Solvent free liquid-phase alkylation of phenol over solid sulfanilic acid catalyst

A solid sulfanilic acid catalyst was found to be active in the solution state alkylation reaction. Alkylation of phenol yielded 57% conversion of phenol and shows 52% selectivity towards 4- tert-butylphenol. [Display omitted] ► The immobilization of silica with sulfanilic acid has been done via a simple technique. ► The catalyst was active in the solvent free alkylation of phenol. ► The solvent free alkylation of phenol with tert-butyl alcohol at 120 °C gave a 57% conversion with 52% selectivity towards 4- tert-butylphenol. ► The catalyst was regenerated easily and reused many times without loss of activity. Sulfanilic acid was immobilized onto rice husk ash via 3-(chloropropyl)triethoxy-silane to form an acidic solid catalyst denoted as RHAPhSO 3H. The BET surface area was found to be 308 m 2 g −1. Pyridine adsorption study revealed the presence of Brønsted acid sites. The EDX analysis showed the presence of S (10.88%) and N (10.37%). The 29Si MAS NMR showed the presence of T 2, T 3, Q 3 and Q 4 silicon centres. The three carbon atoms of the propyl group were evident from the 13C MAS NMR together with a series of chemical shifts consistent with the presence of the benzene ring. In the alkylation of phenol using RHAPhSO 3H as the catalyst resulted in 95% conversion of tert-butyl alcohol at 120 °C with 52% selectivity towards 4- tert-butylphenol. The catalyst was reused several times without significant loss of catalytic activity.