in Wiley InterScience (www.interscience.wiley.com).Binary H 2 -THF clathrate hydrate formation kinetics were investigated with a pressure decay method at temperatures from 266.7 to 275.1 K, at initial pressures from 3.6 to 8.4 MPa, and at stoichiometric THF hydrate concentrations for particle sizes between 212 and 1,400 lm. Formation rate increased for smaller particle sizes, higher pressures and lower-temperatures. A hydrogen delocalization model and a proposed hydrogen hydrate phase diffusion (HHPD) model were used to analyze the formation mechanisms. The HHPD model assumes that the H 2 -THF hydrate phase is formed due to hydrogen adsorption onto the particle surface that is followed by subsequent diffusion of hydrogen into the clathrate hydrate. The HHPD model could express the kinetics quantitatively at the experimental conditions studied. Values of the hydrogen diffusion coefficient in the clathrate hydrate estimated from the bulk data and the phase thickness in the HHPD model agreed well with the literature.

Degradation of polyvinylchloride (PVC) in high-temperature and supercritical water was studied with a hydrothermal diamond anvil cell to determine phase change characteristics of the reacting polymer with respect to water density. During the reaction period of 500 s, at temperatures between 400 and 5008C and at water densities from 0 to 930 kg/m 3 , PVC particles exhibited clearly defined spreading on the anvil surface that was defined as spread time, S t . The spread times decreased with increasing temperature and the values increased with increasing water density. Analysis of the residues with infrared spectroscopy showed the presence of both polyenes and polyols, whose formation was correlated with water density.From the analyses, nucleophilic substitution of PVC in water was found to be promoted at low temperatures ($ 4008C) and high water densities (>830 kg/m 3 ), whereas the ionic chain dechlorination was promoted at high temperatures (> $ 4508C) and low water densities ($ 750 kg/ m 3 ). A reaction pathway is proposed that shows À ÀOH nucleophilic substitution in competition with ionic chain reaction for dechlorination both of which vary with water density.