Selective oxidation of glycerol with molecular oxygen was studied over different functionalized MWNTs supported Pt catalysts in base-free aqueous solution. N-2 adsorption, IR, Raman and SEM-EDS analysis confirmed that the tubular structure of MWNTs is stable during HNO3 and H2O2 pretreatment and the surface of MWNTs was successfully functionalized by HNO3, H2O2 and NH2-CH2-CH2-SH. XRD, SEM and TEM analysis demonstrated that unique sized Pt particles formed on S-pretreated MWNTs. Pt/S-MWNTs catalyst with small Pt particles was more active than Pt/MWNTs, Pt/HNO3-MWNTs and Pt/H2O2-MWNTs for glycerol oxidation in base-free aqueous solution. Free glyceric acid formed (with 68.3% selectivity and 90.4% conversion of glycerol) on Pt/S-MWNTs in base-free solution. While dihydroxyacetone formed firstly in an aqueous solution of NaOH/glycerol = 2:1 and the cleavage C-C bonds (catalyzed by alkali) arise severely. (C) 2011 Elsevier B.V. All rights reserved.