Thermodynamic and Modeling Study of Selected Aqueous Chemical Systems from 370 to 450 Degrees Celcius

摘要

Determination of thermodynamic quantities (K, DELTA H deg, DELTA S deg, and DELTA C sub p deg) for chemical reactions in the supercritical water region has special requirements. During the grant period, progress has been made in meeting these requirements in several areas. First, a new calorimeter has been constructed that overcomes significant experimental challenges in this temperature region. In this calorimeter, the reaction vessel and associated tubing are immersed in a eutectic-salt bath. This feature and the use of a thermoelectric cooler make it possible to minimize baseline corrections. Second, a novel model based on Helmholtz energy and capable of accounting for ion dissociation has been formulated. This model has been tested on experimental heat of reaction and heat of dilution data and has been shown to be superior to the Anderko-Pitzer equation in accounting for the measured heats in this temperature region. Third, heats of dilution, heats of mixing, and heats of reaction were determined for selected chemical systems and used to verify the achievement of the first and second items. The progress made during the grant period provides information that will be valuable for the design of processes needed for operation under supercritical water conditions.