For an heterogenization, different kinds of catalytic filamentous carbons (CFC) were used as a support for some heteropoly acids (HPAs): H6P2W21O71 (H2O)(3) (P2W21), H(6)AS(2)W(12)O(69) (H2O) (As2W21), Dawson type alpha-H6P2W12O62 (P2W18) and Keggin type H3PW12O40 (PW). The support properties, which affect the interaction between HPAs and supports were studied. Concentration of Bronsted acidic sites in PW and PW/support was determined from the ESR studies of the stable nitroxyl radical (4-hydroxy-2,2',6,6'-tetramethylpyperidin-N-oxyl (TEMPOL)) adsorbed from hexane. The reaction of 2,6-di-tert-butyl-4-methylphenol (DMBP) with toluene as tert-butyl acceptors was studied using bulk and supported PW and P2W18. It was found that P2W18 was more active than PW. It was shown that catalytic activities of HPAs supported on SiO2 and CFC were approximately equal. The activity of the surface protons in HPA/support increased monotonically as the total HPA loading increased, reaching a maximum for the bulk HPA. (C) 2003 Elsevier B.V. All rights reserved.