Interactions of lactam containing compounds based on kinetic hydrate inhibition polymers

Abstract

As the supply of natural gas becomes more scarce, it is becoming increasingly more attractive and financially viable to start using reserves that were previously determined to be to impure to use. H2S and CO2 are a couple of the major impurities found in natural gas. Natural gas high in these chemicals is referred to as sour gas. Presence of these impurities increases the chances of clathrate hydrate formation in pipelines, which can lead to pipe blockages or ruptures. To prevent clathrate hydrate formation, low dosage, polymeric, kinetic hydrate inhibitors (KHIs) are used. KHIs are water soluble polymers, most commonly polyvinylcaprolactam (PVCap) and polyvinylpyrrolidone (PVP). There is to date no definitive answer to the method of hydrate inhibition by KHIs and knowing how they work could lead to the design and manufacture of more effective inhibitors.
This thesis begins with the synthesis of model compounds. Low molecular weight compounds containing pyrrolidone and/or caprolactam rings were created to mimic PVP and PVCap. To look at the crystallisation behaviour of the model compounds, a wide range of different multicomponent crystallisations were attempted with pharmaceutical coformers, hydrogen bond donors, halogen bond donors and metal salts. Successfully formed cocrystals were analysed by single crystal x-ray crystallography. Cocrystals formed with boronic acids were tested for their ability to gel guar and compared with the commercially used boric acid.
The effect of sour gas on the interactions of the KHIs and model compounds with water was investigated using IR and NMR techniques. Small angle neutron diffraction was used to explore the synergistic effect between butoxyethanol and PVCap which leads to a significant improvement in hydrate inhibition.
Finally the ability of the model compounds to prevent crystallisation was applied to pharmaceuticals. Attempts to stabilise the amorphous forms of a range of drugs by creating coamorphous mixtures with the model compounds were investigated by hot-stage microscopy, DSC and PXRD.