Nitrogen production using adsorption

Characterization of products. N2-adsorption-desorption isotherms were recorded at liquid nitrogen temperature after outgassing at 200-250 C for 2hr. Surface areas were calculated using the BET-equation and pore volumes were estimated to be the liquid volume adsorbed at a relative pressure of 0.995. Pore-size distributions were calculated from the desorption branches of the isotherms using parallel plates as a geometrical model. X-ray diffraction analyses were performed on samples oriented in order to amplify the 001-reflexions. 

Several methods of helium purification from nitrogen are used. The washing the concentrate with liquid hydrocarbons, particularly with propane, is based on abnormal helium solubility in liquid propane. There are also continued intensive studies and implementation works on helium purification using membranes [19,20]. The purification by washing does not, however give a product of a sufficient purity and efficiency of the diffusive separation on membranes is still too low. For these reasons, the basic process of helium denitrification is adsorption on solid adsorbents, mainly on active carbon. 

The parent siliceous materials of the SBA-15 and MLV types were synthesised after typical procedures [2], The carbon replicas were prepared via polymerisation, catalysed by ferric chloride, of pyrrole introduced into the mesopores of matrices [3]. The products were characterised by the nitrogen adsorption, TEM, and thermal analysis (DTG, DTA). The nitrogen content in carbons was determined using elemental analysis, XPS, and EDX, while the Si and Fe contents, with XPS. The replicas of SBA-15 and MLV-0.75 are denoted as CMK-3Nx and OCM-.Nx, respectively, were x refers to the number of g of FeCl3 per 1 g of silica used for preparations. 

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