Nitrogen adsorption study of organised mesoporous alumina

As the arrangement of pores generally achieved in organised mesoporous alum ina is not completely regular, gas adsorption methods appear important for characterisation of this material. One of the promising approaches to adsor ption data analysis is based on the comparison of the adsorption isotherm o f nitrogen at -196 degreesC on the porous solid under study with the standa rd adsorption isotherm of the same adsorbate on a reference nonporous solid . To obtain reliable standard nitrogen adsorption data for characterisation of the alumina porous structure, nitrogen adsorption isotherms on Degussa Aluminiumoxid C and alpha -alumina were carefully measured at -196 degreesC with ASAP 2010 and modified Accusorb 2100E instruments. Standard nitrogen adsorption data (adsorbed amount divided by surface area) were listed for 4 1 points in the relative pressure range 0.001 to 0.95. Their applicability was tested on organised mesoporous aluminas of various structural parameter s using the comparison plot method. Although some samples of organised meso porous alumina were calcined at relatively high temperatures, only the stan dard data on Degussa Aluminiumoxid C proved suitable for the comparative an alysis of adsorption isotherms. The standard adsorption data on Degussa Alu miniumoxid C transformed to the statistical film thickness curve were used for calculation of Barrett-Joyner-Halenda (BJH) pore size distributions. Th e determined material parameters of the organised mesoporous aluminas were also supported by X-ray diffraction data and were consistent with the condi tions of synthesis and heat treatment of these materials.