Einsatz ligandenstabilisierter Nanopartikel in der heterogenen Katalyse

Colloidally-synthesized nanoparticles are advantageous (e.g. control of size/morphology) compared to traditional synthetic routes. Although such particles are already been widely used in liquid phase catalysis, applications in heterogeneous gas phase catalysis are still largely missing. Whereas in many studies organic stabilizers from the synthesis are considered to block catalytically active sites, their benefits on heterogeneous gas phase catalysis are discussed in this work. Identical Pt nanoparticles with a variety of different ligands are synthesized with the ethylene glycol method which allows for a direct investigation of the influence of the ligands. Ligand-capped nanoparticles are deposited on different oxidic supports and compared with their ligand-free counterparts in respect to hydrogenation reactions and CO oxidation. The fate of the ligand shell in different temperature ranges and beneficial effects of the ligands on catalytic properties are elucidated. Furthermore, the results obtained for powder catalysts can be easily transferred to monolithic structures with distinct advantages for industrial applications

Classical strong metal–support interactions between gold nanoparticles and titanium dioxide

Supported metal catalysts play a central role in the modern chemical industry but often exhibit poor on-stream stability. The strong metal–support interaction (SMSI) offers a route to control the structural properties of supported metals and, hence, their reactivity and stability. Conventional wisdom holds that supported Au cannot manifest a classical SMSI, which is characterized by reversible metal encapsulation by the support upon high-temperature redox treatments. We demonstrate a classical SMSI for Au/TiO2, evidenced by suppression of CO adsorption, electron transfer from TiO2 to Au nanoparticles, and gold encapsulation by a TiOx overlayer following high-temperature reduction (reversed by subsequent oxidation), akin to that observed for titania-supported platinum group metals. In the SMSI state, Au/TiO2 exhibits markedly improved stability toward CO oxidation. The SMSI extends to Au supported over other reducible oxides (Fe3O4 and CeO2) and other group IB metals (Cu and Ag) over titania. This discovery highlights the general nature of the classical SMSI and unlocks the development of thermochemically stable IB metal catalysts

Ringhals kärnkraftverk - Rening av ånggeneratorernas bottenblås Jämförelse mellan jonbytare och EDI : Jämförelse mellan jonbytare och EDI

Ringhals är ett kärnkraftverk beläget på Väröhalvön i Halland. Det finns totalt fyra stycken reaktorer i drift. Ringhals 1 är en kokvattenreaktor medan Ringhals 2-4 är tryckvattenreaktorer. Syftet med rapporten är att fastställa vilken reningsmetod av ånggeneratorernas bottenblås som är den mest fördelaktiga sett ur ett personal-, miljömässigt samt ekonomiskt perspektiv. Reningen av ånggeneratorernas bottenblåsningssystem skiljer sig åt på Ringhals 2-4. På Ringhals 2 renas vattnet på elektroniskt vis, medan man i Ringhals 3-4 renar vattnet med hjälp av jonbytarfilter. Varannan vecka blir massan mättad och behöver bytas ut. Processoperatörerna får då ett recept av kemiavdelningen hur blandningen ska vara. Vanligtvis är det 82 säckar, som vardera väger tjugo kilo, som ska fyllas i jonbytaren. Det har i många år förts debatt om fyllningen av jonbytarmassa. Arbetet medför tunga och obekväma lyft. Säckarna lyfts från marken och fylls i en tratt, belägen ungefär 1,5 meter över golvet vilket kan leda till arbetsskador. Skulle jonbytarmassa hamna på golvet medför detta en halkrisk. Förbrukad massa hamnar på deponi. Fördelarna med avjonisering på elektroniskt vis är störst ur personalmässig synvinkel. Jonbytarmassan, som fungerar som ett partikelfilter, behöver endast bytas ut en gång per år under revision på Ringhals 2. Ammoniaken som avskiljs från processvattnet leds ut till kylvattenkanalen, vilket medför utsläpp till havet på 800 kg per år. Underhåll och drift är mindre krävande med electronic deionization (EDI) jämfört med jonbytarfilter. Vidare undersökningar krävs för att fastställa om det är ekonomiskt och miljömässigt hållbart att installera EDI på de övriga blocken

