The surface area, pore volume (total and specific) and their size distributions in the range of micro- and mesopores for porous materials (catalysts, carriers, sorbents) can be measured using the Quadrasorb evo QDS-30 automatic analyzer (Quantachrome Instruments, USA). As a result of the measurement, a standard report is generated, including data for modelling the pore size distribution applicable to a diameter of 1 - 300 nm.
Option of measuring samples with minimum size of 10 microns. The shape of pellets is irrelevant.
The sample is degassed in vacuum at a temperature of 200 ° C for 120 minutes before the test. The temperature and time of heat treatment can be changed by agreement with the customer.
The porous structure of solid materials (catalysts, carriers, sorbents and other porous materials) is determined by the presence of pores of various diameters: macro (>50 nm), meso (2 - 50 nm) and micro (< 2 nm) and their volume.
The volume of mesopores is determined by nitrogen porosimetry. The volume of macropores is determined by mercury porosimetry.
The method of nitrogen porosimetry is based on quantity measurement of nitrogen condensating in the pores of a sample at a certain pressure. The steady-state pressure corresponds to a certain pore radius. By applying mathematical processing of adsorption isotherms via use various theories and models, the specific surface area values are calculated (using the BET-Brunaer-Emmett-Teller or Langmuir method); specific pore volume, pore size distribution, as well as the predominant mesopore diameters from the adsorption and desorption branches of the isotherm, diameter. The method refers to non-destructive testing.
Through specific surface measurements, it is possible to evaluate catalysts, adsorbents and other porous materials both during production quality control stage and in the product development stage. The specific surface area of the material is what significantly affects the overall performance of the catalyst and sorbent, i.e it provides the contact area of the catalyst / sorbent with the reaction medium. Additionally, this method helps to determine the degradation factor of the catalyst or sorbent during operation. A decrease in the specific surface area of the material used is among the most common causes of performance degradation of the process units.