Mechanical properties of monolithic compressed expanded graphite-based adsorbents related to the temperature of pyrolysis and activation, studied with ultrasound

Compressed expanded graphite (CEG) blocks produced from expanded graphite (EG) of apparent density of 2.6 kg m−3 and surface area of 20–40 m2/g, provided by Carbone-Lorraine Group (France), were applied to the preparation of microporous adsorbents. About 100 cubic CEG blocks were prepared, with a porosity in the range 87.7–99.3%. Thirty CEG blocks of the same porosity equal to 94.32% were impregnated with polyfurfuryl alcohol and varnish, pyrolyzed next at the temperatures of 400, 450, 500 or 550 °C, and finally activated at 900 and 950 °C. The effect of temperature of both the pyrolysis and activation, as well as the effect of the type of applied impregnating agent on the elastic properties of the resultant adsorbents, are discussed. found that the stiff impregnating agent can destroy the weak, sensitive network of the highly porous CEG if its concentration exceeds a certain threshold value, characteristic of a given CEG porosity. A high temperature of pyrolysis can increase the cross-linking degree of the polymer, resulting in a higher stiffness of the adsorbents. r difference of properties between samples impregnated with polyfurfuryl alcohol and varnish was found as a result of the different wettability of these impregnating agents and different ability to create additional cross-links.