Boronic and Organic Acids as Synergists for a Poly(N-vinylcaprolactam) Kinetic Hydrate Inhibitor

A range of boronic acids have been investigated as synergists for the kinetic hydrate inhibitor (KHI) polymer, poly(N-vinylcaprolactam) (PVCap, Mw ≈ 10,000 g/mol) using high pressure rocking cells, a natural gas mixture, and a slow constant cooling (1 °C/h) test method from 76 bar. Surprisingly, unlike other classes of synergists such as alcohols and quaternary ammonium salts, the boronic acids that gave the best synergy had an alkyl or cycloalkyl tail with a maximum of a 3 carbon atom distance from the boron atom. The tail-branched iso-butylboronic acid was the best of these, yet it showed a negligible KHI effect when tested alone. However, consistent with the other classes of synergists, tail branching or use of a cyclic alkyl group was beneficial. Interestingly, boronic acids with chains of 5 to 6 carbon atoms, i.e., n-pentyl- and n-hexylboronic acids, were antagonistic to the PVCap KHI performance. For comparison, several organic acids were also investigated as synergists with PVCap. The same trend as for the boronic acids regarding the size and branching of the acid was seen. 3-Methylbutanoic acid gave the best synergy although worse than that of iso-butylboronic acid. The synergistic performance of sodium salts of some organic acids differed markedly to that of the free organic acids. Sodium 3,3-dimethylbutanoate gave the best synergy with PVCap.publishedVersio

Investigation of Lactam- Based Kinetic Hydrate Inhibitors and the Synergetic Effect of Solvents

Gas hydrate formation in flow lines is of notorious concern for the oil and gas industry, and it only gets bigger because of the never-ending pursuit of oil and gas compels the industry into deeper and colder waters. Gas hydrate can form and agglomerate into plugs, jeopardizing hydrocarbon production. Therefore, a variety of methods have been developed to inhibit gas hydrate formation. One of these is to utilize chemicals in the form of low dosage hydrate inhibitors (LDHI), which consists of two categories, kinetic hydrate inhibitors (KHI) and anti-agglomerants (AA). KHIs, the focus of this thesis, are mixtures of one or more water-soluble polymers in solvents and synergists. In order to find KHI chemicals with better inhibiting capabilities and/or environmental properties, the mechanism as to how KHIs operate must be better understood. The understanding of gas hydrate formation and the effect of different KHIs has been enriched by a large number of experimental studies using a plethora of research techniques, gaining insight into the gas hydrate nucleation and growth processes, coupled with the possible modes of action of KHIs. Investigations were carried out on both the macroscopic and microscopic scale. Despite all these endeavours, no clear consensus on the inhibition mechanism exists in the hydrate community, which limits the ability to design improved KHIs. Therefore, investigating new KHI polymers and synergists can help understand the structure-activity relationship and factors involved in the KHI mechanism. This PhD study consists of two main agendas, 1) investigating different compounds for their potential capabilities as synergist with probably the most well-known industrial KHI polymer, poly(N-vinyl caprolactam) (PVCap) and 2) investigating novel alternatives for PVCap as KHIs which also contain pendant caprolactam rings. Several excellent new synergists were discovered and a new class of acrylamido-based caprolactam polymers were synthesized and developed to give good KHI performance. In addition, the stability of PVCap and related KHI polymers was studied at a wide range of conditions including temperature and pH. This is relevant for field applications at extreme conditions. In another study, literature and experimental studies were used to determine if there is a correlation between polymer cloud point and KHI inhibition performance. The results showed that a low cloud point, near the hydrate formation temperature, was useful for high KHI performance of a polymer but only if certain criteria are met. These include low molecular weight, pendant hydrophobic groups of an optimal size close to the polymer backbone and the correct neighbouring hydrophilic functional groups. Finally, a new class of non-amide-based polymers, polyvinylaminals, were investigated as KHIs. For testing the inhibition capabilities, for both the synergist mixtures and the novel polymers, high-pressure rocking cells with synthetic natural gas mixture with either slow constant cooling or isothermal test regime were mainly used. These studies have resulted in nine journal publications

