Environmentally, CO2 removal in form of CO2 hydrate in the ocean is one possibility of reducing the atmospheric concentrations of this greenhouse gas and assist in diminishing global warming. Considering the importance of CO2 hydrates, this paper focuses on molecular ynamics (MD) simulations of structure I CO2 hydrate. The goal is to study the stability of the clathrate at different temperatures. For achieving this purpose, energetic and structural properties are calculated. Equilibrium MD simulations are carried out to study the properties of fully occupied CO2 clathrate-hydrate at 260, 270, 280, and 290 K using CVFF force field. A mixture of water and CO2 placed in a cubic cell is used as a model system to simulate the CO2 clathrate hydrate at 5 MPa during total simulation time of 200 ps. The cell parameters, stablization energies as well as radial distribution functions are computed. The obtained results at different temperatures indicate the hydrate stablility at low temperatures up to 280 K. Moreover, stablization energy outcomes reveals that CO2 hydrate is more stable than the empty clathrate.
Gas hydrates (or clathrate hydrates) are ice-like crystalline molecular complexes composed of water and gas in which solid lattices of water molecules trap ‘guest’ gas molecules in a cage-like structure, or clathrate. They are formed when water and gas are combined at low temperature and generally high pressure (e.g. temperatures below 25◦C and pressures greater than 1.5 MPa for natural gas hydrates) . The water molecules in gas hydrates are linked to each other through hydrogen bonds to form a host lattice with polyhedral cavities that are large enough for small gas molecules such as methane, ethane, propane, carbon dioxide, and hydrogen sulphide to occupy . When gas hydrates dissociate, the crystalline lattice breaks down into liquid water and the gas is released. The common naturally occurring gas hydrates are known in three structural forms of structure I and structure II with cubic symmetry and structure H with hexagonal symmetry ; However, the current study is based only on structure I hydrates. Structure I hydrate has two types of cavity: a small pentagonal dodecahedral cavity consisting of 12 pentagonal rings of water (20 water molecules) and a large tetrakaidecahedral cavity consisting of 12 pentagonal and two hexagonal rings of water (24 water molecules) . Commonly cited structural details are given in Table 1.
Publisher : 2nd National Iranian Conference on Gas Hydrate (NICGH)
By : Mohammad Gharebeiglou, Zeinab Jamalzadeh, Hamid Erfan-Niya
File Information: English Language/ 10 Page / size: 1.40 KB
سال : 1392
ناشر : دومین کنفرانس ملی هیدرات گاز (NICGH)
کاری از : محمد قاربیگلو، زینب جمالزاده، حمید عرفان نیا
اطلاعات فایل : زبان انگلیسی / 10 صفحه / حجم : KB 1.40