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

Sulfanilic acid was immobilized onto rice husk ash via 3-(chloropropyl)triethoxy-silane to form an acidic solid catalyst denoted as RHAPhSO(3)H. The BET surface area was found to be 308 m(2) g(-1). Pyridine adsorption study revealed the presence of Bronsted acid sites. The EDX analysis showed the presence of S (10.88%) and N (10.37%). The Si-29 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 C-13 MAS NMR together with a series of chemical shifts consistent with the presence of the benzene ring. In the alkylation of phenol using RHAPhSO(3)H as the catalyst resulted in 95% conversion of tert-butyl alcohol at 120 degrees C with 52% selectivity towards 4-tert-butylphenol. The catalyst was reused several times without significant loss of catalytic activity. (C) 2011 Elsevier B.V. All rights reserved.