Ubiquitous preferential water adsorption to electrodes in water/1-propanol mixtures detected by electrochemical impedance spectroscopy

The electric double layer is an important structure that appears at charged liquid interfaces, and it determines the performance of various electrochemical devices such as supercapacitors and electrokinetic energy converters. Here the double-layer capacitance of the interface between aluminum electrodes and water/1-propanol electrolyte solutions is investigated using electrochemical impedance spectroscopy. The double-layer capacitances of mixture solvents are almost the same as those of water-only electrolyte solutions, and the double-layer capacitance of 1-propanol-only solutions are significantly smaller than those of other volume fractions of water. The qualitative variation of the double-layer capacitances with the water volume fraction is independent of the electrolyte types and their concentrations. Therefore, these results can be explained by ubiquitous preferential water adsorption caused by the hydrophilicity of the electrode surface.Comment: 7 pages, 5 figure

Novel Benzindoloazecines and Dibenzazecines: synthesis and affinities for the Dopamine receptors

Azecine sind eine neuartige Klasse von Dopaminrezeptor-Antagonisten, gekennzeichnet durch ihre nanomolare Affinitäten an den Dopaminrezeptoren und vor allem ihre Selektivität für die Rezeptoren der D1-Familie. Strukturwirkungsbeziehungen dieser Verbinungsklasse wurde umfassend erforscht. Die Strategie der vorliegenden Arbeit war die Strukturen der Leitverbindungen LE300 und LE404 so zu modifizieren, dass die erforderlichen strukturellen Merkmale weitgehend erhalten werden sollten. Das Benzindoloazecin LE300 wurde vielfältig modifiziert; z.B. durch Veränderung des Annellierungsmusters vom Ringgerüst oder Einfügen eines Substituents an verschiedenen Stellen. Außerdem wurde die phenolische Gruppe der Leitstruktur LE404 vom Dibenzazecin-Typ durch eine Methylendioxygruppe ersetzt. Das Ziel dieser Arbeit war die Strukturwirkungsbeziehungen dieser neuartigen Klasse von Dopaminrezeptor-Antagonisten weiter zu entwickeln, um Derivate mit höheren Affinitäten und besser ausgeprägten Subtypselektivität zu erreichen. Insgesamt wurden 29 Zielverbindungen synthetisiert und die Affinitäten an den verschiedenen Dopaminrezeptoren (human) durch Radioligandbindungsstudien ermittelt. Weiterhin wurde die Funktionalität der Verbindungen (Agonisten oder Antagonisten) mit Hilfe eines Calcium Assays bestimmt

Piacentinu Ennese PDO cheese as reservoir of promising probiotic bacteria

Piacentinu Ennese is a protected designation of origin (PDO) cheese produced in the surrounding area of Enna (Sicily, Italy), using raw ewe’s milk without the addition of any starter cultures. In the present study, the Lactobacillus population of Piacentinu Ennese PDO cheese was in vitro screened in order to select promising probiotic strains to be further used in humans. One hundred and sixty-nine lactic acid bacteria (LAB) were isolated from 90 days ripened cheeses and identified by Rep-PCR genomic fingerprinting, using the (GTG)5-primer, and by MALDI-TOF MS. One hundred and thirteen (113) isolates belonging to QPS-list species were characterized for both safety and functional properties. All tested isolates were considered safe because none showed either gelatinase, DNase, mucinase, or hemolytic activity. Tolerance to lysozyme, bile salts, and acidic conditions, along with ability to survive under simulated gastrointestinal digestion, were observed. In addition, based on antimicrobial activity against pathogens, cell surface characteristics, Caco-2 adhesion abilities, and anti-inflammatory potential, it was possible to confirm the strain-dependent functional aptitude, suggesting that Piacentinu Ennese PDO cheese may be considered a precious source of probiotic candidates

