Theoretical Investigations on the Electrochemical Fluorination Reaction in the Simons Process

Perfluorinated compounds are found in a wide array of technical applications associated with modern society. For instance, perfluorinated compounds are used as various surfactants, or as cooling agents in the production of electronics. The Simons process is applied in industry for the synthesis of such compounds. The experimental setup consists of a Ni anode, a cathode (often Ni or Fe) and anhydrous hydrogen fluoride (HF) as fluorine source and solvent, in which organic substrates are dissolved. A cell potential of around 4.5-6.0 V is applied, which drives the fluorination reaction. Despite the prevalence in industrial applications, the chemical mechanism of the Simons process has still not been fully understood. There is evidence that the electrochemistry only involves the oxidation of the Ni anode and subsequent binding of fluoride ions from the solvent, leading to a reactive nickel fluoride film (NixFy) forming at the anode. The film is of unknown structure and chemical composition, although it is believed to include highly oxidized Ni3+ or Ni4+ centers. In this thesis, the structure and formation of the NixFy film is considered. Using a model system involving Ni(111) surfaces and layers of explicit solvent molecules, results from DFT calculations indicate that a metallic Ni anode is easily oxidized at very low cell potentials. Furthermore, the work contains studies on the interface of a Ni(111) surface and a single HF molecule, in order to gain knowledge of the adsorption mechanism of the molecule in a non-electrochemical environment. A good starting point for models of NixFy films are the already known binary nickel fluorides. Particularly NiF3 is of interest because of its strongly oxidizing properties and proposed role in the Simons process. The series of magnetic 3d metal trifluorides from TiF3 to NiF3 is considered with hybrid DFT and DFT+U methods. NiF3 is characterized as an antiferromagnetic wide-bandgap (3.3 eV) semiconductor. Hence, the compound is expected to be less electrically insulating than the Mott-Hubbard insulator NiF2 (bandgap 5 eV). Anodes are typically passivized at cell potentials below ca. 3 V, due to the formation of an insulating NiF2 film. In this thesis, the anode is structurally modeled as different NiF2 surfaces. Using hybrid DFT calculations and thermodynamical considerations for the cell potential, the oxidation of surface Ni2+ to Ni3+ is calculated to proceed at potentials around 3.1 V, which is in good agreement with oxidation features in cyclic voltammetry experiments.Perfluorinierte Verbindungen kommen in vielen technischen Anwendungen vor, die mit unserer modernen Gesellschaft verbunden sind. Perfluorinierte Verbindungen werden zum Beispiel als Tenside verwendet, oder als Kühlmittel, die bei der Herstellung elektronischer Geräte notwendig sind. Der Simons-Prozess wird häufig in der Industrie benutzt, um solche Verbindungen zu synthetisieren. Die experimentelle Einrichtung besteht aus einer Ni-Anode, einer Kathode (typisch Ni oder Fe) und wasserfreiem Fluorwasserstoff (HF), der als Fluor-Quelle und Lösungsmittel dient, in das die organischen Reaktanten aufgelöst werden. Es wird eine Zellspannung von 4.5-6.0 V benutzt, um die Fluorierungsreaktion voranzutreiben. Trotz der Vielfalt an industriellen Anwendungen, ist der chemische Mechanismus des Simons-Prozesses nicht komplett aufgeklärt worden. Es ist bereits literaturbekannt, dass die elektrochemischen Schritte die Oxidation der Ni-Anode betreffen, mit folgendem Binden von Fluorid-Ionen aus dem Lösungsmittel, so dass ein reaktiver Nickel-Fluorid-Oberflächenfilm (NixFy) an der Anode gebildet wird. Die Struktur und chemische Zusammensetzung des Filmes sind immer noch unbekannt, obwohl hoch-oxidierte Ni3+- oder Ni4+-Stellen als mögliche Komponente des Filmes vorgeschlagen worden sind. Diese Dissertation behandelt die Struktur und Entstehungsmechanismen des NixFy-Films. Mittels eines Grenzflächenmodells bestehend aus Ni(111)-Oberflächen und Schichten explizierter Lösungsmittelmoleküle, wird durch DFT-Berechnungen indiziert, dass eine metallische Ni-Anode einfach oxidiert wird, auch bei sehr kleinen Zellspannungen. Auÿerdem wird das Gränzflächensystem einer Ni(111)-Oberfläche und eines einzelnen HF-Moleküls untersucht, um Einsichten zu erhalten, über den Adsorptionsmechanismus des Moleküls in einer nicht-elektrochemischen Umgebung. Ein guter Ansatzpunkt für NixFy-Modelle sind die schon bekannten binären Nickelfluoride. Besonders interessant ist NiF3, wegen seiner stark oxidierenden Eigenschaften und vorgeschlagenen Rolle im Simons-Prozess. Die Serie der magnetischen 3d-Übergangsmetalltrifluoride wird mit hybrid-DFT und DFT+U Methoden untersucht. NiF3 lässt sich als antiferromagnetischer Halbleiter mit einem breiten Bandabstand (3.3 eV) charakterisieren. Deswegen wird erwartet, dass NiF3 weniger elektrisch isolierend wirkt, im Vergleich zu dem Mott-Hubbard-Isolator NiF2 (Bandlücke 5 eV). Anoden werden typischerweise passiviert im Zellspannungsbereich bis zu etwa 3 V, wegen eines entstehenden isolierenden NiF2-Films. In dieser Dissertation wird die Anodenstruktur als verschiedene NiF2-Oberflächen dargestellt. Durch hybrid-DFT-Berechnungen und thermodynamische Modelle für die Zellspannung, wird berechnet, dass die Oxidation von Ni2+ an der Oberfläche zu Ni3+ bei der Zellspannung 3.1 V stattfindet, was gut mit Cyclovoltammetrieversuchen übereinstimmt

