Mosayyeb Arjmandi

Extension of Valderrama-Patel-Teja equation of state to modelling single and mixed electrolyte solutions

The Valderrama modi4cation of Patel–Teja equation of state (VPT EoS) has been extended to predicting 5uid phase equilibria in the presence of single and mixed electrolyte solutions at high-pressure conditions. Salts have been introduced as components in the EoS by calculating their EoS parameters from corresponding cation and anion parameters. A non-density dependent mixing rule is used for calculating a, b, and c parameters of the EoS. The inclusion of salts in the EoS resulted in the omission of the Debye–H9 electrostatic contribution term in the fugacity coe;cient calculations. Water–salt binary interaction parameters (BIPs) are optimised using freezing point depression and boiling point elevation data of aqueous electrolyte solutions. Gas solubility data in aqueous electrolyte solution are used for optimising salt–gas BIPs. The predictions of the model have been compared with independent experimental data, demonstrating the reliability of the approach. ? 2003 Elsevier Science Ltd. All rights reserved.

Formation of Methane Hydrate in the Presence of Natural and Synthetic Nanoparticles

Natural gas hydrates occur widely on the ocean-bed and in permafrost regions, and have potential as an untapped energy resource. Their formation and growth, however, poses major problems for the energy sector due to their tendency to block oil and gas pipelines, whereas their melting is viewed as a potential contributor to climate change. Although recent advances have been made in understanding bulk methane hydrate formation, the effect of impurity particles, which are always present under conditions relevant to industry and the environment, remains an open question. Here we present results from neutron scattering experiments and molecular dynamics simulations that show that the formation of methane hydrate is insensitive to the addition of a wide range of impurity particles. Our analysis shows that this is due to the different chemical natures of methane and water, with methane generally excluded from the volume surrounding the nanoparticles. This has important consequences for our understanding of the mechanism of hydrate nucleation and the design of new inhibitor molecules.