Synthesis of cc-tocopherol starting from trimethylhydroquinone (TMHQ) and isophytol (IP) was performed over Nafion/SiO2 nano-composite catalysts (Nafion content: 5-20 wt.%) and Nafion(R) NR50 resin. The nanocomposites were made by in situ hydrolys.s of tetraethoxysilane in the presence of home-made Nation solution. Nitrogen adsorption and catalytic dehydration of 2-propanol were used, respectively, to characterize the texture and acid properties of the nanocomposites. It is found that acid strength of the Nafion-based acidic sites was weakened in the nanocomposites and the weakening disappeared when the amount of Nation exceeded 30 wt.% of the nanocomposite. The pore structure and accessibility of the Nafion-based acidic sites in the nanocomposite catalysts showed pronounced effects on the catalytic efficiency toward the desired alpha-tocopherol. In comparison with Nation resin in the condensed phase (Nafion(R) NR50), 5 and 13 wt.% Nafion/SiO2 catalysts showed tenfold higher catalytic activities by turnover frequency for alpha-tocopherol formation owing to increased Nafion dispersion and accessibility of the Nafion-based acid sites. Though the acid sites in the 20 wt.% Nafion/SiO2 catalyst had similar accessibility to those in the 5 and F; wt.% Nafion/SiO2 catalysts by the dehydration of 2-propanol, smaller pore sizes of the 20 wt.% Nafion/SiO2 catalyst induced severe side reactions of the IP reactant, such as dehydration to form phytadienes and furan derivatives, which resulted in much lower yield (or selectivity) and turnover frequency for alpha-tocopherol. (C) 2004 Elsevier B.V. All rights reserved.