Cartilage oligomeric matrix protein deficiency promotes early onset and the chronic development of collagen-induced arthritis

ABSTRACT: INTRODUCTION: Cartilage oligomeric matrix protein (COMP) is a homopentameric protein in cartilage. The development of arthritis, like collagen-induced arthritis (CIA), involves cartilage as a target tissue. We have investigated the development of CIA in COMP-deficient mice. METHODS: COMP-deficient mice in the 129/Sv background were backcrossed for 10 generations against B10.Q mice, which are susceptible to chronic CIA. COMP-deficient and wild-type mice were tested for onset, incidence, and severity of arthritis in both the collagen and collagen antibody-induced arthritis models. Serum anti-collagen II and anti-COMP antibodies as well as serum COMP levels in arthritic and wild-type mice were measured by enzyme-linked immunosorbent assay. RESULTS: COMP-deficient mice showed a significant early onset and increase in the severity of CIA in the chronic phase, whereas collagen II-antibody titers were similar in COMP-deficient and wild-type controls. COMP antibodies were not found in wild-type mice. Finally, COMP-deficient and wild-type mice responded similarly to collagen antibody-induced arthritis, indicating no difference in how collagen II antibodies interact with COMP-deficient cartilage during the initial stages of arthritis. CONCLUSIONS: COMP deficiency enhances the early onset and development of chronic arthritis but does not affect collagen II autoimmunity. These findings accentuate the importance of COMP in cartilage stability

Combining theory and experiment to characterize the voltammetric behavior of nickel anodes in the Simons process

The Simons process, otherwise known as the electrochemical fluorination (ECF) method, is widely used in industry to electrolytically synthesize chemicals for various purposes. Even to this day, the exact mechanism of the ECF reaction remains unknown, but is believed to involve the formation of an anodic nickel fluoride film with highly oxidized nickel centers. In this study, experiments and density functional theory calculations are combined to characterize the initial anodic peak occurring at potentials typically required in an ECF cell. NiF2 is believed to form a passivating layer at low potentials. The calculations show that a potential of +3.1 V is required to oxidize surface Ni2+ centers to Ni3+. This is in good agreement with the measured anodic peak at +3.57 V

Exploring nine simultaneously occurring transients on April 12th 1950

Nine point sources appeared within half an hour on a region within $\sim$ 10 arcmin of a red-sensitive photographic plate taken in April 1950 as part of the historic Palomar Sky Survey. All nine sources are absent on both previous and later photographic images, and absent in modern surveys with CCD detectors which go several magnitudes deeper. We present deep CCD images with the 10.4-meter Gran Telescopio Canarias (GTC), reaching brightness $r \sim 26$ mag, that reveal possible optical counterparts, although these counterparts could equally well be just chance projections. The incidence of transients in the investigated photographic plate is far higher than expected from known detection rates of optical counterparts to e.g.\ flaring dwarf stars, Fast Radio Bursts (FRBs), Gamma Ray Bursts (GRBs) or microlensing events. One possible explanation is that the plates have been subjected to an unknown type of contamination producing mainly point sources with of varying intensities along with some mechanism of concentration within a radius of $\sim$ 10 arcmin on the plate. If contamination as an explanation can be fully excluded, another possibility is fast (t $<0.5$ s) solar reflections from objects near geosynchronous orbits. An alternative route to confirm the latter scenario is by looking for images from the First Palomar Sky Survey where multiple transients follow a line.Comment: 21 pages, 3 figures, 1 table. Published in Scientific Reports. Supplementary information can be found on the publishers webpage (open access