Applications of colloidally synthesized nanoparticles in heterogeneous catalysis

Colloidally-synthesized nanoparticles are advantageous (e.g. control of size/morphology) compared to traditional synthetic routes. Although such particles are already been widely used in liquid phase catalysis, applications in heterogeneous gas phase catalysis are still largely missing. Whereas in many studies organic stabilizers from the synthesis are considered to block catalytically active sites, their benefits on heterogeneous gas phase catalysis are discussed in this work. Identical Pt nanoparticles with a variety of different ligands are synthesized with the ethylene glycol method which allows for a direct investigation of the influence of the ligands. Ligand-capped nanoparticles are deposited on different oxidic supports and compared with their ligand-free counterparts in respect to hydrogenation reactions and CO oxidation. The fate of the ligand shell in different temperature ranges and beneficial effects of the ligands on catalytic properties are elucidated. Furthermore, the results obtained for powder catalysts can be easily transferred to monolithic structures with distinct advantages for industrial applications

Molecular and Surface Catecholato Complexes of Titanium(IV)

Surface functionalized titanium dioxides (TiO2) are among the most studied hybrid materials for photocatalytic reactions and their potential application in the field of biomedicine, e.g. for light-induced targeted drug delivery, was pointed out. Catechols are prominent organic dyes, which generate different surface species on TiO2, dependent on the latter´s surface curvature and the surface loading. In order to investigate the surface species, which has previously been detected, only on very small nanoparticles, heteroleptic Ti(IV) catecholate complexes were synthesized, aiming at a monomeric Ti(IV) catecholate complex, whose basic actor ligands would readily react with the surface hydroxyls of the substrate, and whose catecholato binding mode (chelating) is predefined and retained upon the grafting reaction. In a first approach Ti(NMe2)4 was reacted with five differently substituted catechols, giving oxo-bridged dimers (except for [Ti(CATtBu-3,6)(NMe2)2]2, where one nitrogen atom was involved in the bridging, too). A ligand scrambling test with the largest and the smallest catecholate complexes indicated the presence of monomeric species in solution. Therefore, the sterically most demanding dimer [Ti(DHN)(NMe2)2]2 was further investigated according to two grafting routes – the sequential approach gave the same dominant surface species as the convergent approach, but in both cases more than one species was present at the surface. To prevent dimerization, the complexes with none and with the highest degree of catecholato- oxygen shielding by tert-butyl groups at the benzene ring – [Ti(CAT)(NMe2)2]2 and [Ti(CATtBu-3,6)(NMe2)2]2 – were reacted with neopentanol to exchange the small amido groups with bulkier actor ligands. In both cases HNMe2 stayed coordinated at the Ti(IV) centers to ensure an octahedral geometry. But only for the bulkier catecholato ligand a monomeric complex, [Ti(CATtBu-3,6)(OCH2tBu)2(HNMe2)2], was obtained. This was further used for the grafting onto KIT-6 for characterization of the surface species and onto m-TiO2 for optical and electronic investigations. Only the convergent approach gave exclusively the desired bidentate chelating surface species [Ti(CATtBu-3,6)(OCH2tBu)2(HNMe2)2]@[KIT-6], which was compared to an aqueous route species H2CATtBu-3,6@Ti(OH)x@[KIT-6] on the same support. The energy levels of the hybrid m-TiO2 from the aqueous route mirrored the well-known type-II excitation mechanism, which is accompanied by a slight increase of energy levels and a reduced bandgap, compared to virgin m-TiO2. The novel hybrid-m-TiO2 from the convergent approach displayed decreased energy levels compared to virgin m-TiO2, and an even smaller bandgap than the aqueous approach material