Co-treatment of novolac- and resole-type phenolic resins with coal-tar pitch for porous carbons

Commercial novolac- and resole-type phenol-formaldehyde resins were blended with a coal-tar pitch at a 1:1 weight ratio under conditions permitting the synthesis of homogeneous carbon materials. The behaviour of the carbon precursors (single components and blends) on pyrolysis up to 1000 °C followed by reactivity towards CO2 was assessed using a thermogravimetric analyser. N2 adsorption at 77 K was used to compare the development of porosity in activated carbons produced by steam activation until 50 wt.% burn-off. The addition of a hardener (urothropine) modifies the thermal behaviour of the novolac resin. There is a shift in the maximum of the weight loss rate to a higher temperature and a distinct increase in the char yield. However, very similar microporous activated carbons with a BET surface area of about 1500 m2/g are produced from the uncured and cured resin. Blending with pitch reduces the SBET by 300-400 m2/g. In the resin-pitch blend the urothropine induces a cross-linking of pitch constituents leading to an enhanced yield of the resultant char. The activation of resole-derived char occurs at a high gasification rate, leading to a less developed porosity and a considerable contribution of mesopores. Such behaviour is related to the catalytic activity of inorganic impurities, mostly sodium, that are present in this resin.