Some Key Jurisprudential Issues of the Twenty-First Century

The objective of this study was to estimate the dispersal rate in an organism assumed to be confined to tree stands with unbroken continuity. We used the lichen-forming ascomycete Cliostomum corrugatum, which is largely confined to old oak stands. Five populations, with pairwise distances ranging from 6.5 to 83 km, were sampled in Ostergotland, south-eastern Sweden. DNA sequence data from an intron in the small subunit nuclear ribosomal RNA gene was obtained from 85 samples. Nearly all molecular variance (99.6%) was found within populations and there were no signs of isolation-by-distance. The absolute number of immigrants per population per generation (estimated to 30 years), inferred by Bayesian MCMC, was found to be between 1 and 5. Altogether, evidence suggests abundant gene flow in the history of our sample. A simulation procedure demonstrated that we cannot know whether effective dispersal is ongoing or if it ceased at the time when oaks started to decrease dramatically around 400 years BP. However, a scenario where effective dispersal ceased already at the time when the postglacial reinvasion of oak had reached the region around 6000 years BP is unlikely. Vegetation history suggests that the habitat of C. corrugatum was patchily distributed in the landscape since the early Holocene. Combined with the high dispersal rate estimate, this suggests that the species has been successful at frequently crossing distances of at least several kilometres and possibly that it has primarily been limited by the availability of habitat rather than by dispersal.Original Publication:Hakan Lattman, Louise Lindblom, Jan-Eric Mattsson, Per Milberg, Morten Skage and Stefan Ekman, Estimating the dispersal capacity of the rare lichen Cliostomum corrugatum, 2009, BIOLOGICAL CONSERVATION, (142), 8, 1870-1878.http://dx.doi.org/10.1016/j.biocon.2009.03.026Copyright: Elsevier Science B.V., Amsterdam.http://www.elsevier.com

Spin- and charge-density oscillations in spin chains and quantum wires

We analyze the spin- and charge-density oscillations near impurities in spin chains and quantum wires. These so-called Friedel oscillations give detailed information about the impurity and also about the interactions in the system. The temperature dependence of these oscillations explicitly shows the renormalization of backscattering and conductivity, which we analyze for a number of different impurity models. We are also able to analyze screening effects in one dimension. The relation to the Kondo effect and experimental consequences are discussed.Comment: Final published version. 15 pages in revtex format including 22 epsf-embedded figures. The latest version in PDF format is available from http://fy.chalmers.se/~eggert/papers/density-osc.pd

Loadings of dissolved organic matter and nutrients from the Neva River into the Gulf of Finland - Biogeochemical composition and spatial distribution within the salinity gradient

We studied the loadings of dissolved organic matter (DOM) and nutrients from the Neva River into the Eastern Gulf of Finland, as well as their distribution within the salinity gradient. Concentrations of dissolved organic carbon (DOC) ranged from 390 to 840 mu M, and were related to absorption of colored DOM (CDOM) at 350 nm, a(CDOM)(350), ranging from 2.70 to 17.8 m(-1). With increasing salinity both DOC and a(CDOM) decreased, whereas the slope of a(CDOM) spectra, S-CDOM(300-700), ranging from 14.3 to 21.2 mu m(-1), increased with salinity. Deviations of these properties from conservative mixing models were occasionally observed within the salinity range of approximately 1-4, corresponding to the region between 27 and 29 degrees E. These patterns are suggested to mostly reflect seasonal changes in properties of river end-member and hydrodynamics of the estuary, rather than non-conservative processes. On the other hand, observed nonlinear relationships observed between a(CDOM)*(350) and S-CDOM(275-295) emphasized the importance of photochemistry among various transformation processes of DOM. Dissolved inorganic nitrogen was effectively transformed in the estuary into particulate organic nitrogen (PON) and dissolved organic nitrogen (DON), of which DON was mostly exported from the estuary, enhancing productivity in nitrogen limited parts of the Gulf of Finland. DON concentrations ranged from 12.4 to 23.5 mu M and its estuarine dynamics were clearly uncoupled from DOC. In contrast to DOC, estuarine DON dynamics suggest that its production exceeds losses in the estuary. Total nitrogen (TN) and phosphorus (TP) loadings from the Neva River and St. Petersburg were estimated as 73.5 Gg N yr(-1) and 4.2 Gg P yr(-1), respectively. Approximately 59% of TN and 53% of TP loads were in organic forms. DOC and DON loadings were estimated as 741.4 Gg C yr(-1) and 19.0 Gg N yr(-1), respectively. Our estimate for DOC loading was evaluated against a previously published carbon budget of the Baltic Sea. According to the updated model, the Baltic Sea could be identified as a weak source of carbon into the atmosphere. (C) 2016 The Authors. Published by Elsevier B.V.Peer reviewe