Tris(tert-heptyl)-N-alkyl-1-ammonium bromides-Powerful THF hydrate crystal growth inhibitors and their synergism with poly-vinylcaprolactam kinetic gas hydrate inhibitor

Quaternary ammonium salts containing the t-heptyl group have been synthesized for the first time. The new compounds are water-soluble tris(t-heptyl)(n-propyl)ammonium bromide and sparingly water-soluble tris(t-heptyl)(n-pentyl)ammonium bromide (tris(t-heptyl)PeAB). Both compounds were found to be powerful inhibitors of Structure II tetrahydrofuran hydrate crystal growth, with the performance of (tris(t-heptyl)PeAB) being as good as or better than that of either tetra(iso-alkyl)- or tetra(n-alkyl)ammonium bromides. Both t-heptyl salts were also excellent synergists in blends with poly(N-vinylcaprolactam) for kinetic hydrate inhibition of a Structure II-forming natural gas mixture using decane and 1.5 wt% aqueous NaCl at 80% water cut. This is all the more surprising for tris(t-heptyl)PeAB as this compound is sparingly water-soluble and thus partitions mostly to the liquid hydrocarbon phase.