The chemistry of low dosage clathrate hydrate inhibitors

Abstract

Clathrate hydrate formation remains a significant problem in the oil and gas industry, often resulting in pipeline blockage and field-site shutdown. To this end, a series of low dosage hydrate inhibitors are utilised in industry to circumvent potentially catastrophic effects. While a plethora of inhibitors are in application, to date there has been no conclusive determination of the mechanism of action of these important compounds. In order to drive the optimisation of inhibitor design, there remains a need to understand their complex behaviour and the role of key functional groups.

This thesis begins with a systematic study of the hydration behaviour of a series of commercially available poly(lactam) hydrate inhibitors. Solution IR spectroscopic titrations are reported for these polymers, providing insight into water binding at the polar amide carbonyl moiety. In an attempt to overcome the complexities associated with gaining quantitative insight into the behaviour of polymers, this thesis reports the development and analysis of model compounds. The model compounds are, in general, small dimeric analogues containing the key functionalities from the parent polymer appended on an aliphatic backbone. Finally, the solution and solid-state behaviours of these small model compounds are examined through a combination of analytical techniques.

Neutron scattering studies can provide unique insight into the structures of disordered systems. This thesis examines the liquid structures of aqueous THF, aqueous 2-butoxyethanol and aqueous lactam systems. By combining experimental neutron data with computational modelling it was possible to elucidate some insight into these systems of interest in solution as a function of temperature.

The final chapters report a series of lactam-metal coordination complexes, wherein the high polarity of the amide carbonyl moiety is exploited in the formation of interesting carbonyl-bound metal complexes. The X-ray single crystal structures are included for complexes containing sodium, potassium, zinc and calcium cation centres, with short carbonyl-metal bond distances observed in all instances. The versatility of ligand binding is encouraging, and may be of industrial importance.