Hydrogen storage properties of B- and N-doped microporous carbon

A B- and N-doped microporous carbon has been synthesized via a substitution reaction. The obtained carbon exhibited much higher surface area than the previously reported B- and N-doped carbon. The hydrogen storage measurements indicated that the B- and N-doped microporous carbon had a 53% higher storage capacity than the carbon materials with similar surface areas. Furthermore, hydrogen storage via spillover was studied on Ru-supported B- and N-doped microporous carbon and a storage capacity of 1.2 wt % at 298 K and 10 MPa was obtained, showing an enhancement factor of 2.2. Ab initio molecular orbital calculations were also performed for the binding energies between the spiltover hydrogen atom and various sites on the doped carbon. The theoretical calculations can explain the experimental results well, which also shed light on the most favorable and possible sites with which the spiltover hydrogen atoms bind. © 2009 American Institute of Chemical Engineers AIChE J, 2009Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/63091/1/11851_ftp.pd

Effect of fractional free volume and Tg on gas separation through membranes made with different glassy polymers

8 páginas, 10 figuras, 3 tablas.The aim of this work is to study how the characteristics of the polymer used to manufacture gas separation membranes influence its permeability and selectivity. It has been shown that the gas diffusivity decreases with the kinetic diameter of the gas except for CO2, probably due to its high condensability. While solubility increases with the gas condensation temperature and clearly with the glass transition temperature of the polymer for each gas. The permeabilities of CO2, CH4, O2, N2 increase for increasing glass transition temperatures. Nevertheless only the selectivity of CO2 versus the other gases increases significantly when polymers with high glass transition are used. The Robeson limit in a selectivity-versus-permeability plot is approached for CO2/CH4 when Tg increases. This distance to the Robeson limit, for this pair of gases, results to decrease for increasing Tg. For the case of the O2/N2 selectivity remains approximately constant with an appreciable increase in permeability for polymers with increasing Tg. Permeability increases due to the corresponding increase in fractional free volume, FFV, that appears for increasing glass transition temperatures, Tg. This correlation of FFV with Tg has been confirmed by obtaining FFV by different methods.Contract grant sponsor: CICYT Plan Nacional de I1D1I; contract grant numbers: MAT2005-04976, CTQ2006-01685, and MAT2004-01946.Peer reviewe