Five intermediates for preparing long chain n-alkylphenol trimeric surfactants, 2,6-bis(5-alkylsalicyl)-4-alkylphenol, were synthesized from fatty acid, phenol, and paraformaldehyde through Friedel-Crafts acylation, esterification, Fries rearrangement, Huang Minlon reduction, alkaline catalytic reaction, and condensation reaction by virtue of solid superacid, and their molecular structures were confirmed by NMR, IR techniques and elemental analysis. According to this synthetic route of 2,6-bis(5-alkylsalicyl)-4-alkylphenol, 2,6-bis(5-nonylsalicyl)-4-nonylphenol has also been synthesized by using isononylphenol (industrial product) and paraformaldehyde successfully. It was showed that when 2,6-bis(hydroxymethyl)-4-alkylphenol and alkylphenol were reacted at a molar ratio of 1∶2 at 140 ℃ for 2 h, the product yield could reach 95%.

Key words: solid superacid, alkylphenol, paraformaldehyde, catalysis, synthesis