Search results for "physisorption"
showing 10 items of 53 documents
Characterization and utilization of MFI zeolites and MCM-41 materials for gaseous pollutant adsorption
1999
Physisorption of n-hexane, trichloroethylene, tetrachloroethylene, carbon and nitrogen oxides on a microporous ZSM-5 (Si/Al=339) zeolite and an amorphous mesoporous MCM-41 (Si/Al=∞) sample was examined by isothermal thermogravimetry, manometry and calorimetry to evaluate the feasibility of using these porous materials for gaseous pollutant adsorption at room temperature. The adsorbents showed very interesting adsorption properties for hydrocarbons. ZSM-5 exhibited the strongest adsorption affinity and MCM-41 showed the largest adsorption capacity. Another main feature in this work was to observe a stepped-isotherm for the adsorption of C2Cl4 on ZSM-5. Such a substep located at very low rela…
Adsorption of hydrogen isotopes in the zeolite NaX: Experiments and simulations
2017
Abstract Among the different methods to separate hydrogen isotopes one is based on the physisorption at low temperature (below 100 K) where quantum effects induce a particular behavior. In the present work, we study the adsorption of single H 2 and D 2 on the zeolite NaX by combining experiments (manometry) from 30 to 150 K and molecular dynamics simulations at 40 and 77 K. Simulations also include the adsorption analysis for T 2 . Adsorption on NaX membranes is simulated and quantum corrections are introduced by using the well-known Feynman–Hibbs approach into the interaction potentials. Experimental adsorption isotherms are reproduced by using the Toth equation and it is shown that the ad…
Theoretical study of the interaction between carbon nanotubes and carboplatin anticancer molecules
2015
International audience; Full DFT calculations were carried out to study the interactions between single-wall functionalized carbon-based metallic nanotubes (CNTs) and carboplatin anticancer drugs. The geometry of the CNT-carboplatin was optimized considering different molecular configurations on inner and outer surfaces of the nanotubes. Simulation results show that the most stable physisorption state for molecules is to be located inside the nanotubes in a parallel configuration. Furthermore{,} we demonstrated that the molecular physisorption was reinforced as soon as the number of encapsulated carboplatin molecules increased{,} leading to a favored state where the nanovector is filled by …
Theoretical use of boron nitride nanotubes as a perfect container for anticancer molecules
2016
International audience; In recent years great interest has emerged in the development of nanocarriers for drug transport. One of themajor challenges is to obtain a drug delivery system able to control the drug release profile, transportabsorption and distribution, in the view of improving efficacy and safety. Herein, we present theoreticalresults based on density functional theory (DFT) to determine the best adsorption site for the anticancerifosfamide molecule in boron nitride nanotubes. For this functionalized system we determine thedependence of the adsorption energy on the displacement of molecules in the outer and inner boronnitride surfaces, together with their local morphological and…
Imidazolium functionalized carbon nanotubes for the synthesis of cyclic carbonates: reducing the gap between homogeneous and heterogeneous catalysis
2016
Single walled carbon nanotubes (SWCNTs) were functionalized with imidazolium salts bearing vinyl functionalities. An extremely high loading of active species was achieved through a straightforward one-pot procedure involving self-assembly of the imidazolium moieties followed by radical initiated polymerization of the double bonds. The materials were extensively characterized by transmission electron microscopy, Raman spectroscopy, nitrogen physisorption and combustion chemical analysis. The imidazolium functionalized SWCNTs displayed excellent catalytic activity for the reaction of CO2 and epoxides to produce cyclic carbonates as demonstrated by the excellent turnover numbers (TON). Moreove…
Interaction Mechanisms between guaiacols and lignin: the conjugated double bond makes the difference.
2011
Lignin is considered to be responsible for a selective sorption of phenolic compounds on wood. In order to investigate the mechanisms involved, two similar guaiacol compounds--only differing by the nature of the para side chain--were adsorbed on oak wood extracted lignin. Vapor sorption-desorption isotherms indicated that about 3.5 wt % of 4-vinylguaiacol is adsorbed near saturation whereas it is only 0.8% for 4-ethylguaiacol. For both compounds, the isotherms displayed a hysteresis though significantly greater for 4-vinylguaiacol. Analyses of the hydroxyl stretching region of FTIR spectra of the lignin/4-ethylguaiacol and lignin/4-vinylguaiacol complexes indicated that physisorption via hy…
A model for polybutadiene coatings on porous silica
1993
Non-wetting viscous liquids such as oligobutadiene prefer “active” sites such as pores during the process of physisorption. Thus, polybutadiene (PBD) coatings on porous silica do not result in a homogeneous polymer film but in an inhomogeneous loading where the bulk polymer is mainly sited in the pores of the silica. An increasing polymer loading leads to increasingly filled pores instead of a thicker polymer film. We cannot exclude the possibility that most of the surface is covered at least with a thin polymer film since the chromatographic behaviour is relatively good for polypeptides, which are highly susceptible to the silanol groups of silica.
Isostructural compartmentalized spin-crossover coordination polymers for gas confinement
2016
[EN] Here we present two FeII coordination polymers that possess discrete compartments suitable for CO2 physisorption despite the lack of permanent channels. The two crystalline materials, of general formula [Fe(btzbp)3](X)2 (X = ClO4 or BF4), present voids of ca. 250 Å3, which each can accommodate up to two CO2 molecules. The abrupt spin transition can be modified upon CO2 sorption, and different magnetic behaviour is observed depending on the number of molecules sorbed.
Multilayer build-up of a reactive polymer with α,ω-functionalized chromophores
1997
Alternating multilayers with up to ten layers have been prepared by sequential reaction of a reactive polymer (poly[(1-methylvinyl isocyanate)-alt-(maleic anhydride)]) with α,ω-functionalized chromophores. For this purpose new chromophores were synthesized varying the length of the hydrophobic spacer. The analysis of the multilayer build-up shows that physisorption is more important than chemisorption for fixation of new polymer layers. Thus, a multilayer build-up is only possible with the shorter, more hydrophilic chromophore and not with the long hydrophobic spacer.
Influence of the preparation method on the thiophene HDS activity of silica supported CoMo catalysts
2002
Abstract The effect of the preparation method of CoMo/SiO2 catalysts with and without sodium ions, on the hydrodesulfurization (HDS) of thiophene was investigated by X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS) and N2 physisorption (BET). The samples were prepared by total sol–gel route, by classic wetness impregnation and by co-impregnation, in the presence of nitrilotriacetic acid (NTA), of commercial and sol–gel prepared silica. The influence of sodium ions added to the sol mixture and to the silica before the impregnation with Co and Mo salt solution, was also considered. The presence of sodium favoured the phase transition of amorphous silica to cristobalite with con…