بررسي نفوذ و جذب گازهاي كربن دي اكسيد ،كربن دي سولفيد، متان، اكسيژن و نيتروژن در زئوليت

چكيده انگليسي :

Calculation and investigation of self diffusivity of Carbon disulfide Carbon dioxide Methane Nitrogen and Oxygen gases in Beta zeolite via molecular dynamics simulation Seyedeh Leila Fani Sadrabadi e mail leilafani@gmail com March 24 2010 Department of Chemistry Isfahan University of Technology Isfahan 84156 83111 Iran Degree M Sc Language Farsi Bijan Najafi najafi@cc iut ac ir Saman Alavi samanalavi@gmail com Abstract Beta zeolite represented the first high silica zeolite Si Al 10 100 synthesized and it has superior thermal and acid stability The structure of Beta zeolite consists of intersecting 6 5 5 6 and 7 5 5 7 channels this zeolite has been demonstrated to be useful in several hydrocarbon conversion processes however there are seldom reports on applications of Beta zeolite for gas adsorption now The most straightforward way is to compute a diffusion coefficient of an adsorbed molecule directly from a molecular dynamics simulation So in this thesis diffusion of Carbon disulfide Carbon dioxide Methane Nitrogen and Oxygen gases molecules in Beta zeolite with BEA code and Si64O128 chemical formula has been studied by molecular dynamics simulation These gases are very important in many industrial applications The aim of this study is to understand the effects of the temperature and kind of guest on the dynamic and diffusion of these guests in Beta zeolite Simulations were performed at loadings of 4 and 8 Carbon disulfide Carbon dioxide Methane Nitrogen and Oxygen molecules per unit cell at 250 K 298 K 350 400 K 500 K 600 K and 700 K The main purpose of this simulation is the study of properties such as the mean square displacement diffusion coefficient radial distribution function adsorption energy and activation energy In all the simulations via DL POLY2 software pressure and time step of each system were fixed at 1 bar and 0 001 ps respectively First the simulations for each loading were performed in canonical ensemble at seven different temperatures during 100 ps 100 000 steps to reach the equilibration of the systems Then each of the equilibrium systems was simulated in micro canonical ensemble during 500 ps 500 000 steps to get the dynamic properties as named above The slope of the curves of mean square displacement vs time increases with temperature and molecular weight of At the loadings The calculated diffusion coefficient at fixed loading increases with temperature and at a fixed temperature decreases as the loading and molecular weight of guests increases The calculated activation energies via Arrhenius equation decrease with increasing of loading and increase as molecular weight of gusts increases Good agreement between the simulated and experimental activation energies have obtained Radial distribution functions of different atomic sites were obtained at various temperatures and loadings and the highest peak shifts were observed in center of mass center of mass RDFs of guests Adsorption energies for each guest in Beta zeolite are calculated at kJ mol In both loadings the Adsorption energies decrease with temperature and increase with molecular weight of guest Key Words Beta zeolite Molecular dynamics Simulation Diffusion coefficient Carbon disulfide Carbon dioxide Methane Nitrogen Oxygen

فاني صدرآبادي، ليلا

بررسي نفوذ و جذب گازهاي كربن دي اكسيد ،كربن دي سولفيد، متان، اكسيژن و نيتروژن در زئوليت

ديناميك مولكولي , انرژي جذب , انرژي فعال سازي نيتروژن