Raman Studies of Molecular Potential Energy Surface Changes in Supercritical Fluids

A unified equation for calculating methane vapor pressures in the CH4–H2O system with measured Raman shifts

“…As shown in Fig. 7b, our results are in excellent agreement with the experimental data as well as theoretical predictions of Ben-Amotz et al (1992). Their predictions were based on a model which approximates the structure of a supercritical fluid using a hard sphere reference fluid, attractive forces effects using a van der Waals mean field model, and the vibration of a polyatomic molecule using a corresponding pseudo-diatomic molecule.…”

“…The dashed curve is the same one shown in Fig. 7b from the theoretical study of Ben-Amotz et al (1992). Solid curves are visual fits of the data.…”

“…However, it should be pointed out that this near linear D-q relation is only true for the system where the density of methane is less than 0.3 g/cm 3 where van der Waals-type attractive forces dominate. At higher densities, repulsive forces become more important, as shown by the deviation of the measured and predicted values of Ben-Amotz et al (1992) from the linear D-q relation (Fig. 7b) and the observed change in slope of the D-q relationship at higher pressures (Fabre and Couty, 1986).…”

“…(b) Raman shifts of CH 4 (t 1 ) in the vapor phase of CH 4 -H 2 O system as a function of density of methane. The data plotted are those listed in Tables 1a and 5, and the experimental and theoretical values ofBen-Amotz et al (1992) were from theirFig. 4for pure CH 4 system.…”

Online Monitoring of Heterogeneous Polymerizations in Supercritical Carbon Dioxide by Raman Spectroscopy

“…[4][5][6] However, due to the high pressure related to the use of CO 2 under supercritical conditions, picking representative samples out the reactor is not simple, so that monitoring the reaction or polymerization kinetics is extremely difficult, laborious and time consuming. [15,16] For instance, Ben-amotz et al used a specifically designed cell for collecting the scattered light at 1808 of the incident laser beam whereas other groups directly introduced optical fibres in the cell for laser irradiation and collection of the scattered light 17 . Spectroscopic methods such as UV, infrared and Raman spectroscopy are ideal analytical tools for answering this demand.…”