Over the years, a lot of work has been devoted to the design and testing of molecular additives capable of preventing the build-up and agglomeration of natural gas hydrates (NGHs) in subsea pipelines, which are the main cause of pipeline blockage. Quaternary ammonium salts (QASs), for example, have been found to bind to NGH surfaces and change their chemistry and morphology, preventing agglomeration. And although originally developed to prevent hydrate formation/growth, studies have shown that some additives can promote growth instead, posing a serious limitation to the effective design of these molecules. On top of that, additive research commonly requires simulations of systems of thousands of molecules for long periods of time, making classical molecular dynamics the tool of choice, even considering the limitations imposed by the use of empirical force fields to the accurate modeling of hydrate-additive interactions. As these limitations highlight the need for a new computational framework for the successful modeling of NGHs-additive interactions, we aim to develop a multiscale/multimodel approach, where we take advantage of a continuum embedding scheme to overcome the cubic-scaling computational bottleneck associated with DFT modeling of larger systems, allowing for a first-principles description of the important components of hydrate-additive systems. With a realistic system, reconstructed from classical molecular dynamics simulations of larger hydrate systems,  one can investigate the adsorption of QAS of different alkyl chain lengths and functionalization on representative hydrate surfaces and to then analyze and compare compounds in terms of properties such as their binding affinities to determine their promotion/inhibition performances.

A first-principles high-throughput approach towards gashydrates inhibition and promotion

ACS Fall 2021

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