Hydration Behavior of Polylactam Clathrate Hydrate Inhibitors and Their Small-Molecule Model Compounds

Abstract

The solution hydration behavior of a series of lactam-based kinetic clathrate hydrate inhibitors (KHIs) has been studied in order to determine mechanistic insight into their KHI performance.IR and 1 H NMR spectroscopic titration data were compared across a series of mono-and bis(lactam) model compounds, and solid-phase hydration behavior was examined by Dynamic Vapour Sorption. The structures of several of the model compounds have been investigated by X-ray crystallography. The work reveals insight into the very low crystallinity and high hygroscopicity of these materials which is linked to their performance as KHIs. Analysis of water binding in sour gas systems, containing H 2 S and CO 2 , reveals no effect on the water affinity of the lactams suggesting that sour gas components do not inhibit KHI performance, but rather promote clathrate hydrate formation.

Halogen and Hydrogen Bonding in Povidone-Iodine and Related Co-Phases

“…In particular the IR spectra of 1 the weakening of the C=O bond, a phenomenon observed previously. 3 In commercial povidoneiodine, however this band is strong and present at 1653 cm -1 , slightly lower that its position in free PVP K12 (1668 cm -1 ; 24 The Fikentscher K-value 6 is derived from the viscosity of a 1wt% solution of the polymer and K12 corresponds to a molecular weight of 4,000 -6,000 25 ).…”

“…Interestingly, in a dry acetonitrile solution of PVP K12, this band occurs at significantly higher wavenumber, 1682 cm -1 . 24 The reduction in stretching frequency in the solid state is attributed to CH•••O hydrogen bonding interactions. In PVP-iodine the presence of this band indicates the presence of a substantial number of free (non-protonated) carbonyl groups, consistent with the relatively low loading of iodine in the commercial product, which is typically produced from significantly less than 0.1 moles of iodine per pyrrolidone monomer unit.…”

Boric acid co-crystals in guar gelation

“…This shift is similar to those seen upon hydration and metal complexation of 1 and is indicative of a shift to the enolate resonance form and hence strong hydrogen bonding interactions. 33,34 The co-crystal was also prepared mechanochemically. 35 Solvent-free grinding of 1 and boric acid, in a 1:2 ratio using a pestle and mortar, results in the immediate formation of a white paste that transforms to a white crystalline solid upon air drying over a period of 3 hours at room temperature.…”

“…While the supramolecular chemistry of compound 1 is dominated by its strong hydrogen bond acceptor ability, -caprolactam is both a good hydrogen bond acceptor and donor with the seven-membered ring imparting a higher degree of polarity to the carbonyl group than the fivemembered ring analogue. 33 Grinding a 1:1 mixture of -caprolactam (2) and boric acid in a ball mill gave a homogeneous powder of a 1:1 co-crystal 2·B(OH)3. The cocrystal was identified by the characteristic hydrogen bonding induced shift in the carbonyl band in the solid state FTIR spectrum of the product (from 1653 to 1623 cm -1 ) and by its unique XRPD pattern.…”

Structures of a Clathrate Hydrate Former, Inhibitor, and Synergist in Water

“…[16][17] THF hydrate forms a structure II type clathrate and is synthesized from a 1:17 molar ratio of THF:water at temperatures below 4 o C. 18 In practice PVCap is often used as a 50% solution in 2-butoxyethanol. 11,19 In addition to being a solvent, there is evidence that 2-butoxyethanol assists with the operation of the KHI and hence it is described as a 'synergist'. 20 N-alkoxyethanols (ROCH2CH2OH) have been species of considerable interest, due in part to the formation of molecular aggregates within aqueous solution.…”