Is gas hydrate formation thermodynamically promoted by hydrotrope molecules?

The effect of para-toluene sulfonic acid (p-TSA), an amphiphilic compound, on the phase equilibria of gas hydrates was studied experimentally. The equilibrium conditions (H–Lw–V) of three different gas hydrate systems were measured at different p-TSA concentrations in order to determine the effect of hydrotropes on the hydrate thermodynamics. It was previously reported that the hydrate dissociation temperature is shifted towards higher values with the addition of p-TSA. However, in this present study, no effect was observed on the hydrate phase equilibria with hydrotrope concentrations in the range of 2000–5000 ppm. Furthermore, at higher concentrations (up to 138 000 ppm), an inhibitor effect on CH4 hydrates was measured by a decrease in the hydrate stability zone (as an analogy to colligative properties of solutions). The accuracy of the hydrate equilibrium points, using the temperature cycling procedure, was found to be highly dependent on the heating rate during hydrate dissociation, and the reason for the discrepancy in the literature.