Further Investigation of Solvent Synergists for Improved Performance of Poly(N-vinylcaprolactam)-Based Kinetic Hydrate Inhibitors

Poly(N-vinylcaprolactam) (PVCap) and related copolymers have been used as kinetic hydrate inhibitors (KHIs) to combat gas hydrate formation in oil and gas field production flow lines. It is known that the addition of certain solvents to the KHI polymer can enhance its ability to hinder gas hydrate formation. In an earlier study, a wide range of alcohols, glycol ethers, and ketones were investigated as synergetic solvents with PVCap. In that study, an outstanding synergetic effect was achieved by 4-methyl-1-pentanol (iHexOl). This report builds on that study by investigating iHexOl in more detail as well as some newly synthesized solvents predicted by the first study to have good synergism. Both slow constant cooling (SCC) and isothermal KHI experiments were conducted in high-pressure steel rocking cells using a structure II-forming natural gas mixture. The KHI polymer concentration, solvent concentration, and mixed solvent systems were investigated. The solvent synergist water solubility, also in brines, and partitioning to the liquid hydrocarbon phase are shown to be important factors to consider for optimizing KHI performance. Further, it was observed that the optimal molecular weight distribution for the KHI polymer when used with a solvent synergist is not the same as the optimum distribution when using the polymer alone.publishedVersio

I. Stereochemical Control of Chiral Assembly and Liquid Crystal Phase Formation of Nonamphiphilic Molecules in Water II. Control Bacterial Quorum Sensing and Quorum Sensing-mediated Activities Using Small Unnatural Molecules

The primary goal of this research is to utilize organic synthesis as a tool to prepare small molecules that find potential application in different areas including colloidal and material science, biological chemistry, and medicinal chemistry. Chapter 1 describes the interpretation of the conformation of nonamphiphilic mesogen disodium cromoglycate (5´DSCG) when it exists as part of an assembly in water. The study of thermodynamic incompatibility and miscibility suggest that a previously proposed model for the assembly of 5´DSCG may be applicable to nonamphiphilic organic dyes and other mesogens. Chapter 2 presents a study of stereochemical control on assembly and liquid crystal formation by nonamphiphilic molecules. Three stereoisomers of a disodium chromonyl carboxylate derivative, 5´DSCG-diviol, were designed and synthesized. The chiral stereoisomers formed chiral nematic liquid crystals while the achiral counterpart did not form any kind of liquid crystals. The hydrated assemblies of chiral 5´DSCG-diviol were able to interact with each other across a 6 nm separation in aqueous environment and the chirality information was transmitted through achiral medium. Chapter 3 describes the synthesis and biological studies of a class of bicyclic brominated furanones. These molecules interacted with quorum sensing in an opportunistic pathogen P. aeruginosa. Some representative compounds in this class inhibited quorum sensing-controlled activities such as biofilm formation and virulence factor production, which were key factors in the pathogenicity of the bacteria. These compounds exhibited significant reduction in the toxicity of human neuroblastoma SK-N-SH and did not inhibit bacterial growth. Furthermore, one compound, 6-BBF, significantly improved P. aeruginosa clearance in the lungs of mice in an immunocompromised pneumonia mouse model in vivo. Chapter 4 reports the synthesis of a library of squarylated homoserine lactones (SHLs) as analogues to the natural autoinducers N-acyl homoserine lactones (AHL) in Gram-negative bacteria. These SHLs were shown to have no or minimal impact of the growth of P. aeruginosa and V. fischeri, but maintain the abilities to modulate quorum sensing and inhibit biofilm formation. Primary studies of structural activity relationship revealed that the alkyl chain length was critical to activities of SHLs. These SHLs are promising candidates as modulators of other AHL-mediated QS systems